JP2014056021A - Ocular lens system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ocular lens system which offers superior optical performance by correcting aberrations well over a wide field of view.SOLUTION: The ocular lens system comprises a first lens group having negative refractive power, a field stop, and a second lens group having positive refractive power arranged in order from the object side. The first lens group comprises a negative lens and a positive lens located in order from the object side cemented together. The ocular lens system satisfies conditional expressions (1) and (2): (1) -9.5<f1/f2<-2.5, (2) |ν1n-ν1p|>40; where f1 represents a focal length of the first lens group, f2 represents a focal length of the second lens group, ν1n represents an Abbe number of the negative lens of the first lens group for d-ray, and ν1p represents an Abbe number of the positive lens of the first lens group for d-ray.

Description

  The present invention relates to an eyepiece lens system used in combination with an objective lens system of binoculars or a telescope.

  Patent Documents 1-3 include, in order from the objective side, a first lens group (field flatner) having a negative refractive power, a field stop, and a second lens group having a positive refractive power. An eyepiece system in which (Field Flatner) is a cemented lens of a negative lens and a positive lens is disclosed. In this type of eyepiece lens system, in order to correct field curvature and astigmatism, the first lens group (field flattener) is disposed on the object side of the field stop to reduce the Petzval sum.

  However, in the eyepiece system disclosed in Patent Documents 1-3, since the refractive power of the first lens group (field flatner) is too strong, off-axis aberrations (astigmatism and coma) can be corrected in the second lens group. Have difficulty. In particular, since the astigmatism in the meridional direction at the outermost periphery is large, the edge of the field stop is blurred when looking into the eyepiece lens system.

  In the eyepiece system disclosed in Patent Documents 1-3, the Abbe number for the d-line of the negative lens and the positive lens constituting the first lens group (field flatner) is inappropriate. For this reason, the burden of correcting the chromatic aberration (axial chromatic aberration, lateral chromatic aberration) of the second lens group becomes large, and color blur occurs at the edge of the field stop, for example.

JP 2008-15418 A Japanese Patent No. 3518704 Japanese Patent Laid-Open No. 6-109983

  The present invention has been made based on the above awareness of the problem, and an object of the present invention is to obtain an eyepiece system that can satisfactorily correct various aberrations over a wide field of view and achieve excellent optical performance.

An eyepiece lens system according to the present invention is an eyepiece lens system including a first lens unit having a negative refractive power, a field stop, and a second lens group having a positive refractive power in order from the objective side. It consists of a cemented lens of a negative lens and a positive lens positioned in order from the objective side, and satisfies the following conditional expressions (1) and (2).
(1) -9.5 <f1 / f2 <-2.5
(2) | ν1n−ν1p |> 40
However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group,
ν1n: Abbe number with respect to d-line of the negative lens in the first lens group,
ν1p: Abbe number of the positive lens in the first lens group with respect to the d-line,
It is.

The eyepiece system of the present invention preferably satisfies the following conditional expression (3).
(3) | N1n-N1p |> 0.07
However,
N1n: the refractive index of the negative lens in the first lens group with respect to the d-line,
N1p: refractive index of the positive lens in the first lens group with respect to the d-line,
It is.

The eyepiece system of the present invention preferably satisfies the following conditional expression (4).
(4) 0.4 <(D3 + D4) / f <0.7
However,
D3: an air space between the most eye-side surface of the first lens unit and the field stop,
D4: the air space between the field stop and the most objective surface of the second lens group,
f: focal length of the entire system,
It is.

  The first lens group is preferably composed of a cemented lens of a biconcave negative lens positioned in order from the object side and a positive lens having a convex surface directed to the object side.

  The second lens group includes, in order from the objective side, a cemented lens having a positive refractive power in which a negative lens having a concave surface facing the objective side and a positive lens having a convex surface facing the eye side are cemented from the objective side. It can be composed of a biconvex positive lens positioned in sequence, a cemented lens having a positive refractive power in which a negative lens having a concave surface facing the object side is cemented, and a positive lens having a concave surface facing the eye side.

  Alternatively, the second lens group includes, in order from the objective side, a positive lens in which a positive lens having a concave surface directed toward the objective side, a biconvex positive lens positioned in order from the objective side, and a negative lens having a concave surface directed toward the objective side are joined. It is also possible to configure the lens with a positive lens having a concave surface facing the eye side.

In another aspect, the eyepiece lens system of the present invention is an eyepiece system comprising, in order from the objective side, a first lens unit having a negative refractive power, a field stop, and a second lens group having a positive refractive power. The first lens group is composed of a cemented lens of a negative lens and a positive lens positioned in order from the objective side, and satisfies the following conditional expression (2).
(2) | ν1n−ν1p |> 40
However,
ν1n: Abbe number with respect to d-line of the negative lens in the first lens group,
ν1p: Abbe number of the positive lens in the first lens group with respect to the d-line,
It is.

  According to the present invention, it is possible to obtain an eyepiece system that can satisfactorily correct various aberrations over a wide field of view and achieve excellent optical performance.

It is a lens block diagram of Numerical Example 1 of the eyepiece lens system according to the present invention. FIG. 2 is a diagram illustrating various aberrations in the configuration of FIG. 1. It is a lens block diagram of Numerical Example 2 of the eyepiece lens system according to the present invention. FIG. 4 is a diagram illustrating various aberrations in the configuration of FIG. 3. It is a lens block diagram of Numerical Example 3 of the eyepiece lens system according to the present invention. FIG. 6 is a diagram illustrating various aberrations in the configuration of FIG. 5. It is a lens block diagram of numerical Example 4 of the eyepiece lens system by this invention. FIG. 8 is a diagram illustrating various aberrations in the configuration of FIG. 7. It is a lens block diagram of Numerical Example 5 of the eyepiece system according to the present invention. FIG. 10 is a diagram of various aberrations in the configuration of FIG. 9. It is a lens block diagram of Numerical Example 6 of the eyepiece lens system according to the present invention. FIG. 12 is a diagram illustrating various aberrations in the configuration of FIG. 11. It is a lens block diagram of Numerical Example 7 of the eyepiece lens system according to the present invention. FIG. 14 is a diagram illustrating various aberrations in the configuration of FIG. 13. It is a lens block diagram of Numerical Example 8 of the eyepiece lens system according to the present invention. FIG. 16 is a diagram illustrating various aberrations in the configuration of FIG. 15.

  The eyepiece lens system of the present embodiment has an objective side (objective) as shown in Numerical Examples 1-8 in FIGS. 1, 3, 5, 7, 9, 11, 13, and 15. In order from the lens system side), the first lens group (field flattener) G1 having a negative refractive power, a field stop S, and a second lens group G2 having a positive refractive power. An intermediate image by an objective lens system (not shown) is formed at the position of the field stop S between the first lens group G1 and the second lens group G2.

  The first lens group G1 includes a cemented lens of a biconcave negative lens 11 and a positive lens (a positive lens having a convex surface directed toward the object side) 12 which are sequentially arranged from the object side, through all numerical value examples 1-8. The positive lens 12 is a positive meniscus lens convex toward the objective side in Numerical Example 1-5, and is a biconvex positive lens in Numerical Example 6-8.

  In Numerical Example 1-5, the second lens group G2 includes a biconcave negative lens (a negative lens having a concave surface directed toward the objective side) 21 and a biconvex positive lens (eye side) sequentially from the objective side. A positive lens having a positive refractive power, a birefringent positive lens 23 positioned in order from the objective side, and a negative meniscus lens convex to the eye side (a negative lens having a concave surface facing the objective side) ) 24 and a positive refractive power cemented lens, and a positive meniscus lens convex on the objective side (a positive lens with a concave surface facing the eye).

  In Numerical Example 6-8, the second lens group G2 includes, in order from the objective side, a positive meniscus lens 21 ′ convex to the eye side (a positive lens having a concave surface directed toward the objective side) 21 ′, and biconvex positioned in order from the objective side. A cemented lens having a positive refractive power obtained by cementing a positive lens 23 and a negative meniscus lens convex to the eye side (a negative lens having a concave surface facing the objective side), and a positive meniscus lens convex to the objective side (a concave surface facing the eye side). Positive lens) 25.

  In the eyepiece system of the present embodiment, the first lens group G1 includes a biconcave negative lens 11 positioned in order from the objective side and a positive lens with a convex surface facing the objective side (a positive meniscus lens convex to the objective side or a biconvex positive lens). Lens) 12 cemented lenses. Thereby, the Petzval sum can be reduced on the diverging surface of the first lens group G1, and the field curvature and astigmatism can be corrected well. Further, chromatic aberration can be favorably corrected by selecting an appropriate glass.

  In order to satisfactorily correct various aberrations (astigmatism, coma, curvature of field, spherical aberration, distortion, axial chromatic aberration, lateral chromatic aberration, etc.) in the entire eyepiece system, the first lens group G1 and the second lens group It is necessary to appropriately balance the aberration of the lens group G2, and the lens configuration of the second lens group G2 is particularly important.

  Therefore, in the eyepiece lens system of the present embodiment, the second lens group G2 is made up of three lens groups each having a positive power (that is, “a lens having a positive refractive power in front of a positive refractive power composed of a cemented lens of the lens 21 and the lens 22 or the lens 21 ′” Group ”,“ medium group of positive refractive power ”composed of a cemented lens of lens 23 and lens 24, and“ back group of positive refractive power ”composed of lens 25).

  The Petzval sum can be further reduced by making the most object side surface of the “front group of positive refractive power” of the second lens group G2 concave on the object side.

  In addition, the “middle group of positive refractive power” of the second lens group G2 includes a biconvex positive lens 23 positioned in order from the objective side and a negative meniscus lens (negative lens with a concave surface facing the objective side) 24 convex toward the eye side. Astigmatism, coma, and spherical aberration can be satisfactorily corrected by using a cemented lens having a positive refractive power.

  Further, the “second group of positive refractive power” of the second lens group G2 is composed of a positive meniscus lens convex to the objective side (a positive lens having a concave surface facing the eye side), thereby improving coma and distortion. It can be corrected.

Conditional expression (1) defines the ratio (power balance) of the focal lengths of the first lens group G1 and the second lens group G2. By satisfying conditional expression (1), the diameter of the second lens group G2 can be reduced, and astigmatism, coma aberration, and field curvature can be corrected well.
When the upper limit of conditional expression (1) is exceeded, the power of the first lens group G1 becomes too strong, and the incident height of the light beam to the second lens group G2 increases due to the diverging action of the first lens group G1, Correction of point aberration and coma becomes difficult. In particular, since the astigmatism in the meridional direction at the outermost periphery is large, the edge of the field stop S is blurred when looking into the eyepiece lens system. In addition, the lens diameter of the second lens group G2 increases.
If the lower limit of conditional expression (1) is exceeded, the power of the first lens group G1 becomes too weak and the Petzval sum increases in the positive direction, making it difficult to correct field curvature.

Conditional expression (2) defines the Abbe number difference between the negative lens 11 and the positive lens 12 constituting the first lens group G1 with respect to the d-line. By satisfying conditional expression (2), axial chromatic aberration and lateral chromatic aberration can be corrected well.
If the lower limit of conditional expression (2) is exceeded, the burden of correcting the longitudinal chromatic aberration and lateral chromatic aberration of the second lens group G2 will increase, and color blur will occur at the edge of the field stop S, for example.

Conditional expression (3) defines the difference in refractive index between the negative lens 11 and the positive lens 12 constituting the first lens group G1 with respect to the d-line. By satisfying conditional expression (3), coma can be corrected well, and, for example, when used in combination with an objective lens system of binoculars, it is possible to prevent inconvenience such that dust is easily visible.
When the lower limit of conditional expression (3) is exceeded, the curvature of the cemented surface of the negative lens 11 and the positive lens 12 becomes too large to correct axial chromatic aberration, and off-axis coma increases. Further, when the lens thickness of the positive lens 12 is increased in order to secure the edge of the positive lens 12 that can be processed, the thickness of the first lens group G1 increases. For example, when combined with an objective lens system of binoculars, This is not preferable because the distance between the two becomes closer and it becomes easier to see dust.

Conditional expression (4) defines the ratio between the air distance between the first lens group G1 and the second lens group G2 and the focal length of the entire system. Satisfying conditional expression (4) makes the eyepiece lens system compact, corrects various off-axis aberrations (especially coma), and maintains image flatness (field curvature). In addition, it is possible to secure the length to the eye point, and to prevent defects such as scratches and dust on the lens surface and the observation image.
If the upper limit of conditional expression (4) is exceeded, the light rays incident on the second lens group G2 will become high, and off-axis aberrations (particularly coma aberration) will be undercorrected. In addition, the total length of the eyepiece lens system is increased and the lens diameter is increased, which is not preferable because the compactness is lost.
If the lower limit of conditional expression (4) is exceeded, the combined focal length of the first lens group G1 and the second lens group G2 becomes small, so that the Petzval sum increases and the flatness of the image deteriorates. Further, the focal length of the second lens group G2 becomes short, and the length to the eye point becomes insufficient. Furthermore, since the air space between the first lens group G1 and the second lens group G2 is narrowed and each lens group approaches the image plane, scratches and dust on the lens surface can be seen together with the observation image, which is not preferable.

  Next, specific numerical examples 1-8 will be described. In the aberration diagrams and tables, d-line, g-line, and C-line are the aberrations for each wavelength, S is sagittal, M is meridional, f is the focal length of the entire system, B is the exit angle (half angle) (°), ER is the pupil diameter, R is the radius of curvature, d is the lens thickness or lens interval, N (d) is the refractive index for the d-line, and ν (d) is the Abbe number for the d-line. The unit of length is [mm]. Throughout the numerical examples 1-8, no aspheric lens is used. The intermediate image position is the position of an object point when a light beam of −1 diopter is emitted from the eyepiece lens system.

[Numerical Example 1]
1 to 2 and Table 1 to Table 2 show Numerical Example 1 of an eyepiece system according to the present invention. FIG. 1 is a lens configuration diagram, and FIG. Table 1 shows surface data, and Table 2 shows various data.

  The eyepiece lens system of Numerical Example 1 includes, in order from the objective side, a first lens group G1 having a negative refractive power, a field stop S, and a second lens group G2 having a positive refractive power. An intermediate image by an objective lens system (not shown) is formed at the position of the field stop S between the first lens group G1 and the second lens group G2.

  The first lens group G1 is composed of a cemented lens of a biconcave negative lens 11 positioned in order from the objective side and a positive meniscus lens 12 (positive lens with a convex surface facing the objective side) convex toward the objective side.

  The second lens group G2 includes, in order from the object side, a biconcave negative lens (a negative lens having a concave surface facing the object side) 21 and a biconvex positive lens (a positive lens having a convex surface facing the eye side) sequentially from the object side. 22 is a positive refractive power in which a cemented lens having a positive refractive power, a biconvex positive lens 23 positioned in order from the object side, and a negative meniscus lens 24 convex to the eye side (a negative lens having a concave surface facing the object side) are cemented. It consists of a cemented lens of force and a positive meniscus lens (positive lens with a concave surface facing the eye) 25 convex toward the objective side.

(Table 1)
Surface data surface number R d N (d) ν (d)
1 -28.928 1.500 1.49700 81.6
2 26.651 2.809 1.57501 41.5
3 129.709 3.494
4 stops ∞ 6.843
5 -66.428 1.500 1.84666 23.8
6 30.895 8.610 1.77250 49.6
7 -23.506 1.000
8 103.137 10.000 1.75700 47.8
9 -22.513 2.000 1.84666 23.8
10 -75.974 1.000
11 20.261 5.000 1.80 400 46.6
12 45.423-
(Table 2)
Various data
f 16.19
B 28.4
ER φ4.2
Eye relief 21.00

[Numerical Example 2]
3 to 4 and Table 3 to Table 4 show Numerical Example 2 of the eyepiece system according to the present invention. FIG. 3 is a lens configuration diagram, and FIG. Table 3 shows surface data, and Table 4 shows various data.

  The lens configuration of Numerical Example 2 is the same as the lens configuration of Numerical Example 1.

(Table 3)
Surface data surface number R d N (d) ν (d)
1 -44.216 1.500 1.49700 81.6
2 37.025 3.120 1.92286 18.9
3 63.460 3.758
4 stops ∞ 5.799
5 -35.584 1.500 1.84666 23.8
6 40.381 8.610 1.77250 49.6
7 -21.710 1.000
8 85.296 10.000 1.75700 47.8
9 -20.753 2.000 1.84666 23.8
10 -57.615 1.000
11 19.671 5.000 1.80 400 46.6
12 40.537-
(Table 4)
Various data
f 16.17
B 31.1
ER φ4.2
Eye relief 21.00

[Numerical Example 3]
5 to 6 and Table 5 to Table 6 show Numerical Example 3 of the eyepiece system according to the present invention. FIG. 5 is a lens configuration diagram, and FIG. Table 5 shows surface data, and Table 6 shows various data.

  The lens configuration of Numerical Example 3 is the same as the lens configuration of Numerical Example 1.

(Table 5)
Surface data surface number R d N (d) ν (d)
1 -47.315 1.500 1.49700 81.6
2 49.641 3.502 1.92286 18.9
3 87.695 3.604
4 stops ∞ 5.782
5 -29.866 1.500 1.84666 23.8
6 31.098 8.610 1.77250 49.6
7 -20.713 1.000
8 71.274 10.000 1.75700 47.8
9 -23.097 2.000 1.84666 23.8
10 -61.621 1.000
11 19.278 5.000 1.80 400 46.6
12 37.422-
(Table 6)
Various data
f 16.16
B 29.8
ER φ4.2
Eye relief 20.89

[Numerical Example 4]
7 to 8 and Tables 7 to 8 show Numerical Example 4 of the eyepiece system according to the present invention. FIG. 7 is a lens configuration diagram, and FIG. Table 7 shows surface data, and Table 8 shows various data.

  The lens configuration of Numerical Example 4 is the same as the lens configuration of Numerical Example 1.

(Table 7)
Surface data surface number R d N (d) ν (d)
1 -44.824 1.500 1.49700 81.6
2 43.099 3.329 1.67270 32.1
3 131.161 3.476
4 stops ∞ 5.851
5 -29.172 1.500 1.84666 23.8
6 31.938 8.610 1.77250 49.6
7 -20.695 1.000
8 74.573 10.000 1.75700 47.8
9 -21.492 2.000 1.84666 23.8
10 -58.985 1.000
11 19.216 5.000 1.80 400 46.6
12 36.704-
(Table 8)
Various data
f 16.16
B 29.8
ER φ4.2
Eye relief 21.14

[Numerical Example 5]
9 to 10 and Tables 9 to 10 show Numerical Example 5 of the eyepiece system according to the present invention. FIG. 9 is a lens configuration diagram, and FIG. Table 9 shows surface data, and Table 10 shows various data.

  The lens configuration of Numerical Example 5 is the same as the lens configuration of Numerical Example 1.

(Table 9)
Surface data surface number R d N (d) ν (d)
1 -28.579 1.500 1.49700 81.6
2 44.594 1.968 1.92286 18.9
3 67.948 3.747
4 stops ∞ 6.531
5 -92.666 1.500 1.84666 23.8
6 28.019 8.610 1.77250 49.6
7 -23.289 1.000
8 172.031 10.000 1.75700 47.8
9 -23.251 2.000 1.84666 23.8
10 -76.954 1.000
11 21.595 5.000 1.80 400 46.6
12 62.481-
(Table 10)
Various data
f 16.20
B 29.7
ER φ4.2
Eye relief 22.10

[Numerical Example 6]
11 to 12 and Tables 11 to 12 show Numerical Example 6 of the eyepiece system according to the present invention. FIG. 11 is a lens configuration diagram, and FIG. Table 11 shows surface data, and Table 12 shows various data.

The lens configuration of Numerical Example 6 is the same as the lens configuration of Numerical Example 1 except for the following points.
(1) The positive lens 12 of the first lens group G1 is a biconvex positive lens.
(2) Instead of the cemented lens of the biconcave negative lens 21 and the biconvex positive lens 22 of the second lens group G2, a positive meniscus lens (positive lens having a concave surface facing the objective side) 21 ′ provided on the eye side is provided. It has been.

(Table 11)
Surface data surface number R d N (d) ν (d)
1 -36.751 1.500 1.49700 81.6
2 24.501 3.526 1.57501 41.5
3 -628.565 3.035
4 stops ∞ 10.016
5 -39.636 8.000 1.80400 46.6
6 -22.918 1.000
7 92.278 11.000 1.61800 63.4
8 -18.533 1.500 1.84666 23.8
9 -87.693 1.000
10 25.808 5.800 1.80 400 46.6
11 198.664-
(Table 12)
Various data
f 20.21
B 24.1
ER φ5.2
Eye relief 27.23

[Numerical Example 7]
13 to 14 and Tables 13 to 14 show Numerical Example 7 of the eyepiece system according to the present invention. FIG. 13 is a lens configuration diagram, and FIG. Table 13 shows surface data, and Table 14 shows various data.

  The lens configuration of Numerical Example 7 is the same as the lens configuration of Numerical Example 6.

(Table 13)
Surface data surface number R d N (d) ν (d)
1 -30.180 1.500 1.49700 81.6
2 27.494 3.363 1.69895 30.1
3 -621.499 3.034
4 stops ∞ 8.580
5 -32.281 9.980 1.77250 49.6
6 -23.594 1.000
7 62.936 11.000 1.61800 63.4
8 -19.722 1.500 1.84666 23.8
9 -80.783 1.000
10 26.480 5.200 1.80 400 46.6
11 153.997-
(Table 14)
Various data
f 20.20
B 24.4
ER φ5.2
Eye relief 28.30

[Numerical Example 8]
15 to 16 and Table 15 to Table 16 show Numerical Example 8 of the eyepiece system according to the present invention. FIG. 15 is a lens configuration diagram, and FIG. Table 15 shows surface data, and Table 16 shows various data.

  The lens configuration of Numerical Example 8 is the same as the lens configuration of Numerical Example 6.

(Table 15)
Surface data surface number R d N (d) ν (d)
1 -20.499 1.500 1.49700 81.6
2 94.923 3.487 1.57501 41.5
3 -35.722 2.415
4 stops ∞ 9.456
5 -29.068 9.980 1.77250 49.6
6 -23.254 1.000
7 51.720 11.000 1.61800 63.4
8 -20.226 1.500 1.84666 23.8
9 -97.766 1.000
10 25.979 5.200 1.80 400 46.6
11 108.566-
(Table 16)
Various data
f 20.18
B 24.4
ER φ5.2
Eye relief 29.13

Table 17 shows values for the conditional expressions of the numerical examples.
(Table 17)
Example 1 Example 2 Example 3 Example 4
Conditional expression (1) -2.99 -4.09 -4.73 -4.77
Conditional expression (2) 40.1 62.7 58.1 49.5
Conditional expression (3) 0.078 0.426 0.311 0.176
Conditional expression (4) 0.64 0.59 0.58 0.58
Example 5 Example 6 Example 7 Example 8
Conditional expression (1) -2.61 -5.00 -8.40 -7.50
Conditional expression (2) 62.7 40.1 62.7 40.1
Conditional expression (3) 0.426 0.078 0.426 0.078
Conditional expression (4) 0.63 0.65 0.45 0.59

  As apparent from Table 17, Numerical Example 1 to Numerical Example 8 satisfy the conditional expressions (1) to (4), and various aberrations are corrected relatively well as is apparent from the various aberration diagrams. ing.

G1 First lens group with negative refractive power (field flatner)
11 Biconcave negative lens 12 Positive lens (positive lens with convex surface facing the objective)
G2 Second lens group 21 with positive refractive power 21 Negative lens (negative lens with concave surface facing the objective)
21 'positive lens (positive lens with concave surface facing the objective)
22 Positive lens (positive lens with convex surface facing the eye)
23 Biconvex positive lens 24 Negative lens (negative lens with concave surface facing the objective)
25 Positive lens (positive lens with concave surface facing the eye)
S Field stop

Claims (7)

In order from the objective side, in an eyepiece system comprising a first lens unit having a negative refractive power, a field stop, and a second lens group having a positive refractive power,
The first lens group includes a cemented lens of a negative lens and a positive lens positioned in order from the objective side, and satisfies the following conditional expressions (1) and (2).
(1) -9.5 <f1 / f2 <-2.5
(2) | ν1n−ν1p |> 40
However,
f1: the focal length of the first lens group,
f2: focal length of the second lens group,
ν1n: Abbe number with respect to d-line of the negative lens in the first lens group,
ν1p: Abbe number with respect to d-line of the positive lens in the first lens group. The eyepiece system according to claim 1, wherein the eyepiece system satisfies the following conditional expression (3).
(3) | N1n-N1p |> 0.07
However,
N1n: the refractive index of the negative lens in the first lens group with respect to the d-line,
N1p: Refractive index with respect to d-line of the positive lens in the first lens group. The eyepiece lens system according to claim 1 or 2, wherein the eyepiece lens system satisfies the following conditional expression (4).
(4) 0.4 <(D3 + D4) / f <0.7
However,
D3: an air space between the most eye-side surface of the first lens unit and the field stop,
D4: the air space between the field stop and the most objective surface of the second lens group,
f: Focal length of the entire system.   The eyepiece system according to any one of claims 1 to 3, wherein the first lens group includes a cemented lens of a biconcave negative lens positioned in order from the object side and a positive lens having a convex surface facing the object side. system.   5. The eyepiece system according to claim 1, wherein the second lens group includes a negative lens having a concave surface directed toward the objective side and a convex surface directed toward the eye side in order from the objective side. A cemented lens having a positive refractive power obtained by cementing a positive lens, a cemented lens having a positive refractive power obtained by cementing a biconvex positive lens positioned in order from the object side, and a negative lens having a concave surface directed toward the object side, and a concave surface on the eye side. Eyepiece lens system consisting of positive lenses facing   5. The eyepiece system according to claim 1, wherein the second lens group includes, in order from the object side, a positive lens having a concave surface directed toward the object side, a biconvex positive lens positioned in order from the object side, and an object. An eyepiece lens system comprising a cemented lens having a positive refractive power formed by cementing a negative lens having a concave surface facing the side, and a positive lens having a concave surface facing the eye side. In order from the objective side, in an eyepiece system comprising a first lens unit having a negative refractive power, a field stop, and a second lens group having a positive refractive power,
The first lens group is composed of a cemented lens of a negative lens and a positive lens positioned in order from the objective side, and satisfies the following conditional expression (2).
(2) | ν1n−ν1p |> 40
However,
ν1n: Abbe number with respect to d-line of the negative lens in the first lens group,
ν1p: Abbe number with respect to d-line of the positive lens in the first lens group.

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