Abstract: A temporal-spectral multiplexing sensor for simultaneous or near simultaneous spatial-temporal-spectral analysis of an incoming optical radiation field. A spectral encoder produces a time series of spectrally encoded optical images at a high sampling rate. A series of full panchromatic spectrally encoded optical images are collected at a rate similar to the sampling rate. A detector records at least one spatial region of the spectrally encoded optical image. A processor is configured to process two series of spectrally encoded optical images to produce an artifact-free spectral image. The processing includes using the panchromatic images to normalize the spectrally encoded images, and decoding the normalized encoded images to produce high fidelity spectral signatures, free of temporal artifacts due to fluctuations at frequencies slower than the sampling rate for polychromatic images.

Abstract: A temporal-spectral multiplexing sensor for simultaneous or near simultaneous spatial-temporal-spectral analysis of an incoming optical radiation field. A spectral encoder produces a time series of spectrally encoded optical images at a high sampling rate. A series of full panchromatic spectrally encoded optical images are collected at a rate similar to the sampling rate. A detector records at least one spatial region of the spectrally encoded optical image. A processor is configured to process two series of spectrally encoded optical images to produce an artifact-free spectral image. The processing includes using the panchromatic images to normalize the spectrally encoded images, and decoding the normalized encoded images to produce high fidelity spectral signatures, free of temporal artifacts due to fluctuations at frequencies slower than the sampling rate for polychromatic images.

Abstract: A system for controlling the uniformity of combustion over a range of operating conditions in a combustor with a plurality of fuel nozzles. The system includes a number of optical sensors, each sensor comprising an optical probe that collects naturally occurring optical radiation emanating from a segment of the combustor or combustor exhaust, and at least one transducer that receives the radiation collected by the probes, compares the intensity of collected radiation from each sensor in a plurality of spectral pass-bands that are indicative of the fuel/air ratio in the combustor segments, and produces output signals that are indicative of the state of combustion in the combustor segments. A control system receives the output signals from the transducers and in response controls the fuel flow to the fuel nozzles to achieve an output from each of the sensors that has been determined to be indicative of a predetermined state of combustion.

Abstract: An adaptive spectral sensor, and methods of using the sensor. The sensor uses a programmable band pass transmission filter to produce both contrast signals, which discriminate specific target materials from background materials by comparing spectral signatures in hardware, and scene radiance spectra. The adaptive spectral sensor may measure one or more scene spectra and may form a spectral image. The sensor may automatically adjust to changing spectral, spatial and temporal conditions in the environment being monitored, by changing sensor resolution in those dimensions and by changing the detection band pass. The programmable band pass can be changed on-the-fly in real time to implement a variety of detection techniques in hardware or measure the spatial or spectral signatures of specific materials and scenes.

Abstract: A radiative transport band model method for prediction and analysis of high spectral resolution radiometric measurements. Atomic and molecular line center absorption is determined from finite spectral bin equivalent widths. A mathematically exact expansion for finite bin equivalent widths provides high accuracy at any desired spectral resolution. The temperature and pressure dependent Voigt line tail spectral absorption contributing to each spectral bin is pre-computed and fit to Padé approximants for rapid and accurate accounting of neighboring-to-distant lines. A specific embodiment has been incorporated into the MODTRAN™ radiation transport model.

Abstract: A spectral encoder for producing spectrally selected images of a radiation field containing multiple spectral components. An imaging spectrograph defines a first optical path that produces from the input radiation field a spectrally dispersed image comprising multiple spectral components displaced along a dispersion direction. Spectral pass bands are encoded on the dispersed image by a programmable spatial light modulator using one or more spatial masks. The imaging spectrograph further defines a second optical path that reverses the spectral dispersion of the first path and produces a spectrally-encoded polychromatic output image containing only those spectral components encoded by the spatial mask. The first and second optical paths share a common dispersing element. A detector records at least one spatial region of the spectrally encoded output image.

Abstract: A spectral encoder for producing spectrally selected images of a radiation field containing multiple spectral components. An imaging spectrograph defines a first optical path that produces from the input radiation field a spectrally dispersed image comprising multiple spectral components displaced along a dispersion direction. Spectral pass bands are encoded on the dispersed image by a programmable spatial light modulator using one or more spatial masks. The imaging spectrograph further defines a second optical path that reverses the spectral dispersion of the first path and produces a spectrally-encoded polychromatic output image containing only those spectral components encoded by the spatial mask. The first and second optical paths share a common dispersing element. A detector records at least one spatial region of the spectrally encoded output image.

Abstract: A radiative transport band model method for prediction and analysis of high spectral resolution radiometric measurements. Atomic and molecular line center absorption is determined from finite spectral bin equivalent widths. A mathematically exact expansion for finite bin equivalent widths provides high accuracy at any desired spectral resolution. The temperature and pressure dependent Voigt line tail spectral absorption contributing to each spectral bin is pre-computed and fit to Padé approximants for rapid and accurate accounting of neighboring-to-distant lines. A specific embodiment has been incorporated into the MODTRAN™ radiation transport model.

Abstract: A system and method for remotely determining at least one of the temperature of, and the relative concentrations of species making up, a hot fluid, based on the spectral structure of radiation emitted from the fluid. Thermal radiation over a field of view including the hot fluid is collected. At least a portion of the emission spectrum from the collected radiation is resolved. The resolved emission spectrum is resolved into spectra that are characteristic of specific emitting species and emitter temperatures. The temperature of, and the relative concentrations of species making up, the hot fluid, are determined from the relative amounts of at least two resolved spectra.

Abstract: A method and apparatus for in situ measurement of the concentration of a gas with a frequency modulated tunable diode laser is disclosed. The sampling cell, which is mounted in the flow of gases to be measured, is a Herriott cell. Gas enters the sampling cell through sintered metal filters that prevent entrance of particulates. Signals from a sample detector and a null detector are compared to eliminate interference patterns from the laser optics. High accuracy dynamic calibration of the apparatus is also disclosed.

Abstract: A multi-pass optical cell for measuring the concentration of one or more species in a fluid to be monitored includes a sample region; a source of collimated radiation; a detector device for sensing the intensity of the radiation; at least two reflective surfaces for reflecting in a first direction in the sample region a number of times the radiation from the source and delivering it to the detector device.

Abstract: An off-line-locked laser diode species monitor system includes: reference means for including at least one known species having a first absorption wavelength; a laser source for irradiating the reference means and at least one sample species having a second absorption wavelength differing from the first absorption wavelength by a predetermined amount; means for locking the wavelength of the laser source to the first wavelength of the at least one known species in the reference means; a controller for defeating the means for locking and for displacing the laser source wavelength from said first absorption wavelength by said predetermined amount to the second absorption wavelength; and a sample detector device for determining laser radiation absorption at the second wavelength transmitted through the sample to detect the presence of the at least one sample species.