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Hand Wanded Optical Bar Code Signal Processor

IP.com Disclosure Number: IPCOM000083964D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Pierce, CM: AUTHOR

Abstract

When optical bar-coded indicia are scanned by hand-held wands, severe problems are encountered during the decoding process of the electrical signal provided by the hand-propelled scanning wand.

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Hand Wanded Optical Bar Code Signal Processor

When optical bar-coded indicia are scanned by hand-held wands, severe problems are encountered during the decoding process of the electrical signal provided by the hand-propelled scanning wand.

The first of the problems concerns the variations of the output signal from the hand-propelled wand from label-to-label. These variations are caused by differences in the contrast between label samples and differences across the labels themselves, due to losses incurred in the signal as a result of variations in the tilt angle of the scanner. These tilt angle variations will vary from operator-to- operator, and may vary within the scanning of a single label by changes in the angle that the scanning wand makes with the carrier for the label.

A second problem is that the signals representing the symbol encoded on the label in the form of optical bars may be preceded by extraneous noise signals due to other printed matter on the label support. The system must tolerate these extraneous signals and reject them, and provision must be made for determining the beginning of the encoded data.

The third major problem encountered in systems of this nature is the effects of acceleration. Any acceleration of the wand may introduce errors in the decoding process.

The fourth problem encountered in systems of this type is not directly related to operation of the decoding system itself, but is caused by intentional changes to the system, which can necessitate a major redesign of the hardware used for decoding the signals representative of the symbol. The system described is modular in nature and is divided into four independent elements, any one of which may be modified to accommodate different changes of operating parameters.

A block diagram of the modular system is shown in Fig. 1 and includes a first element for receiving the reflected light from the coded indicia. The light energy is converted to electrical energy and amplified and transmitted to a second element, which digitizes the electrical video information provided by the first element. The digitized video signal from the second element is applied to a third element, which locates electrical signals representing symbol coded information. These signals, when identified, are passed on to the fourth element in the system which processes the signals provided by the third element in a digital manner, and provides the decoded information to an ultimate utilization device.

The light converter and amplifier of element 1 is shown in greater detail in Fig. 2. The bar-coded symbol is sensed by detecting the relative reflection of light from the dark and light surfaces. A photodiode is used to provide the conversion from optical to electrical signals, because it provides a more stable, linear and predictable conversion than a phototransistor. Since the output of the photodiode may be less than 25 x 10/-9/ amps, a field-effect transistor (FET) operational amplifier...