Automatic focusing device for slide projectors

Details Automatic focusing device for slide projectors Automatic focusing device for slide projectors

1983-02-24

1985-01-22

Haroian, Harry N.

Optics: image projectors

Lens support

Lens position adjustable

G03B 310

Patent

active

044948395

ABSTRACT:
An automatic focusing device for slide projectors in which at least one photo-electric receiver of the secondary projection device which determines the position of the slide generates, from a beam of light impinging upon the receiver, the error voltage controlling the focusing of the slide. The error voltage is fed into an electronic amplifier circuit of the focusing device, which contains manual facilities for refocusing the slide comprising primary switching elements which automatically apply the error voltage produced by the photoelectric receiver to the positioning motor for the focusing device, but only when this error voltage reaches a predetermined level. In addition, the device contains secondary switching elements which cut off the amplifier circuit from the positioning motor when the manual facilities for focus adjustment are operated, and which connect the focus adjustment means to the positioning motor and adjust the positioning motor to run at a constant speed via a combination (group) of resistors.

REFERENCES:
patent: 3628863 (1971-12-01), Kottler
patent: 3861794 (1975-01-01), Sobotta

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