Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1998-06-05
2000-08-22
Hannaher, Constantine
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
2503361, 25033902, 25033903, 250352, G01J 514
Patent
active
061076309
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to detectors and, more particularly, to an array of photoconductive detectors.
2. Background Art
The use of photoconductive detectors for measuring radiation is well known. Because of their high sensitivity, photoconductive detectors such as PbS and PbSe are particularly effective in measuring infrared radiation. Detection of infrared radiation is used by the military for tracking warm vehicles and in night vision devices, is used by medical instrument manufacturers for measuring glucose and other body constituents in a noninvasive manner and is used by scientific instrument manufacturers for measuring chemical composition and structure.
In general, the resistance of the photoconductive detector changes when the radiation falls on its surface. Resistance changes can be measured as an electrical signal change and the intensity of the detected radiation can be estimated by the magnitude of resistance change.
Photoconductive detectors typically require a bias current or voltage to operate, such as a direct current bias. The sensitivity of the detector is proportional to the magnitude of the applied bias. It is preferred to supply a high bias to such a detector to increase its sensitivity and to overcome the noise of the electronics associated with the detector in an overall detection system.
It is common to use a plurality of photoconductive detector elements, also referred to as pixels, in the form of a linear array mounted on a common substrate to measure radiation across a spectrum of wavelengths. Each detector element is responsive to and detects a particular wavelength, or band of wavelengths, of radiation. In applications such as infrared scanners and cameras, it is a goal to integrate many photoconductive detector elements and their associated electronics into a single compact package.
It is an object of the present invention to provide a radiation detector which includes an array of photoconductive detector elements in which the performance of individual detector elements is alike. It is a further object to provide stability to the overall detector array both in terms of atmosphere and temperature stability, as well as in mechanical stability, and in an arrangement which is less complicated to manufacture than prior devices.
SUMMARY OF THE INVENTION
The present invention is a packaged linear array of detector elements which are particularly suitable for noninvasive tissue constituent measurement using infrared radiation. The dimensions of the individual detector elements should be chosen such that their size and spacing presents an electrical signal output that is usable and is relevant to the desired radiation or optical data. The preferred semiconducting material chosen for the photodetector elements is optimized for the best spectral response, signal quality and noise output for measurement of radiation signals from tissue constituents.
The packaging of the large group of detector elements in accordance with the present invention is unique and accomplishes several objects. The detector elements are interdigitated in such a way that adjacent detector elements face opposite directions. This design allows the array assembly to be manufactured in a more compact arrangement. In addition, the spacing between the individual detector signal connections can be increased to 2.54 mm or 0.1 inch or more by using one wire bond, one trace and one solder connection per detector element. Such a configuration significantly reduces the cost of the overall system.
In order to avoid contamination of the detector elements in the array, a package surrounding the detector array and associated electronics uses materials and construction to yield a high reliability seal. A window which allows radiation to impinge upon the detector array is chosen so as to not degrade the radiation's ability to reach the detector elements. The substrate carrying the array of detector elements is cooled by a thermoelectric cooler or the like, with temperature se
REFERENCES:
patent: 4225786 (1980-09-01), Perlman
patent: 5296710 (1994-03-01), Ohno et al.
patent: 5391875 (1995-02-01), Cederberg et al.
patent: 5914488 (1999-06-01), Sone
Griffith John S.
Mazurowski John S.
Norman Robert D.
Diasense, Inc.
Gabor Otilia
Hannaher Constantine
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