Image processing apparatus and method with locking feature

• US 6,570,708 B1
• Filed: 09/18/2000
• Issued: 05/27/2003
• Est. Priority Date: 09/18/2000
• Status: Expired due to Term

• Current Assignee: Institut national d'optique
• Original Assignee: Institut national d'optique
• Inventors: Doucet, Michel, Bergeron, Alain, Prévost, Donald
• Primary Examiner(s): Nguyen, Thong
• Assistant Examiner(s): ASSAF, FAYEZ G
• Application Number:
  US09/664,355
• Time in Patent Office: 981 Days
• Field of Search: 359/558, 359/559, 359/561, 359/560, 382/210, 380/54
• US Class Current: 359/559
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G02B 27/52 Phase contrast optics in microscopes G02B21/14
• CPC Class Codes: G06V 10/89 using frequency domain filters, e.g. Fourier masks implemented on spatial light modulators

Abstract

An optical coherent processor or correlator for processing an input image produced by an imaging device illuminated by a coherent light source utilizes an optical key for preventing unauthorized use of the processor. The principle underlying processing apparatus and method according to the invention uses an optical lock in combination with an encoded software key superimposed on a filter image. The optical lock, which is preferably in hardware form, consists of a first optical mask implementing a locking mask function that is preferably complex (phase and/or amplitude), which first optical mask is included in the optical path of the processor. The mask is fixed during assembly of the processor or correlator and a unique pattern is encoded thereon. The software key consists of a pattern defined by a key mask function that is displayed preferably using a spatial light modulator as part of a second optical mask included on the processor optical path. The key mask function is designed to compensate for the wave-front distortion generated by the locking mask function of the first optical mask. Therefore, an optical processor or correlator provided with its unique hardware lock cannot generates useful correlation, unless a corresponding unique software key is used.

Claims

1. An apparatus for processing an input image produced by an imaging device illuminated by a coherent light source, said apparatus comprising:

first Fourier transform means for performing the Fourier transform of said input image to generate a corresponding transformed input image in the spatial frequency domain within an area defined by a Fourier transform filter plane;

first optical mask means being disposed within said area, said first optical mask implementing a locking mask function;

data processor means for generating filter mask function control data;

second optical mask means disposed within said area, said second optical mask means implementing a filter mask function according to said filter mask function control data to generate with said locking mask function a combined image in the spatial frequency domain;

second Fourier transform means for performing the inverse Fourier transform of said combined image to generate a processed image only if said filter mask function control data include key control data corresponding to a key mask function complementary to said locking mask function for substantially cancel the locking effect thereof.

2. The apparatus of claim 1, wherein said locking mask function is a phase mask function.

3. The apparatus of claim 1, wherein said locking mask function is a complex mask function.

4. The apparatus of claim 3, wherein said locking mask function is expressed by the following relation:

5. The apparatus of claim 4, wherein said key mask function is expressed by the following relation:

6. The apparatus of claim 1, wherein said first optical mask means include an optical element having a profile specifically shaped to provide said reference locking mask function.

7. The apparatus of claim 1, wherein said second optical mask means include a spatial light modulator.

8. The apparatus of claim 1, wherein said data processor means for generating filter mask function control data include a computer having a memory for storing data representing said filter mask function as a selected one of a plurality of selectable filter mask functions each formed by a respective processing function and said key mask function.

9. The apparatus of claim 8, wherein said second optical mask means include a spatial light modulator.

10. The apparatus of claim 8, wherein said stored data is encrypted into said memory.

11. The apparatus of claim 1, further comprising data processor means for generating locking mask function control data, said locking mask function being implemented according to said locking mask function data.

12. The apparatus of claim 11, wherein said first optical mask means includes a spatial light modulator.

13. The apparatus of claim 11, wherein said data processor means for generating locking mask function control data include a computer having a memory for storing data representing said locking mask function as a selected one of a plurality of locking mask functions that can be selected for said apparatus.

14. The apparatus of claim 13, wherein said first optical mask means includes a spatial light modulator.

15. The apparatus of claim 11, further comprising data processor means for generating processing mask function data, said first optical mask means further implementing a corresponding processing mask function used to generate said combined image.

16. The apparatus of claim 15, wherein said first optical mask means includes a spatial light modulator.

17. A lockable coherent optical processing apparatus comprising:

a laser source for generating substantially coherent light;

an input imaging device receiving the coherent light to produce an input image;

first Fourier transform means for performing the Fourier transform of said input image to generate a corresponding transformed input image in the spatial frequency domain within an area defined by a Fourier transform filter plane;

first optical mask means being disposed within said area, said first optical mask implementing a locking mask function;

data processor means for generating filter mask function control data;

second optical mask means disposed within said area, said second optical mask means implementing a filter mask function according to said filter mask function control data to generate with said locking mask function a combined image in the spatial frequency domain;

second Fourier transform means for performing the inverse Fourier transform of said combined image to generate a processed image only if said filter mask function control data include key control data corresponding to a key mask function complementary to said locking mask function for substantially cancel the locking effect thereof.

18. An optical correlator for analyzing an input image produced by an imaging device illuminated by a coherent light source, said optical correlator comprising:

first Fourier transform means for performing the Fourier transform of said input image to generate a corresponding transformed input image in the spatial frequency domain within an area defined by a Fourier transform filter plane;

first optical mask means being disposed within said area, said first optical mask implementing a locking mask function;

data processor means for generating filter mask function control data;

second optical mask means disposed within said area, said second optical mask means implementing said filter mask function according to said filter mask function control data to generate with said locking mask function a combined image in the spatial frequency domain;

second Fourier transform means for performing the inverse Fourier transform of said combined image to generate a correlation indicating image only if said filter mask function control data include key control data corresponding to a key mask function complementary to said locking mask function for substantially cancel the locking effect thereof.

19. The optical correlator of claim 18, wherein said locking mask function is a phase mask function.

20. The optical correlator of claim 18, wherein said locking mask function is a complex mask function.

21. The optical correlator of claim 20, wherein said locking mask function is expressed by the following relation:

22. The optical correlator of claim 21, wherein said key mask function is expressed by the following relation:

23. The optical correlator of claim 18, wherein said first optical mask means include an optical element having a profile specifically shaped to provide said reference locking mask function.

24. The optical correlator of claim 18, wherein said second optical mask means include a spatial light modulator.

25. The optical correlator of claim 18, wherein said data processor means for generating filter mask function control data include a computer having a memory for storing data representing said filter mask function as a selected one of a plurality of selectable filter mask functions each formed by a respective processing function and said key mask function.

26. The optical correlator of claim 25, wherein said second optical mask means include a spatial light modulator.

27. The optical correlator of claim 25, wherein said stored data is encrypted into said memory.

28. The optical correlator of claim 18, further comprising data processor means for generating locking mask function control data, said locking mask function being implemented according to said locking mask function data.

29. The optical correlator of claim 28, wherein said first optical mask means includes a spatial light modulator.

30. The optical correlator of claim 28, wherein said data processor means for generating locking mask function control data include a computer having a memory for storing data representing said locking mask function as a selected one of a plurality of locking mask functions that can be selected for said apparatus.

31. The optical correlator of claim 30, wherein said first optical mask means includes a spatial light modulator.

32. A lock device for controlling the use of an optical image processor including a laser source for generating and directing substantially coherent light onto an input imaging device producing an input image, first Fourier transform means for performing the Fourier transform of said input image to generate a corresponding transformed input image in the spatial domain within an area defined by a Fourier transform filter plane, second Fourier transform means for performing the inverse Fourier transform of said transformed input image to be combined in the spatial frequency domain with a filter mask image to generate a processed image;

said lock device comprising;

first optical mask means being disposed within said area, said first optical mask implementing a locking mask function;

data processor means for generating filter mask function control data;

second optical mask means disposed within said area, said second optical mask means implementing a filter mask function according to said filter mask function control data to generate with said locking mask function said filter mask image, wherein said processed image is generated by said image processor only if said filter mask function control data include key control data corresponding to a key mask function complementary to said locking mask function for substantially cancel the locking effect thereof.

33. The device of claim 32, wherein said locking mask function is a phase mask function.

34. The device of claim 32, wherein said locking mask function is a complex mask function.

35. The device of claim 34, wherein said locking mask function is expressed by the following relation:

36. The device of claim 35, wherein said key mask function is expressed by the following relation:

37. The device of claim 32, wherein said first optical mask means include an optical element having a profile specifically shaped to provide said reference locking mask function.

38. The device of claim 32, wherein said second optical mask means include a spatial light modulator.

39. The device of claim 32, wherein said data processor means for generating filter mask function control data include a computer having a memory for storing data representing said filter mask function as a selected one of a plurality of selectable filter mask functions each formed by a respective processing function and said key mask function.

40. The device of claim 39, wherein said second optical mask means include a spatial light modulator.

41. The device of claim 39, wherein said stored data is encrypted into said memory.

42. The device of claim 32, further comprising data processor means for generating locking mask function control data, said locking mask function being implemented according to said locking mask function data.

43. The apparatus of claim 42, wherein said first optical mask means includes a spatial light modulator.

44. The device of claim 42, wherein said data processor means for generating locking mask function control data include a computer having a memory for storing data representing said locking mask function as a selected one of a plurality of locking mask functions that can be selected for said device.

45. The apparatus of claim 44, wherein said first optical mask means includes a spatial light modulator.

46. The device of claim 42 further comprising data processor means for generating processing mask function data, said first optical mask further implementing a corresponding processing mask function used to generate said combined image.

47. The apparatus of claim 46, wherein said first optical mask means includes a spatial light modulator.

48. A method of processing an input image produced by an imaging device illuminated by a coherent light source, said method comprising the steps of:

a) performing the Fourier transform of said input image to generate a corresponding transformed input image in the spatial frequency domain within an area defined by a Fourier transform filter plane;

b) combining said transformed input image with a filter mask image and a locking mask image respectively defined by a filter mask function and a locking mask function to generate a combined image in the spatial domain; and

c) performing the inverse Fourier transform of said combined image to generate a processed image only if said filter mask function include a key mask function complementary to said locking mask function for substantially cancel the locking effect thereof.

49. The method of claim 48, wherein said locking mask function is a phase mask function.

50. The method of claim 48, wherein said locking mask function is a complex mask function.

51. The method of claim 50, wherein said locking mask function is expressed by the following relation:

52. The apparatus of claim 51, wherein said key mask function is expressed by the following relation: