US 4,360,798 A · Portable laser scanning arrangement for and method of evaluating and validating bar code symbols

Abstract

Laser light reflected from a bar code symbol pattern is detected by a photodetector mounted in a portable scanning head of a laser scanning system. By selecting appropriate threshold values on the analog signal generated by the photodetector, the analog signal is converted to a series of pulses, each pulse width accurately corresponding to the width of a bar from the scanned pattern. A plurality of functions can be determined from the series of pulses, each function being independently selected by keyboard entry from the head, displayed on the head, and/or recorded by a printer remote from the head. Single line or multiple line scans in two orthogonal directions relative to the pattern may be selected. A bimorph or speaker-type oscillatory element may be utilized as a miniature scanning element. Circuitry for synchronizing scanning along both axes, and for generating a signal to drive the bimorph in a uniform, constant velocity manner is also disclosed.

Claims12

Dependent claims

A noise-resistant method of processing an electrical analog time-varying signal indicative of the detected intensity of the light reflected from a bar code symbol upon directing a laser light beam on the latter, said method comprising the steps of:

(a) establishing respective upper threshold levels at a fixed predetermined voltage value which is below and independent of the magnitudes of the respective peaks of the analog signal;
(b) establishing respective lower threshold levels at a fixed predetermined voltage value which is above and independent of the magnitudes of the respective valleys of the analog signal;
and
(c) generating in response to establishing said upper and lower threshhold levels a series of digital pulses, each successive pulse having a time period which corresponds to the width of each successive bar of the symbol to be scanned.

1 more element

In a laser scanning system of the type having means for directing a laser light beam towards a bar code symbol for reflection therefrom, and means for detecting the intensity of the light reflected from the symbol and for generating an electrical analog time-varying signal indicative of the detected intensity of the reflected light, a noise-resistant signal processing circuit for processing the analog signal to thereby determine the bar widths of the bar code symbol to be scanned, said signal processing circuit comprising:

(a) generator means for generating a series of digital pulses, each successive pulse having a time period which generally corresponds to the width of each successive bar, except for the very first bar, of the symbol to be scanned;
(b) gating means for generating a gating pulse having a time period which substantially equals the sum of all the individual time periods of the series of digital pulses as well as the time period of the digital pulse which corresponds to the very first bar of the symbol to be scanned;
and
(c) means for combining the series of digital pulses with the gating pulse to generate an output signal train of digital pulses each corresponding to the respective widths of all of the bars of the symbol to be scanned.

1 more element

(a) means for establishing respective upper threshhold levels at a fixed predetermined voltage value which is below and independent of the magnitudes of the respective peaks of the analog signal;
(b) means for establishing respective lower threshhold levels at a fixed predetermined voltage value which is above and independent of the magnitudes of the respective valleys of the analog signal;
and
(c) means responsive to both of said threshhold-establishing means for generating a series of digital pulses, each successive pulse having a time period which corresponds to the width of each successive bar of the symbol to be scanned.

1 more element

Dependencies are inferred from the claim text.

Portable laser scanning arrangement for and method of evaluating and validating bar code symbols

Life of this patent

Portable laser scanning arrangement for and method of evaluating and validating bar code symbols

Life of this patent

Abstract

Claims12