Observation optical system, optical device, and method for manufacturing observation optical system

Abstract

Provided is a small-sized, lightweight, wide-view, and high-magnification observation optical system having a large numerical aperture and capable of satisfactorily correcting various aberrations. The present invention comprises, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being formed between the objective optical system and the relay optical system, and a second intermediate image I2 being formed between the relay optical system and the eyepiece optical system.

Description

Observation optical system, optical instrument, and method for manufacturing observation optical system

[0001] The present invention relates to an observation optical system, an optical instrument, and a method for manufacturing an optical system.

[0002] Conventionally, among observation optical systems whose main purpose is to observe an object, there are known those that use an erecting prism as an erecting optical system, as in Patent Document 1. In recent years, there has been a demand for such observation optical systems that can correct various aberrations more effectively, and that are small, lightweight, have a wide field of view, have a high magnification, and have a large aperture.

[0003] Japanese Patent Application Laid-Open No. 2008-40065

[0004] An observation optical system according to a first aspect has, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system that forms a first intermediate image between the objective optical system and the relay optical system, and a second intermediate image between the relay optical system and the eyepiece optical system, and that satisfies the following condition: 0.060<fe / TL<0.130, where fe is the focal length of the eyepiece optical system, and TL is the total optical length of the observation optical system.

[0005] An observation optical system according to a second aspect includes, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, wherein the erecting optical system is a relay optical system, and wherein a first intermediate image is formed between the objective optical system and the relay optical system, and a second intermediate image is formed between the relay optical system and the eyepiece optical system; and further includes a second observation optical system that is composed of the same lens components as the first observation optical system, and wherein the first observation optical system and the second observation optical system are arranged in parallel.

[0006] An observation optical system according to a third aspect has, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system that forms a first intermediate image between the objective optical system and the relay optical system, and a second intermediate image between the relay optical system and the eyepiece optical system, and that satisfies the following condition: 0.040<Dm / TL<0.350, where Dm is the maximum air space between lens surfaces in the observation optical system, and TL is the total optical length of the observation optical system.

[0007] An observation optical system according to a fourth aspect has, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system that forms a first intermediate image between the objective optical system and the relay optical system, and a second intermediate image between the relay optical system and the eyepiece optical system, and at least one lens S among the lenses arranged in the objective optical system satisfies the following condition: 80.00<νds, where νds is the Abbe number of the lens S with respect to the d-line.

[0008] An optical apparatus according to a fifth aspect includes the above observation optical system.

[0009] A sixth aspect of the present invention provides a method for manufacturing an observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system that forms a first intermediate image between the objective optical system and the relay optical system, and a second intermediate image between the relay optical system and the eyepiece optical system, and that satisfies the following condition: 0.060<fe / TL<0.130, where fe is the focal length of the eyepiece optical system, and TL is the total optical length of the observation optical system.

[0010] In addition, a manufacturing method for an observation optical system according to a seventh aspect includes a first observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, wherein the erecting optical system is a relay optical system, and a first intermediate image is formed between the objective optical system and the relay optical system, and a second intermediate image is formed between the relay optical system and the eyepiece optical system; and further includes a second observation optical system constructed from the same lens components as the first observation optical system, and the first observation optical system and the second observation optical system are arranged in parallel.

[0011] Furthermore, a manufacturing method for an observation optical system according to an eighth aspect includes, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system that forms a first intermediate image between the objective optical system and the relay optical system, and a second intermediate image between the relay optical system and the eyepiece optical system, and is configured to satisfy the following conditional expression: 0.040<Dm / TL<0.350, where Dm is the maximum air space between lens surfaces in the observation optical system, and TL is the total optical length of the observation optical system.

[0012] A manufacturing method of an observation optical system according to a ninth aspect includes, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system that forms a first intermediate image between the objective optical system and the relay optical system, and a second intermediate image between the relay optical system and the eyepiece optical system, and at least one lens S of the lenses arranged in the objective optical system is configured to satisfy the following conditional expression: 80.00<νds, where νds is the Abbe number of the lens S for the d-line.

[0013] An observation optical system according to a tenth aspect has, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being between the objective optical system and the relay optical system, and a second intermediate image being between the relay optical system and the eyepiece optical system, the relay optical system being composed of, in order from the object side, a front group and a rear group, with an air gap between the front group and the rear group, the front group and the rear group each having a positive lens, the positive lens AL of the front group positive lenses arranged closest to the observation side has an Abbe number vdAL for the d-line greater than 40.00, and the positive lens B1 of the rear group positive lenses arranged closest to the object side has an Abbe number vdB1 for the d-line smaller than 40.00, and when there are multiple combinations of the front group positive lens AL and the rear group positive lens B1, the combination having the largest difference in Abbe number for the d-line between the front group positive lens AL and the rear group positive lens B1 is used, When a negative single lens is provided between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group, and at least one positive lens A among the front group positive lenses satisfies the following conditional expressions: 1.400<ndA<1.650 60.00<νdA, where ndA: refractive index of the front group positive lens A for the d line νdA: Abbe number of the front group positive lens A for the d line

[0014] An optical apparatus according to an eleventh aspect includes the above observation optical system.

[0015] a first intermediate image between the objective optical system and the relay optical system and a second intermediate image between the relay optical system and the eyepiece optical system; the relay optical system is composed of a front group and a rear group in that order from the object side, with an air gap between the front group and the rear group; the front group and the rear group each having a positive lens; the positive lens AL of the front group positive lenses arranged closest to the observation side has an Abbe number vdAL for the d-line greater than 40.00; the positive lens B1 of the rear group positive lenses arranged closest to the object side has an Abbe number vdB1 for the d-line smaller than 40.00; and when there are multiple combinations of the front group positive lens AL and the rear group positive lens B1, the combination having the largest difference in Abbe number for the d-line between the front group positive lens AL and the rear group positive lens B1 is used; When a negative single lens is present between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group, and at least one positive lens A among the front group positive lenses is configured to satisfy the following conditional expressions: 1.400<ndA<1.650 60.00<νdA where, ndA: refractive index of the front group positive lens A for the d line νdA: Abbe number of the front group positive lens A for the d line

[0016] 10 is a cross-sectional view of an observation optical system according to Example 1. FIG. 11 is a diagram illustrating various aberrations of the observation optical system according to Example 1. FIG. 12 is a cross-sectional view of an observation optical system according to Example 2. FIG. 13 is a diagram illustrating various aberrations of the observation optical system according to Example 3. FIG. 14 is a cross-sectional view of an observation optical system according to Example 4. FIG. 15 is a diagram illustrating various aberrations of the observation optical system according to Example 4. FIG. 16 is a cross-sectional view of an observation optical system according to Example 5. FIG. 17 is a diagram illustrating various aberrations of the observation optical system according to Example 5. FIG. 18 is a cross-sectional view of an observation optical system according to Example 6. FIG. 19 is a diagram illustrating various aberrations of the observation optical system according to Example 6. FIG. 19 is a cross-sectional view of an observation optical system according to Example 7. FIG. 19 is a diagram illustrating various aberrations of the observation optical system according to Example 7. FIG. 19 is a cross-sectional view of an observation optical system according to Example 8. FIG. 19 is a diagram illustrating various aberrations of the observation optical system according to Example 8. FIG. 19 is a cross-sectional view of an observation optical system according to Example 9. FIG. 19 is a cross-sectional view of an observation optical system according to Example 10. FIG. 19 is a diagram illustrating various aberrations of the observation optical system according to Example 10. FIG. 19 is a cross-sectional view of an observation optical system according to a second embodiment, which uses a pair of observation optical systems. FIG. 19 is a schematic cross-sectional view of binoculars, which are an optical instrument using a pair of observation optical systems. 10. A flow diagram showing an outline of a method for manufacturing the optical devices of the first and third embodiments. A flow diagram showing an outline of a method for manufacturing the optical device of the second embodiment. A flow diagram showing an outline of a method for manufacturing the optical device of the fourth embodiment. A sectional view of the observation optical system of the 11th example. A sectional view of the observation optical system of the 12th example. A sectional view of the observation optical system of the 12th example. A sectional view of the observation optical system of the 13th example. A sectional view of the observation optical system of the 13th example. A sectional view of the observation optical system of the 14th example. A sectional view of the observation optical system of the 14th example. A sectional view of the observation optical system of the 15th example. A sectional view of the observation optical system of the 15th example. A sectional view of the observation optical system of the 16th example. A sectional view of the observation optical system of the 16th example. A schematic sectional view of binoculars, which is an optical device using a pair of observation optical systems. A flow diagram showing an outline of a method for manufacturing the optical device of the tenth embodiment.

[0017] Below, we will explain observation optical systems, optical devices, and methods for manufacturing optical systems according to the basic embodiment and first to twelfth embodiments of the present application. However, the present invention is not limited to the following embodiments, and any combination may be used. Furthermore, to avoid complication of explanation due to an increase in the number of reference symbols, the reference symbols for the figures according to each embodiment may be used independently in each drawing. Therefore, even if reference symbols common to other drawings are used, they do not necessarily have the same configuration as those in the other drawings.

[0018] First, the observation optical system according to this basic embodiment will be described. The observation optical system OS according to this basic embodiment has, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E. The erecting optical system is a relay optical system R, which forms a first intermediate image I1 between the objective optical system O and the relay optical system R, and a second intermediate image I2 between the relay optical system R and the eyepiece optical system E.

[0019] The objective optical system O has positive refractive power and, for example, collects light from a distant object to form a first intermediate image I1, which is an inverted image. The relay optical system R has positive refractive power and re-images the first intermediate image I1, which is an inverted image formed by the objective optical system O, to form a second intermediate image I2, which is an erect image. The eyepiece optical system E has positive refractive power and magnifies the second intermediate image I2, which is an erect image formed by the relay optical system R. By configuring the observation optical system OS in this manner, an observer (not shown) can observe the object to be observed at eyepoint EP. Note that the observation optical system OS can change the spacing between some of the lenses to adjust diopter. By forming the erecting optical system using the relay optical system R, the first intermediate image I1 formed by the objective optical system O can be appropriately reduced, magnified to the same magnification, enlarged, or variable, compared to an erecting prism, and various aberrations generated in the objective optical system O and the eyepiece optical system E can be effectively corrected. In addition, image blur can be corrected by shifting or rotating some lenses relative to the optical axis. Furthermore, the diameter of the erecting optical system can be made smaller than with an erecting prism. This allows the observation optical system OS to achieve high magnification while maintaining a wide true field of view and to be made compact and lightweight. This observation optical system OS may also have a focusing screen, which serves as a collimation system, located on the image plane of at least one (or both) of the first intermediate image I1 and the second intermediate image I2. The focusing screen is typically a crosshair and field ring chrome-deposited on a glass plate. However, a display component such as an LCD panel may be used to realize a variable display, or various pieces of information may be displayed as appropriate. With this configuration, the observation optical system OS of this basic embodiment can effectively correct various aberrations, particularly spherical aberration, astigmatism, field curvature, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., and achieve high magnification while maintaining a wide true field of view and make the observation optical system compact and lightweight.

[0020] With this configuration, the observation optical system of the first embodiment further satisfies the following conditional expression (1): 0.060<fe / TL<0.130 (1) where fe is the focal length of the eyepiece optical system, and TL is the total optical length of the observation optical system.

[0021] Conditional formula (1) defines the ratio between the focal length of the eyepiece optical system and the overall optical length of the viewing optical system. By satisfying conditional formula (1), various aberrations, such as spherical aberration, coma, astigmatism, field curvature, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, and high magnification can be achieved while maintaining a wide actual field of view. In particular, spherical aberration and coma can be corrected well while maintaining a compact and lightweight lens.

[0022] It should be noted that by setting the lower limit of conditional expression (1) to 0.062, the effect of the first embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the first embodiment, it is more preferable to set the lower limit of conditional expression (1) to 0.064, 0.066, 0.067, or even 0.068. On the other hand, by setting the upper limit of conditional expression (1) to 0.125, the effect of the first embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the first embodiment, it is more preferable to set the upper limit of conditional expression (1) to 0.120, 0.115, 0.110, 0.105, 0.100, or even 0.097.

[0023] The observation optical system OS of the second embodiment is the same as that of the basic embodiment, i.e., a first observation optical system OS1 having, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, which forms a first intermediate image I1 between the objective optical system O and the relay optical system R, and a second intermediate image I2 between the relay optical system R and the eyepiece optical system E. With this configuration, the observation optical system OS further has a second observation optical system OS2 which is composed of the same lens components as the first observation optical system OS1, and the first observation optical system OS1 and the second observation optical system OS2 are arranged in parallel.

[0024] With this configuration, the observation optical system OS of the second embodiment has the same effects as the configuration of the observation optical system OS of the basic embodiment. Furthermore, the first observation optical system OS1 and the second observation optical system OS2 are configured using the same lens components, allowing binocular observation with the same optical performance. For the first observation optical system OS1 and the second observation optical system OS2, some lens spacing can be changed differently relative to the other for diopter adjustment. Note that the same lens components refer to lenses with the same surface radius of curvature, thickness, and material, but may differ in anti-reflection coating, outer shape, and so on. Furthermore, at least one of the first observation optical system OS1 and the second observation optical system OS2 may use optical components (such as the focusing screen, display component, optical filter, or prism), or different optical components may be used.

[0025] The observation optical system OS of the third embodiment is the same as that of the basic embodiment, i.e., it has, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, which forms a first intermediate image I1 between the objective optical system O and the relay optical system R, and forms a second intermediate image I2 between the relay optical system R and the eyepiece optical system E. With this configuration, the observation optical system OS of the third embodiment has the same effects as the configuration of the observation optical system OS of the basic embodiment, and with this configuration, it further satisfies the following condition: 0.040<Dm / TL<0.350 (2) where, Dm: maximum air spacing between lens surfaces in the observation optical system TL: total optical length of the observation optical system

[0026] Conditional expression (2) defines the ratio between the maximum air gap between lens surfaces in the viewing optical system and the total optical length of the viewing optical system. By satisfying conditional expression (2), various aberrations, such as spherical aberration, coma, astigmatism, field curvature, and chromatic aberration (i.e., axial chromatic aberration and lateral chromatic aberration), can be effectively corrected, a high magnification can be achieved while maintaining a wide field of view, and a compact and lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact and lightweight lens. Note that Dm is the air gap equivalent length when an optical component with no refractive power, such as a prism, is present between the lens surfaces.

[0027] Note that by setting the lower limit of conditional expression (2) to 0.045, the effect of the third embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the third embodiment, it is more preferable to set the lower limit of conditional expression (2) to 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, or even 0.078. On the other hand, by setting the upper limit of conditional expression (2) to 0.330, the effect of the third embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the third embodiment, it is more preferable to set the upper limit of conditional expression (2) to 0.300, 0.280, 0.250, 0.230, 0.200, 0.180, 0.150, 0.130, or even 0.100.

[0028] The observation optical system OS of the fourth embodiment is the same as that of the basic embodiment, i.e., has, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, which forms a first intermediate image I1 between the objective optical system O and the relay optical system R, and forms a second intermediate image I2 between the relay optical system R and the eyepiece optical system E. With this configuration, the observation optical system OS of the fourth embodiment has the same effects as the configuration of the observation optical system OS of the basic embodiment, and further, with this configuration, at least one lens S of the lenses arranged in the objective optical system satisfies the following conditional expression: 80.00<νds (3) where νds: Abbe number for the d-line of the lens S

[0029] Here, the Abbe number v for the d-line is expressed by the following equation, where nC is the refractive index for the C-line (wavelength 656.3 nm), nd is the refractive index for the d-line (wavelength 587.6 nm), and nF is the refractive index for the F-line (wavelength 486.1 nm): v = (nd - 1) / (nF - nC) The same equation for the Abbe number for the d-line applies to the subsequent conditional expressions, so explanation will be omitted.

[0030] Conditional expression (3) defines the Abbe number for the d-line of the lens S. By satisfying conditional expression (3), various aberrations, such as chromatic aberrations, i.e., axial chromatic aberration, lateral chromatic aberration, spherical aberration, astigmatism, and curvature of field, can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved. In particular, axial chromatic aberration and lateral chromatic aberration can be corrected well.

[0031] It should be noted that by setting the lower limit of conditional expression (3) to 81.00, the effect of the fourth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the fourth embodiment, it is more preferable to set the lower limit of conditional expression (3) to 82.00, 84.00, 86.00, 88.00, 90.00, 92.00, or even 93.00. It should be noted that by setting the upper limit of conditional expression (3) to "<100.00," the effect of the fourth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the fourth embodiment, it is more preferable to set the upper limit of conditional expression (3) to 98.00, 96.00, 94.00, 92.00, 90.00, 88.00, 86.00, or even 84.00.

[0032] Here, it is preferable to satisfy conditional expressions (1) to (3) in a redundant manner, since this allows for a composite effect to be obtained. 1 Furthermore, in the observation optical systems according to the first to fourth embodiments, it is desirable that at least one lens S among the lenses arranged in the objective optical system satisfies the following conditional expression: 1.4300<nds<1.5200 (4) where, nds: refractive index of the lens S with respect to the d line.

[0033] Conditional expression (4) defines the refractive index of the lens S with respect to the d-line. By satisfying conditional expression (4), various aberrations, such as spherical aberration, coma, and chromatic aberration, i.e., axial chromatic aberration and lateral chromatic aberration, can be corrected well, and a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can also be achieved. In particular, spherical aberration, coma, axial chromatic aberration, and lateral chromatic aberration can be corrected well.

[0034] Note that by setting the lower limit of conditional expression (4) to 1.4320, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (4) to 1.4370, 1.4400, 1.4500, 1.4600, 1.4700, or even 1.4800. On the other hand, by setting the upper limit of conditional expression (4) to 1.5100, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (4) to 1.5000, 1.4900, 1.4800, 1.4700, or even 1.4600.

[0035] Furthermore, in the observation optical systems according to the first to fourth embodiments, it is desirable that at least one lens S among the lenses arranged in the objective optical system is the positive lens closest to the object among the positive lenses included in the objective optical system.

[0036] This configuration makes it possible to effectively correct various aberrations, such as spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), achieve high magnification while maintaining a wide field of view, and achieve a compact and lightweight design. In particular, spherical aberration, coma, axial chromatic aberration, and lateral chromatic aberration can be effectively corrected.

[0037] In addition, in the observation optical systems according to the first to fourth embodiments, it is desirable that the lens closest to the object side of the observation optical system is a negative lens.

[0038] With this type of configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, the lens is durable, achieves high magnification while maintaining a wide actual field of view, and is also compact and lightweight.

[0039] Furthermore, it is desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 4.00<(-fcom) / fe<30.00 (5) where fcom is the combined focal length of the objective optical system and the relay optical system, and fe is the focal length of the eyepiece optical system.

[0040] Condition (5) defines the ratio of the combined focal length of the objective optical system and the relay optical system to the focal length of the eyepiece optical system, and indicates the magnification of the observation optical system.

[0041] By satisfying conditional expression (5), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration, i.e., axial chromatic aberration, lateral chromatic aberration, and the like, can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact, lightweight lens can also be achieved.

[0042] Note that by setting the lower limit of conditional formula (5) to 4.50, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional formula (5) to 5.00, 5.50, 6.00, 6.50, 7.00, 7.50, 8.00, 8.50, 9.00, or even 9.50. On the other hand, by setting the upper limit of conditional formula (5) to 25.00, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional formula (5) to 20.00, 18.00, 16.00, 14.00, 12.00, 11.00, 10.60, or even 10.30.

[0043] Furthermore, it is desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 4.00<tan θ′ / tan θ<30.00 (6), where 2θ is the actual field of view of the observation optical system, in degrees; 2θ′ is the apparent field of view of the observation optical system, in degrees.

[0044] Conditional expression (6) defines the ratio between the actual field of view of the observation optical system and the apparent field of view of the observation optical system, and indicates the magnification of the observation optical system.

[0045] By satisfying conditional expression (6), various aberrations, such as coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration), and chromatic aberration of magnification, can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact, lightweight lens can be achieved. In particular, coma can be effectively corrected while maintaining a high magnification with a compact, lightweight lens.

[0046] Note that by setting the lower limit of conditional expression (6) to 4.50, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first embodiment, it is more preferable to set the lower limit of conditional expression (6) to 5.00, 5.50, 6.00, 6.50, 7.00, 7.50, 8.00, 8.50, 9.00, or even 9.50. On the other hand, by setting the upper limit of conditional expression (6) to 25.00, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (6) to 20.00, 18.00, 16.00, 14.00, 12.00, 11.00, 10.60, or even 10.30.

[0047] Furthermore, it is desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 1.00<(-fcom) / fo<3.50 (7) where fcom is the combined focal length of the objective optical system and the relay optical system, and fo is the focal length of the objective optical system.

[0048] Conditional expression (7) defines the ratio between the combined focal length of the objective optical system and the relay optical system and the focal length of the objective optical system, and indicates the magnification of the relay optical system.

[0049] By satisfying conditional expression (7), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact, lightweight lens can be achieved. In particular, spherical aberration and coma can be corrected well at high magnification while maintaining a compact, lightweight lens.

[0050] Note that by setting the lower limit of conditional expression (7) to 1.10, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (7) to 1.20, 1.30, 1.40, 1.50, 1.55, 1.60, 1.65, 1.70, or even 1.75. On the other hand, by setting the upper limit of conditional expression (7) to 3.40, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (7) to 3.30, 3.20, 3.10, 3.00, 2.90, or even 2.80.

[0051] It is also desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 0.030<ER / TL<0.120 (8) where ER is the eye relief of the observation optical system, and TL is the total optical length of the observation optical system.

[0052] Conditional expression (8) defines the ratio between the eye relief of the observation optical system and the total optical length of the observation optical system. By satisfying conditional expression (8), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), can be corrected well, an appropriate eye relief can be obtained, high magnification can be achieved while maintaining a wide actual field of view, and compactness and weight reduction can be achieved.

[0053] Note that by setting the lower limit of conditional expression (8) to 0.040, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (8) to 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, or even 0.072. On the other hand, by setting the upper limit of conditional expression (8) to 0.110, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (8) to 0.105, 0.100, 0.095, 0.090, or even 0.085.

[0054] Furthermore, it is desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 3.00<fo / fe<8.00 (9) where fo is the focal length of the objective optical system, and fe is the focal length of the eyepiece optical system.

[0055] Conditional expression (9) defines the ratio between the focal length of the objective optical system and the focal length of the eyepiece optical system. By satisfying conditional expression (9), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compactness and weight reduction can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining compactness and weight reduction.

[0056] It should be noted that by setting the lower limit of conditional expression (9) to 3.10, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first embodiment, it is more preferable to set the lower limit of conditional expression (9) to 3.20, 3.30, 3.40, 3.50, 3.60, or even 3.70. On the other hand, by setting the upper limit of conditional expression (9) to 7.50, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (9) to 7.00, 6.80, 6.50, 6.30, 6.00, 5.80, 5.60, 5.40, or even 5.20.

[0057] Furthermore, it is desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 0.030<fr / TL<0.160 (10) where fr is the focal length of the relay optical system, and TL is the total optical length of the observation optical system.

[0058] Conditional expression (10) defines the ratio between the focal length of the relay optical system and the total optical length of the viewing optical system. By satisfying conditional expression (10), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact, lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact, lightweight lens.

[0059] Note that by setting the lower limit of conditional expression (10) to 0.032, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (10) to 0.034, 0.036, 0.038, 0.040, 0.046, or even 0.060. On the other hand, by setting the upper limit of conditional expression (10) to 0.150, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (10) to 0.140, 0.130, 0.120, 0.110, 0.100, 0.090, 0.080, or even 0.060.

[0060] Furthermore, it is desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 0.40<(-fcom) / TL<1.20 (11) where fcom is the combined focal length of the objective optical system and the relay optical system, and TL is the total optical length of the observation optical system.

[0061] Conditional expression (11) defines the ratio between the combined focal length of the objective optical system and the relay optical system and the total optical length of the viewing optical system. By satisfying conditional expression (11), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact and lightweight lens.

[0062] Note that by setting the lower limit of conditional expression (11) to 0.45, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (11) to 0.50, 0.55, 0.60, 0.65, or even 0.70. On the other hand, by setting the upper limit of conditional expression (11) to 1.15, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (11) to 1.13, 1.10, 1.08, 1.05, 1.03, 1.00, 0.97, or even 0.90.

[0063] It is also desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 2.50<fo / fr<10.00 (12) where fo is the focal length of the objective optical system, and fr is the focal length of the relay optical system.

[0064] Conditional expression (12) defines the ratio between the focal length of the objective optical system and the focal length of the relay optical system. By satisfying conditional expression (12), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved. In particular, spherical aberration and coma can be corrected well at high magnification while maintaining a compact and lightweight lens.

[0065] It should be noted that by setting the lower limit of conditional expression (12) to 2.60, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (12) to 2.80, 3.00, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, or even 7.00. On the other hand, by setting the upper limit of conditional expression (12) to 9.80, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (12) to 9.60, 9.40, 9.20, 9.00, 8.80, 8.30, or even 8.00.

[0066] Furthermore, it is desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 0.40<fr / fe<2.50 (13) where fr is the focal length of the relay optical system, and fe is the focal length of the eyepiece optical system.

[0067] Conditional expression (13) defines the ratio between the focal length of the relay optical system and the focal length of the eyepiece optical system. By satisfying conditional expression (13), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact and lightweight lens.

[0068] Note that by setting the lower limit of conditional expression (13) to 0.42, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (13) to 0.44, 0.46, 0.48, 0.50, or even 0.58. On the other hand, by setting the upper limit of conditional expression (13) to 2.30, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (13) to 2.10, 1.80, 1.60, 1.40, 1.20, 1.10, 0.90, or even 0.80.

[0069] Furthermore, the observation optical systems according to the first to fourth embodiments preferably satisfy the following condition: 0.70<D1 / TL<1.20 (14) where D1 is the distance from the object-side surface of the second lens component located closest to the object in the objective optical system to the observation-side surface of the eyepiece optical system, and TL is the total optical length of the observation optical system.

[0070] Conditional expression (14) defines the ratio of the distance from the object-side surface of the second-most lens component from the object side in the objective optical system to the observation-side surface of the eyepiece optical system to the total optical length of the observation optical system. By satisfying conditional expression (14), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact, lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact, lightweight lens.

[0071] Note that by setting the lower limit of conditional expression (14) to 0.72, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (14) to 0.75, 0.77, 0.80, 0.82, 0.85, 0.87, 0.90, or even 0.91. On the other hand, by setting the upper limit of conditional expression (14) to 1.18, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (14) to 1.15, 1.13, 1.10, 1.08, 1.05, 1.03, 1.00, or even 0.96.

[0072] Furthermore, it is desirable that the observation optical systems according to the first to fourth embodiments satisfy the following condition: 0.030<D2 / TL<0.200 (15), where D2 is the distance from the side closest to the observation side of the relay optical system to the side closest to the object side of the eyepiece optical system, and TL is the total optical length of the observation optical system. Condition (15) defines the ratio between the distance from the side closest to the observation side of the relay optical system to the side closest to the object side of the eyepiece optical system and the total optical length of the observation optical system. By satisfying condition (15), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, chromatic aberration of magnification), etc., can be effectively corrected, achieving high magnification while maintaining a wide actual field of view and enabling a compact and lightweight system. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact and lightweight system. It should be noted that D2 is the air distance converted into air length when an optical component with no refractive power, such as a prism, is present between the lens surfaces.

[0073] Note that by setting the lower limit of conditional expression (15) to 0.032, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (15) to 0.034, 0.036, 0.038, 0.040, 0.042, 0.044, or even 0.045. On the other hand, by setting the upper limit of conditional expression (15) to 0.180, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (15) to 0.160, 0.140, 0.120, 0.110, 0.100, 0.095, or even 0.090.

[0074] Furthermore, it is desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 0.90<(-fe1) / fe<10.00 (16) where fe1 is the focal length of the negative lens in the eyepiece optical system that is closest to the object, and fe is the focal length of the eyepiece optical system.

[0075] Conditional expression (16) defines the ratio between the focal length of the negative lens closest to the object in the eyepiece optical system and the focal length of the eyepiece optical system. By satisfying conditional expression (16), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), can be corrected well, a suitable eye relief can be provided, high magnification can be achieved while maintaining a wide actual field of view, and compactness and weight reduction can be achieved.

[0076] Note that by setting the lower limit of conditional expression (16) to 0.95, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (16) to 0.98, 1.20, 1.40, 1.60, 1.80, 2.00, 2.20, 2.50, 2.70, 3.00, 3.50, or even 4.00. On the other hand, by setting the upper limit of conditional expression (16) to 9.00, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (16) to 8.00, 7.00, 6.50, 6.00, 5.70, or even 5.00.

[0077] Furthermore, it is desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 2.00<rL / fe<200.00 (17) where rL is the radius of curvature of the lens surface of the eyepiece optical system that is closest to the viewing side, and fe is the focal length of the eyepiece optical system.

[0078] Conditional expression (17) defines the ratio between the radius of curvature of the lens surface closest to the observation side in the eyepiece optical system and the focal length of the eyepiece optical system. By satisfying conditional expression (17), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compactness and weight reduction can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining compactness and weight reduction.

[0079] Note that by setting the lower limit of conditional expression (17) to 2.20, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (17) to 2.50, 2.70, 3.00, 3.20, 3.50, 3.70, 4.00, or even 4.50. On the other hand, by setting the upper limit of conditional expression (17) to 180.00, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit value of conditional expression (17) to 160.00, 120.00, 70.00, 50.00, 30.00, 20.00, 18.00, 16.00, 15.00, 12.00, 10.00, 8.00, 7.00, 5.50, and even more preferably 5.00.

[0080] It is also desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 0.55<Φe / Φ<1.50 (18) where Φe: maximum effective diameter of the eyepiece optical system Φ: diameter of the objective optical system

[0081] Conditional expression (18) defines the ratio between the maximum effective diameter of the eyepiece optical system and the aperture of the objective optical system. By satisfying conditional expression (18), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact and lightweight lens.

[0082] Note that by setting the lower limit of conditional expression (18) to 0.57, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the lower limit of conditional expression (18) to 0.59, 0.62, 0.65, 0.67, 0.70, 0.72, 0.75, 0.80, 0.82, or even 0.85. On the other hand, by setting the upper limit of conditional expression (18) to 1.40, the effects of the first to fourth embodiments can be more reliably achieved. Furthermore, in order to further ensure the effects of the first to fourth embodiments, it is more preferable to set the upper limit of conditional expression (18) to 1.30, 1.20, 1.15, 1.05, or even 0.95.

[0083] In the observation optical systems according to the first to fourth embodiments, it is desirable that the relay optical system has a cemented lens and that the following conditional expression be satisfied: 1≦Nrc≦7 (19) where Nrc is the number of cemented lenses in the relay optical system.

[0084] Conditional expression (19) defines the number of cemented lenses in the relay optical system. By satisfying conditional expression (19), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved. In particular, spherical aberration and coma can be corrected well at high magnification while maintaining a compact and lightweight lens.

[0085] It should be noted that by setting the lower limit of conditional expression (19) to 2, the effects of the first to fourth embodiments can be made more certain. Furthermore, in order to make the effects of the first to fourth embodiments more certain, it is more preferable to set the lower limit of conditional expression (19) to 3, 4, or even 5. On the other hand, by setting the upper limit of conditional expression (19) to 6, the effects of the first to fourth embodiments can be made more certain. Furthermore, in order to make the effects of the first to fourth embodiments more certain, it is more preferable to set the upper limit of conditional expression (19) to 5, 4, 3, or even 2.

[0086] It is also desirable that the viewing optical systems according to the first to fourth embodiments satisfy the following condition: 4≦Ne≦8 (20) where Ne is the number of lenses in the eyepiece optical system.

[0087] Conditional expression (20) defines the number of lenses in the eyepiece optical system. By satisfying conditional expression (20), various aberrations, such as spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact, lightweight lens can be achieved. In particular, spherical aberration and coma can be effectively corrected at high magnification while maintaining a compact, lightweight lens.

[0088] It should be noted that by setting the lower limit of conditional expression (20) to 5, the effects of the first to fourth embodiments can be made more certain. Furthermore, in order to make the effects of the first to fourth embodiments more certain, it is more preferable to set the lower limit of conditional expression (20) to 6. On the other hand, by setting the upper limit of conditional expression (20) to 7, the effects of the first to fourth embodiments can be made more certain. Furthermore, in order to make the effects of the first to fourth embodiments more certain, it is more preferable to set the upper limit of conditional expression (20) to 6, 5, or even 4.

[0089] Here, an example of an observation optical system according to the second embodiment will be described. Fig. 21 is a cross-sectional view showing an observation optical system having a first observation optical system OS1 and a second observation optical system OS2. The first observation optical system OS1 and the second observation optical system OS2 are composed of identical lens components and are arranged side by side. As an example of the identical lens components, the observation optical system of Example 1 is shown.

[0090] The optical apparatus according to this embodiment has an observation optical system with the above-described configuration, which makes it possible to realize an optical apparatus equipped with a large-diameter observation optical system that can effectively correct various aberrations, achieve high magnification while maintaining a wide actual field of view, and also achieve compactness and light weight.

[0091] Here, an example of an optical device equipped with an observation optical system OS according to the fifth embodiment will be described. Fig. 22 is a cross-sectional view showing an example of the configuration of binoculars equipped with the observation optical system OS. The binoculars include a first observation optical system OS1 and a second observation optical system OS2 that is composed of the same lens components as the first observation optical system OS1, and the first observation optical system OS1 and the second observation optical system OS2 are arranged in parallel to form the binoculars. Note that the optical device is not limited to binoculars, and may also be a telescope composed of a single observation optical system OS.

[0092] Furthermore, a manufacturing method of the observation optical system OS of the first embodiment according to the sixth embodiment includes, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, a first intermediate image I1 being formed between the objective optical system O and the relay optical system R, and a second intermediate image I2 being formed between the relay optical system R and the eyepiece optical system E, and is configured to satisfy the following conditional expression: 0.060<fe / TL<0.130 (1) where fe: focal length of the eyepiece optical system TL: total optical length of the observation optical system

[0093] Furthermore, the manufacturing method of the observation optical system OS of the second embodiment relating to the seventh embodiment has, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, a first observation optical system OS1 that forms a first intermediate image I1 between the objective optical system O and the relay optical system R, and a second intermediate image I2 between the relay optical system R and the eyepiece optical system E, and further has a second observation optical system OS2 that is composed of the same lens components as the first observation optical system OS1, and the first observation optical system OS1 and the second observation optical system OS2 are arranged in parallel.

[0094] Furthermore, a manufacturing method of an observation optical system OS of the third embodiment according to the eighth embodiment has, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, a first intermediate image I1 being formed between the objective optical system O and the relay optical system R, and a second intermediate image I2 being formed between the relay optical system R and the eyepiece optical system E, and is configured to satisfy the following conditional expression: 0.040<Dm / TL<0.350 (2) where Dm: maximum air spacing between lens surfaces in the observation optical system TL: total optical length of the observation optical system

[0095] Furthermore, a manufacturing method of an observation optical system OS of the fourth embodiment according to the ninth embodiment includes, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, a first intermediate image I1 being formed between the objective optical system O and the relay optical system R, and a second intermediate image I2 being formed between the relay optical system R and the eyepiece optical system E, and at least one lens S of the lenses arranged in the objective optical system being configured to satisfy the following conditional expression: 80.00<νds (3) where νds is the Abbe number of the lens S for the d-line.

[0096] An outline of a manufacturing method for an observation optical system OS according to the sixth and eighth embodiments will be described below with reference to Fig. 23. First, an optical system is arranged (S1) so that, in order from the object side, it has an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, and a first intermediate image I1 is formed between the objective optical system O and the relay optical system R, and a second intermediate image I2 is formed between the relay optical system R and the eyepiece optical system E. Next, each optical system is arranged (S2) so as to satisfy a predetermined conditional expression.

[0097] An outline of a manufacturing method for an observation optical system OS according to the seventh embodiment will now be described with reference to Fig. 24. First, a first observation optical system OS1 is arranged (S1) so as to have, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, and to form a first intermediate image I1 between the objective optical system O and the relay optical system R, and a second intermediate image I2 between the relay optical system R and the eyepiece optical system E. Further, a second observation optical system OS2 is arranged in parallel with the first observation optical system OS1, and is composed of the same lens components as the first observation optical system OS1 (S2).

[0098] 25, an outline of a manufacturing method for an observation optical system OS according to the ninth embodiment will be described. First, an optical system is arranged (S1) to have, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, such that a first intermediate image I1 is formed between the objective optical system O and the relay optical system R, and a second intermediate image I2 is formed between the relay optical system R and the eyepiece optical system E. Next, at least one lens S of the lenses arranged in the objective optical system is configured to satisfy a predetermined conditional expression (S2).

[0099] Next, an observation optical system, an optical device, and a method for manufacturing an optical system according to a tenth embodiment of the present invention will be described. However, the present invention is not limited to the following embodiments, and any combination may be used. Furthermore, the reference symbols for the figures according to the embodiments may be used independently in each drawing to avoid complication of explanation due to an increase in the number of reference symbols. Therefore, even if reference symbols common to other drawings are used, they do not necessarily have the same configuration as those in the other drawings.

[0100] First, an observation optical system according to the tenth embodiment will be described. The observation optical system OS according to the tenth embodiment comprises, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, a first intermediate image I1 being located between the objective optical system O and the relay optical system R, and a second intermediate image I2 being located between the relay optical system R and the eyepiece optical system E, the relay optical system R being composed of, in order from the object side, a front group RF and a rear group RR, with an air gap between the front group RF and the rear group RR, each of the front group RF and the rear group RR having a positive lens, the positive lens AL of the front group located closest to the observation side having an Abbe number vdAL for the d-line greater than 40.00, and the positive lens B1 of the rear group located closest to the object side having an Abbe number vdB1 for the d-line less than 40.00, When there are a plurality of combinations of the front group positive lens AL and the rear group positive lens B1, the one having the largest difference in Abbe number between the front group positive lens AL and the rear group positive lens B1 with respect to the d-line is used, and when there is a negative single lens between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group.

[0101] The objective optical system O has positive refractive power and, for example, collects light from a distant object to form a first intermediate image I1, which is an inverted image. The relay optical system R has positive refractive power and re-images the first intermediate image I1, which is an inverted image formed by the objective optical system O, to form a second intermediate image I2, which is an erect image. The eyepiece optical system E has positive refractive power and enlarges the second intermediate image I2, which is an erect image formed by the relay optical system R. The relay optical system R is composed of, in order from the object side, a front group RF and a rear group RR, with an air gap between the front group RF and the rear group RR, each of the front group RF and the rear group RR having a positive lens, the positive lens AL of the front group located closest to the observation side having an Abbe number vdAL for the d-line greater than 40.00, the positive lens B1 of the rear group located closest to the object side having an Abbe number vdB1 for the d-line less than 40.00, if there are multiple combinations of the front group positive lens AL and the rear group positive lens B1, the combination with the largest difference in Abbe number for the d-line between the front group positive lens AL and the rear group positive lens B1 is used, and if there is a negative single lens between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group. By configuring the observation optical system OS in this way, an observer (not shown) can observe an object to be observed at eyepoint EP. In addition, the observation optical system OS can change the spacing between some of the lenses to adjust the diopter. By forming the erecting optical system using a relay optical system R, the first intermediate image I1 formed by the objective optical system O can be appropriately reduced, magnified to the same magnification, enlarged, or variable, compared to an erecting prism, allowing for excellent correction of various aberrations occurring in the objective optical system O and the eyepiece optical system E. Image blur can also be corrected by shifting or rotating some of the lenses relative to the optical axis. Furthermore, the diameter and overall length of the erecting optical system can be reduced compared to an erecting prism. This allows the observation optical system OS to achieve high magnification while maintaining a wide actual field of view, and also allows for a smaller, more lightweight design. This observation optical system OS may also have a focusing screen, which serves as a collimation system, located on the image plane of at least one of the first intermediate image I1 and the second intermediate image I2 (or both).The focusing screen is usually a crosshair and field ring or the like coated with chrome on a glass plate, but a display component such as a liquid crystal panel may be used to realize a variable display, or various pieces of information may be displayed as appropriate. With this configuration, the observation optical system OS of the tenth embodiment can effectively correct various aberrations, particularly spherical aberration, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), and can achieve high magnification and compactness and light weight while maintaining a wide actual field of view.

[0102] With this configuration, the viewing optical system of the tenth embodiment can further ensure the effects of the tenth embodiment by setting the lower limit 40.00 of the Abbe number νdAL for the d-line of the positive lens AL located closest to the viewing side among the positive lenses in the front group RF to 42.00. Furthermore, to further ensure the effects of the tenth embodiment, it is more preferable to set the lower limit 40.00 to 44.00, or even 46.00. Furthermore, to further ensure the effects of the tenth embodiment, it is more preferable to set the upper limit 40.00 of the Abbe number νdB1 for the d-line of the positive lens B1 located closest to the object side among the positive lenses in the rear group RR to 38.00. Furthermore, to further ensure the effects of the tenth embodiment, it is more preferable to set the lower limit 36.00, or even 34.00. Furthermore, with this configuration, the viewing optical system of the tenth embodiment has at least one positive lens A of the front group positive lenses satisfying the following conditional expressions (21) and (22): 1.400<ndA<1.650 (21) 60.00<νdA (22) where, ndA: refractive index of the front group positive lens A for the d line, νdA: Abbe number of the front group positive lens A for the d line.

[0103] Here, the Abbe number v for the d-line is expressed by the following equation, where nC is the refractive index for the C-line (wavelength 656.3 nm), nd is the refractive index for the d-line (wavelength 587.6 nm), and nF is the refractive index for the F-line (wavelength 486.1 nm): v = (nd - 1) / (nF - nC) The same equation for the Abbe number for the d-line applies to the subsequent conditional expressions, so explanation will be omitted.

[0104] The conditional expressions (21) and (22) are conditional expressions that define the refractive index for the d-line and the Abbe number of the front group positive lens A. By satisfying the conditional expression (21), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration, i.e., axial chromatic aberration, lateral chromatic aberration, etc., can be corrected well, and by satisfying the conditional expression (22), various aberrations, particularly chromatic aberration, i.e., axial chromatic aberration, lateral chromatic aberration, etc., can be corrected well, thereby achieving a high magnification while maintaining a wide actual field of view, and also enabling a reduction in size and weight.

[0105] Note that by setting the lower limit of conditional expression (21) to 1.4100, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (21) to 1.4200, 1.4300, 1.4400, 1.4500, 1.4600, 1.4700, 1.4800, or even 1.4900. On the other hand, by setting the upper limit of conditional expression (21) to 1.6300, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (21) to 1.6150, 1.6000, 1.5800, 1.5600, 1.5400, 1.5200, 1.5100, or even 1.5000. Note that by setting the lower limit of conditional expression (22) to 61.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (22) to 62.00, 65.00, 67.00, 68.00, 69.00, 70.00, 71.00, 73.00, 76.00, 78.00, 80.00, or even 81.00. On the other hand, by setting the upper limit of conditional expression (22) to "<100.00," the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (22) to 98.00, 96.00, 94.00, 92.00, 90.00, 88.00, 86.00, or even 84.00.

[0106] In the viewing optical system according to the tenth embodiment, it is desirable that at least one positive lens B among the positive lenses in the rear group satisfy the following condition: 15.00<νdB<40.00 (23) where νdB is the Abbe number of the positive lens B in the rear group for the d-line.

[0107] Conditional expression (23) defines the Abbe number for the d-line of the rear group positive lens B. By satisfying conditional expression (23), various aberrations, particularly chromatic aberrations, such as axial chromatic aberration and lateral chromatic aberration, can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can also be achieved.

[0108] It should be noted that by setting the lower limit of conditional expression (23) to 16.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (23) to 17.00, 18.00, 19.00, 20.00, 21.00, 22.00, or even 23.00. On the other hand, by setting the upper limit of conditional expression (23) to 38.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (23) to 36.00, 34.00, 32.00, 30.00, 28.00, 26.00, 25.00, or even 24.00.

[0109] In the viewing optical system according to the tenth embodiment, it is desirable that the front group positive lens A satisfy the following condition: 60.00<νdAav (24) where νdAav is the average value of the Abbe number of the front group positive lens A for the d line.

[0110] Conditional expression (24) defines the average value of the Abbe number for the d-line of the front group positive lens A. By satisfying conditional expression (24), various aberrations, particularly chromatic aberrations, such as axial chromatic aberration and lateral chromatic aberration, can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can also be achieved.

[0111] Note that by setting the lower limit of conditional formula (24) to 61.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional formula (24) to 62.00, 65.00, 67.00, 68.00, 69.00, 70.00, 71.00, 73.00, 76.00, 78.00, 80.00, or even 81.00. On the other hand, by setting the upper limit of conditional formula (24) to "<100.00," the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional formula (22) to 98.00, 96.00, 94.00, 92.00, 90.00, 88.00, 86.00, or even 84.00.

[0112] In the viewing optical system according to the tenth embodiment, it is desirable that the rear group positive lens B satisfy the following condition: 15.00<νdBav<40.00 (25) where νdBav is the average value of the Abbe number of the rear group positive lens B for the d-line.

[0113] Conditional expression (25) defines the average value of the Abbe number for the d-line of the rear group positive lens B. By satisfying conditional expression (25), various aberrations, particularly chromatic aberrations, such as axial chromatic aberration and lateral chromatic aberration, can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can also be achieved.

[0114] Note that by setting the lower limit of conditional formula (25) to 16.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional formula (25) to 17.00, 18.00, 19.00, 20.00, 21.00, 22.00, or even 23.00. On the other hand, by setting the upper limit of conditional formula (25) to 38.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional formula (25) to 36.00, 34.00, 32.00, 30.00, 28.00, 26.00, 25.00, or even 24.00.

[0115] In the observation optical system according to the tenth embodiment, it is desirable that the relay optical system has a cemented lens and that the following conditional expression be satisfied: 1≦Nrc≦7 (26) where Nrc is the number of cemented lenses in the relay optical system.

[0116] Conditional expression (26) defines the number of cemented lenses in the relay optical system. By satisfying conditional expression (26), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved.

[0117] It should be noted that by setting the lower limit of conditional expression (26) to 2, the effect of the tenth embodiment can be made more certain. Furthermore, in order to make the effect of the tenth embodiment more certain, it is more preferable to set the lower limit of conditional expression (26) to 3, 4, or even 5. On the other hand, by setting the upper limit of conditional expression (26) to 6, the effect of the tenth embodiment can be made more certain. Furthermore, in order to make the effect of the tenth embodiment more certain, it is more preferable to set the upper limit of conditional expression (26) to 5, 4, 3, or even 2.

[0118] It is also desirable that the observation optical system according to the tenth embodiment satisfy the following condition: 1.00<(-βr)<3.50 (27) where βr is the lateral magnification of the relay optical system.

[0119] Conditional expression (27) defines the lateral magnification of the relay optical system. By satisfying conditional expression (27), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved.

[0120] It should be noted that by setting the lower limit of conditional expression (27) to 1.10, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (27) to 1.20, 1.30, 1.40, 1.50, 1.55, 1.60, 1.65, 1.70, or even 1.75. On the other hand, by setting the upper limit of conditional expression (27) to 3.25, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (27) to 3.00, 2.80, 2.60, 2.40, 2.20, or even 2.00.

[0121] It is also desirable that the viewing optical system according to the tenth embodiment satisfy the following condition: 0.30<frr / frf<0.90 (28) where frr is the focal length of the rear group of the relay optical system, and frf is the focal length of the front group of the relay optical system.

[0122] Conditional expression (28) defines the ratio between the focal length of the rear group of the relay optical system and the focal length of the front group of the relay optical system. By satisfying conditional expression (28), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved.

[0123] Note that by setting the lower limit of conditional expression (28) to 0.35, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (28) to 0.40, 0.45, 0.50, 0.54, or even 0.58. On the other hand, by setting the upper limit of conditional expression (28) to 0.86, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (28) to 0.83, 0.80, 0.78, 0.76, 0.74, 0.72, 0.70, 0.68, 0.66, or even 0.64.

[0124] In the viewing optical system according to the tenth embodiment, it is desirable that the front group has at least three positive lenses arranged in succession.

[0125] With this configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compact and lightweight design can also be achieved.

[0126] In the viewing optical system according to the tenth embodiment, it is desirable that the rear group has at least three positive lenses arranged in succession.

[0127] With this configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compact and lightweight design can also be achieved.

[0128] In the observation optical system according to the tenth embodiment, it is desirable that the lens L21 in the front group closest to the object side has a meniscus shape with its concave surface facing the object side, and that the following condition be satisfied: −1.00<(R212−R211) / (R212+R211)<1.00 (29) where R211 is the radius of curvature of the object-side surface of the lens L21 in the front group, and R212 is the radius of curvature of the observation-side surface of the lens L21 in the front group.

[0129] Conditional expression (29) defines the shape of lens L21 in the front group. By satisfying conditional expression (29), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved.

[0130] Note that by setting the lower limit of conditional expression (29) to -0.80, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (29) to -0.60, -0.50, -0.40, -0.30, -0.20, -0.10, 0.00, 0.10, 0.20, or even 0.30. On the other hand, by setting the upper limit of conditional expression (29) to 0.95, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (29) to 0.85, 0.80, 0.70, 0.60, 0.50, 0.40, 0.30, 0.20, 0.10, 0.00, -0.10, -0.20, or even -0.30.

[0131] In the observation optical system according to the tenth embodiment, it is desirable that the second-most lens L22 in the front group from the object side has a meniscus shape with its concave surface facing the object side, and that the following condition be satisfied: −1.00<(R222−R221) / (R222+R221)<1.00 (30) where R221 is the radius of curvature of the object-side surface of lens L22 in the front group, and R222 is the radius of curvature of the observation-side surface of lens L22 in the front group.

[0132] Conditional expression (30) defines the shape of the second lens element L22 from the object side in the front group. By satisfying conditional expression (30), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved.

[0133] It should be noted that by setting the lower limit of conditional expression (30) to -0.90, the effect of the tenth embodiment can be made more certain. Furthermore, in order to make the effect of the tenth embodiment more certain, it is more preferable to set the lower limit of conditional expression (30) to -0.80, -0.70, -0.60, -0.50, -0.40, -0.30, -0.20, -0.10, 0.00, 0.10, 0.20, or even 0.30. On the other hand, by setting the upper limit of conditional expression (30) to 0.80, the effect of the tenth embodiment can be made more certain. Furthermore, in order to make the effect of the tenth embodiment more certain, it is more preferable to set the upper limit of conditional expression (30) to 0.60, 0.50, 0.40, 0.30, 0.20, 0.10, 0.00, -0.10, -0.20, or even -0.30.

[0134] It is also desirable that the viewing optical system according to the tenth embodiment satisfy the following condition: 0.040<DmR / TLR<0.700 (31) where DmR is the maximum air space between the lens surfaces in the rear group, and TLR is the total optical length of the rear group.

[0135] Conditional expression (31) defines the ratio between the maximum air spacing between lens surfaces in the rear group and the total optical length of the rear group. By satisfying conditional expression (31), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, and chromatic aberrations, i.e., axial chromatic aberration and lateral chromatic aberration, can be effectively corrected, achieving high magnification while maintaining a wide actual field of view and enabling a compact and lightweight lens. Note that the air spacing in the DmR range is the air-equivalent length when an optical component with no refractive power, such as a prism, is located between the lens surfaces. The total optical length of the rear group is the distance from the lens surface closest to the object to the lens surface closest to the observation on the optical axis in the rear group.

[0136] Note that by setting the lower limit of conditional expression (31) to 0.070, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (31) to 0.100, 0.150, 0.200, 0.240, 0.270, 0.300, 0.320, 0.340, 0.360, or even 0.380. On the other hand, by setting the upper limit of conditional expression (31) to 0.650, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (31) to 0.600, 0.550, 0.530, 0.520, 0.510, 0.500, 0.490, 0.480, 0.470, 0.460, or even 0.450.

[0137] In the viewing optical system according to the tenth embodiment, it is desirable that the maximum air spacing DmR between the lens surfaces in the rear group is the object-side air spacing of the lens closest to the viewing side in the rear group.

[0138] With this configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compact and lightweight design can also be achieved.

[0139] In the observation optical system according to the tenth embodiment, it is desirable that at least one positive lens C among the lenses arranged in the objective optical system satisfies the following condition: 80.00<νdC (32) where νdC is the Abbe number for the d-line of the positive lens C of the objective optical system.

[0140] Conditional expression (32) defines the Abbe number for the d-line of the positive lens C in the objective optical system. By satisfying conditional expression (32), various aberrations, particularly chromatic aberrations, such as axial chromatic aberration and lateral chromatic aberration, can be effectively corrected, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can also be achieved.

[0141] Note that by setting the lower limit of conditional expression (32) to 80.50, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (32) to 81.00, 81.50, or even 82.00. On the other hand, by setting the upper limit of conditional expression (32) to "<100.00," the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (22) to 98.00, 96.00, 94.00, 92.00, 90.00, 88.00, 86.00, or even 84.00.

[0142] Furthermore, in the observation optical system according to the tenth embodiment, it is desirable that at least two positive lenses C are disposed in the objective optical system.

[0143] With this configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compact and lightweight design can also be achieved.

[0144] Furthermore, in the observation optical system according to the tenth embodiment, it is desirable that the lens component L1 closest to the object side of the objective optical system has a biconvex shape and satisfies the following condition: −1.00<(R2+R1) / (R2−R1)<1.00 (33) where, R1: radius of curvature of the object-side surface of the lens component L1 closest to the object side of the objective optical system, R2: radius of curvature of the observation-side surface of the lens component L1 closest to the object side of the objective optical system. Note that the lens component refers to a single lens or a cemented lens.

[0145] Conditional expression (33) defines the shape of the lens component L1 closest to the object side in the objective optical system. By satisfying conditional expression (33), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight design can be achieved.

[0146] It should be noted that by setting the lower limit of conditional expression (33) to -0.80, the effect of the tenth embodiment can be made more certain. Furthermore, in order to make the effect of the tenth embodiment more certain, it is more preferable to set the lower limit of conditional expression (33) to -0.60, -0.50, -0.40, -0.30, -0.20, -0.10, 0.00, 0.10, 0.20, or even 0.30. On the other hand, by setting the upper limit of conditional expression (33) to 0.80, the effect of the tenth embodiment can be made more certain. Furthermore, in order to make the effect of the tenth embodiment more certain, it is more preferable to set the upper limit of conditional expression (33) to 0.70, 0.60, 0.52, 0.40, 0.32, 0.20, 0.10, 0.00, -0.10, -0.20, or even -0.30.

[0147] In the observation optical system according to the tenth embodiment, it is desirable that the lens closest to the observation side of the objective optical system is a focusing lens.

[0148] With this configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compact and lightweight design can also be achieved.

[0149] It is also desirable that the observation optical system according to the tenth embodiment satisfy the following condition: 4.00<tan θ′ / tan θ<30.00 (34) where 2θ: actual field of view of the observation optical system, unit [°] 2θ′: apparent field of view of the observation optical system, unit [°]

[0150] Condition (34) defines the ratio between the actual field of view of the observation optical system and the apparent field of view of the observation optical system. By satisfying condition (34), various aberrations, particularly coma, astigmatism, curvature of field, chromatic aberration (axial chromatic aberration, lateral chromatic aberration), etc., can be corrected well, a high magnification can be achieved while maintaining a wide actual field of view, and a compact and lightweight lens can be achieved.

[0151] Note that by setting the lower limit of conditional expression (34) to 4.50, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (34) to 5.00, 5.50, 6.00, 6.50, 7.00, 7.50, 8.00, 8.50, 9.00, or even 9.50. On the other hand, by setting the upper limit of conditional expression (34) to 25.00, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (34) to 20.00, 18.00, 16.00, 14.00, 12.00, 11.00, 10.60, or even 10.30.

[0152] It is also desirable that the observation optical system according to the tenth embodiment satisfy the following condition: 0.030<ER / TL<0.120 (35) where ER is the eye relief of the observation optical system, and TL is the total optical length of the observation optical system.

[0153] Conditional expression (35) defines the ratio between the eye relief of the observation optical system and the total optical length of the observation optical system. By satisfying conditional expression (35), various aberrations, particularly spherical aberration, coma, astigmatism, curvature of field, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be well corrected, an appropriate eye relief can be obtained, high magnification can be achieved while maintaining a wide actual field of view, and compactness and weight reduction can be achieved. The total optical length TL of the observation optical system is the distance from the lens surface closest to the object to the lens surface closest to the observation on the optical axis.

[0154] Note that by setting the lower limit of conditional expression (35) to 0.040, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (35) to 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, or even 0.072. On the other hand, by setting the upper limit of conditional expression (35) to 0.110, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (35) to 0.100, 0.090, 0.080, 0.075, 0.070, or even 0.065.

[0155] It is also desirable that the observation optical system according to the tenth embodiment satisfy the following condition: 0.040<Dm / TL<0.350 (36) where Dm is the maximum air space between lens surfaces in the observation optical system, and TL is the total optical length of the observation optical system.

[0156] Conditional expression (36) defines the ratio between the maximum air spacing between lens surfaces in the observation optical system and the total optical length of the observation optical system. By satisfying conditional expression (36), various aberrations, particularly spherical aberration, coma, astigmatism, field curvature, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compactness and weight reduction can be achieved. Note that the air spacing Dm is the air-equivalent length when an optical component with no refractive power, such as a prism, is present between the lens surfaces. Furthermore, the total optical length TL of the observation optical system is the distance from the lens surface closest to the object to the lens surface closest to the observation side on the optical axis.

[0157] Note that by setting the lower limit of conditional expression (36) to 0.045, the effect of the tenth embodiment can be more reliably achieved. Furthermore, in order to further ensure the effect of the tenth embodiment, it is more preferable to set the lower limit of conditional expression (36) to 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.078, 0.080, 0.090, 0.100, 0.120, 0.140, 0.160, 0.180, 0.200, 0.220, or even 0.240. On the other hand, by setting the upper limit of conditional expression (36) to 0.330, the effect of the tenth embodiment can be more reliably achieved. In order to further ensure the effect of the tenth embodiment, it is more preferable to set the upper limit of conditional expression (36) to 0.320, 0.310, 0.300, 0.290, 0.280, 0.270, 0.250, 0.230, 0.200, 0.180, 0.150, 0.130, 0.100, or even 0.080.

[0158] Furthermore, in the observation optical system according to the tenth embodiment, it is desirable that the maximum air distance Dm between lens surfaces in the observation optical system is the air distance between the surface closest to the observation side of the objective optical system and the surface closest to the object side of the relay optical system.

[0159] With this configuration, various aberrations, particularly spherical aberration, coma, chromatic aberration (i.e., axial chromatic aberration, lateral chromatic aberration), etc., can be effectively corrected, high magnification can be achieved while maintaining a wide actual field of view, and compact and lightweight design can also be achieved.

[0160] The optical apparatus according to the eleventh embodiment has an observation optical system with the above-described configuration, which makes it possible to realize an optical apparatus equipped with a large-diameter observation optical system that can effectively correct various aberrations, achieve high magnification while maintaining a wide actual field of view, and also achieve compactness and light weight.

[0161] Here, an example of an optical device equipped with the observation optical system OS of this embodiment will be described. Fig. 38 is a cross-sectional view showing an example of the configuration of binoculars equipped with the observation optical system OS. The binoculars include a first observation optical system and a second observation optical system that is composed of the same lens components as the first observation optical system, and the first observation optical system and the second observation optical system are arranged in parallel. Note that the optical device is not limited to the binoculars, and may also be a telescope composed of a single observation optical system OS.

[0162] a method for manufacturing an observation optical system OS of the tenth embodiment according to the twelfth embodiment, the method comprising: an objective optical system, an erecting optical system, and an eyepiece optical system, in order from the object side, the erecting optical system being a relay optical system; a first intermediate image being between the objective optical system and the relay optical system, and a second intermediate image being between the relay optical system and the eyepiece optical system; the relay optical system being composed of a front group and a rear group, in order from the object side, with an air gap between the front group and the rear group; the front group and the rear group having positive lenses; the positive lens AL of the front group positive lenses that is arranged closest to the observation side has an Abbe number vdAL for the d-line that is greater than 40.00; and the positive lens B1 of the rear group positive lenses that is arranged closest to the object side has an Abbe number vdB1 for the d-line that is smaller than 40.00; and when there are multiple combinations of the front group positive lens AL and the rear group positive lens B1, the combination having the largest difference in Abbe number for the d-line between the front group positive lens AL and the rear group positive lens B1 is selected. A manufacturing method for an observation optical system, in which when a negative single lens is present between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group, and at least one positive lens A among the front group positive lenses is configured to satisfy the following conditional expressions: 1.400<ndA<1.650 (21) 60.00<νdA (22) where, ndA: refractive index of the front group positive lens A for the d line, νdA: Abbe number of the front group positive lens A for the d line.

[0163] An outline of a manufacturing method of an observation optical system OS according to the twelfth embodiment will be described below with reference to Fig. 39. First, the observation optical system has, in order from the object side, an objective optical system O, an erecting optical system, and an eyepiece optical system E, the erecting optical system being a relay optical system R, a first intermediate image I1 being present between the objective optical system O and the relay optical system R, and a second intermediate image I2 being present between the relay optical system R and the eyepiece optical system E, the relay optical system being composed of, in order from the object side, a front group and a rear group, each having a positive lens, with an air gap between the front group and the rear group, and the positive lens AL of the front group, which is located closest to the observation side, has an angle .theta. The positive lens B1, which has an Abbe number vdAL greater than 40.00 and is arranged closest to the object among the positive lenses in the rear group, has an Abbe number vdB1 for the d-line that is smaller than 40.00, and if there are multiple combinations of the positive front lens AL and the positive rear lens B1, the one with the largest difference in Abbe number for the d-line between the positive front lens AL and the positive rear lens B1 is used, and if there is a negative single lens between the positive front lens AL and the positive rear lens B1, the negative single lens is included in the front group (S1). Next, each optical system is arranged so that at least one positive lens A among the positive front lenses satisfies a predetermined conditional expression (S2).

[0164] According to the above-mentioned manufacturing method of an observation optical system, it is possible to manufacture a large-diameter observation optical system in which various aberrations are well corrected, high magnification is achieved while maintaining a wide actual field of view, and it is also possible to reduce the size and weight.

[0165] It should be noted that the conditions and configurations described above each exert the effects described above, and are not limited to those that satisfy all of the conditions and configurations; the effects described above can be obtained by satisfying any one of the conditions or configurations, or a combination of any one of the conditions or configurations.

[0166] Furthermore, the examples described below are specific examples of the present invention, and the present invention is not limited to these. The following content can be adopted as appropriate within the scope that does not impair the optical performance of the observation optical system of this embodiment.

[0167] For example, the following embodiments are presented as numerical examples of the observation optical system. Some lenses or partial lens groups may be used as focusing lenses, and the system may be applied to autofocusing, and motor drive for autofocusing (such as an ultrasonic motor, a stepping motor, or a VCM motor) is also possible.

[0168] In addition, some lenses or partial lens groups may be moved so as to have a displacement component perpendicular to the optical axis, or may be rotated (oscillated) in a plane including the optical axis to create an anti-vibration lens that corrects image blur caused by camera shake or the like.

[0169] The lens surface may be spherical, flat, or aspherical. A spherical or flat lens surface is preferred because it facilitates lens processing and assembly adjustment and prevents degradation of optical performance due to errors in processing and assembly adjustment. It is also preferred because it minimizes degradation of imaging performance even when the image plane is misaligned. If the lens surface is aspherical, the aspherical surface may be any of the following aspherical surfaces: a ground aspherical surface, a glass-molded aspherical surface in which glass is molded into an aspherical shape, or a hybrid aspherical surface in which a resin is molded into an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0170] The aperture stop is preferably disposed inside or outside the lens group, but it is also possible to use the lens frame to fulfill the role of the aperture stop without providing a member serving as the aperture stop.

[0171] Furthermore, each lens surface may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high contrast and high optical performance.

[0172] With the above-described configuration, it is possible to provide a large-diameter observation optical system OS that has good optical performance, achieves high magnification while maintaining a wide actual field of view, and can also be made small and lightweight, and an optical device that includes this observation optical system OS.

[0173] Each example according to this embodiment will be described below with reference to the drawings. Tables 1 to 16 are tables showing the specifications of the first to sixteenth examples.

[0174] 1 is a cross-sectional view of the observation optical system of the first embodiment, with the left side of the observation optical system OS representing the object side and the right side representing the observation side, and showing, in order from the object side, the objective lens O, the first intermediate image I1, the relay lens R, the second intermediate image I2, the eyepiece lens E, and the eyepoint EP. In this cross-sectional view of the observation optical system, the lenses are designated, in order from the object side (left side of the page), as L11, L12, L13, ...

[0175] 1 relating to the first embodiment are used independently for each embodiment to avoid complication of explanation due to an increase in the number of digits of the reference symbols. Therefore, even if common reference symbols are used in drawings relating to other embodiments, they do not necessarily have the same configuration as the other embodiments.

[0176] Furthermore, for example, Figure 2 shows various aberration diagrams for the observation optical system according to Example 1, showing spherical aberration, astigmatism, lateral aberration, distortion, chromatic aberration of magnification, and other aberrations. These aberration diagrams demonstrate that the observation optical system OS exhibits excellent imaging performance with well-corrected aberrations. Here, h is the height from the optical axis, which is 1 / 2 the objective lens aperture Φ; θ is 1 / 2 the actual field of view; and d and g represent the aberration curves for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm), respectively. For astigmatism, the solid line represents the sagittal image plane, and the dotted line represents the meridional image plane. The horizontal axis is in units of 1 / m. In each example, the C-line (wavelength 656.3 nm), d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and g-line (wavelength 435.8 nm) are selected as the targets for calculating aberration characteristics.

[0177] In the table (Basic specifications), Φ is the diameter of the objective lens, Φe is the maximum effective diameter of the eyepiece lens, 2θ is the actual field of view (maximum angle of incidence, unit: °), 2θ' is the apparent field of view (maximum angle of emergence, unit: °), ER is the eye relief, TL is the total optical length of the observation optical system (the distance from the lens surface closest to the object to the lens surface closest to the observation on the optical axis), TLR is the total optical length of the rear group of relay lenses (the distance from the lens surface closest to the object to the lens surface closest to the observation on the optical axis in the rear group of relay lenses), fo is the focal length of the objective lens, fr is the focal length of the relay lens, frf is the focal length of the front group of relay lenses, frr is the focal length of the rear group of relay lenses, fe is the focal length of the eyepiece, fcom is the combined focal length of the objective lens and relay lens, nds is the refractive index of lens S of the objective lens for the d-line, νds is the Abbe number of lens S of the objective lens for the d-line, D1 is the distance from the object side of the lens component located second from the object side of the objective lens to the observation side of the eyepiece, D2 is the distance from the observation side of the relay lens to the object side of the eyepiece, fe1 is the focal length of the negative lens closest to the object in the eyepiece, and rL is the lens closest to the observation side in the eyepiece. the radius of curvature of the surface, Ne is the number of lenses in the eyepiece, βr is the lateral magnification of the relay lens, Dm is the maximum air space between lens surfaces in the observation optical system, DmR is the maximum air space between lens surfaces in the rear relay lens group, νdAL is the Abbe number for the d-line of the positive lens AL in the front relay lens group that is located closest to the observation side, νdB1 is the Abbe number for the d-line of the positive lens B1 in the rear relay lens group that is located closest to the object side, ndA is the refractive index for the d-line of the positive lens A in the front relay lens group, νdA is the refractive index for the d-line of the positive lens A in the front relay lens group where vdB is the Abbe number for the d-line of the positive lens B in the rear relay lens group, vdAav is the average Abbe number for the d-line of the positive lens A in the front relay lens group, vdBav is the average Abbe number for the d-line of the positive lens B in the rear relay lens group, vdC is the Abbe number for the d-line of the positive lens C in the objective lens, R211 is the radius of curvature of the object-side surface of the lens L21 closest to the object in the front relay lens group, R212 is the radius of curvature of the observation-side surface of the lens L21 closest to the object in the front relay lens group, and R221 is the radius of curvature of the object-side surface of the lens L22 that is second from the object side in the front relay lens group,R222 is the radius of curvature of the observation side surface of the second lens L22 from the most object side in the front group of the relay lens, R1 is the radius of curvature of the object side surface of the lens component L1 most object side of the objective lens, R2 is the radius of curvature of the observation side surface of the lens component L1 most object side of the objective lens, and Nrc is the number of cemented lenses in the relay lens.

[0178] In the (surface data) table, the surface number indicates the order of the optical surface from the object side along the direction of light ray travel, r indicates the radius of curvature of each optical surface, d indicates the surface spacing, which is the distance on the optical axis from each optical surface to the next optical surface (or intermediate image plane, eye point), nd indicates the refractive index of the material of the optical element with respect to the d-line, and νd indicates the Abbe number of the material of the optical element with respect to the d-line. Also, "∞" for the radius of curvature indicates a plane or an intermediate image plane. The refractive index of air, "1.00000," is omitted.

[0179] In the (aspheric surface data) table, the aspheric surface is expressed by the following formula (a), where y is the height in the direction perpendicular to the optical axis, S(y) is the distance along the optical axis from the tangent plane of the vertex of each aspheric surface at height y to each aspheric surface (amount of sag), r is the radius of curvature of the reference spherical surface (paraxial radius of curvature), k is the conic constant, and An is the aspheric coefficient of order n (n = 4, 6, 8, 10). In the following examples, "E-n" represents "×10-n." For example, "-6.391E-05" represents "-6.391×10-5."

[0180] S(y)=(y2 / r) / [1+{1-(k+1)×y2 / r2}1 / 2] +A4×y4+A6×y6+A8×y8+A10×y10 (a)

[0181] In each example, the second-order aspherical coefficient A2 is omitted because it is 0. In the table of each example, aspherical surfaces are marked with an asterisk (*) to the right of the surface number.

[0182] In the following, for all specification values, the focal length f, radius of curvature r, surface spacing d, and other lengths are generally expressed in "mm" unless otherwise specified, but this is not limited to this because the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced. Furthermore, the unit is not limited to "mm" and other appropriate units can be used.

[0183] The explanations of the tables and aberration diagrams up to this point are common to all the embodiments, and will not be repeated below.

[0184] (First Example) Figure 1 is a cross-sectional view of an observation optical system according to the first example. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E, and the image is observed through the eyepiece lens E at an eyepoint EP located at the eye relief ER. The above description is common to all examples, and will not be repeated below.

[0185] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a meniscus positive lens L23 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a meniscus negative lens L25 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a meniscus positive lens L27 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L28 and a biconcave negative lens L29, and a cemented lens formed by cementing a biconcave negative lens L30 and a meniscus positive lens L31 with its convex surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L41 having a meniscus lens shape with its concave surface facing the object side and a positive lens L42 having a meniscus lens shape with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0186] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0187] Table 1 below shows the values ​​of each parameter in the first embodiment. (Table 1) First Example (Basic specifications) Magnification 8.01 Φ (aperture diameter of objective lens) 42.00 Φe (maximum effective diameter of eyepiece lens) 36.40 2θ (actual field of view) 9.64 2θ' (apparent field of view) 68.0 ER (eye relief) 15.594 TL (total optical length of observation optical system) 189.299 fo (focal length of objective lens) 74.123 fr (focal length of relay lens) 9.920 fe (focal length of eyepiece lens) 14.821 fcom (combined focal length of objective lens and relay lens) -118.738 Dm (maximum air spacing between lens surfaces in observation optical system) 17.869 nds (refractive index for d-line of lens S of objective lens) 1.45600 νds (Abbe number for d-line of lens S of objective lens) 91.37 D1 (distance from the object side of the lens component located second furthest from the object in the objective lens to the observation side of the eyepiece) 175.599 D2 (distance from the observation side of the relay lens to the object side of the eyepiece) 7.500 fe1 (focal length of the negative lens closest to the object in the eyepiece) -67.986 rL (radius of curvature of the lens surface closest to the object in the eyepiece) 97.317 Nrc (number of cemented lenses in the relay lens) 5 Ne (number of lenses in the eyepiece) 6 (Surface data) Surface number r d nd νd 1 43.121 2.000 1.80400 46.60 2 35.000 11.500 1.45600 91.37 3 -88.987 0.200 4 37.680 11.200 1.45600 91.37 5 -44.875 1.500 1.80400 46.60 6 115.412 17.869 7 -122.716 3.250 1.60300 65.44 8 -60.947 5.000 1.84666 23.80 9 -40.644 7.712 10 35.000 2.000 1.48749 70.32 11 19.382 10.000 12 -10.747 1.000 1.48749 70.32 13 -1402.896 4.010 14 (First intermediate image) ∞ 4.000 15 14.000 6.000 1.85026 32.35 16 -18.838 1.000 1.75520 27.57 17 11.203 3.000 18 -184.484 3.896 1.80400 46.60 19 -14.717 0.200 20 19.067 5.528 1.59319 67.90 21 -10.123 1.000 1.84666 23.80 22 -65.037 11.514 23 53.786 3.121 1.72916 54.61 24 -23.297 2.273 1.84666 23.80 25 -22.813 5.161 26 12.399 5.792 1.79504 28.69 27 -11.301 3.604 1.84666 23.80 28 10.195 3.500 29 -11.000 2.200 1.54814 45.51 30 15.746 3.546 1.80400 46.60 31 79.726 3.495 32 (Second intermediate image) ∞ 4.005 33 -55.570 1.200 1.84666 23.80 34 -1622.286 13.800 1.80400 46.60 35 -21.623 0.200 36 237.047 6.200 1.72916 54.61 37 -138.449 0.200 38 41.449 6.300 1.59319 67.90 39 -357.089 0.200 40 23.500 9.923 1.59319 67.90 41 -56.603 1.200 1.80518 25.45 42 97.317 15.594 43(Eyepoint) .

[0188] FIG. 2 is a diagram showing various aberrations of the observation optical system according to the first example, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0189] 3 is a cross-sectional view of an observation optical system according to Example 2. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0190] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a meniscus positive lens L23 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a meniscus negative lens L25 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a meniscus positive lens L27 with its concave surface facing the object side, a cemented lens formed by cementing a meniscus positive lens L28 with its convex surface facing the object side and a meniscus negative lens L29 with its convex surface facing the object side, and a cemented lens formed by cementing a meniscus negative lens L30 with its concave surface facing the object side and a meniscus negative lens L31 with its concave surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42, a cemented lens formed by cementing a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0191] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0192] Table 2 below shows the values ​​of the various parameters in the second embodiment. (Table 2) Second Example (Basic specifications) Magnification 10.02 Φ 42.00 Φe 42.00 2θ 8.01 2θ' 70.0 ER 15.051 TL 199.909 fo 74.123 fr 8.708 fe 17.008 fcom -170.454 Dm 17.869 nds 1.45600 νds 91.37 D1 186.209 D2 14.264 fe1 -82.205 rL 80.000 Nrc 5 Ne 6 (Surface data) Surface number r d nd νd 1 43.121 2.000 1.80400 46.60 2 35.000 11.500 1.45600 91.37 3 -88.987 0.200 4 37.680 11.200 1.45600 91.37 5 -44.875 1.500 1.80400 46.60 6 115.412 17.869 7 -122.716 3.250 1.60300 65.44 8 -60.947 5.000 1.84666 23.80 9 -40.644 7.712 10 35.000 2.000 1.48749 70.32 11 19.382 10.000 12 -10.747 1.000 1.48749 70.32 13 -1402.896 4.010 14(First intermediate image) ∞ 4.000 15 14.000 6.000 1.85026 32.35 16 -18.838 1.000 1.75520 27.57 17 11.203 3.000 18 -184.484 3.896 1.80400 46.60 19 -14.717 0.200 20 19.067 5.528 1.59319 67.90 21 -10.123 1.000 1.84666 23.80 22 -65.037 11.514 23 53.786 3.121 1.72916 54.61 24 -23.297 2.273 1.84666 23.80 25 -22.813 10.481 26 10.165 2.913 1.83481 42.73 27 12.059 2.200 1.84666 23.80 28 10.000 3.200 29 -10.000 1.878 1.85026 32.35 30 -34.290 2.200 1.78472 25.64 31 -372.546 9.203 32 (Second intermediate image) ∞ 5.061 33 -76.790 1.500 1.84666 23.80 34 750.000 14.300 1.75500 52.34 35 -25.194 0.200 36 74.833 6.900 1.48749 70.32 37 -133.618 0.200 38 51.837 7.600 1.48749 70.32 39 -141.285 0.200 40 24.300 11.900 1.59319 67.90 41 -72.611 1.200 1.80518 25.45 42 80.000 15.051 43(Eyepoint) .

[0193] FIG. 4 is a diagram showing various aberrations of the observation optical system according to the second example, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0194] 5 is a cross-sectional view of an observation optical system according to Example 3. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0195] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a meniscus positive lens L23 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a meniscus negative lens L25 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a meniscus positive lens L27 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L28 and a biconcave negative lens L29, and a cemented lens formed by cementing a biconcave negative lens L30 and a meniscus positive lens L31 with its convex surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L41 having a meniscus lens shape with its concave surface facing the object side and a positive lens L42 having a meniscus lens shape with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0196] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0197] Table 3 below shows the values ​​of the various parameters in the third embodiment. (Table 3) Third Example (Basic specifications) Magnification 8.00 Φ 42.00 Φe 36.40 2θ 9.64 2θ' 68.0 ER 15.645 TL 190.101 fo 74.221 fr 9.920 fe 14.821 fcom -118.553 Dm 18.715 nds 1.43384 νds 95.16 D1 176.401 D2 7.456 fe1 -67.986 rL 97.317 Nrc 5 Ne 6 (Surface data) Surface number r d nd νd 1 44.718 2.000 1.80400 46.60 2 39.747 11.500 1.43384 95.16 3 -75.315 0.200 4 37.920 11.200 1.43384 95.16 5 -40.425 1.500 1.80400 46.60 6 127.086 18.715 7 -157.654 3.250 1.60300 65.44 8 -54.000 5.000 1.84666 23.80 9 -39.235 7.712 10 35.000 2.000 1.48749 70.32 11 19.382 10.000 12 -10.747 1.000 1.48749 70.32 13 -1402.896 4.010 14(First intermediate image) ∞ 4.000 15 14.000 6.000 1.85026 32.35 16 -18.838 1.000 1.75520 27.57 17 11.203 3.000 18 -184.484 3.896 1.80400 46.60 19 -14.717 0.200 20 19.067 5.528 1.59319 67.90 21 -10.123 1.000 1.84666 23.80 22 -65.037 11.514 23 53.786 3.121 1.72916 54.61 24 -23.297 2.273 1.84666 23.80 25 -22.813 5.161 26 12.399 5.792 1.79504 28.69 27 -11.301 3.604 1.84666 23.80 28 10.195 3.500 29 -11.000 2.200 1.54814 45.51 30 15.746 3.546 1.80400 46.60 31 79.726 3.449 32 (Second intermediate image) ∞ 4.007 33 -55.570 1.200 1.84666 23.80 34 -1622.286 13.800 1.80400 46.60 35 -21.623 0.200 36 237.047 6.200 1.72916 54.61 37 -138.449 0.200 38 41.449 6.300 1.59319 67.90 39 -357.089 0.200 40 23.500 9.923 1.59319 67.90 41 -56.603 1.200 1.80518 25.45 42 97.317 15.645 43(Eyepoint) .

[0198] FIG. 6 is a diagram showing various aberrations of the observation optical system according to the third example, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0199] 7 is a cross-sectional view of an observation optical system according to Example 4. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0200] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a meniscus positive lens L23 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a meniscus negative lens L25 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a meniscus positive lens L27 with its concave surface facing the object side, a cemented lens formed by cementing a meniscus positive lens L28 with its convex surface facing the object side and a meniscus negative lens L29 with its convex surface facing the object side, and a cemented lens formed by cementing a meniscus negative lens L30 with its concave surface facing the object side and a meniscus negative lens L31 with its concave surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42, a cemented lens formed by cementing a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0201] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0202] Table 4 below shows the values ​​of each parameter in the fourth embodiment. (Table 4) Fourth Example (Basic specifications) Magnification 9.99 Φ 42.00 Φe 42.00 2θ 8.01 2θ' 70.0 ER 15.130 TL 200.664 fo 74.221 fr 8.708 fe 17.008 fcom -169.878 Dm 18.715 nds 1.43384 νds 95.16 D1 186.964 D2 14.173 fe1 -82.205 rL 80.000 Nrc 5 Ne 6 (Surface data) Surface number r d nd νd 1 44.718 2.000 1.80400 46.60 2 39.747 11.500 1.43384 95.16 3 -75.315 0.200 4 37.920 11.200 1.43384 95.16 5 -40.425 1.500 1.80400 46.60 6 127.086 18.715 7 -157.654 3.250 1.60300 65.44 8 -54.000 5.000 1.84666 23.80 9 -39.235 7.712 10 35.000 2.000 1.48749 70.32 11 19.382 10.000 12 -10.747 1.000 1.48749 70.32 13 -1402.896 4.010 14(First intermediate image) ∞ 4.000 15 14.000 6.000 1.85026 32.35 16 -18.838 1.000 1.75520 27.57 17 11.203 3.000 18 -184.484 3.896 1.80400 46.60 19 -14.717 0.200 20 19.067 5.528 1.59319 67.90 21 -10.123 1.000 1.84666 23.80 22 -65.037 11.514 23 53.786 3.121 1.72916 54.61 24 -23.297 2.273 1.84666 23.80 25 -22.813 10.481 26 10.165 2.913 1.83481 42.73 27 12.059 2.200 1.84666 23.80 28 10.000 3.200 29 -10.000 1.878 1.85026 32.35 30 -34.290 2.200 1.78472 25.64 31 -372.546 9.109 32 (Second intermediate image) ∞ 5.064 33 -76.790 1.500 1.84666 23.80 34 750.000 14.300 1.75500 52.34 35 -25.194 0.200 36 74.833 6.900 1.48749 70.32 37 -133.618 0.200 38 51.837 7.600 1.48749 70.32 39 -141.285 0.200 40 24.300 11.900 1.59319 67.90 41 -72.611 1.200 1.80518 25.45 42 80.000 15.130 43(Eyepoint) .

[0203] FIG. 8 is a diagram showing various aberrations of the observation optical system according to the fourth example, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0204] 9 is a cross-sectional view of an observation optical system according to Example 5. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0205] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a meniscus positive lens L23 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a meniscus negative lens L25 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a meniscus positive lens L27 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L28 and a biconcave negative lens L29, and a cemented lens formed by cementing a biconcave negative lens L30 and a meniscus positive lens L31 with its convex surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L41 having a meniscus lens shape with its concave surface facing the object side and a positive lens L42 having a meniscus lens shape with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0206] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0207] Table 5 below shows the values ​​of each parameter in the fifth embodiment. (Table 5) Fifth Example (Basic specifications) Magnification 8.01 Φ 42.00 Φe 36.20 2θ 9.64 2θ' 68.0 ER 15.598 TL 189.348 fo 74.119 fr 9.920 fe 14.821 fcom -118.702 Dm 17.919 nds 1.49782 νds 82.57 D1 175.648 D2 7.499 fe1 -67.986 rL 97.317 Nrc 5 Ne 6 (Surface data) Surface number r d nd νd 1 47.758 2.000 1.80400 46.60 2 37.703 11.500 1.49782 82.57 3 -82.986 0.200 4 36.846 11.200 1.49782 82.57 5 -41.138 1.500 1.80400 46.60 6 73.398 17.919 7 -116.592 3.250 1.60300 65.44 8 -47.881 5.000 1.84666 23.80 9 -36.763 7.712 10 35.000 2.000 1.48749 70.32 11 19.382 10.000 12 -10.747 1.000 1.48749 70.32 13 -1402.896 4.010 14(First intermediate image) ∞ 4.000 15 14.000 6.000 1.85026 32.35 16 -18.838 1.000 1.75520 27.57 17 11.203 3.000 18 -184.484 3.896 1.80400 46.60 19 -14.717 0.200 20 19.067 5.528 1.59319 67.90 21 -10.123 1.000 1.84666 23.80 22 -65.037 11.514 23 53.786 3.121 1.72916 54.61 24 -23.297 2.273 1.84666 23.80 25 -22.813 5.161 26 12.399 5.792 1.79504 28.69 27 -11.301 3.604 1.84666 23.80 28 10.195 3.500 29 -11.000 2.200 1.54814 45.51 30 15.746 3.546 1.80400 46.60 31 79.726 3.491 32 (Second intermediate image) ∞ 4.008 33 -55.570 1.200 1.84666 23.80 34 -1622.286 13.800 1.80400 46.60 35 -21.623 0.200 36 237.047 6.200 1.72916 54.61 37 -138.449 0.200 38 41.449 6.300 1.59319 67.90 39 -357.089 0.200 40 23.500 9.923 1.59319 67.90 41 -56.603 1.200 1.80518 25.45 42 97.317 15.598 43(Eyepoint) .

[0208] FIG. 10 is a diagram showing various aberrations of the observation optical system according to the fifth example, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0209] 11 is a cross-sectional view of an observation optical system according to Example 6. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0210] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a meniscus positive lens L23 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a meniscus negative lens L25 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a meniscus positive lens L27 with its concave surface facing the object side, a cemented lens formed by cementing a meniscus positive lens L28 with its convex surface facing the object side and a meniscus negative lens L29 with its convex surface facing the object side, and a cemented lens formed by cementing a meniscus negative lens L30 with its concave surface facing the object side and a meniscus negative lens L31 with its concave surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42, a cemented lens formed by cementing a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0211] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0212] Table 6 below shows the values ​​of each parameter in the sixth embodiment. (Table 6) Sixth Example (Basic specifications) Magnification 10.02 Φ 42.00 Φe 42.00 2θ 8.00 2θ' 70.0 ER 15.036 TL 199.958 fo 74.119 fr 8.708 fe 17.008 fcom -170.375 Dm 17.919 nds 1.49782 νds 82.57 D1 186.258 D2 14.263 fe1 -82.205 rL 80.000 Nrc 5 Ne 6 (Surface data) Surface number r d nd νd 1 47.758 2.000 1.80400 46.60 2 37.703 11.500 1.49782 82.57 3 -82.986 0.200 4 36.846 11.200 1.49782 82.57 5 -41.138 1.500 1.80400 46.60 6 73.398 17.919 7 -116.592 3.250 1.60300 65.44 8 -47.881 5.000 1.84666 23.80 9 -36.763 7.712 10 35.000 2.000 1.48749 70.32 11 19.382 10.000 12 -10.747 1.000 1.48749 70.32 13 -1402.896 4.010 14(First intermediate image) ∞ 4.000 15 14.000 6.000 1.85026 32.35 16 -18.838 1.000 1.75520 27.57 17 11.203 3.000 18 -184.484 3.896 1.80400 46.60 19 -14.717 0.200 20 19.067 5.528 1.59319 67.90 21 -10.123 1.000 1.84666 23.80 22 -65.037 11.514 23 53.786 3.121 1.72916 54.61 24 -23.297 2.273 1.84666 23.80 25 -22.813 10.481 26 10.165 2.913 1.83481 42.73 27 12.059 2.200 1.84666 23.80 28 10.000 3.200 29 -10.000 1.878 1.85026 32.35 30 -34.290 2.200 1.78472 25.64 31 -372.546 9.195 32 (Second intermediate image) ∞ 5.068 33 -76.790 1.500 1.84666 23.80 34 750.000 14.300 1.75500 52.34 35 -25.194 0.200 36 74.833 6.900 1.48749 70.32 37 -133.618 0.200 38 51.837 7.600 1.48749 70.32 39 -141.285 0.200 40 24.300 11.900 1.59319 67.90 41 -72.611 1.200 1.80518 25.45 42 80.000 15.036 43(Eyepoint) .

[0213] FIG. 12 is a diagram showing various aberrations of the observation optical system according to Example 6, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0214] 13 is a cross-sectional view of an observation optical system according to Example 7. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0215] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a positive lens L13 having a meniscus lens shape with its convex surface facing the object side, and a positive lens L14 having a meniscus lens shape with its convex surface facing the object side. The relay lens R is composed of, in order from the object side, a biconcave negative lens L21, a biconvex positive lens L22, a meniscus positive lens L23 with its concave surface facing the object side, a meniscus positive lens L24 with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28, a meniscus negative lens L29 with its concave surface facing the object side, a biconvex positive lens L30, a meniscus positive lens L31 with its convex surface facing the object side, a biconcave negative lens L32, and a meniscus positive lens L33 with its concave surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42, a biconvex positive lens L43, a meniscus-shaped negative lens L44 with its concave surface facing the object side, and a meniscus-shaped positive lens L45 with its convex surface facing the object side.

[0216] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d7, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d32 and d33; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0217] Table 7 below shows the values ​​of each parameter in the seventh embodiment. (Table 7) Seventh Example (Basic specifications) Magnification 10.02 Φ 42.00 Φe 33.00 2θ 8.00 2θ' 69.9 ER 13.932 TL 200.000 fo 67.687 fr 8.899 fe 16.306 fcom -163.307 Dm 50.800 nds 1.43384 νds 95.163 D1 189.600 D2 9.600 fe1 -30.947 rL 116.740 Nrc 2 Ne 5 (Surface data) Surface number r d nd νd 1 84.551 2.000 1.90265 35.771 2 40.733 8.200 1.43384 95.163 3 -248.700 0.200 4 39.210 7.300 1.43384 95.163 5 1658.312 15.800 6 33.563 3.300 1.49782 82.571 7 42.991 47.800 8 (First intermediate image) ∞ 3.000 9 -9.091 1.400 1.48749 70.441 10 59.187 1.300 11* 233.980 5.200 1.85207 40.149 12 -15.000 0.500 13 -70.835 4.600 1.87071 40.729 14 -16.233 1.000 15* -54.038 3.000 1.85207 40.149 16 -41.207 1.600 17 12.973 5.300 1.71700 47.928 18 -9.981 1.000 1.86074 23.078 19 9.939 1.600 20 -19.572 1.800 1.75211 25.048 21 9.091 3.900 1.70000 48.081 22 -13.993 5.000 23 -9.091 2.700 1.86074 23.078 24 -9.725 1.900 25 30.752 3.000 1.86074 23.078 26 -37.124 7.100 27 55.790 2.900 1.48749 70.441 28 100.180 6.400 29 -9.091 3.000 1.86074 23.078 30 67.630 2.300 31 -20.738 3.500 1.85207 40.149 32* -17.000 4.477 33 (Second intermediate image) ∞ 5.123 34 -237.620 3.000 1.92286 20.880 35 32.658 12.000 1.80400 46.598 36 -25.910 0.200 37 37.153 9.500 1.59319 67.901 38 -44.709 1.500 1.86074 23.078 39 -108.822 0.200 40 21.968 6.400 1.59319 67.901 41 116.740 13.932 42(Eye point) (Aspheric data) Surface k A4 A6 A8 A10 11 0.000E+00 3.291E-05 1.425E-07 -1.251E-08 5.676E-11 15 0.000E+00 -6.391E-05 1.771E-08 -4.416E-09 7.216E-11 32 0.000E+00 -1.440E-04 -1.126E-06 2.418E-08 -2.505E-10 .

[0218] FIG. 14 is a diagram showing various aberrations of the observation optical system according to Example 7, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0219] 15 is a cross-sectional view of an observation optical system according to Example 8. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0220] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a meniscus-shaped negative lens L11 with its convex surface facing the object side and a biconvex positive lens L12, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14, a cemented lens formed by cementing together a meniscus-shaped positive lens L15 with its concave surface facing the object side and a meniscus-shaped positive lens L16 with its concave surface facing the object side, a meniscus-shaped negative lens L17 with its convex surface facing the object side, and a meniscus-shaped negative lens L18 with its concave surface facing the object side. The relay lens R is composed of, in order from the object side, a cemented lens formed by cementing a biconvex positive lens L21 and a biconcave negative lens L22 together, a positive lens L23 having a meniscus shape with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L24 and a negative lens L25 having a meniscus shape with its concave surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L26 and a negative lens L27 having a meniscus shape with its concave surface facing the object side, a cemented lens formed by cementing a positive lens L28 having a meniscus shape with its convex surface facing the object side and a negative lens L29 having a meniscus shape with its convex surface facing the object side, and a cemented lens formed by cementing a negative lens L30 having a meniscus shape with its concave surface facing the object side and a negative lens L31 having a meniscus shape with its concave surface facing the object side. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L41 having a meniscus lens shape with its concave surface facing the object side and a positive lens L42 having a meniscus lens shape with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44, a biconvex positive lens L45, and a biconcave negative lens L46.

[0221] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d6, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L12 and L13; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L41.

[0222] Table 8 below shows the values ​​of each parameter in the eighth embodiment. (Table 8) Eighth Example (Basic specifications) Magnification 10.07 Φ 42.00 Φe 46.60 2θ 9.00 2θ' 76.8 ER 15.101 TL 200.062 fo 71.312 fr 9.803 fe 18.557 fcom -186.860 Dm 16.228 nds ​​1.45600 νds 91.3748 D1 186.362 D2 15.299 fe1 -103.315 rL 80.000 Nrc 5 Ne 6 (Surface data) Surface number r d nd νd 1 40.857 2.000 1.80400 46.5977 2 35.000 11.500 1.45600 91.3748 3 -102.820 0.200 4 35.386 11.200 1.45600 91.3748 5 -45.471 1.500 1.80400 46.5977 6 140.895 16.228 7 -69.136 2.675 1.60300 65.4413 8 -47.171 3.216 1.84666 23.7966 9 -36.089 5.490 10 35.000 2.000 1.48749 70.3188 11 19.991 10.000 12 -9.777 1.000 1.48749 70.3188 13 -181.036 4.311 14 (First intermediate image) ∞ 4.000 15 14.492 6.000 1.85026 32.3529 16 -20.373 1.000 1.75520 27.5711 17 11.838 3.000 18 -703.488 3.900 1.80400 46.5977 19 -15.212 0.200 20 18.621 6.200 1.59319 67.9006 21 -10.052 1.000 1.84666 23.7966 22 -105.579 9.762 23 49.290 3.572 1.72916 54.6115 24 -17.841 2.200 1.84666 23.7966 25 -21.598 7.345 26 10.300 2.599 1.83481 42.7334 27 12.739 2.200 1.84666 23.7966 28 11.000 3.600 29 -10.000 5.965 1.85026 32.3529 30 -39.023 5.800 1.78472 25.6384 31 -146.626 10.044 32 (Second intermediate image) ∞ 5.255 33 -82.935 1.500 1.84666 23.7966 34 -1612.106 14.700 1.75500 52.3363 35 -28.000 0.200 36 1016.755 8.300 1.48749 70.3188 37 -52.878 0.200 38 55.061 6.900 1.48749 70.3188 39 -3925.676 0.200 40 23.526 11.900 1.59319 67.9006 41 -191.952 1.200 1.80518 25.4483 42 80.000 15.101 43(Eyepoint) .

[0223] FIG. 16 is a diagram showing various aberrations of the observation optical system according to Example 8, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0224] 17 is a cross-sectional view of an observation optical system according to Example 9. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0225] The objective lens O is composed of, in order from the object side, a biconvex positive lens L11, a meniscus-shaped positive lens L12 with its convex surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L13 and a biconcave negative lens L14. The relay lens R is composed of, in order from the object side, a biconcave negative lens L21, a biconvex positive lens L22, a meniscus-shaped positive lens L23 with its convex surface facing the object side, a biconcave negative lens L24, a meniscus-shaped positive lens L25 with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L26 and a biconcave negative lens L27, a cemented lens formed by cementing together a biconvex positive lens L28 and a biconcave negative lens L29, a meniscus-shaped positive lens L30 with its concave surface facing the object side, a meniscus-shaped positive lens L31 with its convex surface facing the object side, and a biconcave negative lens L32. The eyepiece E is composed of, in order from the object side, a positive lens L41 having a meniscus lens shape with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L42 and a negative lens L43 having a meniscus lens shape with its concave surface facing the object side, and a positive lens L44 having a meniscus lens shape with its convex surface facing the object side.

[0226] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d4, which satisfies conditional expression (2); lens S of the objective lens O, which satisfies conditional expressions (3) and (4), is L12; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system is surface spacing d30 and d31, which satisfies conditional expression (15); and the lens of the eyepiece optical system, which has a focal length fe1 of the negative lens nearest to the object side, which satisfies conditional expression (16), is L43.

[0227] Table 9 below shows the values ​​of each parameter in the ninth embodiment. (Table 9) Ninth Example (Basic specifications) Magnification 10.00 Φ 42.00 Φe 27.80 2θ 8.00 2θ' 70.0 ER 15.474 TL 199.458 fo 74.728 fr 14.199 fe 13.829 fcom -138.287 Dm 28.195 nds 1.49782 νds 82.57 D1 193.771 D2 12.630 fe1 -21.838 rL 1962.631 Nrc 2 Ne 4 (Surface data) Surface number r d nd νd 1 67.351 5.473 1.66382 27.35 2 -1855.800 0.214 3 49.650 5.084 1.49782 82.57 4 182.310 28.195 5 17.696 4.897 1.72916 54.61 6 -21.785 2.925 1.84666 23.80 7 11.429 18.856 8 (First intermediate image) ∞ 3.000 9 -22.325 1.000 1.84666 23.80 10 25.203 2.782 11 1178.570 4.834 1.99900 30.00 12 -13.733 0.238 13 23.399 2.835 1.92110 36.05 14 51.184 18.855 15 -28.307 3.000 1.84666 23.80 16 17.303 0.896 17 -157.551 2.744 1.83917 42.02 18 -17.387 0.200 19 15.717 4.823 1.88000 41.00 20 -10.000 1.000 1.84666 23.80 21 10.000 0.265 22 10.742 4.930 1.86869 41.27 23 -10.000 3.000 1.84666 23.80 24 35.480 21.682 25 -28.050 3.631 1.85000 23.00 26 -16.187 1.051 27 16.634 4.007 1.85000 23.00 28 44.723 7.236 29 -16.869 1.052 1.71524 28.35 30 12.006 8.503 31 (Second intermediate image) ∞ 4.127 32 -26.662 7.509 1.75500 52.34 33 -14.916 0.200 34 146.137 12.278 1.75500 52.34 35 -13.606 1.000 1.84666 23.80 36 -53.250 0.200 37 21.068 6.936 1.75500 52.34 38 1962.631 15.474 39(Eyepoint) .

[0228] FIG. 18 is a diagram showing various aberrations of the observation optical system according to Example 9, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0229] 19 is a cross-sectional view of an observation optical system according to Example 10. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. A first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E, and observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0230] The objective lens O is composed of, in order from the object side, a positive lens L11 having a meniscus lens shape with a convex surface facing the object side, a positive lens L12 having a meniscus lens shape with a convex surface facing the object side, a biconvex positive lens L13, and a biconcave negative lens L14. The relay lens R is composed of, in order from the object side, a biconcave negative lens L21, a positive lens L22 having a meniscus lens shape with a concave surface facing the object side, a negative lens L23 having a meniscus lens shape with a concave surface facing the object side, a positive lens L24 having a meniscus lens shape with a convex surface facing the object side, a biconcave negative lens L25, a cemented lens formed by cementing a biconcave negative lens L26 and a biconvex positive lens L27, a cemented lens formed by cementing a biconvex positive lens L28 and a biconcave negative lens L29, a positive lens L30 having a meniscus lens shape with a concave surface facing the object side, a positive lens L31 having a meniscus lens shape with a convex surface facing the object side, and a biconcave negative lens L32. The eyepiece E is composed of, in order from the object side, a meniscus-shaped positive lens L41 with its concave surface facing the object side, a cemented lens formed by cementing together a biconcave negative lens L42 and a biconvex positive lens L43, and a meniscus-shaped positive lens L44 with its convex surface facing the object side.

[0231] In this observation optical system, the maximum air spacing Dm between lens surfaces in the observation optical system is surface spacing d4, which satisfies conditional expression (2); lenses S of the objective lens O, which satisfy conditional expressions (3) and (4), are L11 and L12; the distance D2 from the surface nearest to the observation side of the relay optical system to the surface nearest to the object side of the eyepiece optical system, which satisfies conditional expression (15), is surface spacing d31 and d32; and the lens of the eyepiece optical system, which is nearest to the object and has a focal length fe1, which satisfies conditional expression (16), is L42.

[0232] Table 10 below shows the values ​​of each parameter in the tenth embodiment. (Table 10) Tenth Example (Basic specifications) Magnification 9.96 Φ 42.00 Φe 25.00 2θ 7.50 2θ' 66.5 ER 15.455 TL 194.449 fo 80.049 fr 28.363 fe 14.114 fcom -140.612 Dm 41.909 nds 1.49782 νds 82.57 D1 188.466 D2 20.502 fe1 -14.092 rL 1477.865 Nrc 2 Ne 4 (Surface data) Surface number r d nd νd 1 58.275 5.783 1.49782 82.57 2 2170.730 0.200 3 41.473 4.578 1.49782 82.57 4 77.112 41.909 5 13.475 3.494 1.732828 45.55 6 -399.104 0.461 7 -65.211 2.947 1.85 23.00 8 10.150 15.313 9 (First intermediate image) ∞ 3.420 10 -43.257 1.081 1.670203 30.01 11 35.440 1.321 12 -55.783 4.660 1.932017 34.99 13 -10.881 4.181 14 -10.000 1.191 1.792792 32.44 15 -15.186 0.200 16 11.168 4.579 1.85 23.00 17 53.240 6.335 18 -11.212 3.000 1.85 23.00 19 12.924 0.874 20 -44.180 2.374 1.85 23.00 21 10.000 4.051 1.88 41.00 22 -13.150 0.200 23 14.877 4.473 1.77614 43.92 24 -10.000 1.000 1.85 23.00 25 71.238 23.666 26 -735.964 3.318 1.85 23.00 27 -20.218 0.200 28 17.597 3.152 1.85 23.00 29 69.780 2.112 30 -34.506 1.000 1.699325 47.04 31 10.045 15.350 32 (Second intermediate image) ∞ 5.152 33 -58.169 4.853 1.88 41.00 34 -19.168 0.200 35 -85.696 1.000 1.85 23.00 36 13.999 9.923 1.650333 49.73 37 -33.536 0.200 38 19.099 6.698 1.88 41.00 39 1477.865 15.455 40(Eyepoint) .

[0233] FIG. 20 is a diagram showing various aberrations of the observation optical system according to Example 10, and it is clear that various aberrations are well corrected and that the imaging performance is excellent.

[0234] 26 is a cross-sectional view of an observation optical system according to Example 11. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. The relay lens R is composed of, in order from the object side, a front group RF and a rear group RR, and a first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER. The above description is common to all subsequent examples.

[0235] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a biconvex positive lens L13, a positive lens L14 having a meniscus lens shape with its convex surface facing the object side, and a negative lens L15 having a meniscus lens shape with its convex surface facing the object side. The front group RF of the relay lens R is composed of, in order from the object side, a negative lens L21 having a meniscus shape with a concave surface facing the object side, a positive lens L22 having a meniscus shape with a concave surface facing the object side, a biconvex positive lens L23, a positive lens L24 having a plano-convex shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28. The rear group RR of the relay lens R is composed of, in order from the object side, a biconvex positive lens L29, a positive lens L30 having a meniscus shape with a convex surface facing the object side, a positive lens L31 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L32 and a biconcave negative lens L33, and a biconcave negative lens L34. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a plano-concave negative lens L41 with its concave surface facing the object side and a plano-convex positive lens L42 with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44 and a biconcave negative lens L45.

[0236] In this viewing optical system, the positive lens AL of the positive lenses in the relay lens front group that is located closest to the viewing side is L28, the positive lens B1 of the positive lenses in the relay lens rear group that is located closest to the object side is L29, the positive lenses A in the relay lens front group that satisfy the conditional expressions (21), (22), and (24) are L22, L23, L24, L25, and L28, the positive lenses B in the relay lens rear group that satisfy the conditional expressions (23) and (25) are L29, L30, L31, and L32, and the cemented lenses of the relay lens that satisfy the conditional expression (26) are L25+26, L27+28, and L32+33, The lens closest to the object in the front relay lens group that satisfies conditional expression (29) is L21, the second lens closest to the object in the front relay lens group that satisfies conditional expression (30) is L22, the maximum air spacing DmR between lens surfaces in the rear group that satisfies conditional expression (31) is d33, the positive lenses C of the objective lens that satisfy conditional expression (32) are L12, L13, and L14, the lens component L1 closest to the object in the objective lens that satisfies conditional expression (33) is L11+12, and the maximum air spacing Dm between lens surfaces in the observation optical system that satisfies conditional expression (36) is the surface spacing d9+d10.

[0237] Table 11 below shows the values ​​of each parameter in the eleventh embodiment. (Table 11) Eleventh Example (Basic Specifications) Magnification 10.00 Φ (Aperture of Objective Lens) 42.00 2θ (Actual Field of View) 8.00 2θ' (Apparent Field of View) 69.90 ER (Eye Relief) 15.30 TL (Total Optical Length of Observation Optical System) 246.04 TLR (Total Optical Length of Rear Group of Relay Lens) (d25 to d34) 35.35 fo (Focal Length of Objective Lens) (L11 to L15) 89.654 fr (Focal Length of Relay Lens) (L21 to L34) 10.061 frf (Focal Length of Front Group of Relay Lens) (L21 to L28) 34.355 frr (Focal Length of Rear Group of Relay Lens) (L29 to L34) 21.141 fe (Focal Length of Eyepiece Lens) (L41 to L45) 16.542 βr (lateral magnification of relay lens) (L21 to L34) -1.855 Dm (maximum air spacing between lens surfaces in the observation optical system) (d9 + d10) 63.50 DmR (maximum air spacing between lens surfaces in the rear relay lens group) (d33) 14.05 νdAL (Abbe number for the d-line of the positive lens AL in the front relay lens group, which is located closest to the observation side) (L28) 82.57 νdB1 (Abbe number for the d-line of the positive lens B1 in the rear relay lens group, which is located closest to the object side) (L29) 23.80 ndA (refractive index for the d-line of the positive lens A in the front relay lens group) (L22, 23, 24, 25, 28) 1.49782 νdA (Abbe number for the d-line of the positive lens A in the front relay lens group) (L22,23,24,25,28) 82.57 νdB (Abbe number for the d-line of the positive lens B in the rear relay lens group) (L29, 30, 31, 32) 23.80 νdAav (average value of the Abbe number for the d-line of the positive lens A in the front relay lens group) (L22, 23, 24, 25, 28) 82.57 νdBav (average value of the Abbe number for the d-line of the positive lens B in the rear relay lens group) (L29, 30, 31, 32) 23.80 νdC (Abbe number for the d-line of the positive lens C in the objective lens group) (L12, 13, 14) 82.57 R211 (radius of curvature of the object-side surface of the lens L21 in the front relay lens group) (r11) -19.196 R212 (radius of curvature of the observation-side surface of the lens L21 in the front relay lens group) (r12) -46.026 R221 (radius of curvature of the object-side surface of the front group lens L22 of the relay lens) (r13) -31.735 R222 (radius of curvature of the observation-side surface of the front group lens L22 of the relay lens) (r14) -15.842 R1 (radius of curvature of the object-side surface of the lens component L1 of the objective lens closest to the object) (r1) 157.059 R2 (radius of curvature of the observation-side surface of the lens component L1 of the objective lens closest to the object) (r3) -351.506 Nrc (number of cemented lenses in the relay lens) (L25+26, L27+28, L32+33) 3 However, in the above specifications, (r1) etc. are the surface numbers corresponding to the numerical values, (d9) etc. are the surface spacing numbers corresponding to the numerical values, (L11) etc. are the lens numbers corresponding to the numerical values, and the same applies to the subsequent examples. (Face data) Face number r d nd νd 1 157.059 2.20 1.84666 23.80 2 60.631 6.30 1.49782 82.57 3 -351.506 0.70 4 63.626 6.60 1.49782 82.57 5 -307.500 0.30 6 55.456 3.20 1.49782 82.57 7 87.585 17.03 8 347.656 1.70 1.60300 65.44 9 105.085 59.27 10(First intermediate image)∞ 4.23 11 -19.196 5.40 1.84666 23.80 12 -46.026 3.35 13 -31.735 8.60 1.49782 82.57 14 -15.842 0.45 15 118.791 4.10 1.49782 82.57 16 -38.268 0.20 17 29.417 3.30 1.49782 82.57 18 ∞ 0.20 19 13.588 6.00 1.49782 82.57 20 -36.804 1.00 1.84666 23.80 21 22.084 2.55 22 -11.172 1.00 1.84666 23.80 23 38.935 9.50 1.49782 82.57 24 -11.646 8.45 25 86.276 2.00 1.84666 23.80 26 -229.397 2.95 27 29.141 2.30 1.84666 23.80 28 93.515 2.05 29 15.508 2.30 1.84666 23.80 30 24.167 1.30 31 242.384 3.70 1.84666 23.80 32 -10.954 1.00 1.83481 42.73 33 32.546 14.05 34 -15.195 3.70 1.75520 27.57 35 62.069 9.05 36 (Second intermediate image) ∞ 5.71 37 -43.657 1.80 1.84666 23.80 38 ∞ 13.00 1.80400 46.60 39 -23.666 0.20 40 51.799 10.60 1.59319 67.90 41 -64.407 0.20 42 24.483 12.90 1.59319 67.90 43 -56.000 1.60 1.84666 23.80 44 154.314 15.30 45 (Eye point) .

[0238] FIG. 27 is a diagram showing various aberrations of the observation optical system according to Example 11, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0239] 28 is a cross-sectional view of an observation optical system according to Example 12. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. The relay lens R is composed of, in order from the object side, a front group RF and a rear group RR, and a first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0240] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a biconvex positive lens L13, a positive lens L14 having a meniscus lens shape with its convex surface facing the object side, and a negative lens L15 having a meniscus lens shape with its convex surface facing the object side. The front group RF of the relay lens R is composed of, in order from the object side, a negative lens L21 having a meniscus shape with a concave surface facing the object side, a positive lens L22 having a meniscus shape with a concave surface facing the object side, a biconvex positive lens L23, a positive lens L24 having a plano-convex shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28. The rear group RR of the relay lens R is composed of, in order from the object side, a biconvex positive lens L29, a positive lens L30 having a meniscus shape with a convex surface facing the object side, a positive lens L31 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L32 and a biconcave negative lens L33, and a biconcave negative lens L34. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a plano-concave negative lens L41 with its concave surface facing the object side and a plano-convex positive lens L42 with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44 and a biconcave negative lens L45.

[0241] In this viewing optical system, the positive lens AL of the positive lenses in the relay lens front group that is located closest to the viewing side is L28, the positive lens B1 of the positive lenses in the relay lens rear group that is located closest to the object side is L29, the positive lenses A in the relay lens front group that satisfy the conditional expressions (21), (22), and (24) are L22, L23, L24, L25, and L28, the positive lenses B in the relay lens rear group that satisfy the conditional expressions (23) and (25) are L29, L30, L31, and L32, and the cemented lenses of the relay lens that satisfy the conditional expression (26) are L25+26, L27+28, and L32+33, The lens closest to the object in the front relay lens group that satisfies conditional expression (29) is L21, the second lens closest to the object in the front relay lens group that satisfies conditional expression (30) is L22, the maximum air spacing DmR between lens surfaces in the rear group that satisfies conditional expression (31) is d33, the positive lenses C of the objective lens that satisfy conditional expression (32) are L12, L13, and L14, the lens component L1 closest to the object in the objective lens that satisfies conditional expression (33) is L11+12, and the maximum air spacing Dm between lens surfaces in the observation optical system that satisfies conditional expression (36) is the surface spacing d9+d10.

[0242] Table 12 below shows the values ​​of each parameter in the twelfth embodiment. (Table 12) 12th Example (Basic specifications) Magnification 10.00 Φ 42.00 2θ 8.00 2θ' 69.90 ER 15.10 TL 246.03 TLR(d25~d34) 34.99 fo(L11~L15) 89.692 fr(L21~L34) 10.089 frf(L21~L28) 34.401 frr(L29~L34) 21.163 fe(L41~L45) 16.583 βr(L21~L34) -1.851 Dm(d9+d10) 63.51 DmR(d33) 14.05 νdAL(L28) 82.57 νdB1(L29) 23.80 νdA(L22,23,24,25,28) 82.57 νdB(L29,30,31,32) 23.80 νdAav(L22,23,24,25,28) 82.57 νdBav(L29,30,31,32) 23.80 νdC(L12,13,14) 82.57 R211(r11) -19.189 R212(r12) -46.485 R221(r13) -31.907 R222(r14) -15.395 R1(r1) 155.401 R2(r3) -360.614 Nrc(L25+26,L27+28,L32+33) 3 (Face data) Face number r d nd νd 1 155.401 2.20 1.84666 23.80 2 60.370 6.30 1.49782 82.57 3 -360.614 0.71 4 63.587 6.60 1.49782 82.57 5 -303.467 0.27 6 55.675 3.20 1.49782 82.57 7 87.681 17.04 8 343.709 1.70 1.60300 65.44 9 104.792 59.30 10 (First intermediate image) ∞ 4.21 11 -19.189 5.40 1.84666 23.80 12 -46.485 3.34 13 -31.907 8.60 1.49782 82.57 14 -15.395 0.48 15 169.117 4.10 1.49782 82.57 16 -37.843 0.20 17 29.039 3.30 1.49782 82.57 18 ∞ 0.25 19 13.615 6.00 1.49782 82.57 20 -36.573 1.00 1.84666 23.80 21 22.172 2.53 22 -11.165 1.00 1.84666 23.80 23 39.036 9.50 1.49782 82.57 24 -11.644 8.50 25 100.490 2.00 1.84666 23.80 26 -183.263 2.60 27 28.670 2.30 1.84666 23.80 28 93.952 2.03 29 15.516 2.30 1.84666 23.80 30 24.026 1.31 31 229.072 3.70 1.84666 23.80 32 -11.129 1.00 1.83481 42.73 33 32.530 14.05 34 -14.871 3.70 1.75520 27.57 35 67.863 9.08 36 (Second intermediate image) ∞ 5.93 37 -44.040 1.80 1.84666 23.80 38 ∞ 13.00 1.80400 46.60 39 -23.811 0.20 40 51.798 10.60 1.59319 67.90 41 -64.759 0.20 42 24.208 12.90 1.59319 67.90 43 -54.359 1.60 1.84666 23.80 44 142.289 15.10 45(Eye point) .

[0243] FIG. 29 is a diagram showing various aberrations of the observation optical system according to Example 12, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0244] 30 is a cross-sectional view of an observation optical system according to Example 13. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. The relay lens R is composed of, in order from the object side, a front group RF and a rear group RR, and a first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0245] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a biconvex positive lens L13, a positive lens L14 having a meniscus lens shape with its convex surface facing the object side, and a negative lens L15 having a meniscus lens shape with its convex surface facing the object side. The front group RF of the relay lens R is composed of, in order from the object side, a negative lens L21 having a meniscus shape with a concave surface facing the object side, a positive lens L22 having a meniscus shape with a concave surface facing the object side, a biconvex positive lens L23, a positive lens L24 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28. The rear group RR of the relay lens R is composed of, in order from the object side, a biconvex positive lens L29, a positive lens L30 having a meniscus shape with a convex surface facing the object side, a positive lens L31 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L32 and a biconcave negative lens L33, and a biconcave negative lens L34. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42, a cemented lens formed by cementing a biconvex positive lens L43, a biconvex positive lens L44 and a biconcave negative lens L45.

[0246] In this viewing optical system, the positive lens AL of the positive lenses in the relay lens front group that is located closest to the viewing side is L28, the positive lens B1 of the positive lenses in the relay lens rear group that is located closest to the object side is L29, the positive lenses A in the relay lens front group that satisfy the conditional expressions (21), (22), and (24) are L22, L23, L24, L25, and L28, the positive lenses B in the relay lens rear group that satisfy the conditional expressions (23) and (25) are L29, L30, L31, and L32, and the cemented lenses of the relay lens that satisfy the conditional expression (26) are L25+26, L27+28, and L32+33, The lens closest to the object in the front relay lens group that satisfies conditional expression (29) is L21, the second lens closest to the object in the front relay lens group that satisfies conditional expression (30) is L22, the maximum air spacing DmR between lens surfaces in the rear group that satisfies conditional expression (31) is d33, the positive lenses C of the objective lens that satisfy conditional expression (32) are L12, L13, and L14, the lens component L1 closest to the object in the objective lens that satisfies conditional expression (33) is L11+12, and the maximum air spacing Dm between lens surfaces in the observation optical system that satisfies conditional expression (36) is the surface spacing d9+d10.

[0247] Table 13 below shows the values ​​of each parameter in the thirteenth embodiment. (Table 13) 13th Example (Basic specifications) Magnification 10.00 Φ 42.00 2θ 8.00 2θ' 69.90 ER 15.20 TL 245.03 TLR(d25~d34) 34.78 fo(L11~L15) 89.809 fr(L21~L34) 9.706 frf(L21~L28) 33.330 frr(L29~L34) 20.544 fe(L41~L45) 16.548 βr(L21~L34) -1.847 Dm(d9+d10) 63.42 DmR(d33) 14.15 νdAL(L28) 82.57 νdB1(L29) 23.80 ndA(L22,23,24,25,28) 1.49782 νdA(L22,23,24,25,28) 82.57 νdB(L29,30,31,32) 23.80 νdAav(L22,23,24,25,28) 82.57 νdBav(L29,30,31,32) 23.80 νdC(L12,13,14) 82.57 R211(r11) -19.139 R212(r12) -43.252 R221(r13) -30.342 R222(r14) -15.411 R1(r1) 133.761 R2(r3) -616.481 Nrc(L25+26,L27+28,L32+33) 3 (Face data) Face number r d nd νd 1 133.761 2.20 1.84666 23.80 2 56.775 6.30 1.49782 82.57 3 -616.481 0.20 4 63.663 6.60 1.49782 82.57 5 -288.496 0.25 6 56.348 3.20 1.49782 82.57 7 89.196 17.03 8 357.298 1.70 1.60300 65.44 9 106.164 59.26 10 (First intermediate image) ∞ 4.16 11 -19.139 5.40 1.84666 23.80 12 -43.252 3.30 13 -30.342 8.60 1.49782 82.57 14 -15.411 0.43 15 187.678 4.20 1.49782 82.57 16 -37.931 0.20 17 26.939 3.30 1.49782 82.57 18 287.852 0.24 19 13.257 6.10 1.49782 82.57 20 -37.420 1.00 1.84666 23.80 21 22.171 2.55 22 -11.127 1.00 1.84666 23.80 23 38.986 9.50 1.49782 82.57 24 -11.660 8.61 25 65.955 2.00 1.84666 23.80 26 -415.191 2.25 27 30.412 2.20 1.84666 23.80 28 93.128 1.97 29 15.425 2.30 1.84666 23.80 30 24.214 1.31 31 268.710 3.70 1.84666 23.80 32 -10.622 1.00 1.83481 42.73 33 32.570 14.15 34 -15.093 3.90 1.75520 27.57 35 52.874 8.33 36 (Second intermediate image) ∞ 5.44 37 -52.407 1.80 1.84666 23.80 38 424.412 13.70 1.80400 46.60 39 -24.020 0.21 40 52.365 10.40 1.59319 67.90 41 -66.942 1.24 42 23.872 12.20 1.59319 67.90 43 -56.319 1.60 1.84666 23.80 44 135.406 15.20 45(Eye Point) .

[0248] FIG. 31 is a diagram showing various aberrations of the observation optical system according to Example 13, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0249] 32 is a cross-sectional view of an observation optical system according to Example 14. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. The relay lens R is composed of, in order from the object side, a front group RF and a rear group RR, and a first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0250] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a biconvex positive lens L13, a positive lens L14 having a meniscus lens shape with its convex surface facing the object side, and a negative lens L15 having a meniscus lens shape with its convex surface facing the object side. The front group RF of the relay lens R is composed of, in order from the object side, a negative lens L21 having a meniscus shape with a concave surface facing the object side, a positive lens L22 having a meniscus shape with a concave surface facing the object side, a biconvex positive lens L23, a biconvex positive lens L24, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28. The rear group RR of the relay lens R is composed of, in order from the object side, a biconvex positive lens L29, a positive lens L30 having a meniscus shape with a convex surface facing the object side, a positive lens L31 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L32 and a biconcave negative lens L33, and a biconcave negative lens L34. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing a biconcave negative lens L41 and a biconvex positive lens L42, a cemented lens formed by cementing a biconvex positive lens L43, a biconvex positive lens L44 and a biconcave negative lens L45.

[0251] In this viewing optical system, the positive lens AL of the positive lenses in the relay lens front group that is located closest to the viewing side is L28, the positive lens B1 of the positive lenses in the relay lens rear group that is located closest to the object side is L29, the positive lenses A in the relay lens front group that satisfy the conditional expressions (21), (22), and (24) are L22, L23, L24, L25, and L28, the positive lenses B in the relay lens rear group that satisfy the conditional expressions (23) and (25) are L29, L30, L31, and L32, and the cemented lenses of the relay lens that satisfy the conditional expression (26) are L25+26, L27+28, and L32+33, The lens closest to the object in the front relay lens group that satisfies conditional expression (29) is L21, the second lens closest to the object in the front relay lens group that satisfies conditional expression (30) is L22, the maximum air spacing DmR between lens surfaces in the rear group that satisfies conditional expression (31) is d33, the positive lenses C of the objective lens that satisfy conditional expression (32) are L12, L13, and L14, the lens component L1 closest to the object in the objective lens that satisfies conditional expression (33) is L11+12, and the maximum air spacing Dm between lens surfaces in the observation optical system that satisfies conditional expression (36) is the surface spacing d9+d10.

[0252] Table 14 below shows the values ​​of each parameter in the fourteenth embodiment. (Table 14) 14th Example (Basic specifications) Magnification 10.00 Φ 42.00 2θ 8.00 2θ' 69.90 ER 15.20 TL 244.93 TLR(d25~d34) 35.72 fo(L11~L15) 89.634 fr(L21~L34) 9.648 frf(L21~L28) 33.820 frr(L29~L34) 20.501 fe(L41~L45) 16.299 βr(L21~L34) -1.815 Dm(d9+d10) 63.42 DmR(d33) 14.10 νdAL(L28) 82.57 νdB1(L29) 23.80 ndA(L22,23,24,25,28) 1.49782 νdA(L22,23,24,25,28) 82.57 νdB(L29,30,31,32) 23.80 νdAav(L22,23,24,25,28) 82.57 νdBav(L29,30,31,32) 23.80 νdC(L12,13,14) 82.57 R211(r11) -19.126 R212(r12) -49.467 R221(r13) -33.101 R222(r14) -16.151 R1(r1) 146.069 R2(r3) -438.735 Nrc(L25+26,L27+28,L32+33) 3 (Face data) Face number r d nd νd 1 146.069 2.20 1.84666 23.80 2 59.000 6.20 1.49782 82.57 3 -438.735 0.23 4 63.688 6.60 1.49782 82.57 5 -289.232 0.22 6 56.587 3.20 1.49782 82.57 7 89.753 16.98 8 354.538 1.70 1.60300 65.44 9 105.836 59.35 10 (First intermediate image) ∞ 4.07 11 -19.126 5.40 1.84666 23.80 12 -49.467 3.31 13 -33.101 8.60 1.49782 82.57 14 -16.151 0.40 15 128.187 4.20 1.49782 82.57 16 -34.028 0.20 17 33.126 3.30 1.49782 82.57 18 -387.418 0.21 19 13.488 6.10 1.49782 82.57 20 -37.765 1.00 1.84666 23.80 21 22.075 2.67 22 -11.123 1.00 1.84666 23.80 23 39.301 9.50 1.49782 82.57 24 -11.648 8.64 25 69.823 2.20 1.84666 23.80 26 -365.873 2.89 27 29.923 2.20 1.84666 23.80 28 96.171 2.03 29 15.488 2.30 1.84666 23.80 30 24.427 1.30 31 304.575 3.70 1.84666 23.80 32 -10.841 1.00 1.83481 42.73 33 32.522 14.10 34 -15.284 4.00 1.75520 27.57 35 49.370 7.95 36 (Second intermediate image) ∞ 5.30 37 -50.269 1.80 1.84666 23.80 38 642.530 13.40 1.80400 46.60 39 -23.601 0.39 40 54.980 10.60 1.59319 67.90 41 -59.708 0.69 42 23.669 12.20 1.59319 67.90 43 -57.984 1.60 1.84666 23.80 44 125.433 15.20 45(Eye Point) .

[0253] FIG. 33 is a diagram showing various aberrations of the observation optical system according to Example 14, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0254] 34 is a cross-sectional view of an observation optical system according to Example 15. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. The relay lens R is composed of, in order from the object side, a front group RF and a rear group RR, and a first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0255] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a biconvex positive lens L13, a positive lens L14 having a meniscus lens shape with its convex surface facing the object side, and a negative lens L15 having a meniscus lens shape with its convex surface facing the object side. The front group RF of the relay lens R is composed of, in order from the object side, a negative lens L21 having a meniscus shape with a concave surface facing the object side, a positive lens L22 having a meniscus shape with a concave surface facing the object side, a biconvex positive lens L23, a biconvex positive lens L24, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, and a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28. The rear group RR of the relay lens R is composed of, in order from the object side, a positive lens L29 having a meniscus shape with a convex surface facing the object side, a positive lens L30 having a meniscus shape with a convex surface facing the object side, a positive lens L31 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L32 and a biconcave negative lens L33, and a biconcave negative lens L34. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L41 having a meniscus lens shape with its concave surface facing the object side and a positive lens L42 having a meniscus lens shape with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44, and a biconcave negative lens L45.

[0256] In this viewing optical system, the positive lens AL of the positive lenses in the relay lens front group that is located closest to the viewing side is L28, the positive lens B1 of the positive lenses in the relay lens rear group that is located closest to the object side is L29, the positive lenses A in the relay lens front group that satisfy the conditional expressions (21), (22), and (24) are L22, L23, L24, L25, and L28, the positive lenses B in the relay lens rear group that satisfy the conditional expressions (23) and (25) are L29, L30, L31, and L32, and the cemented lenses of the relay lens that satisfy the conditional expression (26) are L25+26, L27+28, and L32+33, The lens closest to the object in the front relay lens group that satisfies conditional expression (29) is L21, the second lens closest to the object in the front relay lens group that satisfies conditional expression (30) is L22, the maximum air spacing DmR between lens surfaces in the rear group that satisfies conditional expression (31) is d33, the positive lenses C of the objective lens that satisfy conditional expression (32) are L12, L13, and L14, the lens component L1 closest to the object in the objective lens that satisfies conditional expression (33) is L11+12, and the maximum air spacing Dm between lens surfaces in the observation optical system that satisfies conditional expression (36) is the surface spacing d9+d10.

[0257] Table 15 below shows the values ​​of each parameter in the fifteenth embodiment. (Table 15) 15th Example (Basic specifications) Magnification 10.00 Φ 42.00 2θ 8.00 2θ' 69.90 ER 15.20 TL 245.01 TLR(d25~d34) 33.68 fo(L11~L15) 88.717 fr(L21~L34) 9.623 frf(L21~L28) 34.263 frr(L29~L34) 21.418 fe(L41~L45) 16.206 βr(L21~L34) -1.821 Dm(d9+d10) 62.90 DmR(d33) 14.90 νdAL(L28) 82.57 νdB1(L29) 23.80 ndA(L22,23,24,25,28) 1.49782 νdA(L22,23,24,25,28) 82.57 νdB(L29,30,31,32) 23.80 νdAav(L22,23,24,25,28) 82.57 νdBav(L29,30,31,32) 23.80 νdC(L12,13,14) 82.57 R211(r11) -18.850 R212(r12) -103.370 R221(r13) -60.079 R222(r14) -17.559 R1(r1) 162.073 R2(r3) -301.288 Nrc(L25+26,L27+28,L32+33) 3 (Face data) Face number r d nd νd 1 162.073 2.20 1.84666 23.80 2 61.741 6.30 1.49782 82.57 3 -301.288 0.20 4 60.151 6.30 1.49782 82.57 5 -442.602 0.20 6 57.376 3.20 1.49782 82.57 7 92.214 16.90 8 486.129 1.70 1.60300 65.44 9 114.916 58.76 10 (First intermediate image) ∞ 4.14 11 -18.850 5.20 1.84666 23.80 12 -103.370 6.45 13 -60.079 4.90 1.49782 82.57 14 -17.559 0.20 15 102.854 4.40 1.49782 82.57 16 -32.371 0.20 17 26.766 4.10 1.49782 82.57 18 -337.176 0.20 19 15.015 5.80 1.49782 82.57 20 -43.992 1.00 1.84666 23.80 21 22.204 2.99 22 -11.567 1.00 1.84666 23.80 23 37.620 9.70 1.49782 82.57 24 -12.012 9.61 25 40.000 2.30 1.84666 23.80 26 383.775 2.21 27 29.185 2.20 1.84666 23.80 28 76.141 2.13 29 16.303 2.10 1.84666 23.80 30 24.948 0.84 31 160.854 3.50 1.84666 23.80 32 -12.137 1.00 1.83481 42.73 33 25.795 14.90 34 -16.022 2.50 1.75520 27.57 35 49.871 8.44 36 (Second intermediate image) ∞ 5.64 37 -40.233 1.80 1.84666 23.80 38 -827.788 13.00 1.80400 46.60 39 -23.150 0.20 40 48.460 11.50 1.59319 67.90 41 -64.325 0.20 42 23.315 13.30 1.59319 67.90 43 -56.000 1.60 1.84666 23.80 44 109.134 15.20 45(Eye Point) .

[0258] FIG. 35 is a diagram showing various aberrations of the observation optical system according to Example 15, and it is clear that various aberrations are well corrected and that the imaging performance is excellent.

[0259] 36 is a cross-sectional view of an observation optical system according to Example 16. The observation optical system OS according to this example is composed of, in order from the object side, an objective lens O, a relay lens R of an erecting optical system, and an eyepiece lens E. The relay lens R is composed of, in order from the object side, a front group RF and a rear group RR, and a first intermediate image I1 is formed between the objective lens O and the relay lens R, and a second intermediate image I2 is formed between the relay lens R and the eyepiece lens E. Observation is performed through the eyepiece lens E at an eyepoint EP located at the position of the eye relief ER.

[0260] The objective lens O is composed of, in order from the object side, a cemented lens formed by cementing together a negative lens L11 having a meniscus lens shape with its convex surface facing the object side and a biconvex positive lens L12, a biconvex positive lens L13, a positive lens L14 having a meniscus lens shape with its convex surface facing the object side, and a negative lens L15 having a meniscus lens shape with its convex surface facing the object side. The front group RF of the relay lens R is composed of, in order from the object side, a negative lens L21 having a meniscus shape with a concave surface facing the object side, a positive lens L22 having a meniscus shape with a concave surface facing the object side, a biconvex positive lens L23, a plano-convex positive lens L24 having a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L25 and a biconcave negative lens L26, a cemented lens formed by cementing a biconcave negative lens L27 and a biconvex positive lens L28, and a negative lens L29 having a meniscus shape with a concave surface facing the object side. The rear group RR of the relay lens R is composed of, in order from the object side, a positive lens L30 having a meniscus shape with a convex surface facing the object side, a positive lens L31 having a meniscus shape with a convex surface facing the object side, a positive lens L32 having a meniscus shape with a convex surface facing the object side, a cemented lens formed by cementing a biconvex positive lens L33 and a biconcave negative lens L34, and a biconcave negative lens L35. The eyepiece E is composed of, in order from the object side, a cemented lens formed by cementing together a plano-concave negative lens L41 with its concave surface facing the object side and a plano-convex positive lens L42 with its concave surface facing the object side, a cemented lens formed by cementing together a biconvex positive lens L43, a biconvex positive lens L44 and a biconcave negative lens L45.

[0261] In this observation optical system, the positive lens AL of the positive lenses in the relay lens front group and arranged closest to the observation side is L28, the positive lens B1 of the positive lenses in the relay lens rear group and arranged closest to the object side is L30, the positive lenses A in the relay lens front group that satisfy the conditional expressions (21), (22), and (24) are L22, L23, L24, L25, and L28, the positive lenses B in the relay lens rear group that satisfy the conditional expressions (23) and (25) are L30, L31, L32, and L33, and the cemented lenses of the relay lens that satisfy the conditional expression (26) are L25+26, L27+28, and L33+34, The lens closest to the object in the front relay lens group that satisfies conditional expression (29) is L21, the second lens closest to the object in the front relay lens group that satisfies conditional expression (30) is L22, the maximum air spacing DmR between lens surfaces in the rear group that satisfies conditional expression (31) is d35, the positive lenses C of the objective lens that satisfy conditional expression (32) are L12, L13, and L14, the lens component L1 closest to the object in the objective lens that satisfies conditional expression (33) is L11+12, and the maximum air spacing Dm between lens surfaces in the observation optical system that satisfies conditional expression (36) is the surface spacing d9+d10.

[0262] Table 16 below shows the values ​​of each parameter in the 16th embodiment. (Table 16) 16th Example (Basic specifications) Magnification 10.00 Φ 42.00 2θ 8.00 2θ' 69.90 ER 15.90 TL 249.90 TLR(d25~d34) 34.77 fo(L11~L15) 90.277 fr(L21~L34) 9.802 frf(L21~L28) 36.037 frr(L29~L34) 18.111 fe(L41~L45) 15.983 βr(L21~L34) -1.775 Dm(d9+d10) 63.43 DmR(d33) 14.22 νdAL(L28) 82.57 νdB1(L30) 23.80 ndA(L22,23,24,25,28) 1.49782 νdA(L22,23,24,25,28) 82.57 νdB(L30,31,32,33) 23.80 νdAav(L22,23,24,25,28) 82.57 νdBav(L30,31,32,33) 23.80 νdC(L12,13,14) 82.57 R211(r11) -18.964 R212(r12) -396.715 R221(r13) -82.847 R222(r14) -17.592 R1(r1) 164.075 R2(r3) -300.000 Nrc(L25+26,L27+28,L33+34) 3 (Face data) Face number r d nd νd 1 164.075 2.00 1.84666 23.80 2 61.144 6.63 1.49782 82.57 3 -300.000 1.05 4 64.722 6.59 1.49782 82.57 5 -260.714 0.25 6 58.728 3.32 1.49782 82.57 7 91.045 17.13 8 1066.140 1.65 1.60300 65.44 9 132.022 59.86 10 (First intermediate image)∞ 3.57 11 -18.964 5.40 1.84666 23.80 12 -396.715 3.40 13 -82.847 8.66 1.49782 82.57 14 -17.592 0.45 15 79.881 4.50 1.49782 82.57 16 -33.628 0.33 17 30.259 3.62 1.49782 82.57 18 ∞ 0.63 19 15.122 6.47 1.49782 82.57 20 -30.357 1.41 1.84666 23.80 21 23.422 3.49 22 -12.519 1.55 1.84666 23.80 23 38.033 7.82 1.49782 82.57 24 -12.104 1.00 25 -17.272 1.09 1.84666 23.80 26 -18.155 8.56 27 37.754 2.24 1.84666 23.80 28 501.098 2.45 29 38.588 2.13 1.84666 23.80 30 279.852 1.86 31 16.993 2.36 1.84666 23.80 32 25.898 1.27 33 351.061 3.23 1.84666 23.80 34 -12.274 1.13 1.83481 42.73 35 31.331 14.22 36 -21.624 3.88 1.75520 27.57 37 27.748 8.16 38 (Second intermediate image) ∞ 4.50 39 -44.876 1.88 1.84666 23.80 40 ∞ 13.95 1.80400 46.60 41 -23.249 0.20 42 65.835 10.61 1.59319 67.90 43 -55.047 0.20 44 23.369 13.44 1.59319 67.90 45 -55.892 1.80 1.84666 23.80 46 163.527 15.90 47 (Eye point) .

[0263] FIG. 37 is a diagram showing various aberrations of the observation optical system according to Example 16, and it is clear that various aberrations are well corrected and that the optical system has excellent imaging performance.

[0264] According to each of the above-described embodiments, various aberrations can be corrected well, and a large-diameter observation optical system can be realized that achieves high magnification, compactness, and light weight while maintaining a wide actual field of view.

[0265] Next, a table of [values ​​corresponding to conditional expressions] for the first to ninth embodiments (first to tenth examples) is shown below. This table shows values ​​corresponding to each of conditional expressions (1) to (20) for each example.

[0266] Conditional expression (1) 0.060<fe / TL<0.130 Conditional expression (2) 0.040<Dm / TL<0.350 Conditional expression (3) 80.00<νds Conditional expression (4) 1.4300<nds<1.5200 Conditional expression (5) 4.00<(-fcom) / fe<30.00 Conditional expression (6) 4.00<tanθ' / tanθ<30.00 Conditional expression (7) 1.00<(-fcom) / fo<3.50 Conditional expression (8) 0.030<ER / TL<0.120 Conditional expression (9) 3.00<fo / fe<8.00 Conditional expression (10) 0.030<fr / TL<0.160 Conditional expression (11) 0.40<(-fcom) / TL<1.20 Conditional expression (12) 2.50<fo / fr<10.00 Conditional expression (13) 0.40<fr / fe<2.50 Conditional expression (14) 0.70<D1 / TL<1.20 Conditional expression (15) 0.030<D2 / TL<0.200 Conditional expression (16) 0.90<(-fe1) / fe<10.00 Conditional expression (17) 2.00<rL / fe<200.00 Conditional expression (18) 0.55<Φe / Φ<1.50 Conditional expression (19) 1≦Nrc≦7 Conditional expression (20) 4≦Ne≦8

[0267] [Conditional expression corresponding values] Conditional expression 1st example 2nd example 3rd example 4th example (1) 0.078 0.085 0.078 0.085 (2) 0.094(d6) 0.089(d6) 0.098(d6) 0.093(d6) (3) 91.37(L12,13) ​​91.37(L12,13) ​​95.16(L12,13) ​​95.16(L12,13) ​​(4) 1.45600(L12,13) ​​1.45600(L12,13) ​​1.43384(L12,13) ​​1.43384(L12,13) ​​(5) 8.012 10.022 7.999 9.988 (6) 7.999 10.001 7.999 10.001 (7) 1.602 2.300 1.597 2.289 (8) 0.082 0.075 0.082 0.075 (9) 5.001 4.358 5.008 4.364 (10) 0.052 0.044 0.052 0.043 (11) 0.627 0.853 0.624 0.847 (12) 7.472 8.512 7.482 8.523 (13) 0.669 0.512 0.669 0.512 (14) 0.928 0.931 0.928 0.932 (15) 0.040(d31,32) 0.071(d31,32) 0.039(d31,32) 0.071(d31,32) (16) 4.587(L41) 4.833(L41) 4.587(L41) 4.833(L41) (17) 6.566 4.704 6.566 4.704 (18) 0.867 1.000 0.867 1.000 (19) 5 5 5 5 (20) 6 6 6 6 Conditional Expression 5th Example 6th Example 7th Example 8th Example (1) 0.078 0.085 0.082 0.093 (2) 0.095(d6) 0.090(d6) 0.254(d7) 0.081(d6) (3) 82.57(L12,13) ​​82.57(L12,13) ​​95.163(L12,13) ​​91.3748(L12,13) ​​(4) 1.49782(L12,13) ​​1.49782(L12,13) ​​1.43384(L12,13) ​​1.45600(L12,13) ​​(5) 8.009 10.018 10.015 10.069 (6) 7.999 10.013 9.995 10.071 (7) 1.602 2.299 2.413 2.620 (8) 0.082 0.075 0.070 0.075 (9) 5.001 4.358 4.151 3.843 (10) 0.052 0.044 0.044 0.049 (11) 0.627 0.852 0.817 0.934 (12) 7.472 8.512 7.606 7.275 (13) 0.669 0.512 0.546 0.528 (14) 0.928 0.931 0.948 0.932 (15 0.040(d31,32) 0.071(d31,32) 0.048(d32,33) 0.076(d31,32) (16) 4.587(L41) 4.833(L41) 1.898(L41) 5.567(L41) (17) 6.566 4.704 7.159 4.311 (18) 0.862 1.000 0.786 1.110 (19) 5 5 2 5 (20) 6 6 5 6 Conditional Expression 9th Example 10th Example (1) 0.069 0.073 (2) 0.141(d4) 0.216(d4) (3) 82.57(L12) 82.57(L11,12) (4) 1.49782(L12) 1.49782(L11,12) (5) 10.000 9.963 (6) 10.013 10.003 (7) 1.851 1.757 (8) 0.078 0.079 (9) 5.404 5.672 (10) 0.071 0.146 (11) 0.693 0.723 (12) 5.263 2.822 (13) 1.027 2.010 (14) 0.971 0.969 (15) 0.063(d30,31) 0.105(d31,32) (16) 1.579(L43) 0.998(L42) (17) 141.926 104.711 (18) 0.662 0.595 (19) 2 2 (20) 4 4 However, in the above conditional expressions, (d6) etc. after the numerical value indicates the surface spacing number corresponding to that numerical value, and (L12) etc. indicates the lens number corresponding to that numerical value.

[0268] Next, a table of [Values ​​Corresponding to Conditional Expressions] for the tenth to twelfth embodiments (11th to 16th Examples) is shown below. This table shows the values ​​corresponding to each of conditional expressions (21) to (36) for each example.

[0269] It is also possible to have a negative lens adjacent to the positive lens AL located closest to the observation side among the positive lenses in the front group, that is, a negative lens cemented to the positive lens AL or a negative single lens. In this case, the front group includes up to the negative lens.

[0270] Conditional formula (21) 1.400<ndA<1.650 Conditional formula (22) 60.00<νdA Conditional formula (23) 15.00<νdB<40.00 Conditional formula (24) 60.00<νdAav Conditional formula (25) 15.00<νdBav<40.00 Conditional formula (26) 1≦Nrc≦7 Conditional formula (27) 1.00<(-βr)<3.50 Conditional formula (28) 0.30<frr / frf<0.90 Conditional formula (29) -1.00<(R212-R211) / (R212+R211)<1.0 Conditional formula (30) -1.00 < (R222-R221) / (R222+R221) < 1.00 Conditional formula (31) 0.040 < DmR / TLR < 0.700 Conditional formula (32) 80.00 < νdC Conditional formula (33) -1.00 < (R2+R1) / (R2-R1) < 1.00 Conditional formula (34) 4.00 < tanθ' / tanθ < 30.00 Conditional formula (35) 0.030 < ER / TL < 0.120 Conditional formula (36) 0.040 < Dm / TL < 0.350

[0271] [Conditional expression corresponding values] Conditional expression 11th example 12th example 13th example 14th example (21) 1.49782 1.49782 1.49782 1.49782 (22) 82.57 82.57 82.57 82.57 (23) 23.80 23.80 23.80 23.80 (24) 82.57 82.57 82.57 82.57 (25) 23.80 23.80 23.80 23.80 (26) 3 3 3 3 (27) 1.855 1.851 1.847 1.815 (28) 0.615 0.615 0.616 0.606 (29) 0.411 0.416 0.386 0.442 (30) -0.334 -0.349 -0.326 -0.344 (31) 0.397 0.402 0.407 0.395 (32) 82.57 82.57 82.57 82.57 (33) 0.382 0.398 0.643 0.500 (34) 9.995 9.995 9.995 9.995 (35) 0.062 0.061 0.062 0.062 (36) 0.258 0.258 0.259 0.259 Conditional expression 15th embodiment 16th embodiment (21) 1.49782 1.49782 (22) 82.57 82.57 (23) 23.80 23.80 (24) 82.57 82.57 (25) 23.80 23.80 (26) 3 3 (27) 1.821 1.775 (28) 0.625 0.503 (29) 0.692 0.909 (30) -0.548 -0.650 (31) 0.442 0.409 (32) 82.57 82.57 (33) 0.300 0.293 (34) 9.995 9.995 (35) 0.062 0.064 (36) 0.257 0.254 .

[0272] OS Observation optical system O Objective lens R Relay lens RF Front group of relay lens RR Rear group of relay lens E Eyepiece lens I1 First intermediate image I2 Second intermediate image EP Eye point

Claims

1. An observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, forming a first intermediate image between the objective optical system and the relay optical system, and forming a second intermediate image between the relay optical system and the eyepiece optical system, and satisfying the following condition: 0.060<fe / TL<0.130, where fe: focal length of the eyepiece optical system TL: total optical length of the observation optical system 2. An observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, wherein the erecting optical system is a relay optical system, and wherein a first intermediate image is formed between the objective optical system and the relay optical system, and a second intermediate image is formed between the relay optical system and the eyepiece optical system, and further comprising a second observation optical system composed of the same lens components as the first observation optical system, wherein the first observation optical system and the second observation optical system are arranged in parallel.

3. An observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, forming a first intermediate image between the objective optical system and the relay optical system, and forming a second intermediate image between the relay optical system and the eyepiece optical system, and satisfying the following condition: 0.040<Dm / TL<0.350, where Dm is the maximum air space between lens surfaces in the observation optical system, and TL is the total optical length of the observation optical system.

4. An observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, forming a first intermediate image between the objective optical system and the relay optical system, and forming a second intermediate image between the relay optical system and the eyepiece optical system, and at least one lens S among the lenses arranged in the objective optical system satisfies the following condition: 80.00<νds where νds is the Abbe number of the lens S for the d line.

5. The observation optical system according to any one of claims 1 to 4, wherein at least one lens S among the lenses arranged in the objective optical system satisfies the following condition: 1.4300<nds<1.5200, where nds is the refractive index of the lens S with respect to the d line.

6. An observation optical system as described in claim 4 or 5, characterized in that at least one lens S among the lenses arranged in the objective optical system is the positive lens closest to the object among the positive lenses included in the objective optical system.

7. The observation optical system according to any one of claims 1 to 6, wherein the lens closest to the object side of the observation optical system is a negative lens.

8. The viewing optical system according to any one of claims 2 to 7, which satisfies the following condition: 0.060<fe / TL<0.130, where fe is the focal length of the eyepiece optical system, and TL is the total optical length of the viewing optical system.

9. The viewing optical system according to any one of claims 1, 2, and 4 to 8, which satisfies the following condition: 0.040<Dm / TL<0.350, where Dm is the maximum air gap between lens surfaces in the optical system, and TL is the total optical length of the viewing optical system.

10. The observation optical system according to any one of claims 1 to 3 and 5 to 9, wherein at least one lens S among the lenses arranged in the objective optical system satisfies the following condition: 80.00<νds, where νds is the Abbe number of the lens S with respect to the d line.

11. The viewing optical system according to any one of claims 1 to 10, which satisfies the following condition: 4.00<(-fcom) / fe<30.00, where fcom is the combined focal length of the objective optical system and the relay optical system, and fe is the focal length of the eyepiece optical system.

12. The viewing optical system according to any one of claims 1 to 11, which satisfies the following condition: 4.00<tan θ' / tan θ<30.00, where 2θ: actual field of view of the viewing optical system, unit [°], 2θ': apparent field of view of the viewing optical system, unit [°].

13. The viewing optical system according to any one of claims 1 to 12, which satisfies the following condition: 1.00<(-fcom) / fo<3.50, where fcom is the combined focal length of the objective optical system and the relay optical system, and fo is the focal length of the objective optical system.

14. The observation optical system according to any one of claims 1 to 13, which satisfies the following condition: 0.030<ER / TL<0.120, where ER is the eye relief of the observation optical system, and TL is the total optical length of the observation optical system.

15. The viewing optical system according to any one of claims 1 to 14, which satisfies the following condition: 3.00<fo / fe<8.00, where fo is the focal length of the objective optical system, and fe is the focal length of the eyepiece optical system.

16. The observation optical system according to any one of claims 1 to 15, which satisfies the following condition: 0.030<fr / TL<0.160, where fr is the focal length of the relay optical system, and TL is the total optical length of the observation optical system.

17. The observation optical system according to any one of claims 1 to 16, which satisfies the following condition: 0.40<(-fcom) / TL<1.20, where fcom is the combined focal length of the objective optical system and the relay optical system, and TL is the total optical length of the observation optical system.

18. The viewing optical system according to any one of claims 1 to 17, which satisfies the following condition: 2.50<fo / fr<10.00, where fo is the focal length of the objective optical system, and fr is the focal length of the relay optical system.

19. The viewing optical system according to any one of claims 1 to 18, which satisfies the following condition: 0.40<fr / fe<2.50, where fr is the focal length of the relay optical system, and fe is the focal length of the eyepiece optical system.

20. The viewing optical system according to any one of claims 1 to 19, which satisfies the following condition: 0.70<D1 / TL<1.20, where D1 is the distance from the object-side surface of the lens component located second most from the object side in the objective optical system to the observation-side surface of the eyepiece optical system, and TL is the total optical length of the viewing optical system. Note that the lens component refers to a single lens or a cemented lens.

21. The viewing optical system according to any one of claims 1 to 20, which satisfies the following condition: 0.030<D2 / TL<0.200, where D2 is the distance from the side closest to the observation side of the relay optical system to the side closest to the object side of the eyepiece optical system, and TL is the total optical length of the viewing optical system.

22. The viewing optical system according to any one of claims 1 to 21, wherein the eyepiece optical system has a negative lens and satisfies the following condition: 0.90<(-fe1) / fe<10.00, where fe1 is the focal length of the negative lens in the eyepiece optical system that is closest to the object, and fe is the focal length of the eyepiece optical system.

23. The viewing optical system according to any one of claims 1 to 22, which satisfies the following condition: 2.00<rL / fe<200.00, where rL is the radius of curvature of the lens surface of the eyepiece optical system that is closest to the viewing side, and fe is the focal length of the eyepiece optical system.

24. The viewing optical system according to any one of claims 1 to 23, which satisfies the following condition: 0.55<Φe / Φ<1.50, where Φe is the maximum effective diameter of the eyepiece optical system, and Φ is the aperture of the objective optical system.

25. The viewing optical system according to any one of claims 1 to 24, wherein the relay optical system has a cemented lens and satisfies the following condition: 1≦Nrc≦7, where Nrc is the number of cemented lenses in the relay optical system.

26. The viewing optical system according to any one of claims 1 to 25, which satisfies the following condition: 4≦Ne≦8, where Ne is the number of lenses in the eyepiece optical system.

27. An optical instrument comprising an observation optical system according to any one of claims 1 to 26.

28. A manufacturing method for an observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being formed between the objective optical system and the relay optical system, and a second intermediate image being formed between the relay optical system and the eyepiece optical system, and configured to satisfy the following condition: 0.060<fe / TL<0.130, where fe: focal length of the eyepiece optical system TL: total optical length of the observation optical system.

29. A method for manufacturing an observation optical system comprising, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, wherein the erecting optical system is a relay optical system, a first observation optical system characterized in that a first intermediate image is formed between the objective optical system and the relay optical system, and a second intermediate image is formed between the relay optical system and the eyepiece optical system, and a second observation optical system composed of the same lens components as the first observation optical system, wherein the first observation optical system and the second observation optical system are arranged in parallel.

30. A manufacturing method for an observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being formed between the objective optical system and the relay optical system, and a second intermediate image being formed between the relay optical system and the eyepiece optical system, and configured to satisfy the following condition: 0.040<Dm / TL<0.350, where Dm is the maximum air space between lens surfaces in the observation optical system, and TL is the total optical length of the observation optical system.

31. A method for manufacturing an observation optical system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being formed between the objective optical system and the relay optical system, and a second intermediate image being formed between the relay optical system and the eyepiece optical system, and at least one lens S of the lenses arranged in the objective optical system being configured to satisfy the following conditional expression: 80.00<νds, where νds is the Abbe number of the lens S with respect to the d line.

32. A telephoto lens system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being between the objective optical system and the relay optical system, and a second intermediate image being between the relay optical system and the eyepiece optical system, the relay optical system being composed of, in order from the object side, a front group and a rear group, with an air gap between the front group and the rear group, the front group and the rear group each having a positive lens, the positive lens AL of the front group located closest to the observation side has an Abbe number vdAL for the d-line greater than 40.00, the positive lens B1 of the rear group located closest to the object side has an Abbe number vdB1 for the d-line smaller than 40.00, and when there are multiple combinations of the front group positive lens AL and the rear group positive lens B1, the combination with the largest difference in Abbe number for the d-line between the front group positive lens AL and the rear group positive lens B1 is used, When a negative single lens is provided between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group, and at least one positive lens A among the front group positive lenses satisfies the following conditional expressions: 1.400<ndA<1.650 60.00<νdA, where ndA: refractive index of the front group positive lens A for the d line νdA: Abbe number of the front group positive lens A for the d line 33. The viewing optical system according to claim 32, wherein at least one positive lens B in the rear group of positive lenses satisfies the following condition: 15.00<νdB<40.00, where νdB is the Abbe number of the rear group of positive lens B for the d-line.

34. The viewing optical system according to claim 32 or 33, wherein the front group positive lens A satisfies the following condition: 60.00<νdAav, where νdAav is the average value of the Abbe number of the front group positive lens A for the d line.

35. The viewing optical system according to any one of claims 32 to 34, wherein the rear group positive lens B satisfies the following condition: 15.00<νdBav<40.00, where νdBav is the average value of the Abbe number for the d-line of the rear group positive lens B.

36. The viewing optical system according to any one of claims 32 to 35, wherein the relay optical system has a cemented lens and satisfies the following condition: 1≦Nrc≦7, where Nrc is the number of cemented lenses in the relay optical system.

37. The viewing optical system according to any one of claims 32 to 36, which satisfies the following condition: 1.00<(-βr)<3.50, where βr is the lateral magnification of the relay optical system.

38. The viewing optical system according to any one of claims 32 to 37, which satisfies the following condition: 0.30<frr / frf<0.90, where frr is the focal length of the rear group of the relay optical system, and frf is the focal length of the front group of the relay optical system.

39. The viewing optical system according to any one of claims 32 to 38, characterized in that the front group comprises at least three positive lenses arranged in succession.

40. The viewing optical system according to any one of claims 32 to 39, characterized in that the rear group comprises at least three positive lenses arranged in succession.

41. The viewing optical system according to any one of claims 32 to 40, wherein the lens L21 in the front group closest to the object side has a meniscus shape with its concave surface facing the object side, and the following condition is satisfied: -1.00<(R212-R211) / (R212+R211)<1.00, where R211 is the radius of curvature of the object-side surface of lens L21 in the front group, and R212 is the radius of curvature of the viewing-side surface of lens L21 in the front group.

42. The viewing optical system according to any one of claims 32 to 41, wherein the second lens L22 from the most object side in the front group has a meniscus shape with its concave surface facing the object side, and the following condition is satisfied: -1.00<(R222-R221) / (R222+R221)<1.00, where R221 is the radius of curvature of the object-side surface of lens L22 in the front group, and R222 is the radius of curvature of the viewing-side surface of lens L22 in the front group.

43. The viewing optical system according to any one of claims 32 to 42, which satisfies the following condition: 0.040<DmR / TLR<0.700, where DmR is the maximum air space between lens surfaces in the rear group, and TLR is the total optical length of the rear group.

44. The viewing optical system according to any one of claims 32 to 43, characterized in that the maximum air spacing DmR between lens surfaces in the rear group is the object-side air spacing of the lens in the rear group that is closest to the viewing side.

45. The viewing optical system according to any one of claims 32 to 44, wherein at least one positive lens C among the lenses arranged in the objective optical system satisfies the following conditional expression: 80.00<νdC, where νdC is the Abbe number for the d-line of the positive lens C of the objective optical system.

46. ​​The observation optical system according to claim 45, characterized in that at least two positive lenses C are arranged in the objective optical system.

47. The observation optical system according to any one of claims 32 to 46, wherein the lens component L1 closest to the object side of the objective optical system has a biconvex shape and satisfies the following condition: -1.00<(R2+R1) / (R2-R1)<1.00, where R1: radius of curvature of the object-side surface of the lens component L1 closest to the object side of the objective optical system, R2: radius of curvature of the observation-side surface of the lens component L1 closest to the object side of the objective optical system. Note that the lens component refers to a single lens or a cemented lens.

48. An observation optical system according to any one of claims 32 to 47, characterized in that the lens closest to the observation side of the objective optical system is a focusing lens.

49. The viewing optical system according to any one of claims 32 to 48, which satisfies the following condition: 4.00<tan θ' / tan θ<30.00, where 2θ: actual field of view of the viewing optical system, unit [°], 2θ': apparent field of view of the viewing optical system, unit [°].

50. The observation optical system according to any one of claims 32 to 49, which satisfies the following condition: 0.030<ER / TL<0.120, where ER is the eye relief of the observation optical system, and TL is the total optical length of the observation optical system.

51. The viewing optical system according to any one of claims 32 to 50, which satisfies the following condition: 0.040<Dm / TL<0.350, where Dm is the maximum air space between lens surfaces in the viewing optical system, and TL is the total optical length of the viewing optical system.

52. An observation optical system described in any one of claims 32 to 51, characterized in that the maximum air distance Dm between lens surfaces in the observation optical system is the air distance between the surface closest to the observation side of the objective optical system and the surface closest to the object side of the relay optical system.

53. An optical instrument comprising the observation optical system according to any one of claims 32 to 52.

54. A telephoto lens system having, in order from the object side, an objective optical system, an erecting optical system, and an eyepiece optical system, the erecting optical system being a relay optical system, a first intermediate image being between the objective optical system and the relay optical system, and a second intermediate image being between the relay optical system and the eyepiece optical system, the relay optical system being composed of, in order from the object side, a front group and a rear group, with an air gap between the front group and the rear group, the front group and the rear group having positive lenses, the positive lens AL of the front group located closest to the observation side has an Abbe number vdAL for the d-line greater than 40.00, the positive lens B1 of the rear group located closest to the object side has an Abbe number vdB1 for the d-line smaller than 40.00, and when there are multiple combinations of the front group positive lens AL and the rear group positive lens B1, the combination with the largest difference in Abbe number for the d-line between the front group positive lens AL and the rear group positive lens B1 is used, When a negative single lens is present between the front group positive lens AL and the rear group positive lens B1, the negative single lens is included in the front group, and at least one positive lens A among the front group positive lenses is configured to satisfy the following conditional expressions: 1.400<ndA<1.650 60.00<νdA, where ndA: refractive index of the front group positive lens A with respect to the d line νdA: Abbe number of the front group positive lens A with respect to the d line

Images