  We present a design improvement for a recently proposed type of
Shack-Hartmann wavefront sensor that uses a cylindrical (lenticular) lenslet
array. The improved sensor design uses optical binning and requires
significantly fewer detector pixels than the corresponding conventional or
cylindrical Shack-Hartmann sensor, and so detector readout noise causes less
signal degradation. Additionally, detector readout time is significantly
reduced, which reduces the latency for closed loop systems, and data processing
requirements. We provide simple analytical noise considerations and Monte-Carlo
simulations, and show that the optically binned Shack-Hartmann sensor can offer
better performance than the conventional counterpart in most practical
situations, and our design is particularly suited for use with astronomical
adaptive optics systems.
