520.490 Analog and Digital VLSI Systems

A Detector Array for Direct Control of a Deformable Mirror

Robert Winsor, Margaret Frazier, Michael Krueger, Tim Myers
Graduate Advisor: Marc Cohen

The Detector Array in TinyChip form

A detector array is presented with capabilities suited towards adaptive optical systems.  The array is designed to have a white light interferogram imaged onto it, which is modulated to provide phase retrieval.  The nature of the modulation is characterized by a voltage signal, which is delivered as an input to the array.  For many applications, this can also be used to directly drive the resonator.  As a fringe moves across an individual detector, the null is sensed and this triggers a sampling of the modulation signal.  The signal is sampled and held until the next null is sensed.  By looking at the sampled signal, it is possible to directly determine the necessary corrections to send to a deformable mirror to flatten the phasefront.  The array outputs both the photodetector current and the sampled modulation signal voltage.    Individual pixels are selected by means of bit parallel row and column input.  Each pixel in the array corresponds to an actuator on the deformable mirror, so a 1:1 mapping is required in the optics.  Simulations of this design suggest refresh rates in excess of 3kHz are attainable.  A prototype of this array is being fabricated in a 0.5um CMOS process with 21 x 21 detectors, suitable for (circular) deformable mirrors with up to 349 actuators.  This wavefront sensor could greatly simplify the process of controlling a deformable mirror for many applications, thereby increasing refresh rates and improving sensitivity.

Keywords:  Detector Array, Adaptive Optics, Deformable Mirror, Controller, Interferometer, VLSI


Robert Winsor, winsor@stsci.edu, December 7, 2001.