With the improvement of spatial resolution, the focal length of space cameras and spectral imagers become longer. The thermal stability of image stability is more sensitive, with the temperature, especially in VNIR (visible and near-infrared). To solve the thermal stability of R-C(Ritchey-Chrétien) long focal length fore-telescope system, the relevant factors are discussed, on the basis of the LASIS(Large Aperture Static Imaging Spectrometer), and the change in the spacing between primary mirror and secondary mirror with temperature is proposed. Base on the calculation in theory, the method of mechanical passive athermalization design is developed. Mechanical test results indicate that the first natural frequency is 195Hz, above the 100 Hz. The thermal experiments show that the stability of primary mirror and secondary mirror spacing is 0.5μm.℃-1 , consisting with the FEA(Finite Element Analysis) value
Blood glucose level has important significance for medical diagnosis. Blood glucose measurement in traditional methods requires collecting blood samples several times a day, which causes discomfort, environmental pollution and so on. As a "fingerprint" spectrum for molecular recognition, Raman spectroscopy has attracted attention in blood glucose measurement. However, blood glucose level is low and spectral signal of glucose is easy to be influenced by noise and other components. To improve accuracy of blood glucose concentration estimation by Raman spectroscopy, we carried out the Raman blood glucose measurement in vitro, the interferograms of blood samples in different glucose concentrations were measured by the self-developed Spatial Heterodyne Raman Spectrometer (SHRS), and converted the interferograms to one-dimensional spectroscopic data using Fourier transform. In order to get data with higher quality, we used wavelet decomposition to remove the noise and sparse representation to remove the signal baseline. Then, selected the spectroscopy at 500-2500 cm-1 as input, and the corresponding blood glucose concentration value as label, use particle swarm optimization-support vector regression (PSO-SVR) algorithm to construct the blood glucose concentration estimation model. The results show that the R2 of test set is 0.8041 and the RMSE is 1.8580. And the accuracy of blood glucose concentration estimation was evaluated by the Clark Error Grid. The model based on PSO-SVR can achieve accurate estimation of blood glucose concentration. This method has important research significance and application potential for blood glucose measurement.
A Doppler asymmetric spatial heterodyne (DASH) interferometer was designed to measure atmospheric winds at a height of 60 to 80 km by observing the airglow emission line of molecular oxygen at 867 nm. The designed monolithic DASH interferometer exhibited decent thermal stability. The phase thermal drift of the fabricated interferometer obtained from thermal performance measurements was 0.376 rad / ° C. To accurately model and minimize the thermal drift performance of an interferometer in the design phase, it is necessary to include the influence of thermal distortion of the monolithic interferometer components. Therefore, an optical–structural–thermal integrated analysis method based on Zernike polynomials was proposed to accurately calculate the phase thermal drift of the interferometer. The optical model modified by the finite-element method calculated the phase thermal drift to be 0.420 rad / ° C, which agreed with the experimental result within 11.7%. This analysis method can accurately calculate and optimize thermal stability during the design of a DASH interferometer.
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.
As a new type of wind field detection technology, Doppler Asymmetric Spatial Heterodyne(DASH)can invert information such as atmospheric wind speed by monitoring the Doppler frequency shift of the absorption line or emission line of the atmospheric composition. It is widely used in the detection of middle and upper atmospheric wind fields. In this paper, a flexible support structure suitable for DASH interferometer is designed, so that the bonding process between different materials has a high safety margin in environmental testing. After modal analysis and random vibration analysis of the whole structure, the results show that the design meets the requirements. First, the fundamental frequency of the interferometer (765.79Hz>100Hz) meets the requirements of general satellites for the load; secondly, the random vibration analysis results show that the bonding stress between the surfaces is less than the allowable stress of the material (2MPa<14MPa), and it has a certain safety margin (>2); finally, the optical parts and structural parts did not collide with the structural parts during the vibration process, and the flexible structure did not undergo plastic deformation, and the whole structure of the interferometer was safe and reliable
The main propose of this paper is to discuss the possibility of a space-based early warning technology for missiles in boost phase based on the near-infrared fine spectrum of potassium atoms in the exhaust plume. Emission transfer link from the exhaust plume to the detector is established in combination with the observation model of satellite and target on the ground. Line-by-line integral method is used to calculate the characteristic spectrum of potassium atoms. The result shows the potassium line have high spectral emissivity and narrow bandwidth. The analyses on the atmospheric transmission and background radiation indicate that the atmospheric transmission of the 769.896 nm potassium line is higher than that of the 766.490 nm potassium line which lies on top of an O2 line, and the irradiance of the 769.896 nm line is stronger than that of background and the 766.490 nm line. Considering atmospheric transmission and background radiation, it is suitable to choose the 769.896 nm line to detect the exhaust plume of the missile. According to the characteristic of potassium atoms emission line with narrow bandwidth, a 1.2 nm wide filter centered on 770nm is used to extract target signal. The maximum detection range and other indexes are evaluated. The simulation results show that ultra-narrow band filter can achieve a large degree of background suppression, and the system performance indexes meet the detection requirements. Therefore, it is feasible that missile detection can be realized by using near-infrared fine spectrum of potassium atoms.
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.
Doppler asymmetric spatial heterodyne spectroscopy (DASH) is a new technology for measuring upper atmospheric winds by observing the Doppler shift of atmospheric emission lines from a satellite using a limb viewing geometry. The real-fringe DASH interferometer is a modification of conventional DASH interferometer; it keeps the advantages of the conventional one. Moreover, this interferometer will not need exit optics to image the superposed fringes onto the detector; it will be more compact and lightweight, making it suitable for space-based platforms. We describe the concept of the new interferometer and present the exact expression of spatial frequency and phase of the interferogram. We also describe design and simulation of a real-fringe DASH interferometer for observation of the O [1D] 630nm emission. The simulation results agree with the theory.
Spatial heterodyne spectrometers have been used in multiple scientific studies since their invention and early
development. Broadband spatial heterodyne spectrometers also have the advantages of large etendue, high spectral
resolving powers, and high data collection rates as traditional spatial heterodyne spectrometer. Basic theory, design and
performance parameters, breadboard experiment for a broadband, high-resolution spatial heterodyne spectrometer are
reported. The experimental spatial heterodyne spectrometer achieves a design resolution 0.39cm-1. Firstly, it is
demonstrated that broadband spatial heterodyne spectrometer have the advantages of wide spectral coverage and high
spectral resolving power simultaneously; secondly, the effects of optical defects on the system are discussed; thirdly,
Two dimension interference data procession also is mentioned.
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