Rockwell Automation 5370-CVIM2 Module - Manual (Page 48)

5 Chapter Chapter 3
Image Acquisition Parameters
3–9
The interactive result of the two cursor settings is this: All portions of the
image whose brightness values are between the high and low light reference
values will have digitized pixel values between 0 and 255. Portions of the
image that are brighter than the high reference will have a digitized pixel
value of 255. Portions of the image that are darker than the low reference
will have a digitized pixel value of 0.
Here is a methodical approach to setting the two cursors for any application:
1. Drag the Hi cursor up to its highest position (value: 255).
2. Drag the Lo cursor down to its lowest position (value: 0).
3. Use the Focus function to optimize the focus and set the camera and
lighting for maximum brightness in an image of the parts to be inspected.
NOTE: If image saturation or “blooming” occurs, reduce the image
brightness by reducing the aperture, or, if practicable, by dimming the
lighting.
4. Drag the Hi cursor slowly downward until a green color begins to appear
in the brightest areas of the image. Then, drag the cursor gradually
upward until the green color just barely disappears from the image.
It is acceptable to let some portions of the image remain green (saturated
white) if they are not used for inspection.
5. Drag the Lo cursor slowly upward until a blue color begins to appear in
the darkest areas of the image. Then, drag the cursor gradually
downward until the blue color just barely disappears from the image.
It is acceptable to let some portions of the image remain blue (saturated
black) if they are not used for inspection.
At this point, the contrast between all inspection–related parts of the image
will be maximized. You may, however, still be able to improve the contrast
by making slight changes to the lighting, camera aperture setting, and light
references.
Figure 3.6 (page 3–10) provides an example of how a workpiece image
might appear before and after maximizing the contrast.