Automatic exposure control systems and light metering systems for cameras

Claim 2

An automatic exposure control system for a camera, the system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means; means for passing a current proportional to the intensity of light incident on said light responsive means through a circuit including said variable resistance means and said light responsive means connected in series; count control means for adjusting the count in said counter means to maintain the voltage at a point at which said variable resistance means and said light responsive means are connected at a predetermined voltage level; and exposure control means for controlling the exposure of film in said camera in accordance with said count.

Claim 3

An exposure control system as set forth in claim 1, further comprising means for enabling adjustment of said predetermined voltage level in accordance with the adjustment of exposure factors, such as film speed.

Claim 4

An automatic exposure control system for a camera, the system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means connected in circuit with said variable resistance means for varying the voltage at a point in said circuit in accordance with the intensity of light incident on said light responsive means; count control means for adjusting the count in said counter means to maintain the voltage at said point at a predetermined voltage level; and exposure control means for controlling the exposure of film in said camera in accordance with said count; said counter means comprising a reversible counter, and said count control means comprising means for stepping the counter in a first direction when the voltage at said point is below said predetermined voltage level and for stepping the counter in the opposite direction when the voltage at said point is above said predetermined voltage level.

Claim 5

An automatic exposure control system for a camera, the system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means connected in circuit with said variable resistance means for varying the voltage at a point in said circuit in accordance with the intensity of light incident on said light responsive means; count control means for adjusting the count in said counter means to maintain the voltage at said point at a predetermined voltage level; and exposure control means for controlling the exposure of film in said camera in accordance with said count; said counter means comprising a reversible counter, and said count control means comprising means for stepping the counter in a first direction when the voltage at said point is below said predetermined voltage level and for stepping the counter in the opposite direction when the voltage at said point is above said predetermined voltage level.

Claim 6

An exposure control system as set forth in claim 3, wherein said reversible counter comprises a pulse counter having first and second input terminals to which pulses may be applied for stepping said pulse counter in said first and opposite directions, respectively, and wherein the last-mentioned means comprises comparator means for producing first and second output signals when the voltage at said point is respectively above and below said predetermined level and means responsive to said first and second output signals for applying pulses to said first and second input terminals, respectively, of said pulse counter.

Claim 7

An exposure control system as set forth in claim 4, wherein said comparator means has first and second input terminals connected to said point and to means for establishing said predetermined voltage level, respectively, and wherein said light responsive means comprises a photovoltaic device connected between said first and second input terminals.

Claim 8

An exposure control system as set forth in claim 1, wherein said variable resistance means comprises a plurality of weighted resistors corresponding to respective counting stages of said counter means, each of the resistors being adapted to conduct current in response to a particular condition of the corresponding counting stage of said counter means.

Claim 9

An exposure control system as set forth in claim 1, further comprising digital indicator means for displaying information relating to the count in said counter means.

Claim 10

An exposure control system as set forth in claim 1, further comprising means for interrupting adjustment of the count by said count control means in response to actuation of the shutter release mechanism of the camera.

Claim 11

An exposure control system as set forth in claim 1, wherein the exposure control means comprises shutter control means for controlling the exposure time of the camera in accordance with the resistance of said variable resistance means.

Claim 12

An exposure control system as set forth in claim 9, wherein said shutter control means comprises: a capacitor; switch means for connecting said variable resistance means and said capacitor in series in response to actuation of the shutter release mechanism of the camera; an electromagnet for holding the shutter open when the electromagnet is energized and for permitting the shutter to close when the electromagnet is de-energized; and means for de-energizing said electromagnet when the voltage across said capacitor reaches a predetermined voltage.

Claim 13

An exposure control system as set forth in claim 1, wherein said light responsive means comprises a photoconductive cell.

Claim 14

An automatic light metering system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means; means for passing a current porportional to the intensity of light incident on said light responsive means through a circuit including said variable resistance means and said light responsive means connected in series; and control means for adjusting the count in said counter means to maintain the voltage at a point at which said variable resistance means and said light responsive means are connected at a predetermined voltage level.

Claim 15

An automatic light metering system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means; means for passing a current porportional to the intensity of light incident on said light responsive means through a circuit including said variable resistance means and said light responsive means connected in series; and control means for adjusting the count in said counter means to maintain the voltage at a point at which said variable resistance means and said light responsive means are connected at a predetermined voltage level.

Claim 16

A light metering system as set forth in claim 12, further comprising means for enabling adjustment of said predetermined voltage level in accordance with the adjustment of exposure factors, such as film speed.

Claim 17

An automatic light metering system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means connected in circuit with said variable resistance means for varying the voltage at a point in said circuit in accordance with the intensity of light incident on said light responsive means; and control means for adjusting the count in said counter means to maintain the voltage at said point at a predetermined voltage level; said counter means comprising a reversible counter, and said control means comprising means for stepping said counter in a first direction when the voltage at said point is below said predeterminEd voltage level and for stepping said counter in the opposite direction when the voltage at said point is above said predetermined voltage level.

Claim 18

An automatic light metering system comprising: counter means; variable resistance means having a resistance which varies in accordance with the count in said counter means; light responsive means connected in circuit with said variable resistance means for varying the voltage at a point in said circuit in accordance with the intensity of light incident on said light responsive means; and control means for adjusting the count in said counter means to maintain the voltage at said point at a predetermined voltage level; said counter means comprising a reversible counter, and said control means comprising means for stepping said counter in a first direction when the voltage at said point is below said predeterminEd voltage level and for stepping said counter in the opposite direction when the voltage at said point is above said predetermined voltage level.

Claim 19

A light metering system as set forth in claim 14, wherein said reversible counter comprises a pulse counter having first and second inputs to which pulses may be applied for stepping said pulse counter in said first and opposite directions, respectively, and wherein the last-mentioned means comprises comparator means for producing first and second output signals when the voltage at said point is respectively above and below said predetermined voltage level and means responsive to said first and second output signals for applying pulses to said first and second input terminals, respectively, of said pulse counter.

Claim 20

A light metering system as set forth in claim 15, wherein said comparator means has first and second input terminals connected to said point and to means for establishing said predetermined voltage level, respectively, and wherein said light responsive means comprises a photovoltaic device connected between said first and second input terminals of said comparator means.

Claim 21

A light metering system as set forth in claim 12, wherein said variable resistance means comprises a plurality of weighted resistors corresponding to respective counting stages of said counter means, each of the resistors being adapted to conduct current in response to a particular condition of the corresponding counting stage of said counter means.

Claim 22

A light metering system as set forth in claim 12, further comprising digital indicator means for displaying information relating to the count in said counter means.

Claim 23

A light metering system as set forth in claim 12, wherein said light responsive means comprises a photoconductive cell.

Claim 24

A light metering system as set forth in claim 12, wherein said control means comprises means for adjusting the count in said counter means to vary said variable resistance means in inverse proportion to the intensity of the light incident on said light responsive means.

Claim 25

A light metering system as set forth in claim 20, wherein said current passing means comprises a source of voltage connected across said variable resistance means and said light responsive means in series.

Claim 26

A light metering system as set forth in claim 21, wherein said control means comprises means for comparing the voltage at said point with a reference voltage.