Light metering systems and exposure control systems for cameras

Claim 2

A light metering system comprising: photoelectric means for producing a first analog signal which represents the intensity of light incident thereon; a reversible counter; converter means for producing a second analog signal which represents the count stored in said counter; and counter control means for stepping said counter in a first direction when the difference between the first and second analog signals is greater than a predetermined value and for stepping said counter in the opposite direction when said difference is less than said predetermined value.

Claim 3

A light metering system as set forth in claim 1, wherein said counter control means comprises comparator means for comparing said first and second analog signals, said comparator means producing a first output signal when said difference between the first and second analog signals is greater than said predetermined value and producing a second output signal when said difference is less than said predetermined value, and means for stepping said counter in said first direction in response to said first output signal and for stepping said counter in said opposite direction in response to said second output signal.

Claim 4

A light metering system as set forth in claim 2, wherein said reversible counter comprises a pulse counter having first and second input terminals to which pulses may be applied for stepping the counter in said first and opposite directions, respectively, and wherein the last-mentioned means comprises means for applying pulses to one of said first and second input terminals in response to said first output signal and for applying said pulses to the other of said input terminals in response to said second output signal.

Claim 5

A light metering system as set forth in claim 3, wherein said means for applying pulses comprises a pulse generator for generating said pulses and first and second gate means responsive to said first and second output signals, respectively, for applying said pulses to said one and said other input terminals, respectively, of said pulse counter.

Claim 6

A light metering system as set forth in claim 3, wherein said means for applying pulses comprises first and second pulse generators responsive to said first and second output signals, respectively, for applying pulses to said one and said other input terminals, respectively, of said pulse counter.

Claim 7

A light metering system as set forth in claim 3, wherein said comparator means comprises a differential amplifier having first and second output terminals for providing said first and second output signals, respectively.

Claim 8

A light metering system as set forth in claim 3, wherein said comparator means comprises a differential amplifier having an output terminal for providing said first output signal of the comparator means and an inverter having its input connected to said output terminal so that the output of said inverter provides said second output signal of the comparator means.

Claim 9

A light metering system as set forth in claim 1, wherein said coNverter means comprises a plurality of weighted resistors corresponding to respective counting stages of said counter, each of said resistors being adapted to conduct current in response to a particular condition of its corresponding counting stage.

Claim 10

A light metering system in accordance with claim 1, further comprising a plurality of digital display elements and means for actuating the display elements in accordance with the count in said counter.

Claim 11

An automatic exposure control system comprising: photoelectric means for producing a first analog signal which represents the brightness of an object to be photographed; a reversible counter; converter means for producing a second analog signal which represents the count in said counter; counter control means for stepping said counter in a first direction when the difference between the first and second analog signals is greater than a predetermined value and for stepping said counter in the opposite direction when the difference between the analog signals is less than said predetermined value; and exposure control means for controlling exposure of film in a camera in accordance with the count in said counter.

Claim 12

An automatic exposure control system comprising: photoelectric means for producing a first analog signal which represents the brightness of an object to be photographed; a reversible counter; converter means for producing a second analog signal which represents the count in said counter; counter control means for stepping said counter in a first direction when the difference between the first and second analog signals is greater than a predetermined value and for stepping said counter in the opposite direction when the difference between the analog signals is less than said predetermined value; and exposure control means for controlling exposure of film in a camera in accordance with the count in said counter.

Claim 13

An exposure control system as set forth in claim 10, wherein said counter control means comprises comparator means for comparing said first and second analog signals, said comparator means producing a first control signal when the difference between the first and second analog signals is greater than said predetermined value and producing a second control signal when said difference is less than said predetermined value and means for stepping said counter in said first direction in response to said first control signal and for stepping said counter in said opposite direction in response to said second control signal.

Claim 14

An exposure control system as set forth in claim 11, wherein said reversible counter comprises a pulse counter having first and second input terminals to which pulses may be applied for stepping the counter in said first and opposite directions, respectively, and wherein the last-mentioned means comprises means for applying pulses to one of said first and second input terminals in response to said first output signal and for applying said pulses to the other of said input terminalso in response to said second output signal.

Claim 15

An exposure control system as set forth in claim 12, wherein said means for applying pulses comprises a pulse generator for generating said pulses and first and second gate means responsive to said first and second output signals, respectively, for applying said pulses to said one and said other input terminals, respectively, of the pulse counter.

Claim 16

An exposure control system as set forth in claim 11, wherein said means for applying pulses comprises first and second pulse generators responsive to said first and second output signals, respectively, for applying said pulses to said one and said other input terminals, respectively, of said counter.

Claim 17

An exposure control system as set forth in claim 12, wherein said comparator means comprises a differential amplifier having first and second output terminals for providing said first and second output signals, respectively.

Claim 18

An exposure control system as set forth in claim 12, wherein said comparator means comprises a differential amplifier having an output terminal for providing said first output signal of the comparator means and an inverter having its input connected to said first output terminal so that the output of said inverter provides said second output signal of the comparator means.

Claim 19

An exposure control system as set forth in claim 11, wherein said converter means comprises a plurality of weighted resistors corresponding to respective counting stages of said pulse counter, each of said resistors being adapted to conduct current in response to a particular condition of its corresponding counting stage.

Claim 20

An exposure control system in accordance with claim 10, further comprising a plurality of digital display elements and means for actuating the display elements in accordance with the count in said counter.

Claim 21

An exposure control system as set forth in claim 10, wherein said exposure control means comprises shutter control means for controlling the exposure time of the camera.

Claim 22

An exposure control system as set forth in claim 19, wherein said shutter control means comprises means for interrupting stepping of said counter by said counter control means in response to actuation of the shutter opening mechanism of the camera, means for stepping the counter in one of said first and opposite directions after said interruption, and means for preventing the shutter from closing until said counter has been stepped thereby to a predetermined count.

Claim 23

An exposure control system as set forth in claim 20, wherein said counter comprises a pulse counter, and wherein said means for stepping said pulse counter after said interruption comprises a pulse generator and a switch responsive to opening of the shutter for applying pulses generated by said pulse generator to said counter, and wherein said means for preventing the shutter from closing comprises an electromagnet for holding the shutter open when the electromagnet is energized and gate means for energizing the electromagnet until said pulse counter reaches said predetermined count.

Claim 24

A light metering system as set forth in claim 19, wherein said shutter control means comprises: means for producing a current proportional to the intensity of light incident on said photoelectric means; a capacitor; switch means for initiating charging of said capacitor by said current in response to actuation of the shutter opening mechanism of the camera; and means for preventing the shutter from closing until the voltage on said capacitor reaches a predetermined voltage.

Claim 25

A light metering system as set forth in claim 22, wherein the last-mentioned means comprises an electromagnet for holding the shutter in open position when the electromagnet is energized, and detector means for de-energizing said electromagnet when the voltage across said capacitor reaches said predetermined value.