Stabilization of light sources with digital micromirror devices for calibration of high-precision photometric instruments

To answer the new challenges imposed by the most recent exoplanet space missions, testing and calibrating high-precision photometric instruments requires a highly stable illumination system, which is a great challenge when the mission’s required photometric stability is a few parts per million for long observation periods. Traditional calibration sources do not fulfill the stability requirements of the most demanding missions. It is necessary to use additional methods to compensate for flux fluctuations. This study introduces a new method, using a digital micromirror device (DMD) as an intensity light modulator. DMD is a micro-electromechanical device developed by Texas Instruments, which consists of a two-dimensional array of micromirrors. Each micromirror can be individually tilted between two positions. By controlling the state of each micromirror, it is possible to control the flux of light that goes in a particular direction. This technology enables fast modulation speeds, with high precision and broadband capabilities. This study presents an exploratory work on the technical feasibility of using DMDs to compensate for light source fluctuations, accurately modulating the beam coming from a Halogen (QTH) source. We developed a proof-of-concept method able to reduce light source fluctuations from ±1.3% to ±0.1%, based on a simple open loop methodology.