JPH0522920Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Technical Field" The present invention relates to a reflection mirror for a single-lens reflex camera, and in particular to a reflection mirror in which a vapor-deposited film is attached on a half mirror to increase the average reflectance from the center to the periphery. .

"Prior art and its problems" A single-lens reflex camera guides incident light from a photographic lens system to a viewfinder optical system using a reflecting mirror, but recent cameras use incident light as a distance measurement signal or an exposure signal. In this case, the center portion of the reflecting mirror is made into a half mirror. The light that has passed through the half mirror is further input to a focus detection device and an exposure control device via another total reflection mirror.

Conventionally, this reflective mirror has a reflective film deposited in a predetermined pattern on the half mirror to eliminate the strange feeling in the viewfinder field of view caused by the half mirror in the center and to improve the visibility of the finder. The reflectance is the smallest at the center and largest at the periphery. However, the conventional reflective film formation pattern involves applying a reflective film whose average reflectance changes in stages within multiple concentric areas set from the center, so the change in reflectance is not smooth. .

``Purpose of the invention'' The object of the invention is to obtain a reflecting mirror in which the change in reflectance is smoother and the viewfinder field of view is less strange.

"Summary of the invention" As a result of research on the pattern of the reflective film deposited on the half mirror, this invention was developed using a fan-shaped basic shape centered on the center of the half mirror to make changes in reflectance smoother. It was completed by discovering what could be done.

In other words, the present invention imagines a plurality of concentric annular regions centered on the center of the reflecting mirror, and within each of these plural annular regions, the center side is removed from the fan shape centered on the center. A plurality of truncated fan-shaped reflective film segments are formed, and the circumferential spacing between these reflective film segments is approximately constant, and the average reflectance of the outer annular region is equal to that of the inner annular region. It is characterized in that the number of reflective film segments in the annular region on the outer circumferential side is smaller than the number of reflective film segments in the annular region on the inner circumferential side so that the reflectance is higher than the average reflectance.

``Embodiments of the invention'' The invention will be described below with reference to illustrated embodiments. FIG. 3 is a conceptual diagram of a single-lens reflex camera using the reflecting mirror 11 of the present invention. Subject light passing through the photographing lens system 12 is reflected by the reflecting mirror 11 and enters the viewfinder optical system 14 including the pentaprism 13. A subject image is observed through the eyepiece system 15.
The optical axis O is the optical axis of the photographic lens system 12.

The center portion of the reflecting mirror 11 corresponding to the optical axis O is a half mirror portion 11a, and the subject light transmitted through the half mirror portion 11a enters the light receiving element 17 via the total reflection mirror 16. The light receiving element 17 is, for example, a light receiving element of a focus detection device, and detects the focus state of the photographic lens system 12. The reflection mirror 11 and the total reflection mirror 16 are
At the time of photographing, it is evacuated from the optical path by a well-known retraction mechanism.

The present invention provides a reflection mirror 1 used in this way.
The reflectance is increased as smoothly as possible from the center part (optical axis O part) to the peripheral part of the lens, and an example thereof is shown in FIG. In view of symmetry, FIG. 1 shows only 1/4 (90°) of the reflective mirror 11 of the present invention surrounded by a horizontal line passing through the optical axis O and a vertical line.

The entire reflecting mirror 11 is composed of a half mirror 21 with a transmittance of 50%, for example, and a reflective film (for example, A1 film) with a reflectance of 95% on a predetermined portion thereof.
A truncated fan-shaped reflective film segment 22 is deposited. In the figure, the shaded areas are reflective films, and the gist of the present invention is these formation patterns.

In this example, centering on the optical axis O,
A central circular area A, two annular areas B and C,
An outermost area D is set outside the area. The central circular area A is a truncated fan-shaped reflective film segment 22
(Half mirror portion 11a)
Then, the half mirror 21 is completely exposed. The next annular regions B and C are the first and second increased reflectance regions, and the outermost region D is the maximum reflectance region.

The present invention is characterized in that the reflective films in the annular regions B and C are truncated fan-shaped reflective film segments 22 of various sizes. The truncated fan-shaped reflective film segment 22 has a shape obtained by removing (cutting) the center part from a fan shape centered on the center part (optical axis O) of the reflecting mirror 11, and the farther from the optical axis O the more the reflection becomes The area is getting wider. These truncated fan-shaped reflective film segments 22 are formed so that the intervals in the circumferential direction between the segments are substantially the same, and the length in the radial direction is set to be larger than the length in the circumferential direction.

In the annular regions B and C, the number of reflective film segments 22 is made different so that the average reflectance in the outer annular region C is higher than the average reflectance in the inner annular region B. That is, in the annular region B near the center, there are many truncated fan-shaped reflective film segments 22, and their size (area ratio to the non-adhering region of the reflective film) is small. Therefore, within a range where the average reflectance is small, the reflectance increases toward the periphery. Further, in the annular region C outside the annular region B, the number of truncated fan-shaped reflective film segments 22 is small and the size (same) is larger. Therefore, within a range where the average reflectance is large, the reflectance increases toward the periphery. In area D at the periphery of the reflective mirror 11, since the reflective mirror 11 has a rectangular shape, the reflective film is
It does not have a truncated fan shape, and the reflective film 23 occupies most of its area.

The reflectance distribution of the above reflecting mirror 11 is schematically shown in FIG. That is, the reflectance, which was 50% in the central region A, gradually increases as it moves to the annular regions B and C, and since the truncated fan-shaped reflective film segments 22 are fan-shaped in each region,
The average reflectance increases from the center to the periphery.

The broken line in the figure shows the reflectance distribution of the conventional reflecting mirror 11, where the reflectance in each region is constant and increases stepwise as it goes to the periphery. When this conventional reflectance distribution is compared with the reflectance distribution of the present invention, the superiority of the present invention is obvious.

The shape of the truncated fan-shaped reflective film segment 22 is as follows:
Due to the rectangular shape of the reflecting mirror 11 and the manufacturing technology of the vapor deposited film pattern that determines the non-adherent portion of the vapor deposited film (that is, the portion to be left as the half mirror 21), there is a difference in size between the annular regions B and C. exist. Even if such a size exists in the truncated fan-shaped reflective film segment 22, it is possible to obtain the effect that the reflectance increases in a portion farther from the optical axis O due to the fan-shaped truncated fan-shaped reflective film segment 22. can. In other words, the annular regions B and C do not need to be formed strictly by concentric circles, and it is sufficient if they are annular in macroscopic view. Further, in order to obtain a smoother reflectance distribution, the annular region may be further subdivided.

"Effects of the Invention" As described above, according to the reflective mirror of the single-lens reflex camera of the present invention, the reflectance can be changed more smoothly from the center to the periphery. This eliminates the sense of discomfort in the viewfinder field of view caused by the presence of a half mirror in the center of the reflective mirror.
A good viewfinder field of view can be obtained.

[Brief explanation of the drawing]

Figure 1 is a 1/4 plan view showing an embodiment of the reflective mirror according to the present invention, Figure 2 is a graph showing the reflectance distribution of the reflective mirror in Figure 1, and Figure 3 is the function of the reflective mirror in a single-lens reflex camera. FIG. DESCRIPTION OF SYMBOLS 11...Reflection mirror, 11a...Half mirror part, 12...Photographing lens system, 14...Finder optical system, 17...Light receiving element, 21...Half mirror, 22...Frunciated fan-shaped reflective film segment.

Claims (1)

[Claim for Utility Model Registration] A reflective mirror for a single-lens reflex camera that guides incident light from a photographic lens to a viewfinder optical system, the average reflectance of which is determined by the vapor deposition pattern of a reflective film on the half mirror. smallest in the center;
In a reflecting mirror that is set to increase in size at the periphery, imagine a plurality of concentric annular regions centered on the center of the reflecting mirror, and place the center within each of these plural annular regions. A plurality of truncated fan-shaped reflective film segments are formed by removing the center side from a central fan shape, and the intervals in the circumferential direction of these reflective film segments are made approximately constant, and the annular region on the outer peripheral side is so that the average reflectance is higher than the average reflectance of the inner annular area.
A reflective mirror for a single-lens reflex camera, characterized in that the number of reflective film segments in the annular region on the outer circumferential side is smaller than the number of reflective film segments in the annular region on the inner circumferential side.