Algol – CPNG: photon counting cameras for interferometry in visible wavelengths

¹ UMR 6525 H. Fizeau, Université de Nice-Sophia Antipolis, Centre National de la Recherche Scientifique, Observatoire de la Côte d'Azur, Campus Valrose, 06108 Nice Cedex, France
² Université de Lyon, Lyon, 69000, France; Université Lyon 1, Villeurbanne, 69622, France; Centre de Recherche Astronomique de Lyon, Observatoire de Lyon, 9 avenue Charles André, Saint-Genis Laval Cedex, 69561, France; CNRS/UMR-5574; École Normale Supérieure de Lyon, Lyon, France
³ Institut de Recherches en Communication et Cybernétique de Nantes, 1 rue de la Noë, 44321 Nantes, France

Corresponding author: blazit@obs-azur.fr

Abstract

Images in visible interferometry are characterised by their low coherence time, and except for brightest stars, the flux on the detector is much less than one photon per pixel per image. Algol and Comptage de Photons Nouvelle Génération (CPNG) are new photon counting cameras developed for high angular resolution in the visible. They are intensified CCDs built to benefit from improvements in photonic commercial components, and personal computer processing power. We present how we achieve optimal performances (sensitivity and spatiotemporal resolution) by the combination of proper optical and electronics design, and real-time elaborated data processing. The number of pixels is 532 × 516 and 768 × 640 read at a frame rate of 262 Hz and 50 Hz for CPNG and Algol respectively. The dark current is very low: 5 × 10^-4 electron.pixel^-1.s^-1. Quantum efficiencies reach up to 36% in the visible with the GaAsP photocathodes and and 26% in the red with the GaAs ones, thanks to the sensitivity of the photocathodes and to the photon centroiding algorithm; they are likely the highest values reported for ICCDs.