JPH06118303A - Real image type variable power finder optical system - Google Patents

Abstract

PURPOSE:To excellently compensate aberrations and to let an optical system meet the size reduction of a camera by making the movement quantity of a moving lens group on the pupil side of a reflection member smaller than the movement quantity of a moving lens group on the object side of the reflection member. CONSTITUTION:This finder optical system consists of the objective lens which is composed of three 1st, 2nd, and 3rd lens groups G1, G2, and G3 in order from the object side and varies the power by moving the 2nd and 3rd lens groups G2 and G3, and an ocular. In this lens constitution, the 2nd lens group functions mainly for power variation and the 3rd lens group functions for diopter correction. Namely, the movement quantity of the moving lens group on the pupil side of the reflection member is made smaller than the movement quantity of the moving lens group on the object side of the reflection member. Namely, B2T/B2W-B3T/B3W holds, where B2W is the power of the 2nd lens group at the wide-angle end, B2T the power of the 2nd lens group at the telephoto end, B3W the power of the 3rd lens group at the wide-angle end, and B3T the power of the 3rd lens group at the telephoto end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a real image type variable magnification finder optical system.

[0002]

2. Description of the Related Art The thickness of a camera depends on the length from the first surface of the first lens group of the objective lens of the finder to the first reflecting surface of the reflecting member. Therefore, in order to reduce the thickness of the camera, it is necessary to shorten the length of the objective lens of the finder optical system. However, in order to reduce the length of the objective lens, it is necessary to increase the refracting power of each lens, which causes a large amount of aberration. Therefore, as shown in Japanese Unexamined Patent Publication No. 4-86733 shown in FIG. 23, a reflecting surface M is provided between the moving lens groups G ₂ and G ₃ to bend the optical axis to shorten the length of the objective lens and to reduce the length of the camera. Some have a smaller thickness. However, in this conventional example, only one reflecting surface can be formed, and it is necessary to provide another reflecting surface in the objective lens system, resulting in high cost. Further, although the thickness of the camera is reduced, the size of the camera is not necessarily reduced.

[0003]

In the above-mentioned conventional example, in order to reduce the thickness of the camera, a reflecting surface is provided between the moving lens groups to bend the optical axis. However, in this conventional example, only one reflecting surface can be provided between the lens groups, and therefore the optical axis can be bent only 90 °. In addition, there is a moving lens group after the optical axis is bent at a right angle, the camera becomes large in the vertical or horizontal direction by the amount of movement of this lens group, and then another reflection member must be provided. The viewfinder occupies a large volume, which is not preferable for compactness. In addition, since the moving lenses are always arranged at right angles to each other in any structure of the reflecting member, the driving mechanism for moving the lenses becomes complicated.

An object of the present invention is to eliminate the above-mentioned drawbacks by adopting a three-group objective lens to correct aberrations satisfactorily, and moreover, to realize miniaturization of a camera and real-image type variable magnification. It is to provide an optical system.

[0005]

A real image type variable power optical system of the present invention is a variable power system which comprises an objective lens having a positive refracting power as a whole and an eyepiece lens having a positive refracting power. The objective lens has two moving lens groups and a reflecting member having at least two reflecting surfaces between the two lens groups, and the moving amount of the moving lens group on the object side of the reflecting member is larger than that of the reflecting member. The feature is that the moving amount of the moving lens unit on the pupil side is reduced.

The optical system of the present invention comprises, for example, as shown in FIG. 1, three lens groups G ₁ , G ₂ and G ₃ of negative, positive and positive first, second and third in order from the object side. It is composed of an objective lens and an eyepiece lens which are configured to move the second and third lens groups G ₂ and G ₃ to change the magnification. 2 is a perspective view of FIG. When installing this optical system in a camera,
The length from the first surface of the lens group G ₁ to the first reflecting surface of the reflecting member D ₁ must be ensured, which is the thickness of the camera. Therefore, in order to reduce the thickness of the camera, in order to reduce the thickness of the camera, the movable lens group (the second and third lens groups in FIG.
It is possible to shorten the length from the first surface to the reflecting surface by disposing the reflecting member between the lens groups. However, if only one reflecting surface can be arranged between the moving lens groups, the thickness of the camera can be reduced, but the optical system cannot always be compactly housed inside the camera. According to the present invention, a reflecting member having two reflecting surfaces is arranged between the moving lens groups, and by doing so, a thin and compact camera can be realized.

Here, in the conventional objective lens of the finder optical system, the second lens group and the third lens group in the lens system including the negative first lens group, the positive second lens group, and the positive third lens group. Consider a case where two reflective surfaces are provided between the two. First, focusing on only the first lens group and the second lens group, these are configured by a negative first lens group and a positive second lens group, and a lens configuration of a type that can lengthen the back focus. Therefore, it is understood that it is sufficient to dispose the reflecting member after the second lens group and correct the diopter by the third lens group.

When the reflecting member is arranged between the movable lens groups in this way, the third lens group is arranged near the intermediate image forming plane. Therefore, if the third lens group is mainly made to have a function of zooming, the amount of movement of this lens group becomes large, and the distance to the intermediate image forming surface must be made large, so that it can be compactly housed inside the camera. Disappear. Therefore, the optical path length of the reflecting member cannot be sufficiently obtained. Therefore, it is preferable that the second lens group mainly has a variable power role and the third lens group has a diopter correction function. That is, the moving amount of the moving lens unit on the pupil side of the reflecting member is smaller than the moving amount of the moving lens unit on the object side of the reflecting member.

The above contents are shown by the formulas as follows.

Β _2T / β _2W −β _3T / β _3W > 0 where β _2W is the magnification at the wide end of the second lens group, β
_2T is the magnification at the tele end of the second lens group, β _3W is the magnification at the wide end of the third lens group, and β _3T is the magnification at the tele end of the third lens group.

With the above structure, a reflecting member having two reflecting surfaces can be arranged in the moving lens group.

The arrangement when the optical system having this lens structure is housed inside the camera will now be described. For example, when a Porro prism is used for the reflecting member, the reflecting member can be arranged by utilizing the space (shaded portion in FIG. 24) which is conventionally open inside the camera, and it can be made thin and compactly housed in the camera. Further, since the moving direction of the moving lens group is the same as the optical axis of the taking lens, the driving mechanism can be simplified.
However, since the prism moves to the object side in the eyepiece system, the loupe lens also goes inside the camera. However, the eyepoint of the eyepiece should be increased. If the eyepoint cannot be made large, the thickness of the camera can be reduced while keeping the same eyepoint by performing the procedure shown in FIGS. Further, the same effect can be obtained by using a polo mirror or a roof mirror as the reflecting member.

FIGS. 5 and 6 are schematic views showing the finder optical system of the present invention. G ₁ , G ₂ and G ₃ are the first, second and third lens groups, respectively. In this figure, it is important to take the optical path length between the second lens group G ₂ and the third lens group G ₃ which are moving lens groups. Considering a lens system including only the first lens group G ₁ and the second lens group G ₂ , the intermediate image formation plane I
Since the reflecting member P ₁ and the third lens group G ₃ are present up to, the back focus of the system including the lens groups G ₁ and G ₂ must be large. For that purpose, it is preferable to satisfy the following condition (1). (1) 0.2 <−f _W / f ₁ <1.5 where f ₁ is the focal length of the first lens group G ₁ , and f _W is the focal length at the wide end of the objective lens.

If the lower limit of the condition (1) is exceeded, the optical path length required for disposing the reflecting member P _{1 and the} like cannot be secured. If the upper limit of condition (1) is exceeded, the above optical path length can be secured,
The refracting power of the first lens group G ₁ becomes too strong and the aberrations deteriorate, making correction difficult.

In the above description, the third lens group G ₃ is configured as a positive lens group, but it may be a negative lens group. The third lens group G ₃ has a role of adjusting the diopter of the optical system. When the third lens group G ₃ has a negative refractive power as described above, the movement of the third lens group G ₃ for diopter adjustment is performed when the third lens group G ₃ has a positive refractive power (see FIG. 5). ) Is the opposite.

The third lens group G ₃ satisfies the condition (2) when the refractive power is positive (f ₃ > 0) and negative (f ₃ <0).
It is desirable that 0) satisfy the condition (3). _{(2) 0.2 <f 2 /} f 3 <1.2 (3) 0.5 <f 2 / -f 3 <1.5 However _f 2, _{f 3} are each second lens group _{G 2} and the third It is the focal length of the lens group G ₃ .

If the lower limit of the condition (2) or the condition (3) is exceeded, the refracting power of the third lens group G ₃ becomes weak, and diopter correction cannot be performed while maintaining the optical path length of the reflecting member.
Further, if the upper limit of the condition (2) or the condition (3) is exceeded, the refractive power of the third lens group G ₃ becomes strong, which is not preferable for aberration correction.

Further, it is preferable to provide an aspherical surface in the third lens group G ₃ in order to correct distortion. For the reflective member,
It is possible to use a prism or a mirror. When a prism is used as the reflecting member, it is possible to give power to the incident surface and the exit surface, but this power may be positive or negative. When a mirror is used as the reflecting member, the lens may be arranged on the object side of the mirror.

[0019]

EXAMPLES The following are practical examples of the real image type variable magnification finder optical system of the present invention. Example 1 r ₁ = ∞ d ₁ = 1.000 n ₁ = 1.58423 ν ₁ = 3 0.49 r ₂ = 14.2831 (aspherical surface) d ₂ = D ₁ r ₃ = 15.55046 d ₃ = _{3.500 n 2 = 1.49241 ν 2 =} 57.66 r 4 = -19.1871 ( _{aspherical) d 4 = D 2 r 5} = 20.9674 ( _aspherical) d 5 = 17.000 n ₃ = 1.49241 ν ₃ = 57.66 r ₆ = ∞ d ₆ = D ₃ r ₇ = 9.4249 d ₇ = 2.000 n ₄ = 1.49241 ν ₄ = 57.66 r ₈ = 57.74444 d ₈ = D ₄ r ₉ = ∞ (field frame) d ₉ = 1.000 r ₁₀ = ∞ d ₁₀ = 25.000 n ₅ = 1.49241 ν ₅ = 57.66 r ₁₁ = ∞ d ₁₁ = 2.000 r _{12 = 17.8960 d 12 = 3.400 n} 6 = _{.49241 ν 6 = 57.66 r 13 =} -22.9520 ( _{aspherical) d 13 = 20.000 r 14 =} ∞ ( eye point) aspheric coefficient (second surface) P = 1.0000, E = 0 80634 × 10 ⁻⁴ , F = −0.83 595 × 10 ⁻⁵ G = 0.27053 × 10 ⁻⁶ (4th surface) P = 1.0000, E = 0.16165 × 10 ⁻⁴ , F = −0.13 098 × 10 ⁻⁶ G = 0.22307 × 10 ⁻⁶ (fifth surface) P = 1.0000, E = −0.18479 × 10 ⁻³ , F = 0.24 977 × 10 ⁻⁴ G = −0.10000 × 10 ⁻⁵ (thirteenth surface) P = 1.0000, E = 0.79267 × 10 ⁻⁴ , F =. 0.5 7040 × 10 ⁻⁶ G = 0.68501 × 10 ⁻⁸ Magnification 0.42 0.55 0.73 Incident angle 2ω 49.2 ° 35.7 ° 25.8 ° D ₁ 16.9313 12.66639.5 .7
851 D ₂ 0.9934 5.2608 12.1
397 D ₃ 1.1646 2.4609 1.0
000 D ₄ 2.4963 1.2000 2.6
609 β _2T / β _2W −β _3T / β _3W = 0.837, −f _{W
/ F 1 = 0.360, f 2} / f 3 = 0.798 Example _{2 r 1 = -47.6349 d 1 =} 1.000 n 1 = 1.58423 ν 1 = 30.49 r 2 = 11. 3090 (aspherical surface) d ₂ = D ₁ r ₃ = 8.5940 d ₃ = 4.00 n ₂ = 1.49421 ν ₂ = 57.66 r ₄ = −13.8822 (aspherical surface) d ₄ = D ₂ r ₅ = -157.1628 d ₅ = 17.000 n ₃ = 1.49421 ν ₃ = 57.66 r ₆ = −34.8083 d ₆ = D ₃ r ₇ = 28.5534 (aspherical surface) d ₇ = _{2.000 n 4 = 1.49241 ν 4 =} 57.66 r 8 = -9.5875 d 8 = D 4 r 9 = ∞ ( field _{frame) d 9 = 1.000 r 10 =} ∞ d 10 = 25. _{000 n 5 = 1.49241 ν 5 =} 57.66 r 1 _{= ∞ d 11 = 2.000 r 12} = 17.8960 d 12 = 3.400 n 6 = 1.49241 ν 6 = 57.66 r 13 = -22.9520 ( _aspherical) d 13 = 20.000 r ₁₄ = ∞ (eye point) Aspherical surface coefficient (second surface) P = 1.0000, E = 0.37587 × 10 ⁻⁴ , F = −0.40 688 × 10 ⁻⁵ G = 0.17093 × 10 ^{− 6} (4th surface) P = 10000, E = 0.42798 × 10 ⁻³ , F = −0.610 06 × 10 ⁻⁵ G = 0.11478 × 10 ⁻⁶ (7th surface) P = 1.0000 , E = 0.52338 × 10 ⁻³ , F = −0.40 706 × 10 ⁻⁴ G = −0.57707 × 10 ⁻⁶ (13th surface) P = 1.0000, E = 0.79267 × 10 ^{-4, F = -0.5 7040 × 10} -6 G = 0.68 01 × ^{10 -8} magnification 0.42 0.55 0.73 incident angle _{2ω48.6 ° 36.2 ° 25.7 ° D 1} 10.2355 8.3014 3.705
5 D ₂ 1.2650 3.1991 7.795
0 D ₃ 1.0000 2.7483 1.587
3 D ₄ 2.7481 1.0000 2.161
0 β _2T / β _2W −β _3T / β _3W = 0.670, −f _W
/ F ₁ = 0.567, f ₂ / f ₃ = 0.772 Example 3 r ₁ = 1.7826 d ₁ = 1.000 n ₁ = 1.58423 ν ₁ = 30.49 r ₂ = 5.7602 (Aspherical surface) d ₂ = D ₁ r ₃ = 17.2727 d ₃ = 3.500 n ₂ = 1.49241 ν 2 = 57.66 r ₄ = −19.99917 (aspherical surface) d ₄ = D ₂ r ₅ = 22.7521 _{(aspherical) d 5 = 19.000 n 3 =} 1.49241 ν 3 = 57.66 r 6 = -9.2533 d 6 = D 3 r 7 = -6.5774 ( aspherical) d ₇ = 2.123 n ₄ = 1.58423 ν ₄ = 30.49 r ₈ = -13.5892 d ₈ = D ₄ r ₉ = ∞ (field frame) d ₉ = 1.000 r ₁₀ = ∞ d ₁₀ = _{25.000 n 5 = 1.49241 ν 5 =} 57.66 r 1 ₁ = ∞ d ₁₁ = 2.000 r ₁₂ = 17.8960 d ₁₂ = 3.400 n ₆ = 1.49241 ν ₆ = 57.66 r ₁₃ = -22.9520 (aspherical surface) d ₁₃ = 20.000 r ₁₄ = ∞ (eye point) Aspherical surface coefficient (second surface) P = 1.0000, E = −0.16113 × 10 ⁻³ , F = 0.244 383 × 10 ⁻⁵ G = −0.28437 × 10 ⁻⁶ (fourth surface) P = 1.0000, E = −0.83801 × 10 ⁻⁴ , F = 0.29 452 × 10 ⁻⁵ G = −0.13869 × 10 ⁻⁶ (fifth surface) P = 1.0000, E = −0.24666 × 10 ⁻³ , F = 0.15 700 × 10 ⁻⁵ G = −0.19113 × 10 ⁻⁶ (7th surface) P = 1.0000, E = −0.51080 × 10 ⁻³ , F = 0.11 222 × 10 ⁻³ G = −0 27077 × 10 ⁻⁵ (thirteenth surface) P = 1.0000, E = 0.79267 × 10 ⁻⁴ , F = −0.5 7040 × 10 ⁻⁶ G = 0.68501 × 10 ⁻⁸ magnification 0. 42 0.55 0.73 Incident angle 2ω 49.4 ° 36.7 ° 26.3 ° D ₁ 22.7509 18.0645 10.9
669 D ₂ 1.0000 5.68665 12.7
840 D ₃ 2.4443 1.3000 2.3
318 D ₄ 1.1876 2.3318 1.3
000 β _2T / β _2W −β _3T / β _3W = 0.799, −f _W
/ F ₁ = 0.386, f ₂ / −f ₃ = 0.790 Example 4 r ₁ = -11.3483 d ₁ = 1.000 n ₁ = 1.58423 ν ₁ = 30.49 r ₂ = 11 .7092 (aspherical surface) d ₂ = D ₁ r ₃ = 8.5448 (aspherical surface) d ₃ = 2.223 n ₂ : 1.49421 ν ₂ : 57.66 r ₄ = −9.9778 d ₄ = D ₂ r ₅ = 57.1126 d ₅ = 1.000 n ₃ = 1.58423 ν ₃ = 30.49 r ₆ = 10.2677 (aspherical surface) d ₆ = D ₃ r ₇ = 6.2502 d ₇ = 3 _{.587 n 4 = 1.49241 ν 4 =} 57.66 r 8 = 16.3419 d 8 = 0.500 r 9 = 5.3470 ( _{aspherical) d 9 = 1.000 n 5 =} 1.58423 ν 5 _{= 30.49 r 10 = 4.9106 d 10} = D r ₁₁ = ∞ (field _{frame) d 11 = 1.000 r 12 =} ∞ d 12 = 25.000 n 6 = 1.49241 ν 6 = 57.66 r 13 = ∞ d 13 = 2.000 r 14 = 17 _{.8960 d 14 = 3.400 n 7 =} 1.49241 ν 7 = 57.66 r 15 = -22.9520 ( _{aspherical) d 15 = 20.000 r 16 =} ∞ ( eye point) aspherical coefficients (first 2nd surface) P = 1.0000, E = -0.81563 × 10 ⁻³ , F = 0.28 444 × 10 ⁻⁴ G = −0.17376 × 10 ⁻⁶ (third surface) P = 1.0000 , E = −0.75454 × 10 ⁻³ , F = −0.1 9287 × 10 ⁻⁵ G = 0.13014 × 10 ⁻⁶ (sixth surface) P = 1.0000, E = −0.88233 × ^{10 -4, F = -0.2 0871 ×} 10 -5 G = 0.86395 × ^{10 -6} (ninth surface) P = 1.0000, E = -0.14459 × 10 -2, F = 0.39 259 × 10 -4 G = -0.34782 × 10 -5 ( Fifteenth surface) P = 1.0000, E = 0.79267 × 10 ⁻⁴ , F = −0.5 7040 × 10 ⁻⁶ G = 0.68501 × 10 ⁻⁸ Magnification 0.42 0.55 0.73 Incident angle 2ω 50.6 ° 33.9 ° 23.9 ° D ₁ 12.3860 10.2228 6.7
329 D ₂ 1.0000 3.1633 6.6
531 D ₃ 19.0000 20.5484 19.8
291 D ₄ 5.0484 3.5000 4.2
193 β _2T / β _2W −β _3T / β _3W = 0.607, −f _W
/ F ₁ = 0.908, f ₂ / f ₃ = 0.557 The first embodiment has a configuration as shown in FIG. 7, and the objective lens has a negative refracting power and is a fixed first lens group G ₁ A second lens group G ₂ which has a positive refractive power and is a moving group, and a prism P ₁ which is a reflecting member having a positive refractive power (the second lens group G ₂ has a convex surface) and a positive lens The third lens group G ₃ is a moving group having a refractive power, and the eyepiece lens is a reflecting lens P ₂ and the fourth lens group G is a fixed group having a positive refractive power.
_{It consists of four} . With this optical system, the second objective lens
The lens group G ₂ and the third lens group G ₃ are moved in a direction along the optical axis to perform zooming and diopter correction. Further, since the object-side surface of the prism P ₁ is a convex surface, the angle of incidence on the third lens group G ₃ is gentle and distortion is less likely to occur. Therefore, good performance is obtained without using an aspherical surface for the third lens group G ₃ .

In the optical system of Example 1, the image-side surface r _{2 of} the first lens group G ₁ , the eye-side surface r _{4 of} the second lens group G ₂ , the convex surface r ₅ of the prism P ₁ , and the fourth surface The surface r ₁₃ on the eye side of the lens group G ₄ is an aspherical surface.

The second embodiment has the configuration shown in FIG.
It has the same configuration as. The object-side surface of the prism P ₁ which is a reflecting member is a surface concave to the object side. In this case, since the condition of total reflection is not satisfied inside the prism, it is preferable to vapor-deposit aluminum on the prism. The third lens group G ₃ is a biconvex lens.

In this embodiment, the surfaces r ₂ , r ₄ , r ₇ , r
₁₃ is an aspherical surface.

The third embodiment has the configuration shown in FIG. 9, and includes a first lens group G ₁ which is a fixed lens group having a negative refractive power, and a second lens group G ₂ which is a movable lens group having a positive refractive power. , P ₁ which is a reflecting member having a positive refractive power (the surface on the object side is a convex surface)
And an objective lens composed of a third lens group G ₃ having a negative refractive power and being a moving group, and an eyepiece composed of a reflecting member P ₂ and a fourth lens group G ₄ having a positive refractive power and being a fixed group. It consists of a lens. Here, the second lens group G ₂ and the third lens group G ₃
And are moved to perform zooming and diopter correction.

Since the third lens group G ₃ has a negative refracting power and a reflecting member having a positive refracting power is arranged on the object side, most of the light rays satisfy the condition of total reflection inside the prism.

In the third embodiment, the surfaces r ₂ , r ₄ , r ₅ , r
₁₃ is an aspherical surface.

The fourth embodiment has the configuration shown in FIG. 10, and includes a first lens group G ₁ which is a fixed lens group having a negative refractive power, and a second lens group G ₂ which is a movable lens group having a positive refractive power. , A third lens group G ₃ which is a fixed group having a negative refracting power, a mirror of a reflecting member P ₁ having two reflecting surfaces, and two lenses of a positive first lens and a negative second lens. In other words, the objective lens including the fourth lens group G ₄ which is a moving group having a positive refracting power as a whole, and the eyepiece of the reflecting member P ₂ and the fifth lens group G ₅ which has a positive refracting power and is a fixed group. Consists of. In Example 4, the optical path length required for disposing the reflecting member after the first and second lens groups cannot be taken, so that the second lens group G ₂ is followed by the fixed group G ₃ having a negative refractive power. They are arranged so as to have a large optical path length. Although the reflecting member P ₁ is not shown in FIG. 10 and the data, it is necessary to dispose two mirrors between the third lens group G ₃ and the fourth lens group G ₄ as can be seen from the figures and the data. The intervals are.

The shape of the aspherical surface used in each of the above embodiments is
When the direction of the optical axis is x and the direction perpendicular to the optical axis is y, it is expressed as follows.

Here, C is the curvature of the apex of the aspherical surface, P is the conic constant, and E, F, and G are aspherical surface coefficients.

[0029]

The present invention can be arranged in a thin and compact camera by arranging a reflecting member having two reflecting surfaces between the moving lens groups of the objective lens, and a driving mechanism for the moving lens groups can be easily formed. In addition, a real image type variable magnification viewfinder optical system having good optical performance can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a finder optical system of the present invention.

FIG. 2 is a perspective view of the optical system shown in FIG.

FIG. 3 is a diagram showing another configuration of the finder optical system of the present invention.

FIG. 4 is a perspective view of the optical system of FIG.

FIG. 5 is a diagram schematically showing a configuration of a finder optical system of the present invention.

FIG. 6 is a diagram schematically showing another configuration of the finder optical system of the present invention.

FIG. 7 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 11 is an aberration curve diagram of Example 1 at the wide-angle end.

FIG. 12 is a diagram of aberration curves at the intermediate focal length of Example 1.

FIG. 13 is an aberration curve diagram for Example 1 at the telephoto end.

FIG. 14 is an aberration curve diagram of Example 2 at the wide-angle end.

FIG. 15 is an aberration curve diagram for Example 2 at the intermediate focal length.

FIG. 16 is an aberration curve diagram for Example 2 at the telephoto end.

FIG. 17 is an aberration curve diagram of Example 3 at the wide-angle end.

FIG. 18 is an aberration curve diagram for Example 3 at the intermediate focal length.

19 is an aberration curve diagram for Example 3 at the telephoto end. FIG.

FIG. 20 is an aberration curve diagram for Example 4 at the wide-angle end.

FIG. 21 is an aberration curve diagram for Example 4 at the intermediate focal length.

FIG. 22 is an aberration curve diagram for Example 4 at the telephoto end.

FIG. 23 is a diagram showing a configuration of a conventional finder optical system.

FIG. 24 is a diagram showing the configuration of another conventional finder optical system.

FIG. 25 is a perspective view of the conventional example shown in FIG.

FIG. 26 is a diagram showing the configuration of another conventional finder optical system.

27 is a perspective view of the conventional example shown in FIG.

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[Procedure amendment]

[Submission date] May 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

2. The real image type variable power viewfinder optical system according to claim 1, wherein the movable lens group on the pupil side is located in the vicinity of an intermediate image forming plane.

[Procedure amendment]

[Submission date] August 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020] In the optical system of the first embodiment, the surface _{r 2} of the first lens group _{G 1} of the eye-side, second lens group _{G 2} of the eye-side surface _{r 4,} the convex surface _{r 5} of the prism _{P 1,} 4 The surface r ₁₃ on the eye side of the lens group G ₄ is an aspherical surface.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

The fourth embodiment has the configuration shown in FIG. 10, and includes a first lens group G ₁ which is a fixed lens group having a negative refractive power, and a second lens group G ₂ which is a movable lens group having a positive refractive power. , A third lens group G ₃ which is a fixed group having a negative refracting power, a mirror of a reflecting member P ₁ having two reflecting surfaces, and two lenses of a positive first lens and a negative second lens. In other words, the objective lens including the fourth lens group G ₄ which is a moving group having a positive refracting power as a whole, and the eyepiece of the reflecting member P ₂ and the fifth lens group G ₅ which has a positive refracting power and is a fixed group. Consists of. In Example 4, the optical path length required for disposing the reflecting member after the first and second lens groups cannot be taken, so that the second lens group G ₂ is followed by the fixed group G ₃ having a negative refractive power. They are arranged so as to have a large optical path length. Although the reflecting member P ₁ is not shown in FIG. 10 and data, a mirror having two reflecting surfaces is arranged between the third lens group G ₃ and the fourth lens group G ₄ as can be seen from the figures and data. It has the necessary interval.

Claims (2)

[Claims] 1. A variable power system comprising an objective lens having a positive refracting power as a whole and an eyepiece lens having a positive refracting power, said objective lens having two moving lens groups, A reflecting member having at least two reflecting surfaces is disposed between the two moving lens groups, and the moving amount on the pupil side of the reflecting member is greater than the moving amount of the moving lens group on the object side of the reflecting member. A real-image variable-magnification viewfinder optical system characterized by reducing the amount of lens group movement. 2. The real image type variable power viewfinder optical system according to claim 1, wherein the movable lens group on the pupil side is located in the vicinity of an intermediate image forming plane.