Bar code reading system and method
First Claim
1. A method of reading a bar code label, said method comprising the steps of:
- (a) producing an analog signal in response to scanning of the bar code label, said analog signal including signals representative of amounts of light reflected from bars and spaces of the bar code label, the widths of said bars and spaces being representative of whether said bars and spaces represent first or second logical states;
(b) amplifying and shaping said analog signal to produce a raw data signal including a plurality of pulses, the durations of consecutive ones of said pulses corresponding to the widths of consecutive bars, respectively, of said bar code label, the durations of consecutive intervals between said pulses corresponding to widths of consecutive ones of said spaces, respectively, said bar code label including at least one character including a plurality of said bars and spaces;
(c) measuring the durations of each of a plurality of said pulses and intervals of at least said one character of said bar code label to produce a plurality of digital duration numbers representative of said plurality of durations, respectively, and storing said plurality of digital duration numbers;
(d) computing a first reference number;
(e) comparing each of said digital duration numbers to said first reference number and producing a first binary number having a plurality of bits corresponding, respectively, to the bars and spaces of said character, each of said bits being equal to said first logical state if a corresponding one of said digital duration numbers is less than said first reference number, each of said bits being equal to said second digital state if a corresponding one of said digital duration numbers is greater than said first reference number;
(f) determining if said first binary number is an acceptable number in accordance with a predetermined criteria, and decoding said first binary number, if it is acceptable, to determine what said character is; and
(g) adjusting the value of said first reference number by a predetermined amount if said first binary number is not acceptable and repeating steps (e) and (f).
2 Assignments
0 Petitions
Accused Products
Abstract
A bar code reading system having a wand that detects variations in light reflected by bars and spaces of the label produces a sequence of corresponding pulses and intervals as the wand scans the label. The entire sequence of pulses and intervals is input to a microprocessor system which produces corresponding digital duration numbers. The microprocessor system computes a reference number for a first character of the label and compares each digital duration number of the character to the reference number to compute a binary number with bits that are a "one" or a "zero" according to whether corresponding digital internal numbers exceed or are less than the reference number. If the number of "ones" in the binary number is too low or too high, the microprocessor decreases or increases the reference time, compares the digital duration number with the adjusted reference number, and re-determines if the resulting value of the binary number has the correct number of "ones". This compensates for variations in scan speed over different characters of the label.
19 Citations
20 Claims
-
1. A method of reading a bar code label, said method comprising the steps of:
-
(a) producing an analog signal in response to scanning of the bar code label, said analog signal including signals representative of amounts of light reflected from bars and spaces of the bar code label, the widths of said bars and spaces being representative of whether said bars and spaces represent first or second logical states; (b) amplifying and shaping said analog signal to produce a raw data signal including a plurality of pulses, the durations of consecutive ones of said pulses corresponding to the widths of consecutive bars, respectively, of said bar code label, the durations of consecutive intervals between said pulses corresponding to widths of consecutive ones of said spaces, respectively, said bar code label including at least one character including a plurality of said bars and spaces; (c) measuring the durations of each of a plurality of said pulses and intervals of at least said one character of said bar code label to produce a plurality of digital duration numbers representative of said plurality of durations, respectively, and storing said plurality of digital duration numbers; (d) computing a first reference number; (e) comparing each of said digital duration numbers to said first reference number and producing a first binary number having a plurality of bits corresponding, respectively, to the bars and spaces of said character, each of said bits being equal to said first logical state if a corresponding one of said digital duration numbers is less than said first reference number, each of said bits being equal to said second digital state if a corresponding one of said digital duration numbers is greater than said first reference number; (f) determining if said first binary number is an acceptable number in accordance with a predetermined criteria, and decoding said first binary number, if it is acceptable, to determine what said character is; and (g) adjusting the value of said first reference number by a predetermined amount if said first binary number is not acceptable and repeating steps (e) and (f). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A method of reading a bar code label, said method comprising the steps of:
-
(a) producing an analog signal in response to scanning of the bar code label, said analog signal including signals representative of amounts of light reflected from bars and spaces of the bar code label, the widths of said bars and spaces being representative of whether said bars and spaces represent first or second logical states; (b) amplifying and shaping said analog signal to produce a raw data signal including a plurality of pulses, the durations of consecutive ones of said pulses corresponding to the widths of consecutive bars, respectively, of said bar code label, the durations of consecutive intervals between said pulses corresponding to widths of consecutive ones of said spaces, respectively, said bar code label including at least one portion including a plurality of said bars and spaces; (c) measuring the durations of each of a plurality of said pulses and intervals of at least said one portion of said bar code label to produce a plurality of digital duration numbers representative of said plurality of durations, respectively, and storing said plurality of digital duration numbers; (d) computing a first reference number; (e) comparing each of said digital duration numbers to said first reference number and producing a first binary number having a plurality of bits corresponding, respectively, to the bars and spaces of said portion, each of said bits being equal to said first logical state if a corresponding one of said digital duration numbers is less than said first reference number, each of said bits being equal to said second logical state if a corresponding one of said digital duration numbers is greater than said first reference number; (f) determining if said first binary number is an acceptable number in accordance with a predetermined criteria, and decoding said first binary number, if it is acceptable, to determine what said portion represents; and (g) adjusting the value of said first reference number by a predetermined amount if said first binary number is not acceptable and repeating steps (e) and (f).
-
-
12. A system for reading a bar code label, said system comprising in combination:
-
(a) means for producing an analog signal in response to scanning of the bar code label, said analog signal including signals representative of amounts of light reflected from bars and spaces of the bar code label, the widths of said bars and spaces being representative of whether said bars and spaces represent first or second logical states; (b) means for amplifying and shaping said analog signal to produce a raw data signal including a plurality of pulses, the durations of consecutive ones of said pulses corresponding to the widths of consecutive bars, respectively, of said bar code label, the durations of consecutive intervals between said pulses corresponding to widths of consecutive ones of said spaces, respectively, said bar code label including at least one character including a plurality of said bars and spaces; (c) means for measuring the durations of each of a plurality of said pulses and intervals of at least said one character of said bar code label to produce a plurality of digital duration numbers representative of said plurality of durations, respectively, and storing said plurality of digital duration numbers; (d) means for computing a first reference number; (e) means for comparing each of said digital duration numbers to said first reference number and producing a first binary number having a plurality of bits corresponding, respectively, to the bars and spaces of said character, each of said bits being equal to said first logical state if a corresponding one of said digital duration numbers is less than said first reference number, each of said bits being equal to said second logical state if a corresponding one of said digital duration number is greater than said first reference number; (f) means for determining if said first binary number is an acceptable number in accordance with a predetermined criteria, and decoding said first binary number, if it is acceptable, to determine what said character is; and (g) means for adjusting the value of said first reference number by a predetermined amount if said first binary number is not acceptable. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
-
Specification