Method of optical character recognition

• US 4,864,628 A
• Filed: 05/14/1987
• Issued: 09/05/1989
• Est. Priority Date: 08/26/1983
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Scott, Warner C.
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US07/052,192
• Time in Patent Office: 845 Days
• Field of Search: 382/21, 382/22, 382/25, 382/28, 382/60
• US Class Current: 382/197
• CPC Class Codes: G06V 30/10 Character recognition
• CPC Class Codes: G06V 30/182 by coding the contour of the pattern

Abstract

A method for recognizing and providing an output corresponding to a character is disclosed. The character is received by an imager, digitized and transmitted to a buffer memory. Data in the buffer memory is read in a sequence which circumnavigates the test character. Only data representative of the periphery of the character are read. During the circumnavigation character parameters, such as, height, width, perimeter, area, calipers, programmable penetrators and waveform are determined. The character parameters are compared with reference character parameters and the ASCII code for the reference character which matches the character is provided as an output.

Claims

1. The method of character recognition comprising:

(a) scanning a character with an imager,

(b) generating data in the imager representative of the character and storing said data in a memory,

(c) generating character parameter date using only data representative of the periphery of said character, said parameter data including data corresponding to the height, width, distance around the perimeter area with the periphery of the character, a series of contour numbers representative of the shape of the contour and a series of caliper numbers representing the difference between the periphery of said character at any one point along a side and the maximum extension of said character along that same side; and

,

(d) comparing said parameter data with reference character parameter data and providing an output indicative of which reference character corresponds to said character.

2. The method according to claim 1 wherein the data representative of the periphery of said character is read in a sequence which circumnavigates said character.

3. The method of claim 2 wherein said reading sequence is comprised of:

(a) reading cells until a black cell is read,

(b) storing the address of said first black cell as a reference cell,

(c) determining an initial compass heading number for said first black cell,

(d) reading a second cell at address location X1,Y1, with respect to said reference cell and storing the address of said second cell as the reference cell when said second cell is black,

(f) reading a third cell at address X2,Y2 with respect to said reference cell when said second cell is white and storing the address of said third cell as the reference cell when said third cell is black,

(g) retaining said first cell as the reference cell when both said second and third cells are white,

(h) determining a current compass heading number based on the relationship between sequentially determined reference cells,

(i) repeating steps d-h until said first black cell becomes the reference cell and said current compass heading number is the initial compass heading number.

4. The method of claim 3 wherein the relationship between the reference cell X1, Y1 and X2,Y2 is determined by the current compass heading number.

5. The method according to claim 4 wherein one of said parameters is the perimeter of said character and it is determined using the method comprising:

(a) incrementing a first counter PS whenever the second cell X1,Y1 is white and the third cell is black,

(b) incrementing a second counter PN whenever the second cell is black or whenever both second and third cells are white,

(c) providing an output as an approximation of the perimeter using the formula

space="preserve" listing-type="equation">PER=PS+(K*PN)

when said reading sequence is completed.

6. The method according to claim 5 wherein one of said parameters is the area within the periphery of said character and it is determined using the method comprising:

(a) incrementing a DPL register each time said compass heading number represents a first direction,

(b) incrementing a DPA register by the value of said DPL register each time said compass heading number represents a second direction,

(c) decrementing said DPL register by one each time said compass heading number represents a third direction,

(d) decrementing said DPA register by the value of said DPL register each time said compass heading number represents a fourth direction; and

(e) providing the output of the DPA register as the area within the periphery of said character when said reading sequence is completed.

7. The method according to claim 5 wherein one of said parameters is the height of the character and it is determined using the method comprising:

(a) determining the difference between the maximum and minimum Y encountered for said character during said reading sequence and adding one.

8. The method according to claim 4 wherein one of said parameters is the width of said character and it is determined using the method comprising:

(a) determining the difference between the maximum and minimum X encountered for said character during said reading sequence and adding one.

9. The method according to claim 3 wherein a series of contour numbers representative of the contour of the character is generated.

10. The method according to claim 9 wherein each number in said series of contour numbers is comprised of the angle of the vector sum of the most recent N compass heading numbers.

11. The method according to claim 10 wherein said angle of the vector sum is measured in units and a complete circle is comprised of 256 units.

12. The method according to claim 11 wherein said angle is determined using a lookup table in conjunction with said vector sum of compass heading numbers.

13. The method according to claim 12 wherein N equals 6.

14. The method according to claim 13 wherein N equals 2 and a contour number is determined only for every other reference cell.