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T. W. Raasch; Design and Calibration of a Deformable Mirror System for Control and Manipulation of Wavefronts. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2775.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a deformable mirror-based, white light optical system for the control and manipulation of wavefronts. This system is to be used as a test platform for the study of visual performance, with the ability to manipulate the low- and high-order terms representing wavefront shape.
The main components of the system consist of a small white light source, a MEMS deformable mirror, and lenslet array-based wavefront sensor. The mirror is a continuous membrane mirror over a 12x12 square array of actuators. The wavefront sensor consists of a 44x33 array of lenslets in combination with a 10 bit 640x480 camera. Conventional lenses, or variable-power sphere and/or cylinder lenses, are placed in a pupil-conjugate plane to control defocus and astigmatism terms, enabling the full dynamic range of the mirror to be devoted to high-order aberration control.In calibration mode, the mirror is used to null baseline aberrations in the system, and to generate specific levels of wavefront aberration for use in vision testing. Calibration procedures consist of the characterization of the response properties of the deformable mirror, the development of a control algorithm to generate specific Zernike modes, and an algorithm for the combination of Zernike modes to generate arbitrary wavefront shapes.
Individual Zernike modes with amplitude up to ±0.5υm through the 4th order can be consistently generated with less than 10nm RMS error, over a 4.4mm pupil diameter. Zernike modes with amplitude up to ±0.25υm are producible up through 8th order with less than 10nm RMS error. An iterative procedure has been developed, which converges on the desired shape typically in five iterations or less. This calibration procedure yields lookup tables for the generation of Zernike modes of particular amplitude. Compound modes are generated using a combination procedure to create arbitrary wavefront shapes.
In testing mode, the while light source is replaced by a video display, and the camera is replaced by the eye to be tested. Through manipulation of wavefront shape, existing ocular aberrations can be compensated, and arbitrary levels and types of aberration generated.
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