Television – Responsive to nonvisible energy – Infrared
Reexamination Certificate
1998-05-29
2001-07-31
Le, Vu (Department: 2713)
Television
Responsive to nonvisible energy
Infrared
C348S166000, C250S338100, C250S339020
Reexamination Certificate
active
06268883
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to imaging systems and methods, and more specifically to imaging in an infrared spectrum.
BACKGROUND OF THE INVENTION
Infrared (“IR”) sensing arrays are widely used to capture images of objects that radiate in the infrared spectrum in applications such as industrial inspection, surveillance, and infrared astronomy. Each element of such sensing arrays has an infrared detector that reacts either to individual incident photons or to the total thermal energy caused by absorption of the incident photons to produce an electrical signal. The electrical signals produced by the sensing array are read out and processed to produce a digital electronic image indicative of an input IR scene.
An IR focal-plane array (“FPA”) is an IR sensing array located in a focal plane of an optical imaging module that collects the radiation from a target object so that the image of the target object is focused onto the IR sensing array. Two different configurations, monolithic and hybrid configurations, are usually used to form a photosensing IR FPA. A monolithic FPA has both IR-sensing material and electrical signal transmission paths on the same semiconductor layer. A hybrid FPA separates the IR-sensing material and electrical signal transmission paths into two layers which are aligned with each other and are interconnected with conducting elements (e.g., indium bumps).
However implemented, the image captured by the FPA needs to be read out to a subsequent signal processing circuit. The amount of information contained in the image increases with the number of pixels in the EPA. The speed of transferring this data usually forms the bottle neck of the data processing and significantly affects the frame rate of the imaging system.
High-speed IR images are desired in many applications that sense a moving object or certain transient phenomena such as a rapid change in the object temperature. Conventional IR imaging systems use different approaches to increase the frame rates.
For example, one technique implements one or more moving mirrors to achieve high frame rates. An IR imaging device manufactured by Ellis Camera Company is such an example. A polygon mirror with 6 facets may spin at a rate of 20,000 rotations per second. This produces a frame rate of 120,000 frames per second. A higher frame rate using this technique is usually difficult to achieve due to the inherent limitations of material strength and mirror balance.
Another technique implements a partially parallel data acquisition scheme in a FPA system to achieve a frame rate up to about 32,000 frames per second. Amber infrared camera developed for Wayne State University, connects four digitizers in parallel with respect to one another to simultaneously read out and digitize signals from four adjacent pixels in the FPA. An image is captured by scanning out data from the FPA with four pixels at a time.
The present invention provides an infrared imaging system and method based on a FPA to achieve imaging frame rates up to and greater than about 1 million frames per second.
SUMMARY OF THE INVENTION
The present invention is imbedded in an IR imaging system having an imaging optical module, a focal-plane array, and an electronic signal processing module. The imaging optical module receives radiation from a target object and produces an image of the object onto the FPA which converts the radiation image into an array of electrical signals. The electronic signal processing module connects to the FPA and converts the electrical signals into a digital representation of the received radiation image.
The imaging optical module is preferably placed relative to the FPA to form the image of the object with a desired magnification on the FPA. One implementation of this imaging optical module includes four spherical reflectors to form one pair of Schwarzchild systems. Each Schwarzchild system has one convex spherical reflector and one concave spherical reflector that are confocal with respect to each other. The two Schwarzchild systems are placed in an infinite conjugation configuration so that the ratio of the focal lengths of the two Schwarzchild systems determines the magnification factor of the imaging optical module.
One advantage of such doubled Schwarzchild systems is that the magnification of the image formed on the FPA can be easily adjusted to meet the requirements of certain applications.
The electronic signal processing module uses a semi-parallel configuration to improve the data readout rate from the FPA. In a preferred embodiment, the electronic signal processing module includes a plurality of preamplifier circuits each corresponding to a different pixel element in the FPA, a plurality of multiplexer circuits each connected to a row or column of pixel elements in the FPA, and a plurality of digitizers each of which corresponds to a multiplexer circuit. The data in all pixel elements in the FPA is read out in parallel to the preamplifier circuits. The multiplexer circuits are each connected to the preamplifier circuits such that each multiplexer circuit corresponds to a row or column of pixels. Each multiplexer circuit is configured to have at least the same number of input terminals as the number of pixels in a row or column of the FPA so that the data from all preamplifier circuits can be simultaneously received in parallel. The output from each multiplexer circuit is sequential, i.e., the parallel input data from a row or column of the FPA is exported one pixel at a time to the respective digitizer. Each digitizer converts the analog signals from the multiplexer into digital data. One or more memory units may be incorporated in the digitizer to temporarily store the converted data.
These and other aspects and advantages of the invention will become more apparent in light of the accompanying drawings, detailed description of the preferred embodiments, and appended claims.
REFERENCES:
patent: 3798366 (1974-03-01), Hunt et al.
patent: 3807873 (1974-04-01), Nakamori
patent: 3909521 (1975-09-01), Hunt et al.
patent: 3952151 (1976-04-01), Jenkin
patent: 3983395 (1976-09-01), Kim
patent: 4009962 (1977-03-01), Lauer et al.
patent: 4335400 (1982-06-01), Chow et al.
patent: 4338627 (1982-07-01), Stapleton
patent: 4419692 (1983-12-01), Modisette et al.
patent: 4869256 (1989-09-01), Kanno et al.
patent: 5040889 (1991-08-01), Keane
patent: 5095211 (1992-03-01), Kimata
patent: 5394237 (1995-02-01), Chang et al.
patent: 5449910 (1995-09-01), Wood et al.
patent: 5587583 (1996-12-01), Chin et al.
patent: 5663562 (1997-09-01), Jones et al.
patent: 5682035 (1997-10-01), Gallagher et al.
Ravichandran G.
Rosakis Ares J.
Zehnder Alan T.
California Institute of Technology
Fish & Richardson P.C.
Le Vu
LandOfFree
High speed infrared imaging system and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High speed infrared imaging system and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High speed infrared imaging system and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2434937