Illuminant discriminator
First Claim
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1. An illuminant discriminator comprising:
- an analog means for converting an impinging illuminant into an analog signal;
a digital means coupled to said analog means for converting said analog signal into a digital signal; and
computing means coupled to said digital means for performing a Fourier series analysis on said digital signal to determine the amplitude values of at least one harmonic of said analog signal, said computing means also performing a comparison of the determined amplitude values against the amplitude values of known illuminant sources to identify the type of impinging illuminant.
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Abstract
The present invention is an apparatus for discriminating among various types of illuminants such as fluorescent light, tungsten light and natural daylight. The apparatus is comprised of an analog portion and a digital portion. The analog portion functions to convert incident light into a conditioned analog signal. The digital portion utilizes an analog-to-digital converter and a microprocessor to perform a Fourier series analysis on one or more of the harmonics of the illuminant signal. The microprocessor compares the amplitudes of the harmonics against the amplitudes of known illuminant sources to identify the source.
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Citations
7 Claims
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1. An illuminant discriminator comprising:
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an analog means for converting an impinging illuminant into an analog signal; a digital means coupled to said analog means for converting said analog signal into a digital signal; and computing means coupled to said digital means for performing a Fourier series analysis on said digital signal to determine the amplitude values of at least one harmonic of said analog signal, said computing means also performing a comparison of the determined amplitude values against the amplitude values of known illuminant sources to identify the type of impinging illuminant. - View Dependent Claims (2)
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3. Illuminant discrimination apparatus for detecting which of three types of impinging light, tungsten light, fluorescent light or daylight is predominant comprising:
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light-sensitive means responsive to incident light for producing an analog signal; circuit means connected to said light-sensitive means for conditioning said analog signal for analog-to-digital conversion; analog-to-digital converter means coupled to said circuit means for converting said analog signal into a digital signal; and processor means connected to said analog-to-digital converter for determining the amplitude values of at least one of the harmonics of said analog signal from said digital signal and for comparing the determined amplitude values against the amplitude values corresponding to tungsten light, fluorescent light and daylight to identify the predominant impinging light. - View Dependent Claims (4, 5)
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6. A method for discriminating between an impinging tungsten light, fluorescent light or daylight comprising the steps of:
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(a) producing an analog signal as a function of an impinging light; (b) converting said analog signal into a digital signal; (c) determining from said digital signal the amplitude values of at least one harmonic of said analog signal; and (d) comparing the amplitude values determined in step (c) against the amplitude values of known tungsten light, fluorescent light and daylight to determine a match.
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7. A method for discriminating between an impinging tungsten light, fluorescent light or daylight comprising the steps of:
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(a) producing an analog signal as a function of an impinging light; (b) converting said analog signal into a digital signal; (c) determining from said digital signal the fundamental frequency of said analog signal; (d) determining at least the first harmonic of said analog signal; (e) determining the amplitudes of the fundamental frequency and the first harmonics of said analog signal; and (f) comparing the amplitude values determined in step (e) against the amplitude values of known tungsten light, fluorescent light and daylight to determine a match.
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Specification