Light reflection defect detection apparatus and method using pulsed light-emitting semiconductor devices of different wavelengths

A method of detecting defects in articles, comprising the steps of:

• emitting light of at least three different wavelengths, including visible light, each wavelength being emitted from different light-emitting devices;
• pulsing said devices on and off with electrical pulses having an on/off duty cycle of much less than 50% so that each of said devices is pulsed off for a period many times greater than it is pulsed on;
• directing light beams of said light pulses at an article to be sensed in projection fields wider than the sensed article to illuminate the exposed threedimensional surfaces of said article substantially uniformly and to reflect said light pulses from said surfaces and from any defects on said surfaces;
• detecting reflected light from said article corresponding to said light beams by photoelectric detector means to produce electrical sensing signals of different amplitudes;
• and
• processing said sensing signals to determine the presence of an article, to determine whether it contains a defect from the reflected visible light, and to identify any defect.

Defect detection apparatus for detecting defects in articles, comprising:

• optical sensor means for sensing articles and for scanning the articles to detect any defects therein;
• a plurality of light-emitting semiconductor devices including first devices which emit light of a first wavelength and second devices which emit light of a second wavelength different from said first wavelength, at least one of said wavelengths being visible light;
• pulser means for applying electrical pulses to said semiconductor devices to actuate said first and second devices at different times, each of said devices being turned on for much less time than it is turned off during an on/off cycle and the pulses being of substantially constant current;
• illumination means for directing the emitted light of said first and second wavelengths at said articles in projection fields wider than the sensed article to cause said light to be reflected from the exposed three dimensional surface of the sensed article and from any defects on said surface;
• and
• viewer means for receiving said reflected light and directing it to said optical sensor means which measure the amount of reflected light to detect defects in said articles.