Optical-digital method and processor for pattern recognition

• US 5,953,452 A
• Filed: 11/05/1992
• Issued: 09/14/1999
• Est. Priority Date: 11/05/1992
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Shukla, Oodaye B., Boone, Bradley G.
• Primary Examiner(s): CHANG, JON CARLTON
• Application Number:
  US07/972,279
• Time in Patent Office: 2,504 Days
• Field of Search: 382/42, 382/32, 382/16, 382/19, 382/14, 382/22, 382/25, 382/278, 382/212, 382/199, 382/214, 359/561, 359/227, 359/230, 359/232, 359/234, 359/236, 359/618, 359/619, 364/822
• US Class Current: 382/199
• CPC Class Codes: G06V 10/88 Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters

Abstract

The invention is an optical-digital method and processor which uses micro-optical lenslet arrays and fixed masks to implement an angular correlation algorithm and the Hough transform for extracting amplitude and geometric features from objects embedded in video imagery. The optical-digital processor can be interfaced to a variety of sensors and can be used to classify objects when used in conjunction with a neural network.

Claims

1. A method for extracting the boundary of an object in a sensor input image comprising the steps of:

overlapping a slit and the object in the sensor input image;

rotating the slit relative to the object, the slit thereby sampling the entire boundary of the object; and

calculating for each rotation position an area of overlap of the slit and the object versus an angle between the slit and the object;

wherein an algorithm for calculating the area of overlap versus the angle comprises;

##EQU4## where rect r/r_rect (θ

'"'"'+θ

)! is the slit rotated by an angle θ

, and rect r/r(θ

'"'"')! is the object in the sensor input image.

2. An optical-digital signal processor for extracting a feature from an object in a sensor input image, the signal processor comprising:

an optical processor for extracting the boundary of the object, wherein the optical processor comprises;

a multi-lenslet array for replicating the sensor input image;

a fixed mask containing a series of rotated slits for passing the replicated sensor input images therethrough; and

a detector array for receiving the replicated sensor input images and for integrating the superposition of each replicated sensor input image and the corresponding fixed mask slit; and

a digital processor for calculating a feature of the object using the extracted boundary of the object.

3. The signal processor as recited in claim 2, wherein the optical processor further comprises a means for generating the Hough transform of the object.

4. The signal processor as recited in claim 3, wherein the Hough transform generating means comprises a means for calculating an annular correlation.

5. The signal processor as recited in claim 4, wherein the annular correlation calculating means comprises a second fixed mask containing a plurality of annuli having different diameters for passing the replicated images therethrough.

6. The signal processor as recited in claim 2, further comprising a zoom lens preceding the optical processor.

7. The signal processor as recited in claim 6, further comprising a microchannel plate for receiving the sensor input image from the zoom lens and forming a real image.

8. The signal processor as recited in claim 2, further comprising an optical interface for transferring the sensor input image to the optical processor.

9. The signal processor as recited in claim 8, wherein the optical interface comprises a means for creating a displayed image.

10. The signal processor as recited in claim 9, wherein the creating means comprises a video display.

11. The signal processor as recited in claim 10, wherein the optical interface further comprises

a collimating lens.

12. The signal processor as recited in claim 2, further comprising a neural network for classifying the object using the calculated feature.

13. The signal processor as recited in claim 2, wherein the slits and the object are concentric.

14. The signal processor as recited in claim 2, wherein the slits are radial slits.

15. A method for extracting the boundary of an object in a sensor input image comprising the steps of:

overlapping a slit and the object in the sensor input image;

rotating the slit relative to the object, the slit thereby sampling the entire boundary of the object;

calculating for each rotation position an area of overlap of the slit and the object versus an angle between the slit and the object; and

generating a Hough transform of the object comprising calculating an annular correlation.

16. An optical-digital signal processor for extracting a feature from an object in a sensor input image, the signal processor comprising:

a video display;

a collimating lens;

a zoom lens;

a microchannel plate for receiving the sensor input image from the zoom lens and forming a real image;

a multi-lenslet array for replicating the sensor input image;

two fixed masks, a first mask containing a first pattern comprising a series of rotated radial slits and a second mask containing a second pattern comprising a plurality of annuli having different diameters, the first and second fixed masks for passing the replicated images therethrough and extracting the boundary of the object;

a detector array for receiving the replicated images and for integrating the superposition of each replicated image and the corresponding fixed mask patterns; and

a digital processor for calculating a feature of the object using the extracted boundary of the object.