JP2001013549A - Finder and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a finder of wide viewing angle and high-magnification, free from the occurrence of uneven brightness due to the total reflection at a half mirror joint surface, and having a long eye point(E.P.). SOLUTION: The finder is provided with a reverse-Galileian finder optical system with an objective lens L1 and an eyepiece L2, and a prism block P1 with the half mirror joint surface HM which is obliquely arranged inside the block P1 in order to align the 2nd other optical path with the 1st optical path of the finder optical system on the way of the optical path between the objective lens L1 and the eyepiece L2. In this case, a conditional inequality; 1.55<np<1.90 is satisfied (provided that (np) denotes the refractive index at a line (d) of the prism block).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finder and a camera, and more particularly to an inverted Galilean finder having an objective lens and an eyepiece, and a camera incorporating the finder.

[0002]

2. Description of the Related Art As described above, an inverted Galilean finder optical system having an objective lens and an eyepiece, and a first optical path and another second optical path of the finder optical system are overlapped with each other. In the optical path between the objective lens and the eyepiece of the finder optical system, a half mirror joining surface obliquely provided for overlapping another second optical path on the first optical path of the finder optical system is provided inside. There is known a finder that includes a prism block having the second optical path and the first optical path by the half mirror joining surface.

For example, Japanese Patent Application Laid-Open No.
No. 125716 is disclosed. In the configuration of the inverted Galilean finder optical system, a prism block in which a half mirror is obliquely provided between an objective lens and an eyepiece is used, and the material of the prism block is a so-called BK7.
Those with a fairly low refractive index are used.

[0004] (Prior art 2) an inverted Galilean finder optical system having an objective lens and an eyepiece;
In the optical path between the objective lens and the eyepiece of the finder optical system, a half-mirror joining surface obliquely provided to overlap the visual field frame optical system is provided as if the visual field frame optical system were superimposed on each other. A finder is known which comprises a prism block and overlaps the optical path of the field frame optical system with the optical path of the finder optical system by the half mirror joining surface. Further, there is known a finder having a lighting mirror member that illuminates a field frame that determines an imaging range by collecting external light and reflecting the external light on the reflection surface.

[0005]

However, as a (problem of the prior art 1), in an inverted Galilean type finder having a configuration in which a prism block having a half mirror is arranged between an objective lens and an eyepiece, a prism block is provided. If a glass material having a low refractive index is used, the length in terms of air cannot be reduced so much that the finder magnification cannot be increased. Also, there is a problem that the brightness of the finder becomes uneven due to the difference in the incident light in the left-right direction from the object due to the oblique angle of the half mirror bonding surface.

[0006] Another problem (problem of prior art 2) is that a large space is required for disposing the light-collecting mirror member, and the camera tends to be large.

One of the objects of the present invention is to provide a finder having a long eye point (EP), a wide angle of view, and a high magnification, without unevenness in brightness due to total reflection or the like at a joint surface of a half mirror. Is to do.

[0008] One of the objects of the present invention, in addition to the above objects, is to provide:
Another object of the present invention is to provide a compact viewfinder having a distance measuring optical system and an inverted Galileo type viewfinder.

It is an object of the present invention to provide a finder which effectively illuminates a field frame in a small space and has less unevenness in the brightness of the field frame.

An object of the present invention is to provide a camera in which the finder is compactly incorporated in a camera body.

[0011]

The above object is achieved by any of the following means.

(1) An inverted Galilean finder optical system having an objective lens and an eyepiece lens, and a first finder optical system in the optical path between the objective lens and the eyepiece lens of the finder optical system. And a prism block provided with a half-mirror bonding surface provided obliquely so as to overlap another second optical path on the optical path of (1), wherein the following condition is satisfied.

1.55 <n _p <1.90 (1) where n _p is the refractive index of the prism block at d-line. (2) The second optical path is measured. The finder according to (1), which is an optical path of a distance optical system, and obtains a distance measurement image by overlapping the first optical path by the half mirror joining surface.

(3) The finder according to (1) or (2), wherein the following conditions are satisfied.

48 ° <θ _p <60 ° Expression [2] where θ _{p is} the optical axis of the inverted Galilean finder and the normal to the half mirror joining surface of the prism block. Corner

(4) The optical path between the objective lens and the eyepiece of the finder optical system is such that an inverted Galilean finder optical system having an objective lens and an eyepiece and a field frame optical system overlap each other. A prism block having a half-mirror joining surface provided obliquely provided therein, wherein the optical path of the field-of-view frame optical system is overlapped with the optical path of the finder optical system by the half-mirror joining surface. The frame optical system has a lighting mirror member that illuminates a visual field frame that determines an imaging range by collecting external light and reflecting the light on a reflecting surface, and that the reflecting surface is divided into four or more in the horizontal direction. A finder to be characterized.

(5) The finder according to (4), wherein the following condition is satisfied.

0.1 ≦ p ≦ 3.0 (3) where p is the horizontal pitch (unit: mm) of the divided reflecting surface of the lighting mirror member. (6) A camera comprising the finder according to any one of (1) to (5).

Here, each item will be described. According to the invention described in (1), the conditional expression [1] defines the refractive index suitable for the material of the prism block having the half mirror provided between the objective lens and the eyepiece of the inverted Galileo finder. It is. The prism block has the effect of shortening the air-equivalent length as the refractive index is higher, which is equivalent to providing parallel plane glass. Below the lower limit, the cost of glass material is low, but the effect of shortening the air equivalent length is small,
Compactness and high magnification become insufficient. Conversely, if the upper limit is exceeded, miniaturization can be achieved. However, in addition to the high cost of the glass material, many glass materials whose transmittance of short-wavelength light deteriorates are not preferable because they may appear yellowish.

According to the invention described in (2), the above (1)
In addition to the above effect, the inverted Galileo finder and the distance measuring optical system can be observed simultaneously by the prism block having the half mirror.

According to the invention described in (3), the conditional expression [2] has a half mirror joining surface provided between the negative refractive index objective lens and the positive refractive index eyepiece of the inverted Galilean finder. In the prism block, an appropriate angle is set when the half mirror joining surface is set obliquely with respect to the optical axis of the inverted Galileo finder. If the upper limit is exceeded, the angle of incidence with respect to the half mirror bonding surface increases, so that total reflection easily occurs, flare tends to occur, and
The entrance surface of the prism block on the objective lens side becomes narrow, and a sufficient angle of view cannot be obtained. Conversely, if the lower limit is exceeded, total reflection will not occur. Become.

Further, the lower the refractive index of the adhesive used for the half mirror joint surface, the greater the difference from the refractive index of the prism block, the easier the total reflection, and the greater the angle of incidence on the half mirror joint surface, Brightness unevenness occurs on the left and right of the visual field image.

More specifically, referring to FIG. 3, in the finder, the refractive index of the prism block P1 is larger than that of a general adhesive. Therefore, the right principal ray S
When the incident angle θ1 with respect to the half mirror bonding surface HM is larger than the incidence angle θ2 with respect to the half mirror bonding surface HM than the left principal ray S1, the transmittance of the right principal ray S2 is smaller than that of the left principal ray S1. The difference between the transmittances of the right and left rays causes uneven brightness. When the incident angle is extremely large, total reflection may occur.

According to the invention described in (4), the number of divided reflecting surfaces of the lighting mirror member is preferably four or more in the horizontal direction, and when it is less than this, unevenness in brightness of the visual field frame tends to be conspicuous. .

According to the invention described in (5), the conditional expression [3] defines the condition under which the unevenness of the brightness of the visual field frame hardly occurs and the condition of the workability. If the upper limit is exceeded, the brightness of the field frame becomes uneven. Conversely, if the lower limit is exceeded, when the lighting mirror is formed of a plastic material, the pitch of the reflecting surface is too fine, and the ridges of the reflecting surface are worn by the mold, and the brightness tends to decrease.

According to the invention described in (6), a camera incorporating a finder having the above effects is provided. Further, the finder can be compactly incorporated in the camera body, and the camera becomes compact.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A viewfinder and a camera according to an embodiment of the present invention will be described with reference to the drawings. FIG.
Is an entire finder optical system according to the present invention. FIG. 2 shows another view frame optical system.

As shown in FIG. 1, the finder according to the embodiment has a field optical system, a distance measuring optical system, and a field frame optical system of an inverted Galilean type finder, but is not limited thereto.

1) The inverted Galilean finder (field optical system) will be described.

An inverted Galilean finder is constituted by an objective lens L1 having a negative refractive power and an eyepiece L2 having a positive refractive power. Further, the objective lens L of the finder optical system described above.
In the optical path between 1 and the eyepiece L2, there is a prism block P1 having a half-mirror joining surface HM obliquely provided to overlap another optical path inside.

When the prism block P1 is joined to the prism block P1a and the lens prism block P1b, the prism block P1 functions as a parallel plane glass for the inverted Galilean finder. The joining portion between the prism block P1a and the lens prism block P1b is a half-mirror joining surface HM, which allows the light flux of the inverted Galilean finder to pass therethrough, and the distance measuring optical system and the field frame optical system described later reflect, These light beams are superimposed and work as a composite image to the eye point. Further, by using a glass material having a high refractive index as the material of the prism block P1a and the lens prism block P1b, the air conversion length is further shortened and the finder magnification is increased.

Next, the eyepiece L2 is a part of an eyepiece of a distance measuring optical system and a field frame optical system, which will be described later, as well as an eyepiece of an inverted Galilean finder. Note that the cover glass CG1 protects the objective lens L1.

2) The viewfinder of the distance measuring optical system will be described.

In this distance measuring optical system, external light from an object is made incident through a cover glass CG2, and a right and left inverted erect image of the object is formed by a roof prism P2. For this purpose, it passes through a distance measuring objective L4 moving between infinity and a close distance, and further,
A double image matching type ranging image is formed on the field frame f1 having the ranging window by the ranging objective lens L4. Further, the half mirror connecting surface HM obliquely provided in the optical path of the inverted Galileo finder and the eyepiece L2 constitute an optical system for obtaining a right and left normal erect virtual image as a ranging image from a real image.

The half mirror joining surface HM inside the prism block P1 is set obliquely within an appropriate angle range with respect to the optical axis F1 of the inverted Galilean finder. This suppresses uneven brightness due to total reflection and the like.

3) The viewfinder of the field frame optical system will be described.

External light from the front of the camera is a light window FP
to go into. The lighting window FP has a large number of vertically elongated prisms formed on a substrate, and external light is collected by a mirror M1.
To guide you efficiently. Further, after being reflected by the lighting mirror M1, the field frame f1 is irradiated. The lighting mirror M1 has a vertically elongated reflecting surface M1b, and a large number of reflecting surfaces M1b are formed on one substrate. Each reflecting surface M1b faces the front of the camera. Note that the lighting mirror M1 is provided with an opening M1a for allowing the light beam F2 for distance measurement to pass through.

The field frame f1 is provided with a mechanism that moves between infinity and a close distance for automatic parallax correction in conjunction with focusing of the photographing lens.

Any one of the frames for each focus lens automatically appears in conjunction with the replacement of the lens. When one frame comes out, the other frames disappear.
Note that the small lighting prism P3 is a prism for mainly increasing the brightness of the field frame of the telephoto lens.

The light from the field frame f1 passes through the condenser lens L3, and then passes through the half mirror joining surface HM obliquely provided in the optical path of the inverted Galileo finder and the eyepiece L2 of the inverted Galileo finder. The optical system obtains a virtual image of the frame f1.

As described above, even if the distance between the distance measuring objective lens L4 and the field frame f1 is narrow, the field frame f can be effectively used.
1 can be lit without uneven brightness.

Here, another view frame optical system will be described with reference to FIG. As shown in FIG. 2, external light from the front of the camera has a large number of vertically elongated prisms formed on a substrate in a light taking window FP, and guides the external light to the lighting mirror M2. Further, the light reflected by the lighting mirror M2 is guided to the lighting prism P4, and further condensed to irradiate the field frame f2. The daylighting mirror M2 has a large number of vertically elongated reflecting surfaces M2b formed on one substrate.
Each reflection surface M2b faces the front of the camera rather than the substrate. The lighting mirror M2 is provided with an opening M2a for passing the optical axis F2 for distance measurement.

The daylighting prism P4 is a prism having a light condensing property at a peripheral portion P4b and a diverging property at a central portion P4c, and is disposed near the field frame f2. Note that a transparent portion P4a for passing the optical axis F2 of the distance measuring system is provided at the center.

The field frame f2 is provided with a mechanism which moves between infinity and a close distance for automatic parallax correction in conjunction with focusing of the photographing lens. Any one of the frames for each focus lens automatically appears in conjunction with the replacement of the lens. As shown in FIG. 1, after passing through the condenser lens L3, the half mirror joining surface HM obliquely provided in the optical path of the inverted Galileo finder.
And the eyepiece L2 of the inverted Galileo finder,
The optical system obtains a virtual image of the visual field frame. In addition,
Principal rays S3 and S4 indicate the light rays at the extreme end of the daylighting.

As described above, even when the distance between the distance measuring objective lens L4 (FIG. 1) and the field frame f2 is small, the field frame f2 can be illuminated without unevenness in brightness.

Next, the camera of the present invention is a camera incorporating the above finder. ADVANTAGE OF THE INVENTION According to the camera of this invention, the unevenness | luminance of brightness | luminance by the total reflection etc. at a half mirror joint surface does not generate | occur | produce, a long eye point (EP), a camera provided with a high angle of view and a high magnification finder Becomes In addition, since a small finder is incorporated, it becomes a small camera.

[0047]

Examples of the present invention will be described below. Here, the symbols used in each embodiment are as follows.

F: focal length f _B : back focus r: radius of curvature of refraction surface d: interval between refraction surfaces ω: angle of view n _d : refractive index of lens material at d-line ν _d : Abbe number of lens material H : Pupil radius (mm) D: diopter (diopter) (Example 1) FIG. 4 shows an optical cross-sectional view (a) of a visual field system and an optical cross-sectional view (b) of a distance measuring system in Example 1. Also. Table 1 shows the lens data.

[0049]

[Table 1]

FIG. 5 shows an aberration diagram (a) of the visual field system and an aberration diagram (b) of the distance measuring system according to the first embodiment. Aberration is well corrected.

(Embodiment 2) FIG. 6 shows an optical cross-sectional view (a) of a visual field system and an optical cross-sectional view (b) of a distance measuring system according to a second embodiment. Also. The lens data is shown in "Table 2".

[0052]

[Table 2]

FIG. 7 shows an aberration diagram (a) of the visual field system and an aberration diagram (b) of the distance measurement system according to the second embodiment. Aberration is well corrected.

The values of the conditional expressions in each embodiment are shown in Table 3.

[0055]

[Table 3]

As shown in Table 3, each conditional expression is satisfied.

[0057]

According to the structure described above, the following effects can be obtained. There is no unevenness in brightness due to total reflection or the like at the joint surface of the half mirror, and the eye point (E.
P. ) Is long and has a high angle of view and high magnification.
In addition to the above effects, a compact finder having a distance measuring optical system and an inverted Galileo type finder, having a large effective base line length, is obtained. In addition, the viewfinder has less unevenness in brightness of the visual field frame and is easy to see. further,
The camera has a viewfinder built into the camera body.

[Brief description of the drawings]

FIG. 1 is an overall viewfinder optical system according to the present invention.

FIG. 2 is another view frame optical system.

FIG. 3 is a diagram for explaining unevenness in brightness of a visual field image.

FIG. 4A is an optical cross-sectional view of a visual field system according to a first embodiment, and FIG.

FIGS. 5A and 5B are an aberration diagram (a) of the visual field system and an aberration diagram (b) of the distance measurement system according to the first embodiment.

6A is an optical sectional view of a visual field system according to a second embodiment, and FIG. 6B is an optical sectional view of a distance measuring system.

7A and 7B are an aberration diagram of a visual field system and an aberration diagram of a distance measurement system according to a second embodiment.

[Explanation of symbols]

 P pitch f1, f2 Field of view frame M1, M2 Lighting mirror M1b, M2b Reflecting surface P3 Lighting small prism L1 Objective lens L2 Eyepiece L3 Condenser lens L4 Distance measuring objective lens P1 Prism block P. Eye point P4 Daylight prism HM Half mirror joint surface

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H018 AA04 BA06 BC05 2H087 KA14 PA02 PA04 PA17 PA18 PB02 PB05 QA02 QA07 QA14 QA17 QA21 QA22 QA25 QA32 QA41 QA42 QA45 RA41 RA42 TA04 9A001 KK16 KZ42

Claims (6)

[Claims] An inverted Galilean finder optical system having an objective lens and an eyepiece; and a first finder optical system in an optical path between the objective lens and the eyepiece of the finder optical system. A finder, comprising: a prism block provided with a half-mirror bonding surface provided obliquely so as to overlap another second optical path on the optical path, wherein the following condition is satisfied. 1.55 <n _p <1.90 where n _p is the refractive index of the prism block at d-line 2. The distance measuring image according to claim 1, wherein the second optical path is an optical path of a distance measuring optical system, and the half mirror joining surface obtains a distance measuring image superimposed on the first optical path. Viewfinder. 3. The finder according to claim 1, wherein the following conditions are satisfied. 48 ° <θ _p <60 ° where θ _p is the angle between the optical axis of the inverted Galileo finder and the normal line of the half mirror joining surface of the prism block. 4. An optical path between the objective lens and the eyepiece of the finder optical system, such that an inverted Galilean finder optical system having an objective lens and an eyepiece and a field frame optical system overlap each other. A prism block having a half-mirror joining surface obliquely provided therein, wherein the optical path of the field-of-view frame optical system is overlapped with the optical path of the viewfinder optical system by the half-mirror joining surface. The optical system has a lighting mirror member that illuminates a field frame that determines an imaging range by collecting external light and reflecting the light on a reflecting surface, wherein the reflecting surface is divided into four or more in a horizontal direction. The finder. 5. The finder according to claim 4, wherein the following condition is satisfied. 0.1 ≦ p ≦ 3.0 where p is the horizontal pitch (unit: mm) of the divided reflecting surfaces of the lighting mirror member. 6. A camera comprising the finder according to claim 1. Description: