An optimal measure for camera focus and exposure

Consistent image quality is one of the most important requirements for a camera system. This applies to application systems in industrial inspection, consumer photography and microscopy. The quality of an image can be measured in terms of two components: sharpness and contrast. These can be directly translated to the camera system control variables: focus and exposure. A number of measures have been developed to adjust the focus and exposure independently. In this paper, an optimal statistical measure of image quality is developed and tested. This measure allows the simultaneous optimization of both the focus and exposure settings during system calibration or operation. The performance of this measure is demonstrated using a series of test patterns and compared to other popular measures.