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Performance Sensitive Gain Adjustment Routine For Checkout Scanner

IP.com Disclosure Number: IPCOM000048642D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Broockman, EC: AUTHOR

Abstract

This article describes a technique for adjusting the gain of a photomultiplier tube (PMT) in a supermarket scanner to compensate for a smudged or dirty scanner window.

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Performance Sensitive Gain Adjustment Routine For Checkout Scanner

This article describes a technique for adjusting the gain of a photomultiplier tube (PMT) in a supermarket scanner to compensate for a smudged or dirty scanner window.

Where the checkout scanner is controlled by a microprocessor, the technique can be embodied in a subroutine which is called near the conclusion of each scan operation. In the course of the scan operation, two statistics are collected for use in the subroutine. STAT 1 is a count of the number of successful scans. STAT 2 is a count of the number of unsuccessful scan attempts which produce candidates having the appropriate number of characters.

These statistics are used to compute a Quality Ratio (QR) in accordance with the formula STAT 1/STAT 1+STAT 2. The values of STAT 1 and STAT 2 for a given scanner design will vary as a function of operator scanning technique and window condition, i.e., whether the window is clean or dirty. When an operator is properly trained, the effects of scanning technique are secondary.

A fixed value a represents the normal level of performance for a scanner. As long as the scanner window remains clean, the computed Quality Ratio should equal or exceed Alpha. If the Quality Ratio becomes less than Alpha, compensation can be provided by boosting the gain of the PMT tube in the scanner.

Referring to the flow chart, the first step in the subroutine (block 10) is to compute the QR based on STAT 1 and STAT 2 for the just concluded scan operation. A decision is made (block 12) as to whether the QR is greater than
1.1Alpha. If it is not, a check is made (block 14) to see if it is less than 0.9Alpha. If QR falls within the "deadband" between 0.9 Alpha and 1.1 Alpha, no action is taken and program control is retuned to a main program.

If QR has fallen below 0.9 Alpha, a gain delta count is incremented (block
16). The gain delta count reflects the number of gain incre...