JPS6153622A - Photometric device of single-lens reflex camera - Google Patents

Abstract

PURPOSE:To adjust a photmetric characteristic of a photometric element by constituting a titled device so that a reflected light quantity is varied successively along the prescribed direction on the light semi-transmitting surface, for instance, constituting said device of many reflecting areas by which the area is varied successively, and varying the area of the reflecting area. CONSTITUTION:A semi-tramsmitting part 9 is provided on one of an emitting surface S3 of the first prism 5 or an incident surface S4 of the second prism 6, and a part of a liminous flux reflected totally by the second reflecting surface S1' of the first prism is reflected in the direction of the second reflecting surface S1'. It is emitted from said part and led to a photodetector 10 provided in the vicinity of the second reflecting surface S1', and a photometry is executed. In order to eliminate an interference of the photodetector 10 and a focusing screen 4, the semi-transmitting part 9 is divided into rectangular reflecting areas extended in the horizontal direction and having each different area, so that the area becomes smaller toward the reflecting area being near the second reflecting area S1'. In this way, the reflected light quantity of the lower side part decreases gradually, a dense distribution of a light of lower part from the center of a picture is reduced, and the effect correspnding to a center priority average photometry can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus suitable for a nine-electron camera using an Fi solid-state photographing element.

Single-lens reflex cameras that use silver halide film have achieved great development because they have the optimal structure for image development. A typical optical system is to split the optical path of the image capture lens using a quick return mirror to create a finder optical path, and guide the split optical path to a penta roof prism to change the direction of the optical path and completely invert the left and right sides of the double-sided moonlight. This is for guiding the eyepiece to the eyepiece.

A photometry device for measuring the light beam passing through the friz@lens and performing so-called °I'TL side light is often placed on the bottom surface or exit surface of the pentagonal roof prism.

However, in the viewfinder optical systems of so-called electronic cameras using recent imaging bodies such as COD, the above-mentioned finder optical systems are no longer desirable in terms of optical performance and configuration.90 This is mainly due to the following reasons. Due to reasons.

(b) For example, the effective screen of a 215-inch image pickup body has a diagonal length ratio of 174, which is smaller than that of a 55-inch film. It's difficult.

(b) A space must be provided at the rear of the image pickup body for arranging the electrical processing circuit, which increases the distance from the image plane of the photographic lens to the rearmost end of the camera. For this reason, the observation pupil position of the finder optical system must be extended to the rear of the camera side, and such a configuration is difficult to maintain optical performance. , 11Although (a) and (b) mentioned above are particularly important in terms of optical performance,
This will be discussed in terms of visual field magnification. In general, the larger the field of view magnification is, the easier it is to use RyeI2 as a finder optical system, so it is better. The field of view magnification γ is the focal length of the mark I of the photographic lens as fOs.If the focal length of the eyepiece lens is fe, then the field of view is represented by r=, r:, -.To increase the sound rate r, It is necessary to reduce the focal length #fθ. The eyepiece is a finder optical system connection 9
Since the front focal point is placed in the fixed vicinity, in order to achieve a high magnification of field of view r, it is necessary to obtain a so-called erect normal image from the focusing screen of the finder optical system to the eyepiece lens. There are eight factors that reduce the path length of the optical system as much as possible. Assuming that the focal length fo of the photographic lens is fO = 12.5 mm, which is equivalent to a standard lens for a 2/3-inch image pickup body, and the field magnification r is 0.6, the focal length fe of the eyepiece lens is 20, F
Therefore, in order to obtain a field magnification of γ = 0.6 or more using a penta roof prism and a conventional finder optical system, the optical path length from the focusing screen to the eye opening lens must be approximately 20.8 rym, which is equal to the focal length of the eyepiece lens. must be done. This means that the eyepiece must be placed as close as possible to the exit surface of the pentagonal roof prism, and due to the condition mentioned above, the Ill'll for clear observation must be placed from the rear end of the camera. It is difficult to laugh at this because it conflicts with Jin who wants to set it at the back.

This patent was first published in Tokubon Sho 59-126825, which is a finder optical system that aims to increase the field of view magnification of the finder and sets the pupil for focusing at the rear of the camera's end. It also describes a device that guides a portion of the finder light flux to a photometric element. However, since the finder optical system itself is a 4A structure that meets the requirements of a non-trivial system, there is not enough room to satisfy other school requirements, making it difficult to freely select the Oki 1-element characteristic. There is.

(Objective) The object of the present invention is to provide a device for branching the optical path of the viewfinder optical system of an optical reflex camera and guiding the light to a photometric element;
The photometric characteristics can be made into the desired shape (1).

The purpose is to expand the field of view magnification and move the 11 lenses 8 to the rear of the camera body to branch the optical path of the viewfinder and achieve photometry regardless of the problems with the photometering element. The characteristics were changed to center-weighted average photometry.

In order to achieve the above objects, the present invention includes a photographic lens that forms a subject image on a projection body, and a finder that includes a prism that is optically coupled to the photographic lens and that guides the object by internal reflection during a return look. , a light semi-transmissive surface that branches the optical path in the prism, and a photometric element that receives the light beam passing through the branched light P3. The element's 1tllll'jt, %sexual complete tone, is a waste.

The embodiment to be described later is located on the original axis of the photographing lens, and is provided with a reflective film that divides the photographing path and the viewfinder optical path, and has an incident surface for vertically injecting the reflected light from the reflection angle. The incident element from S1 and the incident surface S1 is
A first reflecting surface S for deflecting so as to be reflected at the same surface (second reflecting surface B1') as the incident surface S1, and a second reflecting surface S'tf for emitting the reflected light t. 281 prism having an exit surface S, and an entrance surface S4 for making the multiplication table incident from the exit surface Ss of the brush 1 prism, and a Tri:J (M 5 reflection surface S) which is the same as the entrance surface S4.
A roof surface having two reflective surfaces (fifth reflective surface 8, fourth reflective surface S') for reversing the left and right images and reflecting the image again at (-); 5. A second prism having an exit surface S6 for exiting the source reflected by the reflecting surface S-?A t-th finder optical system for observing an object ρ having an exit surface S8 of the first prism, or A light semi-transmissive surface is provided on the incident surface S4 of the second prism, and a part of the light reflected by the second reflective surface S1' of the first prism is reflected in the direction of the second anti-reflective surface 1'. The semi-transmissive part is composed of a large number of reflective regions having different areas,
The surface cost of each reflective area is made smaller as it approaches the second reflective surface B,/.

(Example) The present invention will be described in detail below with reference to FIG. Heishin,
1#-j Wait for the function to form an image of the subject with the photographing lens. 2 is a quick return mirror and has a 1r bow that guides light to the viewfinder. The mirror 2 may be a semi-transparent mirror. 5 is the imaging plane of the solid body image Nanko. Reference numeral 4 denotes a focusing screen, which has, for example, a split prism in the center and a matte surface around the periphery. The light beam is reflected by the mirror 2 and forms an image on or near the focusing screen 4.

5 and 6 are combination prisms that change the direction of the optical path, together determine the positional relationship between the optical axis of the photographing lens 10 and the optical axis of the eyepiece lens 7, and have the function of reversing the left and right sides of both sides.
, the 5-digit first prism has a triangular shape, and the surface indicated by m corresponds to the cross section. The first reflecting surface Bl, which has been subjected to the trowel surface treatment, has a total reflection or specular reflection, and the second reflecting surface S, which is an extension of the incident surface Sl, , is the exit surface. 6 is the second prism, S is the incident surface, and S
II'S5' is the first reflective surface (〒), which is a mirror-treated roof surface. Reference numeral 13i is a second rear surface that is completely opposite or mirror-reflective, and is a surface that is longer than the entrance surface S4. S6 is the exit surface. Furthermore, the light emitted from the focusing screen 4 is perpendicularly incident on the incident surface S of the flute 1 prism 50, reflected by the yellow phosphorus A1 reflective surface S of the reflective film, and then reflected at the second reflection surface, which is the same surface as the incident surface S1. The sound is totally reflected or specularly reflected by the surfaces S and ′, and is emitted from the first prism 5 through the exit surface S. After that, the original beam enters from the entrance surface S4 of the second beam 6, is reflected by the roof surface consisting of the two third reflection surfaces S3 and the fourth reflection @S,' on which the reflection film is deposited, and is further reflected by the incident surface 1nn.
The temporary seal S reflected on the fifth reflecting surface S, which is the same surface as s.
, ejects more nearly vertically. The light beam emitted from the exit surface S6 passes through the eyepiece lens 7 and reaches observation R:18. Incidentally, the r, z1 prism 5' and the broom 2 prism 6 may be attached to each other, or they may be arranged as one with a slight gap between them.

Next, a method for performing photometry at the groove bottom will be explained in detail.

In the figure, the exit surface of the first prism is "S" or "91".
A semi-transparent part 9 is provided on either of the entrance surfaces S4 of the x2 prism, and the a'! A part of the luminous flux totally reflected by the second reflecting surface S1 of the first prism is reflected in the direction of the second reflecting surface B1' and emitted from the second reflecting surface B1', and a light receiving element disposed near the second reflecting surface S1 is provided. 10 and measure the light. However, since the light receiving element 10 and the focusing screen 4 are placed close to each other, if consideration is given to eliminating mechanical interference between the holding members, the position of the light receiving element cannot be moved very close to the focusing screen. The problem caused by this will be explained with reference to FIG. 2. The center of the light receiving element 10 is located closer to the eyepiece, and the photometric sensitivity distribution on the focusing screen becomes biased. At the same time, for convenience, it shows how the tS emitted from the center point of the light receiving element in various directions is distributed on the focusing screen 4.
From this, the jllll light sensitivity distribution becomes lower-weighted average photometry, which shows a dense distribution below the center of the screen. This is shown in FIG.

With the nine different photometric sensitivity distributions shown in the same figure, it can be seen that in a typical bust shot scene of a person, the person's face is slightly above the center of the screen, so if the person is wearing black clothes, the person's face will be The part will be extremely over-exposed, and if you are wearing white clothes, it will be under-exposed, making it difficult to get the maximum exposure.

To deal with this situation, the semi-transparent section 9 in Fig. 1 is divided into rectangular reflecting areas extending horizontally and having different areas as shown in Fig. The area of the reflection area is made small. This configuration allows lower (u1
The amount of reflected light in the area gradually decreases, and the dense distribution of rays in the i direction can be reduced by one point below the center of the screen on the photometric sensitivity distribution, so it can provide an effect equivalent to center-weighted average side light. It is. In Fig. 4, the reflective area changes in the vertical direction; however, depending on the application, it is also possible to divide the area with equal pitch or variable pitch in the left and right directions. It may be used on the bottom, or it may be replaced with a semi-transparent reflective film deposited so that the reflection value gradually changes.

Note that the surface-precision divided reflection area itself may be a semi-transmissive mirror or a total reflection mirror.

(Effects) Since the present invention can transform the photometric distribution into a desired shape, the prism in the finder can be adapted to the scanning system and the arrangement of the camera itself, so that the photometric distribution can be adjusted to the initial purpose. Even if it differs from the above, it has the effect of allowing you to adjust it freely.

A further advantageous effect of the present invention is that less color is received by the eyepiece (measured with respect to the incident light y0). As a means to prevent this, an eyepiece shutter placed near the eyepiece lens or the like is used to solve photometry errors due to the incoming light. 90 In the photometry method according to the present invention, most of the reverse incident light incident from the eyepiece side is determined to be a light grating that travels backward through the normal optical path of the finder element system, and the light flux incident from the incident surface S3 of the first prism is , the light is totally reflected by the second reflecting surface S1' and does not reach the light receiving sensor 10, so there is an advantage that no exposure error occurs.

4 Brief explanation of further aspects The first factor is an optical cross-sectional diagram showing an embodiment of the present invention, FIG. FIG. 4 is a perspective view showing a semi-transparent part according to an embodiment.

In the diagram 1 is the photographic lens 2 is quick return mirror 4 is focusing screen 5 is the first prism 6J-1 2nd prism 7 is the eyepiece 9 is a half-sided part 10 is receiving) °e element It is.

Claims (3)

[Claims] (1) A photographic lens that forms a subject image on an imaging body, a finder that is optically coupled to the photographic lens and includes a prism that guides light through multiple internal reflections, and an optical half that branches the optical path in the prism. It has a transmitting surface and a photometric element that receives a light beam passing through a branched optical path, and the side light characteristic of the photometric element is adjusted by configuring the semi-transparent surface to change the amount of reflected light along a predetermined direction. A photometric device for single-lens reflex cameras featuring: (2) A photometric device for a single-lens reflex camera according to claim 1, wherein the semi-transparent surface has a reflective area whose area changes in sequence. (3) A reflecting mirror is used to optically couple the finder to the photographing lens, and the prism has an entrance surface S_ for vertically entering the reflected light from the reflecting mirror.
1, and the light incident from the incident surface S_1 is transmitted to the incident surface S_1.
A first reflective surface S_2 for deflecting the light so that it is totally reflected on the same surface as _1 (second reflective surface S_1'), and an exit surface S_2 for emitting the light totally reflected on the second reflective surface S_1'.
3, an entrance surface S_4 for allowing the light emitted from the exit surface S_3 of the first prism to enter, and a surface that is the same as the entrance surface S_4 (fifth reflective surface S_4').
a roof surface having two reflective surfaces (fifth reflective surface S_5, fourth reflective surface S_5') for deflecting the surface so as to be reflected again at the center and inverting the left and right images; and the fifth reflective surface S_4'.
The second prism has an exit surface S_6 for exiting the light reflected by the light beam, and the light semi-transparent surface is the exit surface S_3 of the first prism or the entrance surface S_6 of the second prism.
The second reflective surface S_1' of the first prism is located on the
A part of the light reflected by the light is reflected in the direction of the second reflective surface S_1', and furthermore, the area of the reflective area forming the light semi-transparent surface becomes smaller as it approaches the second reflective surface. A photometric device for a single-lens reflex camera according to claims 1 and 2.