The design of the dual-channel projection collimator for the dynamic infrared scene projector is introduced in this paper. The optical system is the combination of a telescope system and two imaging systems of the target channel and the inference channel. The scenes from two optical channels are combined into one scene by the beam combiner. The optical system consists of twelve elements and aspheric surfaces are used in the imaging system to increase the image quality and simplify the configuration of the optical system. The optical system is capable of operation over the 8~12μm wavelength range and testing an infrared seeker over 12°field of view (FOV). The effective focal length of the optical system is 228.3mm and the exit pupil distance is 800mm.The image quality and the formats of the system meet the requirements of the projector.
Dynamic infrared scene projection system can provide infrared detectors such as infrared seeker with target infrared radiation characteristics equivalent to the real environment in the laboratory. It can produce dynamic infrared scene to simulate the infrared radiation characteristics of real objects and their environment. The system constitutes a hardware in the loop simulation test system together with multi axis motion platform, seeker system, control system and other related equipment. This paper presents a scheme of infrared scene projection system based on dual digital micro mirror device (DMD), describes the main functions and composition of the system, and focuses on the working mechanism of dual DMD to improve gray level and frame rate. The system consists of dual DMD infrared scene projector, synchronization control device and scene generation computer. Two DMDs are used to modulate the infrared radiation intensity of each frame image and the spatial distribution characteristics of the image, and jointly complete the modulation of the gray level and spatial distribution of the output image. At the same time, the synchronization control device works synchronously with the test equipment or seeker to ensure that the generated infrared field frame rate is synchronized with the image collected by the test system. At present, the high frame rate infrared scene projection system based on dual DMD can meet the index requirements of maximum frame rate of 100Hz and minimum integration time of 2ms, which can vary with the synchronization signal frequency, and meet the integration time and synchronization test requirements of a variety of infrared detection equipment.
An infrared imaging spectrometer based on a variable gap interferometer is introduced, which is working in 7.7μm~14μm, and often used in spectral measurement, camouflage target detection and gas component identification. In this paper, the wedge prism shapes processed by grinding and diamond knife turning is compared, which affects the phase distribution near zero phase of the interferogram, and results in the difference of spectrum in the result. Finally, the turning process with less damage to the sharp edges was selected. An adjusting device and monitoring software are designed to ensure the symmetry of the wedge angle of the interference cavity with variable gap, so that two sides of the interferogram are sampled at equal intervals. The working mode is designed as the interferometer’s linear translation scan inside the imaging spectrometer. This working mode can reduce the volume of the system, and decrease the noise caused by the nonuniformity of the FPA response, improving signal-to-noise ratio. Stepper motor, rail and slide block are used to realize uniform reciprocating scanning. Finally, some measurement results using this infrared imaging spectrometer are presented.
Recently, hyperspectral image projectors (HIP) have been developed in the field of remote sensing. For the advanced performance of system-level validation, target detection and hyperspectral image calibration, HIP has great possibility of development in military, medicine, commercial and so on. HIP is based on the digital micro-mirror device (DMD) and projection technology, which is capable to project arbitrary programmable spectra (controlled by PC) into the each pixel of the IUT1 (instrument under test), such that the projected image could simulate realistic scenes that hyperspectral image could be measured during its use and enable system-level performance testing and validation. In this paper, we built a visible hyperspectral image projector also called the visible target simulator with double DMDs, which the first DMD is used to product the selected monochromatic light from the wavelength of 410 to 720 um, and the light come to the other one. Then we use computer to load image of realistic scenes to the second DMD, so that the target condition and background could be project by the second DMD with the selected monochromatic light. The target condition can be simulated and the experiment could be controlled and repeated in the lab, making the detector instrument could be tested in the lab. For the moment, we make the focus on the spectral engine design include the optical system, research of DMD programmable spectrum and the spectral resolution of the selected spectrum. The detail is shown.
With applications ranging from the desktop to remote sensing, the long wave infrared (LWIR) interferometric spectral imaging system is always with huge volume and large weight. In order to miniaturize and light the instrument, a new method of LWIR spectral imaging system based on a variable gap Fabry-Perot (FP) interferometer is researched. With the system working principle analyzed, theoretically, it is researched that how to make certain the primary parameter, such as, wedge angle of interferometric cavity, f-number of the imaging lens and the relationship between the wedge angle and the modulation of the interferogram. A prototype is developed and a good experimental result of a uniform radiation source, a monochromatic source, is obtained. The research shows that besides high throughput and high spectral resolution, the advantage of miniaturization is also simultaneously achieved in this method.
Interference imaging spectroscopy is the advanced subject among the infrared remote sensing, and it has become an important technique to detect spatial information and spectral information of targets. It has the advantages of high flux, high spectral resolution and high spatial resolution that can be used for detecting more details of the spectral and spatial information. Based on a Michelson interferometer with its mirrors replaced by corner-cubes, principles of a hand-held, static, long-wave infrared Fourier Transform(FT) imaging spectrometer using an uncooled microbolometer array are introduced. Because in such FT-based spectral imager, the interferogram is acquired over the whole field of the camera while the scene of interest scans the path difference range, vignetting should be strongly limited while keep the size of the interferometer as small as possible. Interferometer size is given and interferential light path is verified through TracePro software. First results of field and laboratory measurements using the spectral imager are presented. Remotely obtained spectrums collected with this instrument and with those of high precise Michelson spectrometer are compared, and the measured values turned out to be closely corresponded. The results, in turn, verified the feasibility of the systematic working mode. The resulting system tested here provides datacubes of up to 640×480 pixels over the 7.7~13μm spectral range, this wavelength range reveals important information about scenes such as gas or landmine detection, and the instrument has a spectral resolution of about 8cm-1 that fulfils the requirement for most targeted applications. Examples of sky and buildings detection are shown.
The research on infrared spectral target signature shows great military importance in the domain of IR detection Recognition, IRCM, IR image guide and ir stealth etc. The measurements of infrared spectral of tactical targets have been a direct but effective technique in providing signatures for both analysis and simulation to missile seeker designers for many years. In order to deal with the problem of dynamic target infrared spectral signature, this paper presents a new method for acquiring and testing ir spectral radiation signatures of dynamic objects, which is based on an IR imager guiding the target and acquiring the scene at the same time, a FOV chopping scan infrared spectral radiometer alternatively testing the target and its background around ir spectral signature.ir imager and spectral radiometer have the same optical axis. The raw test data was processed according to a new deal with method. Principles and data processing methods were described in detail, test error also analyzed. Field test results showed that the method described in the above is right; the test error was reduced smaller, and can better satisfy the needs of acquiring dynamic target ir spectral signature.
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