Wavefront coded imaging systems

• US 20060291058A1
• Filed: 08/28/2006
• Published: 12/28/2006
• Est. Priority Date: 02/03/1995
• Status: Active Grant

• Current Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Original Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Inventors: Dowski, Edward Raymond Jr.
• Granted Patent: US 7,554,731 B2
• Time in Patent Office: Days
• US Class Current: 359/558
• CPC Class Codes: G02B 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G02B 5/00 Optical elements other than lenses light guides G02B6/00; optical logic elements G02F3/00

Abstract

An infrared imaging system for imaging infrared radiation from an object onto a detector includes optics configured for producing, with the infrared radiation, transverse ray intercept curves that are substantially straight, sloped lines. A wavefront coding element is configured such that a modulation transfer function of the optics and wavefront coding element, combined, exhibits reduced variation, over a range of spatial frequencies and caused, at least in part, by thermal variation within the imaging system, as compared to a modulation transfer function of the optics alone, without the wavefront coding element. A post processor is configured for generating an improved modulation transfer function, over the range of spatial frequencies, as compared to the modulation transfer function of the optics and the wavefront coding element.

Claims

1. An infrared imaging system for imaging infrared radiation from an object to a detector, comprising:

optics configured for producing, with the infrared radiation, transverse ray intercept curves that are substantially straight, sloped lines;

a wavefront coding element configured for modifying phase of a wavefront of the infrared radiation such that a modulation transfer function of the optics and wavefront coding element, combined, has reduced variation, over a range of spatial frequencies and caused, in part, by thermal variation within the imaging system, as compared to a modulation transfer function of the optics alone, without the wavefront coding element; and

a post processor configured for generating an improved modulation transfer function, over the range of spatial frequencies, as compared to the modulation transfer function of a combination of the optics and the wavefront coding element.

2. The infrared imaging system of claim 1, wherein the wavefront coding element is formed on a surface of the optics.

3. The infrared imaging system of claim 1, wherein the system includes an aperture stop, and wherein the wavefront coding element is disposed substantially at the aperture stop.

4. The infrared imaging system of claim 1, wherein the optics consist of a single lens.

5. The infrared imaging system of claim 4, wherein the lens includes a front surface facing the object and a back surface opposite the front surface, and wherein the wavefront coding element is formed on one of the front surface and the back surface.

6. The infrared imaging system of claim 1, wherein the wavefront coding element is further configured such that the modulation transfer function of the optics and wavefront coding element exhibits reduced variation, over a field of view of at least approximately fifty degrees, as compared to a modulation transfer function of the optics without the wavefront coding element.

7. The infrared imaging system of claim 1, wherein the post processor includes a digital filter.

8. The infrared imaging system of claim 7, wherein the digital filter includes a separable filter.

9. The infrared imaging system of claim 1, wherein the wavefront coding element includes a selected one of a rectangularly separable surface, a non-separable surface, and a surface having a sum of rectangularly separable forms.

10. In a system for imaging infrared radiation from an object to a detector, the system including optics configured for producing, with infrared radiation, transverse ray intercept curves that are substantially straight, sloped lines, an improvement comprising:

a wavefront coding element configured for modifying phase of a wavefront of the infrared radiation such that a modulation transfer function of the optics and wavefront coding element, combined, has reduced variation, over a range of spatial frequencies and caused, in part, by thermal variation within the imaging system, as compared to a modulation transfer function of the optics alone, without the wavefront coding element; and

a post processor configured for generating an improved modulation transfer function, over the range of spatial frequencies, as compared to the modulation transfer function of a combination of the optics and the wavefront coding element.

11. In the system of claim 10, the further improvement wherein the wavefront coding element is formed on a surface of the optics.

12. In the system of claim 11, the further improvement wherein the wavefront coding element is formed on a surface of the optics furthest from the object.

13. In the system of claim 10, the further improvement wherein the optics consists of a single lens.

14. In the system of claim 10, the further improvement wherein the wavefront coding element is further configured such that the modulation transfer function of the optics and wavefront coding element exhibits reduced variation, over a field of view of at least approximately fifty degrees, as compared to a modulation transfer function of the optics without the wavefront coding element.

15. In the system of claim 10, the further improvement wherein the post processor includes a digital filter.

16. In the system of claim 15, the further improvement wherein the digital filter includes a separable filter.

17. In the system of claim 10, the further improvement wherein the wavefront coding element includes a selected one of a rectangularly separable surface, a non-separable surface, and a surface having a sum of rectangularly separable forms.