JPS5952809B2 - Exposure control device for plate making camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a direct plate making camera in which a reflecting mirror and a photographing lens move relatively to change the magnification or reduction magnification. The purpose of this is to automatically change exposure appropriately.

Direct plate-making cameras are disclosed, for example, in Japanese Patent Application No. 51-157851 (Japanese Unexamined Patent Publication No. 53-82324) and Utility Model Application No. 10241-1983 (Japanese Utility Model Application No. 53-105) filed by the present applicant.
Publication No. 801) and No. 10242 (Utility Model Publication No. 1983-10)
No. 5802).

That is, in FIGS. 1 and 2, a box 1 is divided into a photographing section 2 and a darkroom section 3, and a horizontal document table 4, a reflector 5, and a camera 6 are attached to the photographing section 2. It has an optical axis slightly inclined from the horizontal position. However, the lever reflecting mirror 5 and the photographing lens 1 of the camera 6 are designed to move relative to each other as shown by solid lines and chain lines.
As a result, the plate-making magnification changes by approximately 60 to 120% to bring the image into focus. A plate master (photosensitive plate making material) 8 for direct plate making is housed in the darkroom part 3.
It passes through the focal plane of the rear surface of the camera, passes through a processing section 9 for developing, washing, etc. in the lower part of the box 1, and is taken out from an outlet 10.

As shown in the embodiments of the drawings, the photographing lens T is attached to the movable support plate 12 so as to be movable in the optical axis direction together with the reflecting mirror 5 on the rail 11. An aperture ring 13 for adjustment is provided.

A connecting piece 14 is fixed to this aperture ring 13, and a connecting link 15
It is connected to the rod 16 via.

The rod 16 is supported by a bearing IT provided on the movable support plate 12, and the rod 16 is slidable in the axial direction.
The tip of the rod 16 is threaded and adjustably connected to a forked piece 18 via a nut, to which a roller 19 is rotatably attached. Also, the rod 16 has a spring 20
5 in the direction of the roller 19. In order to make pressure contact with this roller 19, there is an inclined cam 21 having a linear inclined cam surface fixed in parallel to the moving direction of the moving support plate 12 and movable in the optical axis direction of the photographing lens on the sugar production 1 side. It is provided.

The connecting link 15 is connected by a long groove 22 so as not to hinder horizontal sliding of the rod 16, and the aperture range of the aperture ring 13 can be changed depending on the document to be photographed, the illuminance applied to it, etc. It may be adjusted and fixed to the connecting link 15 through the elongated hole 23 with a tightening screw 24. Furthermore, this adjustment can also be made so that the linear inclined cam 21 can be replaced with a linear inclined cam having a different angle of inclination. In the optical device, the exposure time T(1+m)2 when the magnification is m is theoretically FfCT=? In other words, it is proportional to the square of the change in the effective F-number (1+F).

If this is drawn as a curve of 60 to 120% of the magnification range of the plate-making camera, it becomes a substantially straight line. On the other hand, the relationship between the amount of movement of the lens of the plate-making camera and the magnification is x=Y(MM-m), and when this is graphed, it also has a substantially linear proportional relationship. Therefore, with the above-mentioned device of the present invention, it is possible to adjust the exposure amount with respect to changes in magnification by opening and closing the aperture of the taking lens 7 in relation to the amount of movement of the taking lens 7, which is moved in response to changes in magnification. can. Therefore, compared to the conventional TTL method using Cbs, it does not require an electric circuit or a rotating cam with a cam surface made of a special curved surface that is difficult to manufacture, and has a mechanical configuration that is easy to manufacture and inexpensive. Since the control is made possible by using an inclined cam having a linear cam surface, this type of device can be provided at low cost, is free from failure, is highly durable, and can be operated easily.

j The simple explanatory diagrams in the drawings show an embodiment of the apparatus of the present invention. Fig. 1 is a partially cutaway side view of a small direct plate making camera, Fig. 2 is a plan view of the same, and Fig. 3 is a cutaway of the main part. The front view and FIG. 4 are also plan views.

1 is a container box, 5 is a reflector, 6 is a camera, 7 is a photographic lens, 12 is a movable support plate, 13 is an aperture ring, 14 is a connecting piece, 15 is a connecting link, 16 is a rod, 20 is a spring, 21 is an inclined cam.

Claims (1)

[Claims] 1. In a plate-making camera in which the positions of the photographing lens and reflector are automatically moved according to the photographing magnification to change the photographing magnification, a bearing is provided on the support plate for moving the photographic lens, and a rod can be freely slid in the axial direction on this. One end of the rod is pivotally connected via a connection link to a connecting piece attached to the aperture ring provided on the photographic lens, a roller is attached to the other end with a spring interposed, and a movable support plate is attached to the instrument box. A linear inclined cam having a cam surface parallel to the moving direction of the rod is provided, and a roller at the other end of the rod is pressed against this cam surface by a spring, and the linear inclined cam is moved in conjunction with the movement of the photographing lens and the reflector. Accordingly, an exposure control device for a plate-making camera is characterized in that the rod pivots and the aperture ring is rotated to increase or decrease the amount of light in accordance with changes in photographic magnification using the aperture of the photographic lens.