Sony Corporation

Tadashi Esashika

Ryuji Shiono

Apparatus is provided for automatically controlling or locking the iris aperture of a camera. The brightness level of a signal produced by the camera is detected and an automatic control circuit responds to this detected brightness level to energize an iris drive, thereby establishing the iris aperture. The actual size of that aperture is represented by an aperture signal. This aperture signal is used by a control signal generator to generate a control signal corresponding thereto. A selecting circuit is operable to select either an automatic control mode wherein the iris drive is energized by the detected brightness level of the signal produced by the camera, or an iris lock mode wherein the iris drive is energized to maintain the iris aperture at a fixed size irrespective of changes in that brightness level. An iris lock circuit responds to the selection of the iris lock mode for storing the control signal which is generated just prior to the selection of the iris lock mode, and compares the stored control signal to the aperture signal that is produced during the iris lock mode to energize the iris drive as a function of the difference therebetween. In the iris lock mode the automatic control circuitry is disabled. The iris aperture thus is fixed at a size determined by the stored control signal.

Apparatus for locking the iris aperture of a camera

An aperture correction signal processing circuit includes first and second differential amplifiers, each consisting of first and second transistors. The respective first transistors of the first and second differential amplifiers are applied at respective base electrodes thereof with first and second aperture correction signals, which are opposite in phase to each other, while the base electrodes of the respective second transistors of the first and second differential amplifiers are connected to each other and fed with a variable bias voltage. The common electrodes of the first and second transistors of the first differential amplifier are connected to each other and further to a variable constant-current source, while the common electrodes of the first and second transistors of the second differential amplifier are connected to each other and further to a variable constant-current source, both of the above sources being simultaneously controllable. Thus, output signals from the first and second differential amplifiers are fed to the base electrode of a transistor for being added together to obtain an aperture correction signal free from noise at its emitter electrode.

Growing community of inventors

Atsugi, Japan

Tadashi Esashika