Panasonic A230 User Manual

Gray Scale Edge Checkers OCR Type A23011 − 611.1 Gray Scale Edge Checkers24. AreaCreate or move the checker area.The area cannot be set to a size of less than 7 pixels in the scanning direction.The “Illegal checker area size.” error will appear.25. Edge ConditionSet the edge conditions for the checker being created.A gray scale edge checker scans from start point to end point, detecting edgesin the image under inspection where light changes to dark, or where darkchanges to light, or both.The edges are detected at locations meeting the conditions set for the edgethreshold value.The default setting is Both. When set to Both, the filter, width and averagearea functions work on both light to dark edges and dark to light edges,enabling edges with positive and negative differentials to be detected.Edge conditionPointScan directionDetection direction = horizontalDetection direction = verticalFinishing pointDark → light Light → darkStarting pointScan direction Detected Detected DetectedDetectedDetectedDetectedDark → light Light → darkStarting pointFinishing pointBothBoth26. Edge Threshold ValueSet the edge threshold values for the checker being created.A gray scale edge checker performs differential processing on a gray scaleimage to detect edges. Changes in brightness of the gray scale image areprocessed as differential data. After processing, the data can be representedas a graph with peaks like those shown in the diagram. When the graph slantsupwards, the gray scale level is changing from dark to light. The dotted lineon the vertical axis of this graph is the threshold value (expressed in256−gradation gray scale). Only peaks which reach the threshold value aredetected as edges. Set the threshold value with reference to the differentialvalues of the edges so that only the required edges are detected.