Fade-in and fade-out device of an automatic servomechanism of di

Details Fade-in and fade-out device of an automatic servomechanism of di Fade-in and fade-out device of an automatic servomechanism of di

1977-05-13

1978-11-07

Hayes, Monroe H.

Optics: motion pictures

Special effects

Transition effects

352141, G03B 2136

Patent

active

041242831

ABSTRACT:
A fade-in and fade-out device of an automatic servomechanism for controlling the diaphragm exposure of cinecamera. A differential amplifier having a first input voltage corresponding to the scene light and a second reference input voltage corresponding to the requisite exposure, produces a differential control voltage which is applied to the diaphragm during fade-in or fade-out. The reference input voltage to the differential amplifier is produced by an operation amplifier circuit which includes a resistive voltage divider applied to the non-inverting op-amp terminal, a negative feedback circuit formed by the parallel combination of a diode and a capacitor between the op-amp output and the op-amp inverting input, and a pair of charge and discharge resistors selectively coupled to the inverting op-amp input by means of a switch such that the reference input voltage to the differential amplifier produced at the op-amp output is linearly varied in accordance with the position of the switch, with the exposure at the midpoint of the fading-in equaling the exposure at the mid-point of the fading-out.

REFERENCES:
patent: 3701594 (1972-10-01), Keiner
patent: 3966312 (1976-06-01), Wagensonner et al.
patent: 4006976 (1977-02-01), Ishiguro

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