An exposure control system for a photographic system

Claim 2

An exposure control apparatus for a photographic camera having an objective lens system, comprising diaphragm means mounted to form an aperture in the objective lens system, a Wheatstone bridge having four branches, photosensitive means on one of said branches for receiving light from an object to be photographed, three resistor means each in the other of said branches, at least one of said resistor means correcting for an exposure factor, a differential amplifier circuit including at least one pair of transistors of the same polarity, said Wheatstone bridge having an output, said transistors each having an input electrode connected with the output of said Wheatstone bridge, a driving circuit connected with the output of said differential amplifier circuit for producing a current that responds to the output of said differential amplifier circuit, an electromagnetic device electrically coupled to the output of said output circuit and connected with said diaphragm means for varying the opening of said diaphragm means, said electromagnetic device being coupled to at least one of said branches in said Wheatstone bridge for adjusting the bridge so that the bridge assumes a balanced condition, damping coil means in said electromagnetic device, coupling means for coupling said damping coil to said input electrodes of said transistors for preventing said diaphragm means from producing irregular responses.

Claim 3

A photographic apparatus as in claim 1, further comprising indicator means actuated in response to the quantity of light received by the photosensitive element.

Claim 4

A photographic apparatus according to claim 1, wherein said differential amplifier includes a power source, said comparator having a voltage different from that of the power source but derived from said power source.

Claim 5

An exposure control system for a camera having an objective lens system, comprising diaphragm means mounted to form an aperture in said objective lens system, a comparator circuit including photosensitive means and three resistor means connected to form a Wheatstone bridge, said comparator circuit having output terminals, diaphragm adjusting means operatively connected with said diaphragm means for adjusting said diaphragm means, a differential amplifier circuit including at least a pair of transistors of the same polarity connected to the output terminals of said comparator circuit and an output circuit, said transistors having respective input electrodes, said output circuit including an electromagnetic device coupled to said diaphragm adjusting means for actuating said diaphragm adjusting means, said output circuit producing an output value corresponding to a quantity of light received by said photosensitive element, damper means including a damping coil magnetically interlinked with said electromagnetic device, and coupling means for coupling said damping coil to said input electrodes of said transistors in order to prevent irregular responses, said diaphragm adjusting means being actuated by said electromagnetic device under the control of said damping coil.

Claim 6

An exposure control system for a camera having an objective lens system, comprising diaphragm means mounted to form an aperture in said objective lens system, a comparator circuit including photosensitive means and three resistor means connected to form a Wheatstone bridge, said comparator circuit having output terminals, diaphragm adjusting means operatively connected with said diaphragm means for adjusting said diaphragm means, a differential amplifier circuit including at least a pair of transistors of the same polarity connected to the output terminals of said comparator circuit and an output circuit, said transistors having respective input electrodes, said output circuit including an electromagnetic device coupled to said diaphragm adjusting means for actuating said diaphragm adjusting means, said output circuit producing an output value corresponding to a quantity of light received by said photosensitive element, damper means including a damping coil magnetically interlinked with said electromagnetic device, and coupling means for coupling said damping coil to said input electrodes of said transistors in order to prevent irregular responses, said diaphragm adjusting means being actuated by said electromagnetic device under the control of said damping coil.

Claim 7

A photographic apparatus according to claim 4, wherein the photosensitive element is disposed behind the objective lens system of the camera.

Claim 8

A photographic apparatus as in claim 4, in which the output circuit comprises a second Wheatstone bridge having bipolar characteristicS, each branch of said other Wheatstone bridge having an amplifier so that said other bridge may function in response to an input to each of said amplifiers connected to the differential amplifier circuit.

Claim 9

A photographic apparatus as in claim 4, wherein said photosensitive element is located outside of the path of light passing through said diaphragm means, and wherein connector means connect the output of said output circuit to one of said resistor means for adjusting the resistor means in response to the output of said output circuit so as to vary the balance of said comparator circuit.

Claim 10

A photographic exposure control system for a camera with an objective lens, comprising diaphragm means mounted to form a aperture in said objective lens, photosensitive means located outside of the path of light passing through said diaphragm means, variable means forming with said photosensitive means a sensing ciruicit having a pair of transistors of the same conductive type which produce a signal indicative of the light to which said photosensitive means is exposed, said transistors having respective bases control circuit means responsive to said signal, said control circuit means for adjusting said diaphragm means, coupling means for coupling said control circuit means to said variable means for varying the output of said sensing cirucit in response to the output of said control cirucit means and thereby reduce the output of said sensing circuit as the adjustment of said diaphragm means comes closer to that determined by said photosensitive means, magnetic means electrically coupled to the output of said control means for generating a magnetic flux in accordance with the output of the control circuit means, and a damping coil coupled to said magnetic means, and coupling means for coupling said damping coil to said bases of said transistors for preventing irregular responses from said sensing means, said diaphragm means being actuated by said control circuit means under the control of said damping coil.

Claim 11

A photographic exposure control system for a camera with an objective lens, comprising diaphragm means mounted to form a aperture in said objective lens, photosensitive means located outside of the path of light passing through said diaphragm means, variable means forming with said photosensitive means a sensing ciruicit having a pair of transistors of the same conductive type which produce a signal indicative of the light to which said photosensitive means is exposed, said transistors having respective bases control circuit means responsive to said signal, said control circuit means for adjusting said diaphragm means, coupling means for coupling said control circuit means to said variable means for varying the output of said sensing cirucit in response to the output of said control cirucit means and thereby reduce the output of said sensing circuit as the adjustment of said diaphragm means comes closer to that determined by said photosensitive means, magnetic means electrically coupled to the output of said control means for generating a magnetic flux in accordance with the output of the control circuit means, and a damping coil coupled to said magnetic means, and coupling means for coupling said damping coil to said bases of said transistors for preventing irregular responses from said sensing means, said diaphragm means being actuated by said control circuit means under the control of said damping coil.