Abstract:
Spectrometer apparatus (10), for self-calibrating a color image scanner (30) of the line scanner or area scanner type, comprises a member (20), having an optical slit (18), movable into position on an optical axis (14) of the scanner between its polychromatic light source (12) and its focusable lens (16) in a plane occupied by a color image when it is scanned. A diffraction grating (24) is similarly movable onto the optical axis, a given distance from an image sensor (22) of the scanner. The light source illuminates the slit and the diffraction grating disperses transmitted polychromatic light according to its wavelength, forming duplicate spectra off-axis across respective halves of the image sensor, with longer wavelengths being diverted to respectively higher angles.
Abstract:
The invention is a device for the multiplex detection of a plurality of characteristic signals from a plurality of samples. Previous multiplex systems using Hadamard transform multiplexing were often limited to 4n-1 samples (n = 1, 2, 3 etc.). The present invention overcomes this limitations by encoding signals after they had been modulated by a sine function or a cosine function (or a combination of sine and cosine functions). Such modulation of signals using the "sine/cosine transform" is easier to implement than Hadamard transforms and there is no limitation imposed on the number of samples.
Abstract:
A time resolved spectroscopy system and method are provided using digital processing tehcniques of a low power, continuous wave signal generated by a continuous wave light source, such as a cw laser. Time elapse is determined by measuring the time shift of the signal modulation sequence using the cross correlation of a return signal with the reference signal. The high resolution time delay is introduced at the start of each modulation cycle and the high resolution measurement is constructed by interlacing a data set based on the delay information. The high resolution TRS or fluorescence measurement is achieved by correlation calculation of the measured data and the reference code and deconvolving the autocorrelation function of the reference code.
Abstract:
An optical spectrograph utilizes a plurality of holographic transmission optical gratings (34, 36) operative to receive an incoming source of light (26) to be analyzed and diffract the light such that different spectral components impinge upon spatially separated regions of an opto-electric detector (10). Various grating configurations are disclosed, including a physical stack of gratings conductive to extreme compactness, as well as a spaced-apart configuration used to preclude spectral cross-talk in certain configurations. Diverging light emerging from a fiber-optic bundle (22) collimated by a first lens assembly (28) prior to passing through the gratings (34, 36) and a second lens assembly (50) is used to focus the diffracted light onto the detectors (10), preferably in the form of a two-dimensional CCD array.
Abstract:
A spectrophotometer useful for spectral analysis of light emanating from one or more targets (37) within an image. The apparatus comprises a diffractive lens (13) having an optical axis, a planar array of photodetector elements (pixel's) (32), a means for changing the distance between the photodetector array (32) and the diffractive lens (31) along the optical axis and a signal processor (34). If either the array (32) or lens (31) is moved along the optical axis, different wavelengths of light from each target within the image come into or out of focus on particular photodetector elements in the plane of array (32) generating sequential images corresponding to different wavelenghts. By tracking each pixel's output in the array as a function of lens position relative to the array, the spectral composition of each target within the image is generated.
Abstract:
An apparatus and method of wavelength detection and parameter sensing uses a variable magnetic field applied to a Faraday effect thin magnetizable film to perform spectral analysis based on detected intensity distribution of diffracted light for known magnetic field strengths. The strength of the applied magnetic field can also be varied by change in a physical parameter relative to a fixed magnet in a magnetic circuit which generates a magnetic field about the grating to produce diffracted wavelengths which correspond to the parameter which influences the magnetic circuit.
Abstract:
A procedure for enhancing the resolution of spectral data, in which the Fourier self-deconvolution method FSD is used to produce from the input spectrum a data set in an interval 0 - Lt, the maximum entropy method MEM is used to compute prediction error filter coefficients {ak} from this data, and by the linear prediction method LP, using said coefficients {ak} and the data points 0 to M, data are predicted in the interferogram I(x) beyond Lt, whereby in the output spectrum maximum line narrowing with minimum distortion is achieved.
Abstract:
A beam of visible or UV light is directed by a sliding mirror (20) onto a diffraction grating (33) through each of a plurality of collimators (29 to 32) in turn. At each turn a photodiode array (35) measures the spectrum of a corresponding portion of the range of frequencies over which the instrument operates. A set of broad-band band-pass filters (16) may eliminate undesired frequencies at each turn.
Abstract:
An imaging spectrometer device useful for providing a dispersed image of the earth's surface (useful in botanical, geographical, geological, and hydrological scientific studies) from a flying platform. In accordance with this invention, a spectrometer device is provided which can be attached to an existing optical telescope. The spectrometer provides a planar focal plane image which can be processed in a number of manners, for example, by using an array of photosensitive elements. In accordance with the principal feature of this invention, the spectrometer includes an optical system wherein light rays are directed through prisms as they pass through the two symmetrical "legs" of the spectrometer. The spectrometer employs a reflecting concave mirror and prism assemblies having parallel entrance and exit surfaces. In accordance with a first embodiment, a single prism assembly is employed whereas the second described embodiment uses a pair of generally identical prism assemblies.
Abstract:
A high-sensitivity sensor configuration improves upon airbone hyperspectral and multispectral sensing, particularly for thermal/infrared military target detection and/or identification. The invention combines dispersive spectrometer and filtered TDI detector techniques to provide improved NESR through increased dwell time, along with interband temporal simultaneity and spatial registration. Embodiments relating to hyperspectral, multispectral, and dual-band arrangements are disclosed.