# US 4,397,534 A · Device for displaying bulb photographing operation time in a photographic camera

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- Number: US 4,397,534 A
- Document ID: US4397534A
- Status: Granted
- Kind: A
- Application number: 06/379,910
- Filed: 1982-05-19
- Granted: 1983-08-09
- Earliest claimed: 1980-05-14
- Assignees: Canon Kabushiki Kaisha
- Inventors: Nobuaki Sakurada; Nobuaki Date; Masami Shimizu; Hiroshi Aizawa
- Web page: https://patentgrep.com/patent/US4397534A

## CPC

- G03B 17/18: Signals indicating condition of a camera member or suitability of light (indicating depth of field G03B13/30)
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

A display device for displaying the time of a bulb photographing operation is arranged so that a counter for counting the clock pulses starts to operate when the bulb photographing mode is set in the camera and the release operation of the camera is started. A decoder incorporated in the camera decodes the content of the counter and a display instrument displays the output of the decoder in such a manner that the photographer can visually recognize the bulb photographing operation time. Several embodiments of the circuitry for controlling the nature of the display, including timing charts therefor, are set forth.

## Claims

### Claim 1

A display device for a photographic camera, comprising:
(a) means for producing a release signal in response to a release operation of the camera;
(b) means for producing a bulb phtographing setting signal in response to setting of a bulb photographing mode of camera operation;
(c) a counter for counting a number of input pulses and providing a counter output;
(d) a decoder for decoding the output of the counter;
(e) display means for displaying the output of the counter; and
(f) control means for enabling the display means to display the output of the counter the content of which varies successively, when both of the release signal and the bulb photographing setting signal are applied to input terminals of the control means.

### Claim 2 (depends on 1)

A display device according to claim 1, wherein the control means comprises of a gate circuit including a first input terminal connected to the release signal producing means and a second input terminal connected to the bulb photographing setting signal producing means.

### Claim 3 (depends on 2)

A display device according to claim 2, wherein the gate circuit includes an AND gate coupled to a reset terminal of the counter for initiating the counting operation of the counter upon receipt of both of the release signal and the bulb photographing setting signal.

### Claim 4

A display device for a photographic camera, comprising:
(a) means for producing a release signal in response to a release operation of the camera;
(b) means for producing a bulb photographing setting signal in response to setting of a bulb photographing mode of camera operation;
(c) a counter for counting a number of input pulses and providing a counter output;
(d) a decoder for decoding the output of the counter;
(e) display means for displaying the output of the counter; and
(f) control means for enabling the display means to display the output of the counter the content of which varies successively, after both of the release signal and the bulb photographing setting signal have been produced.