JPH043529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus adjustment device that allows a camera with a fixed photographing lens to focus on objects at different photographing distances while the photographing lens remains fixed. be.

In other words, in popular cameras, the photographing lens remains fixed and the lens and film are connected, instead of using a complicated structure in which the lens is moved and adjusted using a helicoid or the like according to the distance of the subject. By changing the effective optical path length from the lens to the film using an extremely simple method of inserting and removing a parallel plane glass perpendicular to the optical axis during This makes it possible to focus on the subject.

To explain the present invention with reference to the drawings, in FIG. , F is the imaging plane of B, and the positional deviation is a.As is clear from the figure, if the film is placed at position F', the image by the light beam A will form a clear image, but the image of B will be clear. The image created by the light beam becomes blurred.

Also, if a film is placed at position F, the opposite effect will be obtained.

In Figure B, if 3 is a parallel plane glass and the other things are the same as A, the light ray from the distant object is refracted by the parallel plane glass 3 of the required thickness, and then the position of F is shifted by a from the position of F. It is possible to match the position of ', that is, the imaging plane of A. If the thickness of 3 is t, then t≒3a Therefore, if you place the film at position F' and remove 3 when photographing subject A, and attach 3 when photographing subject B, the lens And, while the position of the film remains fixed, it is possible to clearly photograph subjects both near and far.

Of course, by changing the thickness of 3, the distance to the ray (b), that is, the distance to the distant object, can be freely selected.

It goes without saying that if a plurality of 3 (parallel plane glasses) of different thicknesses are prepared and one of them is attached as necessary, images of a plurality of objects can be clearly photographed.

In addition, in the present invention, a parallel plane glass is attached and detached between the lens and the film (actually, right after the lens), but when taking pictures, the following situation can be used: ( 1) When parallel plane glass is not included, (2) When parallel plane glass is included.In the case of (2) above, thin and thick glasses, that is, multiple glasses of different thickness, are prepared and the distance to the target subject is determined. Insert one piece of appropriate thickness depending on the length. (However, in practice, only one or two pieces of glass will be prepared.) The second figure is a mechanical diagram when the present invention is specifically implemented in a camera, and shows the lever 4 that operates the strobe 2. The tip of the frame that is linked to the frame is connected to the parallel plane glass, so that by moving the lever 4, the parallel plane glass 3 can be attached and detached between the lens 1 and the focal point (image forming point) of the film. By doing so, the above-mentioned effects can be achieved.

Note that 5 indicates a frame, and 6 is a lever operating knob. With this structure, the present invention provides a fixed-focus camera with a single lens between the photographic lens and the film.
Parallel plane glasses of different thicknesses are interposed one by one using a lever, and the optical path length from the lens to the film can be changed by attaching and detaching them, thereby changing the distance from the camera. A device that sharply forms images of multiple different subjects while keeping the photographic lens fixed, and achieves the same effect as when focusing on each subject by moving the photographic lens. It is.

In this way, the device of the present invention is attached to a frame that moves with a lever, so depending on the distance, the parallel plane glass plate can be moved in and out between the lens and the film to focus either way. Since the glass plate 3 can be easily operated in conjunction with appropriate switching, the user has to make various changes according to the shooting conditions. It is easy to take pictures without requiring any complicated and highly technical operations or judgments, and the focus is accurate, resulting in photographs in extremely good condition. The fact that it has an extremely simple configuration makes it an excellent invention.

[Brief explanation of drawings]

A and B in Figure 1 are explanatory diagrams of the relationship among the lens, parallel plane glass plate, projected light beam, and focal point. Figure 2 is a perspective view of the inside of the camera. 1...Lens, 2...Strobe, 3...Parallel plane glass , 4... Contact lever, 5... Frame,
6...knob, F, F'...focus.

Claims (1)

[Claims] 1. In a fixed focus camera, a parallel plane glass is removably interposed between the photographing lens and the film,
By attaching and detaching the parallel plane glass, the optical path length from the lens to the film can be changed, so that images of objects at different distances from the camera can be clearly formed while the photographic lens is fixed. Focus adjustment device for fixed focus cameras.