Optical image processor with highly selectable modulation transfer function

• US 4,854,669 A
• Filed: 06/17/1988
• Issued: 08/08/1989
• Est. Priority Date: 02/27/1987
• Status: Expired due to Fees

• Current Assignee: Quantum Diagnostics Limited
• Original Assignee: Quantum Diagnostics Limited
• Inventors: Hsu, Fu K., Birnbach, Curtis
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Edmondson, David J.
• Application Number:
  US07/211,218
• Time in Patent Office: 417 Days
• Field of Search: 350/162.12, 350/356, 350/392, 382/43
• US Class Current: 359/276
• CPC Class Codes: G02B 27/46 Systems using spatial filters
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means

Abstract

An optical image processor utilizes a source of partially coherent light and a spatial filter with a highly selectable modulation transfer function for processing an image, which may be present in real time. The spatial filter contains electro-optic material with electrodes arranged on such material to form a plurality of annular bands of different radii that are concentrically-situated and invididually-addressable. The annular bands are changeable in transmissivity in a continuous spectrum from transparent to opaque in response to an electrical signal on the respective electrodes of the bands. A first optical transmission path receives the image to be processed and optically transmits the image to the spatial filter for processing. A second optical transmission path receives the image processed by the spatial filter and optically transmits the image to an output port. The first and second optical transmission paths may each contain a respective spatial light modulator, whereby, for example, gray scale operations can be performed on the image. Each of the first and second optical transmission paths may include a respective zoom lens, whereby the output image size may be adjusted during image processing without interfering with the operation of the spatial filter. The spatial filter may have a reflective backing on one side for system compactness.

Claims

1. An optical image processor comprising:

input means for providing an image to be processed. p1 first transmission means for receiving an image beam, imparting partial coherence to the image beam, and optically transmitting the image beam along a first path to a spatial filter for processing; and

second transmission means for receiving an image beam processed by said spatial filter and optically transmitting the image beam along a second path to an output port;

said spatial filter containing a layer of electro-optic material with electrodes arranged thereon to form a plurality of individually-addressable, concentric annular bands of different radii, said annular bands being selectively changeable in transmissivity in a continuous spectrum from transparent to opaque in response to an electrical signal on the respective electrodes of the bands.

2. The image processor of claim 1, wherein said first transmission means includes a first spatial light modulator in the first path for receiving and amplifying an image beam to be processed.

3. The image processor of claim 2, wherein said second transmission means includes a second spatial light modulator in the second path for receiving the processed image and transmitting to the output port an image processed by the first and second spatial light modulators, whereby the first and second spatial light modulators can cooperatively interact, for example, to process the image beam by blocking gray values above an upper threshold and those below a lower threshold.

4. The image processor of claim 3, further including an optical mount and wherein:

said second transmission means includes a zoom lens in the second path; and

said first and second spatial light modulators are mounted on said optical mount;

said zoom lens being isolated from said optical mount, whereby second first and second spatial light modulators are isolated from said zoom lens.

5. The image processor of claim 2, wherein said first transmission means includes a first zoom lens in the first path and said second transmission means includes a second zoom lens in the second path, whereby adjustment of the second zoom lens changes the size of the output image beam without changing any interaction between the first zoo lens and the spatial filter.

6. The image processor of claim 1, wherein said second transmission means includes a spatial light modulator in the second path for receiving and amplifying said processed image beam before it reaches the output port.

7. The image processor of claim 1, wherein said first transmission means includes:

a spatial light modulator in the first path for receiving the image beam to be processed and producing an output pattern with reflectively varying in correspondence with the image received;

a source of collimated and monochromatic light; and

means to direct said collimated and monochromatic light onto the reflective output pattern of said spatial light modulator, whereby the light reflected off said pattern is higher in intensity than the image received by the spatial light modulator.

8. The image processor of claim 1, wherein said spatial filer has an input surface for receiving an image beam from said first transmission means, and includes a reflective material situated on an opposite surface of the spatial filter and oriented to reflect the image beam back through the spatial filter, whereby the first and second paths are coincident over at least a portion of their respective lengths.

9. The image processor of claim 1, wherein said input means comprises photographic film and a source of collimated and monochromatized light for illuminating said film.

10. The image processor of claim 9, wherein said film is cine film.

11. The image processor of claim 9, wherein:

said source of collimated and monochromatized light comprises an arc lamp, a first collimator and a first monochromatizing filter; and

said first transmission means includes a second collimator, a second monochromatizing filter supplied with light by said arc lamp, a spatial light modulator in the first path for receiving the image beam to be processed and producing an output pattern with reflectivity varying in conformity with the image received and means to direct light from said second collimator and said second monochromatizing filter onto the reflective output pattern of said spatial light modulator to produce an amplified image beam;

whereby said arc lamp is used for multiple purposes.

12. The image processor of claim 1, wherein:

said first transmission means includes a grating situated prior to said spatial filter in the first path and producing a diffraction pattern at a Fourier plane; and

said spatial filter is accompanied by a plurality of like spatial filters respectively arrayed to receive image information in the diffraction pattern.

13. The image processor of claim 12, wherein at least two of said spatial filters are stacked on each other to provide a balanced processing arrangement for points in said diffraction pattern of different order.

14. The image processor of claim 12, wherein said grating comprises a two-dimensional sinusoidal grating and three of said spatial filters are stacked on each other in positions corresponding to a zero order point of said diffraction pattern, two of said spatial filters are stacked in positions corresponding to first order points of said diffraction pattern;

and a single spatial filter is placed in a position corresponding to second order points of said diffraction pattern.

15. The image processor of claim 14, wherein said first transmission means includes a source of collimated and monochromatized light, and amplifying means to intensify an image beam in the first path, said means supplied with light by said light source.

16. The image processor of claim 14, wherein said first and second transmission means commonly share a polarizing beam splitter receiving and reflecting by 90°

light from said first light source into the first path in a direction away from said spatial filter and towards said amplifying means for intensifying the input image beam, while passing without reflection on an amplified image beam in the first path traveling toward said spatial filter, and receiving and reflecting by 90°

an image beam processed by said spatial filter and directing said processed beam towards said output port, whereby multiple use of said polarizing beam splitter reduces processor size.

17. The image processor of claim 1, wherein said first transmission means includes an image rotation prism to permit rotation of the image beam.

18. The image processor of claim 1, wherein said first transmission means comprises a source of collimated and monochromatic light, said light source including an array of redundant lamps mounted on a carousel, a sensor to detect the failure of a lamp in use, a motor means responsive to said sensor for moving another of said redundant lamps into the position occupied by said lamp in use when said sensor detects failure of said lamp in use, and a means responsive to said sensor for latching said array of redundant lamps in position except when said sensor detects a failed lamp.

19. The image processor of claim 18, wherein said redundant lamps comprise arc lamps.

20. The image processor of claim 18, wherein said latching means comprises a register pin for being received in a respective one of a plurality of apertures in a part of said carousel.