Design, analysis, and testing of a microdot apodizer for the Apodized Pupil Lyot Coronagraph. II. The dot size impact. (Research Note)

The Apodized Pupil Lyot Coronagraph (APLC) is a promising coronagraphic device for direct exoplanets detection on the European-Extremely Large Telescope. We present new near-IR laboratory results using binary apodizers -- the so-called microdots apodizer -- which represent a very attractive and advantageous solution for the APLC. Microdots apodizers introduce high-frequency noise whose characteristics depend on the pixel size. The aim of this work is to characterize the impact of the pixel size on the coronagraphic image. Estimation of both the noise intensity and its localization in the field of view is the objective of this study. Stray-light diffraction introduced by the finite pixel size was measured during experiment. Intensity decreases, and radial distance increases, when the pixel size gets smaller. The physical properties of these microdots apodizers have been demonstrated in laboratory. The microdots apodizer is a suitable solution for any coronagraph using pupil amplitude apodization if properly designed.