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Constant output light emitting device

  • US 4,182,977 A
  • Filed: 06/01/1978
  • Issued: 01/08/1980
  • Est. Priority Date: 06/01/1978
  • Status: Expired due to Term
First Claim
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1. A light emitting device to be used in conjunction with a power supply, comprising in combination:

  • a light emitter for emitting light when supplied with electric current, wherein an increase in electric current supplied to the light emitter increases the output light intensity;

    a compensating circuit comprising an integrated circuit powered by the power supply, electrically connected to the light emitter for supplying current to the light emitter, the compensating circuit including a light sensor in proximity to and substantially to the side of the light emitter wherein the compensating circuit is responsive to the light intensity sensed by the light sensor, increasing the current supplied to the light emitter as the intensity of the light sensed decreases;

    means for electrically connecting the compensating circuit to the power supply;

    a substantially clear overcoat substantially covering the light emitting surface of the light emitter wherein part of the light emitted from the light emitter is transmitted through the overcoat and part of the light emitted is reflected by the overcoat to the light sensor, whereby the intensity of light transmitted through the overcoat when the light emitting device is on remains substantially constant over the useful life of the light emitter; and

    a header for mounting electrical components, wherein the light emitter and the compensating circuit are mounted on the header;

    wherein the header forms a recess for mounting the light emitter, and the light emitter is mounted on the header in the recess, and wherein the substantially clear overcoat substantially covers both the light sensor and the light emitting surface of the light emitter.

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