Santa Barbara Research Center

John E Stannard

Geoffrey A Walter

Cathy M Peterson

Roger A West

William H Wellman

A differential spectrometry system detects very narrow-band spectral features, while providing much higher optical transmittance and signal-to-noise ratios than prior optical-filter-based spectrometer systems. A plurality of light detectors (10a, 10b) detect light that falls within respective wide wavebands. The wide wavebands have overlapping and non-overlapping portions, one of which is the desired narrow waveband. The detector outputs are operated upon to produce an output signal (22) which includes substantially only the desired narrow waveband. In the preferred embodiment, the light detectors (10a, 10b) are implemented with a pair of optical detectors (30a, 30b) and respective optical interference filters (24a, 24b). The filters have substantially identical cut-off wavelengths (.lambda..sub.2) and cut-on wavelengths that are shifted by .DELTA..lambda. with respect to each other (.lambda..sub.1 and (.lambda..sub.1 +.DELTA..lambda.), respectively). The detector outputs are differenced with an operational amplifier (33), so that detector signals resulting from spectral features common to both detectors (30a, 30b) are canceled. The remaining signal (36) varies according to the amount of light that falls between wavelength boundaries �.lambda..sub.1 and (.lambda..sub.1 +.DELTA..lambda.)!. A preferred method of fabricating the optical interference filters (24a, 24b) is also provided.

High resolution differential spectrometry system

A differential spectrometry system detects very narrow-band spectral features, while providing much higher optical transmittance and signal-to-noise ratios than prior optical-filter-based spectrometer systems. A plurality of light detectors (10a, 10b) detect light that falls within respective wide wavebands. The wide wavebands have overlapping and non-overlapping portions, one of which is the desired narrow waveband. The detector outputs are operated upon to produce an output signal (22) which includes substantially only the desired narrow waveband. In the preferred embodiment, the light detectors (10a, 10b) are implemented with a pair of optical detectors (30a, 30b) and respective optical interference filters (24a, 24b). The filters have substantially identical cut-off wavelengths (.lambda..sub.2) and cut-on wavelengths that are shifted by .DELTA..lambda. with respect to each other (.lambda..sub.1 and (.lambda..sub.1 +.DELTA..lambda.), respectively). The detector outputs are differenced with an operational amplifier (33), so that detector signals resulting from spectral features common to both detectors (30a, 30b) are canceled. The remaining signal (36) varies according to the amount of light that falls between wavelength boundaries [.lambda..sub.1 and (.lambda..sub.1 +.DELTA..lambda.)]. A preferred method of fabricating the optical interference filters (24a, 24b) is also provided.

Two broad blackbody sources (24, 26) having a constantly maintained temperature differential therebetween are alternately directed via a chopper (40) onto a detector array (12) for testing same.

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Santa Barbara, CA, United States of America

John E Stannard