CHARACTER RECOGNITION SYSTEMS AND APPARATUS

• US 3,599,147 A
• Filed: 09/11/1968
• Issued: 08/10/1971
• Est. Priority Date: 09/12/1967
• Status: Expired due to Term

• Current Assignee: Ian Leifer, Rogers Gordon Leonard, Stephens Noel W F
• Original Assignee: Ian Leifer, Rogers Gordon Leonard, Stephens Noel W F
• Inventors: ROGERS GORDON LEONARD, Leifer, Ian, STEPHENS NOEL W F
• Application Number:
  US04/758,969
• Time in Patent Office: 1,063 Days
• 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

Method of and apparatus for effecting recognition of patterns, especially written or printed characters in which a representation of the pattern in incoherent light, moving electrons or other charged particles is caused to cast shadows of a grating on to a plurality of photoelectric or equivalent sensing devices thereby to derive a number of electric signals representing respectively different Fourier coefficients of one or more spatial frequency components of the pattern and in which such derived signals are comparatively examined in logical circuit means to derive an output signal identifying the pattern.

Claims

1. A method of effecting recognition of a pattern which comprises the steps of:

causing a representation of the pattern in incoherent light, moving electrons or other charged pArticles to cast shadows of at least one grating of straight opaque lines and transparent interline spaces on to a plurality of appropriately positioned photoelectric or equivalent sensing devices thereby to derive a plurality of electric signals representing respective different Fourier coefficients of one or more spatial frequency components of the pattern, causing said plurality to include a signal representing the phase of at least one of said Fourier coefficients, and then subjecting said plurality of signals to a comparative examination by means of a logical circuit network to derive an output signal indicating the identity of the represented pattern.

2. The method according to claim 1 in which a signal representing the zero frequency Fourier coefficient component is derived and applied to said logical network during said comparative examination.

3. The method according to claim 1 in which said pattern representation is caused to cast shadows of each of a plurality of gratings on to separate sensing devices.

4. The method according to claim 4 in which said plurality of gratings have different line and interline spacing dimensions.

5. The method according to claim 3 in which the respective line and spacing directions of said plurality of gratings are oriented at different angles.

6. The method according to claim 1 in which relative scanning movement is caused to occur between said pattern representation and said grating or gratings and/or said sensing devices.

7. The method according to claim 1 in which the effect of relative scanning movement between said pattern representation and said sensing devices is simulated by the use of additional masking grid means similar to said grating in front of said sensing devices, said masking grid means for each Fourier coefficient being subdivided into a plurality of sections having respectively different displacements relative to said grating and each controlling the pattern representation incident upon a separate sensing device, the different outputs from the sensing devices for each coefficient being processed substantially as described.

8. The method according to claim 1 in which the pattern is a written or printed character forming one of a defined finite set of characters.

9. The method according to claim 8 in which said pattern representation consists of the character illuminated by incoherent light.

10. The method according to claim 9 in which said pattern representation is derived by illumination of the character printed on a rough surface, such that, even if illuminated coherently, the light reflected from such surface has such random phase relationships as to have no systematic spatial coherence.

11. A method according to claim 9 in which said pattern representation is derived from illumination of a transparency thereof with incoherent light.

12. The method according to claim 11 in which said pattern representation is applied to light diffusing means.

13. The method according to claim 9 in which said pattern representation is derived from the visual light output from the fluorescent screen of a cathode-ray tube, image converter tube or the like.

14. The method according to claim 8 in which said pattern representation as applied at least to said grating consists of a stream of electrons.

15. The method according to claim 14 in which said stream of electrons are derived from excitation of a photoemissive surface in response to a light pattern.

16. Apparatus for effecting recognition of a pattern, e.g. a character, which comprises:

means for forming a representation of said pattern in incoherent light, moving electrons on other charged particles, a grating of straight opaque lines and transparent interline spaces, means for directing said pattern representation on to one side of said grating, a plurality of photoelectric or equivalent sensing devices located relative to said grating to receive light, electrons or other charged particles from said repResentation passing through said interline spaces of said grating, said positions being so chosen that the signal outputs from said sensing devices represent respectively different Fourier coefficients of one or more spatial frequency components of the pattern, means for deriving a signal output representing the phase of at least one of said Fourier coefficients, and a logical circuit network connected to be supplied with said outputs from said sensing devices and said output from said means for deriving a phase representative signal and adapted by comparative examination of said outputs to provide an output signal indicating the identity of said represented pattern.

17. Apparatus according to claim 16 which includes means for deriving a signal representing the zero frequency Fourier coefficient components, said further zero frequency component signal being arranged also to be applied to said logical circuit network for use in said comparative examination.

18. Apparatus according to claim 16 in which said grating comprises a plurality of grating sections of different form each associated with at least one of said sensing devices.

19. Apparatus according to claim 18 in which said grating sections have different line and interline spacing dimensions.

20. Apparatus according to claim 18 in which the respective line and spacing directions of said different grating sections are oriented at different angles.

21. Apparatus according to claim 16 in which said representation forming means comprise a source of incoherent light arranged to illuminate a rough surface bearing a light reflecting image of said pattern thereon.

22. Apparatus according to claim 16 in which said representation forming means comprise a transparency of said pattern and a source of incoherent light directed to pass light therethrough.

23. Apparatus according to claim 22 which includes a light diffusing means arranged to be illuminated by the light emerging from said transparency.

24. Apparatus according to claim 16 in which said representation forming means comprise a fluorescent screen forming part of an electron-optical device such as a cathode-ray tube, image converter tube or the like.

25. Apparatus according to claim 16 in which said representation forming means comprise an electron-optical device for providing a stream of electrons issuing from an area shaped in accordance with said pattern.

26. Apparatus according to claim 16 which includes means for causing relative scanning movement between said pattern representation and said grating and/or said sensing devices.

27. Apparatus according to claim 26 in which said scanning means include a mechanical device, such as a motor, arranged to cause movement of a light reflecting surface such as a mirror or prism.

28. Apparatus according to claim 24 which includes electron beam deflecting means operable upon the electron beam of said cathode-ray tube or other electron optical device for causing relative scanning movement between said pattern representation and said grating and/or sensing means.

29. Apparatus according to claim 25 in which said electron optical device includes an internal grid structure arranged to operate as said grating.

30. Apparatus according to claim 16 in which a masking grid having a line spacing and orientation similar to that of said grating or associated grating section is disposed in front of said sensing device or devices.

31. Apparatus according to claim 30 in which, for each coefficient said masking grid is subdivided into a plurality of sections each displaced laterally by different amounts relative to the related shadowing grating and each controlling the pattern representation incident upon a separate sensing device, the respective outputs from said sensing devices being arranged for processing substantially as described to simulate the effect of relative scanning movement between said pattern representation and said sensing devices.