CHARACTER RECOGNITION APPARATUS

• US 3,803,553 A
• Filed: 06/14/1972
• Issued: 04/09/1974
• Est. Priority Date: 06/14/1972
• Status: Expired due to Term

• Current Assignee: Kazuo Nakata, Yasuaki Nakano
• Original Assignee: Kazuo Nakata, Yasuaki Nakano
• Inventors: Nakano, Yasuaki, Nakata, Kazuo
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/262,507
• Time in Patent Office: 664 Days
• Field of Search: 340/146.3R,146.3D,146.3F,146.3S
• US Class Current: 382/206
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/18095 Summing image-intensity values; Projection and histogram analysis

Abstract

Character recognition apparatus wherein projection patterns obtained by projecting a density distribution of a printed or typed character on two orthogonally-intersecting axes are compared with a number of standard projection patterns obtained by a similar method and separately recorded, and the standard information at the highest degree of similarity is selected as the recognized character.

Claims

1. Character recognition apparatus comprising:

means for projecting the density distribution of an unknown input pattern taken along at least two intersecting axes of the pattern to obtain at least two input projection patterns, memory means for storing predetermined standard patterns in the form of the standard projection patterns thereof taken along the same axes as the unknown input pattern, distance calculating circuit means for comparing the standard projection patterns stored in said memory means sequentially with at least one input projection pattern related to the density of a character along a selected projection axis to evaluate the degree of similarity between said unknown input pattern and each of said standard patterns, including selection circuit means for selecting the standard pattern having the maximum degree of similarity corresponding to the unknown input pattern, and output circuit means responsive to said selection circuit means for providing identification of the corresponding standard pattern as a recognized output, including means for decomposing said unknown input pattern into a plurality of meshes, means for generating signals corresponding to each mesh, means for quantizing said signals into binary signals and means for accumulating said binary signals in a predetermined direction.

2. Character recognition apparatus as defined in claim 1 wherein said distance calculating circuit means further includes shift register means connected to said memory means for sequentially storing each standard pattern signal obtained from said memory device corresponding to said selected projection axis and control means for shifting the position of said standard pattern signal in said shift register means.

3. Character recognition apparatus as defined in claim 2 wherein said distance calculating circuit means further includes comparison means for measuring the degree of similarity between each standard projection pattern stored in said shift register means and said input projection pattern.

4. Character recognition apparatus comprising:

means for projecting the density distribution of an unknown input pattern taken along at least two intersecting axes of the pattern to obtain at least two input projection patterns, memory means for storing predetermined standard patterns in the form of the standard projection patterns thereof taken along the same axes as the unknown input pattern, distance calculating circuit means for comparing the standard projection patterns stored in said memory means sequentially with at least one input projection pattern related to a selected projection axis to evaluate the degree of similarity between said unknown input pattern and each of said standard patternS, including selection circuit means for selecting the standard pattern having the maximum degree of similarity corresponding to the unknown input pattern, and output circuit means responsive to said selection circuit means for providing identification of the corresponding standard pattern as a recognized output, wherein said comparison means includes a plurality of subtractor circuits each having a first input receiving signals of said input projection pattern and a second input connected to said shift register means, a plurality of squaring circuits connected to said subtractor circuits for squaring the outputs thereof, and an adder circuit for adding the outputs of said squaring circuits so as to produce a signal value equal to the sums of the squares of the differences between said input projection pattern and each standard projection pattern, wherein said distance calculating circuit means further includes shift register means connected to said memory means for sequentially storing each standard pattern signal obtained from said memory device corresponding to said selected projection axis and control means for shifting the position of said standard pattern signal in said shift register means, wherein said distance calculating circuit means further includes comparison means for measuring the degree of similarity between each standard projection pattern stored in said shift register means and said input projection pattern.

5. Character recognition apparatus as defined in claim 4 wherein said selection circuit means includes means for storing the minimum value of the output of said adder circuit and said output circuit means includes output means connected to said memory means and said selection circuit means for storing the identity of the standard pattern corresponding to said stored minimum value.

6. Character recognition apparatus as defined in claim 5 wherein said selection circuit means includes a subtractor circuit having one input connected to the output of said adder circuit, an analog memory circuit having an output connected to a second input of said subtractor circuit, a selectively operable switch for connecting the output of said adder circuit to the input of said analog memory circuit, and switch operating means for operating said switch in response to the output of said subtractor circuit when the output of said adder circuit is less than the value stored in said analog memory circuit, thereby replacing the value stored in said analog memory circuit with the output of said adder circuit.

7. Character recognition apparatus as defined in claim 6 wherein said switch operating means includes a threshold circuit connected to the output of said subtractor circuit for providing an output when the output of said subtractor circuit exceeds a fixed value, a differentiation circuit connected to the output of said threshold circuit, and a delay circuit connected to the output of said differentiation circuit and said switch.

8. Character recognition apparatus as defined in claim 7 wherein said output means includes a plurality of address registers, a plurality of gates selectively connecting said address registers to said memory means and being actuated by the output of said delay circuit.

9. Character recognition apparatus as defined in claim 3 wherein said comparison means includes means for producing a signal value equal to the sums of the squares of the differences between said input protection pattern and each standard projection pattern.

10. Character recognition apparatus as defined in claim 3 wherein said axes on which said input pattern is projected are orthogonally intersecting axes.

11. Character recognition apparatus as defined in claim 3 wherein said means for projecting the density distribution of said input pattern comprises a scanning type photoelectric conversion pickup tube, an integrator circuit connected to the output of said pickup tube, a sampling circuit for sampling the output of said integrator circuit each horizontal scaNning period of said pickup tube, and a sample hold circuit for storing the sampled signals for a fixed period of time.

12. Character recognition apparatus comprising:

means for projecting the density distribution of an unknown input pattern taken along at least two intersecting axes of the pattern to obtain at least two input projection patterns, memory means for storing predetermined standard patterns in the form of the standard projection patterns thereof taken along the same axes as the unknown input pattern, distance calculating circuit means for comparing the standard projection patterns stored in said memory means sequentially with at least one input projection pattern related to a selected projection axis to evaluate the degree of similarity between said unknown input pattern and each of said standard patterns, including selection circuit means for selecting the standard pattern having the maximum degree of similarity corresponding to the unknown input pattern, and output circuit means responsive to said selection circuit means for providing identification of the corresponding standard pattern as a recognized output, wherein said distance calculating circuit means comprises switch circuit means for selecting one of the two input projection patterns, calculating circuit means connected to said switch circuit means for calculating the degree of similarity between the selected input projection pattern, ordering circuit means for rearranging the standard patterns in the order of the higher degrees of similarity in said calculating circuit means, and first and second register means for storing character addresses and degrees of similarity of said rearranged standard patterns.

13. Character recognition apparatus as defined in claim 12 wherein the two input projection patterns are horizontal and vertical projection patterns.

14. Character recognition apparatus as defined in claim 12 wherein said distance calculating circuit means further includes address converter circuit means for converting the addresses of characters into address signals for said memory means in which the standard projection patterns of said characters are stored, logical code adder circuit means for selecting the projection axis of said standard projection patterns, address selection circuit means for selecting the standard pattern information of said memory means by outputs of said address converter circuit means and said code adder circuit means, register means for recording the selected standard pattern information and comparison circuit means for calculating degrees of similarity between outputs successively read out from said register means and said input projection pattern.

15. Character recognition apparatus as defined in claim 14 wherein said degree of similarity calculated by said distance calculating circuit is determined by values of sums of squares of differences between said input projection pattern and said standard projection pattern, and wherein said calculating circuit means for evaluating said degree of similarity comprises a plurality of subtractor circuits for evaluating said difference between said two patterns, a plurality of square circuits for squaring the outputs of said subtractor circuits, and a circuit for adding the squared values.

16. Character recognition apparatus as defined in claim 14 wherein said register means is composed of a shift register means and wherein said standard pattern information of the specific characters read out from said memory means are sequentially moved within said shift register to make corrections of position of the data stored therein.