High speed infrared imaging system and method

• US 6,268,883 B1
• Filed: 05/29/1998
• Issued: 07/31/2001
• Est. Priority Date: 05/30/1997
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Zehnder, Alan T., Ravichandran, G., Rosakis, Ares J.
• Primary Examiner(s): Le, Vu
• Application Number:
  US09/087,735
• Time in Patent Office: 1,159 Days
• Field of Search: 348/162, 348/163, 348/164, 348/166, 356/51, 250/330, 250/332, 250/334, 250/338.1, 250/339.02, 250/370.08
• US Class Current: 348/164
• CPC Class Codes: H04N 23/23 from thermal infrared radiation
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A system and method for radiation detection with an increased frame rate. A semi-parallel processing configuration is used to process a row or column of pixels in a focal-plane array in parallel to achieve a processing rate up to and greater than 1 million frames per second.

Claims

1. A radiation detection system, comprising:

an imaging module configured to receive radiation from an object;

a sensing array disposed to receive said radiation from said imaging module and configured to have an array of sensing pixels which are responsive to said radiation to produce a plurality of pixel signals indicative of said radiation;

a plurality of multiplexer circuits connected in parallel to said sensing array to simultaneously receive all of said pixel signals and configured to receive and hold said pixel signals according to a clock signal, wherein each of said multiplexer circuits has input ports to simultaneously receive a group of said pixel signals corresponding to a group of said pixels and sequentially outputs said group of said pixel signals at an output port; and

a plurality of digitizers respectively connected to output ports of said multiplexer circuits and configured to respectively and simultaneously sample and digitize said pixel signals in parallel from said multiplexer circuits to produce a digital representation of said pixel signals from said sensing array, wherein each digitizer sequentially digitizes each pixel signal of said group of said pixel signals sampled and held by a respective multiplexer within one period of said clock signal before said respective multiplexer resets and receives group of pixel signals from said sensing array.

2. The system as in claim 1, further comprising at least one memory unit connected to said digitizers and configured to store said digital representation.

3. The system as in claim 1, wherein said imaging module comprises two convex lenses with different focal lengths.

4. The system as in claim 1, wherein said imaging module comprises first and second pairs of spherical reflectors, wherein each pair includes a convex spherical reflector and a concave spherical reflector that is confocal with said convex spherical reflector and has a radius of curvature greater than a radius of curvature of said convex spherical reflector.

5. The system as in claim 1, further comprising a plurality of preamplifiers connected to said sensing array and said multiplexers and configured in such a way that said preamplifiers respectively correspond to said sensing pixels to receive and amplify all of said pixel signals in parallel.

6. The system as in claim 1, wherein said sensing array comprises a semiconductor compound that includes mercury, cadmium, and telluride.

7. A method of detecting an image of an object, comprising:

collecting radiation from an object;

converting said radiation into an array of electrical signals by using a sensing array with a plurality of sensing pixels arranged in rows and columns;

simultaneously receiving and holding said electrical signals in response to a clock signal by using a plurality of multiplexers that are connected to said sensing array with respect to one another in parallel, wherein each multiplexer simultaneously receives a respective group of said electrical signals corresponding to a row of said sensing pixels;

sequentially outputting said respective group of said electrical signals to an output port of each multiplexer within one period of said clock signal before said multiplexer receives new electrical signals from said sensing array;

simultaneously digitizing output signals from said multiplexers, within said one period of said clock signal, to produce a digital image of said object.

8. The method as in claim 7, further comprising simultaneously receiving and amplifying said electrical signals by using a plurality of preamplifiers that are connected to said sensor array in parallel.

9. The method as in claim 7, wherein said collecting radiation of said object is performed by using an imaging module comprises first and second pairs of spherical reflectors, wherein each pair includes a convex spherical reflector and a concave spherical reflector that is confocal with said convex spherical reflector and has a radius of curvature greater than a radius of curvature of said convex spherical reflector.

10. The method as in claim 7, wherein said sensing array comprises a semiconductor compound that includes mercury, cadmium, and telluride.

11. An imaging method, comprising:

capturing radiation from an object by using an array of sensing pixels in N rows and M columns to convert said radiation into pixel signals that constitute a snapshot image of said object;

simultaneously sampling and holding, in response to a clock signal, said pixels signals in N multiplexers connected in parallel and each having M parallel input ports to hold M pixel signals in each row in a respective multiplexer, wherein said pixels signals held in said N multiplexers represent said snapshot image;

digitizing M pixel signals held in each multiplexer, one at a time within one period of said clock signal, by using N digitizers respectively connected to said N multiplexers so that N different pixels from different rows are simultaneously digitized in parallel at a time; and

using output digital data from said N digitizers to construct a digital snapshot image of said object.

12. The method as in claim 11, further comprising using said digital snapshot image to determine a temperature map of said object at a given instant.

13. The method as in claim 11, further comprising using said digital snapshot image to determine a temporal variation in the temperature of said object.

14. The method as in claim 11, further comprising setting a clock frequency of said clock signal to not be smaller than M multiplied by a frame rate of said sensing array.

15. The method as in claim 11, wherein said capturing includes using an optical module comprises first and second pairs of spherical reflectors to image said object to said sensing array, wherein each pair includes a convex spherical reflector and a concave spherical reflector that is confocal with said convex spherical reflector and has a radius of curvature greater than a radius of curvature of said convex spherical reflector.

16. The method as in claim 15, further comprising adjusting said optical module to select radiation from a portion of said object to be captured by said sensing array.