To properly configure Pixelink cameras for optimum image quality:
Plug in the camera and open the software;
Start the preview window.
Configure the Region of Interest as required to get the proper field of view.
Set the lens, lighting, exposure, brightness (only available in monochrome cameras) and gain so that the blacks are black and no areas in the image are saturated. Auto exposure will provide a good starting point. The histogram tool can be used when adjusting the above parameters to ensure that the image is not saturated. Ideally, you want all the image data to be within the histogram and to use most of the available gray scales. The figure below shows an example of a histogram that covers most of the grey scales available.
For a colour camera, adjust the White Balance feature to match the temperature of the light source. The default is incandescent 3200º Kelvin.
Adjust the white point with the Auto White Shading or Auto White Balance feature. This feature uses the highest intensity areas of the scene to assess the white shading. Ensure that these areas are white or gray in color. Replace high-intensity colored objects with a gray or white card and ensure there is little or no saturation occurring in the image (i.e. gray is better than bright white).
Adjust the Saturation to achieve the best color.
Adjust the Gamma control as required to achieve the best image contrast.
Flat Field Correction
Any digital camera has temporal and pattern noise. Fixed Pattern Noise (FPN), Photo Response Non Uniformity (PRNU), and stuck pixels are examples of pattern noise. If not corrected, these noise sources can cause significant image artefacts.
Pixelink camera corrects for these forms of pattern noise artefacts with a pixel-by-pixel flat field correction (FFC). Internal to the camera, a gain and offset is applied to each pixel so that the overall sensor has a uniform response. In addition, stuck pixels are corrected by replacing their value with the average of the neighbouring pixels.
The FFC is factory calibrated at zero gain with a standard diffuse light source and no lens. While the calibration can be used at other camera settings, it is only valid for the gain and exposure setting used during the calibration. At other settings, image artefacts may be apparent.
For the best results, it is strongly recommended that users of Pixelink PL-B cameras perform a FFC calibration with the lens and lighting that will be used in the field.
A Flat Field Calibration Wizard is available as part of the Pixelink Camera Kit or SDK, and can be used with PL-B cameras. Instructions on the process are included in the application dialog boxes.
Before evaluating the camera on image quality, users should determine the exposure and gain settings required based on the factory calibration for the lens and lighting used in their application. Then, with the subject removed and with a uniform surface under examination, perform the FFC calibration. Once this is complete, continue with the evaluation of the image quality.
If a single gain and exposure setting is not possible, there will be practical limits on the gain and exposure times that can be used before the noise artifacts cause unacceptable degradation to the image quality.
For PL-D cameras, please use the Static Defective Pixel Correction Wizard.
Thermal Considerations
Machine vision users should heat-sink cameras since temperature affects the black level offset. Waiting a few minutes for the camera to reach a certain temperature level will minimise temperature induced image quality drift.
For more information, see Thermal Considerations, or Thermal Considerations for mounting PL-D cameras.