Bar code digitizer including a voltage comparator

United States Patent [w]

Boyd

[54] BAR CODE DIGITIZER INCLUDING A VOLTAGE COMPARATOR

[75] Inventor: Raymond J. Boyd, Bloomfield, N.Y.

[73] Assignee: PSC Inc., Webster, N.Y.

[21] Appl. No.: 841,807
[22] Filed: May 5, 1997

[51] Int. CI.6 G06K 7/10

[52] U.S. C I 235/462

[58] Field of Search 235/462; 327/68,

327/70, 72

[56] References Cited

U.S. PATENT DOCUMENTS

5,103,080 4/1992 Barkan 235/437

5,200,597 4/1993 Eastman et al 235/467

5,210,397 5/1993 Eastman 235/462

5,298,729 3/1994 Elliott et al 235/463

5,307,196 4/1994 Kinoshita 327/72

5,382,783 1/1995 Bremer 235/462

5,446,272 8/1995 Barkan 235/462

5,463,211 10/1995 Arends et al 235/462

lllllllllllllllllllllllllllllllllllllllllllllli

US005864129A [ii] Patent Number: 5,864,129 [45] Date of Patent: Jan. 26, 1999

5,581,072 12/1996 Bridgelall et al 235/462

5,619,028 4/1997 Barkan 235/462

5,682,028 10/1997 Coleman 235/462

Primary Examiner—Anita Pellman Gross
Assistant Examiner—Diane I. Lee
Attorney, Agent, or Firm—Foley & Lardner

[57] ABSTRACT

A digitizer for a barcode scanner includes an amplifier and a comparator. The amplifier receives a feedback signal and a differentiated return signal on a first port, and a reference voltage signal on a second port. Based on a difference between voltages on the first and second ports, the amplifier outputs an output signal, which is limited between a maximum voltage value and a minimum voltage value. The output signal is delayed in phase, and the phase-delayed signal is input to a first port of a comparator, while the undelayed output signal is input to a second port of the comparator. Based on a comparison of the voltages on the first and second ports of the comparator, the feedback signal having one of a first voltage value and a second voltage value is obtained.

22 Claims, 6 Drawing Sheets