Digital control camera

• US 4,235,538 A
• Filed: 12/22/1978
• Issued: 11/25/1980
• Est. Priority Date: 10/21/1975
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Taguchi, Tetsuya, Aizawa, Hiroshi, Uchidoi, Masanori, Iwashita, Tomonori, Ichiyanagi, Toshikazu, Iura, Yukio
• Primary Examiner(s): Hix, L. T.
• Assistant Examiner(s): Perkey, William B.
• Application Number:
  US05/972,322
• Time in Patent Office: 704 Days
• Field of Search: 354/23 D, 354/60 R, 354/60 L, 354/60 E, 354/266, 354/268
• US Class Current: 396/266
• CPC Class Codes: G03B 7/093 for control of exposure time
• CPC Class Codes: G03B 7/097 for control of both exposure time and aperture

Abstract

A camera having an exposure control device or, more particularly, having a digital control circuit for controlling exposure. Sequence control over a photographing operation and control over a display operation are both accomplished by the same sequence control circuit, which is simplified and yet permits selection between self-timer photographing and ordinary photographing operations.

Claims

1. A camera comprising:

(a) connection means for connection to a power source;

(b) a warning signal forming circuit coupled to said connection means for detecting the voltage at the connection means and for producing a warning signal when the voltage drops to a value less than a given voltage value;

(c) a photographic operation start signal forming means for producing a signal for starting a photographic operation;

(d) operating means coupled to the start signal forming means and said warning signal forming circuit for performing a photographic operation, said operating means including a releasable shutter and a sequence control circuit for producing control signals in a time sequence for controlling photographic sequence operations and for producing at least a control signal for releasing the shutter; and

(e) an operation circuit in said operating means responsive to the signal from said photographic operation start signal forming means for producing a signal to render said sequence control circuit operative to start control over a sequence of photographing actions, said operation circuit being arranged for inhibiting the signal which renders said sequence control circuit operative when said warning signal is issued.

2. A camera according to claim 1 in which said operation circuit includes flip-flop means, a gate circuit connected to the input terminal of said flip-flop means for producing a signal when the signal from photographic operation start signal forming means is produced, said flip-flop means for producing an output to render said sequence control circuit operative in response to the signal from the gate circuit, said gate circuit inhibiting production of said signal from the gate circuit in response to said warning signal independent of the signal from the photographic operation start signal means.

3. A camera according to claim 2 in which said sequence control circuit includes a pulse generator and a counter for counting the pulses from pulse generator.

4. A camera comprising:

(a) connection means for connection to a power source;

(b) a display circuit coupled to said connection means for displaying photographic information;

(c) photographing operation start signal forming means which produces a start signal for starting photographing operation;

(d) operation means coupled to the start signal forming means and the display circuit for performing a photographic operation, said operation means including a sequence control circuit connected to said connection means for producing control signals for controlling the photographic sequence operations, said sequence control circuit becoming operative for starting control over a sequence of photographing action in response to said start signal from photographing operation start signal forming means; and

(e) a warning signal forming circuit coupled to the connection means and the sequence control circuit for detecting the voltage at the power source and for producing a warning signal when the voltage drops to a value less than a certain voltage value and for disabling the sequence control circuit in response to the warning signal irrespective of the existance of said start signal.

5. A camera according to claim 4 in which said operation means includes a light measuring circuit and the display circuit indicates exposure information on the basis of the output from the light measuring circuit.

6. A digital control circuit for a camera comprising:

(a) a pulse oscillator;

(b) a counting means which counts the pulses derived from the pulse oscillator;

(c) a display circuit for displaying photographic information in response to the counting operation of said counting means;

(d) photographic operation start signal forming means for producing a photographic operation start signal for starting a photographing operation;

(e) a counter setting circuit connected to the counting means for setting the contents of counting means into an initial state in response to the photographing operation start signal;

(f) a shutter release signal forming circuit responsive to the photographing operation start signal and which is connected to the counting means for producing a shutter release signal when the value counted by the counting means reaches a preset value;

(g) a source circuit for coupling to a power source and supplying power to the digital control circuit; and

(h) a warning signal forming circuit which detects the voltage at the power source and which produces a warning signal when the voltage drops to a value less than a certain voltage value, and for holding said shutter release signal forming circuit in a non-operative state in response to a low signal irrespective of the start signal.

7. A digital control circuit according to claim 6, in which said digital control circuit includes gate means for producing a signal when the photographic operation start signal is produced, flip-flop means for producing an output in response to the signal from said gate means, said shutter release signal forming circuit being arranged to become operative in response to the output from said flip-flop means, and said gate means inhibiting production of said signal in response to the warning signal independent of the photographic operation start signal.

8. A digital control circuit according to claim 7 in which the gate means is a NAND gate.