JPH01155326A - Finder device - Google Patents

Abstract

PURPOSE:To have the image-formation state of an object image formed by a photographic lens viewed in the same focusing state in every position of a focusing plate by making the shape of the image-formation surface of the focusing plate coincide with the curvature of the intended image-formation surface of the photographic lens by a condenser lens. CONSTITUTION:The shape of the image-formation surface of the focusing plate is made to coincide with the curvature of the intended image-formation surface of the photographic lens by the condenser lens. Namely, the reason why the light incident surface 4a is formed in a sphere on the focusing plate 4 is that the image-formation surface of the photographic lens 2 is caused to be curved by the condenser lens 6. And the light reflecting surface 4a of the focusing plate 4 which is an image observing surface is formed so that it coincides with said curved image surface and the image-formation state equivalent to that on a film surface can be made to be visible through an eye-piece lens 9. Thus, a finder device through which the image-formation state of the object image can be surely confirmed even in a part except the center of the focusing plate can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in a finder device having a condenser lens arranged in a camera.

(Background of the Invention) FIG. 14 is a cross-sectional view of a conventional single-lens reflex camera, in which subject light transmitted through a photographing lens 101 is bent by a movable mirror 102 and enters a focusing plate 103 as a subject image. The light is diffused and enters the condenser lens 104 arranged at the next stage. Here, it is divided into two parts, and the negative beam is reflected by a part of the half mirror,
The light is then totally reflected by the bottom surface of the condenser lens 104 and guided to the light receiving element 105. The other light beam passes through a portion of the half mirror, and is then guided to the eyepiece lens 107 via the pentaprism 106.

In a camera with such a configuration, if it becomes necessary to reduce the height dimension of the camera due to design reasons, etc., the condenser lens 104 can be placed in front of the focusing plate 103 to improve functionality. can be easily achieved without any problems. However, in this configuration, since the condenser lens 104 is located between the photographing lens 101 and the focusing plate 103, the subject image formed on the focusing plate 104 is curved, and only the central part of the screen is visible. A problem arises in that it is not possible to confirm the imaging state.

In addition, the applicant has formed a light reflecting surface on a part of the light incidence surface (imaging surface) of the focusing plate or a surface equivalent thereto, and the reflected light is transmitted to the focus detection system ( On the same day, an application was filed for a camera configured to detect distance measurement information (or photometry information) by guiding the light to the viewfinder system and the focus detection system. Since a condenser lens is disposed between the photographing lens and the focusing plate for reasons such as sharing it with the camera, there is the problem that the subject image on the focusing plate is curved, as described above.

(Object of the Invention) An object of the present invention is to provide a finder device that solves the above-mentioned problems and can reliably check the imaging state of a subject image even in a portion other than the center of the focusing plate. be.

(Features of the Invention) In order to achieve the above object, the present invention makes the shape of the image forming surface of the focusing plate match (including substantially matching) the curvature of the expected image forming surface of the photographing lens formed by the condenser lens. The present invention is characterized in that the imaging state of the subject image formed by the photographic lens can be viewed simultaneously at the position of the focusing plate and in the focused state.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a central sectional view of a single-lens reflex camera showing an embodiment of the present invention. In the figure, 1 is a camera body, 2 is a photographic lens, 3 is a movable mirror (half mirror) that has a transmission characteristic of transmitting 50% of the light amount and reflecting the remaining 50%, and 4 is a light entrance surface 4a that is spherical. A focusing plate 5 having a matte surface and a light exiting surface 4b serving as a Fresnel lens is disposed close to the light incident surface 4a of the focusing plate 4 as shown in FIG. 10
The diaphragm is a diaphragm made of a transparent plate having a spherical W±p shape similar to the light incident surface 4a and integrally having a slit-shaped light reflecting member 5a that reflects 0%.

6 is arranged in the reciprocating optical path by the light reflecting member 5a,
A condenser lens 7 used as one of the focus detection optical systems connects the light reflecting member 5a through the diaphragm 5 in the direction of arrow A.
(See Figure 2) A vibration mechanism for vibrating in the direction, 8 a pentaprism, 9 an eyepiece lens, 18 the light reflecting member 5a
This is an operating member (only shown in FIG. 2) that allows the light reflecting member 5a to be moved in the directions of arrows X and Y in FIG. can.

10 is a light shielding cover for removing harmful light; 11 is a diaphragm having two apertures 11a and llb as shown in FIG. 3; and 12
As shown in FIG. 4, a light-receiving element has two light-receiving parts 12a and 12b, and 13 is a holding member that holds the light-receiving element 12.

In the above configuration, 50% of the subject light transmitted through the photographic lens 2 is bent upward in FIG.
The object image is formed on the a-plane, that is, on the light incident surface 4a of the focusing plate 4.

Here, the reason why the light entrance surface 4a of the focusing plate 4 is made into a spherical shape is because the condenser lens 6
This is due to the fact that the image forming surface of 9
It is intended to be visually recognized through the .

Of the subject light incident on the light incident surface 4a of the focusing plate 4, the subject light that is not reflected by the light reflecting member 5a passes through the light exit surface 4b forming a Fresnel lens, and further passes through the pentaprism 8 and the eyepiece lens 9. After that, the image of the subject is subjected to observation. Further, the subject light reflected by the light reflecting member 5a passes through the condenser lens 6 again, passes through the movable mirror 3, and reaches each light receiving section 12a, 12b of the light receiving element 12 arranged at a position equivalent to the film surface. It is guided by the diaphragm 11 and converted here into an electrical signal.

Figure 5 shows the parts related to focus detection extracted from the above configuration and further expanded to show the round trip optical path part.
In the figure, 5a' is a virtual plane drawn by extending the reflection surface of the slit-shaped light reflection member 5a, 6' is the return path of the condenser lens 6, 14 is the entrance pupil of the photographing lens 2, and 15 is the exit pupil.

The object light enters the entrance pupil 14, exits from the exit pupil 15, and forms an image on the virtual plane 5a'. Further, the reciprocation of the condenser lens 6 (6') and the virtual surface 5a' project images of the apertures 11a and 11b of the diaphragm 11 into the exit pupil 15 of the photographic lens 2. This situation is shown in Figure 6, 16a
, 16b are images of the apertures 11a and llb of the diaphragm 11.

Due to this imaging relationship, the image passes through the image 16a and the focus plate 4
The subject light that is incident on the light incident surface 4a and reflected by the light reflecting member 5a passes through the aperture 11a of the diaphragm 11 and enters the light receiving portion 12a of the light receiving element 12. In addition, the subject light that has passed through the image 16b and been reflected by the light reflecting member 5a passes through the opening 11b of the calibration 11 and reaches the light receiving portion 1 of the light receiving element 12.
2b. At this time, the light reflecting member 5a is set at the center position of the screen as shown in FIG.
is vibrated in six directions shown by the arrows in FIGS. 2 and 5 by the action of the vibration mechanism 7 via the diaphragm 5.

Here, the principle of distance measurement will be briefly explained using FIG. A slit-shaped light reflecting member 5a is provided near the imaging plane of the photographic lens 2.
are arranged, and images 16a and 16b of the exit pupil of the photographing lens 2 are transmitted to the light receiving section 12 of the light receiving element 12 using the condenser lens 6.
a, 12b. Thereby, the light that has passed through the image 16b of the photographic lens 2 will be incident on the light receiving section 12b, and the light that has passed through the image 16a will be incident on the light receiving section 12a. For convenience of explanation, the subject here is a point light source, and FIG. 7 shows output waveforms when the light reflecting member 5a is vibrated in six directions indicated by arrows.

When in focus, both outputs have exactly the same phase, but when they are slightly out of focus, the outputs lose their sharpness and a phase difference occurs between the outputs of the light receiving sections 12a and 12b. In front focus, the output of the light receiving section 12a is
It is ahead of the output of b, and is reversed when the focus is rearward. In this way, by using the phase difference between the outputs of the light receiving section 12a and the light receiving section 12b that occur depending on the focus state, front focus and rear focus are detected, the moving direction of the photographing lens 2 is determined, and the photographing lens is moved to the in-focus position. This is an attempt to stop 2.

The above has described the case where the distance measurement area (slit-shaped light reflecting member 5a) is set at the center of the photographing screen, but the position of the light reflecting member 5a within the light incidence surface 4a of the focusing plate 4 (inside the screen) is As shown in FIGS. 8 to 10, the diaphragm 5
It is easy to set the distance using the operating member 18 via the , which makes it possible to measure the distance at any position.

For example, as shown in FIG. 9, a light reflecting member 5a is attached to the edge of the screen.
FIG. 11 shows the focus detection optical path when the distance measurement area is moved.

FIG. 12 shows another embodiment of the present invention corresponding to FIG. 14, and the same parts as in FIG. 14 are given the same reference numerals.

The difference from FIG. 14 is that, as shown in FIG. 13, the light entrance surface 51a of the focusing plate 51 is shaped to match the curvature of the expected image formation surface of the photographing lens 101 formed by the condenser lens 104. This makes it possible to check the imaging state of the subject image in the same state as in the center even in a portion other than the center of the focusing plate 51.

According to this embodiment, the shape of the light incident surface of the focusing plate matches the curvature of the expected imaging surface of the photographing lens formed by the condenser lens (
(approximately match), the following effects are achieved.

1) It is possible to check the imaging state of the subject image even in areas other than the center of the focus plate.

2) By making the shape of the condenser lens as described above, a phase difference detection method is used that makes it possible to obtain a wide range of subject information (distance information in the example) by using the reflected light from the focusing plate surface. A focus detection device becomes possible.

(Effects of the Invention) As explained above, according to the present invention, the shape of the image forming surface of the focusing plate is made to match the curvature of the expected image forming surface of the photographing lens formed by the condenser lens. Since the image formation state of the subject image can be seen in the same focus state at any position on the focus plate, it is possible to reliably check the image formation state of the subject image even in areas other than the center of the focus plate. It becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a single-lens reflex camera showing an embodiment of the present invention, Fig. 2 is a plan view of a diaphragm and focusing plate having the light reflecting member shown in Fig. 1, and Fig. 3 is a plane view of the aperture. 4 is a plan view of the light receiving element, FIG. 5 is a developed view showing the optical path of the focus detection system, FIG. 6 is a diagram showing the division of the exit pupil of the photographic lens, and FIG. 7 is a diagram showing the invention of the present invention. Figures 8 to 10 are diagrams explaining the distance measurement method adopted in the present invention, and Figures 8 to 10 are diagrams explaining how to switch the position of the distance measurement area in the screen, which is an embodiment of the present invention. FIG. 8 is a diagram showing the optical path of the focus detection system when the distance measurement area is set at the position as shown in FIG. FIG. 14, which is an enlarged view of the illustrated focus plate, is a sectional view of a conventional single-lens reflex camera. 2...Taking lens, 3...Half mirror 14...Focus plate, 5...Diaphragm,
5a...Light reflecting member, 6...Condenser lens, 8...Penta prism, 9...
...Eyepiece lens, 12 light-receiving elements, 51...Focusing plate, 101...Photographing lens, 104...
... Condenser lens, 106 ... Pentaprism, 107 ... Eyepiece. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] (1) A focusing plate disposed at a position equivalent to the planned focal plane of the photographing lens and allowing observation of the imaging state of the subject image, and a condenser lens disposed between the photographing lens and the focusing plate. 1. A finder device, characterized in that the shape of the image-forming surface of the focusing plate matches the curvature of the expected image-forming surface of the photographing lens formed by the condenser lens.