JPH10301039A - Diopter correcting lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the diopter of a finder optical system without the complication of the constitution and to correct the diopter in a wide range by constituting a diopter correcting lens so that it can be attached/detached to/from the eye point side of an eyepiece and it may be provided with 1st and 2nd lens groups having respectively a negative refractive power and a positive refractive power from the eyepiece side, moving the 2nd lens group in the optical axis direction and changing the diopter of the finder optical system. SOLUTION: The diopter correcting lenses 4 and 5 are freely detachably attached behind the eyepiece 3 of the finder optical system. The diopter correcting lens is constituted of the 1st lens group 4 whose refractive power is negative and the 2nd lens group 5 whose refractive power is positive arranged in order from the eyepiece side. And by moving the 2nd lens group 5 in the optical axis direction, the diopter of the finder optical system is changed. An optional diopter is obtained in a wide diopter correction range by the works of two lens groups 4 and 5. Besides, it is preferable that 0. 7<|f1|/f2<1.0 is satisfied. Provided that f1 and f2 separately denote each focal distance of the 1st and 2nd lens groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diopter correction lens, and more particularly to a diopter correction lens for changing the diopter of a finder optical system.

[0002]

2. Description of the Related Art Conventionally, diopter correction of a finder optical system is performed by moving at least a part of an eyepiece lens along an optical axis, replacing a part of the lens with another lens, or using an eyepiece lens. This was done by adding an auxiliary lens.

[0003]

However, in the prior art, it is difficult to correct the diopter over a wide range, and if the diopter is corrected over a wide range, the configuration of the finder optical system becomes complicated. There was an inconvenience of doing so.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and corrects diopter over a wide range by changing diopter of the finder optical system without complicating the configuration of the finder optical system. It is an object of the present invention to provide a diopter correction lens that can perform the correction.

[0005]

In order to solve the above-mentioned problems, the present invention is configured so that the eyepiece of the finder optical system can be attached to and detached from the eyepoint side, and the negative refractive power is reduced in order from the eyepiece side. And a second lens group having a positive refractive power, wherein a diopter of the finder optical system is changed by moving the second lens group in an optical axis direction. To provide a diopter correcting lens.

According to a preferred aspect of the present invention, the first
Assuming that the focal length of the lens group is f1 and the focal length of the second lens group is f2, the following condition is satisfied: 0.7 <| f1 | / f2 <1.0.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention employs a configuration in which a diopter correction lens is detachably attached to the rear of the eyepiece of the finder optical system, that is, on the eye point side. Avoids the complexity of itself. For the purpose of diopter correction, the diopter correction lens of the present invention includes, in order from the eyepiece side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. . Then, the diopter of the finder optical system is changed by moving the second lens group in the optical axis direction.

As described above, by imparting a negative refractive power to the first lens group, a light beam which is being converged toward an eye point through an eyepiece having a generally positive refractive power is once diverged. An interval for attaching the diopter correction lens on the eye point side of the eyepiece can be secured. Further, by giving a positive refractive power to the second lens group, the light flux from the finder optical system once diverged by the first lens group is converged again, and a wide diopter correction range is obtained by the action of the two lens groups. , An arbitrary diopter can be obtained. That is, the diopter can be changed as needed by moving the second lens group along the optical axis, and continuous diopter correction can be performed in a specific range.

In the present invention, in addition to the above configuration,
It is desirable to satisfy the following conditional expressions (1). 0.7 <| f1 | / f2 <1.0 (1) where f1: focal length of the first lens group f2: focal length of the second lens group

Conditional expression (1) defines conditions for ensuring a wide diopter correction range without increasing the size of the diopter correction lens. If the lower limit of conditional expression (1) is not reached, the first
Since the refractive power of the lens group increases, the distance between the eyepiece of the finder optical system and the diopter correction lens may be increased, or a long eye relief (the axis between the eye point side of the diopter correction lens and the eye point closest to the eye point) (Upper interval). However, when the refracting power of the first lens group is increased, the luminous flux passing through the first lens group diverges greatly, so that the diameter of the second lens group tends to increase. In order to suppress an increase in the diameter of the second lens group, it is necessary to bring the second lens group closer to the first lens group. In this case, the moving range of the second lens group is narrowed, and a large diopter correction range is secured. It becomes difficult to do. Conversely, when trying to obtain a wide diopter correction range, the diameter of the second lens group increases, and the diopter correction lens tends to increase in size.

Further, if the refractive power of the first lens group is increased to obtain the same diopter correction range without changing the arrangement of the diopter correcting lens, it is necessary to increase the refractive power of the second lens group. However, if the refractive power of each lens group constituting the diopter correction lens is increased, the aberration of the field light flux transmitted through the finder optical system and the diopter correction lens deteriorates. In particular, since coma aberration deteriorates, it becomes difficult to secure a good eye point over the entire diopter correction range.
On the other hand, when the value exceeds the upper limit of conditional expression (1), the refractive power of the first lens unit tends to decrease. For this reason, the luminous flux through the finder system does not diverge much, and it is difficult to secure a wide diopter correction range and a long eye relief.

In the present invention, it is desirable to satisfy the following conditional expression (2). 5 <ν2−ν1 <35 (2) where, ν1: Abbe number of the lens constituting the first lens group ν2: Abbe number of the lens constituting the second lens group

Conditional expression (2) defines conditions for favorably correcting lateral chromatic aberration of the finder optical system over a wide diopter correction range. If the lower limit of conditional expression (2) is not reached, the diopter correction range in which the chromatic aberration of magnification can be favorably corrected will be small. On the other hand, when the value exceeds the upper limit of conditional expression (2), it is necessary to increase the distance between the first lens unit and the second lens unit in order to maintain good chromatic aberration of magnification, and the configuration of the diopter correction lens is practical. Is gone.

Further, in the present invention, it is desirable to introduce an aspherical surface into the diopter correction lens. By introducing an aspherical surface, coma and distortion can be satisfactorily corrected over the entire diopter correction range. In particular, by introducing an aspherical surface, when a large diopter correction range is to be ensured, it becomes easy to satisfactorily correct aberrations over the entire range.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each embodiment, the diopter correction lens of the present invention is configured so as to be detachable from the eye point side of the eyepiece of the finder optical system, and a first lens group having a negative refractive power in order from the eyepiece, And a second lens group having a refractive power of Then, the diopter of the finder optical system is changed by moving the second lens group in the optical axis direction.

In the fourth and fifth embodiments, the aspherical surface has a height y in the direction perpendicular to the optical axis and a displacement (sag amount) in the optical axis direction at the height y of S (y). ), When a reference radius of curvature (vertex radius of curvature) is R and a cone coefficient is κ, the following equation (a) is used. ^{S (y) = (y 2} / R) / {1+ (1-κ · y 2 / R 2) 1/2} (a) The paraxial curvature radius r of the aspherical surface, second order aspheric coefficient when it was the C _2, is represented by the following formula (b). r = 1 / (2C ₂ + 1 / R) (b) In the fourth and fifth embodiments, the aspherical surfaces are marked with * on the right side of the surface number.

[First Embodiment] FIG. 1 is an optical path development view showing a state in which a diopter correction lens according to a first embodiment of the present invention is attached to an eye point side of an eyepiece of a finder optical system of a single-lens reflex camera. It is. In FIG. 1, the finder optical system has, in order from the object side, a reticle 1 on which an object image is formed by a photographing lens of a camera, a pentaprism 2 as an erecting system, a biconvex lens, and a concave surface facing the object side. An eyepiece 3 made of a cemented lens with a negative meniscus lens. The diopter correction lens includes a first lens group including a biconcave lens 4 and a second lens group including a biconvex lens 5 in order from the eyepiece side. Note that in FIG. P indicates an eye point.

The following Table (1) shows values of specifications of the first embodiment of the present invention. In Table (1), ER indicates an eye relief, a surface number indicates an order of lens surfaces along the traveling direction of light from the reticle 1, r indicates a radius of curvature (∞ indicates a flat surface) of the lens surface, and d indicates a surface radius. Ν and n are d-line (λ
= 587.6 nm) respectively.

[0019]

[Table 1] Surface number r dn v 1 ∞ 3.30 (eye point side of reticle 1) 2 ∞ 88.00 1.51680 64.1 (pentaprism 2) 3 ∞ 2.80 4 59.678 6.50 1.60311 60.6 (eyepiece 3) 5 -30.150 1.50 1.74077 27.6 6 -84.550 4.30 7 -42.000 0.80 1.80410 46.5 (biconcave lens 4) 8 42.000 (d8 = variable) 9 40.945 2.70 1.69680 55.4 (biconvex lens 5) 10 -40.945 (ER = variable) (variable interval in diopter correction) ) Diopter -2.88 -0.99 +0.88 d8 1.00 2.60 4.20 ER 15.8 14.2 12.6 (Values corresponding to conditional expressions) (1) | f1 | / f2 = 0 .87 (2) ν2-ν1 = 8.9

FIGS. 2 to 4 show various aberration diagrams of the first embodiment. That is, FIG. 2 is a diagram of various aberrations at the eye point when the diopter is -2.88 diopters, FIG. 3 is a diagram of various aberrations at the eye point when the diopter is -0.99 diopters, FIG. 4 is a diagram of various aberrations at the eye point when the diopter is +0.88 diopter. In each aberration diagram, H is the height of the pentaprism 2 from the optical axis on the side of the reticle 1, Y is the object height, Dp is the diopter,
min is the angle unit, D is the d-line (λ = 587.6n
m), C indicates the C line (λ = 656.3 nm), and F indicates the F line (λ = 486.1 nm). Also,
In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 2 to 4, it can be seen that in the first embodiment, various aberrations are satisfactorily corrected at each diopter, even though the diopter correction range is about 4 diopters.

[Second Embodiment] FIG. 5 is an optical path development view showing a state in which a diopter correction lens according to a second embodiment of the present invention is attached to an eye point side of an eyepiece of a finder optical system of a single-lens reflex camera. It is. In FIG. 5, the finder optical system has, in order from the object side, a reticle 1 on which an object image is formed by a photographing lens of a camera, a pentaprism 2 as an erecting system, a biconvex lens, and a concave surface facing the object side. An eyepiece 3 made of a cemented lens with a negative meniscus lens. The diopter correction lens includes a first lens group including a biconcave lens 4 and a second lens group including a biconvex lens 5 in order from the eyepiece side. Note that in FIG. P indicates an eye point.

Table 2 below summarizes data values of the second embodiment of the present invention. In Table (2), ER indicates an eye relief, a surface number indicates an order of lens surfaces along the traveling direction of light from the reticle 1, r indicates a radius of curvature (の indicates a flat surface) of the lens surface, and d indicates a lens surface. Ν and n are d-line (λ
= 587.6 nm) respectively.

[0023]

[Table 2] Surface number r dn ν 1 ∞ 3.30 (surface on the eye point side of reticle 1) 2 ∞ 88.00 1.51680 64.1 (pentaprism 2) 3 ∞ 2.80 4 59.678 6.50 1.60311 60.6 (eyepiece 3) 5 -30.150 1.50 1.74077 27.6 6 -84.550 4.30 7 -40.550 0.80 1.72342 37.9 (Bi-concave lens 4) 8 40.550 (d8 = Variable) 9 44.000 3.00 1.71300 53.9 (Bi-convex lens 5) 10 -44.000 (ER = Variable) (Variable interval in diopter correction) ) Diopter −2.0 −1.0 +1.0 d8 1.10 2.10 4.10 ER 16.00 15.00 13.00 (Values corresponding to conditional expressions) (1) | f1 | / f2 = 0 .89 (2) v2-v1 = 16.0

FIGS. 6 to 8 are graphs showing various aberrations of the second embodiment. That is, FIG. 6 is a diagram of various aberrations at the eye point when the diopter is -2.0 diopter, FIG. 7 is a diagram of various aberrations at the eye point when the diopter is -1.0 diopter, FIG. 8 is a diagram of various aberrations at the eye point when the diopter is +1.0 diopter. In each aberration diagram,
H is the height of the pentaprism 2 from the optical axis on the side of the reticle 1, Y is the object height, Dp is the diopter, min is the angle unit, and D is the d line (λ = 587. 6 nm)
C is the C line (λ = 656.3 nm), F is the F line (λ = 4
86.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 6 to 8, it can be seen that in the second embodiment, various aberrations are favorably corrected at each diopter, even though the diopter correction range is 3 diopters.

[Third Embodiment] FIG. 9 is an optical path development diagram showing a state in which a diopter correction lens according to a third embodiment of the present invention is attached to the eye point side of an eyepiece of a finder optical system of a single-lens reflex camera. It is. In the third embodiment, unlike the first and second embodiments, the eyepiece 3 is formed of a single plastic lens. In FIG. 9, the finder optical system includes, in order from the object side, a reticle 1 on which an object image is formed by a photographing lens of a camera, a pentaprism 2 as an erecting system, and an eyepiece 3 made of a biconvex lens. Have been. The diopter correction lens includes a first lens group including a biconcave lens 4 and a second lens group including a biconvex lens 5 in order from the eyepiece side. Note that in FIG. P indicates an eye point.

Table 3 below summarizes the data values of the third embodiment of the present invention. In Table (3), ER indicates an eye relief, a surface number indicates an order of lens surfaces along the traveling direction of light from the reticle 1, r indicates a radius of curvature of the lens surface (∞ indicates a flat surface), and d indicates a lens surface. Ν and n are d-line (λ
= 587.6 nm) respectively.

[0027]

[Table 3] Surface number r dn ν 1 ∞ 3.30 (eye point side of reticle 1) 2 ∞ 82.00 1.51680 64.1 (pentaprism 2) 3 ∞ 5.00 4 39.234 6.00 1.49 108 57.5 (eyepiece 3) 5 -200.049 3.00 6 -43.250 1.00 1.58300 29.9 (Bi-concave lens 4) 7 43.250 (d7 = Variable) 8 40.945 3.00 1.49108 57.7 (Bi-convex lens 5) 9 -40.945 (ER = Variable) (Variable interval in diopter correction) Diopter-2. 55 -1.01 +0.41 d7 1.00 3.50 6.00 ER 15.00 12.50 10.00 (Values corresponding to conditional expressions) (1) | f1 | /f2=0.87 (2) ν2 −ν1 = 27.6

FIGS. 10 to 12 show various aberration diagrams of the third embodiment. That is, FIG. 10 is a diagram of various aberrations at the eye point when the diopter is −2.55 diopters.
1 is an aberration diagram at the eye point when the diopter is -1.01 diopter, and FIG. 12 is an aberration diagram at the eye point when the diopter is +0.41 diopter. In each aberration diagram, H is the height of the pentaprism 2 from the optical axis on the side of the reticle 1, Y is the object height, Dp is diopter, min is the angle unit, and D is the d-line. (Λ = 58
7.6 nm), C is the C line (λ = 656.3 nm),
F indicates the F line (λ = 486.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. Referring to FIGS. 10 to 12, in the third embodiment,
It can be seen that various aberrations are satisfactorily corrected at each diopter, even though the eyepiece is a single lens and the diopter correction range is about 3 diopters.

Fourth Embodiment FIG. 13 is an optical path development diagram showing a state in which a diopter correction lens according to a fourth embodiment of the present invention is attached to the eyepoint side of an eyepiece of a finder optical system of a compact camera. is there. In FIG. 13, the finder optical system includes, in order from the object side, an objective lens (not shown), a reticle 1 on which an object image is formed by the objective lens, and an erect prism 2 having a condenser lens on the entrance surface. And an eyepiece 3 made of a convex lens. The diopter correction lens includes a first lens group including a biconcave lens 4 and a second lens group including a biconvex lens 5 in order from the eyepiece side. In addition,
In FIG. P indicates an eye point.

Table 4 below summarizes data values of the fourth embodiment of the present invention. In Table (4), ER indicates an eye relief, surface numbers indicate the order of lens surfaces along the traveling direction of light from the reticle 1, r indicates a radius of curvature of the lens surface (平面 indicates a flat surface), and d indicates a lens surface. Ν and n are d-line (λ
= 587.6 nm) respectively. The object-side surface of the erect prism 2 and the object-side surface of the eyepiece 3 are formed in aspherical shapes.

[0031]

[Table 4] Surface number rd nv 1 ∞ 0.55 1.51680 64.1 (focus plate 1) 2 ∞ 0.50 3 * 11.500 29.00 1.49108 57.5 (erect prism 2) 4 ∞ 0.80 5 * 21.645 2.30 1.49108 57.5 (eyepiece 3) 6 -21.645 1.00 7 -31.360 1.00 1.58300 29.9 (Bi-concave lens 4) 8 31.360 (d8 = Variable) 9 28.000 2.00 1.49108 57.5 (Bi-convex lens 5) 10 -28.000 (ER = Variable) (Aspherical data) 3 planes C ₂ = 0 κ = 0 5 plane C ₂ = 0 κ = −4.9 (variable interval in diopter correction) Diopter −1.0 +1.0 +3.0 d8 1.00 2.70 4.50 ER 15.00 13 .30 11.50 (Values corresponding to conditional expressions) (1) | f1 | /f2=0.92 (2) ν2-ν1 = 27.6

FIGS. 14 to 16 show various aberration diagrams of the fourth embodiment. That is, FIG. 14 shows that the diopter of the eyepiece is −
FIG. 15 is a diagram illustrating various aberrations at the eye point when the diopter is 1.0 diopter, and FIG. 15 is a diagram illustrating various aberrations at the eye point when the diopter of the eyepiece is +1.0 diopter.
FIG. 4 is a diagram illustrating various aberrations at the eye point when the diopter of the eyepiece is +3.0 diopters. In each aberration diagram, H
Is the height of the pentaprism 2 from the optical axis on the side of the reticle 1, Y is the object height, Dp is the diopter, min is the angle unit, and D is the d line (λ = 587.6 nm). ) To C
Is the C line (λ = 656.3 nm), and F is the F line (λ = 48
6.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. 14 to 16
In the fourth example, it can be seen that, in the fourth example, various aberrations are favorably corrected over the diopter correction range of 4 diopters even though the focal length of the eyepiece is small.

Fifth Embodiment FIG. 17 is an optical path development view showing a state in which a diopter correction lens according to a fifth embodiment of the present invention is attached to the eyepoint side of an eyepiece of a finder optical system of a compact camera. is there. In FIG. 17, the finder optical system includes, in order from the object side, an objective lens (not shown), a reticle 1 on which an object image is formed by the objective lens, and an erect prism 2 having a condenser lens on the entrance surface. And an eyepiece 3 made of a convex lens. The diopter correction lens includes a first lens group including a biconcave lens 4 and a second lens group including a biconvex lens 5 in order from the eyepiece side. In addition,
In FIG. P indicates an eye point.

Table 5 below summarizes the data values of the fifth embodiment of the present invention. In Table (5), ER indicates an eye relief, a surface number indicates an order of lens surfaces along the traveling direction of light from the reticle 1, r indicates a radius of curvature of the lens surface (∞ indicates a flat surface), and d indicates a lens surface. Ν and n are d-line (λ
= 587.6 nm) respectively. The object-side surface of the erect prism 2 and the object-side surface of the eyepiece 3 are formed in aspherical shapes.

[0035]

[Table 5] Surface number rdnv1 ∞ 0.55 1.51680 64.1 (focus plate 1) 2 ∞ 0.50 3 * 11.500 29.00 1.49108 57.5 (Erect prism 2) 4 4 0.80 5 * 21.645 2.30 1.49108 57.5 (Eyepiece 3) 6 -21.645 1.00 7 -30.000 1.00 1.58300 29.9 (Bi-concave lens 4) 8 30.000 (d8 = Variable) 9 33.150 2.00 1.49108 57.5 (Bi-convex lens 5) 10 -33.150 (ER = Variable) (Aspherical data) 3 planes C ₂ = 0 κ = 0 5 plane C ₂ = 0 κ = −4.9 (variable interval in diopter correction) Diopter −1.0 +1.0 +3.0 d8 7.00 4.80 1.70 ER 15.00 17 .20 20.30 (Values corresponding to conditional expressions) (1) | f1 | /f2=0.75 (2) ν2-ν1 = 27.6

FIGS. 18 to 20 show various aberration diagrams of the fifth embodiment. That is, FIG. 18 shows that the diopter of the eyepiece is −
FIG. 19 is a diagram illustrating various aberrations at the eye point when the diopter is 1.0 diopter, and FIG. 19 is a diagram illustrating various aberrations at the eye point when the diopter of the eyepiece is +1.0 diopter.
FIG. 4 is a diagram illustrating various aberrations at the eye point when the diopter of the eyepiece is +3.0 diopters. In each aberration diagram, H
Is the height of the pentaprism 2 from the optical axis on the side of the reticle 1, Y is the object height, Dp is the diopter, min is the angle unit, and D is the d line (λ = 587.6 nm). ) To C
Is the C line (λ = 656.3 nm), and F is the F line (λ = 48
6.1 nm). In the aberration diagram showing astigmatism, a solid line indicates a sagittal image plane, and a broken line indicates a meridional image plane. 18 to 20
In the fifth example, it can be seen that in the fifth example, various aberrations are favorably corrected over the diopter correction range of 4 diopters despite the small focal length of the eyepiece.

In each of the above-described embodiments, the diopter correction lens of the present invention is applied to the finder optical system of a single-lens reflex camera or a compact camera. A correction lens can be easily applied. In the above-described fourth and fifth embodiments, the diopter correction range is -1.0 to +
Although the diopter is set to 3.0 diopters, various aberrations can be satisfactorily corrected for each diopter within the diopter correction range even if the diopter correction range is set on the minus side.

[0038]

As described above, according to the present invention, the diopter of the finder optical system is changed by a simple lens configuration without complicating the configuration of the finder optical system, and the diopter is changed over a wide range. It is possible to realize a diopter correction lens that can perform correction.

[Brief description of the drawings]

FIG. 1 is an optical path development view showing a state in which a diopter correction lens according to a first embodiment of the present invention is attached to an eye point side of an eyepiece of a finder optical system of a single-lens reflex camera.

FIG. 2 is a diagram illustrating various aberrations at the eye point when the diopter is −2.88 diopters in the first example.

FIG. 3 is a diagram illustrating various aberrations at the eye point when the diopter is −0.99 diopters in the first example.

FIG. 4 is a diagram illustrating various aberrations at the eye point when the diopter is +0.88 diopters in the first example.

FIG. 5 is an optical path development diagram showing a state in which a diopter correction lens according to a second embodiment of the present invention is attached to an eyepoint side of an eyepiece of a finder optical system of a single-lens reflex camera.

FIG. 6 is a diagram illustrating various aberrations at the eye point when the diopter is −2.0 diopters in the second example.

FIG. 7 is a diagram illustrating various aberrations at the eye point when the diopter is −1.0 diopter in the second example.

FIG. 8 is a diagram illustrating various aberrations at the eye point when the diopter is +1.0 diopter in the second example.

FIG. 9 is an optical path development diagram showing a state in which a diopter correction lens according to a third embodiment of the present invention is attached to an eyepoint side of an eyepiece of a finder optical system of a single-lens reflex camera.

FIG. 10 is a diagram illustrating various aberrations at the eye point when the diopter is −2.55 diopters in the third example.

FIG. 11 is a diagram illustrating various aberrations at the eye point when the diopter is −1.01 diopter in the third example.

FIG. 12 is a diagram illustrating various aberrations at the eye point when the diopter is +0.41 diopter in the third example.

FIG. 13 is an optical path development view showing a state in which a diopter correction lens according to a fourth embodiment of the present invention is attached to an eye point side of an eyepiece of a viewfinder optical system of a compact camera.

FIG. 14 is a diagram illustrating various aberrations at the eye point when the diopter is −1.0 diopter in the fourth example.

FIG. 15 is a diagram illustrating various aberrations at the eye point when the diopter is +1.0 diopter in the fourth example.

FIG. 16 is a diagram illustrating various aberrations at the eye point when the diopter is +3.0 diopters in the fourth example.

FIG. 17 is an optical path development view showing a state in which a diopter correction lens according to a fifth embodiment of the present invention is attached to an eyepoint side of an eyepiece of a viewfinder optical system of a compact camera.

FIG. 18 is a diagram illustrating various aberrations at the eye point when the diopter is −1.0 diopter in the fifth example.

FIG. 19 is a diagram illustrating various aberrations at the eye point when the diopter is +1.0 diopter in the fifth example.

FIG. 20 is a diagram illustrating various aberrations at the eye point when the diopter is +3.0 diopters in the fifth example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Focusing plate 2 Prism 3 Eyepiece 4 First lens group of diopter correction lens 5 Second lens group of diopter correction lens

Claims (4)

[Claims] 1. A first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the eyepiece lens side, the first lens group being configured to be detachable from an eye point side of an eyepiece of a finder optical system. And a diopter correction lens, wherein the diopter of the finder optical system is changed by moving the second lens group in an optical axis direction. 2. When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, the following condition is satisfied: 0.7 <| f1 | / f2 <1.0. The diopter correction lens according to claim 1, wherein: 3. The condition of 5 <ν2−ν1 <35 is satisfied, where the Abbe number of the lens forming the first lens group is ν1 and the Abbe number of the lens forming the second lens group is ν2. The diopter correction lens according to claim 1, wherein the diopter correction is performed. 4. The first lens group is a biconcave lens,
The diopter correction lens according to any one of claims 1 to 3, wherein the second lens group is a biconvex lens.