of the aperture 118 with further improvement such a wavefront sensor can be made more adaptive to provide a number of additional advantages to a number of applications we will now discuss the advantages that one can further obtain by turning the sequential wavefront sensor into an adaptive one note that since the sampling of each sub wavefront is sequential they are separated in time and consequently there is no longer the concern of a cross talk between neighboring sub wavefronts as would happen for the simultaneous parallel sensing format when the tilting of a sub wavefront is significant although in the parallel case larger lenslet grid size can reduce cross talk it will reduce the spatial resolution as well in the adaptive sequential case the aperture size for a sub wavefront to be sampled by the adaptive sequential wavefront sensor can be made either large to achieve a desired high light sensitivity adequate resolution and sub wavefront averaging effect or as small as the diffraction limit allows to substantially increase the spatial resolution as needed the small aperture and hence high spatial resolution is especially beneficial for precision measurement of certain high order aberrations which in the case of a human eye are more predominant when the iris is widely open or in older patients on the other hand the larger aperture will allow more averaging effect for higher order aberrations and faster data processing in exchange for the lower spatial resolution in the case of a human eye the aperture can be opened more for the central regions of the eye furthermore for an adaptive sequential wavefront sensor the photodetector used is typically a quadrant detector or in general a light spot.