We employ an acousto-optic cell as a tunable-pitch wavefront sensor and study its performance. The index of refraction of two cross-standing waves forms, in the near field, an adjustable array of caustics. These caustics, similar to the lenslets used for Hartmann–Shack sensing, were measured to have an extended focal relief of 200 times their pitch. We discovered a strong interaction between the caustics and source speckle, so much so that we had to modulate the beam to reduce it. We measured ocular wavefronts at different frequencies and established the consistency and reliability of the reconstruction.
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