Rockwell Automation 5370-OCR2 PAK - Manual (Page 80)

A–B
B
Appendix
B–1
Compensating for Lighting Variations
This appendix describes how to use CVIM2 Image Tools to compensate for
variations in lighting.
Variations in the lighting across the field of view or image to image
brightness variation can make it difficult to recognize characters. The effect
of these variations can be reduced by using the CVIM2 module Image Tools
to preprocess the image before recognizing the characters with the OCR
Tool. This appendix describes two methods that provide this type of
compensation. These methods also provide moderate compensation for
background color change and changes in print density.
Method 1 – Maximum Compensation
The maximum compensation for lighting variation is accomplished using
two Image Tools that compensate for changes in the angle and brightness of
the light:
•
The first Image Tool filters out the characters to produce a brightness
reference image.
•
The second Image Tool subtracts the brightness reference image from
the original camera image to produce a compensated image for the
OCR Tool.
Note: Refer to the CVIM2 Reference Manual (Publication No. 5370-801)
for more information on Image Tool operation.
Objectives
Using Image Processing