Exposure control system

• US 4,420,237 A
• Filed: 12/17/1982
• Issued: 12/13/1983
• Est. Priority Date: 02/13/1979
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ogawa, Yukio, Yamada, Tateo, Harigaya, Isao, Hirohata, Michio
• Primary Examiner(s): Gellner, Michael L.
• Application Number:
  US06/450,745
• Time in Patent Office: 361 Days
• Field of Search: 354/23 D, 354/29, 354/30, 354/42, 354/49, 354/59, 354/60 R, 354/209
• US Class Current: 396/242
• CPC Class Codes: G03B 7/081 Analogue circuits
• CPC Class Codes: G03B 7/093 for control of exposure time

Abstract

A camera having an electromagnetically driven shutter provided with a counter capable upon counting a present number producing a signal. Each time the shutter is closed, the counted value is changed, while the period of actuation of the shutter is controlled to effect a predetermined fraction of an exposure, so that a continuous sequence of shots equal in number to that preset in the counter are taken automatically.

Claims

1. An exposure control system including:

(a) electromagnetically operated shutter means operating under the action of an electromagnetic force and positioned to block and unblock light entering a photo-taking lens;

(b) a shutter drive circuit responsive to an actuating signal for opening, and, after a predetermined time, closing said electromagnetically operated shutter;

(c) means for setting a number of exposures;

(d) a counter or counting each time said electromagnetically operated shutter means is closed after a an actuating signal and for producing a closing signal upon having counted the predetermined number set by the exposure number setting means;

(e) a flip-flop circuit for holding said shutter drive circuit in an operative position from the time of the actuating signal to that at which said counter produces the predetermined signal; and

(f) a timer circuit for preventing actuation of said shutter drive circuit from the initiation of a closing of said electromagnetically operated shutter to the termination of the closing thereof.

2. An exposure control system according to claim 1, further comprising setting means for optionally selecting distribution of the exposure amount for each of the multiple exposures.

3. An exposure control system according to claim 2, further comprising a release switch for closing in response to the camera release to supply power to the circuits, and means for holding a power source, said holding means maintaining the power supply condition until the set number of exposures is finished after the release switch opens.

4. An exposure control system according to claim 1, further comprising means for indicating the number of exposures set by the exposure number setting means.

5. An exposure control system according to claim 4, wherein the indicating means serves for indicating the remaining number of exposures.

6. A system as in claims 1, 3, 4 or 5, wherein the number of exposures set is equal to N, and wherein said shutter drive circuit includes means responsive to the object brightness for establishing a time T suitable for one full exposure to close the electromagnetically operated shutter and for closing the shutter following an opening after a time T/N.

7. An exposure control system according to claim 1, wherein said electromagnetically operated shutter means is associated with diaphragm means.

8. An exposure control system according to claim 7, further including auxiliary diaphragm means for changing the amount of incident light therethrough in response to movement of at least one shutter blade of said electromagnetically operated shutter, and means for sensing the amount of light through said auxiliary diaphragm means.

9. An exposure control system according to claim 8, further comprising means for controlling the time from the moment at which said shutter drive means has driven the electromagnetically operated shutter to open to the moment at which said shutter is to be closed is controlled so that the amount of light incident through said auxiliary diaphragm means is made constant.

10. An exposure control system according to claim 7, further including means for sensing the brightness of an object to be photographed, and where the period of actuation of said shutter drive circuit from opening to closing of the electromagnetically operated shutter is determined by sid object brightness sensed.

11. An exposure control system according to claim 1, wherein said counter produces a signal when a predetermined number has been counted to add or to subtract, whereby said signal cuases the film to be able to advance one frame.

12. An exposure control system according to claim 11, wherein said electromagnetically operated shutter also serves as diaphragm means, and further including auxiliary diaphragm means for varying the amount of light passing therethrough in response to movement of at least one shutter blade of said shutter means, and means for sensing the amount of incident light passing through said auxiliary diaphragm means.

13. An exposure control system according to claim 12, wherein the time from the moment at which said shutter drive means has driven the electromagnetically operated shutter means to open to the moment at which said shutter means is caused to be closed is adjusted so that the amount of incident light passing through said auxiliary diaphragm means is made constant, and the multiplication of this incident light amount by the predetermined number for said counter corresponds to a proper exposure value.

14. An exposure control system according to claim 1, further including a display device connected through a decoder to the output of the counter.

15. An exposure control system according to claim 1, wherein the period of actuation of said timer circuit is variable.

16. An exposure control system operating in response to a release switch and the brightness of an object, comprising:

(a) electromagnetically operated shutter means for operating in response to the action of an electromagnetic force as the driving source and positioned to block and unblock light entering through a photo-taking lens;

(b) a shutter drive circuit for opening, and, after a predetermined time based on the brightness of the object causing said electromagnetically operated shutter to be closed;

(c) a counter for counting each time said electromagnetically operated shutter means is closed after the release switch has been thrown and, upon having counted a predetermined number, producing a predetermined signal;

(d) a timer circuit for intermittently actuating the shutter drive circuit, said timer circuit being arranged for preventing the actuation of the shutter drive circuit for a given time from initiation to finish of closure of the electromagnetically operated shutter means and for actuating the shutter drive circuit in an operative position;

(e) a gate circuit for sustaining said shutter drive circuit in an operative position for a time from the throwing of the release switch to the release thereof; and

(f) maintaining means for maintaining power to the exposure control system from the time of the release switch being thrown to the time the counter produces the predetermined signal.

17. An exposure control system according to claim 16, wherein said electromagnetically operated shutter means is associated with diaphragm means.

18. An exposure control system according to claim 17, further including auxiliary diaphragm means for changing incident light amount in response to movement of at least one shutter blade of said electromagnetically operated shutter, and means for sensing the amount of light passing through said auxiliary diaphragm means.

19. An exposure control system according to claim 18, wherein the time from the moment at which said shutter drive means has driven the electromagnetically operated shutter to open to the moment at which said shutter is to be closed is controlled so that the amount of light incident through said auxiliary diaphragm means is made constant.

20. An exposure control system according to claim 17, further including means for sensing the brightness of an object to be photographed, and for determining where the period of actuation of said shutter drive circuit from opening to closing of the electromagnetically operated shutter means on the basis of the brightness sensed.

21. An exposure control system according to claim 16, wherein said counter produces a signal when a predetermined number has been counted to add or to subtract, whereby said signal causes the film to advance one frame.

22. An exposure control system according to claim 21, wherein said electromagnetically operated shutter also serves as diaphragm means, and further including auxiliary diaphragm means for varying the amount of light passing therethrough in response to movement of at least one shutter blade of said shutter means, and means for sensing the amount of incident light passing through said auxiliary diaphragm means.

23. An exposure control system according to claim 22, further comprising means for controlling the time from the moment at which said shutter drive means has driven the electromagnetically operated shutter means to open to the moment at which said shutter means is to be closed is adjusted so that the amount of incident light entering through said auxiliary diaphragm means is made constant, and means for multiplying the amount of incident light by the predetermined number in said counter corresponding to a proper exposure value.

24. An exposure control system according to claim 16, further including a display device connected through a decoder to the output of said counter.

25. An exposure control system according to claim 16, further comprising:

a long-time timer circuit which releases the maintaining of power to the exposure control system by the maintaining means with its output a predetermined time after the time of the actuating signal.