Compact infrared cryogenic wafer-level camera: design and experimental validation

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 is compatible with both cryogenic constraints and wafer-level fabrication. The design strategy of such a camera is described, as well as its fabrication and integration process. Its characterization has been carried out in terms of the modulation transfer function and the 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.

Development of an infrared ultra-compact multichannel camera integrated in a SOFRADIR's detector Dewar cooler assembly

“…As a starting point, we consider the cryogenic wafer-level camera we designed in previous work [7] [8]. Its FOV is equal to 120°, and its F-number is equal to 3.…”

“…In previous work, we designed a cryogenic wafer-level camera whose total track length was only equal to 4.08 mm [7] [10]. We assessed its good quality in terms of FTM and NETD.…”

Compact multichannel infrared camera integrated in an operational detector dewar cooler assembly

“…Miniaturization can be achieved by designing multichannel optical systems. We made a cryogenic wafer-level camera whose total track length is equal to 4.08 mm only [28]. However, it is associated with a laboratory IRFPA, and integrated in a laboratory Dewar.…”

Fabrication of concave and convex potassium bromide lens arrays by compression molding

“…A source of inspiration can be found simply by looking at nature, where small invertebrates have developed compound eyes [2]. Several miniaturized systems have already been proposed, and they mainly rely on multichannel architectures [3][4][5][6][7][8][9][10][11]. The principle of these systems is to divide the information contained in the whole scene into the different optical channels.…”

“…The principle of these systems is to divide the information contained in the whole scene into the different optical channels. Therefore, the key components of multichannel architectures are microlens arrays for applications in the visible spectral range [3][4][5][6][7]10] and lens arrays for applications in the infrared spectral range [8,9,11]. Current stateof-the-art technology requires the use of planar detectors and of planar microlens and lens arrays.…”