Absolute Radiometric Calibration Of Digital Imaging Systems

We have developed a tunable laser-based facility for the absolute radiometric calibration of digital imaging systems such as CCD cameras, spectrographs, and microscopes. Several types of silicon-based digital imaging systems have been calibrated in this new facility, including a commercially available camera equipped with a removable photopic filter, a custom-designed digital microscope, and a CCD spectrograph. We present results of the CCD camera calibration in detail and discuss relevant aspects of the microscope and spectrograph calibrations. During the radiometric calibration, the pixel-to-pixel uniformity, linearity, and absolute spectral responsivity of each system were determined over the visible spectral range (400 nm to 800 nm). Each of these aspects of the CCD camera calibration will be presented, along with a discussion of the measurement uncertainties.