A noiseless kilohertz frame rate imaging detector based on microchannel plates read out with the Medipix2 CMOS pixel chip

摘要

A new hybrid optical imaging detector is described that is being developed for the next generation adaptive optics (AO) wavefront sensors (WFS) for ground-based telescopes. The detector consists of a photocathode and proximity focused microchannel plates (MCPs) read out by the Medipix2 CMOS pixel ASIC. Each pixel of the Medipix2 device measures 55 x 55 mu m(2) and comprises pre-amplifier, a window discriminator and a 14-bit counter. The 256 x 256 Medipix2 array can be read out noiselessly in 287 mu s. The readout can be electronically shuttered down to a temporal window of a few mu s. The Medipix2 is buttable on three sides to produce 512 x (n * 256) pixel devices. Measurements with ultraviolet light yield a spatial resolution of the detector at the Nyquist limit. Sub-pixel resolution can be achieved using centroiding algorithms. For the AO application, very high continuous frame rates of the order of 1 kHz are required for a matrix of 512 x 512 pixels. The design concepts of a parallel readout board are presented that will allow this fast data throughput. The development status of the optical WFS tube is also explained. (c) 2006 Elsevier B.V. All rights reserved.