Elastomeric lenses with tunable astigmatism

Abstract

Microlenses fabricated using flexible elastomers can be tuned in focal length by application of controlled strain. By varying the strain azimuthally, the lenses may be deformed asymmetrically such that aberrations may be controlled. This approach is used to tune the astigmatism of the tunable lenses, and it is shown that the generated wavefront may be accurately controlled. The lens presented here has an initial focal length of 32.6 mm and a tuning range of 12.3 mm for approximately 10% applied strain. The range of directly tunable Zernike polynomials representing astigmatism is about 3 mm, while the secondary lens errors, which cannot be tuned directly, vary only by about 0.2 mm. Light: Science & Applications (2013) 2, e98; doi:10.1038/lsa.2013.54; published online 13 September 2013Keywords: aberrations; active or adaptive optics; micro-optical devices; polymers INTRODUCTION A broad spectrum of tunable micro-optical components using a wide variety of physical effects has been proposed and demonstrated. 1 One approach with considerable potential is the mechanical deformation of microlenses entirely made of flexible elastomers: by controlled application of radial strain, resulting in a change in lens curvature, it has been shown that the focal length can be tuned over a considerable range. 2,3 To date, strain has only been applied symmetrically around these tunable elastomeric lenses, such that only refractive power (focal length), but not other optical properties, have been tuned. A number of other tunable devices have considered the astigmatism. For example, Beadie et al. 4 presented a tunable composite lens, one part being a fixed focal length lens made of poly(methylmetacrylate) and the tunable part using a membrane with a poly(dimethylsiloxane) (PDMS) elastomer as a filling; the surface profiles showed an inherent astigmatism.Alternatively, singlet polymer lenses with thermal actuation have been reported by Lee et al. 5 By choosing an anisotropic heater structure, Lee et al. were able to tune astigmatism along one axis, while the other axis remains fixed. A more versatile approach with a combination of several membrane lenses was pursued by Marks et al. 6 Here two perpendicularly oriented cylindrical lenses provide variable astigmatism, whose total focus is compensated with a rotational symmetric membrane lens.We show here that application of azimuthally varying strain to a deformable elastomer lens can result in controlled variation of aberrations, particularly astigmatism. As a result, the microlens is not only tunable in focal length, but the concomitant aberrations can be increased or decreased at will.

Design and analysis of an adaptive lens that mimics the performance of the crystalline lens in the human eye

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“…(5) [9][10][11]: (5) where φ is the total system power, τ the distance between elements, and φ si the individual element power.…”

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