公开(公告)号：DE3280181D1

公开(公告)日：1990-06-28

申请号：DE3280181

申请日：1982-03-25

Applicant: IBM

Inventor： LAURER GEORGE JOSEPH ,  STOKES JR

IPC: G06K7/10 ,  G06K7/016 ,  G06K7/14

Abstract: A technique for compensating for systematic errors in printing or reading bar codes is disclosed. Label decoding always begins with a center character and proceeds one character at a time toward a margin. When bar-space pair measurements indicate an ambiguous character (which can only be fully decoded using bar width measurements) error correction is based on the characteristics of the adjacent, previously decoded character.

公开(公告)号：DE3481646D1

公开(公告)日：1990-04-19

申请号：DE3481646

申请日：1984-12-04

Applicant: IBM

Inventor： CATO ROBERT THOMAS ,  DICKSON LEROY DAVID ,  STOKES JR

IPC: G06K7/12 ,  G02B26/10 ,  G06K7/10 ,  H04N1/113 ,  G02B5/32

Abstract: Operating parameters for a multiple facet holographic disc scanner are adjusted on real time basis as a function of the actual diffraction efficiency of the facet region aligned with the impinging laser beam. The operating parameters are adjusted to achieve optimum signal levels independent of facet characteristics. Diffraction efficiency is inversely related to zero order beam power for a given level of input beam power. A photodetector measures the zero order beam power. The output of this photodetector is used to control video amplifier gain and/or semiconductor laser current.