Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
2002-04-11
2004-04-13
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C250S2140RC
Reexamination Certificate
active
06720544
ABSTRACT:
BACKGROUND
It is often desirable to produce light which is controlled to produce a constant and stabilized output. It may be challenging to control simple semiconductor light sources, such as light emitting diodes (LEDs), using simple circuitry.
SUMMARY
According to the present system, a simple circuit is described which obviates many of these problems. The circuit uses a semiconductor light source and a semiconductor photoreceptor within the feedback loop of a controlled amplifier. The amplifier can be an operational amplifier which uses the light source and photoreceptor within its feedback loop. The photoreceptor senses a level of the illumination light, and the operation of the feedback loop maintains that illumination light constant at a desired level. In an embodiment, the illumination light may be varied according to a digital control.
REFERENCES:
patent: 4577320 (1986-03-01), Yoshikawa et al.
patent: 5097473 (1992-03-01), Taguchi
Barna Sandor L.
Campbell Scott Patrick
Dickstein , Shapiro, Morin & Oshinsky, LLP
Le Que T.
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