Cryogenic wafer-level MWIR camera: laboratory demonstration

Abstract

We present a compact infrared cryogenic multichannel camera with a wide field of view equal to 120°. By merging the optics with the detector, the concept has to be compatible with both cryogenic constraints and wafer-level fabrication. For this, we take advantage of the progress in micro-optics to design a multichannel optical architecture directly integrated on the detector. This wafer-level camera uses state of art microlenses with a high sag height. The additional mass of the optics is sufficiently small to be compatible with the cryogenic environment of the Dewar. The performance of this camera will be discussed. Its characterization has been carried out in terms of modulation transfer function and noise equivalent temperature difference (NETD). The optical system is limited by the diffraction. By cooling the optics, we achieve a very low NETD equal to 15 mK compared with traditional infrared cameras. A postprocessing algorithm that aims at reconstructing a well-sampled image from the set of undersampled raw subimages produced by the camera is proposed and validated on experimental images.