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

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 × 55 μ m 2 and comprises pre-amplifier, a window discriminator and a 14-bit counter. The 256 × 256 Medipix2 array can be read out noiselessly in 287 μ s . The readout can be electronically shuttered down to a temporal window of a few μ s . The Medipix2 is buttable on three sides to produce 512 × ( 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 × 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.