We have recently shown that dewar-level integration of optics is a promising way to develop compact IR cameras.
Indeed, the integration of optics into the dewar leads to simple and entirely cooled optical architectures dedicated to
imaging applications with large-field of view. Here, we review the optical elements we could add in those devices to
make a hyper- or multispectral imager. Among them, we find specific focal-plane arrays with a built-in spectrometry
function, plasmonic filters combined with a multichannel optical design, and birefringent interferometers. Several optical
architectures will be detailed with first experimental results.
A new configuration of micro-spectrometer based on an infrared stationary Fourier transform (FTIR)
interferometer has been developed at ONERA. Our device is based on a classic infrared focal plane array (FPA)
of HgCdTe technology with a built-in two-wave wedge-like interferometer. This new architecture generates
research works in several domains. Technological researches are conducted in collaboration with the CEA to
optimize the manufacturing process and reduce the technological defects. In parallel, researches in optical
design are conducted to implement the FTIR-FPA in a complete system. For this, theoretical work is needed to
understand and describe the fringes formation inside the detection structure when illuminated by a wave which is
not ideal, i.e. emitted by an extended source positioned at a finite distance from the detection plane. The results
of this theoretical study are presented. These results are exploited to design a compact spectrometer with a very
simple optical architecture. First experimental data are presented and discussed.
Today's infrared focal plane arrays concentrate in a small volume of typically 1 cm3 the results of three decades of
research in microelectronics and packaging. Several technological breakthroughs have already been achieved leading to
the development of infrared focal plane arrays (IRFPA's) for high-performances applications requiring spatial and
thermal resolution, also for low-cost and high-manufacturing volumes (technology of uncooled micro-bolometers). The
next step is to reduce the optics and make it compatible with the successful IRFPA's fabrication technology. This paper
presents some methods and technologies we are exploring for high-performance and small infrared systems. These
developments have led to a tool box of micro-concepts described by an optical function (imagery or spectrometry)
integrated in the vicinity of the IRFPA. For this, old optical concepts have been revisited (pinhole optics, Talbot effect)
and first demonstrations of original IRFPA-based micro-optical assemblies will be given.