Browse Prior Art Database

Dot Location Measurement System

IP.com Disclosure Number: IPCOM000046576D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 64K

Publishing Venue

IBM

Related People

Linton, RL: AUTHOR

Abstract

The system provides more precise measurement of individual dot placement by a matrix printer. It is important to accurately measure quality during printer manufacturing in order to maintain quality control. The present technique measures dot placement automatically, thereby removing variations of human judgment. A printed sample is scanned, and representative data is stored in a computer where the data is analyzed to determine dot placement. This technique consists of two phases. The first phase makes measurements of a print sample. The second phase provides an algorithm for utilizing these measurements to determine the size and location of each individual dot. Refer now to Fig. 1.

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Dot Location Measurement System

The system provides more precise measurement of individual dot placement by a matrix printer. It is important to accurately measure quality during printer manufacturing in order to maintain quality control. The present technique measures dot placement automatically, thereby removing variations of human judgment. A printed sample is scanned, and representative data is stored in a computer where the data is analyzed to determine dot placement. This technique consists of two phases. The first phase makes measurements of a print sample.

The second phase provides an algorithm for utilizing these measurements to determine the size and location of each individual dot. Refer now to Fig. 1. A commercially available optical video scanner is used for locating the edge of the light-to-dark or dark-to-light transition on a cross hair within its field of view. A print sample is placed in the scanner and measurements on the opposite edges of a row of dots are made. These measurements are stored in the processor memory as x and y values with respect to an arbitrary origin. The second or analysis phase of the process uses the processor, an X-Y plotter and an output printer. The information derived from the stored data is the size and location of each individual dot which may sometimes overlap and must be separated to produce valid results. Under software control, the data may be separated into as many segments as there are dots in the sample. Refer now to Fig. 2. Dot separation is performed by examining a plot of the distance from top to bottom of the dot versus the measurement position. The number of valleys in this plot is determined. If this number equals one more than the number of segments desired, then the low points of the valleys are taken as the boundaries of the segments. If there are too many segments, due to local minima, then the program smooths the curve by averaging each two adjacent points and plotting the result between them. After smoothing, the number of valleys are checked. Alternate smoothing and checkin...