JP2503439B2 - Photometric device - Google Patents

Description

The present invention relates to a photometric device for performing photometry for focus detection and exposure control in a single-lens reflex camera or the like.

B. Conventional technology A single-lens reflex camera configured to perform both focus detection for automatic focus adjustment and photometry for automatic exposure control by using part of the subject light that has passed through a shooting lens, etc. Are known.

Various types of photometric devices for this type of camera have been developed. For example, as a photometric device for performing photometric measurement using an optical system for focus detection, the one described in JP-A-57-169734. There is.

This photometric device is provided with a beam splitter using a random dot mirror or stripe mirror in a part of the focus detection optical system, and a part of the light for focus detection is received by this beam splitter It is configured so that it can be sent to and metered.

C. Problems to be Solved by the Invention However, in the conventional photometric device as described above, the light for focus detection is divided by a random dot mirror or the like, so the amount of light for focus detection is reduced. There is a problem that the amount is small, and there is also a problem that the light cannot be sufficiently taken in for photometry.

The present invention has been proposed to solve such a problem, and an object thereof is to provide a photometric device capable of supplying a sufficient amount of light for both focus detection and photometry with a relatively simple configuration. To provide.

D. Means for Solving Problems The present invention will be described with reference to FIG. 1 and FIG. 2 for explaining an embodiment. According to the present invention, a part of the subject light transmitted through the objective lens 1 is used for focus detection and exposure. It has a wavefront splitting element 14 for splitting each split light for control into a light receiving means for focus detection 10 and a light receiving means for photometry 12, and a center portion of the wavefront splitting element 14 for guiding a focus detecting light beam. The area 14A is divided into two as a second area 14B that guides the exposure control light flux around the area 14A and both areas 1
4A and 14B are complementarily formed in the total transmission area or the total reflection area, and the wavefront splitting element 14 is arranged near the planned focal plane of the objective lens 1.

E. Action The subject light guided to the wavefront splitting element 14 is the first area 14A.
Are totally transmitted or totally reflected by the light-receiving means 10 for focus detection and are guided to the light-receiving means 12 for photometry in a complementary manner in the second area 14B around the light-receiving means 10.

F. Examples Hereinafter, the present invention will be described based on illustrated examples.

 1 to 3 show a first embodiment of the present invention.

As shown in FIG. 1, a single-lens reflex camera has a quick return mirror 3 having a half mirror partially or entirely disposed between a photographing lens 1 and a shutter 2, and an object which has passed through the photographing lens 1. Most of the light is reflected by the quick return mirror 3, passes through the focusing screen 4, the pentaprism 5, and the eyepiece 6, and is observed as a finder image. On the other hand, part of the subject light that has passed through the taking lens 1 passes through the quick return mirror 3 and is reflected by the sub-mirror 7.
The photometric device 8 according to the present invention arranged on the bottom of the camera body
Be led to.

Referring also to FIG. 2, this photometric device 8 has an infrared cut filter 9 for removing harmful infrared light on the front surface, and a focus detection device including a lens and a CCD as a focus detection light receiving means. A unit 10, a photometric light receiving element 12 having a condenser lens 11 on the front surface, and a subject light 13 for focus detection light flux 13A.
And a wavefront splitting element 14 for splitting the light flux for exposure control 13B. Since the wavefront division element 14 is configured to transmit the focus detection light beam 13A and reflect the exposure control light beam 13B, the focus detection unit 10 is arranged in the transmission direction and the photometric light receiving element 12 is arranged in the reflection direction. Set up.

Here, in FIG. 2, the subject light 13 is projected onto the planned focal plane 20.
Although the image is formed in the vicinity, normally, the information indicating the focus adjustment state is
A very narrow area 15 in the center of the shooting screen 15 in FIG.
Since it is obtained from A, the focus detection light beam 13A is
So that the luminous flux corresponds to.

Therefore, as shown in FIG. 3, the wavefront splitting element 14 is provided with a slit (first region) 14A capable of transmitting all the focus detecting light beam 13A at the center of the splitting surface. The slit 14A is obtained by providing a reflective film on the split surface (second region) 14B other than the slit 14A. Then, the exposure control light flux 13B is entirely reflected by the split surface 14B almost 100% and enters the photometric light receiving element 12. From the above, there is almost no loss of the focus detection light beam due to the provision of the wavefront splitting element.

In FIG. 4, the area indicated by 15A + 15B is the area taken in by the photometric device, the central area 15A is the area used for focus detection, and the remaining area 15B around it is the area used for photometry.

Here, the photometric region 15B is a region where the central elongated region 15A is omitted, but it is a small amount from the overall area (for example, the occupation ratio of the region 15A is 20%), and the light in the region 15B is almost lost. Since it is not used for photometry, it is possible to obtain a sufficient amount of light for photometry.

Further, since the subject to be photometered does not usually exist only in the central long and narrow area 15A, there is no practical problem even in the photometric area where the central long and narrow area is omitted.

Next, FIGS. 5 and 6 show a second embodiment of the present invention, in which the photometric device 28 includes the photometric light receiving element 12 in the transmission direction and the focus detection unit 10 in the reflection direction. It is arranged, and is selectively used from the first embodiment according to the space at the bottom of the camera body.

Except for the wavefront splitting element, it is the same as that of the first embodiment, and the wavefront splitting element 24 reflects all the focus detection light flux 13A to enter the focus detection unit 10 and transmits all the exposure control light flux 13B to perform photometry. The light receiving element 12 is configured to be incident.

Therefore, as in the first embodiment, a reflection film is provided at the center of the divided surface corresponding to the first area 25A, and the focus detection light beam 13A is provided.
Is set as a reflecting surface 24A that reflects almost 100%, and the other surface 24B does not have a reflecting film so that light is transmitted.

Also in such a wavefront splitting element 24, as in the case of the first embodiment, the provision of the wavefront splitting element causes almost no loss of the light flux for focus detection, and the light quantity for photometry is sufficient.

The areas 15A and 15B shown in FIG. 4 do not have to be in the center of the screen, and the area 15A need not occupy the center of the area 15B. For example, only one of the top and bottom of the first area 15A for focus detection can be used. A second area 15B for photometry may be provided in the.

As described above, according to the embodiment, since the luminous flux used for distance measurement is sufficient only in the central portion of the subject luminous flux 13, the luminous flux in the central portion is completely transmitted by the slit 14A. The light is guided to the focus detection unit 10, and the other part of the light flux is reflected by the split surface 14B to 100% and is guided to the photometric light receiving element 12. On the other hand, in the conventional technique, the subject light flux is transmitted to a semi-transmissive mirror or the like. 50% luminous flux to the light receiving element for distance measurement,
The other 50% of the luminous flux is guided to the light receiving element for photometry. Therefore, in the embodiment, the subject light 13 is effectively distributed to the focus detection unit 10 and the photometric light receiving element 12.
Sufficient detection is possible without loss of light quantity.

G. Effects of the Invention As described above, according to the present invention, a part of the subject light is divided by the wavefront splitting element for focus detection and photometry, and the wavefront splitting element is used for the planned focus of the objective lens. Since it is arranged near the surface, it is possible to supply a sufficient amount of light for both focus detection and photometry with a relatively simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a single-lens reflex camera provided with a first embodiment of a photometric device according to the present invention, and FIG. 2 is a photometric device of FIG. FIG. 3 is an enlarged view, FIG. 3 is a perspective view showing the wavefront splitting element of FIG. 2, FIG. 4 is a schematic view showing a first area for focus detection and a second area for photometry on the photographing screen, and FIG. FIG. 6 is a schematic view showing a single-lens reflex camera provided with a second embodiment of the photometric device according to the present invention.
It is an enlarged view of the photometric device of FIG. 8,28: Photometric device 10: Focus detection unit 12: Photometric light receiving element 13A: Focus detection luminous flux 13B: Exposure control luminous flux 14, 24: Wavefront splitting element 14A: First area 14B: Second area

Claims (1)

(57) [Claims] 1. A part of a subject light transmitted through an objective lens is split by a wavefront splitting element for focus detection and exposure control, and each split light is guided to a focus detection light receiving means and a photometry light receiving means. In a photometric device for performing photometry, a first part for guiding a focus detection light beam to the central part of the wavefront splitting element.
A region, and a second region around which a region for guiding the exposure control light beam is guided, and both regions are formed as complementary total transmission regions or total reflection regions, and the wavefront splitting element is provided near the planned focal plane of the objective lens. A photometric device characterized by being arranged.