Step-by-step algorithm for focal length optimization in a varifocal Shack-Hartmann wavefront sensor

This paper details the development of a varifocal Shack-Hartmann wavefront sensor (SHWFS) featuring an innovative mechanism for dynamic microlens array adaptation. The core of this advancement is a closed-loop iterative algorithm designed to optimize the focal spot size on the detector plane by precisely adjusting the position of the microlens array.

The performance of the device was rigorously investigated under two distinct regimes: direct illumination of the lenslet array with a 650 nm wavelength laser, and operation after resizing optics conjugated with a high-quality reference plate (with a surface figure accuracy of 0.12 μm P-V at 650 nm). Initial tests revealed that the Hartmannogram was highly distorted due to aspherical aberrations arisen from telescope optics. Estimation of the SHWFS microlens array is analyzed on the focal spots size and step-by-step adjustment with thread-to-thread adapter. This process repeats iteratively until the spots are brought into optimal focus.

In summary, the integration of this adaptive algorithm represents a significant leap forward in optical metrology. By enabling dynamic optimization, this work successfully addresses key limitations of traditional sensors. The ability to dynamically adjust the focal length provides unparalleled flexibility, ensuring accurate measurements across a vast range of light intensities and wavefront aberration amplitudes. This adaptability is crucial for applications demanding both high sensitivity and a large dynamic range, positioning the proposed sensor as a versatile platform for research in fields from astronomical adaptive optics to ophthalmic diagnostics.