RU2305306C2 - Viewfinder for continuous sighting - Google Patents

Abstract

FIELD: optical instruments.

SUBSTANCE: viewfinder comprises pentagonal prism, objective lens, and ocular. The pentagonal prism is made of mirror surface composed of mirrors and rotating image-recovering mirror that rises synchronously with the movable mirror of photographic camera. The trajectory of the rise of the rotating mirror differs from the circular trajectory.

EFFECT: expanded functional capabilities.

4 cl, 3 dwg

Description

Technical field

The invention relates primarily to a viewfinder for a single-lens reflex camera.

State of the art

In known devices, the image of the photographed object formed by the lens using an inclined mirror, moving or stationary partially transparent, is displayed on the focusing screen and is sent through the eyepiece through the eyepiece to the eye of the operator. Before the camera shutter is released, the movable mirror is in a horizontal position, the image in the viewfinder disappears, and the aperture of the lens assumes the working value. After that, the shutter fulfills the set shutter speed. The photosensitive surface is exposed to beams carrying the image from the camera lens. After closing the shutter, exposure stops, the movable mirror of the camera and the aperture of the lens return to their original position. The image of the photographed object reappears on the focusing screen.

In the aforementioned known devices of this type, the image obtained by the focusing screen that the operator observes during the period of raising the mirror, the shutter is open and, accordingly, the photosensitive surface is exposed, disappears and the operator loses control over the photographing object, which is a significant drawback. The design of the camera with a fixed partially transparent mirror is not widespread due to the negative effect of the fixed mirror on the lens parameters. In addition, when the aperture is triggered to the operating value, in general, the brightness of the image on the focusing screen decreases stepwise, which sharply worsens the sight and creates visual discomfort for the operator.

In addition, in situations where photographing does not allow additional camera vibrations from impacts of the mirror, when the camera is operated with a previously raised mirror, control of the subject is lost for an even longer time.

These shortcomings are so significant that in a number of photographic situations they sharply limit, and sometimes make it impossible to use single-lens reflex cameras.

Known technical solutions aimed at eliminating these shortcomings.

For example, patents No. 900410, cl. 57a gr. 9/10 and No. 922 325, cl. 57a gr. 9/10.

The essence of this invention lies in the fact that when lifting the movable mirror of the camera, the pentaprism also rises 4. After that, the operator can observe the photographed object through the opened objective lens of the viewfinder 3, which together with the eyepiece 2 form a well-known Galilean-type viewfinder.

The disadvantages of this technical solution are the bulkiness of the design, the large masses of moving elements, which dramatically affects the speed of the camera, as well as the lack of a parallax compensation mechanism. These shortcomings exclude the possibility of practical application of this design.

Other attempts to solve this problem are known. For example, patent No. 839312, class. 57a gr. 9/10. The author proposed the design of a hybrid camera, which, being essentially a single-lens reflex, has another Galilean type viewfinder located on the other side of the camera. Obvious cumbersomeness and inconvenience of use also exclude the practical application of such a technical solution.

The design of the viewfinder described in patent No. 864049, class. 57a gr. 9/10, is also extremely complex, contains 3 movable mirrors, which entails additional technical difficulties in synchronizing and adjusting them. Due to these shortcomings, this design also did not find practical application.

Known design of the viewfinder for single-lens reflex cameras - Patent No. 2023730, class. 57a gr. 9/10, which uses elements similar to this invention, namely: a mirrored roof-like surface and a rotary image-restoring mirror. However, firstly, the axis of rotation of the rotary part of the mirror surface is different from the design proposed in the invention, and secondly, this viewfinder is designed to solve another problem, namely: changing the direction of sight, therefore, can not serve as a prototype of this invention.

In the design of the viewfinder, patent No. 968405, class. 57a gr. On 9/10, an attempt was made to solve the problem - to maintain control of the photographing object with the movable mirror of the camera raised at the time of exposure of the photosensitive surface. To achieve this goal, in the design of the said patent, raising the movable mirror of the camera 3 and lowering the reflecting mirror of the viewfinder 5 is synchronized with the horizontal displacement of the mask 9, the objective lens 13 and one of the ocular lenses. The operator gets the opportunity to continue monitoring the photographed object at the time of exposure of the photosensitive surface 2 through the optical viewfinder of the inverted Galilean type, formed by an objective lens 13 and an eyepiece 7 (Fig.3). After the exposure, the mirrors 3 and 5, as well as all the movable elements 6, 9 and 13 are returned to their original position (figure 2).

The disadvantages of the described design include excessive complexity, the presence of reciprocating movements of the elements 6, 9 and 13, the rotational movement of the reflecting mirror 5, the need for their synchronization with the movement of the main mirror 3. This leads to an increase in the dimensions of the viewfinder (and, accordingly, the camera), which entails additional costs for adjustment and maintenance, an increase in the moving masses of the viewfinder and, as a result, a decrease in speed; also a disadvantage is the lack of a parallax compensation mechanism.

These shortcomings exclude the possibility of practical application of this design.

Finally, as the closest analogue, we can consider the viewfinder circuit described in utility model No. 21094 of July 23, 2001, in which a solution to the problem is proposed - maintaining control of the photographing object with the movable mirror of the camera raised at the time of exposure of the photosensitive surface. However, the proposed design of the viewfinder contains the following disadvantages:

1. Reduced image scale of the photographed object observed in the eyepiece, compared with cameras equipped with known mirror viewfinders.

2. Changing the brightness of the image when switching the channel of sight from mirror to reversed Galileevsky.

3. The absence of a simple system for zooming in on a photographed object observed in the eyepiece when replacing a standard camera lens with lenses with a greater or lesser focal length (except for super wide-angle and super-telephoto lenses).

These disadvantages are excluded in the proposed design of the invention.

Disclosure of invention

The technical task of this invention is to provide a viewfinder that eliminates the disadvantages of single-lens reflex cameras, namely the disappearance of the observed photographic object in the viewfinder at the time of exposure, as well as providing for monitoring the photographed object without an additional viewfinder when the camera is operated with a pre-raised mirror, which increases the sharpness of photographs taken due to the lack of camera vibration from impacts of the movable mirror.

This object is achieved in that in the design of the viewfinder of the present invention, a mirrored roof-shaped surface consisting of separate mirrors is used as a known pentaprism. Moreover, the rotary image restoration mirror can be rotated around the horizontal axis synchronously with the movement of the movable mirror of the camera, opening up the possibility for the operator to observe the photographed object through the eyepiece of the viewfinder and the lens mounted in front of the rotational image restoration mirror, forming with the eyepiece a well-known Galilean-type inverted optical viewfinder. The parameters of the eyepiece and lens (hereinafter referred to as the objective lens of the viewfinder) are selected so that the photographed object is displayed by the viewfinder at the same scale when observing both through a standard camera lens (when the movable mirror of the camera is in the lower position) and when observing through an objective lens viewfinder, which is connected to the lens in such a way that when focusing the camera lens at various distances, it has the ability to move vertically to compensate for parallax. In addition, if you replace a standard camera lens with a lens with a different focal length or install a zoom lens on the camera, an associated discrete or zoom converter can be installed in front of the objective lens of the viewfinder to maintain the scale of the observed object.

The magnification of the zooming converter changes in proportion to the change in the focal length of the camera lens, either through communication between the converter and the lens, or manually.

In order to increase the image scale of the photographed object observed through the eyepiece, to exclude changes in brightness when switching the viewing channels, and also to use the viewfinder with medium format cameras equipped with interchangeable film shops or digital set-top boxes, the following design solutions were applied:

1. The elevation path of the rotary image restoring mirror is different from the circular one, which allows increasing the mirror size while maintaining the dimensions of the roof-shaped mirror surface.

2. The rotary image restoration mirror has a concave reflective surface.

3. A light filter is installed in front of the objective lens of the viewfinder, which allows leveling the image brightness on both observation channels.

4. When replacing a standard camera lens with a lens with a larger or smaller focal length (except for ultra-wide-angle and super-telephoto lenses), the viewfinder objective lens can be replaced with a lens with a correspondingly greater or lesser negative diopter. In this case, the converter is not used.

5. A telescopic lens is installed after the eyepiece lens of the viewfinder.

Thus, the design proposed in this invention eliminates the disadvantages of single-lens reflex cameras and the above points are different from the known closest analogue.

Brief Description of the Drawings

Figure 1 and figure 2 presents a diagram of the design options of the viewfinder.

The viewfinder is mounted on a well-known single-lens reflex camera containing a lens 1, a movable mirror 9, a focusing screen 8.

The letter A denotes the relationship between the focusing of the lens 1 and the vertical movements of the objective lens of the viewfinder 4.

The letter B indicates the relationship between changes in the focal length of the lens 1 and the change in the multiplicity of the Converter 2.

The viewfinder contains a mirror roof-shaped surface 5, a rotary image-recovery mirror 10 with an axis of rotation 11, a zoomable or discrete converter 2, a light filter 3, an objective lens 4, an eyepiece of the viewfinder 6, a telescopic lens 7.

Figure 1 presents the viewfinder diagram without the use of a converter.

Figure 2 presents a viewfinder diagram using a converter.

Figure 3 presents a viewfinder diagram in a spatial image.

The implementation of the invention

In the initial state, the movable mirror of the camera 9 and the rotary image recovery mirror of the viewfinder 10 are in the lower position. The aperture of lens 1 is fully open. The image of the object being photographed, formed by the camera lens 1 through the mirror 9, is displayed on the focusing screen 8 and after re-reflections in the roof-shaped mirror surface 5 and the image-restoring mirror 10 through the eyepiece 6 and the telescopic lens 7 is directed to the eye of the operator.

Before photographing, the operator selects the image scale of the future photograph either by zooming in on lens 1 (if a zoom lens is used on the camera), or approaching or moving the camera away from the subject to be photographed, if the camera has a lens with a constant focal length.

In the case of zooming of the lens 1 by means of communication B (or manually), the converter 2 is zoomed (Fig. 2).

In the case of using a lens with a constant focal length other than the standard one, the objective lens of the viewfinder is replaced with a lens with an appropriate magnification, or a converter with a magnification corresponding to the focal length of the mounted lens is mounted in front of the lens 4.

Next, the lens 1 focuses on the photographed object. In this case, through communication A, a corresponding vertical movement of the objective lens of viewfinder 4 and the associated converter 2 (if used) occurs to compensate for parallax.

After the trigger of the camera is triggered, the diaphragm of the lens 1 assumes the operating value, the movable mirror 9 and the rotary image restoring mirror 10 synchronously occupy the upper position (indicated by a dotted line in the drawing). The image on the focusing screen disappears, but the operator continues to observe the photographed object through a telescopic lens 7, an eyepiece 6, an objective lens 4, a light filter 3 and a converter 2 (if used), which together form a well-known Galilean-type viewfinder. The camera shutter opens; exposure of the photosensitive surface occurs. After closing the shutter, exposure stops, mirrors 9 and 10, as well as the aperture of lens 1, are returned to their original position. The operator continues to observe the object being photographed, but already shown by the lens 1 on the focusing screen 8. If the camera does not have the function of returning the movable mirror 9 after the shutter has been released (for example, “Hasselblad” or “Kiev”, in which the viewfinder is darkened) in the described design of the viewfinder, the possibility of sighting remains.

Thus, the problem of continuous observation in the viewfinder of a single-lens reflex camera of the photographed object at the time of exposure is solved. In addition, when operating the camera with a pre-raised mirror 9, in contrast to the well-known single-lens reflex cameras, the operator continues to monitor the subject being photographed without using an additional interchangeable viewfinder. In this case, the image focused by the lens 1 on the photosensitive surface is sharper due to the lack of camera vibration from impacts of the movable mirror 7. The time interval between pressing the shutter button and the camera shutter is reduced.

Claims (5)

1. The continuous viewfinder for a single-lens reflex camera, eliminating the disappearance of the image during the exposure period, containing a pentaprism, an objective lens, an eyepiece, while this camera contains a lens, a movable mirror, a focusing screen, and a pentaprism uses a mirrored roof-shaped surface consisting of separate mirrors and includes a rotary image recovery mirror that rises synchronously with the raising of the movable camera mirror, open giving the operator the possibility of observing the photographed object through the eyepiece of the viewfinder and an objective lens mounted in front of the rotary image-recovery mirror, forming with the eyepiece an optical viewfinder of the inverted Galilean type, characterized in that the trajectory of raising the rotary mirror is different from circular, which allows to increase the size of the mirror while maintaining dimensions of the mirrored roof-shaped surface. 2. The viewfinder according to claim 1, characterized in that the rotary image restoring mirror has a concave reflective surface. 3. The viewfinder according to claim 1, characterized in that a light filter is installed in front of the objective lens of the viewfinder. 4. The viewfinder according to claim 1, characterized in that the objective lens is removable with the possibility of replacement with a lens with a different diopter. 5. The viewfinder according to claim 1, characterized in that a telescopic lens is installed after the eyepiece lens of the viewfinder.

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