Method and system for detecting defects in optically transmissive coatings formed on optical media substrates
First Claim
1. A method for detecting defects in an optically transmissive coating formed on an optical media substrate, the method comprising the steps of:
- illuminating the coating with light having a wavelength matched to peak absorption wavelengths of the coating to obtain a transmitted light signal;
generating a first electronic signal from the transmitted light signal, the first electronic signal having high frequency defect data and background data having a frequency less than the frequency of the high frequency defect data;
filtering the first electronic signal to pass the high frequency defect data while substantially eliminating the background data; and
processing at least the high frequency defect data to determine the defects in real-time wherein the step of processing determines local defects in real-time.
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Accused Products
Abstract
Spectral transmittance of a dye coating for optical data is determined off-line. Light source wavelength is then matched to the wavelengths at which the dye has the least transmission (i.e. maximum absorbance). The method and system of the present invention are provided for detecting local and global defects in the coating wherein the inspection is done at the maximum absorbance wavelengths to produce a maximum change in a transmitted light signal for a given change in physical thickness of the dye coating. Relative change in thickness is determined based on the change in the transmitted light signal through the dye coating. In order to complete detection and measurement of the transmittance changes, a pair of electronic signals are split from a camera signal wherein one of the electronic signals is filtered by a FIR filter to identify local changes in dye thickness against a globally varying background. In order to detect global variations in the dye thickness, the other electronic signal is processed by a simple thresholding circuit.
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Citations
24 Claims
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1. A method for detecting defects in an optically transmissive coating formed on an optical media substrate, the method comprising the steps of:
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illuminating the coating with light having a wavelength matched to peak absorption wavelengths of the coating to obtain a transmitted light signal; generating a first electronic signal from the transmitted light signal, the first electronic signal having high frequency defect data and background data having a frequency less than the frequency of the high frequency defect data; filtering the first electronic signal to pass the high frequency defect data while substantially eliminating the background data; and processing at least the high frequency defect data to determine the defects in real-time wherein the step of processing determines local defects in real-time. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for detecting defects in an optically transmissive coating formed on an optical media substrate, the method comprising the steps of:
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illuminating the coating with light having a wavelength matched to peak absorption wavelengths of the coating to obtain a transmitted light signal; generating a first electronic signal from the transmitted light signal, the first electronic signal having high frequency defect data and background data having a frequency less than the frequency of the high frequency defect data; generating a second electronic signal having the high frequency defect data and background data, and processing at least the high frequency defect data to determine the defect in real time wherein the step of processing includes the step of processing the high frequency defect data and the background data to detect global defects in real-time. - View Dependent Claims (9)
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10. A system for detecting defects in an optically transmissive coating formed on an optical media substrate, the system comprising:
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a base for supporting the optical media substrate with an optical transmissive coating formed thereon; means for illuminating the coating with light having a wavelength matched to peak absorption wavelengths of the coating to obtain a transmitted light signal; means for generating a first electronic signal from the transmitted light signal, the first electronic signal having high frequency defect data and background data having a frequency less than the frequency of the high frequency defect data; a filter for filtering the first electronic signal to pass the high frequency defect data while substantially eliminating the background data; and a processor for processing at least the high frequency defect data to determine the defects in real-time wherein the processor processes the high frequency defect data to determine local defects in real-time. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A system for detecting defects in an optically transmissive coating formed on an optical media substrate, the system comprising:
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a base for supporting the optical media substrate with an optical transmissive coating formed thereon; means for illuminating the coating with light having a wavelength matched to peak absorption wavelengths of the coating to obtain a transmitted light signal; means for generating a first electronic signal from the transmitted light signal, the first electronic signal having high frequency defect data and background data having a frequency less than the frequency of the high frequency defect data wherein the means for generating includes a camera adapted to respond to the transmitted light signal to obtain a camera signal; a splitter for splitting the camera signal into the first electronic signal and a second electronic signal, the second electronic signal also having the high frequency defect data and the background data; and a processor for processing at least the high frequency defect data to determine the defects in real-time. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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Specification