Abstract
Purpose::
To evaluate the measurement resolution of the Shack-Hartmann (SH) and Ronchi grid (RG) ocular wavefront sensors when the modulation transfer function (MTF) peak algorithm is used to determine refractive state of the eye.
Methods::
We derived equations for the MTF peak algorithm for both a SH and RG ocular wavefront sensor to determine the location of spectral peaks in the MTF of the captured image. The distance traveled by the spectral peaks in the MTF array due to a defocused wavefront (-10 D) was used to determine the system measurement. System parameters, such as pupil size and image detector size and resolution, for the SH and RG systems were identical except for the sensors’ characteristics and distance between the sensor and its image plane.
Results::
Using the expressions derived for system resolution, we were able to work backwards to determine sensor design parameters to yield equivalent resolution for the SH and RG systems. Generally, these design parameters would require custom SH and RG sensors to achieve the desired resolution.
Conclusions::
By proper selection of sensor parameters, the resolution of measurements using the MTF peak algorithm for the SH and RG ocular wavefront sensors can be made equal.
Keywords: image processing