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Browse Prior Art Database

Delta Distance Decoding Having Acceleration Insensitivity

IP.com Disclosure Number: IPCOM000082174D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Subba Rao, KV: AUTHOR

Abstract

In one form of retrospective modulation, an encoded space or bar represents a binary "1" if this space or bar is of the same width, within a tolerance, as the preceding bar or space, respectively. A binary "0" is encoded if the widths are different.

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Delta Distance Decoding Having Acceleration Insensitivity

In one form of retrospective modulation, an encoded space or bar represents a binary "1" if this space or bar is of the same width, within a tolerance, as the preceding bar or space, respectively. A binary "0" is encoded if the widths are different.

When bar code is printed by an impact printer such as a typewriter, increased impression force increases bar width and reduces space width and vice versa. However, leading edge to leading edge and trailing edge to trailing edge dimensions of adjacent bars do not vary with impression control, When each group of bars representing a character is carried on a single-type face. For example, bars and spaces may nominally be 8 mils or 16 mils wide. In this example, edge-to-edge dimensions of adjacent bars will nominally be 16 mils (small), 24 mils (medium), or 32 mils (large), depending upon their width and spacing as necessary to encode a character.

Bar code can be read and decoded using a hand-held scanner which provides pulses in time, having width and spacing which is proportional to the printed bars and spaces. The proportionality is not constant but varies with scanning acceleration. One decoding method is shown in IBM Technical Disclosure Bulletin, Vol. 16, No. 6, November 1973 at pages 1944 and 1945.

The following decoding method utilizes two known reference dimensions which must be contained in a start character, appearing at the beginning of each message. For example, the leading edges of the first two ba...