Santa Barbara Research Center

Geoffrey A Walter

John E Stannard

Cathy M Peterson

Roger A West

Michael D Jack

David R Nelson

Jose A Santana

Stephen H Propst

Robert D Stephens

Lane H Rubin

Christopher B Tacelli

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.

A light source radiates an infrared beam that passes through a chopper, a calibration cell and the exhaust plume of a motor vehicle passing in front of the source. A photosensor assembly includes a plurality of photodetectors which are spaced closely adjacent to each other and simultaneously sense the beam after it propagates through the plume. An optical beam homogenizer or integrator disposed between the plume and the photosensor unit causes the light incident on the photodetectors to have uniform intensity. The photodetectors are sensitive to different wavelengths corresponding to spectral absorption peaks of constituents of the composition of the plume, including carbon monoxide (CO), carbon dioxide (CO.sub.2), hydrocarbon (HC), water vapor (H.sub.2 O) and nitric oxide (NO). A computer computes the composition of the plume as the percentages of the constituents based on the sensed transmittances of the respective wavelengths through the plume. A video camera produces a video image of the vehicle license plate, which is displayed on a video monitor and recorded on a video recorder together with the plume composition data.

Optical sensing apparatus for remotely measuring exhaust gas composition

Infrared transmitting windows having a diamond support are formed by first depositing diamond (14) on a mold (10) comprising a material which can withstand the optimum diamond growth temperatures. A germanium carbide adhesive layer (18) is deposited on the diamond layer Next, ZnSe, ZnS, or other index-matching material (16) is deposited on top of the diamond coating. Finally, the mold is removed. The end product is a diamond/ZnS(e) IR window requiring little or no polishing of diamond surfaces.

Growing community of inventors

Santa Ynez, CA, United States of America

Geoffrey A Walter