JP2002090658A - Real image type finder optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, high-magnification real image type finder optical system, which can have its magnification area switched by replacing the least number of components. SOLUTION: This optical system comprises a positive objective optical system (TA), a mirror (MR), a roof prism (PD), and a positive ocular optical system (SE) in order from an object side. The objective optical system (TA) comprises 1st to 3rd lens groups (Gr1 to Gr3) and a 4-th lens group (Gr4A or Gr4B), and is zoomed by moving the 2nd and 3rd lens groups (Gr2, Gr3). One of the two 4-th lens groups (Gr4A, Gr4B) is switched and arranged in the optical path as the closest to image-side lens group of the objective optical system (TA), so as to optionally vary the focal length of the objective optical system (TA).

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 finder optical system, and more particularly to a Keplerian real image type finder optical system having a zooming function.

[0002]

2. Description of the Related Art A camera requires a finder for confirming a subject image. For example, a lens shutter camera using a silver halide film is equipped with a finder optical system separate from a photographing optical system. In recent years, C
A so-called digital camera configured by a charge element such as a CD (Charge Coupled Device) has become widespread, and a separate finder optical system is often mounted thereon.

When a camera equipped with a finder optical system separate from the photographing optical system is equipped with a zoom lens as the photographing optical system, the finder optical system corresponds to the magnification range and the magnification ratio of the photographing optical system. Need to be done. JP-A-6-3
Japanese Patent No. 24266 proposes a finder optical system that includes a plurality of objective optical systems having different focal lengths, and switches one of them in an optical path to switch a zooming magnification range. Also, JP-A-11
Japanese Patent Application Laid-Open No. 242262 proposes a finder optical system that includes a teleconverter and a wide converter, and switches one of the magnification ranges by attaching one of them to the object side of the objective optical system.

[0004]

However, Japanese Patent Laid-Open No. 6-3 / 1994
If the variable magnification area is configured to be switchable as proposed in Japanese Patent Application Laid-Open No. 24266 and Japanese Patent Application Laid-Open No. H11-242262, the components of the finder optical system become large, which leads to an increase in the size of the camera. become. When the camera is equipped with a finder optical system that is separate from the photographing optical system, it is not limited to the configuration in which the zooming area can be switched, and various specifications (zooming area, zooming ratio, It is necessary to separately prepare a dedicated finder optical system corresponding to the above. Since a special mold is required for this, a finder optical system that can use parts in common even if the specifications are different is desired.

The present invention has been made in view of such a situation, and provides a small-size, high-magnification real-image type finder optical system capable of switching a magnification area by changing the minimum number of parts. The purpose is to:

[0006]

In order to achieve the above object, a real image type finder optical system according to the first invention comprises, in order from the object side, an objective optical system having a positive power, an erecting optical system, An eyepiece optical system having a positive power, wherein the objective optical system comprises a plurality of lens groups, and a real image type variable magnification finder optical system which performs magnification by moving at least one of the lens groups; The focal length of the objective optical system can be arbitrarily changed by changing only the lens group closest to the image among the lens groups constituting the optical system.

According to a second aspect of the present invention, there is provided a real image type finder optical system according to the first aspect, wherein a lens group closest to the image side of the objective optical system has a negative power.

According to a third aspect of the present invention, in the real image type viewfinder optical system according to the first aspect of the present invention, the most image side lens group of the objective optical system has a positive power.

According to a fourth aspect of the present invention, in the real image type viewfinder optical system according to the first, second or third aspect of the present invention, the most image-side lens unit of the objective optical system is fixed during zooming. Features.

According to a fifth aspect of the present invention, in the real image type finder optical system according to the first, second, third or fourth aspect of the present invention, the most image side surface of the objective optical system is a flat surface. And

A real image type finder optical system according to a sixth aspect of the present invention is the real image type finder optical system according to the first, second, third, fourth or fifth aspect of the invention, wherein a focal length is set as a lens group closest to the image side of the objective optical system. A plurality of different lens groups, and any one of them is switched and arranged in the optical path.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A real image finder optical system embodying the present invention will be described below with reference to the drawings. FIG.
Next, an embodiment of a finder optical system having a switching structure of the fourth lens group (Gr4A, Gr4B) will be described. This finder optical system is a real image type variable magnification finder optical system separate from a photographing optical system (not shown), and includes, in order from the object side, an objective optical system (TA) having positive power and a mirror (MR). ), A roof prism (PD), and an eyepiece optical system (SE) having positive power (EP: pupil), a mirror (MR) and a roof prism (P
D) constitutes an erecting optical system.

In the objective optical system (TA), each lens group has a lens 1
It is composed of four positive / negative / positive / negative lens groups, and performs zooming by moving the second and third lens groups (Gr2, Gr3) along the optical axis (AX). It has become. Further, as a lens group closest to the image side of the objective optical system (TA), two fourth lens groups (Gr4A, Gr4B) having different focal lengths
And the movement (rotation, translation, etc.) of the lens holder (LH) holding the fourth lens group (Gr4A, Gr4B) causes any one of the two fourth lens groups (Gr4A, Gr4B) to move. One is switched and arranged in the optical path. Note that the lens holder (LH) is configured to interlock with zooming of a photographing optical system (not shown), but the switching means is not limited to this.

In the finder optical system shown in FIG. 1, the focal length of the objective optical system (TA) changes according to the focal length of the fourth lens group (Gr4A, Gr4B) disposed in the optical path, so that the focal length differs. By fixing a plurality of lens groups to the lens holder (LH), the focal length of the objective optical system (TA) can be arbitrarily changed. If the focal length of the objective optical system (TA) changes, the finder magnification also changes, so that the magnification range of the finder optical system can be easily expanded.

For example, when the fourth lens group (Gr4A) is disposed in the optical path, the finder magnification ΓA is set to 0.37 to 2.12.
The finder magnification ΓB when the fourth lens group (Gr4B) is arranged in the optical path is 0.32 to 1.83. If zooming to the wide side is performed with 第 A = 0.37 when the fourth lens group (Gr4A) is arranged in the optical path, the fourth lens group (Gr4B) is switched and arranged in the optical path and ΓB = 0.32. When the zooming is performed on the telephoto side with the fourth lens group (Gr4B) arranged in the optical path and ΓB = 1.83, the fourth lens group (Gr4A)
Are switched and arranged in the optical path, so that ΓA = 2.12. However,
The image plane position that changes according to the fourth lens group (Gr4A, Gr4B) arranged in the optical path is corrected by moving the second lens group (Gr2) or the third lens group (Gr3).

As described above, the finder optical system shown in FIG. 1 has a configuration in which only the lens unit closest to the image among the lens units constituting the objective optical system (TA) is changed. Although it is twice as large, it is possible to switch the magnification range by changing the minimum number of parts. Japanese Unexamined Patent Application Publication No. 11-2
In the finder optical system described in Japanese Patent No. 42262, the focal length of the objective optical system is changed by a converter attached to the object side of the objective optical system. However, since the converter used must constitute an afocal system,
The overall length of the finder optical system increases, and the lens outer diameter of the converter section also increases. As a result, it is difficult to achieve compactness. As shown in FIG. 1, by changing only the lens group closest to the image among the lens groups constituting the objective optical system (TA), the objective optical system (TA) is changed.
If the configuration is such that the focal length of (TA) is switched, the overall length of the finder optical system and the enlargement of the lens outer diameter can be suppressed.

When a finder optical system separate from the photographing optical system is mounted on the camera, as described above, a dedicated finder optical system corresponding to various specifications (magnification area, magnification ratio, size, etc.) of the camera is used. It is necessary to prepare a finder optical system individually.
However, among the lens groups constituting the objective optical system (TA), only the lens group closest to the image is changed.If the above-described configuration is used, it is possible to commonly use parts even if the specifications are different. . 2 (A) to 2 (C) show an embodiment of a finder optical system in which parts can be commonly used.

The finder optical system shown in FIG. 2A is a real image type variable magnification finder optical system separate from the photographing optical system (not shown), similarly to FIG. 1, and has a positive power in order from the object side. Objective (TA), mirror (MR), and roof prism
(PD) and an eyepiece optical system (SE) having positive power (EP: pupil), and a mirror (MR) and a roof prism (PD) constitute an erecting optical system. The objective optical system (TA) and the mirror (MR) are provided in the first holder (H1), and the roof prism (PD) and the eyepiece optical system (SE) are provided in the second holder (H2). I have. The objective optical system (TA) has four positive, negative, positive and negative lens groups (Gr1 to
Gr3, Gr4A), and the second and third lens groups (Gr2, Gr4,
Gr3) moves along the optical axis (AX) to perform zooming.

The viewfinder optical system shown in FIG. 2A is obtained by widening the angle of view of the viewfinder optical system shown in FIG. 2B. The fourth lens group (Gr4B) used here has a different focal length from the fourth lens group (Gr4A) in FIG. Therefore, the fourth
When the lens group (Gr4B) is replaced, the finder magnification changes because the focal length of the objective optical system (TA) changes. For example, the viewfinder magnification ranges from 0.37 to 2.12 {Fig.
1.83 {FIG. 2 (B)}. Since the optical path length increases when the variable magnification area is changed in this manner, the second holder (H2) is replaced with the second holder (H2 ') in order to adjust the image plane position.
Replace with By changing to the second holder (H2 '), the distance between the mirror (MR) and the roof prism (PD) is increased, and the image plane position is corrected. The changed part is the fourth lens group (Gr4A, Gr4B)
And the second holder (H2, H2 ') alone, it is possible to easily change the magnification range of the finder optical system. For example, the specifications of the finder optical system can be easily changed from telephoto zoom to wide-angle zoom. In addition, instead of replacing with the second holder (H2 '), the first and second holders
A spacer may be arranged between (H1, H2).

The viewfinder optical system of FIG. 2A is obtained by extending the entire length of the viewfinder optical system of FIG. 2A.
Instead of the fourth lens group (Gr4A) and the mirror (MR), the fourth lens group (G
r4C) is used. Also, instead of the first holder (H1), the first holder (H1) having a length suitable for the objective optical system (TA) having a longer overall length is used.
A holder (H1 ') is used. 4th lens group (Gr4A)
Is the lens located closest to the image side of the objective optical system (TA), and if a prism configured to integrate this with the mirror (MR) is used as the fourth lens group (Gr4C), the finder magnification is changed. Without the need for a camera, the overall length of the viewfinder can be increased to fit the size of the camera.

FIGS. 3A and 3B show the total viewfinder lengths (L1, L2).
Shows the change in Note that FIG. 3A corresponds to FIG. 2A, and FIG. 3B corresponds to FIG. 2C. As shown in FIG. 3A, when the optical path before and after the reflecting surface formed by the mirror (MR) is filled with air, the entire length of the finder (L1) is short. As shown in FIG. 3B, when a medium (glass, plastic, or the like) forming the prism exists in the optical path before and after the reflection surface formed by the fourth lens group (Gr4C), the medium (prism) Occupied by the air becomes shorter. Therefore, since the actual length of the optical path is increased, the total length of the finder (L2) is increased with a small number of components.

Next, a finder optical system having preferable characteristics for changing only the lens group closest to the image among the lens groups constituting the objective optical system (TA) will be described. FIG.
7 are lens configuration diagrams respectively corresponding to the real image type viewfinder optical systems of the first to fourth embodiments, and the lens arrangement and the optical path at the wide end [W] are switched from the standard state (A) to the standard state (A). (B) is shown. The standard state (A) has a variable magnification area on the high magnification side (tele side), and the switching state (B) has a variable magnification area on the low magnification side (wide side).

The first to fourth embodiments (FIGS. 4 to 7)
A real image type variable magnification finder optical system separate from a photographing optical system (not shown), and an objective optical system (TA) having positive power and an erecting optical system constituting an erecting optical system in order from the object side. prism
(EP) and an eyepiece optical system (SE) having positive power (EP: pupil). The objective optical system (TA) includes a plurality of lens groups, and zooming is performed by moving at least one of the lens groups. Arrows mj (j =
1, 2, 3, 4) schematically show the movement of the j-th lens unit (Grj) along the optical axis (AX) during zooming from the wide-angle end [W] to the telephoto end [T]. .

In the first embodiment (FIG. 4), the objective optical system
(TA) includes, in order from the object side, a first lens group (Gr1) having positive power and a second lens group (Gr2) having negative power.
And a third lens group (Gr3) having a positive power and a fourth lens group (Gr4A or Gr4B) having a negative power, and the second and third lens groups (Gr2, Gr3) are zoomed. Configuration. Each lens group (Gr1 to Gr3, Gr4A, Gr4B) is composed of one lens, and the object side surface of the erecting prism (PR) is a condenser lens surface. Also, the fourth
The fourth lens (G4A or Gr4A) constituting the lens group (Gr4A or Gr4B)
G4B) has a flat surface on the image side.

In the second embodiment (FIG. 5), the objective optical system
(TA) includes, in order from the object side, a first lens group (Gr1) having positive power and a second lens group (Gr2) having negative power.
A fifth lens group (Gr5A) including a third lens group (Gr3) having positive power, a fourth lens group (Gr4) having negative power, and a fifth lens (G5A) having negative power. Alternatively, a fifth lens group (Gr5B) composed of a plane-parallel plate (G5B) is provided, and the second to fourth lens groups (Gr2 to Gr4) are zoomed. Each lens group (Gr1 to Gr4, Gr5A, Gr5B) is composed of one lens, and the object side surface of the erecting prism (PR) is a condenser lens surface. In addition, the fifth
Fifth lens (G5A or Gr5A) constituting the lens group (Gr5A or Gr5B)
G5B) has a flat surface on the image side.

In the third embodiment (FIG. 6), the objective optical system
(TA) includes, in order from the object side, a first lens group (Gr1) having positive power and a second lens group (Gr2) having negative power.
And a third lens group (Gr3) having a negative power and a fourth lens group (Gr4A or Gr4B) having a positive power, and the second and third lens groups (Gr2, Gr3) are zoomed. Configuration. The first to third lens groups (Gr1 to Gr3) each include one lens, and the fourth lens group (Gr4A, Gr4B)
Consists of a biconvex lens (G4A, G4B) and a prism (G5A, G5B) having a condenser lens surface formed on the side surface of the pupil (EP).

In the fourth embodiment (FIG. 7), the objective optical system
(TA) includes, in order from the object side, a first lens group (Gr1) having negative power and a second lens group (Gr2) having positive power.
And a third lens group (Gr3) having a negative power and a fourth lens group (Gr4A or Gr4B) having a positive power. The first to third lens groups (Gr1 to Gr3) are zoomed. Configuration. The first to third lens groups (Gr1 to Gr3) each include one lens, and the fourth lens group (Gr4A, Gr4B)
Is composed of biconvex lenses (G4A, G4B) and prisms (G5A, G5B), and the object side surface of the erect prism (PR) is a condenser lens surface. Further, the fourth lens group (Gr4A or Gr4
The fifth lens (G5A or G5B) constituting B) has a flat surface on the image side.

As in the first embodiment, the objective optical system (T
It is desirable that the lens unit closest to the image in A) has negative power. By giving negative power to the lens group closest to the image side, it is possible to lengthen the lens back of the objective optical system (TA), and the erecting optics composed of a reflective surface in the secured lens back part A system (a roof prism, a roof mirror, etc.) can be arranged.

As in the third and fourth embodiments, it is desirable that the lens group closest to the image in the objective optical system (TA) has a positive power. In the real image type viewfinder optical system, in order to prevent the incident light from the objective optical system (TA) to the eyepiece optical system (SE) from being vignetted, the light incident on the imaging surface of the objective optical system (TA) is It is desirable that telecentricity is secured to some extent. By giving the positive lens power to the lens group closest to the image side of the objective optical system (TA), the pupil position of the light beam incident on the image plane can be brought closer to the object side, so the telecentricity of the exit light beam Nature can be secured.

As in the first to fourth embodiments, it is desirable that the lens group closest to the image in the objective optical system (TA) be fixed during zooming. Changing the fixed lens group is easier in terms of the configuration of the zoom mechanism than changing the other movable lens groups. If you try to change the focal length of the objective optical system (TA) by changing the lens group that moves during zooming, the image point moves due to zooming, but even if you change the fixed lens group closest to the image side No image point movement due to zooming occurs. Simply changing the power of the lens group will reduce or enlarge the focal length of the entire objective optical system (TA). Therefore, if the lens group closest to the image is fixed during zooming, the focal length of the objective optical system (TA) can be changed with a simpler configuration.

As in the first embodiment, the objective optical system
It is desirable that the most image-side surface of (TA) be a flat surface. In the finder configuration in which the subject image is erected by image inversion between the objective optical system (TA) and the eyepiece optical system (SE), as shown in FIG. Mirror surface (MR)
Rather than the objective optical system (T) as shown in FIG.
If the reflecting surface behind A) is formed of a prism, the number of parts can be reduced and the entire length of the finder can be increased. That is, by using a prism having an optical path length as needed, it is possible to adjust the entire length of the finder without increasing the number of components. If the surface closest to the image side of the objective optical system (TA) is made flat, even if the lens unit closest to the image side is formed of a prism, the power does not change, so that the application is easy.

As in the first to fourth embodiments (FIGS. 4 to 7), only the most image-side lens group among the lens groups constituting the objective optical system (TA) is changed. By
In a case where the focal length of the objective optical system (TA) can be arbitrarily changed, it is desirable to satisfy the following conditional expression (1). 5 <| ΓAW / (φA−φB) | <60… (1) where ΓAW: finder magnification at wide end [W] in standard condition (A), φA: objective optical system in standard condition (A) ( TA), the power of the lens group closest to the image, φB: the power of the lens group closest to the image of the objective optical system (TA) in the switching state (B).

Conditional expression (1) defines a preferable power ratio of the lens group closest to the image in the objective optical system (TA) in each of the states (A) and (B). When the lower limit of conditional expression (1) is exceeded, the standard condition
Since the power ratio between (A) and the switching state (B) becomes too large, it becomes difficult to secure the luminous flux and correct the aberration at the time of switching. Conversely, if the upper limit of conditional expression (1) is exceeded, the power ratio becomes too small and the objective optical system (T
The difference in the focal lengths in (A) becomes small, and the object of the present invention cannot be achieved.

The lens used in each embodiment is a refraction type lens which deflects an incident light beam by refraction.
(That is, a lens of a type in which deflection is performed at the interface between media having different refractive indices), but the lens used is not limited to this. For example, a diffractive lens that deflects an incident light beam by diffraction, a hybrid refraction / diffraction lens that deflects an incident light beam by a combination of diffraction and refraction, and a refractive index distribution type that deflects an incident light beam according to a refractive index distribution in a medium. A lens or the like may be used.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of a real image type finder optical system embodying the present invention will be described more specifically with reference to construction data, aberration diagrams and the like. Examples 1 to 4 given here as examples correspond to the above-described first to fourth embodiments, respectively, and are lens configuration diagrams showing the first to fourth embodiments (FIGS. 4 to 7). ) Correspond to corresponding Examples 1-4
Are shown, respectively.

In the construction data in the standard state (A) and the switching state (B) of each embodiment, si (i = 1, 2, 3,...)
Is the i-th surface counted from the object (i.e., subject) side, and r
i (i = 1,2,3, ...) is the radius of curvature (mm) of surface si, di (i = 1,2,
(3, ...) indicates the i-th axial distance (mm) counted from the object side, and Ni (i = 1,2,3, ...) indicates the i-th optical axis counted from the object side. Refractive index (Ne) of element (Gi, GiA, GiB) for e-line, ν
i (i = 1,2,3, ...) is the i-th optical element (G
i, GiA, GiB) are shown. However, for the construction data in the switching state (B),
Only the changed part at the time of switching is shown. Also, the surface si marked with * indicates that it is a surface composed of an aspheric surface, and is defined by the following equation (AS) representing the surface shape of the aspheric surface.

Y = {C0 · X ² } / {1 + √ (1-ε · C0 ² · X ² )} + ΣAi · X ⁱ (AS) where, in the formula (AS), Y: height X , The displacement in the direction of the optical axis (AX) from the reference plane at the position of X, X: the height in the direction perpendicular to the optical axis (AX), C0: paraxial curvature, ε: quadratic surface parameter, Ai: Aspherical coefficient of the following equation (ΣAi ・ X ⁱ = A4 ・ X ⁴ + A6 ・ X ⁶ + A8 ・ X ⁸ + A1
0 · X ¹⁰ ).

In the construction data, the distance (di) between the top surfaces of the axes, which changes during zooming, is set at the wide end.
[W]-middle [M]-variable air spacing at tele end [T].
The viewfinder magnification (ΓA, ΓB) and the objective optical system (T) in the standard state (A) and the switching state (B) corresponding to each magnification state [W], [M], [T]
The focal length (fA, fB; mm) of A) and the aspherical data are shown together with other data, and the corresponding values of the conditional expression (1) are shown in Table 1.

8 and 9, FIGS. 10 and 11, FIGS. 12 and 13, FIGS. 14 and 15 show the first to fourth embodiments (FIGS. 4 to 5) in the standard state (A) and the switching state (B). It is an aberration figure respectively corresponding to 7). 8 to 15, (A) to (C) show aberrations at the wide end [W] of each embodiment, (D) to (F) show aberrations at the middle [M] of each embodiment, and (G) ) To (I) show aberrations at the telephoto end [T] in each embodiment, and (A), (D), and (G) show astigmatism (Diopt .: diopter),
(B), (E), (H) are distortion (%), (C), (F), (I) are chromatic aberration of magnification
(Rad .: Rashidian). In each aberration diagram, the thick solid line is the aberration for the e-line on the tangential surface, the thin solid line is the aberration for the e-line on the sagittal surface, the short dashed line is the aberration for the C line on the tangential surface, and the two-dot chain line is the sagittal surface. , The long dashed line represents the aberration with respect to the g-line on the tangential surface, and the dashed line represents the aberration with respect to the g-line on the sagittal surface, with respect to the half angle of view (Rad.).

<< Example 1 ... Standard condition (A) >> A = 0.37 [W] to 0.89 [M] to 2.12 [T], fA (mm) = 6.21 [W] to 14.93 [M] to 34.96 [T] [Surface] [Radius of curvature] [Shaft upper surface interval] [Refractive index] [Abbe number] s1 r1 = 23.228 d1 = 1.908 N1 = 1.4933 ν1 = 57.82… G1 (Gr1) s2 * r2 = -11.601 d2 = 0.620 ~ 4.245 ~ 6.532 s3 * r3 = -7.475 d3 = 0.800 N2 = 1.538 ν2 = 39.70… G2 (Gr2) s4 * r4 = 4.514 d4 = 11.648 to 5.788 to 0.350 s5 * r5 = 7.367 d5 = 1.725 N3 = 1.524 ν3 = 52.20… G3 ( Gr3) s6 * r6 = -7.906 d6 = 0.300-2.535-5.686 s7A * r7A = -37.459 d7A = 0.800 N4A = 1.588 ν4A = 30.36… G4A (Gr4A) s8A r8A = ∞ d8A = 13.042 s9 r9 = 10.753 d9 = 21. = 1.493 ν5 = 57.82… G5 (PR) s10 r10 = ∞ d10 = 1.000 s11 * r11 = 24.421 d11 = 0.800 N6 = 1.626 ν6 = 24.01… G6 (SE) s12 r12 = 8.753 d12 = 0.300 s13 * r13 = 6.948 d13 = 2.190 N7 = 1.493 ν7 = 57.82… G7 (SE) s14 * r14 = -14.852

[Aspherical surface data] s2: ε = -11.972, A4 = -5.334 × 10 ^-4 , A6 = 2.124 × 10 ^-5 , A8 = -3.781 × 10 ^-7 s3: ε = 1, A4 = -4.223 ^{× 10 -4, A6 = 5.237 ×} 10 -5, A8 = 5.193 × 10 -7 s4: ε = -6.032, A4 = 3.507 × 10 -3, A6 = -4.304 × 10 -4, A8 = 2.335 × 10 - ⁵ s5: ε = 2.317, A4 = -4.383 × 10 ^-4 , A6 = -1.474 × 10 ^-5 , A8 = 2.122 × 10 ^-5 s6: ε = -3.198, A4 = 5.957 × 10 ^-4 , A6 =- 1.180 × 10 ^-4 , A8 = 3.604 × 10 ^-5 s7A: ε = -9.223 × 10 ² , A4 = -1.670 × 10 ^-3 , A6 = 1.974 × 10 ^-4 , A8 = -1.075 × 10 ^-5 s11: ε = 19.568, A4 = 4.073 × 10 ^-4 , A6 = -1.842 × 10 ^-5 s13: ε = -0.859 s14: ε = 1, A4 = 3.649 × 10 ^-4 , A6 = -1.433 × 10 ^-5 , A8 = -5.496 × 10 ^-8

<< Embodiment 1 ... Changes in Switching to Switching State (B) >> ΓB = 0.32 [W] to 0.77 [M] to 1.83 [T], fB (mm) = 5.37 [W] to 12.91 [ M] ~ 30.24 [T] [Surface] [Radius of curvature] [Shaft upper surface interval] [Refractive index] [Abbe number] s7B * r7B = -139.859 d7B = 0.800 N4B = 1.583 ν4B = 30.36… G4B (Gr4B) s8B r8B = ∞ d8B = 11.219

[Aspherical surface data] s7B: ε = -1.201 × 10 ⁴ , A4 = -3.412 × 10 ^-4 , A6 = 2.156 × 10 ^-5 , A8 = -7.350 × 10 ^-7

<< Embodiment 2—Standard Condition (A) >> A = 0.37 [W] to 0.89 [M] to 2.12 [T], fA (mm) = 6.21 [W] to 14.93 [M] to 34.96 [T] [Surface] [Curvature radius] [Shaft upper surface interval] [Refractive index] [Abbe number] s1 * r1 = 51.652 d1 = 1.737 N1 = 1.493 ν1 = 57.82… G1 (Gr1) s2 * r2 = -8.642 d2 = 0.660 to 4.514 Up to 6.000 s3 * r3 = -6.258 d3 = 0.800 N2 = 1.538 ν2 = 39.70… G2 (Gr2) s4 * r4 = 4.177 d4 = 10.335 to 5.182 to 0.300 s5 * r5 = 6.126 d5 = 2.668 N3 = 1.524 ν3 = 52.20… G3 (Gr3) s6 * r6 = -5.551 d6 = 0.300 to 1.600 to 4.595 s7 * r7 = -46.903 d7 = 0.800 N4 = 1.626 ν4 = 24.01… G4 (Gr4) s8 r8 = 20.000 d8 = 0.400 to 0.400 to 0.800 s9A r9A = -46.548 d9A = 0.800 N5A = 1.588 ν5A = 30.36… G5A (Gr5A) s10A r10A = ∞ d10A = 11.826 s11 r11 = 10.753 d11 = 21.323 N6 = 1.493 ν6 = 57.82… G6 (PR) s12 r12 = ∞d12 = 1.000 r13 = 24.421 d13 = 0.800 N7 = 1.626 ν7 = 24.01… G7 (SE) s14 r14 = 8.753 d14 = 0.300 s15 * r15 = 6.948 d15 = 2.190 N8 = 1.493 ν8 = 57.82… G8 (SE) s16 * r16 = -14.852

[Aspherical surface data] s1: ε = 1, A4 = 6.090 × 10 ^-4 , A6 = -3.206 × 10 ^-5 , A8 = 1.799 × 10 ^-6 s2: ε = -5.186, A4 = 1.877 × 10 ^-4 , A6 = -2.142 × 10 ^-5 , A8 = 1.788 × 10 ^-6 s3: ε = 2.019, A4 = -2.090 × 10 ^-3 , A6 = 3.472 × 10 ^-4 , A8 = -3.038 × 10 ^-6 s4: ε = -3.899, A4 = -1.254 × 10 ^-3 , A6 = 1.536 × 10 ^-4 , A8 = -1.675 × 10 ^-6 s5: ε = -1.799, A4 = 2.690 × 10 ^-4 , A6 = 2.150 × 10 ^-5 , A8 = 4.485 × 10 ^-6 s6: ε = -2.626, A4 = -7.908 × 10 ^-4 , A6 = 3.000 × 10 ^-5 , A8 = 6.845 × 10 ^-6 s7: ε = 236.369, A4 = 5.392 × 10 ^-4 , A6 = -4.015 × 10 ^-5 , A8 = 7.347 × 10 ^-6 s13: ε = 19.568, A4 = 4.073 × 10 ^-4 , A6 = -1.842 × 10 ^-5 s15: ε =- 0.859 s16: ε = 1, A4 = 3.649 × 10 ^-4 , A6 = -1.433 × 10 ^-5 , A8 = -5.496 × 10 ^-8

<< Embodiment 2 ... Changes in Switching to Switching State (B) >> ΓB = 0.32 [W] to 0.77 [M] to 1.83 [T], fB (mm) = 5.37 [W] to 12.91 [ M] ~ 30.24 [T] [Surface] [Radius of curvature] [Spacing of shaft upper surface] [Refractive index] [Abbe number] s9B r9B = ∞ d9B = 0.800 N5B = 1.583 ν5B = 30.36 ... = 10.165

<< Embodiment 3—Standard Condition (A) >> A = 0.40 [W] to 0.72 [M] to 1.32 [T], fA (mm) = 7.64 [W] to 13.78 [M] to 25.29 [T] [Surface] [Curvature radius] [Shaft upper surface interval] [Refractive index] [Abbe number] s1 r1 = 13.762 d1 = 2.690 N1 = 1.493 ν1 = 57.82… G1 (Gr1) s2 * r2 = -46.384 d2 = 0.636 ~ 5.565 ~ 8.941 s3 r3 = -27.283 d3 = 1.000 N2 = 1.493 ν2 = 57.82… G2 (Gr2) s4 * r4 = 6.733 d4 = 7.580〜3.937〜4.171 s5 r5 = -7.073 d5 = 1.000 N3 = 1.588 ν3 = 30.36 ・ ・ ・ G3 (Gr3 ) s6 r6 = -29.437 d6 = 5.034 ~ 3.747 ~ 0.138 s7A * r7A = 9.698 d7A = 3.130 N4A = 1.493 ν4A = 57.82… G4A (Gr4A) s8A * r8A = -6.860 d8A = 1.570 s9A r9A = ∞ d9A = 16.9 1.579 ν5A = 33.00… G5A (Gr4A) s10A r10A = -13.856 d10A = 3.150 s11 r11 = ∞ d11 = 28.496 N6 = 1.588 ν6 = 30.36… G6 (PR) s12 r12 = ∞ d12 = 0.500 s13 r13 = 22.136 d13 = 1.896 = 1.493 ν7 = 57.82… G7 (SE) s14 * r14 = -16.631

[Aspherical surface data] s2: ε = -18.968, A4 = 3.447 × 10 ^-5 , A6 = 7.776 × 10 ^-8 s4: ε = -0.304 s7A: ε = -3.494, A4 = -9.015 × 10 ^{− 5} , A6 = 6.597 × 10 ^-7 s8A: ε = -0.130 s14: ε = -1.749

<< Embodiment 3 ... Changed part when switching to switching state (B) >> ΓB = 0.32 [W] to 0.58 [M] to 1.06 [T], fB (mm) = 6.15 [W] to 11.10 [ [M] ~ 20.36 [T] [Surface] [Radius of curvature] [Shaft upper surface interval] [Refractive index] [Abbe number] s7B * r7B = 7.143 d7B = 3.130 N4B = 1.493 ν4B = 57.82… G4B (Gr4B) s8B * r8B = -6.860 d8B = 1.570 s9B r9B = ∞ d9B = 11.304 N5B = 1.578 ν5B = 33.00… G5B (Gr4B) s10B r10B = -13.856 d10B = 3.150

[Aspherical surface data] s7B: ε = -1.345, A4 = 8.899 × 10 ^-8 , A6 = -2.354 × 10 ^-6 s8B: ε = -1.617

<< Embodiment 4—Standard Condition (A) >> A = 0.40 [W] to 0.89 [M] to 1.40 [T], fA (mm) = 7.95 [W] to 17.74 [M] to 27.62 [T] [Surface] [Curvature radius] [Shaft upper surface interval] [Refractive index] [Abbe number] s1 r1 = -17.416 d1 = 1.000 N1 = 1.588 ν1 = 30.36… G1 (Gr1) s2 r2 = 13.365 d2 = 14.228 to 5.250 to 1.818 s3 * r3 = 7.103 d3 = 3.771 N2 = 1.527 ν2 = 56.38… G2 (Gr2) s4 * r4 = -10.769 d4 = 2.857 to 4.330 to 7.442 s5 * r5 = 10.114 d5 = 1.000 N3 = 1.588 ν3 = 30.36… G3 (Gr3 ) s6 r6 = 4.994 d6 = 1.819 to 7.825 to 9.635 s7A * r7A = 72.932 d7A = 1.252 N4A = 1.527 ν4A = 56.382 ... G4A (Gr4A) s8A r8A = -56.343 d8A = 0.300 s9A r9A = ∞5A = 15.09 = 56.382… G5A (Gr4A) s10A r10A = ∞ d10A = 1.000 s11 r11 = 13.109 d11 = 27.631 N6 = 1.527 ν6 = 56.382… G6 (PR) s12 r12 = ∞ d12 = 1.000 s13 * r13 = 46.311 d13 = 1.936 N7 = 1.493 ν7 = 57.82… G7 (SE) s14 r14 = -12.792

[Aspherical surface data] s3: ε = 1.015, A4 = -4.926 × 10 ^-4 , A6 = -1.600 × 10 ^-5 , A8 = 4.825 × 10 ^-7 , A10 = -1.822 × 10 ^-8 s4: ε = 1.137, A4 = 3.167 × 10 ^-4 , A6 = -2.225 × 10 ^-5 , A8 = 1.140 × 10 ^-6 , A10 = -3.089 × 10 ^-8 s5: ε = 1.131, A4 = -1.997 × 10 ^{− 4} , A6 = -3.713 × 10 ^-5 , A8 = -3.231 × 10 ^-7 , A10 = 8.868 × 10 ^-8 s7A: ε = 1, A4 = 8.860 × 10 ^-4 , A6 = -8.253 × 10 ^-5 , A8 = 6.307 × 10 ^-6 , A10 = -1.704 × 10 ^-7 s13: ε = 6.211, A4 = -1.307 × 10 ^-4 , A6 = 5.659 × 10 ^-6 , A8 = -2.604 × 10 ^-7 , A10 = 3.916 × 10 ^-9

<< Embodiment 4 ... Changed part when switching to switching state (B) >> ΓB = 0.32 [W] to 0.71 [M] to 1.12 [T], fB (mm) = 6.34 [W] to 14.18 [ [M] ～ 22.15 [T] [Surface] [Radius of curvature] [Shaft upper surface interval] [Refractive index] [Abbe number] s7B * r7B = 14.286 d7B = 1.252 N4B = 1.527 ν4B = 56.382… G4B (Gr4B) s8B r8B =- 56.343 d8B = 0.300 s9B r9B = ∞ d9B = 7.340 N5B = 1.527 ν5B = 56.382… G5B (Gr4B) s10B r10B = ∞ d10B = 1.000

[Aspherical surface data] s7B: ε = 1, A4 = 8.860 × 10 ⁻⁴ , A6 = −8.253 × 10 ⁻⁵ , A8 = 6.307 × 10 ⁻⁶ , A10 = −1.704 × 10 ⁻⁷

[0055]

[Table 1]

[0056]

As described above, according to the present invention, only the lens unit closest to the image side among the lens units constituting the objective optical system is changed, so that it is compact and has a high zoom ratio. It is possible to switch the magnification area by changing the minimum number of parts.

[Brief description of the drawings]

FIG. 1 is an optical configuration diagram showing a finder optical system having a switching structure of a fourth lens group.

FIG. 2 is an optical configuration diagram showing a finder optical system that allows common use of components.

FIG. 3 is an optical configuration diagram for explaining a change in the entire length of a finder.

FIG. 4 is a lens configuration diagram of the first embodiment (Example 1).

FIG. 5 is a lens configuration diagram of a second embodiment (Example 2).

FIG. 6 is a lens configuration diagram of a third embodiment (Example 3).

FIG. 7 is a lens configuration diagram of a fourth embodiment (Example 4).

FIG. 8 is an aberration diagram of the first embodiment in a standard state.

FIG. 9 is an aberration diagram of the first embodiment in a switching state.

FIG. 10 is an aberration diagram of the second embodiment in a standard state.

FIG. 11 is an aberration diagram of the switching state of the second embodiment.

FIG. 12 is an aberration diagram of Example 3 in a standard state.

FIG. 13 is an aberration diagram in a switching state of the third embodiment.

FIG. 14 is an aberration diagram of the fourth embodiment in a standard state.

FIG. 15 is an aberration diagram in a switching state of the fourth embodiment.

[Explanation of Symbols] TA: Objective optical system Gr4A: Fourth lens group Gr4B in standard state Gr4A in switched state Gr5A: Fifth lens group Gr5B in standard state: Fifth lens group in switched state MR… Mirror (Erect optical system) PD… Dach prism (Erect optical system) PR… Erect prism (Erect optical system) SE… Eyepiece optical system LH… Lens holder H1, H1 '… First holder H2, H2' … Second holder

 ────────────────────────────────────────────────── ─── Continued on the front page F-term (reference) 2H018 AA02 BA02 2H087 KA14 LA11 PA01 PA02 PA04 PA05 PA07 PA17 PB01 PB02 PB04 PB05 PB06 PB07 QA02 QA03 QA05 QA06 QA07 QA12 QA14 QA18 QA21 QA22 QA25 QA26 QA25 QA25 QA25 QA26 QA26 QA26 QA25 QA26 QA26 QA26 QA26 RA13 RA41 RA42 SA23 SA24 SA26 SA27 SA29 SA30 SA32 SA33 SA63 SA64 SA83 SB02 SB12 SB22 SB32 SB33 TA01 TA03

Claims (6)

[Claims] 1. An objective optical system having a positive power, an erecting optical system, and an eyepiece optical system having a positive power are arranged in order from the object side, and the objective optical system includes a plurality of lens groups. In a real image type variable magnification finder optical system that performs magnification by moving at least one of the lens groups, by changing only the most image side lens group among the lens groups constituting the objective optical system, A real image type finder optical system characterized in that the focal length of the objective optical system can be arbitrarily changed. 2. The real image type finder optical system according to claim 1, wherein a lens group closest to the image side of said objective optical system has a negative power. 3. The real image type viewfinder optical system according to claim 1, wherein a lens group closest to the image side of said objective optical system has a positive power. 4. The lens group closest to the image side of the objective optical system is fixed during zooming.
The real image type viewfinder optical system described in the above. 5. The real image type viewfinder optical system according to claim 1, wherein the most image side surface of said objective optical system is a flat surface. 6. A lens system according to claim 1, wherein a plurality of lens groups having different focal lengths are provided as a lens group closest to the image side of said objective optical system, and one of said lens groups is switched and arranged in an optical path. A real image type viewfinder optical system according to claim 1, 2, 3, 4, or 5.