Contrast measurement system for laser marks
AssigneeHewlett-Packard Company
InventorPeng Seng Toh
Life of this patent
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Abstract
This invention relates to a technique of contrast measurement especially useful for the measurement of contrast of laser mark. The technique involves measuring the light intensity coming from a laser mark and the intensity coming from a background on the integrated circuit, calculating the contrast based on the intensities, and comparing to a gray scale. This invention enables contrast to be measured and communicated with respect to a set of references and hence eliminates subjective judgement.
Claims14
A method for establishing the quality of a laser mark applied to a surface comprising the steps of:
- illuminating a reference gray scale;
- obtaining equivalent intensity readings from light reflected off gray level steps on the reference gray scale whose optical densities are known to establish a quality reference;
- illuminating the laser mark;
- and
- obtaining a first intensity reading (I.sub.M) from light reflected off a portion of the laser mark to derive an absolute measure of quality of the laser mark based on the quality reference.
A system for establishing the quality of a laser mark on a surface comprising:
- a light source for illuminating a reference gray scale and the laser mark;
- an image sensor for determining the intensity of light reflected off the reference gray scale and the laser mark;
- and
- a processor for capturing values corresponding to the intensity of light reflected off the reference gray scale for establishing a quality reference and for capturing a value corresponding to the laser mark (I.sub.M) for deriving an absolute measure of quality based on the quality reference.
A program storage device readable by a processor in a system, tangibly embodying a program of instructions, executable by the processor to perform the method steps for establishing the quality of a laser mark applied to a surface, the method comprising the steps of:
- illuminating a reference gray scale;
- obtaining equivalent intensity readings from light reflected off marks on the reference gray scale whose optical densities are known to establish a quality reference;
- illuminating the laser mark;
- and
- obtaining a first intensity reading (I.sub.M) from light reflected off a portion of the laser mark to derive an absolute measure of quality of the laser mark based on the quality reference.
Dependencies are inferred from the claim text.