JPH01155307A - Camera - Google Patents

Abstract

PURPOSE:To divide the exit pupil of a photographic lens with a simple constitution by arranging a condenser lens in the go-and-return optical path of the light of an object by a light reflecting member. CONSTITUTION:The light reflecting member 5a is provided on a part of the image-formation surface of a focusing plate 4 and the light beams reflected on the member 5a are made to be guided to a photodetector 12 for detecting a focus. And the condenser lens 6 is arranged in the go-and-return optical path by the optical reflecting member 5a. Thus, the division of the exit pupil of the photographic lens 2 is performed with a condenser lens 6, so that the focus detection in a reasonable TTL phase difference detection system can be accomplished. Since the condenser lens 6 can be used in common in a finder system and a focus detection system, the number of parts is reduced and the title camera becomes satisfactory in space and in cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a camera equipped with a focus detection device using a phase difference detection method.

(Background of the Invention) Conventionally, a slit member having a plurality of slit openings arranged at regular intervals is disposed near a planned imaging plane of an imaging lens or at a position on any plane thereof, and the slit member is The imaging lens is vibrated in a direction perpendicular to the optical axis (direction in which the slit openings are lined up), and the phase difference between two images of the object that are incident on a pair of light receiving element surfaces disposed at the subsequent stage is determined and focused. A so-called colphoto type focus detection device for detecting the focus state of an image lens is already known from Japanese Patent Publication No. 32846/1983.

Incidentally, the distance measurement area in this type of device is limited to the center of the screen of the observation field, that is, on the optical axis of the imaging lens. For this reason, there is no problem if the object to be focused is positioned at the center of the screen and the distance measurement operation is performed, but if the object is positioned other than the center of the screen and the operation is performed, it is difficult to accurately focus on the object. The drawback was that it was not possible. In view of this, the applicant of the present application filed a patent application in 1983 for a device that enables distance measurement at a desired position by moving the distance measurement area within the observation field.
-47245 etc.

However, when trying to incorporate the proposed device into, for example, a single-lens reflex camera, it is difficult to incorporate the proposed device into a single-lens reflex camera, in which the photographic lens, main movable mirror, sub-movable mirror, and bottom of the mirror box are used. When it comes to the optical path of the placed focus detection system, the movement range of the distance measurement area within the shooting screen is limited depending on the size of the sub-movable mirror or its position, and in reality it can only move within an extremely narrow range. , a problem arises in that the distance measurement area cannot be expanded.

In contrast, a light reflecting member is provided on a part of the image forming surface of the focusing plate, and the reflected light is guided to the focus detection system at the bottom of the mirror box for distance measurement, eliminating the need for the sub-movable mirror. On the same day, an application was filed for an embodiment camera that allows the distance measurement area to be moved or expanded within the screen.

However, in general, when performing focus detection using the phase difference detection method, it is necessary to divide the exit pupil of the photographing lens, and the applicant has developed a configuration that allows rational exit pupil division of the photographic lens in the above configuration. thinking.

(Object of the Invention) An object of the present invention is to provide a camera that can divide the exit pupil of a photographic lens with a simple configuration.

(Features of the Invention) In order to achieve the above object, the present invention disposes a condenser lens in the reciprocating optical path of the subject light by the light reflecting member,
Thus, the condenser lens is used not only as an optical system for a finder system, but also as an optical system for dividing the exit pupil of a photographic lens, which is essential for a focus detection device using a phase difference detection method. shall be.

(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 ☆≠← tray 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 Fig. 2) A vibration mechanism for moving the light reflecting member 5a in the directions of arrows X and Y in Fig. 2 through the pentaprism 8, an eyepiece lens 9, and the diaphragm 5. This is an operating member (shown only in FIG. 2) that enables the user to freely select the position of the light reflecting member 5a within the screen using the operating member 18.

10 is a light-shielding cover for removing harmful light, and 11 has two openings 11a and 11b as shown in FIG.
12 is a light-receiving element having two light-receiving sections 12a and 12b as shown in FIG. 4;
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 eight surfaces, 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 photographic 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 llb of the diaphragm 11 into the exit pupil 15 of the photographing 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 aperture 9b of the diaphragm 9 and reaches the light receiving portion 12 of the light receiving element 12.
incident on b. At this time, the light reflecting member 5a, which is set at the center position of the screen as shown in FIG. vibrating in the direction.

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 the output waveform when the light reflecting member 5a is vibrated in the six directions of arrows via the diaphragm 5.

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 0
For example, as shown in FIG. 9, a light reflecting member 5a is attached to the edge of the screen.
In other words, FIG. 11 shows the focus detection optical path when the distance measurement area is moved.

According to this embodiment, a light reflecting member 5a is provided on a part of the image forming surface of the focusing plate 4, and the light reflected there is guided to the light receiving element 12 for focus detection, and the light reflecting member 5a
Since the condenser lens 6 is disposed in the reciprocating optical path, the following effects can be obtained.

1) The exit pupil of the photographic lens 2 is divided into condenser lenses 6
Therefore, focus detection using a rational TTL phase difference detection method can be realized.

That is, since the condenser lens 6 can be shared by the finder system and the focus detection system, the number of parts can be reduced, which is advantageous in terms of space and cost.

2) When applied to a single-lens reflex camera as in this embodiment, a configuration that allows subject light to be guided to the light-receiving element 12 without requiring a sub-movable mirror, that is, a focusing plate 4 is provided.
Since the light is reflected by a surface and guided, it is possible to set the distance measurement area at any position within the photographic screen (in the embodiment, this is done by moving the light reflecting member 5a with the operating member 18). This makes it possible to adjust the focus for a wide range of subjects.

(Modified Example) In this embodiment, a light reflecting member 5a is arranged on the light incident surface 4a (image forming surface) of the focusing plate 4, and the light reflecting member 5a is movable two-dimensionally to measure distance within the screen. Although the position of the area can be set arbitrarily, the light entrance surface 4 of the focusing plate 4
A slit-shaped light reflecting member such as the light reflecting member 5a is formed by aluminum vapor deposition or the like on a, and a plurality of such focusing plates (
A similar effect can be obtained by providing a lens with light reflecting portions formed at different positions and replacing the focusing plate as necessary. The focusing plate can be replaced through the lens mount or by removing the pentaprism, as is well known in conventional single-lens reflex cameras.

Also, in this case, the focusing plate 4 is vibrated by the vibration mechanism 7.

Further, although this embodiment shows an example in which the present invention is applied to a single-lens reflex camera, it can be similarly applied to a twin-lens reflex camera.

(Effects of the Invention) As explained above, according to the present invention, a condenser lens is arranged in the reciprocating optical path of the subject light by the light reflecting member,
Therefore, the condenser lens can be used not only as an optical system for a finder system, but also as an optical system for dividing the exit pupil of a photographic lens, which is essential for a focus detection device using a phase difference detection method.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a single-lens reflex camera that is 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. 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. 2...Taking lens, 3...Half mirror 54...Focus plate, 5...Diaphragm,
5a...Light reflecting member, 6...Condenser lens, 8...Penta prism, 9...
...Eyepiece, 11...Aperture, 12 Light receiving element.

Claims (1)

[Claims] (1) A photographic lens, a focusing plate for checking the imaging state of the subject light that passes through the photographic lens and enters, and a focusing plate that is placed on the imaging plane of the focusing plate and that allows a part of the light to enter the imaging plane. A light reflecting member that reflects light; a diaphragm member that regulates the light beams that have passed through different areas of the exit pupil of a photographic lens out of the subject light reflected by the light reflecting member and incident thereon; and a diaphragm member that regulates the light flux that is incident through the diaphragm member. What is claimed is: 1. A camera comprising a photoelectric conversion means for photoelectrically converting the image to produce focus detection information, the camera characterized in that a condenser lens is disposed in a reciprocating optical path of subject light through the light reflecting member.