Abstract
In order to determine light aberrations, Shack-Hartmann optical wavefront sensors make use of microlens arrays (MLA) to divide the incident light into small parts and focus them onto image planes. In this paper, we present the design and fabrication of long focal length MLA with various shapes and arrangements based on a double layer structure for optical wavefront sensing applications. A longer focal length MLA could provide high sensitivity in determining the average slope across each microlens under a given wavefront, and spatial resolution of a wavefront sensor is increased by numbers of microlenses across a detector. In order to extend focal length, we used polydimethysiloxane (PDMS) above MLA on a glass substrate. Because of small refractive index difference between PDMS and MLA interface (UV-resin), the incident light is less refracted and focused in further distance. Other specific focal lengths could also be realized by modifying the refractive index difference without changing the MLA size. Thus, the wavefront sensor could be improved with better sensitivity and higher spatial resolution.
Highlights
An optical wavefront sensor is an important device in determining wavefront aberration if fields ranging from the astronomy to any optical testing application
The incident light is divided into a number of beamlets by the two-dimensional microlens array [8]
The spot displacement which is related to the wavefront slope could be calculated by comparing the reference focal spots and the measured wavefront focal spots provided by each lenslet
Summary
An optical wavefront sensor is an important device in determining wavefront aberration if fields ranging from the astronomy to any optical testing application. There are several types of wavefront sensors including the Michelson interferometer, Shearing interferometer, Fizeau interferometer, and even the Foucault knife-edge test. Applications in quality laser beam measurement, optics testing, and optical system calibration and alignment have been discussed. This technology quickly led to the evolution of more sophisticated sensors focused around ophthalmic applications [2], CCD cameras, and micro-optics. The incident light is divided into a number of small samples by the lenslet arrays, which are focused onto a detector array These focal spots of light are the key principle in the measurement of wavefront aberration. The experimental results of the system are discussed and compared between the long focal length, the shorter focal length and the commercial SHWS
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