Ocular optical system

Abstract

To provide an ocular optical system EL which offers a high observation magnification and good optical performance, and to provide an image capturing device having the same.SOLUTION: An ocular optical system EL provided herein comprises a first lens with positive refractive power, a meniscus-shaped second lens with negative refractive power having a concave surface on the observed object side, a third lens with positive refractive power, and a meniscus-shaped fourth lens with positive refractive power having a concave surface on the observed object side, arranged in order from the observed object side, and satisfies conditions expressed as: 1.38<fe / f1<1.65, 1.600<nd1<1.800, where fe represents a focal length of the entire ocular optical system EL, f1 represents a focal length of the first lens, and nd1 represents a refractive index of a medium of the first lens for the d-ray.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an eyepiece optical system. [Background technology]

[0002] Conventionally, eyepiece optical systems having high imaging performance have been proposed (see, for example, Patent Document 1). However, Patent Document 1 has a problem in that further improvement in optical performance is desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-075713 A Summary of the Invention

[0004] The eyepiece optical system according to the first aspect of the present invention consists essentially of four lenses: a first lens having positive refractive power, a second lens having negative refractive power and a meniscus lens shape with its concave surface facing the observation object side, a third lens having positive refractive power, and a fourth lens having positive refractive power and a meniscus lens shape with its concave surface facing the observation object side, and satisfies the following condition: 1.38 < fe / f1 < 1.65 1.600 < nd1 < 1.800 however, fe: focal length of the entire eyepiece optical system f1: focal length of the first lens nd1: refractive index of the first lens medium for the d line [Brief description of the drawings]

[0005] [Figure 1] FIG. 2 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to the first example. [Diagram 2] 4A to 4C are diagrams showing various aberrations in the eyepiece optical system according to the first example. [Diagram 3]FIG. 11 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to Example 2. [Figure 4] 11A to 11C are diagrams showing various aberrations in the eyepiece optical system according to the second example. [Diagram 5] FIG. 11 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to Example 3. [Figure 6] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to the third example. [Figure 7] FIG. 13 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to Example 4. [Figure 8] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to the fourth example. [Figure 9] FIG. 13 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to Example 5. [Figure 10] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to the fifth example. [Figure 11] FIG. 13 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to Example 6. [Figure 12] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to Example 6. [Figure 13] FIG. 13 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to Example 7. [Figure 14] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to the seventh example. [Figure 15] FIG. 13 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to an eighth example. [Figure 16] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to the eighth example. [Figure 17] FIG. 13 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to a ninth example. [Figure 18] 13A to 13C are diagrams showing various aberrations in the eyepiece optical system according to the ninth example [Figure 19] FIG. 23 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to a tenth example. [Figure 20] 16A to 16C are diagrams showing various aberrations in the eyepiece optical system according to the tenth example. [Figure 21] FIG. 23 is a cross-sectional view showing the lens configuration of an eyepiece optical system according to an eleventh example. [Figure 22]16A to 16C are diagrams showing various aberrations in the eyepiece optical system according to the eleventh example. [Diagram 23] FIG. 2 is a cross-sectional view of a camera equipped with the above-mentioned eyepiece optical system. [Figure 24] 4 is a flowchart for explaining a method of manufacturing the above-mentioned eyepiece optical system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Hereinafter, preferred embodiments will be described with reference to the drawings. As shown in Fig. 1, the eyepiece optical system EL according to this embodiment has, in order from the observation object side (also simply called "object"), a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0007] Note that "lens component" refers to a single lens or a cemented lens. Furthermore, "lens element" refers to each lens that makes up a single lens or a cemented lens. Furthermore, "reference diopter" refers to when the diopter is -1 [1 / m]. Here, in terms of the unit [1 / m], diopter X [1 / m] indicates the state in which the image formed by the eyepiece optical system EL is formed at a position 1 / X [m (meters)] on the optical axis from the eyepoint (the sign is positive when the image is formed on the observer side (eyepoint side) of the eyepiece optical system EL).

[0008] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (1).

[0009] 1.38 < fe / f1 < 3.00 (1) however, fe: focal length of the entire eyepiece optical system EL f1: focal length of the first lens component G1

[0010] Conditional formula (1) specifies the refractive power of the first lens component G1 closest to the observation object in order to strengthen the overall refractive power of the eyepiece optical system EL while maintaining favorable spherical aberration and coma aberration. In the eyepiece optical system EL having the above-mentioned refractive power arrangement of positive, negative, positive, and positive from the observation object side, the first lens component G1 closest to the observation object has the least effect on spherical aberration and coma aberration. The first lens component G1 has a large effect on the deterioration of the curvature of field, but the curvature of field caused by the positive refractive power of the first lens component G1 can be corrected by the negative refractive power of the second lens component G2. Therefore, in order to increase the observation magnification of the eyepiece optical system EL while maintaining favorable spherical aberration and coma aberration, it is necessary to give a strong positive refractive power to the first lens component G1 closest to the observation object. If the lower limit of conditional expression (1) is exceeded, the positive refractive power of the first lens component G1 closest to the observation object becomes weak, the refractive power of the entire eyepiece optical system EL becomes weak, and it becomes difficult to increase the observation magnification, which is undesirable. In order to ensure the effect of conditional expression (1), it is more preferable to set the lower limit of conditional expression (1) to 1.45, more preferably 1.48, and even more preferably 1.50. In addition, if the upper limit of conditional expression (1) is exceeded, the positive refractive power of the first lens component G1 closest to the observation object becomes strong, the curvature of field generated by the first lens component G1 becomes large, and the curvature of field cannot be completely corrected by the second lens component G2, which is undesirable. In order to ensure the effect of conditional expression (1), it is more preferable to set the upper limit of conditional expression (1) to 2.00, and even more preferably 1.65.

[0011] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (2).

[0012] 0.48 < fe / f12 < 3.00 (2) however, fe: focal length of the entire eyepiece optical system EL f12: composite focal length of the first lens component G1 and the second lens component G2

[0013] Conditional formula (2) specifies the composite refractive power of the first lens component G1 and the second lens component G2 in order to increase the observation magnification and to satisfactorily correct the curvature of field. The refractive power of the first lens component G1 and the refractive power of the second lens component G2 greatly affect the correction and occurrence of the curvature of field. In order to prevent the occurrence of the curvature of field, it is desirable to weaken the composite refractive power of the first lens component G1 and the second lens component G2. However, on the other hand, if the composite refractive power of the first lens component G1 and the second lens component G2 is weakened, the refractive power of the entire eyepiece optical system EL becomes weak, making it difficult to increase the observation magnification. In addition, if the composite refractive power of the first lens component G1 and the second lens component G2 is weak and an attempt is made to forcibly increase the observation magnification, the refractive power of the third lens component G3 and the fourth lens component G4 becomes strong, causing the spherical aberration and the coma aberration to worsen. If the lower limit of the conditional expression (2) is exceeded, the composite refractive power of the first lens component G1 and the second lens component G2 becomes weak, and the observation magnification cannot be increased, which is undesirable. If the observation magnification is increased when the lower limit of the conditional expression (2) is exceeded, the spherical aberration and coma aberration become worse, which is undesirable. In order to ensure the effect of the conditional expression (2), it is more preferable to set the lower limit of the conditional expression (2) to 0.48, more preferably 0.50, and even more preferably 0.55. In addition, if the upper limit of the conditional expression (2) is exceeded, the composite refractive power of the first lens component G1 and the second lens component G2 becomes strong, and curvature of field occurs, which is undesirable. In order to ensure the effect of the conditional expression (2), it is more preferable to set the upper limit of the conditional expression (2) to 1.00, and even more preferably 0.70.

[0014] In addition, in the eyepiece optical system EL according to this embodiment, if the lens surface closest to the eyepoint of the lens closest to the eyepoint is made convex toward the eyepoint, the exit angle of the light rays near the center of the observed object from the lens surface closest to the eyepoint of the lens closest to the eyepoint becomes small, making it possible to suppress the amount of spherical aberration generated. On the other hand, the exit angle of the light rays at the periphery of the screen can be made large, making it possible to correct coma aberration.

[0015] In the eyepiece optical system EL according to the present embodiment, it is desirable that at least one of the lens elements constituting the second lens component G2 satisfies the following conditional expression (3).

[0016] 15.0 < νd2 < 35.0 (3) however, νd2: Abbe number for the d-line of the medium of the lens element having the strongest negative refractive power among the lens elements constituting the second lens component G2

[0017] Conditional expression (3) specifies the Abbe number of the lens element with the strongest negative refractive power among the lens elements constituting the second lens component G2 in order to satisfactorily correct the lateral chromatic aberration. In particular, if the composite refractive power of the first lens component G1 and the second lens component G2 is made to have a strong positive refractive power so as to satisfy the above-mentioned conditional expression (2), the negative refractive power of the second lens component G2 becomes small. Therefore, by increasing the dispersion of the lens element with the strongest negative refractive power among the second lens component G2, it is possible to satisfactorily correct the lateral chromatic aberration even with the weak negative refractive power of the second lens component G2. If the lower limit of this conditional expression (3) is not satisfied, the lateral chromatic aberration is overcorrected, and the lateral chromatic aberration is deteriorated, which is not preferable. In order to ensure the effect of this conditional expression (3), it is more preferable to set the lower limit of conditional expression (3) to 20, and more preferably 30. Also, if the upper limit of conditional expression (3) is exceeded, the lateral chromatic aberration cannot be fully corrected, which is not preferable. In order to ensure the effect of conditional expression (3), it is desirable to set the upper limit of conditional expression (3) to 22.

[0018] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (4).

[0019] 0.01 < fe / f4 < 0.33 (4) however, fe: focal length of the entire eyepiece optical system EL f4: Focal length of the fourth lens component G4

[0020] Conditional expression (4) specifies the refractive power of the lens closest to the eyepoint in order to effectively correct spherical aberration and coma. The fourth lens component G4 closest to the eyepoint has the greatest effect on spherical aberration and coma. Therefore, if the upper limit of conditional expression (4) is exceeded, the positive refractive power of the fourth lens component G4 becomes strong, and the spherical aberration and coma aberration become significantly worse, which is undesirable. In order to ensure the effect of conditional expression (4), it is more preferable to set the upper limit of conditional expression (4) to 0.30, further 0.25, and further 0.239. Also, if the lower limit of conditional expression (4) is exceeded, it becomes difficult to increase the overall refractive power of the eyepiece optical system EL, which is undesirable because it becomes impossible to increase the observation magnification. If the refractive power of the fourth lens component G4 falls below the lower limit of conditional formula (4) and the observation magnification is increased, the positive refractive power of the first lens component G1 and the third lens component G3 will become extremely strong, or the negative refractive power of the second lens component G2 will become weak, making it difficult to correct the curvature of field. In order to ensure the effect of conditional formula (4), it is more desirable to set the lower limit of conditional formula (4) to 0.10, and more preferably 0.15.

[0021] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (5).

[0022] -0.30<(G2R2-G3R1) / (G2R2+G3R1)<0.50 (5) however, G2R2: Radius of curvature of the lens surface closest to the eyepoint of the second lens component G2 G3R1: Radius of curvature of the lens surface of the third lens component G3 closest to the object

[0023] Conditional formula (5) specifies the shape of the lens surface closest to the eyepoint of the second lens component G2 and the shape of the lens surface closest to the observation object of the third lens component G3 in order to satisfactorily correct coma aberration. The lens surface closest to the eyepoint of the second lens component G2 and the lens surface closest to the observation object of the third lens component G3 greatly affect the occurrence or correction of coma aberration. In order to satisfactorily correct coma aberration, it is preferable to correct the coma aberration occurring on the lens surface closest to the eyepoint of the second lens component G2 on the lens surface closest to the observation object of the third lens component G3. In addition, in order to satisfactorily correct coma aberration, it is preferable to make the shape of the lens surface closest to the eyepoint of the second lens component G2 similar to the shape of the lens surface closest to the observation object of the third lens component G3, so that the coma aberration occurring on the lens surface closest to the eyepoint of the second lens component G2 and the coma aberration corrected on the lens surface closest to the observation object of the third lens component G3 are similar to each other, thereby canceling out the coma aberration. If the lower limit of conditional expression (5) is not satisfied, the similarity between the shape of the lens surface closest to the eyepoint of the second lens component G2 and the shape of the lens surface closest to the observation object of the third lens component G3 is lost, which is undesirable because coma aberration occurs. In order to ensure the effect of conditional expression (5), it is preferable to set the lower limit of conditional expression (5) to -0.25. In addition, if the upper limit of conditional expression (5) is exceeded, the similarity between the shape of the lens surface closest to the eyepoint of the second lens component G2 and the shape of the lens surface closest to the observation object of the third lens component G3 is lost, which is undesirable because coma aberration occurs. In order to ensure the effect of conditional expression (5), it is more preferable to set the upper limit of conditional expression (5) to 0.25, and more preferably -0.20.

[0024] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (6).

[0025] -0.75<(G1R2+G1R1) / (G1R2-G1R1)<0.00 (6) however, G1R1: Radius of curvature of the lens surface of the first lens component G1 closest to the object G1R2: Radius of curvature of the lens surface closest to the eyepoint of the first lens component G1

[0026] Conditional formula (6) specifies the shape of the first lens component G1 in order to increase the observation magnification and to satisfactorily correct the curvature of field and distortion. The positive refractive power of the first lens component G1 generates curvature of field, but the structure is such that the curvature of field generated by the negative refractive power of the second lens component G2 is corrected. If the refractive power of the lens surface of the first lens component G1 closest to the eyepoint is increased, the curvature of field generated in the first lens component G1 becomes large, and the negative refractive power of the second lens component G2 cannot correct it completely. On the other hand, in order to increase the observation magnification, it is necessary to increase the positive refractive power of the lens surface of the first lens component G1 closest to the observation object, so that the positive refractive power of the lens surface of the first lens component G1 closest to the observation object must be appropriately increased. However, if the positive refractive power of the lens surface of the first lens component G1 closest to the observation object is increased too much, distortion becomes worse. If the upper limit of conditional expression (6) is exceeded, the refractive power of the first lens component G1 becomes too large, which is undesirable as distortion aberration worsens. In order to ensure the effect of conditional expression (6), it is more preferable to set the upper limit of conditional expression (6) to -0.20, and more preferably -0.30. In addition, if the lower limit of conditional expression (6) is exceeded, the refractive power of the first lens component G1 becomes weak, and the observation magnification cannot be increased. In addition, if the observation magnification is increased while the lower limit of conditional expression (6) is exceeded, the refractive power of the lens surface closest to the eyepoint of the first lens component G1 becomes large, which is undesirable as curvature of field worsens. In addition, in order to ensure the effect of conditional expression (6), it is more preferable to set the lower limit of conditional expression (6) to -0.57, and more preferably -0.56, and even more preferably -0.50.

[0027] Furthermore, in the eyepiece optical system EL of this embodiment, by making the lens surface of the first lens component G1 closest to the observation object side a rotationally symmetric aspheric surface, it is possible to correct distortion aberration and to increase the refractive power of the lens surface of the first lens component G1 closest to the observation object side, which is advantageous for achieving a high observation magnification.

[0028] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (7).

[0029] -1.00 < fe / EnP < -0.48 (7) however, fe: focal length of the entire eyepiece optical system EL EnP: Entrance pupil position of the eyepiece optical system EL at the reference diopter (the sign is positive on the eye point side with respect to the observation object surface)

[0030] Conditional expression (7) specifies the entrance pupil position in order to increase the observation magnification while keeping the eye point long. By increasing the passing height of the chief ray of a high image height in an area close to the observation object surface, it becomes easy to increase the observation magnification while keeping the eye point long. In order to increase the passing height of the chief ray of a high image height in an area close to the observation object surface, it is effective to set the entrance pupil distance to a short distance from the observation object surface to the opposite side to the eye point side. If the upper limit value of conditional expression (7) is exceeded, the entrance pupil position is away from the observation object, so the passing height of the chief ray of a high image height cannot be increased, and it is not preferable because it is impossible to increase the magnification while keeping the eye point long. In order to ensure the effect of conditional expression (7), it is preferable to set the upper limit value of conditional expression (7) to -0.50. Also, if the lower limit value of conditional expression (7) is exceeded, the entrance pupil position is too close to the observation object, so the passing height of the chief ray of a high image height of the first lens component G1 becomes high, which is not preferable because it causes a large field curvature. In order to ensure the effect of condition (7), it is more desirable to set the lower limit of condition (7) to -0.70, and more preferably -0.65.

[0031] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (8).

[0032] -0.40 < fe / f23 < -0.15 (8) however, fe: focal length of the entire eyepiece optical system EL f23: composite focal length of the second lens component G2 and the third lens component G3

[0033] Conditional expression (8) specifies the ratio of the composite focal length of the second lens component G2 and the third lens component G3 to the focal length of the entire system of the eyepiece optical system EL in order to reduce the deterioration of the aberration performance when the optical axes of the second lens component G2 and the third lens component G3 are misaligned during manufacturing. By making the composite focal length of the second lens component G2 and the third lens component G3 smaller than the focal length of the entire system of the eyepiece optical system EL, it is possible to reduce the deterioration of the aberration performance even when the optical axes of the second lens component G2 and the third lens component G3 are misaligned due to manufacturing errors. It is also possible to reduce the deterioration of the optical performance when the refractive index or the radius of curvature of the second lens component G2 and the third lens component G3 change due to temperature changes. This is particularly effective when the second lens component G2 and the third lens component G3 are made of optical resin. If the lower limit of this conditional expression (8) is exceeded, the negative composite refractive power of the second lens component G2 and the third lens component G3 becomes strong, which is undesirable because it increases the deterioration of the aberration performance due to manufacturing errors. In order to ensure the effect of conditional expression (8), it is preferable to set the lower limit of conditional expression (8) to -0.35. Furthermore, if the upper limit of conditional expression (8) is exceeded, the negative refractive power of the second lens component G2 becomes small, which is undesirable since correction of curvature of field becomes insufficient. In order to ensure the effect of conditional expression (8), it is more preferable to set the upper limit of conditional expression (8) to -0.20, and further to -0.25.

[0034] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (9).

[0035] 0.58 < D1 / f1 < 0.90 (9) however, D1: Air-equivalent distance from the observed object to the lens surface of the first lens component G1 closest to the observed object at the reference diopter f1: focal length of the first lens component G1

[0036] Conditional formula (9) specifies the ratio of the air-equivalent distance from the observation object to the lens surface of the first lens component G1 closest to the observation object at the standard diopter to the focal length of the first lens component G1 in order to effectively correct coma. When the air-equivalent distance from the observation object to the lens surface of the first lens component G1 closest to the observation object at the standard diopter increases, the passing height of the light beam emitted from a point on the observation surface changes significantly on the first lens component G1. Therefore, when the air-equivalent distance D1 from the observation object to the lens surface of the first lens component G1 closest to the observation object increases, coma aberration occurs significantly due to the positive refractive power of the first lens component G1, so it is necessary to reduce the refractive power of the first lens component G1. On the other hand, in order to increase the refractive power of the first lens component G1, it is necessary to reduce the air-equivalent distance D1 from the observation object to the lens surface of the first lens component G1 closest to the observation object in order to reduce the coma aberration generated by the first lens component G1. If the upper limit of conditional expression (9) is exceeded, the refractive power of the first lens component G1 becomes stronger relative to the air-equivalent distance D1 from the observation object to the lens surface of the first lens component G1 closest to the observation object, and coma aberration worsens, which is undesirable. In order to ensure the effect of conditional expression (9), it is more preferable to set the upper limit of conditional expression (9) to 0.71, and more preferably 0.68. In addition, if the lower limit of conditional expression (9) is exceeded, the positive refractive power of the first lens component G1 becomes weak, and it is not possible to increase the observation magnification, which is undesirable. In order to ensure the effect of conditional expression (9), it is more preferable to set the lower limit of conditional expression (9) to 0.60, and more preferably 0.63.

[0037] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (10): The total length of the eyepiece optical system EL is the distance on the optical axis from the observation object O to the lens surface of the eyepiece optical system EL that is closest to the eyepoint.

[0038] 1.50 < TL / fe < 1.80 (10) however, TL: Total length of the eyepiece optical system EL fe: focal length of the entire eyepiece optical system EL

[0039] Conditional expression (10) prescribes the ratio of the overall length of the eyepiece optical system EL to the focal length of the entire system in order to correct the curvature of field. If the lower limit of conditional expression (10) is not satisfied, the overall refractive power of the eyepiece optical system EL becomes weak and the observation magnification cannot be increased, which is undesirable. In order to ensure the effect of conditional expression (10), it is more preferable to set the lower limit of conditional expression (10) to 1.55, and more preferably 1.60. In addition, if the upper limit of conditional expression (10) is exceeded, the curvature of field worsens, which is undesirable. In order to ensure the effect of conditional expression (10), it is more preferable to set the upper limit of conditional expression (10) to 1.70.

[0040] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (11): When the first lens component G1 is composed of a cemented lens and has a plurality of lens elements, at least one of these lens elements satisfies conditional expression (11).

[0041] 1.550 < nd1 < 1.800 (11) however, nd1: refractive index of the medium of the lens element constituting the first lens component G1 with respect to the d line

[0042] Conditional expression (11) specifies the refractive index of the medium of the lens element constituting the first lens component G1 with respect to the d-line in order to satisfactorily correct distortion and curvature of field. If the lower limit of conditional expression (11) is exceeded, the first lens component G1 cannot have refractive power, and it is difficult to maintain performance and achieve high magnification, which is undesirable. In order to ensure the effect of conditional expression (11), it is more preferable to set the lower limit of conditional expression (11) to 1.600, and more preferably 1.700. In addition, if the upper limit of conditional expression (11) is exceeded, distortion will worsen, which is undesirable. In order to ensure the effect of conditional expression (11), it is more preferable to set the upper limit of conditional expression (11) to 1.850.

[0043] Moreover, it is desirable for the eyepiece optical system EL according to this embodiment to satisfy the following conditional expression (12): When the second lens component G2 is composed of a cemented lens and has a plurality of lens elements, at least one of these lens elements satisfies conditional expression (12).

[0044] 1.640 < nd2 < 1.800 (9) however, nd2: refractive index of the medium of the lens element constituting the second lens component G2 for the d line

[0045] Conditional expression (12) specifies the refractive index for the d-line of the medium of the lens element constituting the second lens component G2 in order to satisfactorily correct astigmatism. If the lower limit of conditional expression (12) is not satisfied, the optical performance is degraded due to decentering of the second lens component G2, which is not preferable. In order to ensure the effect of conditional expression (12), it is preferable to set the lower limit of conditional expression (12) to 1.650. In addition, if the upper limit of conditional expression (12) is exceeded, it is not preferable because it becomes difficult to correct astigmatism. In order to ensure the effect of conditional expression (12), it is preferable to set the upper limit of conditional expression (12) to 1.750.

[0046] Furthermore, the eyepiece optical system EL of this embodiment has the first lens component G1, the second lens component G2, the third lens component G3, and the fourth lens component G4 configured as single lenses, and is therefore able to achieve sufficiently good aberration performance even when configured with four single lenses.

[0047] Moreover, in the eyepiece optical system EL according to this embodiment, diopter adjustment can be easily performed by moving the entire eyepiece optical system in the optical axis direction.

[0048] It should be noted that the conditions and configurations described above each provide the effects described above, and are not limited to those that satisfy all of the conditions and configurations. The effects described above can be obtained by satisfying any one of the conditions or configurations, or any combination of the conditions or configurations.

[0049] Next, a camera, which is an optical instrument (imaging device) equipped with the eyepiece optical system EL according to this embodiment, will be described with reference to FIG. 23. This camera 1 is a so-called mirrorless camera of an interchangeable lens type equipped with an objective lens (photographing lens) OL. In this camera 1, light from an object (subject) (not shown) is collected by the objective lens OL and forms a subject image on an imaging surface of an imaging unit C via an OLPF (Optical low pass filter) (not shown). Then, the subject image is photoelectrically converted by a photoelectric conversion element provided in the imaging unit C to generate an image of the subject. This image is displayed on an electronic view finder EVF (Electronic view finder) provided in the camera 1. Here, the electronic view finder EVF is configured to have an image display element DP such as a liquid crystal display element, and an eyepiece optical system EL for enlarging and observing an image displayed on a display surface (the above-mentioned observation object O) of the image display element DP. Thereby, a photographer can observe an image of the object (subject) formed by the objective lens OL through the eyepiece optical system EL by positioning his / her eye at the eyepoint EP.

[0050] Furthermore, when the photographer presses a release button (not shown), the image photoelectrically converted by the imaging section C is stored in a memory (not shown). In this manner, the photographer can photograph the subject using the camera 1. Note that, although an example of a mirrorless camera has been described in this embodiment, the same effects as those of the camera 1 can be achieved even if the eyepiece optical system EL according to this embodiment is mounted on a single-lens reflex type camera that has a quick-return mirror in the camera body and observes the subject through a viewfinder optical system.

[0051] Thus, the eyepiece optical system EL according to this embodiment is an optical system (eyepiece) for magnifying and observing an image. Here, the image refers to an intermediate image formed by an objective lens, or a display surface of an image display element such as a liquid crystal display element or an organic EL display, and is preferably a display surface of an organic EL display. Therefore, the eyepiece optical system EL according to this embodiment is suitable for use as an eyepiece of electronic binoculars, head-mounted displays, and built-in or external electronic viewfinders for cameras for observing images displayed on a display surface, for example.

[0052] Although not shown in Fig. 1 etc., an optical member such as a cover glass or a prism may be disposed between the observation object O (the display surface of the image display element DP shown in Fig. 23) and the first lens component G1. Also, an optical member such as a cover glass may be disposed between the fourth lens component G4 and the eye point EP.

[0053] Hereinafter, an outline of a manufacturing method of the eyepiece optical system EL according to this embodiment will be described with reference to Fig. 24. First, the lenses are arranged to prepare a first lens component G1 having a positive refractive power, a second lens component G2 having a negative refractive power, a third lens component G3 having a positive refractive power, and a fourth lens component G4 having a positive refractive power (Step S100). Then, they are arranged so as to satisfy the conditions of a predetermined conditional formula (for example, the above-mentioned conditional formula (1) or conditional formula (2)) (Step S200).

[0054] 1, the first lens component G1 is an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically, the second lens component G2 is an aspherical negative lens L12 having a negative meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically and with the concave surface facing the observation object side, the third lens component G3 is an aspherical positive lens L31 having a positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically and with the concave surface facing the object side, and the fourth lens component G4 is an aspherical positive lens L41 having a positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically and with the concave surface facing the observation object side. The lens components prepared in this way are arranged in the above-mentioned procedure to manufacture the eyepiece optical system EL.

[0055] With the above-described configuration, it is possible to provide an eyepiece optical system EL having a large observation magnification and good optical performance, an optical instrument (image pickup device) having this eyepiece optical system EL, and a method for manufacturing the eyepiece optical system EL. EXAMPLES

[0056] Each embodiment of the present application will be described below with reference to the drawings. Note that Fig. 1, Fig. 3, Fig. 5, Fig. 7, Fig. 9, Fig. 11, Fig. 13, Fig. 15, Fig. 17, Fig. 19 and Fig. 21 are cross-sectional views showing the configuration and refractive power distribution of the eyepiece optical system EL (EL1 to EL11) according to each embodiment.

[0057] In these examples, the aspheric surface is expressed by the following formula (a), where y is the height in the direction perpendicular to the optical axis, S(y) is the distance along the optical axis from the tangent plane of the apex of each aspheric surface at the height y to each aspheric surface (amount of sag), r is the radius of curvature (paraxial radius of curvature) of the reference sphere, K is the conic constant, and An is the n-th order aspheric coefficient. Note that in the following examples, "En" is expressed as "×10 -n ".

[0058] S(y)=(y 2 / r) / {1+(1-K×y 2 / r 2 ) 1 / 2} +A4×y 4 +A6×y 6 +A8×y 8 +A10×y 10 +A12×y 12 (a)

[0059] In each embodiment, the second-order aspheric coefficient A2 is 0. In the table of each embodiment, aspheric surfaces are marked with an * to the right of the surface number.

[0060] [First Example] 1 is a diagram showing the configuration of an eyepiece optical system EL1 according to Example 1. This eyepiece optical system EL1 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0061] In this eyepiece optical system EL1, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The second lens component G2 is composed of an aspherical negative lens L12 having a negative meniscus lens shape with the concave surface facing the observation object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the concave surface facing the object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The fourth lens component G4 is composed of an aspherical positive lens L41 having a positive meniscus lens shape with the concave surface facing the observation object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspheric.

[0062] The diopter adjustment in the eyepiece optical system EL1 is performed by moving the entire eyepiece optical system EL1 in the direction of the optical axis.

[0063] Table 1 below lists the values ​​of the specifications of the eyepiece optical system EL1. In Table 1, fe in the overall specifications indicates the focal length of the entire system, H indicates the maximum object height, and TL indicates the overall length. In addition, in the lens data, column 1 m indicates the order of the lens surfaces from the object side along the direction of light travel (surface number), column 2 r indicates the radius of curvature of each lens surface, column 3 d indicates the distance on the optical axis from each optical surface to the next optical surface (surface spacing), and columns 4 nd and 5 νd indicate the refractive index and Abbe number for the d-line (λ=587.6 nm). In addition, the radius of curvature ∞ indicates a flat surface, and the refractive index of air, 1.00000, is omitted. In addition, the object surface indicates the observed object O, and the image surface indicates the eyepoint EP.

[0064] Here, the focal length f (fOe, fEe, etc.), radius of curvature r, surface spacing d, and other length units listed in all the following specifications are generally in "mm", but the optical system can obtain the same optical performance even if it is proportionally enlarged or reduced, so it is not limited to this. Also, the explanations of these symbols and the specifications tables are the same in the following examples.

[0065] As described above, although not shown in the following embodiments including this embodiment, when an optical member such as a cover glass, a prism, or a display cover glass is disposed between the observation object O and the first lens component G1, or between the fourth lens component G4 and the eyepoint EP, the surface distance d is the air-equivalent length.

[0066] (Table 1) First Example [Overall specifications] fe = 17.641 H = 6.30 TL = 28.790 [Lens data] mrd nd νd Object surface ∞ D1 1* 29.01673 6.95 1.77377 47.25 2* -11.37822 3.03 3* -6.74812 1.50 1.63550 23.89 4* -58.92577 1.25 5* -48.01803 5.40 1.53110 55.91 6* -10.14569 0.50 7* -1037.93340 2.75 1.53110 55.91 8* -42.12958 D2 Image plane ∞

[0067] In this eyepiece optical system EL1, surfaces 1, 2, 3, 4, 5, 6, 7, and 8 are aspheric. Table 2 below shows data on the aspheric surfaces, i.e., the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0068] (Table 2) [Aspheric data] Front page K=-1.0414 A4 =-1.29144E-04 A6 =-4.67158E-07 A8 = 1.78024E-08 A10=-1.65828E-10 A12= 6.30320E-13 2nd side K=-2.2911 A4 =-1.46042E-04 A6 = 1.05047E-06 A8 =-8.71894E-09 A10= 3.48401E-11 A12= 0.00000E+00 3rd page K=-0.2684 A4 = 3.35859E-04 A6 = -4.37805E-06 A8 = 2.17895E-08 A10=-4.94107E-11 A12= 0.00000E+00 Side 4 K = 5.9869 A4 = 9.81668E-05 A6 = -1.20860E-06 A8 = 6.95819E-09 A10=-1.72138E-11 A12= 0.00000E+00 5th page K=5.9905 A4 = 2.82487E-05 A6 = 1.16190E-06 A8 =-1.23653E-08 A10= 4.18910E-11 A12= 0.00000E+00 Page 6 K = 0.3916 A4 = 1.91131E-04 A6 =-3.21702E-07 A8 =-3.26701E-09 A10= 2.35655E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.52684E-04 A6 = 1.49017E-06 A8 =-1.20661E-08 A10= 5.44999E-11 A12= 0.00000E+00 Side 8 K = 3.6084 A4 =-2.40943E-04 A6 = 2.55221E-06 A8 =-1.68422E-08 A10= 5.77483E-11 A12= 0.00000E+00

[0069] In this eyepiece optical system EL1, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 3 below shows the variable distances and entrance pupil positions for each diopter. Note that diopters are expressed as -1 [1 / m] as "-1 dpt", +2 [1 / m] as "+2 dpt", and -4 [1 / m] as "-4 dpt". The same applies to the following examples.

[0070] (Table 3) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.41 8.33 6.39 D2 20.60 19.68 21.62 EnP -29.03270 -30.46513 -27.64176

[0071] Table 4 below shows the corresponding values ​​of each conditional expression of this eyepiece optical system EL1.

[0072] (Table 4) f4 = 82.602 f12= ​​28.790 f23=-63.706 [Conditional expression corresponding value] (1) fe / f1=1.545 (2) fe / f12 = 0.613 (3)νd2=23.89 (4) fe / f4=0.214 (5)(G2R2-G3R1) / (G2R2+G3R1)= 0.102 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.437 (7)fe / EnP=-0.608 (8)fe / f23=-0.277 (9) D1 / f1=0.649 (10)TL / fe=1.632 (11)nd1=1.774 (12)nd2=1.636

[0073] In this way, the eyepiece optical system EL1 satisfies the above conditional expressions (1) to (11).

[0074] FIG. 2 shows diagrams of spherical aberration, astigmatism, distortion, and coma for this eyepiece optical system EL1 at the reference diopter (-1 dpt). The horizontal axis of the spherical aberration and astigmatism diagrams is in units of "1 / m", which is indicated by "D" in the diagrams. The coma and lateral chromatic aberration diagrams show minutes in angular units, and d and g in the diagrams show aberration curves at the d-line and g-line. The coma diagram shows the aberration curve for each object height. The same explanation applies to the following examples. From these aberration diagrams, it can be seen that this eyepiece optical system EL1 achieves good aberration within the diopter adjustment range.

[0075] [Second Example] 3 is a diagram showing the configuration of the eyepiece optical system EL2 according to Example 2. This eyepiece optical system EL2 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0076] In this eyepiece optical system EL2, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically. The second lens component G2 is composed of an aspherical negative lens L12 having a negative meniscus lens shape with the concave surface facing the observation object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspherically. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the concave surface facing the object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspherically. The fourth lens component G4 is composed of an aspherical positive lens L41 having a positive meniscus lens shape with the concave surface facing the observation object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspherically.

[0077] The diopter adjustment in the eyepiece optical system EL2 is performed by moving the entire eyepiece optical system EL2 in the direction of the optical axis.

[0078] Table 5 below lists the specifications of the eyepiece optical system EL2.

[0079] (Table 5) Second Example [Overall specifications] fe = 18.135 H = 6.30 TL = 28.100 [Lens data] mrd nd νd Object surface ∞ D1 1* 18.29768 7.45 1.53110 55.91 2* -8.02783 2.40 3* -5.08738 2.15 1.63550 23.89 4* -16.13188 0.50 5* -46.53675 5.00 1.53110 55.91 6* -9.74321 0.50 7* -62.07807 2.30 1.53110 55.91 8* -36.52997 D2 Image plane ∞

[0080] In this eyepiece optical system EL2, surfaces 1, 2, 3, 4, 5, 6, 7, and 8 are aspheric. Table 6 below shows the data on the aspheric surfaces, i.e., the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0081] (Table 6) [Aspheric data] Front page K = 0.4135 A4 =-1.67471E-04 A6 =-2.55937E-06 A8 =4.54261E-08 A10=-3.19957E-10 A12= 1.06400E-12 2nd side K=-2.0545 A4 =-3.02431E-04 A6 = 3.45590E-06 A8 =-3.41508E-08 A10= 1.41269E-10 A12= 0.00000E+00 Page 3 K=-0.3061 A4 = 5.48726E-04 A6 =-5.11105E-06 A8 =-4.02571E-10 A10= 6.06422E-11 A12= 0.00000E+00 Page 4 K=-3.9720 A4 = 1.64809E-04 A6 =-6.23672E-07 A8 =-3.44304E-09 A10= 4.26001E-12 A12= 0.00000E+00 Page 5 K = 5.8883 A4 =-5.24409E-05 A6 = 5.07414E-07 A8 = 3.77890E-09 A10=-1.41672E-11 A12= 0.00000E+00 Page 6 K = 0.4195 A4 = 2.57996E-04 A6 =-1.85757E-06 A8 = 2.18453E-09 A10= 5.57891E-11 A12= 0.00000E+00 Page 7 K = 4.9451 A4 =-8.67424E-05 A6 = 9.74736E-07 A8 = 5.79036E-09 A10=-6.53413E-11 A12= 0.00000E+00 Page 8 K = 5.7525 A4 =-2.08333E-04 A6 = 2.55741E-06 A8 =-6.33475E-09 A10=-2.34517E-11 A12= 0.00000E+00

[0082] In this eyepiece optical system EL2, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eyepoint EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 7 below shows the variable distances and entrance pupil positions for each diopter.

[0083] (Table 7) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.80 8.77 6.74 D2 20.60 19.63 21.66 EnP -34.92593 -37.22500 -32.79600

[0084] Table 8 below shows the corresponding values ​​of each conditional expression of this eyepiece optical system EL2.

[0085] (Table 8) f4 =162.068 f12= ​​33.567 f23=-93.824 [Conditional expression corresponding value] (1) fe / f1=1.557 (2) fe / f12 = 0.540 (3)νd2=23.89 (4) fe / f4 = 0.112 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.485 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.390 (7)fe / EnP=-0.519 (8)fe / f23=-0.193 (9) D1 / f1=0.670 (10)TL / fe=1.550 (11)nd1=1.531 (12)nd2=1.636

[0086] In this way, the eyepiece optical system EL2 satisfies the above conditional expressions (1) to (4) and (6) to (10).

[0087] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL2 at the reference diopter (-1 dpt) are shown in Figure 4. These aberration diagrams show that this eyepiece optical system EL2 achieves good aberration correction within the diopter adjustment range.

[0088] [Third Example] 5 is a diagram showing the configuration of an eyepiece optical system EL3 according to Example 3. This eyepiece optical system EL3 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0089] In this eyepiece optical system EL3, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically. The second lens component G2 is composed of an aspherical negative lens L12 having a biconcave negative lens shape with the lens surface on the observation object side formed aspherically. The third lens component G3 is composed of an aspherical positive lens L31 having a biconvex positive lens shape with the lens surface on the eye point side formed aspherically. The fourth lens component G4 is composed of an aspherical positive lens L41 having a positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically and the concave surface facing the observation object side.

[0090] The diopter adjustment in the eyepiece optical system EL3 is performed by moving the entire eyepiece optical system EL3 in the direction of the optical axis.

[0091] Table 9 below lists the specifications of the eyepiece optical system EL3.

[0092] (Table 9) Third Example [Overall specifications] fe = 17.654 H = 6.30 TL = 29.118 [Lens data] mrd nd νd Object surface ∞ D1 1* 37.20780 7.34 1.82098 42.50 2* -10.78310 2.69 3* -6.86450 1.58 1.63550 23.89 4 403.03380 0.98 5 365.51190 5.94 1.53110 55.91 6* -10.45160 0.50 7* -40.06410 2.69 1.53110 55.91 8* -25.10660 D2 Image plane ∞

[0093] In this eyepiece optical system EL3, surfaces 1, 2, 3, 6, 7, and 8 are aspheric. Table 10 below shows data on the aspheric surfaces, that is, the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0094] (Table 10) [Aspheric data] Front page K = 3.5010 A4 =-1.08770E-04 A6 =-7.76264E-07 A8 = 1.84546E-08 A10=-1.13779E-10 A12= 3.71750E-13 2nd side K=-2.3099 A4 =-1.29893E-04 A6 =9.59335E-07 A8 =-7.24273E-09 A10= 3.52620E-11 A12= 0.00000E+00 3rd page K=-0.1511 A4 = 4.02440E-04 A6 = -4.00609E-06 A8 = 2.11556E-08 A10=-1.51294E-10 A12= 0.00000E+00 Page 6 K = 0.5856 A4 = 2.62266E-04 A6 =-6.94589E-07 A8 =-3.75126E-09 A10= 2.70416E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.21897E-04 A6 = 1.25808E-06 A8 =-5.29696E-09 A10= 4.01375E-11 A12= 0.00000E+00 Side 8 K = 0.9506 A4 =-2.35090E-04 A6 = 2.42051E-06 A8 =-1.44574E-08 A10= 7.36171E-11 A12= 0.00000E+00

[0095] In this eyepiece optical system EL3, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 11 below shows the variable distances and entrance pupil positions for each diopter.

[0096] (Table 11) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.41 8.34 6.40 D2 20.60 19.67 21.61 EnP -30.17343 -31.78442 -28.65171

[0097] Table 12 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL3.

[0098] (Table 12) f4 =119.198 f12 = 34.675 f23=-70.015 [Conditional expression corresponding value] (1) fe / f1=1.614 (2) fe / f12=0.509 (3)νd2=23.89 (4) fe / f4 = 0.148 (5)(G2R2-G3R1) / (G2R2+G3R1)= 0.049 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.551 (7)fe / EnP=-0.585 (8)fe / f23=-0.252 (9) D1 / f1=0.678 (10)TL / fe=1.649 (11)nd1=1.821 (12)nd2=1.636

[0099] In this way, the eyepiece optical system EL3 satisfies the above conditional expressions (1) to (11).

[0100] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL3 at the reference diopter (-1 dpt) are shown in Figure 6. These aberration diagrams show that this eyepiece optical system EL3 achieves good aberration correction within the diopter adjustment range.

[0101] [Fourth Example] 7 is a diagram showing the configuration of an eyepiece optical system EL4 according to Example 4. This eyepiece optical system EL4 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0102] In this eyepiece optical system EL4, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The second lens component G2 is composed of an aspherical negative lens L12 having a negative meniscus lens shape with the concave surface facing the observation object side with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the concave surface facing the observation object side with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The fourth lens component G4 is composed of an aspherical positive lens L41 having a positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric.

[0103] The diopter adjustment in the eyepiece optical system EL4 is performed by moving the entire eyepiece optical system EL4 in the direction of the optical axis.

[0104] Table 13 below lists the specifications of the eyepiece optical system EL4.

[0105] (Table 13) Fourth Example [Overall specifications] fe = 17.636 H = 6.30 TL = 29.262 [Lens data] mrd nd νd Object surface ∞ D1 1* 24.08699 7.78 1.77377 47.25 2* -11.23946 2.66 3* -6.16897 1.50 1.63550 23.89 4* -35.90996 1.64 5* -30.97534 4.55 1.53110 55.91 6* -9.95862 0.50 7* -2317.28230 2.89 1.53110 55.91 8* -41.10583 D2 Image plane ∞

[0106] In this eyepiece optical system EL4, surfaces 1, 2, 3, 4, 5, 6, 7, and 8 are aspheric. Table 14 below shows data on the aspheric surfaces, i.e., the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0107] (Table 14) [Aspheric data] Front page K = 2.7110 A4 =-1.01182E-04 A6 =-1.33523E-06 A8 = 1.97743E-08 A10=-1.25195E-10 A12= 4.06080E-13 2nd side K=-2.9040 A4 =-1.58180E-04 A6 = 1.29335E-06 A8 =-1.01444E-08 A10= 4.38226E-11 A12= 0.00000E+00 3rd page K=-0.4456 A4 = 4.04109E-04 A6 = -4.62087E-06 A8 = 2.20818E-08 A10=-6.21510E-11 A12= 0.00000E+00 Side 4 K=-3.9080 A4 = 1.79698E-04 A6 =-1.03102E-06 A8 =-1.74072E-09 A10= 1.01196E-11 A12= 0.00000E+00 5th page K = 3.7707 A4 =-3.78236E-06 A6 = 1.16143E-06 A8 =-5.58959E-09 A10= 1.44702E-12 A12= 0.00000E+00 Page 6 K = 0.6581 A4 = 2.55240E-04 A6 =-5.27043E-07 A8 =-3.06199E-10 A10= 4.00895E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.20441E-04 A6 = 1.18792E-06 A8 =-6.17544E-09 A10= 2.72498E-11 A12= 0.00000E+00 Side 8 K=-2.5146 A4 =-2.41805E-04 A6 = 2.45866E-06 A8 =-1.44853E-08 A10= 5.06379E-11 A12= 0.00000E+00

[0108] In this eyepiece optical system EL4, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 15 below shows the variable distances and entrance pupil positions for each diopter.

[0109] (Table 15) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.75 8.68 6.74 D2 20.60 19.67 21.61 EnP -28.77738 -30.14404 -27.47277

[0110] Table 16 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL4.

[0111] (Table 16) f4 = 78.761 f12= ​​26.175 f23=-44.512 [Conditional expression corresponding value] (1) fe / f1=1.610 (2) fe / f12 = 0.674 (3)νd2=23.89 (4) fe / f4 = 0.224 (5)(G2R2-G3R1) / (G2R2+G3R1)= 0.074 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.364 (7)fe / EnP=-0.613 (8)fe / f23=-0.396 (9) D1 / f1=0.707 (10)TL / fe=1.659 (11)nd1=1.774 (12)nd2=1.636

[0112] In this way, the eyepiece optical system EL4 satisfies the above conditional expressions (1) to (11).

[0113] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL4 at the reference diopter (-1 dpt) are shown in Figure 8. These aberration diagrams show that this eyepiece optical system EL4 achieves good aberration correction within the diopter adjustment range.

[0114] [Fifth Example] 9 is a diagram showing the configuration of an eyepiece optical system EL5 according to Example 5. This eyepiece optical system EL5 is configured to have, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0115] In this eyepiece optical system EL5, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The second lens component G2 is composed of an aspherical negative lens L12 having a negative meniscus lens shape with the concave surface facing the observation object side with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the concave surface facing the observation object side with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The fourth lens component G4 is composed of an aspherical positive lens L41 having a positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric.

[0116] The diopter adjustment in the eyepiece optical system EL5 is performed by moving the entire eyepiece optical system EL5 in the optical axis direction.

[0117] Table 17 below lists the specifications of the eyepiece optical system EL5.

[0118] (Table 17) Fifth Example [Overall specifications] fe = 18.132 H = 6.30 TL = 27.900 [Lens data] mrd nd νd Object surface ∞ D1 1* 18.12430 7.15 1.54392 55.90 2* -8.93740 2.70 3* -5.25010 2.10 1.63550 23.89 4* -15.01890 0.55 5* -24.00760 4.55 1.54392 55.90 6* -9.36770 0.55 7* -2317.28230 2.50 1.54392 55.90 8* -51.99250 D2 Image plane ∞

[0119] In this eyepiece optical system EL5, surfaces 1, 2, 3, 4, 5, 6, 7, and 8 are formed aspheric. Table 18 below shows data on the aspheric surfaces, that is, the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0120] (Table 18) [Aspheric data] Front page K = 1.5721 A4 =-1.48925E-04 A6 =-2.27684E-06 A8 = 2.76091E-08 A10=-7.95927E-11 A12= 1.93700E-15 2nd side K=-2.1582 A4 =-2.07700E-04 A6 = 1.44079E-06 A8 =-1.32371E-08 A10= 7.80799E-11 A12= 0.00000E+00 3rd page K=-0.3642 A4 = 4.11218E-04 A6 = -4.53688E-06 A8 = 1.52134E-08 A10=-5.51553E-11 A12= 0.00000E+00 Side 4 K=-2.1105 A4 = 1.75549E-04 A6 =-6.55035E-07 A8 =-1.17880E-09 A10=-1.10549E-11 A12= 0.00000E+00 5th page K=-2.6173 A4 = 3.84318E-05 A6 = 5.26426E-07 A8 =-3.63630E-09 A10= 1.31408E-11 A12= 0.00000E+00 Page 6 K = 0.5270 A4 = 3.06334E-04 A6 =-1.20258E-06 A8 =-2.58312E-09 A10= 7.29168E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.44498E-04 A6 = 6.56846E-07 A8 = 4.58887E-09 A10=-2.74632E-11 A12= 0.00000E+00 Side 8 K = 3.4680 A4 =-2.80056E-04 A6 = 2.69450E-06 A8 =-1.10674E-08 A10= 1.88829E-11 A12= 0.00000E+00

[0121] In this eyepiece optical system EL5, the axial air distance D1 between the object and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 19 below shows the variable distances and entrance pupil positions for each diopter.

[0122] (Table 19) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.80 8.78 6.74 D2 20.70 19.72 21.76 EnP -34.42818 -36.66472 -32.37294

[0123] Table 20 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL5.

[0124] (Table 20) f4 = 97.744 f12 = 31.386 f23=-77.761 [Conditional expression corresponding value] (1) fe / f1=1.494 (2) fe / f12 = 0.578 (3)νd2=23.89 (4) fe / f4 = 0.186 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.230 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.339 (7)fe / EnP=-0.527 (8)fe / f23=-0.233 (9) D1 / f1=0.643 (10)TL / fe=1.539 (11)nd1=1.544 (12)nd2=1.636

[0125] In this way, the eyepiece optical system EL5 satisfies the above conditional expressions (1) to (10).

[0126] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL5 at the reference diopter (-1 dpt) are shown in Figure 10. These aberration diagrams show that this eyepiece optical system EL5 achieves good aberration correction within the diopter adjustment range.

[0127] [Sixth Example] 11 is a diagram showing the configuration of an eyepiece optical system EL6 according to Example 6. This eyepiece optical system EL6 is configured to have, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0128] In this eyepiece optical system EL6, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The second lens component G2 is composed of an aspherical negative lens L12 having a negative meniscus lens shape with the concave surface facing the observation object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the concave surface facing the observation object side and the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The fourth lens component G4 is composed of an aspherical positive lens L41 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric.

[0129] The diopter adjustment in the eyepiece optical system EL6 is performed by moving the entire eyepiece optical system EL6 in the direction of the optical axis.

[0130] Table 21 below lists the specifications of the eyepiece optical system EL6.

[0131] (Table 21) Sixth Example [Overall specifications] fe = 18.123 H = 6.30 TL = 28.139 [Lens data] mrd nd νd Object surface ∞ D1 1* 16.56700 7.54 1.53110 55.91 2* -8.36450 2.40 3* -5.15230 2.11 1.63550 23.89 4* -15.20140 0.72 5* -23.94520 4.46 1.53110 55.91 6* -9.83340 0.50 7* 153.86920 2.57 1.53110 55.91 8* -57.12010 D2 Image plane ∞

[0132] In this eyepiece optical system EL6, surfaces 1, 2, 3, 4, 5, 6, 7, and 8 are aspheric. Table 22 below shows data on the aspheric surfaces, i.e., the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0133] (Table 22) [Aspheric data] Front page K = 0.7228 A4 =-1.63997E-04 A6 =-2.61921E-06 A8 = 3.31813E-08 A10=-1.23005E-10 A12= 1.44200E-13 2nd side K=-2.0402 A4 =-2.39241E-04 A6 = 1.88690E-06 A8 =-1.74329E-08 A10= 7.72117E-11 A12= 0.00000E+00 3rd page K=-0.4513 A4 = 4.08176E-04 A6 = -4.24658E-06 A8 = 1.05383E-08 A10=-4.81073E-11 A12= 0.00000E+00 Side 4 K=-2.0834 A4 = 1.95661E-04 A6 =-5.64298E-07 A8 =-2.58247E-09 A10=-1.66041E-11 A12= 0.00000E+00 5th page K=-3.9899 A4 = 7.61468E-06 A6 = 4.89100E-07 A8 = 5.08311E-10 A10=-5.69059E-12 A12= 0.00000E+00 Page 6 K = 0.4497 A4 = 2.70507E-04 A6 =-1.61737E-06 A8 =-1.10795E-09 A10= 7.33076E-11 A12= 0.00000E+00 Side 7 K=-4.0000 A4 =-1.50783E-04 A6 = 6.32142E-07 A8 = 8.23469E-09 A10=-5.41717E-11 A12= 0.00000E+00 Side 8 K = 4.7540 A4 =-2.61403E-04 A6 = 2.68176E-06 A8 =-9.54981E-09 A10= 4.35054E-12 A12= 0.00000E+00

[0134] In this eyepiece optical system EL6, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 23 below shows the variable distances and entrance pupil positions for each diopter.

[0135] (Table 23) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.84 8.82 6.78 D2 20.60 19.62 21.66 EnP -34.03960 -36.20254 -32.04697

[0136] Table 24 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL6.

[0137] (Table 24) f4 = 78.767 f12= ​​30.113 f23=-49.345 [Conditional expression corresponding value] (1) fe / f1=1.550 (2) fe / f12 = 0.602 (3)νd2=23.89 (4) fe / f4=0.230 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.223 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.329 (7)fe / EnP=-0.532 (8)fe / f23=-0.367 (9) D1 / f1=0.671 (10)TL / fe=1.553 (11)nd1=1.531 (12)nd2=1.636

[0138] In this way, the eyepiece optical system EL6 satisfies the above conditional expressions (1) to (10).

[0139] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL6 at the reference diopter (-1 dpt) are shown in Figure 12. These aberration diagrams show that this eyepiece optical system EL6 achieves good aberration correction within the diopter adjustment range.

[0140] [Seventh Example] 13 is a diagram showing the configuration of an eyepiece optical system EL7 according to Example 7. This eyepiece optical system EL7 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0141] In this eyepiece optical system EL7, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The second lens component G2 is composed of an aspherical negative lens L12 having a negative meniscus lens shape with the lens surface on the observation object side formed aspheric and the concave surface facing the observation object side. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the lens surface on the eye point side formed aspheric and the concave surface facing the observation object side. The fourth lens component G4 is composed of an aspherical positive lens L41 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric.

[0142] The diopter adjustment in the eyepiece optical system EL7 is performed by moving the entire eyepiece optical system EL7 in the direction of the optical axis.

[0143] Table 25 below lists the specifications of the eyepiece optical system EL7.

[0144] Table 25: Seventh Example [Overall specifications] fe = 17.662 H = 6.30 TL = 28.320 [Lens data] mrd nd νd Object surface ∞ D1 1* 28.07266 7.30 1.74400 44.80 2* -10.67758 2.70 3* -6.63855 1.55 1.63550 23.89 4 -144.14719 1.00 5 -167.66045 5.95 1.53110 55.91 6* -11.29042 0.50 7* 1712.67070 2.70 1.53110 55.91 8* -31.84183 D2 Image plane ∞

[0145] In this eyepiece optical system EL7, surfaces 1, 2, 3, 6, 7, and 8 are aspheric. Table 26 below shows data on the aspheric surfaces, that is, the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0146] (Table 26) [Aspheric data] Front page K=-2.0140 A4 =-1.26801E-04 A6 =-7.92018E-07 A8 = 1.72033E-08 A10=-1.32394E-10 A12= 5.48090E-13 2nd side K=-2.1884 A4 =-1.51405E-04 A6 = 8.63584E-07 A8 =-7.98722E-09 A10= 2.78537E-11 A12= 0.00000E+00 3rd page K=-0.1010 A4 = 3.80395E-04 A6 = -4.01258E-06 A8 = 2.22431E-08 A10=-1.81820E-10 A12= 0.00000E+00 Page 6 K = 0.6429 A4 = 2.44680E-04 A6 =-7.34170E-07 A8 =-4.17875E-09 A10= 2.11837E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.23377E-04 A6 = 1.23089E-06 A8 =-5.34263E-09 A10= 3.90858E-11 A12= 0.00000E+00 Side 8 K=-0.0905 A4 =-2.34359E-04 A6 = 2.48218E-06 A8 =-1.41661E-08 A10= 7.75465E-11 A12= 0.00000E+00

[0147] In this eyepiece optical system EL7, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 27 below shows the variable distances and entrance pupil positions for each diopter.

[0148] (Table 27) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 6.62 7.55 5.61 D2 20.10 19.17 21.11 EnP -30.15672 -31.88364 -28.53315

[0149] Table 28 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL7.

[0150] (Table 28) f4 = 58.892 f12= ​​34.529 f23=-45.926 [Conditional expression corresponding value] (1) fe / f1=1.562 (2) fe / f12 = 0.512 (3)νd2=23.89 (4) fe / f4 = 0.300 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.075 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.449 (7)fe / EnP=-0.586 (8)fe / f23=-0.385 (9) D1 / f1=0.586 (10)TL / fe=1.603 (11)nd1=1.744 (12)nd2=1.636

[0151] In this way, the eyepiece optical system EL7 satisfies the above conditional expressions (1) to (11).

[0152] 14 shows diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL7 at the reference diopter (-1 dpt). These aberration diagrams show that this eyepiece optical system EL7 achieves good aberration correction within the diopter adjustment range.

[0153] [Eighth Example] 15 is a diagram showing the configuration of an eyepiece optical system EL8 according to Example 8. This eyepiece optical system EL8 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0154] In this eyepiece optical system EL8, the first lens component G1 is composed of a cemented lens formed by cementing together an aspherical positive lens L11 having a biconvex positive lens shape with an aspherical lens surface on the observation object side and an aspherical positive lens L12 having a positive meniscus lens shape with an aspherical lens surface on the eye point side and a concave surface on the observation object side. The second lens component G2 is composed of an aspherical negative lens L12 having an aspherical lens surface on the observation object side and a negative meniscus lens shape with a concave surface on the observation object side. The third lens component G3 is composed of an aspherical positive lens L31 having an aspherical lens surface on the eye point side and a positive meniscus lens shape with a concave surface on the observation object side. The fourth lens component G4 is composed of an aspherical positive lens L41 having an aspherical lens surface on the observation object side and an aspherical lens surface on the eye point side and a positive meniscus lens shape with a concave surface on the observation object side.

[0155] The diopter adjustment in the eyepiece optical system EL8 is performed by moving the entire eyepiece optical system EL8 in the optical axis direction.

[0156] Table 29 below lists the specifications of the eyepiece optical system EL8.

[0157] Table 29: Example 8 [Overall specifications] fe = 17.671 H = 6.30 TL = 28.340 [Lens data] mrd nd νd Object surface ∞ D1 1* 36.28535 1.50 1.75520 27.57 2 -256.85195 5.55 1.74400 44.80 3* -9.58387 2.70 4* -6.33627 1.60 1.63550 23.89 5 -309.22499 1.00 6 -340.41004 5.95 1.53110 55.91 7* -10.20313 0.50 8* -118.11140 2.70 1.53110 55.91 9* -33.13998 D2 Image plane ∞

[0158] In this eyepiece optical system EL8, surfaces 1, 3, 4, 7, 8 and 9 are formed aspheric. Table 30 below shows data on the aspheric surfaces, that is, the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0159] (Table 30) [Aspheric data] Front page K=-2.0658 A4 =-1.42501E-04 A6 =-8.76658E-07 A8 = 1.88394E-08 A10=-1.09268E-10 A12= 3.68460E-13 3rd page K=-1.7532 A4 =-1.52859E-04 A6 = 8.23715E-07 A8 =-8.45101E-09 A10= 3.67563E-11 A12= 0.00000E+00 Side 4 K=-0.2498 A4 = 3.64026E-04 A6 = -4.01765E-06 A8 = 2.07275E-08 A10=-1.61058E-10 A12= 0.00000E+00 Side 7 K = 0.5740 A4 = 2.54149E-04 A6 =-6.32718E-07 A8 =-3.76424E-09 A10= 2.73994E-11 A12= 0.00000E+00 Side 8 K = 1.0000 A4 =-1.19587E-04 A6 = 1.18521E-06 A8 =-5.01478E-09 A10= 4.10280E-11 A12= 0.00000E+00 9th page K = 1.4393 A4 =-2.39375E-04 A6 = 2.51700E-06 A8 =-1.48286E-08 A10= 7.54336E-11 A12= 0.00000E+00

[0160] In this eyepiece optical system EL8, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 31 below shows the variable distances and entrance pupil positions for each diopter.

[0161] (Table 31) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 6.84 7.77 5.83 D2 20.10 19.17 21.11 EnP -31.23485 -33.09550 -29.49620

[0162] Table 32 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL8.

[0163] (Table 32) f4 = 85.790 f12= ​​37.994 f23=-57.363 [Conditional expression corresponding value] (1) fe / f1=1.625 (2) fe / f12 = 0.465 (3)νd2=23.89 (4) fe / f4 = 0.206 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.048 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.582 (7)fe / EnP=-0.566 (8)fe / f23=-0.308 (9) D1 / f1=0.629 (10)TL / fe=1.604 (11)nd1=1.755 (12)nd2=1.636

[0164] In this way, the eyepiece optical system EL8 satisfies the above conditional expressions (1) to (11).

[0165] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL8 at the reference diopter (-1 dpt) are shown in Figure 16. These aberration diagrams show that this eyepiece optical system EL8 achieves good aberration correction within the diopter adjustment range.

[0166] [Ninth Example] 17 is a diagram showing the configuration of an eyepiece optical system EL9 according to Example 9. This eyepiece optical system EL9 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0167] In this eyepiece optical system EL9, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric. The second lens component G2 is composed of an aspherical negative lens L12 having an aspherical negative meniscus lens shape with the concave surface facing the observation object side. The third lens component G3 is composed of an aspherical positive lens L31 having an aspherical positive meniscus lens shape with the lens surface on the eye point side formed aspheric. The fourth lens component G4 is composed of an aspherical positive lens L41 having an aspherical positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspheric.

[0168] The diopter adjustment in the eyepiece optical system EL9 is performed by moving the entire eyepiece optical system EL9 in the direction of the optical axis.

[0169] Table 33 below lists the specifications of the eyepiece optical system EL9.

[0170] Table 33: 9th Example [Overall specifications] fe = 17.664 H = 6.30 TL = 28.440 [Lens data] mrd nd νd Object surface ∞ D1 1* 30.06223 7.30 1.74300 49.25 2* -10.46380 2.70 3* -6.62848 1.55 1.65093 21.51 4 -43.12860 1.00 5 -44.49530 5.95 1.53110 55.91 6* -10.78420 0.50 7* -1133.34000 2.70 1.53110 55.91 8* -34.07780 D2 Image plane ∞

[0171] In this eyepiece optical system EL9, surfaces 1, 2, 3, 6, 7, and 8 are aspheric. Table 34 below shows data on the aspheric surfaces, that is, the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0172] (Table 34) [Aspheric data] Front page K=-1.3191 A4 =-1.08297E-04 A6 =-5.23642E-07 A8 = 1.65142E-08 A10=-1.39777E-10 A12= 5.22770E-13 2nd side K=-2.1775 A4 =-1.37725E-04 A6 = 9.31664E-07 A8 =-7.77285E-09 A10= 2.31975E-11 A12= 0.00000E+00 3rd page K=-0.0873 A4 = 3.71838E-04 A6 = -4.12160E-06 A8 = 2.25930E-08 A10=-1.98410E-10 A12= 0.00000E+00 Page 6 K = 0.6318 A4 = 2.37664E-04 A6 =-7.12383E-07 A8 =-4.02440E-09 A10= 2.46401E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.19476E-04 A6 = 1.21154E-06 A8 =-5.10047E-09 A10= 4.12044E-11 A12= 0.00000E+00 Side 8 K=-0.6189 A4 =-2.32309E-04 A6 = 2.50741E-06 A8 =-1.40702E-08 A10= 7.88020E-11 A12= 0.00000E+00

[0173] In this eyepiece optical system EL9, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eyepoint EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 35 below shows the variable distances and entrance pupil positions for each diopter.

[0174] (Table 35) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 6.74 7.67 5.73 D2 20.00 19.07 20.01 EnP -31.17085 -32.51888 -29.03853

[0175] Table 36 below shows the corresponding values ​​of each conditional expression for this eyepiece optical system EL9.

[0176] (Table 36) f4 = 66.097 f12= ​​29.977 f23=-51.032 [Conditional expression corresponding value] (1) fe / f1=1.561 (2) fe / f12=0.589 (3)νd2=21.51 (4) fe / f4=0.267 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.016 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.484 (7)fe / EnP=-0.567 (8)fe / f23=-0.346 (9) D1 / f1=0.596 (10)TL / fe=1.610 (11)nd1=1.743 (12)nd2=1.651

[0177] In this way, the eyepiece optical system EL9 satisfies the above conditional expressions (1) to (12).

[0178] Diagrams of spherical aberration, astigmatism, distortion and coma of this eyepiece optical system EL9 at the reference diopter (-1 dpt) are shown in Figure 18. These aberration diagrams show that this eyepiece optical system EL9 achieves good aberration correction within the diopter adjustment range.

[0179] [Tenth Example] 19 is a diagram showing the configuration of an eyepiece optical system EL10 according to Example 10. This eyepiece optical system EL10 is configured to include, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0180] In this eyepiece optical system EL10, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape in which the lens surface on the observation object side and the lens surface on the eye point side are formed aspherically. The second lens component G2 is composed of an aspherical negative lens L21 having an aspherical negative meniscus lens shape with a concave surface facing the observation object side, and the lens surface on the observation object side and the lens surface on the eye point side are formed aspherically. The third lens component G3 is composed of an aspherical positive lens L31 having an aspherical positive meniscus lens shape with a concave surface facing the observation object side, and the lens surface on the observation object side and the lens surface on the eye point side are formed aspherically. The fourth lens component G4 is composed of an aspherical positive lens L41 having an aspherical positive meniscus lens shape with a concave surface facing the observation object side, and the lens surface on the observation object side and the lens surface on the eye point side are formed aspherically.

[0181] The diopter adjustment in the eyepiece optical system EL10 is performed by moving the entire eyepiece optical system EL10 in the optical axis direction.

[0182] Table 37 below lists the specifications of the eyepiece optical system EL10.

[0183] Table 37: 10th Example [Overall specifications] fe = 17.655 H = 6.30 TL = 28.870 [Lens data] mrd nd νd Object surface ∞ D1 1* 27.64520 7.35 1.74300 49.25 2* -10.59980 2.70 3* -6.62160 1.50 1.66133 20.35 4* -30.41490 1.00 5* -33.42740 5.95 1.53110 55.91 6* -11.06910 0.50 7* -447.12000 2.70 1.53110 55.91 8* -33.61500 D2 Image plane ∞

[0184] In this eyepiece optical system EL10, surfaces 1, 2, 3, 4, 5, 6, 7, and 8 are aspheric. Table 38 below shows data on the aspheric surfaces, i.e., the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0185] (Table 38) [Aspheric data] Front page K = 1.8706 A4 =-1.58806E-04 A6 =-6.47977E-07 A8 = 2.00513E-08 A10=-1.19924E-10 A12= 3.39780E-13 2nd side K=-2.5122 A4 =-1.82235E-04 A6 = 1.26664E-06 A8 =-9.55146E-09 A10= 4.41287E-11 A12= 0.00000E+00 3rd page K=-0.1010 A4 = 3.59553E-04 A6 = -3.81376E-06 A8 = 2.31702E-08 A10=-1.65901E-10 A12= 0.00000E+00 Side 4 K = 1.2085 A4 = 9.08220E-06 A6 = 4.92684E-09 A8 = 2.99069E-11 A10= 0.00000E+00 A12= 0.00000E+00 5th page K=-0.6362 A4 = 2.08532E-05 A6 = 3.39041E-08 A8 =-4.09295E-10 A10= 0.00000E+00 A12= 0.00000E+00 Page 6 K = 0.5759 A4 = 2.44689E-04 A6 =-6.87340E-07 A8 =-4.20734E-09 A10= 2.20759E-11 A12= 0.00000E+00 Side 7 K = 1.0000 A4 =-1.28197E-04 A6 = 1.23524E-06 A8 =-5.32987E-09 A10= 3.98596E-11 A12= 0.00000E+00 Side 8 K = 0.3803 A4 =-2.29306E-04 A6 = 2.47452E-06 A8 =-1.42769E-08 A10= 7.86334E-11 A12= 0.00000E+00

[0186] In this eyepiece optical system EL10, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eyepoint EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 39 below shows the variable distances and entrance pupil positions for each diopter.

[0187] (Table 39) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.17 8.10 6.16 D2 20.10 19.17 21.11 EnP -30.13523 -31.77608 -28.58721

[0188] Table 40 below shows the corresponding values ​​of each conditional expression of this eyepiece optical system EL10.

[0189] (Table 40) f4 = 68.284 f12= ​​26.280 f23=-47.435 [Conditional expression corresponding value] (1) fe / f1 = 1.572 (2) fe / f12 = 0.672 (3)νd2=20.35 (4) fe / f4=0.259 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.047 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.446 (7)fe / EnP=-0.586 (8)fe / f23=-0.372 (9) D1 / f1=0.638 (10)TL / fe=1.635 (11)nd1=1.743 (12)nd2=1.661

[0190] In this way, the eyepiece optical system EL10 satisfies the above conditional expressions (1) to (12).

[0191] Diagrams of spherical aberration, astigmatism, distortion, and coma of this eyepiece optical system EL10 at the reference diopter (-1 dpt) are shown in Figure 20. These aberration diagrams show that this eyepiece optical system EL10 achieves good aberration correction within the diopter adjustment range.

[0192] [Eleventh Example] 21 is a diagram showing the configuration of an eyepiece optical system EL11 according to Example 11. This eyepiece optical system EL11 is configured to have, in order from the observation object side, a first lens component G1 having positive refractive power, a second lens component G2 having negative refractive power, a third lens component G3 having positive refractive power, and a fourth lens component G4 having positive refractive power.

[0193] In this eyepiece optical system EL11, the first lens component G1 is composed of an aspherical positive lens L11 having a biconvex positive lens shape with the lens surface on the observation object side formed aspherically. The second lens component G2 is composed of a cemented lens in which an aspherical negative lens L21 having a biconcave negative lens shape with the lens surface on the observation object side formed aspherically and an aspherical positive lens L22 having a biconvex positive lens shape with the lens surface on the eye point side formed aspherically. The third lens component G3 is composed of an aspherical positive lens L31 having a positive meniscus lens shape with the lens surface on the eye point side formed aspherically and the concave surface facing the observation object side. The fourth lens component G4 is composed of an aspherical positive lens L41 having a positive meniscus lens shape with the lens surface on the observation object side and the lens surface on the eye point side formed aspherically and the concave surface facing the observation object side.

[0194] The diopter adjustment in the eyepiece optical system EL11 is performed by moving the entire eyepiece optical system EL11 in the optical axis direction.

[0195] Table 41 below lists the specifications of the eyepiece optical system EL11.

[0196] Table 41: 11th Example [Overall specifications] fe = 17.623 H = 6.30 TL = 30.240 [Lens data] mrd nd νd Object surface ∞ D1 1* 28.78836 7.35 1.82098 42.50 2 -11.25246 2.70 3* -7.11620 1.50 1.63550 23.89 4 564.01019 1.48 1.53110 55.91 5* -165.33547 1.00 6 -397.01843 5.95 1.53110 55.91 7* -11.70908 0.5 8* -87.51711 2.70 1.53110 55.91 9* -33.70935 D2 Image plane ∞

[0197] In this eyepiece optical system EL11, surfaces 1, 3, 5, 7, 8, and 9 are formed aspheric. Table 42 below shows data on the aspheric surfaces, that is, the conic constant K and the values ​​of each of the aspheric constants A4 to A12.

[0198] (Table 42) [Aspheric data] Front page K = 4.9064 A4 =-1.05219E-04 A6 =-6.21990E-07 A8 = 1.81446E-08 A10=-1.14918E-10 A12= 3.47790E-13 3rd page K=-2.7141 A4 =-1.22865E-04 A6 = 1.06684E-06 A8 =-6.77704E-09 A10= 4.48572E-11 A12= 0.00000E+00 5th page K=-0.1268 A4 = 3.96618E-04 A6 = -3.89261E-06 A8 = 2.32375E-08 A10=-1.45358E-10 A12= 0.00000E+00 Side 7 K = 0.5892 A4 = 2.52841E-04 A6 =-6.99186E-07 A8 =-4.09567E-09 A10= 2.38163E-11 A12= 0.00000E+00 Side 8 K = 1.0000 A4 =-1.15871E-04 A6 = 1.20055E-06 A8 =-5.20908E-09 A10= 4.32497E-11 A12= 0.00000E+00 9th page K = 2.7036 A4 =-2.43083E-04 A6 = 2.51325E-06 A8 =-1.39088E-08 A10= 7.50477E-11 A12= 0.00000E+00

[0199] In this eyepiece optical system EL11, the axial air distance D1 between the object to be observed and the first lens component G1, and the axial air distance D2 between the fourth lens component G4 and the eye point EP change during diopter adjustment. The entrance pupil position EnP also changes with the change in these distances. Table 43 below shows the variable distances and entrance pupil positions for each diopter.

[0200] (Table 43) [Variable interval data] Diopter -1dpt +2dpt -4dpt D1 7.06 7.98 6.04 D2 20.10 19.18 21.12 EnP -27.40929 -28.67303 -26.17269

[0201] Table 44 below shows the corresponding values ​​of each conditional expression of this eyepiece optical system EL11.

[0202] (Table 44) f4 =101.468 f12= ​​26.176 f23=-66.090 [Conditional expression corresponding value] (1) fe / f1=1.640 (2) fe / f12 = 0.673 (3)νd2=23.89 (4) fe / f4 = 0.174 (5)(G2R2-G3R1) / (G2R2+G3R1)=-0.412 (6)(G1R2+G1R1) / (G1R2-G1R1)=-0.438 (7)fe / EnP=-0.643 (8)fe / f23=-0.267 (9) D1 / f1=0.657 (10)TL / fe=1.716 (11)nd1=1.821 (12)nd2=1.636

[0203] In this way, the eyepiece optical system EL11 satisfies the above conditional expressions (1) to (4) and (6) to (11).

[0204] Diagrams of spherical aberration, astigmatism, distortion and coma of this eyepiece optical system EL11 at the reference diopter (-1 dpt) are shown in Figure 22. These aberration diagrams show that this eyepiece optical system EL11 achieves good aberration correction within the diopter adjustment range.

[0205] The contents described below can be appropriately adopted as long as they do not impair optical performance.

[0206] In this embodiment, a configuration with four lens components has been shown as a numerical example of the eyepiece optical system EL, but other lens configurations, such as five lens components, can also be used. Also, a configuration in which a lens component is added closest to the object side, or a configuration in which a lens component is added closest to the eye point side, may be used.

[0207] Alternatively, a single or multiple lens components may be moved so as to have a displacement component perpendicular to the optical axis, or rotated (rocked) in a plane including the optical axis to form an anti-vibration lens group that corrects image blur caused by camera shake. It is particularly preferable to form the third lens component G3 as an anti-vibration lens group.

[0208] In addition, the lens surface of the lens (lens component, lens element) constituting the eyepiece optical system EL of this embodiment may be spherical or flat, or may be aspheric. If the lens surface is spherical or flat, lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in lens processing and assembly adjustment can be prevented, which is preferable. In addition, even if the image plane is shifted, deterioration of depiction performance is small, which is preferable. If the lens surface is aspheric, it may be an aspheric surface formed by grinding, a glass molded aspheric surface formed by molding glass into an aspheric shape using a mold, or a composite aspheric surface formed by forming a resin provided on the surface of glass into an aspheric shape. In addition, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0209] In addition, the lens surfaces of the lenses (lens components, lens elements) that make up the eyepiece optical system EL of this embodiment may be coated with an anti-reflection coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high optical performance with high contrast.

[0210] In addition, the eyepiece optical system EL of this embodiment is configured such that the first lens component G1, the second lens component G2, the third lens component G3, and the fourth lens component G4 move together, or the entire eyepiece optical system EL moves together to adjust the diopter, but the lens component closest to the eyepoint may be fixed, and the entire lens components closer to the observation object than the lens component may be moved together, or at least some of the lens components among the first lens component G1, the second lens component G2, the third lens component G3, and the fourth lens component G4 may be moved. In particular, it is preferable to move the first lens component G1, and fix the positions of the other lens components relative to the image plane during diopter adjustment. It is preferable that the diopter adjustment lens group is composed of a single lens. [Explanation of symbols]

[0211] EL (EL1~EL11) eyepiece optical system G1 First lens component G2 Second lens component G3 3rd lens component G4 4th lens component 1. Camera (optical device)

Claims

1. From the observation object side, a first lens having a positive refractive power; a second lens having a negative refractive power; a third lens having a positive refractive power; a fourth lens having a positive refractive power; An eyepiece optical system that satisfies the following condition: 1.700 < nd1 < 1.800 1.38 < fe / f1 < 1.65 however, nd1: refractive index of the medium of the first lens with respect to the d line fe: focal length of the entire eyepiece optical system f1: focal length of the first lens

2. From the observation object side, a first lens having a positive refractive power; a second lens having a negative refractive power; a third lens having a positive refractive power; a fourth lens having a positive refractive power; An eyepiece optical system that satisfies the following condition: 1.700 < nd1 < 1.800 0.48 < fe / f12 < 3.00 -0.30 < (G2R2-G3R1) / (G2R2+G3R1) ≦ 0.102 however, nd1: refractive index of the medium of the first lens with respect to the d line fe: focal length of the entire eyepiece optical system f12: composite focal length of the first lens and the second lens G2R2: radius of curvature of the lens surface of the second lens closest to the eyepoint G3R1: radius of curvature of the lens surface of the third lens closest to the observation object

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