Optimization process is the one of the most crucial part of optical design due to it’s including weight, size and performance parameters. Current developments in optical and electronical technology reduce the size and weight of these systems and improve image performance. In this study, optical design of small diameter dual mode imaging infrared system will be summarized. Optical design is including prisms to provide wide field of regard which are rotated in roll axis to scan area. Optical design is also including a filter to split long-wave infrared and mid-wave infrared spectrums from each other. At the end optical design results and analysis will be given.
In this paper, different optical designs, which are composed of different MWIR optical materials, are utilized for passive athermalization and their performance in athermalization are analyzed. The optical designs are carried out by preserving the athermal property as well as keeping the image quality at higher levels within the working temperature between –40 ºC and +60 ºC. The passive athermalization process begins with the calculation of athermalization conditions of candidate material properties. By considering these conditions, athermal material pairs are chosen. To reduce optical aberrations, aspherical surfaces are utilized during the optimization process. At the end of the design phase, the performance of different configurations of athermal optical material pairs, which are enclosed by aluminum alloy housing material, are presented.
In this paper, different optical designs, which are composed of different LWIR optical materials, are utilized for passive athermalization and their performance in athermalization are analyzed. The optical designs are carried out by preserving the athermal property as well as keeping the image quality at higher levels within the working temperature between –40 °C and +60 °C. Our designs consist of two different infrared optical elements to maintain the focus positions as stable as possible within the working temperature. The passive athermalization process begins with the calculation of athermalization conditions of candidate material properties. By taking into account these conditions, athermal material pairs are chosen. The optical design begins with an optimization process using paraxial optics. In order to reduce aberrations such as coma, astigmatism, spherical and chromatic, aspherical surfaces are utilized during the optimization process. At the end of the design phase, the performance of different configurations of athermal optical material pairs, which are enclosed by aluminum alloy housing material, are presented.
In missile applications, new counter measure methods are getting more complex. To discriminate and detect counter measure and to understand target signature from scene is getting harder. Because of all that concerns, using triple-mode seeker for a system solution is a good solution for system total performance. By this way, tridifferent wavelength could be used for same system and same scene. In this study, triple mode system’s optical designs have been made for mid-wave infra-red imaging, long-wave infra-red imaging and short-wave infrared imaging. Optical designs performances have been illustrated in simulation results. Finally, conceptual design of triple mode seeker will be summarized.
Warfare environment get more complex day by days by developing technology. This improvements and complexity cause missile performance degradation. To eliminate these negative aspects, more technological and more complex systems and algorithm are used in new generation missile. Dual mode or triple mode seekers are produced to resolve these problems. More effective and more reliable system can be achievable by combination of different kind of working principle. In this study, cost effective imaging and signal processing solution combination is reviewed. Its conceptual design criteria are assumed in system level and both designs of systems are illustrated. In imaging part, uncooled long wave infrared is chosen for both cost effective and compactness. In signal processing part, four quadrant semi-active seeker is chosen for same reason. Finally, their performance results are shown.
The minimum resolvable temperature difference (MRTD) and minimum detectable temperature difference (MDTD) are widely accepted static performance test parameters that best describe the field performance of thermal imaging systems. MRTD test is measured by determining the minimum temperature difference between the 4-bar target and the background required to resolve the thermal image of the bars by an observer. On the other hand, MDTD test is measured by determining the minimum temperature difference between the target and the background, which is required to detect the target from the thermal image. Different temperature differences between the target and the background with different target spatial dimensions were used while conducting both MRTD and MDTD measurements using collimator test systems. In this study, to evaluate the field performance of various thermal imaging systems, MRTD and MDTD tests were applied. Then, infrared simulations of pinhole and 4-bar collimator static test system targets were described based on the electro-optical parameters of unit under test (UUT) including detector resolution, system SiTF (Signal Transfer Function), system MTF (Modulation Transfer Function) and total optical transmission. With these inputs, the infrared simulation images of pinhole and 4-bar targets, which have adjustable temperature difference and different spatial frequency, were obtained in MATLAB environment. Then, the infrared simulations of pinhole and 4-bar target images were verified with thermal imaging system.
In this paper, the optical design of an athermalised dual field of view step zoom optical system in MWIR (3.7μm – 4.8μm) is described. The dual field of view infrared optical system is designed based on the principle of passive athermalization method not only to achieve athermal optical system but also to keep the high image quality within the working temperature between -40°C and +60°C. The infrared optical system used in this study had a 320 pixel x 256 pixel resolution, 20μm pixel pitch size cooled MWIR focal plane array detector. In this study, the step zoom mechanism, which has the axial motion due to consisting of a lens group, is considered to simplify mechanical structure. The optical design was based on moving a single lens along the optical axis for changing the optical system’s field of view not only to reduce the number of moving parts but also to athermalize for the optical system. The optical design began with an optimization process using paraxial optics when first-order optics parameters are determined. During the optimization process, in order to reduce aberrations, such as coma, astigmatism, spherical and chromatic aberrations, aspherical surfaces were used. As a result, athermalised dual field of view step zoom optical design is proposed and the performance of the design using proposed method was verified by providing the focus shifts, spot diagrams and MTF analyzes’ plots.
This paper presents a methodology for designing an athermalised dual field of view zoom lens in long wave infrared (8μm - 12μm) spectral band by using the benefits of paraxial optics. By using this design methodology the optical designer can develop many types of complex optical systems in a straightforward way. The key feature of this design methodology relies on utilization of paraxial optics for defining the initial positions of the optical elements. The optical design is based on moving a single lens for changing the optical system’s FOV thereby reducing the number of moving parts and simplifying the assembly procedure of the system. The optical design begins with optimization process using paraxial optics. Then the optical design using paraxial optics is used as a template for designing the final optical system by lens material selection for compensating the shift in system’s focus due to thermal effects and lens thickness tuning.
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