Decoding algorithms for improving the imaging performance of Vernier anode readout

Abstract

The Long Slit Spectrograph is one of instruments onboard The World Space Observatory-Ultraviolet. Both the FUV (102-1700nm) and NUV (160-320nm) channels of LSS choose micro-channel plates (MCP) detector with anode readout in the focal plane. The MCP detectors with anode readout are typically used to provide photon counting imaging. According to the desired performance of LSS, the Vernier anode may be the optimum readout scheme. The Vernier anode is famous for its high spatial resolution, however, the original decode algorithms of the Vernier anode is susceptible to wrongly decode, when the charge acquisition is not precise enough and the footprint size of charge cloud collected by Vernier anode is not small enough and eventually results in the deterioration of photon counting image. In this paper, the causes leading to image deterioration is analyzed. The least-squares method was used to calculate the phase value to correct imaging distortions caused by charge measurement accuracy. The area ratio of each electrode covered by charge cloud is accurately calculated to improving the imaging results. The corrected algorithms are verified by experimental results and the results show that the correction methods can obviously improve the quality of the original photon counting image.