Systems And Methods For Minimizing Aberrating Effects In Imaging Systems

• US 20090067680A1
• Filed: 11/07/2008
• Published: 03/12/2009
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: Omnivision Technologies Incorporated (Will Semiconductor Co., Ltd. Shanghai)
• Original Assignee: OmniVision CDM Optics, Inc.
• Inventors: Kubala, Kenneth Scott, Baron, Alan Eugene, Dowski, Edward Raymond JR.
• Granted Patent: US 7,889,903 B2
• Time in Patent Office: Days
• US Class Current: 382/115
• 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 5/284 of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates etalons for fibre optic multiplexing G02B6/29358; etalons for spectral measurement G01J3/26
• CPC Class Codes: G06V 40/18 Eye characteristics, e.g. of the iris

Abstract

A biometric optical recognition system includes optics, including a wavefront coding mask, for imaging a wavefront of object to be recognized to an intermediate image, and a detector for detecting the intermediate image. A modulation transfer function detected by the detector contains no zeros such that subsequent task based image processing recognizes the object. A biometric recognition system includes optics for imaging a wavefront of an object to be recognized to a first intermediate image, and a detector for detecting the first intermediate image. The optics include a phase changing element configured for modifying the wavefront such that a modulation transfer function characterizing detection of the first intermediate image contains no zeros such that subsequent task based image processing recognizes the object. In an optical imaging system that includes a solid state detector, a phase-modifying element reduces reflected power from electromagnetic energy incident upon the detector without introducing aberrations.

Claims

1. A biometric optical recognition system, comprising:

optics, including a wavefront coding mask, for imaging a wavefront of an object to be recognized to an intermediate image; and

a detector for detecting the intermediate image, wherein a modulation transfer function detected by the detector contains no zeros such that subsequent task based image processing recognizes the object.

2. The system of claim 1, further comprising a decoder, connected with the detector, for implementing the task based image processing.

3. The system of claim 2, the decoder operable as an all-pass filter in the frequency domain.

4. The system of claim 2, the decoder operable as an attenuation filter in the frequency domain for magnifications of one or less.

5. A biometric recognition system, comprising:

optics for imaging a wavefront of an object to be recognized to a first intermediate image; and

a detector for detecting the first intermediate image,

wherein the optics includes a phase changing element configured for modifying the wavefront such that a modulation transfer function characterizing detection of the first intermediate image contains no zeros such that subsequent task based image processing recognizes the object.

6. The system of claim 5, further comprising a decoder, connected with the detector, for implementing the task based image processing.

7. The system of claim 6, wherein the decoder is operable as an all-pass filter.

8. The system of claim 6, wherein the decoder is operable as an attenuation filter for magnification of at least one.

9. The system of claim 5, wherein the optics consist of a single optical element.

10. The system of claim 5, wherein the first intermediate image comprises features of the object reformatted by a spatial blurring function implemented by the phase changing element.

11. The system of claim 5,

the first intermediate image being formed with the object at a first distance from the system, a second intermediate image being formed with the object at a second distance from the system,

wherein a Hamming distance between the first and second intermediate images is less than a Hamming distance between the first and second intermediate images formed by an equivalent system but without the phase changing element, of the object, at the first and second distance from the system.

12. The system of claim 5, wherein a Hamming distance, between the first intermediate image and a second intermediate image formed by the system of a second object, is greater than a Hamming distance between intermediate images of the first and second objects formed by an equivalent system without the phase changing element.

13. The system of claim 5, the phase changing element comprising a selected one of circularly symmetric optics, constant profile path optics and rectangularly separable optics.

14. The system of claim 5, the phase changing element comprising a phase function of the form P(r,theta)=Σ

a_i rⁱ cos(w_i theta+phi_i).

15. In an optical imaging system of the type that includes a solid state detector, the improvement comprising:

a phase-modifying element for reducing reflected power from electromagnetic energy incident upon the detector without introducing image aberrations into the optical imaging system.

16. In the optical imaging system of claim 15, the further improvement wherein the phase-modifying element is configured such that the optical imaging system is characterized by a modulation transfer function, without zeros, for spatial frequencies detectable by the detector.

17. In the optical imaging system of claim 15, the further improvement comprising a decoder for post-processing data from the detector to reverse effects induced by the phase-modifying element.

18. In the optical imaging system of claim 15, the further improvement comprising a tilt surface on an optical component within the optical imaging system, to reduce reflected power from the electromagnetic energy.

19. In the optical imaging system of claim 18, the further improvement wherein the tilt surface tilts away from a plane perpendicular to a path of travel of the electromagnetic energy.

20. In the optical imaging system of claim 15, the further improvement wherein the phase-modifying element is configured for spatially diffusing the electromagnetic energy such that the electromagnetic energy does not damage the detector.

21. In the optical imaging system of claim 15, the further improvement wherein the detector comprises one of a human eye, a CCD array, a CMOS array and an IR detector.

22. In the optical imaging system of claim 15, the further improvement wherein the electromagnetic energy comprises laser radiation.

23. An optical imaging system, comprising:

imaging optics for imaging electromagnetic radiation to a detector;

tilt optics for reflecting back-scattered electromagnetic radiation from the detector to an aperture of the imaging system; and

a post processor for processing data from the detector to remove aberrations induced by the tilt optics.

24. The system of claim 23, the tilt optics being positioned at an aperture stop.

25. The system of claim 23, wherein at least one of the imaging optics and the tilt optics comprises a phase-modifying element for modifying phase of a wavefront imaged onto the detector, and wherein the post processor is configured for removing effects induced by the phase-modifying element from data of the detector.

26. The system of claim 25, the phase-modifying element being configured for altering phase such that an optical transfer function of the imaging system is substantially invariant to focus-related aberrations.

27. The system of claim 26, the post processor being configured for removing phase effects induced by the phase-modifying element to form a final image that is substantially free of the focus-related aberrations.

28. An optical imaging system, comprising:

optics for imaging electromagnetic radiation to a detector, the detector being tilted with respect to an optical axis of the optics to direct back-scattered electromagnetic radiation from the detector to an aperture stop of the imaging system; and

a post processor for processing data from the detector to remove aberrations induced by tilt of the detector.

29. The system of claim 28, wherein the optics comprise a phase-modifying element for modifying phase of a wavefront imaged to the detector, and wherein the post processor is configured for removing effects induced by the phase-modifying element.

30. The system of claim 29, wherein the optics are configured for altering the phase such that an optical transfer function of the imaging system is substantially invariant to focus-related aberrations.