Servo-controlled camera diaphragm including a unique dither circuit

Claim 2

An automatic diaphragm control system comprising in an inverse feedback relationship means including a photosensitive element for producing a DC information signal responsive to the light incident on said photosensitive element, a diaphragm positioned in the path of light incident of said photosensitive element, a reversible DC electric motor coupled to said diaphragm to increase and reduce the aperture thereof in accordance with the direction of rotation of said motor, an oscillator, means for combining an AC signal derived from said oscillator with said DC information signal to produce a composite signal, means for rectifying the output of said oscillator to produce a DC voltage source, said information signal-producing means being energized by said DC voltage source, and means responsive to said composite information signal for controlling the rotation and direction of and rotation of said motor and for applying an AC braking current to said motor when said information signal is within a predetermined range.

Claim 3

The system of claim 1 wherein said signal combining said AC signal to said information signal includes signal-combining means includes a capacitor for combining the output of said oscillator with said information signal.

Claim 4

The system of claim 1 wherein said information signal-producing means includes means for selectively adjusting the value of said information signal independently of said photosensitive element.

Claim 5

An automatic diaphragm control arrangement comprising an information signal output section (14) under control of a photoconductor (1) serving as an object brightness-sensing element and a resistor (13) to be adjusted in accordance with photographing Condition other than object brightness, a DC-DC converter (7) serving as the current source for said output section, a circuit (11) for superposing the AC voltage of said converter on the information signal of said output section, a control section (16) which controls the normal and reversed rotation and stoppage of the servomotor (19) in a switching manner through connection of an output transistor section, which is connected to a switching operation-amplifying section (15) to which is applied the information signal, with another output transistor section (20) of the same type, and an incident light control section (23) for said photoconductor which performs its incident light control operation through drive by said servomotor and in response to an exposure-setting operation through drive by said motor.

Claim 6

An automatic diaphragm control arrangement comprising an information signal output section (14) under control of a photoconductor (1) serving as an object brightness-sensing element and a resistor (13) to be adjusted in accordance with photographing Condition other than object brightness, a DC-DC converter (7) serving as the current source for said output section, a circuit (11) for superposing the AC voltage of said converter on the information signal of said output section, a control section (16) which controls the normal and reversed rotation and stoppage of the servomotor (19) in a switching manner through connection of an output transistor section, which is connected to a switching operation-amplifying section (15) to which is applied the information signal, with another output transistor section (20) of the same type, and an incident light control section (23) for said photoconductor which performs its incident light control operation through drive by said servomotor and in response to an exposure-setting operation through drive by said motor.