Observation optics and optical devices

Abstract

The present invention provides an observation optical system that offers good performance while enabling observation with a wider apparent field of view, and an optical device equipped with this observation optical system. [Solution] The observation optical system comprises a display element and an eyepiece positioned on the eye point side of the display element. The eyepiece includes at least one negative lens. When H is the half value of the longest diameter of the display area in the display element and f is the focal length of the eyepiece, the observation optical system is 0.35

Description

Technical Field

[0001] The present disclosure relates to an observation optical system and an optical device.

Background Art

[0002] Conventionally, as an eyepiece lens applicable to an observation optical system, the lens system described in Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, there has been a demand for an observation optical system that can be observed with a wider apparent field of view while having good performance.

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an observation optical system that can be observed with a wider apparent field of view while having good performance, and an optical device including this observation optical system.

Means for Solving the Problems

[0006] An observation optical system according to one aspect of the present disclosure includes a display element and an eyepiece lens disposed on the eye point side of the display element. The eyepiece lens includes at least one negative lens. When the half value of the longest diameter of the display area in the display element is H and the focal length of the eyepiece lens in a state where the diopter is -1 diopter is f, 0.35 < H / f < 0.6 (1) satisfies the conditional expression (1) represented by the above.

[0007] The eyepiece preferably includes at least one positive lens on the display element side of at least one negative lens. Furthermore, the eyepiece preferably includes at least one positive lens on the eye point side of at least one negative lens.

[0008] The eyepiece preferably includes at least three lenses, and during diopter adjustment, at least three lenses within the eyepiece move along the optical axis.

[0009] The eyepiece may be configured to contain five lenses.

[0010] The eyepiece preferably includes at least two lenses on the display element side of at least one negative lens. More preferably, the eyepiece includes at least two positive lenses on the display element side of at least one negative lens.

[0011] In this section, the negative lens with the strongest refractive power among the negative lenses included in the eyepiece will be referred to as the "first negative lens," the positive lens closest to the display element among the positive lenses included in the eyepiece will be referred to as the "display-side positive lens," and the positive lens closest to the eye point among the positive lenses included in the eyepiece will be referred to as the "EP-side positive lens."

[0012] When the paraxial radius of curvature of the display element side surface of the first negative lens is Rnf, and the paraxial radius of curvature of the eye point side surface of the first negative lens is Rnr, the observation optical system of the above embodiment is: 0 < (Rnr + Rnf) / (Rnr - Rnf) < 0.5 (2) It is preferable that the condition (2) expressed by is satisfied.

[0013] The eyepiece includes at least one positive lens on the display element side of the first negative lens, and when the paraxial radius of curvature of the display element side surface of the first negative lens is Rnf and the paraxial radius of curvature of the eye point side surface of the display-side positive lens is Ropr, the observation optical system in the above embodiment is: -3<(Rnf-Ropr) / (Rnf+Ropr)<0.2 (3) It is preferable to satisfy the conditional expression (3) represented by

[0014] The eyepiece lens includes at least one positive lens on the display element side of at least one negative lens. When the paraxial curvature radius of the surface on the display element side of the display-side positive lens is Ropf and the paraxial curvature radius of the surface on the eye point side of the display-side positive lens is Ropr, the observation optical system of the above aspect is -4.5 < (Ropr + Ropf) / (Ropr - Ropf) < 2.7 (4) It is preferable to satisfy the conditional expression (4) represented by

[0015] The eyepiece lens includes at least one positive lens on the eye point side of at least one negative lens. When the paraxial curvature radius of the surface on the display element side of the EP-side positive lens is Repf and the paraxial curvature radius of the surface on the eye point side of the EP-side positive lens is Repr, the observation optical system of the above aspect is -2.2 < (Repr + Repf) / (Repr - Repf) < 1.1 (5) It is preferable to satisfy the conditional expression (5) represented by

[0016] When the maximum value of the refractive index for the d-line of all the lenses included in the eyepiece lens is Nmax, the observation optical system of the above aspect is 1.7 < Nmax < 2.1 (6) It is preferable to satisfy the conditional expression (6) represented by

[0017] When the focal length of the first negative lens is fn, the observation optical system of the above aspect is -2.8 < f / fn < -0.8 (7) It is preferable to satisfy the conditional expression (7) represented by

[0018] The eyepiece lens includes at least one positive lens on the display element side of the first negative lens. When the combined focal length from the surface on the display element side of the display-side positive lens to the surface on the eye point side of the first negative lens in the state where the diopter is -1 diopter is fopn, the observation optical system of the above aspect is 0.1 < f / fopn < 1 (8) It is preferable to satisfy the conditional expression (8) represented by

[0019] When the combined focal length of all the lenses in the eyepiece lens arranged on the eye point side from the first negative lens in the state where the visibility is -1 diopter is fr, the observation optical system of the above aspect is 0.6 < f / fr < 2.2 (9) It is preferable to satisfy the conditional expression (9) represented by

[0020] The eyepiece lens includes at least one positive lens on the display element side from at least one negative lens. When the focal length of the positive lens on the display side is fop and the focal length of the first negative lens is fn, the observation optical system of the above aspect is -4.5 < fop / fn < -0.5 (10) It is preferable to satisfy the conditional expression (10) represented by

[0021] The eyepiece lens includes at least one positive lens on the display element side from at least one negative lens. When the focal length of the positive lens on the display side is fop and the combined focal length of all the lenses in the eyepiece lens arranged on the eye point side from the first negative lens in the state where the visibility is -1 diopter is fr, the observation optical system of the above aspect is 0.1 < fop / fr < 5.5 (11) It is preferable to satisfy the conditional expression (11) represented by

[0022] When the focal length of the first negative lens is fn and the combined focal length of all the lenses in the eyepiece lens arranged on the eye point side from the first negative lens in the state where the visibility is -1 diopter is fr, the observation optical system of the above aspect is -1 < fn / fr < -0.26 (12) It is preferable to satisfy the conditional expression (12) represented by

[0023] The eyepiece includes at least one positive lens on the eye point side of at least one negative lens, and when the paraxial radius of curvature of the display element side surface of the EP-side positive lens is Repf and the paraxial radius of curvature of the eye point side surface of the first negative lens is Rnr, the observation optical system of the above embodiment is 0.01<(Repf-Rnr) / (Repf+Rnr)<3.4 (13) It is preferable that the conditional expression (13) represented by is satisfied.

[0024] The eyepiece includes at least one positive lens on the display element side of at least one negative lens, and when the diopter is -1 diopter, the distance on the optical axis from the display element side surface of the display-side positive lens to the lens surface of the eyepiece closest to the eye point is DL, then the observation optical system of the above embodiment is, 0.75 <DL / f<2.2 (14) It is preferable that the conditional expression (14) represented by is satisfied.

[0025] The eyepiece includes at least one positive lens on the display element side of at least one negative lens, and DLopn is the distance along the optical axis from the display element side surface of the display-side positive lens to the eye point side surface of the first negative lens when the diopter is -1 diopter, and Tn is the distance along the optical axis from the display surface of the display element to the eye point side surface of the first negative lens when the diopter is -1 diopter, and if an optical element that does not have refractive power is arranged between the display surface of the display element and the eye point side surface of the first negative lens, then when Tn is calculated using the air equivalent length for the optical element, the observation optical system of the above embodiment is, 0.4 <DLopn / Tn<0.9 (15) It is preferable that the conditional expression (15) represented by is satisfied.

[0026] When the air distance on the optical axis between the lens adjacent to the display element side of the first negative lens and the first negative lens is Dgnf, and the focal length of the first negative lens is fn, the observation optical system of the above embodiment is: -0.9 <Dgnf / fn<-0.01 (16) It is preferable that the conditional expression (16) represented by is satisfied.

[0027] When Dgnr is the air distance on the optical axis between the lens adjacent to the eye point side of the first negative lens and the first negative lens, and fn is the focal length of the first negative lens, the observation optical system in the above embodiment is: -0.7 <Dgnr / fn<-0.01 (17) It is preferable that the conditional expression (17) represented by is satisfied.

[0028] An optical apparatus according to another aspect of the present disclosure comprises the observation optical system of the above aspect.

[0029] Furthermore, the terms "~consisting of" and "~consisting of" in this specification are intended to include, in addition to the listed components, lenses that have substantially no refractive power, as well as optical elements other than lenses such as apertures, filters, and cover glasses, and lens flanges, lens barrels, etc.

[0030] In this specification, "lens with positive refractive power" and "positive lens" are synonymous. "Lens with negative refractive power" and "negative lens" are synonymous. "Single lens" means a single lens that is not joined together. However, a composite aspherical lens (a lens in which a spherical lens and an aspherical film formed on the spherical lens are integrally constructed and function as a single aspherical lens as a whole) is not considered a joined lens and is treated as a single lens. For lenses including aspherical surfaces, the sign of refractive power, radius of curvature, and surface shape shall be those of the paraxial region unless otherwise specified. The sign of the radius of curvature shall be positive for a surface with a convex shape facing the display element side, and negative for a surface with a convex shape facing the eye point side.

[0031] The "focal length" used in the conditional formulas is the paraxial focal length. The values ​​used in the conditional formulas are relative to the d-line. Unless otherwise specified, the "distance on the optical axis" used in the conditional formulas is the geometric distance on the optical axis. The "d-line," "C-line," and "F-line" described herein are emission lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line as 656.27 nm (nanometers), and the wavelength of the F-line as 486.13 nm (nanometers). [Effects of the Invention]

[0032] According to this disclosure, it is possible to provide an observation optical system that has good performance while being able to observe with a wider apparent field of view, and an optical device equipped with this observation optical system. [Brief explanation of the drawing]

[0033] [Figure 1] This is a cross-sectional view corresponding to the observation optical system of Example 1, showing the configuration and light beam of an observation optical system according to one embodiment. [Figure 2] Figure 1 is a cross-sectional view illustrating the configuration of the eyepiece lens. [Figure 3] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 1. [Figure 4] This is a lateral aberration diagram of the observation optical system of Example 1. [Figure 5] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 2. [Figure 6] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 2. [Figure 7] This is a lateral aberration diagram of the observation optical system in Example 2. [Figure 8] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 3. [Figure 9] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 3. [Figure 10] This is a lateral aberration diagram of the observation optical system in Example 3. [Figure 11]This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 4. [Figure 12] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 4. [Figure 13] This is a lateral aberration diagram of the observation optical system in Example 4. [Figure 14] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 5. [Figure 15] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 5. [Figure 16] This is a lateral aberration diagram of the observation optical system in Example 5. [Figure 17] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 6. [Figure 18] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 6. [Figure 19] This is a lateral aberration diagram of the observation optical system of Example 6. [Figure 20] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 7. [Figure 21] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 7. [Figure 22] This is a lateral aberration diagram of the observation optical system in Example 7. [Figure 23] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 8. [Figure 24] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 8. [Figure 25] This is a lateral aberration diagram of the observation optical system in Example 8. [Figure 26] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 9. [Figure 27] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 9. [Figure 28] This is a lateral aberration diagram of the observation optical system in Example 9. [Figure 29] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 10. [Figure 30] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 10. [Figure 31] This is a lateral aberration diagram of the observation optical system in Example 10. [Figure 32] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 11. [Figure 33] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 11. [Figure 34] This is a lateral aberration diagram of the observation optical system in Example 11. [Figure 35] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 12. [Figure 36] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 12. [Figure 37] This is a lateral aberration diagram of the observation optical system in Example 12. [Figure 38] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 13. [Figure 39] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 13. [Figure 40] This is a lateral aberration diagram of the observation optical system in Example 13. [Figure 41] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 14. [Figure 42] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 14. [Figure 43] This is a lateral aberration diagram of the observation optical system of Example 14. [Figure 44] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 15. [Figure 45] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 15. [Figure 46] This is a lateral aberration diagram of the observation optical system in Example 15. [Figure 47] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 16. [Figure 48] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 16. [Figure 49] This is a lateral aberration diagram of the observation optical system of Example 16. [Figure 50] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 17. [Figure 51] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 17. [Figure 52] This is a lateral aberration diagram of the observation optical system in Example 17. [Figure 53] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 18. [Figure 54] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 18. [Figure 55] This is a lateral aberration diagram of the observation optical system of Example 18. [Figure 56] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 19. [Figure 57] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 19. [Figure 58] This is a lateral aberration diagram of the observation optical system in Example 19. [Figure 59] This is a cross-sectional view showing the configuration and light beam of the observation optical system in Example 20. [Figure 60] These are the spherical aberration diagram, astigmatism diagram, distortion diagram, and magnification chromatic aberration diagram of the observation optical system of Example 20. [Figure 61] This is a lateral aberration diagram of the observation optical system in Example 20. [Figure 62] This is a perspective view of the rear side of an optical device according to one embodiment. [Modes for carrying out the invention]

[0034] The embodiments of this disclosure will be described below with reference to the drawings.

[0035] Figure 1 shows the configuration of the observation optical system 5 and a cross-sectional view of the light beam according to one embodiment of the present disclosure. The example shown in Figure 1 corresponds to Embodiment 1 described later. In Figure 1, the light beam shows the on-axis light beam and the off-axis light beam corresponding to the maximum apparent field of view. In Figure 1, the left side is shown as the display element side and the right side as the eye point side. The eye point EP in Figure 1 does not show the shape but rather the position in the optical axis direction.

[0036] The observation optical system 5 comprises a display element 1 and an eyepiece lens 3 positioned on the eye point side of the display element 1. The display element 1 is an element that displays an image. The display element 1 includes a display area 1a on which the image is displayed and a cover member 1b made of an optical material that does not have refractive power. In the example in Figure 1, the display area 1a is located on the display element side of the cover member 1b. The display element 1 can be configured as an image display panel made of, for example, a liquid crystal display element or an organic electroluminescence (EL) display element. The display element 1 and the eyepiece lens 3 are positioned with a predetermined air gap between them. If the distance between the display element 1 and the eyepiece lens 3 is configured to change during diopter adjustment, providing the above air gap makes it easy to secure the distance for diopter adjustment.

[0037] The display element 1 is an example of an object to be observed. The eyepiece 3 is used to observe the image displayed in the display area 1a of the display element 1. In other words, the observation optical system 5 is configured to observe the image displayed on the display element 1 through the eyepiece 3.

[0038] In the example shown in Figure 1, an optical element 2 is positioned between the display element 1 and the eyepiece lens 3, and an optical element 4 is positioned between the eyepiece lens 3 and the eye point EP. Optical elements 2 and 4 are parallel plate-shaped members with no refractive power, and are intended to be protective cover glass or various filters. In the technology disclosed herein, a configuration is also possible in which at least one of optical elements 2 and 4 is omitted.

[0039] The eyepiece 3 of this embodiment is configured to include at least one negative lens. This configuration is advantageous for correcting chromatic aberration. Furthermore, it is preferable that the eyepiece 3 includes at least one positive lens on the display element side of the at least one negative lens. In this case, it is advantageous for correcting chromatic aberration while suppressing an increase in the diameter of the optical system. Also, it is preferable that the eyepiece 3 includes at least one positive lens on the eye point side of the at least one negative lens. In this case, it is advantageous for widening the apparent field of view while suppressing an increase in the diameter of the optical system.

[0040] Furthermore, if the eyepiece 3 includes multiple negative lenses, the phrase "on the display element side of at least one negative lens" above means on the display element side of any one of the multiple negative lenses included in the eyepiece 3. Similarly, the phrase "on the eye point side of at least one negative lens" above means on the eye point side of any one of the multiple negative lenses included in the eyepiece 3. The same applies to "on the display element side of at least one negative lens" and "on the eye point side of at least one negative lens" in the following explanation.

[0041] The eyepiece 3 preferably includes at least two lenses on the display element side of at least one negative lens. This is advantageous for correcting field curvature. More preferably, the eyepiece 3 includes at least two positive lenses on the display element side of at least one negative lens. In addition to the advantage of correcting field curvature mentioned above, this also provides the advantage of correcting chromatic aberration while suppressing an increase in the diameter of the optical system.

[0042] The eyepiece 3 may be configured to contain four or more lenses. This configuration is advantageous for effectively correcting overall aberrations. For example, as shown in Figure 1, the eyepiece 3 may be configured to contain five lenses. This configuration is advantageous for achieving a compact design by reducing the number of lenses while still effectively correcting overall aberrations.

[0043] As an example, the eyepiece 3 in Figure 1 consists of, in order from the display element side to the eye point side, a lens L1 with positive refractive power, a lens L2 with positive refractive power, a lens L3 with negative refractive power, a lens L4 with positive refractive power, and a lens L5 with positive refractive power.

[0044] In a configuration where the eyepiece 3 includes at least three lenses, the eyepiece 3 may be configured to move along the optical axis Z during diopter adjustment. This configuration is advantageous in suppressing aberration fluctuations during diopter adjustment. In the example in Figure 1, five lenses, L1 to L5, move integrally along the optical axis Z during diopter adjustment. The parentheses and horizontal double arrows below lenses L1 to L5 in Figure 1 indicate that these five lenses move integrally along the optical axis Z during diopter adjustment. In this specification, "moving integrally" means moving simultaneously in the same direction by the same amount.

[0045] Next, preferred and possible configurations of the observation optical system 5 will be described. In the following description, the negative lens with the strongest refractive power among the negative lenses included in the eyepiece 3 will be called the "first negative lens," the positive lens closest to the display element among the positive lenses included in the eyepiece 3 will be called the "display-side positive lens," and the positive lens closest to the eye point among the positive lenses included in the eyepiece 3 will be called the "EP-side positive lens." For example, in the example in Figure 1, lens L3 corresponds to the first negative lens, lens L1 corresponds to the display-side positive lens, and lens L5 corresponds to the EP-side positive lens. In the following description, the explanation concerning the "display-side positive lens" is for a configuration in which the eyepiece 3 includes at least one positive lens on the display element side of at least one negative lens. Also, in the following description, the explanation concerning the "EP-side positive lens" is for a configuration in which the eyepiece 3 includes at least one positive lens on the eye point side of at least one negative lens. Furthermore, the following explanation concerning "all lenses within the eyepiece 3 located on the eye point side of the first negative lens" refers to a configuration in which the eyepiece 3 includes at least one lens on the eye point side of the first negative lens.

[0046] When H is the half-value of the longest diameter of the display area 1a in the display element 1, and f is the focal length of the eyepiece lens 3 when the diopter is -1 diopter, it is preferable that the observation optical system 5 satisfies the following condition (1). By ensuring that the corresponding value of condition (1) does not fall below the lower limit, it is advantageous to widen the apparent field of view. By ensuring that the corresponding value of condition (1) does not exceed the upper limit, it is advantageous to suppress aberrations such as field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (1-1), and even more preferable that it satisfies the following condition (1-2). 0.35 <H / f<0.6 (1) 0.4 <H / f<0.55 (1-1) 0.417 <H / f<0.482 (1-2)

[0047] In this specification, "the longest diameter of the display area 1a in the display element 1" with respect to H means twice the distance between the point furthest from the optical axis Z in the radial direction and the optical axis Z in the display area 1a where the centroid coincides with the optical axis Z. For example, if the display area 1a is rectangular, H can be half the length of the diagonal of the display area 1a. Also, for example, if the display area 1a is a perfect circle, H can be the radius of the display area 1a, and if the display area 1a is an ellipse, H can be half the longest diameter (major axis) of the diameter of the display area 1a.

[0048] Furthermore, the display area 1a refers to the area where the image is actually displayed. For example, if the display element 1 has a display section with an aspect ratio of 4:3 in which multiple pixels are arranged, and displays an image with an aspect ratio of 3:2 in a part of the display section, then the display area 1a refers to the area where the image with an aspect ratio of 3:2 is displayed. Therefore, the diameter of the display element 1 and the longest diameter of the display area 1a do not necessarily coincide.

[0049] When the paraxial radius of curvature of the display element side surface of the first negative lens is Rnf and the paraxial radius of curvature of the eye point side surface of the first negative lens is Rnr, it is preferable that the observation optical system 5 satisfies the following condition (2). By ensuring that the corresponding value of condition (2) does not fall below the lower limit, the refraction of light rays on the eye point side surface of the first negative lens does not become too strong, which is advantageous in suppressing chromatic aberration. By ensuring that the corresponding value of condition (2) does not exceed the upper limit, the refraction of light rays on the display element side surface of the first negative lens does not become too strong, which is advantageous in suppressing field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (2-1), and even more preferable that it satisfies the following condition (2-2). 0 < (Rnr + Rnf) / (Rnr - Rnf) < 0.5 (2) 0.002<(Rnr+Rnf) / (Rnr-Rnf)<0.4 (2-1) 0.004<(Rnr+Rnf) / (Rnr-Rnf)<0.313 (2-2)

[0050] In a configuration where the eyepiece 3 includes at least one positive lens on the display element side of the first negative lens, it is preferable that the observation optical system 5 satisfies the following conditional equation (3). Here, Rnf is the radius of paraxial curvature of the display element side surface of the first negative lens. Ropr is the radius of paraxial curvature of the eye point side surface of the display-side positive lens. By ensuring that the corresponding value in conditional equation (3) does not fall below the lower limit, the refraction at the display element side surface of the first negative lens does not become too strong in relation to the refraction of off-axis rays at the eye point side surface of the display-side positive lens, thus suppressing overcorrection of chromatic aberration. By ensuring that the corresponding value in conditional equation (3) does not exceed the upper limit, the refraction at the display element side surface of the first negative lens does not become too weak in relation to the refraction of off-axis rays at the eye point side surface of the display-side positive lens, thus suppressing undercorrection of chromatic aberration. To obtain better characteristics, the observation optical system 5 is more preferably satisfied with the following condition (3-1), and even more preferably satisfied with the following condition (3-2). -3<(Rnf-Ropr) / (Rnf+Ropr)<0.2 (3) -0.3<(Rnf-Ropr) / (Rnf+Ropr)<0.15 (3-1) -0.05<(Rnf-Ropr) / (Rnf+Ropr)<0.07 (3-2)

[0051] When Ropf is the paraxial radius of curvature of the display element side surface of the display-side positive lens, and Ropr is the paraxial radius of curvature of the eye point side surface of the display-side positive lens, it is preferable that the observation optical system 5 satisfies the following condition (4). By ensuring that the corresponding value of condition (4) does not fall below the lower limit, the refraction of off-axis rays at the eye point side surface of the display-side positive lens does not become too strong, which is advantageous for correcting coma aberration. By ensuring that the corresponding value of condition (4) does not exceed the upper limit, the positive refractive power of the display element side surface of the display-side positive lens does not become too strong, or the negative refractive power of the display element side surface of the display-side positive lens does not become too weak, which is advantageous for suppressing barrel distortion. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (4-1), and even more preferable that it satisfies the following condition (4-2). -4.5<(Ropr+Ropf) / (Ropr-Ropf)<2.7 (4) -3.5<(Ropr+Ropf) / (Ropr-Ropf)<0.5 (4-1) -3.1<(Ropr+Ropf) / (Ropr-Ropf)<0 (4-2)

[0052] When Repf is the paraxial radius of curvature of the display element side surface of the EP-side positive lens, and Repr is the paraxial radius of curvature of the eye point side surface of the EP-side positive lens, it is preferable that the observation optical system 5 satisfies the following condition (5). By ensuring that the corresponding value of condition (5) does not fall below the lower limit, it is possible to suppress the shape of the portion of the eye point side surface of the EP-side positive lens through which off-axis rays pass, such that the distance from the eye point EP becomes longer, which is advantageous for miniaturization. By ensuring that the corresponding value of condition (5) does not exceed the upper limit, the positive refractive power of the display element side surface of the EP-side positive lens does not become too strong, or the negative refractive power of the display element side surface of the EP-side positive lens does not become too weak, which is advantageous for correcting field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (5-1), and even more preferable that it satisfies the following condition (5-2). -2.2<(Repr+Repf) / (Repr-Repf)<1.1 (5) -0.5<(Repr+Repf) / (Repr-Repf)<0.9 (5-1) 0.2<(Repr+Repf) / (Repr-Repf)<0.79 ​​(5-2)

[0053] When Nmax is the maximum refractive index of all lenses included in the eyepiece 3 with respect to the d line, it is preferable that the observation optical system 5 satisfies the following condition (6). By ensuring that the corresponding value in condition (6) does not fall below the lower limit, the Petzval sum can be suppressed from becoming large, which is advantageous for correcting field curvature. By ensuring that the corresponding value in condition (6) does not exceed the upper limit, it is advantageous for correcting chromatic aberration. Furthermore, by ensuring that the corresponding value in condition (6) does not exceed the upper limit, it is possible to improve productivity when processing lens materials. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (6-1), and even more preferable that it satisfies the following condition (6-2). 1.7 <Nmax<2.1 (6) 1.75 <Nmax<1.93 (6-1) 1.8 <Nmax<1.85 (6-2)

[0054] When the focal length of the eyepiece 3 is f and the focal length of the first negative lens is fn in a state of diopter of -1 diopter, it is preferable that the observation optical system 5 satisfies the following condition (7). Ensuring that the corresponding value of condition (7) does not fall below the lower limit is advantageous in suppressing aberrations caused by manufacturing errors. Ensuring that the corresponding value of condition (7) does not exceed the upper limit is advantageous in suppressing chromatic aberration. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (7-1), and even more preferable that it satisfies the following condition (7-2). -2.8 <f / fn<-0.8 (7) -2.2 <f / fn<-1.1 (7-1) -1.94 <f / fn<-1.4 (7-2)

[0055] In a configuration where the eyepiece 3 includes at least one positive lens on the display element side of the first negative lens, it is preferable that the observation optical system 5 satisfies the following conditional equation (8). Here, f is the focal length of the eyepiece 3 when the diopter is -1 diopter. Also, fopn is the combined focal length from the display element side surface of the display-side positive lens to the eye point side surface of the first negative lens when the diopter is -1 diopter. By ensuring that the corresponding value of conditional equation (8) does not fall below the lower limit, it is possible to suppress the weakening of the combined positive refractive power from the display-side positive lens to the first negative lens, thereby suppressing the strengthening of the negative refractive power of the first negative lens, which is advantageous for correcting various aberrations such as astigmatism and field curvature. By ensuring that the corresponding value of conditional equation (8) does not exceed the upper limit, it is possible to suppress the strengthening of the combined positive refractive power from the display-side positive lens to the first negative lens, which is advantageous for securing a wide apparent field of view and a high eye point. To obtain better characteristics, the observation optical system 5 is more preferably satisfied with the following condition (8-1), and even more preferably satisfied with the following condition (8-2). 0.1 <f / fopn<1 (8) 0.2 <f / fopn<0.75 (8-1) 0.3 <f / fopn<0.46 (8-2)

[0056] The observation optical system 5 preferably satisfies the following condition (9). Here, f is the focal length of the eyepiece 3 when the diopter is -1 diopter. Also, fr is the combined focal length of all lenses in the eyepiece 3 that are positioned closer to the eye point than the first negative lens when the diopter is -1 diopter. In the example in Figure 1, the combined focal length of lens L4 and lens L5 corresponds to fr. By ensuring that the corresponding value of condition (9) does not fall below the lower limit, it is possible to suppress the weakening of the positive combined refractive power of all lenses in the eyepiece 3 that are positioned closer to the eye point than the first negative lens, which is advantageous in suppressing astigmatism and spherical aberration. By ensuring that the corresponding value of condition (9) does not exceed the upper limit, it is possible to suppress the weakening of the refractive power of the eyepiece 3, which is advantageous in securing a wide apparent field of view. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (9-1), and even more preferable that it satisfies the following condition (9-2). 0.6 <f / fr<2.2 (9) 0.86 <f / fr<1.75 (9-1) 1 <f / fr<1.56 (9-2)

[0057] When the focal length of the display-side positive lens is fop and the focal length of the first negative lens is fn, it is preferable that the observation optical system 5 satisfies the following condition (10). By ensuring that the corresponding value of condition (10) does not fall below the lower limit, it is possible to suppress the negative refractive power of the first negative lens from becoming too strong, which is advantageous for suppressing astigmatism and correcting field curvature. By ensuring that the corresponding value of condition (10) does not exceed the upper limit, it is possible to suppress the negative refractive power of the first negative lens from becoming too weak, which is advantageous for miniaturization in the optical axis direction when trying to secure a wide apparent field of view. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (10-1), even more preferable that it satisfies the following condition (10-2), and even more preferable that it satisfies the following condition (10-3). -4.5 <fop / fn<-0.5 (10) -4.4 <fop / fn<-0.6 (10-1) -4.3 <fop / fn<-0.8 (10-2) -4.1 <fop / fn<-1 (10-3)

[0058] The observation optical system 5 preferably satisfies the following condition (11). Here, the focal length of the display-side positive lens is defined as fop. Also, when the diopter is -1 diopter, the combined focal length of all lenses in the eyepiece 3 positioned on the eye point side of the first negative lens is defined as fr. By ensuring that the corresponding value of condition (11) does not fall below the lower limit, the weakening of the refractive power of the EP-side positive lens can be suppressed, which is advantageous in suppressing astigmatism and spherical aberration. By ensuring that the corresponding value of condition (11) does not exceed the upper limit, the weakening of the positive refractive power of the display-side positive lens can be suppressed, which is advantageous in correcting astigmatism and field curvature, as the relatively excessive influence of the negative refractive power of the first negative lens can be suppressed. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (11-1), and even more preferable that it satisfies the following condition (11-2). 0.1 <fop / fr<5.5 (11) 0.5 <fop / fr<4.2 (11-1) 1.5 <fop / fr<3.33 (11-2)

[0059] When the focal length of the first negative lens is fn, and the combined focal length of all lenses in the eyepiece 3 positioned closer to the eye point than the first negative lens is fr, it is preferable that the observation optical system 5 satisfies the following condition (12). By ensuring that the corresponding value of condition (12) does not fall below the lower limit, it is possible to suppress the weakening of the negative refractive power of the first negative lens, which is advantageous for miniaturization in the optical axis direction when trying to secure a wide apparent field of view. By ensuring that the corresponding value of condition (12) does not exceed the upper limit, it is possible to suppress the weakening of the refractive power of the EP-side positive lens, which is advantageous for suppressing astigmatism and spherical aberration. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (12-1), and even more preferable that it satisfies the following condition (12-2). -1 <fn / fr<-0.26 (12) -0.95 <fn / fr<-0.34 (12-1) -0.87 <fn / fr<-0.57 (12-2)

[0060] When the paraxial radius of curvature of the display element side surface of the EP-side positive lens is Repf and the paraxial radius of curvature of the eye point side surface of the first negative lens is Rnr, it is preferable that the observation optical system 5 satisfies the following conditional equation (13). By ensuring that the corresponding value of conditional equation (13) does not fall below the lower limit, it is possible to suppress the excessive refraction of off-axis rays at the display element side surface of the EP-side positive lens in relation to the refraction of off-axis rays at the eye point side surface of the first negative lens, which is advantageous for correcting spherical aberration and securing a high eye point. By ensuring that the corresponding value of conditional equation (13) does not exceed the upper limit, it is possible to suppress the weakening of the refraction of off-axis rays at the display element side surface of the EP-side positive lens in relation to the refraction of off-axis rays at the eye point side surface of the first negative lens, which is advantageous for suppressing field curvature and astigmatism. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following conditional equation (13-1), and even more preferable that it satisfies the following conditional equation (13-2). 0.01<(Repf-Rnr) / (Repf+Rnr)<3.4 (13) 0.03<(Repf-Rnr) / (Repf+Rnr)<2 (13-1) 0.06<(Repf-Rnr) / (Repf+Rnr)<0.29 (13-2)

[0061] The observation optical system 5 preferably satisfies the following condition (14). Here, f is the focal length of the eyepiece 3 when the diopter is -1 diopter. DL is the distance on the optical axis from the display element side surface of the display-side positive lens to the lens surface of the eyepiece 3 closest to the eye point when the diopter is -1 diopter. As an example, Figure 2 shows the above distance DL. Figure 2 is a cross-sectional view illustrating the configuration of the eyepiece 3 in Figure 1. In Figure 2, the left side is the display element side and the right side is the eye point side. By ensuring that the corresponding value of condition (14) does not fall below the lower limit, the weakening of the refractive power of the eyepiece 3 can be suppressed, which is advantageous in securing a wide apparent field of view. By ensuring that the corresponding value of condition (14) does not exceed the upper limit, it is advantageous in shortening the overall length of the observation optical system 5. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (14-1), and even more preferable that it satisfies the following condition (14-2). 0.75 <DL / f<2.2 (14) 1.05 <DL / f<1.9 (14-1) 1.12 <DL / f<1.63 (14-2)

[0062] The observation optical system 5 preferably satisfies the following condition (15). Here, DLopn is defined as the distance along the optical axis from the display element side surface of the display-side positive lens to the eye point side surface of the first negative lens when the diopter is -1 diopter. As an example, Figure 2 shows the above distance DLopn. Also, Tn is defined as the distance along the optical axis from the display surface of the display element 1 to the eye point side surface of the first negative lens when the diopter is -1 diopter. However, if an optical element without refractive power is placed between the display surface of the display element 1 and the eye point side surface of the first negative lens, Tn will be calculated using the air equivalent length for that optical element without refractive power. By ensuring that the corresponding value of condition (15) does not fall below the lower limit, it is possible to suppress the abrupt change of light rays between the display surface of the display element 1 and the first negative lens, which is advantageous for correcting aberrations such as chromatic aberration and field curvature. By ensuring that the corresponding value in conditional equation (15) does not exceed the upper limit, it is advantageous to shorten the overall length of the observation optical system 5. To obtain better characteristics, it is more preferable that the observation optical system 5 satisfies the following conditional equation (15-1), and even more preferable that it satisfies the following conditional equation (15-2). 0.4 <DLopn / Tn<0.9 (15) 0.5 <DLopn / Tn<0.8 (15-1) 0.56 <DLopn / Tn<0.72 (15-2)

[0063] The calculation of Tn described above will now be explained. In the example in Figure 1, the position of the display surface of the display element 1 in the optical axis direction is the same as the position of the display area 1a. In the example in Figure 1, the optical elements that do not have refractive power and are located between the display surface of the display element 1 and the eye point side surface of the first negative lens are the cover member 1b and the optical element 2. Therefore, in the example in Figure 1, Tn is the sum of the air equivalent length of the cover member 1b of the display element 1 in the optical axis direction, the air distance between the display element 1 and the optical element 2, the air equivalent length of the optical element 2 in the optical axis direction, the air distance between the optical element 2 and the lens L1, and DLopn. The same consideration can be applied when calculating using the air equivalent length for optical elements that do not have refractive power in the following explanation.

[0064] The observation optical system 5 preferably satisfies the following condition (16). Here, Dgnf is the air distance on the optical axis between the lens adjacent to the display element side of the first negative lens and the first negative lens. Also, fn is the focal length of the first negative lens. In the example in Figure 1, lens L2 corresponds to the lens adjacent to the display element side of the first negative lens. As an example, Figure 2 shows the above air distance Dgnf. By ensuring that the corresponding value of condition (16) does not fall below the lower limit, it is advantageous for correcting distortion aberration. By ensuring that the corresponding value of condition (16) does not exceed the upper limit, it is possible to suppress overcorrection of distortion aberration. To obtain better characteristics, it is more preferable for the observation optical system 5 to satisfy the following condition (16-1), and even more preferable to satisfy the following condition (16-2). -0.9 <Dgnf / fn<-0.01 (16) -0.7 <Dgnf / fn<-0.05 (16-1) -0.46 <Dgnf / fn<-0.11 (16-2)

[0065] The observation optical system 5 preferably satisfies the following condition (17). Here, Dgnr is the air distance on the optical axis between the lens adjacent to the eye point side of the first negative lens and the first negative lens. The focal length of the first negative lens is fn. In the example in Figure 1, lens L4 corresponds to the lens adjacent to the eye point side of the first negative lens. As an example, Figure 2 shows the above air distance Dgnr. By ensuring that the corresponding value of condition (17) does not fall below the lower limit, it is advantageous for miniaturization. By ensuring that the corresponding value of condition (17) does not exceed the upper limit, it is advantageous for correcting field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (17-1), and even more preferable that it satisfies the following condition (17-2). -0.7 <Dgnr / fn<-0.01 (17) -0.4 <Dgnr / fn<-0.02 (17-1) -0.27 <Dgnr / fn<-0.04 (17-2)

[0066] When H is the half-value of the longest diameter of the display area 1a in the display element 1, and fn is the focal length of the first negative lens, it is preferable that the observation optical system 5 satisfies the following conditional equation (18). By ensuring that the corresponding value of conditional equation (18) does not fall below the lower limit, it is possible to suppress the negative refractive power of the first negative lens from becoming too strong, which is advantageous for correcting chromatic aberration and field curvature. By ensuring that the corresponding value of conditional equation (18) does not exceed the upper limit, it is possible to suppress the negative refractive power of the first negative lens from becoming too weak, and to suppress the rebound of light rays from the first negative lens to the EP-side positive lens from becoming too strong. This is advantageous for miniaturization in the optical axis direction when trying to secure a wide apparent field of view. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following conditional equation (18-1), and even more preferable that it satisfies the following conditional equation (18-2). -1.05 <H / fn<-0.4 (18) -0.95 <H / fn<-0.55 (18-1) -0.86 <H / fn<-0.64 (18-2)

[0067] The observation optical system 5 preferably satisfies the following condition (19). Here, H is defined as half the longest diameter of the display area 1a in the display element 1. Also, fr is defined as the combined focal length of all lenses in the eyepiece 3 positioned on the eye point side of the first negative lens when the diopter is -1 diopter. By ensuring that the corresponding value of condition (19) does not fall below the lower limit, it is possible to suppress the weakening of the positive combined refractive power of all lenses in the eyepiece 3 positioned on the eye point side of the first negative lens, which is advantageous in suppressing astigmatism and spherical aberration. By ensuring that the corresponding value of condition (19) does not exceed the upper limit, it is advantageous in suppressing aberrations such as field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (19-1), and even more preferable that it satisfies the following condition (19-2). 0.22 <H / fr<0.92 (19) 0.3 <H / fr<0.8 (19-1) 0.39 <H / fr<0.71 (19-2)

[0068] When the focal length of the eyepiece 3 is f and the focal length of the display-side positive lens is fop at a diopter of -1 diopter, it is preferable that the observation optical system 5 satisfies the following condition (20). By ensuring that the corresponding value of condition (20) does not fall below the lower limit, it is possible to suppress the weakening of the positive refractive power of the display-side positive lens, thereby suppressing the excessive influence of the negative refractive power of the first negative lens, which is advantageous for correcting astigmatism and field curvature. By ensuring that the corresponding value of condition (20) does not exceed the upper limit, it is possible to suppress the weakening of the refractive power of the eyepiece 3, which is advantageous for securing a wide apparent field of view. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (20-1), and even more preferable that it satisfies the following condition (20-2). 0.22 <f / fop<1.95 (20) 0.33 <f / fop<1.73 (20-1) 0.44 <f / fop<0.75 (20-2)

[0069] The observation optical system 5 preferably satisfies the following condition (21). Here, Dopn is the distance along the optical axis from the eye point side surface of the display-side positive lens to the display element side surface of the first negative lens when the diopter is -1 diopter. Also, Dn is the thickness of the first negative lens along the optical axis. As an example, Figure 2 shows the above distance Dopn and thickness Dn. By ensuring that the corresponding value of condition (21) does not fall below the lower limit, it becomes easier to secure a distance to increase the optical beam diameter, which is advantageous for widening the apparent field of view. By ensuring that the corresponding value of condition (21) does not exceed the upper limit, it becomes easier to secure a sufficient thickness of the first negative lens, which is advantageous for correcting chromatic aberration. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (21-1), and even more preferable that it satisfies the following condition (21-2). 0.5 <Dopn / Dn<7 (21) 2.1 <Dopn / Dn<5.9 (21-1) 3.2 <Dopn / Dn<4 (21-2)

[0070] The observation optical system 5 preferably satisfies the following condition (22). Here, Dopn is the distance along the optical axis from the eye-point side surface of the display-side positive lens to the display element side surface of the first negative lens when the diopter is -1 diopter. Also, TTL is the distance along the optical axis from the display surface of the display element 1 to the lens surface of the eyepiece 3 closest to the eye point when the diopter is -1 diopter. However, if an optical element without refractive power is placed between the display surface of the display element 1 and the lens surface of the eyepiece 3 closest to the eye point, TTL will be calculated using the air equivalent length for that optical element without refractive power. By ensuring that the corresponding value of condition (22) does not fall below the lower limit, it is possible to suppress the weakening of the refractive power of the eyepiece 3, which is advantageous in securing a wide apparent field of view. By ensuring that the corresponding value in conditional equation (22) does not exceed the upper limit, an appropriate overall length can be secured for bending and converging the upward-angled light rays, thereby preventing the angle change of the light rays from becoming too abrupt, which is advantageous for correcting aberrations such as chromatic aberration and field curvature. To obtain even better characteristics, it is more preferable for the observation optical system 5 to satisfy the following conditional equation (22-1), even more preferable for it to satisfy the following conditional equation (22-2), and even more preferable for it to satisfy the following conditional equation (22-3). 0.04 <Dopn / TTL<0.6 (22) 0.041 <Dopn / TTL<0.5 (22-1) 0.043 <Dopn / TTL<0.42 (22-2) 0.18 <Dopn / TTL<0.42 (22-3)

[0071] When H is the half-value of the longest diameter of the display area 1a in the display element 1, and fop is the focal length of the display-side positive lens, it is preferable that the observation optical system 5 satisfies the following conditional equation (23). By ensuring that the corresponding value of conditional equation (23) does not fall below the lower limit, it is possible to suppress the weakening of the positive refractive power of the display-side positive lens, thereby suppressing the excessive influence of the negative refractive power of the first negative lens, which is advantageous for correcting astigmatism and field curvature. By ensuring that the corresponding value of conditional equation (23) does not exceed the upper limit, it is advantageous for suppressing aberrations such as field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following conditional equation (23-1), and even more preferable that it satisfies the following conditional equation (23-2). 0.05 <H / fop<0.9 (23) 0.15 <H / fop<0.79 (23-1) 0.19 <H / fop<0.33 (23-2)

[0072] The observation optical system 5 preferably satisfies the following condition (24). Here, H is defined as half the longest diameter of the display area 1a in the display element 1. Also, Tep is defined as the distance on the optical axis from the display surface of the display element 1 to the eye point side surface of the EP-side positive lens when the diopter is -1 diopter. However, if an optical element without refractive power is placed between the display surface of the display element 1 and the eye point side surface of the EP-side positive lens, Tep will be calculated using the air equivalent length for that optical element without refractive power. By ensuring that the corresponding value of condition (24) does not fall below the lower limit, the weakening of the refractive power of the eyepiece lens 3 can be suppressed, which is advantageous in securing a wide apparent field of view. By ensuring that the corresponding value of condition (24) does not exceed the upper limit, it is advantageous in suppressing aberrations such as field curvature. To obtain even better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (24-1), and even more preferable that it satisfies the following condition (24-2). 0.15 <H / Tep<0.5 (24) 0.18 <H / Tep<0.41 (24-1) 0.23 <H / Tep<0.29 (24-2)

[0073] The observation optical system 5 preferably satisfies the following condition (25). Here, f is the focal length of the eyepiece 3 when the diopter is -1 diopter. Also, Doop is the distance on the optical axis from the display surface of the display element 1 to the display element side surface of the display-side positive lens when the diopter is -1 diopter. However, if an optical element that does not have refractive power is placed between the display surface of the display element 1 and the display element side surface of the display-side positive lens, Doop will be calculated using the air equivalent length for that optical element that does not have refractive power. By ensuring that the corresponding value of condition (25) does not fall below the lower limit, it is advantageous to secure a sufficient gap for diopter adjustment between the display element 1 and the eyepiece 3. By ensuring that the corresponding value of condition (25) does not exceed the upper limit, it is advantageous to shorten the overall length of the observation optical system 5. To obtain better characteristics, it is more preferable that the observation optical system 5 satisfies the following condition (25-1), and even more preferable that it satisfies the following condition (25-2). 0.2 <Doop / f<0.7 (25) 0.3 <Doop / f<0.6 (25-1) 0.38 <Doop / f<0.49 (25-2)

[0074] The first negative lens is preferably a single lens that is not joined to another lens. Configuring the object-side and image-side surfaces of the first negative lens to be in contact with air is advantageous for correcting distortion.

[0075] The lenses included in eyepiece 3 may all be configured as unbonded single lenses. This allows for greater design flexibility, which is advantageous for correcting various aberrations.

[0076] The eyepiece 3 may be configured to include an aspherical lens. Including an aspherical lens is advantageous for good aberration correction.

[0077] As shown in Figure 1, the eyepiece 3 may be configured to consist of four positive lenses and one negative lens. When the eyepiece 3 is configured to consist of five lenses in this way, it is particularly advantageous for miniaturization. Specifically, for example, the eyepiece 3 may be configured to consist of a positive lens, a positive lens, a negative lens, a positive lens, and a positive lens in order from the display element side to the eye point side.

[0078] Note that the example shown in Figure 1 is an example of the observation optical system 5 of this disclosure. The eyepiece lens 3 of the observation optical system 5 of this disclosure can also be configured differently from the example shown in Figure 1. For example, the eyepiece lens 3 may be configured to consist of three positive lenses and two negative lenses. When the eyepiece lens 3 is configured to consist of five lenses in this way, it can be a configuration that is particularly advantageous in terms of chromatic aberration. Specifically, for example, the eyepiece lens 3 may be configured to consist of a positive lens, a negative lens, a positive lens, a positive lens, and a negative lens in order from the display element side to the eye point side. Alternatively, the eyepiece lens 3 may be configured to consist of a negative lens, a positive lens, a positive lens, a negative lens, and a positive lens in order from the display element side to the eye point side.

[0079] The number of lenses included in the eyepiece 3 may differ from the example in Figure 1. For example, the eyepiece 3 may be configured to include four lenses. This configuration is advantageous for weight reduction. For example, the eyepiece 3 may be configured to consist of two positive lenses and two negative lenses. In this case, the eyepiece 3 may be configured to consist of a negative lens, a positive lens, a negative lens, and a positive lens in order from the display element side to the eye point side. Alternatively, the eyepiece 3 may be configured to consist of three positive lenses and one negative lens. In this case, the eyepiece 3 may be configured to consist of a positive lens, a positive lens, a negative lens, and a positive lens in order from the display element side to the eye point side.

[0080] Alternatively, the eyepiece 3 may be configured to contain six lenses. This configuration is advantageous for correcting various aberrations. For example, the eyepiece 3 may be configured to consist of four positive lenses and two negative lenses. In this case, the eyepiece 3 may be configured to consist of a positive lens, a negative lens, a positive lens, a negative lens, a positive lens, and a positive lens, in order from the display element side to the eye point side. Alternatively, the eyepiece 3 may be configured to consist of three positive lenses and three negative lenses. In this case, the eyepiece 3 may be configured to consist of a positive lens, a negative lens, a positive lens, a negative lens, a negative lens, and a positive lens, in order from the display element side to the eye point side.

[0081] The display element 1 may be configured to move along the optical axis Z during diopter adjustment. This configuration is advantageous for shortening the overall length of the observation optical system 5. For example, the display element 1 may move during diopter adjustment while the eyepiece 3 remains fixed. Alternatively, the display element 1 and the lens closest to the display element within the eyepiece 3 may move together during diopter adjustment.

[0082] The system may be configured so that at least one air gap changes between the display element 1 and the display element side surface of the first negative lens during diopter adjustment. This configuration is advantageous in suppressing aberration fluctuations during diopter adjustment.

[0083] If the eyepiece 3 includes multiple negative lenses, the negative lens closest to the display element may be configured as the first negative lens, or the second negative lens from the display element side may be configured as the first negative lens.

[0084] The preferred and possible configurations described above, including the configurations related to the conditional expressions, can be combined in any way and are preferably selected as appropriate according to the required specifications. It should be noted that the preferred conditional expressions that the observation optical system 5 of this disclosure satisfies are not limited to those described in formula form, but include all conditional expressions obtained by arbitrarily combining lower and upper limits from the preferred, more preferred, and even more preferred conditional expressions.

[0085] As an example, a preferred embodiment of the present disclosure is an observation optical system 5 comprising a display element 1 and an eyepiece lens 3 positioned on the eye point side of the display element 1, wherein the eyepiece lens 3 includes at least one negative lens and satisfies the above condition (1).

[0086] In observation optical systems for viewfinders of digital cameras and the like, the increasing pixel count of display elements has recently led to a demand for a wider apparent field of view and higher resolution. However, attempting to obtain a wider apparent field of view increases the amount of various aberrations such as field curvature and chromatic aberration, making it difficult to achieve both a wider apparent field of view and high resolution. Therefore, by adopting the above-described preferred embodiment, it becomes easier to realize an observation optical system that allows observation with a wider apparent field of view while suppressing field curvature and chromatic aberration.

[0087] Next, embodiments of the observation optical system 5 of this disclosure will be described with reference to the drawings. Note that the reference numerals assigned to the components in the cross-sectional views of each embodiment are used independently for each embodiment to avoid complexity in the explanation and drawings due to the increasing number of digits in the reference numerals. Therefore, even if the same reference numerals are assigned to the drawings of different embodiments, they do not necessarily represent the same configuration. Examples 1-5, 9-17, and 19-20 below are embodiments of this disclosure, while Examples 6-8 and 18 are reference examples of this disclosure.

[0088] [Example 1] The configuration of the observation optical system 5 of Example 1 is shown in Figure 1, and its illustration method and configuration are as described above, so some redundant explanations will be omitted here. The observation optical system 5 of Example 1 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0089] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L2 is a positive lens with a biconvex shape. Lens L3 is a negative lens with a biconcave shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L5 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0090] Table 1 shows the basic lens data for observation optical system 5 of Example 1, Table 2 shows the specifications, Table 3 shows the variable plane spacing, and Table 4 shows the aspherical coefficient.

[0091] Table 1 is described as follows: The Sn column shows the surface number of each surface, with the surface on which the display area 1a of the display element 1 is located being designated as the first surface, and the number increasing by one as you move toward the eye point. In the optical axis direction, the position of the first surface corresponds to the position of the display surface. The R column shows the radius of curvature of each surface. The D column shows the interplanar spacing on the optical axis between each surface and the surface adjacent to it on the eye point side. The Nd column shows the refractive index of each component with respect to the d line. The νd column shows the Abbe number of each component with respect to the d line.

[0092] Table 1 also lists the display element 1, optical element 2, optical element 4, and eye point EP. In the Sn column for the surface corresponding to eye point EP, the surface number and the phrase (EP) are listed. Aspherical surface numbers are marked with an asterisk (*), and the column for the radius of curvature of the aspherical surface lists the value of the paraxial radius of curvature. In Table 1, the sign of the radius of curvature of a surface with a convex shape facing the display element is positive, and the sign of the radius of curvature of a surface with a convex shape facing the eye point is negative. For the variable surface spacing during diopter adjustment, the symbol DD[ ] is used, and the surface number on the display element side of this spacing is written in column D inside the brackets.

[0093] Table 2 shows the focal length f of the eyepiece 3 for each diopter, and the apparent field of view at the entire angle of view. In the diopter column, the unit diopter is denoted as "dpt," and this notation is also used in Table 3. In the apparent field of view column, (°) indicates that the unit is degrees. Table 2 also shows the half-value H of the longest diameter of the display area 1a in the display element 1.

[0094] Table 3 shows the values ​​of the variable plane spacing for each diopter. The observation optical system 5 of Example 1 allows for diopter adjustment in the range of -4.5 diopters to +2.5 diopters.

[0095] Table 4 shows the aspherical surface number in the Sn row, and the aspherical coefficient values ​​for each aspherical surface in the KA and Am rows. m is an integer greater than or equal to 3 and varies depending on the surface. For example, for the 5th surface in Example 1, m = 3, 4, 5, ... 16. The "E±n" (n: integer) values ​​for the aspherical coefficients in Table 4 are expressed as "×10 ±n This means "[...]. KA and Am are the aspheric coefficients in the aspheric equation expressed by the following formula. Zd = C × h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspherical depth (length of the perpendicular line drawn from a point on the aspherical surface at height h to a plane perpendicular to the optical axis Z to which the aspherical surface tangent is located). h: Height (distance from the optical axis Z to the lens surface) C: Reciprocal of the radius of paraxial curvature KA, Am: Aspherical coefficients Therefore, the Σ in aspherical formulas represents the summation with respect to m.

[0096] In the data in each table, degrees are used as the unit for angles and millimeters (mm) as the unit for lengths. However, since optical systems can be used with proportional magnification or reduction, other appropriate units can also be used. Furthermore, the values ​​in the tables below are rounded to a predetermined number of decimal places.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] [Table 4]

[0101] Figures 3 and 4 show the aberration diagrams for each aspect of the observation optical system 5 of Example 1 at a diopter of -0.98 diopters. In Figure 3, from left to right, the diagrams show spherical aberration, astigmatism, distortion, and chromatic aberration. In the spherical aberration diagram, the aberrations along the d, C, and F lines are shown as solid, long dashed, and short dashed lines, respectively. In the astigmatism diagram, the aberration along the d line in the sagittal direction is shown as a solid line, and the aberration along the d line in the tangential direction is shown as a short dashed line. In the distortion diagram, the aberration along the d line is shown as a solid line. In the chromatic aberration diagram, the aberrations along the C and F lines are shown as long dashed and short dashed lines, respectively. The unit "dpt" on the horizontal axis of the spherical aberration and astigmatism diagrams represents diopters. The unit "min" on the horizontal axis of the chromatic aberration diagram represents minutes of angle. In the spherical aberration diagram, the diameter of the eye point EP is shown after "Φ=" in millimeters (mm). In other aberration diagrams, the apparent field of view value at half the field of view is shown after "ω=".

[0102] In Figure 4, the tangential lateral aberration is shown in the left column and the sagittal lateral aberration is shown in the right column for each apparent field of view. In Figure 4, the aberrations at the d, C, and F lines are shown as solid, long dashed, and short dashed lines, respectively. In Figure 4, the apparent field of view value at half the field of view is shown after "ω=".

[0103] The symbols, meanings, methods of description, and methods of illustration for each data point in Example 1 described above are the same in the following examples unless otherwise specified, so redundant explanations will be omitted below.

[0104] [Example 2] Figure 5 shows the configuration and light beam of the observation optical system 5 of Example 2. The observation optical system 5 of Example 2 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4. Note that in Figure 5, the reference numerals for the display area 1a and the cover member 1b are omitted, and this is also the case in the figures showing the configurations of Example 3 and later.

[0105] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L2 is a positive lens with a biconvex shape. Lens L3 is a negative lens with a biconcave shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L5 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0106] For the observation optical system 5 of Example 2, the basic lens data is shown in Table 5, the specifications in Table 6, the variable plane spacing in Table 7, the aspherical coefficient in Table 8, and the aberration diagrams for each state when the diopter is -0.98 diopters are shown in Figures 6 and 7.

[0107] [Table 5]

[0108] [Table 6]

[0109] [Table 7]

[0110] [Table 8]

[0111] [Example 3] Figure 8 shows the configuration and light beam of the observation optical system 5 of Example 3. The observation optical system 5 of Example 3 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0112] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L2 is a positive lens with a biconvex shape. Lens L3 is a negative lens with a biconcave shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L5 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0113] For the observation optical system 5 of Example 3, the basic lens data is shown in Table 9, the specifications in Table 10, the variable plane spacing in Table 11, the aspherical coefficient in Table 12, and the aberration diagrams for each state when the diopter is -0.98 diopters are shown in Figures 9 and 10.

[0114] [Table 9]

[0115] [Table 10]

[0116] [Table 11]

[0117] [Table 12]

[0118] [Example 4] Figure 11 shows the configuration and light beam of the observation optical system 5 of Example 4. The observation optical system 5 of Example 4 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0119] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L2 is a positive lens with a biconvex shape. Lens L3 is a negative lens with a biconcave shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L5 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0120] For the observation optical system 5 of Example 4, the basic lens data is shown in Table 13, the specifications in Table 14, the variable plane spacing in Table 15, the aspherical coefficient in Table 16, and the aberration diagrams for each state when the diopter is -0.98 diopters are shown in Figures 12 and 13.

[0121] [Table 13]

[0122] [Table 14]

[0123] [Table 15]

[0124] [Table 16]

[0125] [Example 5] Figure 14 shows the configuration and light beam of the observation optical system 5 of Example 5. The observation optical system 5 of Example 5 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0126] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped positive lens with its convex surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens. Lens L3 is a biconcave negative lens in the paraxial region. Lens L4 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L5 is a biconvex positive lens in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the four lenses L2 to L5 move integrally along the optical axis Z, while lens L1, display element 1, optical element 2, and optical element 4 are fixed together.

[0127] For the observation optical system 5 of Example 5, the basic lens data is shown in Table 17, the specifications in Table 18, the variable plane spacing in Table 19, the aspherical coefficient in Table 20, and the aberration diagrams for each state when the diopter is -0.98 diopters are shown in Figures 15 and 16.

[0128] [Table 17]

[0129] [Table 18]

[0130] [Table 19]

[0131] [Table 20]

[0132] [Example 6] Figure 17 shows the configuration and light beam of the observation optical system 5 of Example 6. The observation optical system 5 of Example 6 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0133] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a negative lens with a biconcave shape in the paraxial region. Lens L3 is a positive lens with a biconvex shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape in the paraxial region with the concave surface facing the display element side. Lens L5 is a negative lens with a meniscus shape in the paraxial region with the concave surface facing the display element side. All of lenses L1 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0134] For the observation optical system 5 of Example 6, the basic lens data is shown in Table 21, the specifications in Table 22, the variable plane spacing in Table 23, the aspherical coefficient in Table 24, and the aberration diagrams for each state when the diopter is -0.98 diopters are shown in Figures 18 and 19.

[0135] [Table 21]

[0136] [Table 22]

[0137] [Table 23]

[0138] [Table 24]

[0139] [Example 7] Figure 20 shows the configuration and light beam of the observation optical system 5 of Example 7. The observation optical system 5 of Example 7 comprises, in order from the display element side to the eye point side, a display element 1, an optical member 2, and an eyepiece lens 3.

[0140] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a negative lens with a biconcave shape in the paraxial region. Lens L3 is a positive lens with a biconvex shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape in the paraxial region with the concave surface facing the display element side. Lens L5 is a negative lens with a meniscus shape in the paraxial region with the concave surface facing the display element side. All of lenses L1 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the three lenses L1 to L3 move integrally along the optical axis Z, while the two lenses L4 to L5, the display element 1, and the optical component 2 are fixed together.

[0141] For the observation optical system 5 of Example 7, the basic lens data is shown in Table 25, the specifications in Table 26, the variable plane spacing in Table 27, the aspherical coefficient in Table 28, and the aberration diagrams for each state when the diopter is -0.98 diopters are shown in Figures 21 and 22.

[0142] [Table 25]

[0143] [Table 26]

[0144] [Table 27]

[0145] [Table 28]

[0146] [Example 8] Figure 23 shows the configuration and light beam of the observation optical system 5 of Example 8. The observation optical system 5 of Example 8 comprises, in order from the display element side to the eye point side, a display element 1, an optical member 2, and an eyepiece lens 3.

[0147] The eyepiece 3 consists of four lenses, L1 to L4, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped negative lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens in the paraxial region. Lens L3 is a biconcave negative lens in the paraxial region. Lens L4 is a biconvex positive lens in the paraxial region. All of lenses L1 to L4 are aspherical lenses. All of lenses L1 to L4 are single lenses. During diopter adjustment, the display element 1 and the optical component 2 move integrally along the optical axis Z, while the four lenses L1 to L4 remain fixed.

[0148] For the observation optical system 5 of Example 8, the basic lens data is shown in Table 29, the specifications in Table 30, the variable plane spacing in Table 31, the aspherical coefficient in Table 32, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 24 and 25.

[0149] [Table 29]

[0150] [Table 30]

[0151] [Table 31]

[0152] [Table 32]

[0153] [Example 9] Figure 26 shows the configuration and light beam of the observation optical system 5 of Example 9. The observation optical system 5 of Example 9 comprises, in order from the display element side to the eye point side, a display element 1, an optical member 2, and an eyepiece lens 3.

[0154] The eyepiece 3 consists of four lenses, L1 to L4, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens in the paraxial region. Lens L3 is a biconcave negative lens in the paraxial region. Lens L4 is a biconvex positive lens in the paraxial region. All of lenses L1 to L4 are aspherical lenses. All of lenses L1 to L4 are single lenses. During diopter adjustment, the display element 1 and the optical component 2 move integrally along the optical axis Z, while the four lenses L1 to L4 remain fixed.

[0155] For observation optical system 5 of Example 9, the basic lens data is shown in Table 33, the specifications in Table 34, the variable plane spacing in Table 35, the aspherical coefficient in Table 36, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 27 and 28.

[0156] [Table 33]

[0157] [Table 34]

[0158] [Table 35]

[0159] [Table 36]

[0160] [Example 10] The configuration of the observation optical system 5 in Example 10 and the light beam are shown in FIG. 29. The observation optical system 5 in Example 10 includes a display element 1 and an eyepiece lens 3 in order from the display element side to the eye point side.

[0161] The eyepiece lens 3 consists of five lenses, namely, lenses L1 to L5, in order from the display element side to the eye point side. The lens L1 is a plano-concave negative lens with a concave surface facing the display element side. The lens L2 is a meniscus positive lens with a concave surface facing the display element side in the paraxial region. The lens L3 is a biconvex positive lens in the paraxial region. The lens L4 is a biconcave negative lens in the paraxial region. The lens L5 is a biconvex positive lens in the paraxial region. The lens L1 is a spherical lens, and the lenses L2 to L5 are aspherical lenses. All of the lenses L1 to L5 are single lenses. During diopter adjustment, the display element 1 and the lens L1 move integrally along the optical axis Z, and the four lenses L2 to L5 are fixed.

[0162] For the observation optical system 5 in Example 10, the basic lens data is shown in Table 37, the specifications are shown in Table 38, the variable surface intervals are shown in Table 39, the aspherical coefficients are shown in Table 40, and each aberration diagram in the state where the diopter is -1.00 diopter is shown in FIGS. 30 and 31.

[0163]

Table 37

[0164] 7]

Table 38

[0165]

Table 39

[0166] [Table 40]

[0167] [Example 11] Figure 32 shows the configuration and light beam of the observation optical system 5 of Example 11. The observation optical system 5 of Example 11 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0168] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L2 is a positive lens with a biconvex shape. Lens L3 is a negative lens with a biconcave shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L5 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0169] For the observation optical system 5 of Example 11, the basic lens data is shown in Table 41, the specifications in Table 42, the variable plane spacing in Table 43, the aspherical coefficient in Table 44, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 33 and 34.

[0170] [Table 41]

[0171] [Table 42]

[0172] [Table 43]

[0173]

Table 44

[0174] [Example 12] The configuration of the observation optical system 5 of Example 12 and the light beam are shown in FIG. 35. The observation optical system 5 of Example 12 includes, in order from the display element side to the eye point side, a display element 1, an optical member 2, an eyepiece lens 3, and an optical member 4.

[0175] The eyepiece lens 3 consists of five lenses, namely, lenses L1 to L5, in order from the display element side to the eye point side. The lens L1 is a meniscus-shaped positive lens with a concave surface facing the display element side in the paraxial region. The lens L2 is a biconvex positive lens. The lens L3 is a negative lens with a biconcave shape in the paraxial region. The lens L4 is a meniscus-shaped positive lens with a concave surface facing the display element side in the paraxial region. The lens L5 is a meniscus-shaped positive lens with a convex surface facing the display element side in the paraxial region. The lens L2 is a spherical lens, and the lenses L1 and L3 to L5 are aspherical lenses. All of the lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, and the display element 1, the optical member 2, and the optical member 4 are fixed.

[0176] For the observation optical system 5 of Example 12, the basic lens data is shown in Table 45, the specifications are shown in Table 46, the variable surface intervals are shown in Table 47, the aspherical coefficients are shown in Table 48, and the aberration diagrams in the state where the diopter is -1.00 diopter are shown in FIGS. 36 and 37.

[0177]

Table 46

[0178]

Table 46

[0179] [Table 47]

[0180] [Table 48]

[0181] [Example 13] Figure 38 shows the configuration and light beam of the observation optical system 5 of Example 13. The observation optical system 5 of Example 13 comprises, in order from the display element side to the eye point side, a display element 1, an optical member 2, and an eyepiece lens 3.

[0182] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens. Lens L3 is a biconcave negative lens in the paraxial region. Lens L4 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L5 is a biconvex positive lens in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the display element 1 and optical component 2 move integrally along the optical axis Z, while the five lenses L1 to L5 remain fixed.

[0183] For the observation optical system 5 of Example 13, the basic lens data is shown in Table 49, the specifications in Table 50, the variable plane spacing in Table 51, the aspherical coefficient in Table 52, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 39 and 40.

[0184] [Table 49]

[0185] [Table 50]

[0186] [Table 51]

[0187] [Table 52]

[0188] [Example 14] Figure 41 shows the configuration and light beam of the observation optical system 5 of Example 14. The observation optical system 5 of Example 14 comprises a display element 1 and an eyepiece lens 3, arranged in order from the display element side to the eye point side.

[0189] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped negative lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens in the paraxial region. Lens L3 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L4 is a biconcave negative lens in the paraxial region. Lens L5 is a biconvex positive lens in the paraxial region. All of lenses L1 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the display element 1 and lens L1 move together along the optical axis Z, while the four lenses L2 to L5 remain fixed.

[0190] For the observation optical system 5 of Example 14, the basic lens data is shown in Table 53, the specifications in Table 54, the variable plane spacing in Table 55, the aspherical coefficient in Table 56, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 42 and 43.

[0191] [Table 53]

[0192] [Table 54]

[0193] [Table 55]

[0194] [Table 56]

[0195] [Example 15] Figure 44 shows the configuration and light beam of the observation optical system 5 of Example 15. The observation optical system 5 of Example 15 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0196] The eyepiece 3 consists of four lenses, L1 to L4, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens. Lens L3 is a biconcave negative lens in the paraxial region. Lens L4 is a biconvex positive lens in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L4 are aspherical lenses. All of lenses L1 to L4 are single lenses. During diopter adjustment, the four lenses L1 to L4 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0197] For the observation optical system 5 of Example 15, the basic lens data is shown in Table 57, the specifications in Table 58, the variable plane spacing in Table 59, the aspherical coefficient in Table 60, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 45 and 46.

[0198] [Table 57]

[0199] [Table 58]

[0200] [Table 59]

[0201] [Table 60]

[0202] [Example 16] Figure 47 shows the configuration and light beam of the observation optical system 5 of Example 16. The observation optical system 5 of Example 16 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0203] The eyepiece 3 consists of four lenses, L1 to L4, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens. Lens L3 is a biconcave negative lens in the paraxial region. Lens L4 is a biconvex positive lens in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L4 are aspherical lenses. All of lenses L1 to L4 are single lenses. During diopter adjustment, the four lenses L1 to L4 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0204] For the observation optical system 5 of Example 16, the basic lens data is shown in Table 61, the specifications in Table 62, the variable plane spacing in Table 63, the aspherical coefficient in Table 64, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 48 and 49.

[0205] [Table 61]

[0206] [Table 62]

[0207] [Table 63]

[0208] [Table 64]

[0209] [Example 17] Figure 50 shows the configuration and light beam of the observation optical system 5 of Example 17. The observation optical system 5 of Example 17 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0210] The eyepiece 3 consists of six lenses, L1 to L6, arranged in order from the display element side to the eye point side. Lens L1 is a positive meniscus lens with its concave surface facing the display element side. Lens L2 is a negative meniscus lens with its convex surface facing the display element side in the paraxial region. Lens L3 is a positive biconvex lens. Lens L4 is a negative biconcave lens in the paraxial region. Lens L5 is a positive meniscus lens with its concave surface facing the display element side in the paraxial region. Lens L6 is a positive biconvex lens in the paraxial region. Lenses L1 and L3 are spherical lenses, while lenses L2 and L4 to L6 are aspherical lenses. All of lenses L1 to L6 are single lenses. During diopter adjustment, the six lenses L1 to L6 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0211] For the observation optical system 5 of Example 17, the basic lens data is shown in Table 65, the specifications in Table 66, the variable plane spacing in Table 67, the aspherical coefficient in Table 68, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 51 and 52.

[0212] [Table 65]

[0213] [Table 66]

[0214] [Table 67]

[0215] [Table 68]

[0216] [Example 18] Figure 53 shows the configuration and light beam of the observation optical system 5 of Example 18. The observation optical system 5 of Example 18 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0217] The eyepiece 3 consists of six lenses, L1 to L6, arranged in order from the display element side to the eye point side. Lens L1 is a positive meniscus lens with its concave surface facing the display element side. Lens L2 is a negative meniscus lens with its convex surface facing the display element side in the paraxial region. Lens L3 is a positive biconvex lens. Lens L4 is a negative biconcave lens in the paraxial region. Lens L5 is a negative meniscus lens with its concave surface facing the display element side in the paraxial region. Lens L6 is a positive biconvex lens in the paraxial region. Lenses L1 and L3 are spherical lenses, while lenses L2 and L4 to L6 are aspherical lenses. All of lenses L1 to L6 are single lenses. During diopter adjustment, the six lenses L1 to L6 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0218] For observation optical system 5 of Example 18, the basic lens data is shown in Table 69, the specifications in Table 70, the variable plane spacing in Table 71, the aspherical coefficient in Table 72, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 54 and 55.

[0219] [Table 69]

[0220] [Table 70]

[0221] [Table 71]

[0222] [Table 72]

[0223] [Example 19] Figure 56 shows the configuration and light beam of the observation optical system 5 of Example 19. The observation optical system 5 of Example 19 comprises, in order from the display element side to the eye point side, a display element 1, an optical element 2, an eyepiece lens 3, and an optical element 4.

[0224] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L2 is a positive lens with a biconvex shape. Lens L3 is a negative lens with a biconcave shape in the paraxial region. Lens L4 is a positive lens with a meniscus shape, with its concave surface facing the display element in the paraxial region. Lens L5 is a positive lens with a biconvex shape in the paraxial region. Lens L2 is a spherical lens, while lenses L1 and L3 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the five lenses L1 to L5 move integrally along the optical axis Z, while the display element 1, optical element 2, and optical element 4 are fixed together.

[0225] For observation optical system 5 of Example 19, the basic lens data is shown in Table 73, the specifications in Table 74, the variable plane spacing in Table 75, the aspherical coefficient in Table 76, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 57 and 58.

[0226] [Table 73]

[0227] [Table 74]

[0228] [Table 75]

[0229] [Table 76]

[0230] [Example 20] Figure 59 shows the configuration and light beam of the observation optical system 5 of Example 20. The observation optical system 5 of Example 20 comprises a display element 1 and an eyepiece lens 3, arranged in order from the display element side to the eye point side.

[0231] The eyepiece 3 consists of five lenses, L1 to L5, arranged in order from the display element side to the eye point side. Lens L1 is a meniscus-shaped negative lens with its concave surface facing the display element side in the paraxial region. Lens L2 is a biconvex positive lens in the paraxial region. Lens L3 is a meniscus-shaped positive lens with its concave surface facing the display element side in the paraxial region. Lens L4 is a biconcave negative lens in the paraxial region. Lens L5 is a biconvex positive lens in the paraxial region. All of lenses L1 to L5 are aspherical lenses. All of lenses L1 to L5 are single lenses. During diopter adjustment, the display element 1 and lens L1 move together along the optical axis Z, while the four lenses L2 to L5 remain fixed.

[0232] For observation optical system 5 of Example 20, the basic lens data is shown in Table 77, the specifications in Table 78, the variable plane spacing in Table 79, the aspherical coefficient in Table 80, and the aberration diagrams for each state when the diopter is -1.00 diopters are shown in Figures 60 and 61.

[0233] [Table 77]

[0234] [Table 78]

[0235] [Table 79]

[0236] [Table 80]

[0237] Tables 81 to 85 show the corresponding values ​​for conditional equations (1) to (25) of the observation optical system 5 in Examples 1 to 20. The values ​​shown in Tables 81 to 85 are based on the d-line. The corresponding values ​​for the examples shown in Tables 81 to 85 may be used as the upper or lower limit of the conditional equation to set a preferred range for the conditional equation.

[0238] [Table 81]

[0239] [Table 82]

[0240] [Table 83]

[0241] [Table 84]

[0242] [Table 85]

[0243] The observation optical system 5 in Examples 1 to 20 has a wide apparent field of view, with an apparent field of view of 43 degrees or more across the entire field of view at a diopter of -1 diopter. Furthermore, despite its compact design, the observation optical system 5 in Examples 1 to 20 achieves high optical performance with excellent correction of various aberrations.

[0244] Next, an optical device equipped with an observation optical system according to an embodiment of this disclosure will be described. Figure 62 is a perspective view showing a schematic configuration of the rear side of a camera 100, which is an optical device according to one embodiment of this disclosure. The camera 100 is a digital camera, for example. The camera 100 includes a viewfinder 101 and a diopter adjustment dial 107 for adjusting the diopter, located on the upper part of the camera body 102. The viewfinder 101 is an example of an observation optical device and includes an observation optical system according to one embodiment of this disclosure.

[0245] Camera 100 has an operation button 103 for making various settings, a zoom lever 104 for changing the magnification, and a monitor 106 for displaying images and various setting screens on the back of the camera body 102, and a shutter button 105 on the top of the camera body 102. Camera 100 also has an imaging lens (not shown) on the front of the camera body 102, and an image sensor (not shown) inside the camera body 102 that captures the subject image formed by the imaging lens. The user looks through the viewfinder 101 from the back to observe the subject image.

[0246] Although the technology of this disclosure has been described above with reference to embodiments and examples, the technology of this disclosure is not limited to the above embodiments and examples, and various modifications are possible. For example, the radius of curvature, interplanar spacing, refractive index, Abbe number, and aspheric coefficient of each lens are not limited to the values ​​shown in the above numerical examples, but can take other values. Furthermore, the optical apparatus according to the embodiments of this disclosure is not limited to the above examples, and this disclosure can also be applied to film cameras, video cameras, head-mounted displays, and the like. [Explanation of symbols]

[0247] 1. Display respects 1a Display area 1b Cover member 2 Optical components 3 Eyepiece 4 Optical components 5. Observation Optical System 100 Cameras 101 Finder 102 Camera Body 103 Operation Buttons 104 Zoom Lever 105 Shutter button 106 Monitors 107 Diopter adjustment dial Dgnf air gap Dgnr air gap DL distance DLopn distance Dn Thickness DOPN distance EP Eye Point H is half the maximum diameter of the longest display area in the display element. L1 Lens L2 lens L3 lens L4 lens L5 lens L6 lens Z optical axis

Claims

1. The system comprises a display element and an eyepiece positioned on the eye point side of the display element, The eyepiece includes at least one negative lens, The eyepiece includes at least two lenses on the display element side of the at least one negative lens. Among the negative lenses included in the eyepiece, the negative lens with the strongest refractive power is designated as the first negative lens. Of the positive lenses included in the eyepiece, the positive lens closest to the display element is designated as the display-side positive lens. The eyepiece includes at least one positive lens on the display element side of the first negative lens, H is half the longest diameter of the display area in the display element. The focal length of the eyepiece when the diopter is -1 diopter is f, When the diopter is -1 diopter, the combined focal length from the display element side surface of the display-side positive lens to the eye point side surface of the first negative lens is fopn. The focal length of the first negative lens is fn, When the diopter is -1 diopter, the combined focal length of all lenses in the eyepiece positioned on the eye point side of the first negative lens is fr. The air distance between the lens adjacent to the eye point side of the first negative lens and the first negative lens on the optical axis is Dgnr. Dopn is the distance along the optical axis from the eye-point side surface of the display-side positive lens to the display element side surface of the first negative lens when the diopter is -1 diopter. If the thickness of the first negative lens along its optical axis is Dn, 0.35<H / f<0.6 (1) 0.1<f / fopn<1 (8) -1<fn / fr<-0.26 (12) -0.4<Dgnr / fn<-0.01 (17-3) 3.2<Dopn / Dn<7 (21-3) An observation optical system that satisfies the conditions (1), (8), (12), (17-3), and (21-3) represented by .

2. The observation optical system according to claim 1, wherein the eyepiece lens includes at least one positive lens on the display element side of the at least one negative lens.

3. The observation optical system according to claim 1 or 2, wherein the eyepiece includes at least one positive lens on the eye point side of the at least one negative lens.

4. The observation optical system according to any one of claims 1 to 3, wherein at least three lenses within the eyepiece move along the optical axis when adjusting the diopter.

5. The observation optical system according to any one of claims 1 to 4, wherein the number of lenses included in the eyepiece is five.

6. The observation optical system according to any one of claims 1 to 5, wherein the eyepiece lens includes at least two positive lenses on the display element side of the at least one negative lens.

7. The observation optical system according to any one of claims 1 to 6, wherein the first negative lens is a single lens that is not joined.

8. The paraxial radius of curvature of the display element side surface of the first negative lens is Rnf, When Ropr is the paraxial radius of curvature of the eye point side surface of the aforementioned display-side positive lens, -3<(Rnf-Ropr) / (Rnf+Ropr)<0.2 (3) An observation optical system according to any one of claims 1 to 7 that satisfies the conditional expression (3) represented by .

9. The paraaxial radius of curvature of the display element side surface of the display-side positive lens is R. When Ropr is the paraxial radius of curvature of the eye point side surface of the aforementioned display-side positive lens, -4.5<(Ropr+Ropf) / (Ropr-Ropf)<2.7 (4) An observation optical system according to any one of claims 1 to 8 that satisfies the conditional expression (4) represented by .

10. The eyepiece includes at least one positive lens on the eye point side of the at least one negative lens, Of the positive lenses included in the eyepiece, the positive lens closest to the eye point is designated as the EP-side positive lens. The paraxial radius of curvature of the display element side surface of the EP-side positive lens is Repf, If Repr is the paraxial radius of curvature of the eye point side surface of the EP-side positive lens, -2.2<(Repr+Repf) / (Repr-Repf)<1.1 (5) An observation optical system according to any one of claims 1 to 9 that satisfies the conditional expression (5) represented by .

11. If Nmax is the maximum refractive index of all lenses included in the eyepiece with respect to the d line, 1.7<Nmax<2.1 (6) An observation optical system according to any one of claims 1 to 10 that satisfies the conditional expression (6) represented by .

12. -2.8<f / fn<-0.8 (7) An observation optical system according to any one of claims 1 to 11 that satisfies the conditional expression (7) represented by .

13. 0.6<f / fr<2.2 (9) An observation optical system according to any one of claims 1 to 12 that satisfies the conditional expression (9) represented by .

14. The eyepiece includes at least one positive lens on the display element side of the at least one negative lens. When the focal length of the display-side positive lens is denoted as fop, 0.1<fop / fr<5.5 (11) An observation optical system according to any one of claims 1 to 13 that satisfies the conditional expression (11) represented by .

15. The eyepiece includes at least one positive lens on the eye point side of the at least one negative lens, Of the positive lenses included in the eyepiece, the positive lens closest to the eye point is designated as the EP-side positive lens. The paraxial radius of curvature of the display element side surface of the EP-side positive lens is Repf, When Rnr is the paraxial radius of curvature of the eye point side surface of the first negative lens, 0.01<(Repf-Rnr) / (Repf+Rnr)<3.4 (13) An observation optical system according to any one of claims 1 to 14 that satisfies the conditional expression (13) represented by .

16. The eyepiece includes at least one positive lens on the display element side of the at least one negative lens. When the diopter is -1 diopter, if DL is the distance along the optical axis from the display element side surface of the display-side positive lens to the lens surface of the eyepiece closest to the eye point, 0.75<DL / f<2.2 (14) An observation optical system according to any one of claims 1 to 15 that satisfies the conditional expression (14) represented by .

17. The eyepiece includes at least one positive lens on the display element side of the at least one negative lens. When the diopter is -1 diopter, the distance along the optical axis from the display element side surface of the display-side positive lens to the eye point side surface of the first negative lens is DLopn. Let Tn be the distance along the optical axis from the display surface of the display element to the eye-point side surface of the first negative lens when the diopter is -1 diopter. If an optical element that does not have refractive power is arranged from the display surface of the display element to the eye point side surface of the first negative lens, when calculating Tn for the optical element using the air equivalent length, 0.4<DLopn / Tn<0.9 (15) An observation optical system according to any one of claims 1 to 16 that satisfies the conditional expression (15) represented by .

18. When the air gap on the optical axis between the lens adjacent to the display element side of the first negative lens and the first negative lens is Dgnf, -0.9<Dgnf / fn<-0.01 (16) An observation optical system according to any one of claims 1 to 17 that satisfies the conditional expression (16) represented by .

19. An optical apparatus comprising an observation optical system according to any one of claims 1 to 18.

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