Exposure controlling device for a camera

Claim 2

An exposure control device for a camera having an adjustable iris, comprising capacitor means, charging means connectable to said capacitor means for charging said capacitor means to a predetermined value, discharging means connectable to said capacitor means and including A photoresistive device responsive to light through the iris for discharging said capacitor means at a rate depending on the light through the iris, time controlled switching means for connecting said capacitor means to said charging means and thereafter disconnecting said charging means from said capacitor means and connecting said discharging means to said capacitor means over a predetermined time period before disconnecting said discharging means so as to discharge said capacitor means for a predetermined time period so that the remaining charge on said capacitor means represents a measure of the ambient light, and means for utilizing the remaining charge on said capacitor means for controlling exposure.

Claim 3

An exposure control device as in claim 1, wherein the camera includes an electronic shutter and wherein said means for utilizing the charge includes resistive means connectable to said capacitor means for discharging the remaining charge on said capacitor means and a switching arrangement responsive to the voltage across said resistive means reaching a predetermined potential for controlling said shutter.

Claim 4

An exposure control device for a single lens reflex camera having a lens, a shutter, shutter opening means and shutter closing means, comprising a photoconductive cell positioned in the camera to receive light passing through the lens, charging means for supplying charge to the capacitor and having switching means for connecting said charging means to said capacitor, said switching means selectively connecting said photoconductive cell in parallel with said capacitor while disconnecting said charging means to predischarge said capacitor on the basis of light on said photoconductive cell, discharging means having an impedance member connected by said switching means in parallel with said capacitor in timed relation with said means for opening the shutter, a switching circuit having an input connected by said switching means to be in parallel with the capacitor and an output coupled to the shutter closing means for responding to the voltage across said capacitor reaching a predetermined level and closing the shutter in response thereto.

Claim 5

An exposure control device for a single lens reflex camera having a lens, a shutter, shutter opening means and shutter closing means, comprising a photoconductive cell positioned in the camera to receive light passing through the lens, charging means for supplying charge to the capacitor and having switching means for connecting said charging means to said capacitor, said switching means selectively connecting said photoconductive cell in parallel with said capacitor while disconnecting said charging means to predischarge said capacitor on the basis of light on said photoconductive cell, discharging means having an impedance member connected by said switching means in parallel with said capacitor in timed relation with said means for opening the shutter, a switching circuit having an input connected by said switching means to be in parallel with the capacitor and an output coupled to the shutter closing means for responding to the voltage across said capacitor reaching a predetermined level and closing the shutter in response thereto.

Claim 6

An apparatus as in claim 3, wherein said switching means includes means for keeping said photoconductive cell connected in parallel with said capacitor for a predetermined time period.

Claim 7

An apparatus as in claim 3, wherein said switching means includes an R-C time constant circuit and a second switching circuit, said second switching circuit connecting said capacitor in parallel with said photoconductive cell for a time dependent upon said R-C time constant circuit.

Claim 8

An apparatus as in claim 3, wherein said switching means includes first and second switching elements, said first switching element selectively connecting said capacitor to said charging means, said photoconductive cell and said input to said switching circuit, said second switching element including time constant means and connecting said time constant means to the input of said switching circuit when said capacitor is connected by said first switching element to the photoconductive cell.