Currently, most wavefront sensors designed for measuring the aberration of a human eye involve the use of a two dimensional lenslet array and a two dimensional photodetector array such as a CCD or CMOS image sensor (U.S. Pat. Nos. 5,777,719, 6,530,917) for wavefront information collection. One problem associated with these wavefront sensors is the cross talk between neighboring sub-wavefronts sampled, which puts a limit to the wavefront spatial resolution. In an attempt to increase the wavefront resolution, a Talbot type wavefront sensor was recently introduced to the market which uses a cross grating and a CCD or CMOS detector array placed at the self-imaging plane of the cross grating (U.S. Pat. No. 6,781,681) to extract the wavefront information. Nevertheless, a common problem associated with these parallel simultaneous multiple sub-wavefront sensing schemes is the invariability of the grid associated the either the lenslet array or the diffraction grating and/or the photosensitive pixels of the CCD or CMOS sensor. Other drawbacks of these schemes include the relatively low data transfer rate resulting from the limited frame rate of the CCD or CMOS used and the time-consuming data processing required in order to extract the various orders of aberrations in the form of the coefficients of a Zernike polynomials. The fixedness of the grid and the relatively low speed of operation of these wavefront sensors put limitations to their applications. Although another technology based on laser beam tracing does not require the use of a two dimensional detector array for wavefront information extraction as described in U.S. Pat. No. 6,932,475, this patent did not discuss the speed and grid size issue.
In a pending patent application entitled “SEQUENTIAL WAVEFRONT SENSOR” (application Ser. No. 11/335,980), a high speed sequential wavefront sensor was disclosed that includes a variable aperture for controlling the size of each sampled sub-wavefront. However, no detailed elaboration has been given to describe how this aperture variability can be explored to bring additional advantages for different applications.
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