Design and Development of DMD Controller Interface for INSIST

Abstract

The INSIST (Indian Spectroscopic and Imaging Space Telescope) is a UV-optical 1m class telescope expected to produce high quality imaging and moderate resolution spectra of astronomical sources. A DMD is an optical microelectrical-mechanical system (MEMS) that contains an array of highly reflective aluminum micromirrors. A Digital Micromirror Device (DMD) will be used in front of the onboard spectrograph for sampling light coming from astronomical sources of interest in the light path. The role of DMD here is similar to the slit mask used in the conventional spectrographs. DMD comprises tiny mirror lets arranged in the form of pixels which can be flipped between two predefined positions by applying digital signals. Here DMD acts as a slit for spectrograph with capability of forming multiple slits. This feature enables Multi Object Spectrograph (MOS) capability. By selecting the appropriate pixels on the DMD the required slit mask shape can be configured. The INSIST DMD Controller consists of three levels of cards stacked on one another. The base card being the User Interface Controller (UIC) FPGA Card, middle one being Chipset Card and top most card is DMD DLP9500UV Card. In this project, a controller interface module to transfer the slit mask pattern to the DMD device is under development. Here the user interface controller (UIC) FPGA card is capable of generating and receiving signals required for Chipset Card and communicating with external users. DMD Chipset Card mainly consist of DLPC410 controller chip, DLPR410 PROM chip on board system clock of 50MHz and DLPA200 (2x) driver chips for DLP9500UV. This controller interface takes the data from the user, which contains how many rows and columns of DMD to be flipped for particular observation. DMD DLP9500UV card has 1920X1080 micromirror that can be tilted by +/-12 and the positive (+) state is tilted toward the illumination and is referred to as the "on" state. Similarly, the negative (–) state is tilted away from the illumination and is referred to as the "off" state. At the initial stage of development, this slit mask input will be directly in the form of row and column numbers. The user interface FPGA card is responsible for receiving user data in terms of 1920 × 1080 Array states corresponding to Micromirror states. Each element in this data array is 1-bit binary. This received data needs to be forwarded to DLPC410 controller at the clock rate of 400 MHz At a later stage we will derive the row and column based on the acquired image from the imaging channel. This module will convert Row and Column data in a format which is suitable to the DMD chipset and transfer it to chipset with suitable command format. Controller interface module will receive telemetry of the DMD chipset and display the health of the DMD.