Systematic error of a large dynamic range aberrometer.

Shack-Hartmann aberrometers are routinely used for measuring ocular aberrations. In one configuration, the intermediate images of the Shack-Hartmann spots formed by the lenslet array are relayed by an imaging lens onto a sensor. A systematic introduction of spherical aberration that is strongly related to the power error (defocus) of the incident wavefront is observed in this configuration. We found that the largest component of this error is induced by the pupil aberration of the imaging relay lens. Some simulations and experimental results are demonstrated.