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Automatic Sensitivity Adjustment for Digital Image Acquisition System

IP.com Disclosure Number: IPCOM000037809D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-30
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Fellows, T: AUTHOR [+4]

Abstract

An analog video signal must be converted to a binary data stream in a printed circuit pattern image processing inspection system. The analog signal is first digitized and then compared to a predetermined threshold value. The binary data that results from this process indicates the limits of system detection capability.

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Automatic Sensitivity Adjustment for Digital Image Acquisition System

An analog video signal must be converted to a binary data stream in a printed circuit pattern image processing inspection system. The analog signal is first digitized and then compared to a predetermined threshold value. The binary data that results from this process indicates the limits of system detection capability.

Unfortunately, reflectivity characteristics of parts to be inspected vary. This causes a variation in the analog video signal and makes it difficult to set a threshold that will maximize the system defect detection capability for all parts to be inspected.

The method herein described compensates automatically.

A feature whose dimensions are already known on the panel to be inspected is chosen as the object of the following inventive procedure: 1. Establish a threshold compensation factor based on a sample product and store the factor for use on all subsequent panels. A table of values can be created which contains the imaged width of a known feature at various threshold settings. This is accomplished by setting a threshold, imaging an area of the panel and recording the average imaged dimensions of a set of features. When a reasonable number of samples is inspected, the average change in dimension for a change in threshold can be determined. 2. Load a "ball park" threshold. A value representative of the final threshold from the previous panel is recommended. 3. Image a representa...