US 5,471,052 AGranted

Color sensor system using a secondary light receiver

AssigneeEaton Corporation

InventorLawrence J. Ryczek

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Abstract

A system for photoelectrically sensing the color of an object includes two or more light sources having different characteristic ranges of chromaticity and one primary photosensitive element which receives light from the light sources after it has reflected off of the target object and a secondary photosensitive element which receives light from the light sources prior to reflection off of the target. A divider element divides the output of the primary photosensitive element by the output of the secondary photosensitive element to automatically align the signal representative of the color of the object for variation in the light power output of the light sources. In an alternate embodiment, the output of the secondary photosensitive receiver is used as a closed loop feedback signal to regulate the light power output of the light sources.

A photoelectric color sensor comprising:

at least two light sources disposed in a fixed array directed toward an optical transmission device having a primary path for transmitting light from said light sources to an object whose color is to be measured and a secondary path, each of said light sources operable to generate emitted light having a limited characteristic range of chromaticity differing from the characterization range of chromaticity of each other light source;
a primary photosensitive receiver positioned to receive said emitted light reflected from an object whose color is to be measured;
a secondary photosensitive receiver positioned to receive a portion of said emitted light transmitted from said light sources through said secondary path;
said secondary photosensitive receiver generating an output signal representing the level of said emitted light;
a control circuit connected between said secondary photosensitive receiver and said light sources for controlling the light energy emitted by said light sources, said control conduit having a level comparator electrically connected to said secondary photosensitive receiver for comparing said output signal to a reference level and controlling a current driver for powering said light sources to produce a level of emitted light according to said reference level
logic means in circuit with said light sources and said primary photosensitive receiver operative to sequentially energize said light sources and to receive resultant sample signals from said primary photosensitive receiver in response to each said light source energization, said logic means being further operative to generate a resultant signal as a function of said sample signals, to compare said resultant signal with a predetermined reference standard and generate a condition output signal when the difference between said resultant signal and reference standard exceeds a tolerance limit, wherein said reference standard has been established during an earlier test mode operation of said logic means in which a standard color mode operation of said logic means in which sensing region and sequentially illuminated by said light sources, said reference standard and said resultant signal comprising a respective single signal for each said characteristic range of chromaticity.

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Abstract

Claims18