Controlling lens focal length of slave TV camera - using voltage to frequency conversion of focal length-dependent voltage signal from main camera

摘要

The principal application of the control system is for simultaneous recording of a studio subject and a different live background picture. To maintain compatibility of the two pictures it is desirable, when using zoom lenses, that both cameras operate with identical settings for the lenses. The studio camera acts as master and is under the control of a camera man. A transducer fitted to the zoom appts. produces a d.c. voltage proportional to the set focal length of the camera lens. A converter changes the voltage level into an alternating signal whose frequency is proportional to the d.c. voltage. After transmission to the slave camera the frequency is reconverted into a proportional d.c. voltage which, in turn, acts as reference for the lens setting drive. Digital signals may be employed instead of frequency.