Thomas B Chisholm

US Patent:

51499487, Sep 22, 1992

Filed:

Jul 16, 1990

Appl. No.:

7/553859

Inventors:

Thomas J. Chisholm - Milton MA

Assignee:

Computer Identics - Canton MA

International Classification:

G06K 710

US Classification:

235462

Abstract:

An improved bar code reading system for reading bar codes having a wide range of intensity of reflected radiation includes repeatedly scanning a beam of radiation across a bar code containing bar and space code elements; monitoring the number of scans of the beam across the bar code; sensing the radiation reflected from the bar code and providing a bar code signal representative thereof; the bar code signals are amplified at one of a number of different gains, and a different gain is selected for each scan. Also disclosed is an improved bar code reader system for reading bar codes of diffuse bar elements and specular spaced elements. A bar code is illuminated with radiation polarized in a first direction at an acute angle to the surface of the bar code and generally parallel to the bars and spaces for diverting radiation reflected from the specular spaces away from the scanner and for directing a portion of the radiation reflected from specular imperfections in the bars to the receiver; a crossed-polarizer blocks substantially all the radiation directed back to the scanner from the specular spaces and the specular imperfections in the bar, and transmits to the scanner substantially all the diffuse radiation from the bars and a portion of the return of the specular imperfections of the bars.

US Patent:

57010030, Dec 23, 1997

Filed:

Oct 22, 1996

Appl. No.:

8/735421

Inventors:

Thomas J. Chisholm - Milton MA
Gary Richard - Lincoln RI
Alexander Rysin - Stoughton MA

Assignee:

Computer Identics Corporation - Canton MA

International Classification:

G01J 132

US Classification:

250205

Abstract:

An intensity compensated scanning system includes laser means for providing a laser beam; scanner means for sweeping the laser beam in an arcuate path across a surface to be scanned; means for sensing the return laser beam reflected from the surface to be scanned; means for quantifying the decrease in the intensity of the return laser beam at the scan extremity portion relative to the intermediate scan portion; and means responsive to the means for quantifying for varying the power to the laser means at the scan extremity portion relative to that at the intermediate scan portion for balancing the intensity of the return laser beam reflected from the surface to the means for sensing.

US Patent:

51773465, Jan 5, 1993

Filed:

Dec 13, 1989

Appl. No.:

7/450243

Inventors:

Thomas J. Chisholm - Milton MA

Assignee:

Computer Identics - Milton MA

International Classification:

G06K 710
G02F 101
H01J 4014

US Classification:

235462

Abstract:

A bar code reader system for reading bar code labels with highly specular spaces and bars with low contrast. The bar code label is illuminated with radiation polarized in a first direction. The radiation polarized in a first direction reflected from the bar code label is received and blocked by means of cross polarization. This blocked radiation is representative of the spaces and other radiation passing through unblocked is representative of the bars. The resulting radiation pattern representative of the bars and spaces is consequently inverted from its initial state into a secondary state. The radiation image passed by the block is detected in order to generate a signal representative of the bars and spaces. The strength of the signal representing the spaces is substantially diminished in intensity. The widths of the areas representing the bars and spaces is determined, and the widths representing the bars and spaces are interpreted to obtain the information of the bar code.