Hardware manual

Impact Reference Guide Camera
2-21 Datalogic Automation Inc.
tion speed. The range of acceptable values is determined by the camera type. If you want to use partial scan-
ning on an image, you should calibrate the entire image first and then set the partial scan parameters.
For partial scan images, the image coordinates of 0,0 correspond to the sensor pixel coordinates 0,0. This
means that, when the image is partially scanned from the left or top, the upper left image pixel coordinate
becomes the top left partial scan setting. The image above and to the left of the partial scan setting will not
be displayed in the image window.
• Scan Lines to Overlap: This property indicates the number of scan lines to copy from the bottom of
the previous image and add to the top of the current image. As a result of the overlap, the resultant
image is this number of lines taller than the Partial Scan setting used by the camera.
For example, if a camera with 480 lines has an Overlap value of 100, the resultant image delivered to
the vision program will be 580 lines, with the top 100 lines copied from the previous image and the
remaining 480 lines from the camera sensor.
The feature is primarily intended for use with line scan cameras, however it works with any camera. It
works best with line scan cameras because the bottom line of the previous image will be placed
directly adjacent to the top line of the current image. One primary application is inspection of a mov-
ing part, such as a web, that requires multiple images. If an interesting object, such as a defect, falls in
the area where one image ends and the next image begins, the object can not be fully seen in either
image. By setting the overlap setting to the maximum height of the object of interest, the entire object
at the top of the second image will be visible.
This is a property of the Camera Object, so it can be linked into your vision program and used when
analyzing results. For example, smaller objects may get duplicated at the bottom of the previous
image and the top of the current image, so you can recognize that the position of the object is in the
overlap and avoid counting it twice.
The maximum value for this property is equal to the height of the camera image.
The overlap area is expressed in scan lines, not calibrated units.
The overlap feature only works for vertical overlap, not horizontal overlap.
The overlap feature is not currently compatible with lens distortion calibration. It is compatible with
pixel size calibration.
Some third-party cameras do not allow partial scanning.
Color Tab
This tab is enabled only when a color camera is being used. Impact software uses a 3x3 bilinear interpolation
to convert the incomplete color imager output to a usable color image.
White Balance
If you are using a color camera, you can apply automatic white balance correction which calculates the
proper red and blue pixel gains needed to provide an accurate color image, or you can manually enter values
for the red and blue pixel gains.
To automatically adjust the white balance:
1. Point the camera at a uniformly white or grey object or image. Be sure the image is well-lit and not too
bright. Errors are returned if any of the color channels are saturated (the gain is greater than 100%).
2. Adjust the purple rectangular ROI so that it covers only a white or grey area of the image.
3. Click "Auto." The device automatically calculates the proper red and blue gain values to bring all three
colors into balance.
How White Balance Works