The increasing availability of sensors that can image in the 1 to 5 μm region has allowed for systems to be developed that utilize the full spectrum. Current mid-wave infrared (MWIR) systems have typically only imaged in the 3 to 5 μm region, but the new detectors allow imaging in the short-wave infrared (SWIR) and MWIR bands on the same image plane. Night Vision and Electronic Sensors Directorate (NVESD) had a requirement to design and build a multiple field of view (FOV) optical system that could image the 1 to 5 μm spectral band utilizing a single, cooled infrared detector. The primary challenge of designing this particular optical system was to get the 1 to 2 (SWIR) µm band to focus at the same image plane as the 3 to 5 (MWIR) µm band in all FOVs. A three-FOV broadband optical system that can image the 1 to 5 μm band on the same image plane was designed and built. Several optical concepts were looked at, and it was decided that a combination of a reflective afocal and refractive imager was the best way to meet the system requirements. The use of a catadioptric system with a single focal plane that images in the 1 to 5 μm spectrum reduces the size of the system and provides the user with see-spot capability.
The increasing availability of sensors that can image in the 1-5 micron region has allowed for systems to be developed
that utilize the full spectrum. Past MWIR systems have typically only imaged in the 3-5 micron region, but the new
detectors allow imaging in the SWIR and MWIR bands with the same system. The use of a single FPA reduces SWAP
and allows the user to see laser rangefinder and laser designator wavelengths. NVESD and Axsys have designed and
built a SWIR/MWIR optical system that images in the 1-5 micron band. The optical system utilizes a cooled infrared
detector that images in the 3-5 micron band as well as 1.04 - 1.08 and 1.54 microns without having to refocus the system
to see the SWIR wavelengths. This provided an optical challenge to design a system that would image from 1-5 microns
on the same detector. A combination reflective/refractive design was chosen in order to minimize packaging and meet
the different FOV requirements. This paper discusses the design and development of a multi-FOV optical system with
the capability to image across the 1-5 micron spectral band utilizing a combination of reflective and refractive
Recent requests for test stations to characterize and evaluate thermal and visible imaging systems have shown remarkable similarities. They contain the usual request for target patterns for the measurement of MRTD, NETD, SiTF for the infrared thermal imager and similar patterns for measuring CTF and SNR for the visible imager. The combined systems almost invariably include some type of laser designator/rangefinder in the total package requiring the need for LOS registration among the various individual units. Similarities also exist in that the requests are for large collimator apertures and focal lengths for projecting the desired signals into the unit under test apertures. Diversified Optical Products, Inc. has developed and is continually improving test station hardware and software to provide modularity in design and versatility in operation while satisfying individual test requirements and maintaining low cost. A high emissivity, DSP controlled, high slew rate, low cost, blackbody source with excellent uniformity and stability has been produced to function as the driver for thermal image target projectors. Several types of sources for producing energy in the visible portion of the spectrum have been evaluated. Software for selection of targets, sources, focus and auto- collimation has been developed and tested.
Diversified Optical Products has designed an integrated lens, blackbody reference sources, and source control electronics for a mid-range IR Radiometric lens/staring focal plane array system. The purpose of the system is to be able to accurately correlate objects within the field of view of the system to two known, calibrated, and controllable blackbody sources also within the field of view. The two internal blackbody sources are thermoelectric cooler based, and their output is optically relayed to an internal image plane of the lens. The optical system also incorporates a neutral density filter wheel which attenuates the scene radiance so that both the blackbodies and the scene radiance can be brought into the dynamic range of the focal plane array. The goal of the design effort was to manufacture a highly accurate, field portable radiometric instrument. The specific design areas which where focused upon were: matching the optical design of the lens system with the camera design; controlling the radiometric properties of the optics, optical design requirements for the projection of the blackbody sources within the system field of view; and calibration requirements and methods for the total radiometric system.