| 摘要 |
A system and method which substantially eliminates systematic error in a centroid determination of reconstructed waveforms from images generated by an image sensor. In accordance with the invention, a predetermined wavefront error is added to an input wavefront and the wavefront is detected. The predetermined wavefront error is effective to improve centroid determination. The predetermined wavefront error is effective to improve centroid determination. In the illustrative embodiment, the input wavefront is passed through a random phase plate. The phase plate is an optical window in which the thickness in a z-axis varies randomly over an X/Y plane. The random phase plate acts as a low pass filter and the output of the phase plate is an aberrated wavefront. That is, the nonuniform thickness of the phase plate generates random spatial phase errors in the optical wavefront. The autocorrelation function of the phase plate is such that random phase errors in the optical wavefront will filter out spatial frequencies higher than one cycle per pixel. Hence, the systematic centroiding error is reduced. In the illustrative embodiment, the aberrated wavefront is imaged onto a charge coupled device (CCD) detector by an optical arrangement. The optical arrangement may be implemented with either lenses or mirrors. The CCD is composed of discrete pixels which spatially sample the optical image and converts the photons in the blurred optical image into electrons. An analog-to-digital (A/D) converter converts the analog voltage to a digital signal. A digital circuit reformats the digital signal and provides an interface to a microprocessor. Software running on the microprocessor computes the position of the image centroid on the CCD using the digitized pixel data in a conventional manner.
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