Infrared detection technology is getting more and more attention, with the rapid development of infrared remote sensing application. Among them, low temperature infrared spectroscopy detection technology is an important development direction in the future. Infrared detection technology is a kind of target detection technology, using the infrared radiation characteristics of substances to different wavelengths. Infrared spectrometer is an important instrument to realize infrared detection technology. This type of spectrometer has been popularized and applied. The imaging spectrometer can reflect the spatial information and spectral characteristics of the observation target. With the improvement of spectral imaging resolution, the signal-to-noise ratio of imaging system is required to increase, which is the technical difficulty of low-temperature infrared spectroscopy. At present, noise reduction through low temperature is the main method. Therefore, infrared detection technology to work in a lower temperature direction. Furthermore, it promotes the progress of low temperature infrared spectroscopy technology. This paper summarizes and compares the development status of low temperature infrared spectrum detection technology. Thus, the key technology of low temperature detection spectrum is extracted. The low temperature infrared detection technology is classified according to the development status of low temperature infrared optics, low temperature support technology and low temperature refrigeration technology. Summarize the shortcomings of domestic existing technology and look forward to the future development direction.
To address the problem that bonding can lead to a reduction in the surface shape precision of a space-bound mirror, relationships between mirror deformation, thermal stress, and curing shrinkage stress were studied, and a bonding microstress design route was proposed. The thermal stress and thermal deformation introduced by thermal expansion mismatch were eliminated through an athermal adhesive layer thickness design. The relationship between mirror deformation and the curing shrinkage of the adhesive layer was derived completely, and structural optimization measures for releasing the curing stress of the adhesive layer are given. Bonding stress analysis was conducted based on the equivalent thermal deformation method, and an optimal structure meeting the design requirements was obtained. Finally, bonding of the mirror assembly was completed via this route, and the measured surface shape precision was stable at 0.0225λ. The theoretical analysis and experimental study demonstrate that this bonding design method can predict the bonding stress in the assembly process, making the follow-up bonding result controllable. These results should provide an excellent reference for the design and high-precision integration of large-aperture mirrors.
In order to solve the problems of long manufacturing cycle and high processing cost of mirrors in reflective optical systems of space cameras, a method for manufacturing metal mirrors based on additive manufacturing process is proposed. This paper designs an open honeycomb structure on the mirror backplane, mirror blank is prepared by additive manufacturing technology. Preliminary improvement of surface quality with rough machining and diamond turning. Then, a high-precision mirror surface is obtained through surface modification and secondary diamond turning. The diameter of the prepared mirror is 110mm, mass reduction rate of 70% and surface shape accuracy is better than λ /15 RMS( λ =632.8nm).The results show that the metal mirror prepared by this process can meet the requirements of high-precision reflective optical systems. The research work in this article can provide technical reference for the application of additive manufacturing technology in the field of optics. It has important reference and guiding significance for the research and application of related fields.
The curved prisms have been widely used as a light splitting element because of its own focal power and can be set in nonparallel light path. When the effective light transmission area of large-size curved prism is rectangular or elliptical, it can be processed into rectangular optical elements during processing, which can reduce the volume and mass of the instrument on the one hand, and effectively block the stray light outside the field of view on the other hand. Adhesive fixation is one of the common fixation methods of optical elements, which is applied in many launched spaceborne remote sensors. However, the adhesive bonding process and adhesive strength are unstable and the bonding reliability is poor, resulting in the calculated theoretical bonding area and adhesive layer thickness are often difficult to meet the requirements of complex mechanical and thermal environment. The rigid-flexible dual mode coupling support structure for space-based rectangular curved prism was firstly introduced. And then the tensile and shear tests on the epoxy adhesive used in this project was carried out and the bonding area based on the strength test was designed. On this basis, the mechanical test of the simulator mirror group was carried out to verify the reliability of the bonding area and the design of the support structure. Finally, three bonding postures were simulated analysis and tests including prone, lateral and vertical bonding. The results showed that the vertical bonding was the smallest surface shape errors of the curved prism. Based on this bonding attitude, the bonding and mechanical tests of the curved prism were completed to verify the reliability and rationality of the bonding process.
With the increasing demand of infrared detection, the infrared cold optical technology has developed rapidly in recent decades. The low temperature deformation of infrared optical elements is one of the key factors restricting the development of infrared cold optical technology. The processing and assembly of optical subassemblies and support structures are carried out at room temperature and pressure, while the actual working environment of infrared system is relatively low temperature environment, which can vary by 200 degrees Kelvin or more. Therefore, the temperature adaptability of the support structure is strictly required. The optimal design flexible support of the 70mm diameter single crystal lens made by germanium was carried out to ensure that the component surface shape reached (1/6) λ and the natural frequency was above 200HZ at 100K low temperature in this paper. At the same time, the ISIGHT integrated optimization method was used to optimize the flexible support structure. The multi-objective integrated optimization of key dimensions of flexible support was completed, aiming at maximizing the fundamental frequency of the system and minimizing the lens surface shape errors. Finally, the optimal size was selected to complete the flexible structure design. In this paper, an adaptive flexible support structure for cold optical lens with three layers of stress release was designed by multi-objective integrated optimization method. Meanwhile, its performance was verified by low temperature tests. The results verified the reliability and the feasibility of the structure design and analysis.
To ensure the high surface accuracy and high thermal stability of space mirror, a lightweight design for the Φ514mm ULE primary mirror of a space remote sensor and flexible support structure with three-point was carried out. By further optimizing the parameters of the flexible supporting structure, the requirements of the optical index were met. The finite element model of the mirror assembly was established, and the static and dynamic characteristics of the assembly were analyzed. The results showed that the surface shape accuracy (RMS) of the mirror assembly is better than 8 nm under a load case of 1g gravity when the optical axis is level, and the first-order natural frequency of the component is 254 Hz. Finally, a mechanical test was carried out on the mirror assembly. The test results showed that the first-order frequencies of the three directions of the mirror assembly are all greater than 100 Hz , the error between the test data and the finite element analysis results does not exceed 10%. Analysis and test results showed that, the reasonable support structure design can effectively lower the change of the mirror surface shape caused by assembly stress and thermal stress, and has good dynamic performance. It is verified that the mirror and its supporting structure designed in this paper are reasonable, which provides reference and ideas for the design of flexible supporting structure of similar space mirror.
Spatial heterodyne spectroscopy for long-wave infrared identifies an ozone line near 1133 cm-1 (about 8.8 μm) as a suitable target line, the Doppler shifts of which are used to retrieve stratosphere wind and ozone concentration. The basic principle of Spatial Heterodyne Spectroscopy (SHS) is elaborated. Theoretical analyses for the optical parameters of spatial heterodyne spectroscopy are deduced. The optical system is designed to work at 160 K and to maximize the field of view (FOV). The optical design and simulation is carried on to fulfill the requirement. The principle prototype was built and a frequency-stable laser was used to conduct the experiment. Result shows that the designed interferometer can meet the requirement of spectral resolution (0.1 cm-1 ) and that the spatial frequency of fringe pattern is consistent with the theoretical value at normal temperature and pressure.
To minimize the assembly stress and thermal stress introduced by the support structure, and ensure the high surface accuracy and high thermal stability of space mirror. An ultra-lightweight design of secondary mirror was carried out for some space remote sensor, and three tangential bipods were used for quasi-kinematic support. Firstly, the design principle of quasi-kinematic support structure was investigated, and advantages of bipod kinematic support were analyzed from the angle of degree of freedom decoupling. Based on structure designed above, the finite element model was established. Taking surface accuracy of the mirror as optimization objectives, the integrated optimization method was adopted to extract the structural parameters with high sensitivity on the surface accuracy in the flexible support structure, and parameters optimization design was carried out. Finally, the static and dynamic characteristics of the optimized mirror assembly were analyzed. The analysis results showed that the surface shape accuracy (RMS) of the mirror assembly is better than 1 nm under a load case of 1g gravity when the optical axis is level. Surface accuracy (RMS) is better than 2 nm under the load case of 4℃ uniform temperature rise. The first-order natural frequency of the secondary mirror assembly is 587 Hz. The optimized mirror support structure can well unload the additional deformation caused by the support structure, and has good dynamic stiffness, which verifies that the designed mirror and its support structure are reasonable, and the optimization design method is reliable. This paper provides a reference and idea for the design of flexible support structure of space mirror.
Hyperspectral imaging (HSI) acquires a three-dimensional dataset called hypercube, with two spatial dimensions and one spectral dimension. HSI is an emerging imaging modality for various medical applications, especially in disease diagnosis of early and biomedical research based on their unique spectral signatures. A visible-near-infrared HSI for microspectroscopy is designed, the measured spectrum is from 450 nm to 900 nm, which is sampled by 256 spectral channels. The spatial resolution is 1.25μm.The modulation transfer function (MTF) value of full spectrum and full field of view is close to the diffraction limit. At last, this microspecroscopy have been fabricated and preliminary tests have been implemented. The results indicated this visible-near-infrared hyperspectral microscopy optical systems have excellent optical performances. This hyperspectral microscopy will be well developed and used in the life sciences fields.
Doppler asymmetric spatial heterodyne spectroscopy (DASH) with its high stability and feasibility of synchronized calibration highly suit for the wind field observation. By applying the synchronized calibration, the thermal phase distortion of observation emission line could be corrected greatly based on the similarity of thermal effects between observation emission line and calibration line. While, the correction residual which could be called relative thermal phase distortion still influence the wind measurement precision significantly. In this manuscript, we discuss and analyze the relative phase distortion of DASH theoretically and practically based on the DASH retrieval theory and the experiment. Firstly, based on the retrieve theory of DASH, we analyze the relationship between the relative phase distortion and the precision of the wind measurement. It is found that 1.528mrad phase error equal to 1m/s wind measurement error for the DASH developed by our research group. Secondly, based on the DASH developed by our research group, laser of 632.8nm and Ne lamp are employed as input source to test relationship between relative phase distortion and internal temperature of interferometer. According to the experiment result, the relative phase distortion change weekly with the variation of temperature between 25.14°C and 25.67°C. While, the relative phase stability decrease rapidly in other else temperature range. Lastly, according to the experiment result, we analyze the major source of relative phase distortion which could make contribution to reducing the relative phase error, which could increase the wind measurement precision, in the future research.
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