In the field of acoustic sensing, compared with traditional acoustic sensors, fiber-optic distributed acoustic sensing (DAS) system is a revolutionary technology with many unique capabilities, such as high sensitivity, large sensing scale, real-time dynamic strain detection, excellent compatibility to standard optical fibers. However, DAS is limited by the single-component sensing characteristic of fiber itself, 3-component (3C) DAS technology is still a major challenge to date. 3C-DAS is of great significance to acoustic target tracking aloft and underwater, as well as seismic exploration underground. In this paper, we demonstrate a 3C fiber-optic quasi-distributed acoustic sensing (QDAS) system to detect 3C strains applied to optical fibers, which are mounted on 3C elastomers. 3C strain changes when placing the acoustic source at different positions. We use an ultra-sensitive DAS (uDAS) system with ~5 pε/√Hz strain sensitivity to detect the acoustic field. When the acoustic source is placed 0.5m away from the elastomers, 3C strain detected by uDAS are 5.70 nε, 6.37 nε and 35.88 nε, respectively. The experimental results verify the feasibility of the proposed 3C-QDAS scheme.
KEYWORDS: Sensors, Infrared sensors, Target detection, Signal to noise ratio, Interference (communication), Data processing, Infrared radiation, Signal detection, Infrared detectors, Information technology
This paper combines the information processing technology for target detection with the sensor parameter design. A design method which is suitable for the staring infrared sensor in geosynchronous orbit has been proposed. The signal-to-noise ratio (SNR) has been introduced to evaluate the detection performance. The sensor temporal-spatial noise and background clutter time-domain residual have been comprehensively analyzed. First, the temporal noise and the spatial noise have been separated and compared, and then the background clutter and time-domain residual with different ground sample distance (GSD) have been analyzed based on the on-orbit remote sensing image. The results showed that selecting the appropriate GSD and applying the target detection method of time domain correlation, under the background-limited photodetection (BLIP), the design threshold of the noise equivalent target (NET) can be improved, and the detection and information processing efficiency can be maximized. The method proposed in this paper provide information for the design and optimization of space-based staring infrared sensor parameter.
The energy focus ability of optics system is defined as the ratio of the energy contained in a pixel to the total energy of the dot diffusion function, which is one of the evaluation indexes of some optical systems. the energy focus ability of the room temperature optical system is usually tested by PSF test equipment. The ground PSF testing equipment works at room temperature and is sensitive to vibration, so it is difficult to carry out stability test in the vacuum and low temperature testing equipment. Therefore, the cryogenic optical system generally uses the point source target imaging method to carry out energy focus ability test. The traditional calculation method starts from the point target image of spot, the energy focus ability is calculated by dividing the gray value of the central pixel of the imaging spot by the sum of the gray value of the surrounding neighborhood pixels. Because the point source target used in the test has a certain size, it will affect the calculation results, so the calculation results are smaller. In addition, the center of central pixel of the detector and the center of the point target dispersion cannot be completely coincided in the actual measurement, and the calculation results are smaller due to the deviation of the center of mass. In this paper, through the establishment of point source target imaging model, the link of error correction is obtained, and a calculation method of the energy focus ability based on sampling correction is designed. This method first calibrates the PSF of the system through the target test image, and then uses the deconvolution algorithm to solve the PSF, and then completes the calculation of the energy focus ability. Because this method eliminates the influence of center offset and target size, it can effectively reduce the calculation error. This algorithm is verified in the room temperature optical system. The results show that compared with the traditional point source method, it is closer to the test results of ground PSF equipment and more accurate.
The Segmented Planar Imaging Detector for Electro-optical Reconnaissance system obtains target information through microlens and photon integrated circuit, which has the characteristics of small size, light weight and low power consumption, and is one of the research directions of high-resolution remote sensing in the future. This paper analyzes the influence of different waveguide offsets on the coupling efficiency of the system. The maximum coupling efficiency is 0.8145 without waveguide offset, and decreases rapidly with the increase of the offset. Finally, the calculation method of the optimal F number of microlens array is given.
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