OPTICAL CHARACTER RECOGNITION APPARATUS

• US 3,622,988 A
• Filed: 09/19/1969
• Issued: 11/23/1971
• Est. Priority Date: 09/19/1969
• Status: Expired due to Term

• Current Assignee: Henry John Caulfield, William T. Maloney
• Original Assignee: Henry John Caulfield, William T. Maloney
• Inventors: Caulfield, Henry John, Maloney, William T.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US04/859,449
• Time in Patent Office: 795 Days
• Field of Search: 340/146.3P
• US Class Current: 382/210
• 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

An optical character recognition apparatus comprising a signal processor including a light source and lenses for directing a light beam through both a transparency of the character to be recognized and a holographic plate containing Fourier transform interference patterns representative of the respective characters, the plate being positioned in the frequency plane of the processor. A plurality of photodetectors are positioned in the output plane of the processor at the discrete correlation points of the individual characters. The output signal of each photodetector is weighted and polarized and applied to a plurality of linear summing devices such that the individual summing devices provide a maximum output in response to predetermined characters while the remaining summing devices simultaneously provide output signals of substantially lower magnitude.

Claims

1. A character recognition apparatus comprising a light source, means adapted to support an input character to be identified in the path of the light beam emitted from said source, mask means positioned to receive the light from said input character, said mask means containing a plurality of masks, each representative of a discrete character to be identified, photodetector means positioned to receive discrete light signals transmitted through said mask means for producing corresponding electrical output signals, each discrete light signal being representative of the degree of similarity between said input character and a respective mask of said plurality of masks, algebraic summing means for performing N summations of the totality of photodetector output signals to provide N sum signals, and means for weighting each photodetector output signal, a prescribed weight being assigned to each pHotodetector output signal for each summation such that N summations of the one photodetector output signal representative of correspondence between one of said masks and said input character with the total of the other N-1 photodetector output signals produces one sum signal which is a maximum and N-1 sum signals which are less than the respective photodetector output signals representative of the similarity of the other masks to said input character thereby providing for the difference between said one sum signal and the largest of said N-1 sum signals to be greater than the difference between said one photodetector output signal and any of said other N-1 photodetector output signals.

2. The apparatus of claim 1 wherein said photodetector means comprises a plurality of photodetectors each being located at a predetermined point whereat said discrete light signals are produced.

3. The apparatus of claim 2 wherein the mask means is a holographic plate in which the individual masks are formed by respective interference patterns representative of the characters to be identified.

4. The apparatus of claim 3 wherein the individual masks are multiplexed in a space-sharing manner.

5. The apparatus of claim 2 wherein the summing means comprises a plurality of summing devices and each photodetector is connected to all of said summing devices.

6. The apparatus of claim 5 wherein the weighting means comprises a plurality of elements arranged such that an individual element couples each photodetector to each summing device.

7. The apparatus of claim 1 wherein the input character to be identified is represented by a transparency thereof and the light beam incident on the transparency is collimated and further including lens means positioned between the transparency and mask means such that the mask means is located in the rear focal plane of said lens means, and additional lens means positioned on the other side of said mask means such that the mask means is located in the front focal plane of said additional lens means.

8. The apparatus of claim 7 wherein said photodetector means comprises a plurality of photodetectors each being located at a predetermined point whereat said discrete light signals are produced.

9. The apparatus of claim 8 wherein the mask means is a holographic plate in which the individual masks are formed by respective interference patterns representative of the characters to be identified.

10. The apparatus of claim 9 wherein the individual masks are multiplexed in a space-sharing manner.

11. The apparatus of claim 10 wherein the summing means comprises a plurality of summing devices and each photodetector is connected to all of said summing devices.

12. The apparatus of claim 11 wherein the weighting means comprises a plurality of variable impedance elements arranged such that an individual element couples each photodetector to each summing device.

13. The apparatus of claim 12 wherein the summing devices operate to perform a linear summation.

14. The apparatus of claim 13 further including means for making the signals applied to the summing means alternating in nature.