SYMBOL RECOGNITION SYSTEM, PARTICULARLY FOR ALPHA-NUMERIC CHARACTERS UTILIZING ELECTRO-OPTICAL TECHNIQUES WITH NONCOHERENT LIGHT

• US 3,644,889 A
• Filed: 04/23/1970
• Issued: 02/22/1972
• Est. Priority Date: 05/06/1969
• Status: Expired due to Term

• Current Assignee: Claude Skenderoff, Jean-Pierre Bouron
• Original Assignee: Claude Skenderoff, Jean-Pierre Bouron
• Inventors: Bouron, Jean-Pierre, Skenderoff, Claude
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/031,276
• Time in Patent Office: 670 Days
• Field of Search: 340/146.3 235/181 250/219CR,219DQ
• US Class Current: 382/212
• CPC Class Codes: G06E 3/003 forming integrals of products, e.g. Fourier integrals, Laplace integrals, correlation integrals; for analysis or synthesis of functions using orthogonal functions
• 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 multiplier, such as a fly'"'"''"'"'s eye lens projects a symbol to be recognized on a plurality of masks, which are subdivided into strips, each strip of the mask having predetermined transparencies and transmitting elementary sections of the image to associated photoelectric transducers which are connected to logic circuits identifying those of the transducers associated with any one strip which, conjointly, have an extreme (e.g., maximum) output signal. Preferably, optical or electrical weighting elements are interposed to optimize the outputs of the transducers associated with the various masks.

Claims

1. Symbol recognition system, particularly for alpha-numeric character recognition, utilizing optical correlation technique in real time with noncoherent light, comprising:

optical projecting means (1, 2, 3,

     4) providing a plurality of N of identical projected images (5.1, ...5-j, ...5-N) of a symbol (E, FIG.

     1) to be recognized located in a surrounding predetermined area (2);

a plurality of optical masks (M) each associated with a projected image and subdivided into a determined number P of juxtaposed rows of strips (B1,...Bp) parallel to a common direction (Y), said strips forming P elementary masks (Bk Mj) in front of each of said projected images to define elementary areas, each of said elementary masks containing, for identification, a partial pattern present in at least one ( theta i) of the n different symbols to be recognized ( theta l, ... theta i, ... theta n), said symbols each being located in said predetermined area to be subdivided in the same manner into P elementary areas, the partial pattern being present in at least one of the elementary areas of the row (k) of the elementary masks (Bk Mj), the N different elementary areas of a same row (k) of strips being weighted, all the elementary masks (Bk Mj) of a row (k) identifying by correlation the N different partial patterns of a row (k), the whole number of said elementary masks of a row (k) considered being at most equal to the number n of the different symbols, at least P of said elementary masks of rows 1 to P being utilized for the identification of a projected symbol;

a plurality of optical integrating lens means (6), and photoelectric transducer means (7), responsive to light through the lens means, each of said elementary masks (Bk Mj) forming (FIG.

     2) wiTh said optical integrating lens (6-jk) and a photoelectic transducer means (7k) an optical correlator for the elementary area of the corresponding projected area situated in front of said elementary masks; and

identifying circuits (9) connected to and supplied by said transducer means, said identifying circuits including threshold level comparison means.

2. System according to claim 1, wherein each of the photoelectric transducer means (7-jk) comprises a linear distribution of transducer elements (FIG. 2) along at least one line parallel to the common direction (Y) of said strips, said elements being symmetrically located with respect to the focus of the associated integrating lens (6-jk);

a peak detector (8-jk) connected to and supplied by said elements, said peak detector identifying the one of said transducer elements having an extreme output;

said identifying circuits being connected to and supplied by said peak detectors.

3. System according to claim 2, wherein said linear distribution (7-jk) comprises a line of odd-numbered elements, the central one of said elements being located at the focus of the associated integrating lens (6-jk).

4. System according to claim 2, wherein said elementary masks are matched to enable identification of any one of said symbols by comparing said corresponding extreme output signals to a common threshold level;

said identifying circuits comprising (FIG.

     6) threshold comparators;

analog digital converters (30-1,...30NP) supplied by said comparators, each of said threshold comparators comparing an extreme output applied to said common threshold level (31), and n logic summing circuits (32-l, ...32-n), one for each symbol to be identified, each of said logic summary circuits being supplied by at least P outputs of said converters.

5. System according to claim 14, including electrical weighting means (FIG. 4, I,J,K) comprising summing circuits (20), one for each symbol to be identified, each supplied by at least P outputs of said electrical weighting means which are respectively fed by P extreme output signals, each of said electrical weighting means introducing a multiplication factor of determined value and sign for the corresponding extreme output signals to it applied;

and n threshold comparators (21) supplied respectively by said summing circuits (20), each comparing the output signal of the corresponding summing circuit with a predetermined threshold level (Vk).