Application of Long-Focal-Length Microlens Array on Shack-Hartmann Wavefront Sensor
Date Issued
2011
Date
2011
Author(s)
VINNA
Abstract
In adaptive optics, microlens array (MLA) is used to detect and divide the incidence wavefront into small parts which will be focused on the image sensor (CMOS) of Shack-Hartmann wavefront sensor (SHWS). In this paper, we present the fabrication method of long focal length (millimeter range) MLA with various structure and arrangement based on thermal reflow process. In order to extend the focal length, we used Polydimethysiloxane (PDMS) cover on our glass substrate of MLA. Because of the small refractive index difference between PDMS and MLA interface (UV-resin), the incidence light is less bended and focused in further distance. Besides, other specific focal lengths could be realized by modifying the refractive index difference. After the long-focal-length MLA film was fabricated, it could be integrated with an image sensor to build a SHWS. A longer focal length MLA will provide high sensitivity in determining the average slope across each lenslet under a given wavefront, and the spatial resolution of the wavefront sensor is increased by the number of lenslets across the detector. Thus, the accuracy improves with greater sensitivity and spatial resolution. The experimental result of the system is discussed and compared between the long focal length, the shorter focal length and the commercial SHWS.
Subjects
Shack-Hartmann wavefront sensor
microlens array
thermal reflow
Type
thesis
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