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Using the Flat Field Correction Tool
Flat Field Correction is the process of eliminating small gain differences between pixels in a CCD array.
That sensor when exposed to a uniformly lit field will have no gray level differences between pixels when calibrated flat field correction is applied to the image. The CamExpert Flat Field tool functions with hardware supporting flat field processing.
X64-CL iPro Flat Field Support
The X64-CL iPro supports hardware based real-time Flat Field Correction when used with its dual Base or one Medium configuration.
Flat field and flat line correction impose limitations to the maximum acquisition frame rate. Please contact the DALSA support group for more details on camera specific maximum supported acquisition rates.
Note: Sapera LT 5.2 or later is required for using hardware-based Flat Field Correction.
Loading the Required Camera File
Select the required camera configuration file for the connected camera. For a more detailed description of the server and camera file selection menu see
” on page 53 . Verify the acquisition with the live grab function. Make camera adjustments to get good images.
Also at this time make preparations to grab a flat gray level image such as a clean evenly lighted white wall or non-glossy paper. Note the lens iris position for a white but not saturated image. This white image is required for the calibration process.
Flat Field Correction Calibration Procedure
Calibration is the process of taking two reference images, one of a black field – one of a light gray field
(not saturated), to generate correction data for images captured by the CCD. Each CCD pixel data is modified by the correction factor generated by the calibration process, so that each pixel now has an identical response to the same illumination.
Start the Flat Field calibration tool via the CamExpert menu bar:
Tools • Flat Field Correction • Calibration.
Flat Field Calibration Window
The Flat Field calibration window provides a three step process to acquire two reference images and then save the flat field correction data for the camera used. To aid in determining if the reference images are valid, a histogram tool is provided so that the user can review the images used for the correction data.
48 • CamExpert Quick Start for the X64-CL iPro
X64-CL iPro Series User's Manual
• Setup the camera to capture a uniform black image. Black paper with no illumination and the camera lens’ iris closed to minimum can provide such a black image.
• Click on Acquire Black Image. The flat field demo will grab a video frame, analyze the pixel gray level spread, and present the statistics. The desired black reference image should have pixel values less then 20. If acceptable accept the image as the black reference.
• Setup the camera to acquire a uniform white image (but not saturated white). Even illumination on white paper can be used, with a gray level of 128 minimum. It is preferable to prepare for the white level calibration before the calibration procedure.
• Click on Acquire White Image. The flat field demo will grab a video frame, analyze the pixel gray level spread, and present the statistics. The captured gray level for all pixels should be greater than 128. If acceptable accept the image as the white reference.
• Click on Save. The flat field correction data is saved as a TIF image with a file name of your choice (such as camera name and serial number).
X64-CL iPro Series User's Manual
CamExpert Quick Start for the X64-CL iPro • 49
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