Optimization of the Hartmann–Shack microlens array

Abstract

a b s t r a c tIn this work we propose to optimize the microlens-array geometry for a Hartmann-Shack wavefront sensor. The optimization makes possible that regular microlens arrays with a larger number of microlenses are replaced by arrays with fewer microlenses located at optimal sampling positions, with no increase in the reconstruction error. The goal is to propose a straightforward and widely accessible numerical method to calculate an optimized microlens array for a known aberration statistics. The optimization comprises the minimization of the wavefront reconstruction error and/or the number of necessary microlenses in the array. We numerically generate, sample and reconstruct the wavefront, and use a genetic algorithm to discover the optimal array geometry. Within an ophthalmological context, as a case study, we demonstrate that an array with only 10 suitably located microlenses can be used to produce reconstruction errors as small as those of a 36-microlens regular array. The same optimization procedure can be employed for any application where the wavefront statistics is known.

Spatial control of photoemitted electron beams using a microlens-array transverse-shaping technique

“…The technique employs microlens arrays (MLAs) to directly homogenize the UV laser pulse. MLAs are commonly employed as optical homogenizers for various applications [2][3][4]. In addition to its homogenizing capability, we also demonstrate that the MLA-based technique can also produced a periodic transverse pattern that can form a two-dimensional array of transversely-segmented beams.…”

Customised aberration‐controlling corrections for keratoconic patients using contact lenses

“…A fundamental limitation of the Hartmann–Shack sensor is the requirement that each spot image, generated by any given micro‐lenslet, must land within the ‘virtual sub‐aperture’ of a certain photon detector at the charge‐coupled device (CCD). To this end, the ‘dynamic range’ of a Hartmann–Shack aberrometer is somewhat restricted by the diameter of each individual micro‐lenslet, which typically ranges somewhere between 0.3 to 0.5 mm, but can be as large as 0.75 mm …”

“…To this end, the 'dynamic range' of a Hartmann-Shack aberrometer is somewhat restricted by the diameter of each individual micro-lenslet, which typically ranges somewhere between 0.3 to 0.5 mm, 64 but can be as large as 0.75 mm. 65 The computerised software typically used in commercially available Hartmann-Shack aberrometers is not usually capable of correctly identifying the following spot image registration issues: 56,61,66 • when two (or more) separate spot images are formed at the same CCD photon detector sub-aperture ( Figure 5A) • a spot image which perfectly overlaps with another, formed by an adjacent micro-lenslet ( Figure 5B) • a spot image that 'crosses over' the allocated path of another spot ( Figure 5C) • missing spot imageswhen one or more spot images are formed in an area that falls entirely outside of the CCD sensor ( Figure 5D). While a 'displaced' spot image is obviously aberrant from the 'chief' or 'reference' ray, the magnitude of this displacement provides no indication of the image's quality.…”

Computational test bench and flow chart for wavefront sensors

“…At sampling plan, the input wavefront can be sampled, for exemple, through Castro lenses [4], optical aperture with Liquid Crystal Display (LCD) [5], or a microlens array [6], which has the function of providing information on the local inclination of the wavefront input. In other words, it is at this stage that will be sampled parts of the wave front entrance in the shape of light spots, regarding the same to the next step.…”