JPS6234146A - Single-lens reflex camera - Google Patents

Abstract

PURPOSE:To lighten the weight of a submirror holding frame and to minimize the inertia mass by making plural through holes on the submirror holding frame and covering them with a light shielding sheet. CONSTITUTION:When a camera is released, a main mirror holding frame 41 springs upward a mirror box with a pin spindle 43 as a center and makes a turn. Interlocking with this turn, the submirror holding frame 51 is folded on the reverse side of the main mirror holding frame 41 with a pin spindle 53 as a center, and both a main mirror 4 and a submirror 5 retreat from a light path made of a photographing flux L making incident on the mirror box 3 from a lens barrel side. Due to the operation of a shutter 7, photographing is done, and the main mirror 4 and the submirror 5 return to a finder observing position again. In order to reduce the weight, plural through holes 54 are made on the surface of the submirror holding frame 51, and the light shielding sheet 55 light-shielding said holes 54 is stuck to the fitting side of the submirror 5 of the submirror holding frame 51. A material subjected to reflection preventing treatment such as dull finish is used for the light shielding sheet 55.

Description

[Detailed description of the invention] - A. Purpose of IJ+ [Industrial field of application] IJJ+ is a single-lens reflex camera, more specifically, it is rotatably supported on a mirror box, and the photographing lens is mounted at the viewfinder observation position. a main mirror having a semi-transmissive part that guides the light flux that passes through the main mirror to the finder and reciprocates between the finder observation position and the photographing position; and a light flux that is disposed behind the main mirror and passes through the semi-transmissive part of the main mirror. The present invention relates to a single-lens reflex camera having a sub-mirror that guides the light to a photometer or distance-measuring device disposed on the lower surface of the mirror box and retreats out of the photographing optical path in conjunction with the movement of the main mirror to the photographing position.

[Conventional technology]

In a single-lens reflex camera, the main mirror that reflects the light beam that has passed through the photographic lens toward the viewfinder has two positions: one is the viewfinder observation position where it crosses the photographing light beam at 45 degrees, and the other is the photographic position where it retreats from the photographic light beam and exposes the film. It is configured to reciprocate between the two. Therefore, it has the disadvantage that the subject cannot be observed from the time the camera is released and the main mirror starts retracting to the photographing position until the photographing is completed and the camera returns to the viewfinder observation position.

In order to eliminate this drawback, today's single-lens reflex cameras make the reciprocating movement of the main mirror as fast as possible, thereby minimizing the time during which the viewfinder cannot be detected. However, on the other hand, the vibration that occurs during operation or the shock when operation stops becomes too large to ignore and is one of the causes of so-called camera shake, and the increase in driving force required for high-speed operation increases the winding force. This made the curly beard taste bad.

And, in a single-layer reflex camera that uses a secondary mirror to guide the light flux to the Δ11 light or distance measuring device,
The inertial mass of the secondary mirror and the secondary mirror holding frame is added, and the secondary mirror holding frame is made large enough to prevent the light flux that has passed through the semi-transparent part of the primary mirror from directly reaching the shutter and causing light leakage. This problem is exacerbated by the fact that it has to be done.

In addition, in a single-lens reflex camera with a secondary mirror, regardless of the operating method of the secondary mirror, when the secondary mirror is retracted from the shooting position, the inner space of the mirror box is reduced by the amount of the secondary mirror and the secondary mirror holding inspection. It also had the problem of increasing reflections.

[Problem that the invention seeks to solve]

It is an object of the present invention to eliminate the above-mentioned drawbacks and problems particularly with respect to a single-lens reflex camera having a secondary mirror.

Summary, Structure of the Invention [Means for Solving the Problems] The present invention is rotatably supported by a mirror box, guides a light flux passing through a photographing lens to a finder at a finder observation position, and adjusts the angle between the finder observation position and the photographing position. It operates reciprocally. A main mirror having a semi-transparent part is arranged behind the main mirror, and the light beam passing through the semi-transparent part of the main mirror is guided to a photometer or distance measuring device arranged on the lower surface of the mirror box, In a single-lens reflex camera having a sub-mirror that is retracted out of the photographing optical path in conjunction with movement to the photographing position, a through-hole is provided in a flat part serving as a sub-mirror mounting surface of a sub-mirror holding frame that supports the sub-mirror; ,] [1] A single-lens reflex camera characterized in that a light-shielding sheet for shielding light from the through hole I is attached to the sub-mirror mounting surface side of the sub-mirror holding frame.

[For production]

That is, in the present invention, a large number of through-holes are made in the sub-mirror mounting surface of the sub-mirror holding frame to reduce heavy loads, and at the same time these through-holes are covered with a light-shielding sheet. This is to reduce the inertial mass of the sub mirror holding frame while maintaining the same. Therefore, it is possible to operate the main mirror and the sub-mirror without increasing the winding torque, and it is also possible to reduce camera shake by alleviating the impact when the operation is stopped. The uneven shape on the back surface of the sub-mirror holding frame formed by the through hole hits the back surface of the sub-mirror holding frame when the sub-mirror is retracted to the shooting position, and prevents internal reflection by diffusing the light flux projected onto the film. It is also effective.

〔Example〕

The drawings show an embodiment of a single-lens reflex camera according to the present invention. Fig. 1 is a longitudinal side view when the main mirror and sub mirror are in the finder observation position, and Fig. 2 is a longitudinal side view when the main mirror and sub mirror are in the viewfinder observation position. It is a partial vertical side view in the state where it is located.

In the figure, ■ is the camera body, 2 is the lens barrel mount on the front side (the lens barrel is omitted from the diagram),
3 is a mirror box inside the camera body, 4 and 5 are a main mirror and a sub mirror arranged in the mirror box, 6 is a photometer or distance measuring device arranged on the bottom of the mirror box, and 7 is a mirror box. The shutter 8 on the back side is a finder section disposed at the top of the camera body, and is composed of a focusing plate 9, a condenser lens 10, a pentaprism 11, an eyepiece 12, and the like.

The main mirror 4 is fixedly supported by a main mirror holding frame 41 which is rotatable with respect to the camera body 1 around a bottle shaft 43.

Further, the main mirror 4 has a semi-transparent part 4a, and the semi-transparent part 4
The surface portion of the main mirror holding +S41 corresponding to a is an opening (
Translucent) 42.

The secondary mirror 5 is attached to the main mirror holding frame 4 via an arm 52 around a bottle shaft 53 on the rear side of the main mirror holding frame 41.
1, it is fixedly supported by a rotatable sub-mirror holding frame 51.

In the state shown in FIG. 1 where the main mirror 4 and the sub mirror 5 are at the viewfinder observation position, the main mirror 4 reflects the photographing light beam entering the mirror box 3 from the lens barrel side diagonally by 45''. The surface is held in an oblique I-direction position, and the sub-mirror 5 is held behind the main mirror 4 in a reflecting surface diagonally downward position fE.

The photographing light beam entering the mirror box 3 from the lens barrel side is reflected L1 upward by the main mirror 4 and is imaged on the focusing plate 9 surface. The image is formed in the finder section 8,
That is, it is observed using an optical system including a condenser lens 10, a pentaprism 11, and an eyepiece lens 12.

On the other hand, a portion L2 of the photographing light beam incident on the semi-transparent part 4a of the main mirror 4 passes through the semi-transparent part 4a to the back side of the main mirror, passes through the opening 42 of the main mirror holding frame 41, and passes through the semi-transparent part 4a to the sub mirror 5. The light enters the surface, is reflected by the surface of the sub-mirror 5, and enters the photometering or distance measuring device 6.

When the camera is released in the state shown in Figure 1 above,
A drive mechanism (not shown) causes the main mirror holding frame 41 to flip upward and rotate around the bin shaft 43 as shown in the second figure.

In conjunction with this, the sub mirror holding frame 51 is also folded and rotated around the bottle shaft 53 to the back side of the main mirror holding frame 41, and both the main mirror 4 and the sub mirror 5 are moved from the lens barrel side into the mirror box 3. Then, the shutter 7 is operated to take a picture,
Next, the main mirror 4 and the sub mirror 5 return to the finder observation position shown in FIG. 1 again.

A large number of through holes 54 are formed in the surface of the secondary mirror holding frame 51 in accordance with the present invention to reduce the weight.
A sheet 55 for blocking light from the mirror 4 is pasted on the side of the sub-mirror mounting surface of the sub-mirror holding frame.

FIG. 3 is an enlarged partially cutaway front view of the pocket secondary mirror holding frame 51. Each through hole 54 formed in the holding frame 51 surface of this example
The through holes 54 are all circular holes with the same diameter.The shape of the through holes 54 is not limited, and may be, for example, hexagonal or square.Also, depending on the attachment position of the sub-mirror 5, the frame surface portions that do not require much strength may be used. The through-holes formed in the frame surface may be arranged to be larger, or the through-holes formed in the frame surface portion where there is a lot of internal reflection may be arranged densely. The light-shielding sheet 55 is one that has been subjected to anti-reflection treatment such as matte treatment or matte coating, and is, for example, an opaque plastic sheet that has been treated with anti-reflection treatment or a thin metal plate that has been treated with anti-reflection treatment. Covering the formed through hole 54,
The light beam passing through the through hole 54 and projected onto the shutter 7 in the finder observation position state shown in FIG. 1 is blocked. In the example shown in FIG. 3, no light-shielding sheet is attached to the surface of the sub-mirror holding frame 51 to which the sub-mirror 5 is attached, and the through-hole in that surface is shielded from light by the sub-mirror 5 itself. An opening 56 having approximately the same shape as the outer shape of the secondary mirror 5 is pre-drilled in the surface portion of the light-shielding sheet 55 that is attached to the surface corresponding to the sub-mirror 5, and serves as a guide when attaching the light-shielding sheet 55 to the frame 51 surface. It can also be used as

FIG. 4 is a diagram showing the effect of the present invention on internal reflection after the main mirror 4 and the sub mirror 5 have retreated to the photographing position.
Luminous flux L projected onto the back surface 51a of the sub-mirror holding frame 51
3, the light that enters the through hole 54 is absorbed by the sub-mirror holding frame 51 and the light-shielding sheet 55 due to repeated reflections, and as the amount of light decreases, it is also diffused, and only a part of the light flux L4 is reflected to the shutter 7. Become.

C. As described in detail, the present invention provides a large number of through holes 54 in the sub-mirror holding frame 51, and furthermore, a light shielding sheet 55 is provided in the through holes 54.
4 has the effect of reducing the weight of the sub-mirror holding frame 51 and reducing its inertial mass. This makes it possible to speed up the operation of the mirror without increasing the winding torque and shorten the time the viewfinder image disappears.
Camera shake caused by p+ shots can also be reduced.

In general, the sub-mirror holding frame 51 provided with a large number of through holes 54 improves light diffusion, so when the mirror is retracted to the shooting position, the light beam hitting the back side of the holding frame is reflected to the camera 2 tough. It is also effective in preventing IF from internal reflection.

In addition, although there is a conventional method of removing the thickness of the mirror holding frame 51 by etching, the reduction rate of the weight of the remaining portion is lower than that of the present invention, and if the depth of the four parts is the same thickness, Since the depth is shallower than that of the present invention, the effect of preventing internal reflection is also inferior to that of the present invention.Furthermore, while thinning by etching is time consuming and expected to increase costs, the present invention is short and shallow due to press processing. It is possible to process a large amount in a short amount of time and to reduce costs.

[Brief explanation of drawings]

The drawings show an embodiment of the camera according to the present invention. Figure 1 is a vertical side view showing the main mirror and secondary mirror in the viewfinder observation position, and Figure 2 is a partial side view of the camera when they are retracted to the photographing position. FIG. 3 is a partially cutaway enlarged front view of the sub-mirror holding frame, and FIG. 4 is a diagram showing the internal reflection state of the sub-mirror holding frame. 4 is the main mirror, 41 is its holding frame, 5 is the sub mirror, 51
54 is a holding frame thereof, 54 is a number of through holes formed in the surface of the holding frame, and 55 is a light shielding sheet. Figure 2

Claims (4)

[Claims] (1) A main mirror having a semi-transparent part, which is rotatably supported by a mirror box, guides the light flux that passes through the photographing lens at the finder observation position to the finder, and reciprocates between the finder observation position and the photographing position; It is placed behind the main mirror, and guides the light beam passing through the semi-transparent part of the main mirror to a photometer or distance measuring device placed on the bottom surface of the mirror box, and takes pictures in conjunction with the movement of the main mirror to the shooting position. In a single-lens reflex camera having a sub-mirror that is retracted out of the optical path, a through-hole is provided in a flat part of a sub-mirror holding frame that supports the sub-mirror and serves as a sub-mirror mounting surface, and a light-shielding sheet is provided to block light from the through-hole. A single-lens reflex camera, characterized in that the sub-mirror holding frame is attached to the sub-mirror mounting surface side. (2) The single-lens reflex camera according to claim 1, wherein the light-shielding sheet is formed from an opaque plastic sheet treated with anti-reflection treatment. (3) The single-lens reflex camera according to claim 1, wherein the light-shielding sheet is formed from a thin metal plate subjected to anti-reflection treatment. (4) A hole having the same shape as the outer shape of the secondary mirror is provided in the light-shielding sheet, and the light-shielding sheet is provided to block light from the through hole other than the attachment surface of the secondary mirror, and The single-lens reflex camera according to claim 1, wherein the back surface is subjected to antireflection treatment.