Effective detection of ocean material profile distribution plays a vital role in marine biological research, protecting ocean ecological environment and resource utilization. Compared with other detection technologies, lidar has the advantages of all-weather, high temporal-spatial resolution and rapid and efficient access to its vertical distribution information. Lidar is one of the important means to detect the environmental parameters of ocean profile. Firstly, the basic working principle of lidar system is introduced, the characteristics of Raman lidar, Brillouin scattering lidar and fluorescence detection lidar are reviewed. Then the existing problems of lidar technology in detecting the vertical distribution of marine materials are discussed, finally, the development trend of this technology is prospected.
Airborne laser bathymetric system has great advantages in shallow sea bathymetric mapping due to its no blind area, high accuracy and high density data. By using Monte Carlo method and radiation-transport equation, the spatial distribution of the signal spot on the sea surface is calculated respectively. The results show that the spatial distribution of the signal spot returned to the sea surface is more extensive with the increase of the depth, and the power attenuation of the center of the spot is more serious. In this paper, signal to noise ratio (SNR) is used as the performance evaluation criterion of laser bathymetry system, and the requirements of field of view for signal detection under different depth are analyzed. The analytic results will provide support for the design and optimization of the laser bathymetric system.
The earth’s gravity field reflects the spatial distribution, movement and change of the earth’s mass. High precision gravity field is one of the main tasks of geodesy. The feasibility research of future China's satellite gravity mission(CSGM) were carried out, the satellite to satellite tracking in the low low mode was selected in the future satellite gravity measure. A precise laser ranging system is a key component to CSGM. In this paper, a laboratory breadboard heterodyne laser interferometer was built, experimental result demonstrated that laser ranging performance in laboratory distances was 1 nm@0.01Hz and below1nm@1Hz in translation measurement, and can meet the demand of CSGM mission.
Due to its advantages on the cost, power and size, the study of the CMOS image sensor is considered as an important direction of the development of low-light-level image sensor. However, the sensitivity of current CMOS image sensor does not satisfy the low-light-level application requirements. This paper introduces several key techniques on how to improve the sensitivity of CMOS image sensors. We introduce a novel CMOS low-light-level image sensor based on Geiger mode avalanche photodiode (GM-APD) and digital TDI technology. Noise characteristics and complete signal-tonoise ratio(SNR) theoretical models are constructed for both sensors. A comparison of SNR performance of two image sensors is also done by numerical simulation in this paper. The results show that the novel CMOS low-light-level image sensor outperforms EMCCD at the very low light level.
Airborne photoelectric reconnaissance system with the bore sight down to the ground is an important battlefield situational awareness system, which can be used for reconnaissance and surveillance of complex ground scene. Airborne 3D imaging Lidar system is recognized as the most potential candidates for target detection under the complex background, and is progressing in the directions of high resolution, long distance detection, high sensitivity, low power consumption, high reliability, eye safe and multi-functional. However, the traditional 3D laser imaging system has the disadvantages of lower imaging resolutions because of the small size of the existing detector, and large volume. This paper proposes a high resolution laser 3D imaging technology based on the tunable optical fiber array link. The echo signal is modulated by a tunable optical fiber array link and then transmitted to the focal plane detector. The detector converts the optical signal into electrical signals which is given to the computer. Then, the computer accomplishes the signal calculation and image restoration based on modulation information, and then reconstructs the target image. This paper establishes the mathematical model of tunable optical fiber array signal receiving link, and proposes the simulation and analysis of the affect factors on high density multidimensional point cloud reconstruction.
Squeezed state light field can surpass the shot noise limit and improve the signal-to-noise ratio of the sensor measurement. In this paper, based on optical parametric amplification (OPA), we present employed a semi-monolithic cavity and miniaturization design of optical parametric amplifier (OPA) to improve system stability. The infrared spectrum 1064nm quadrature squeezed state field of noise squeezing degree 6.75dB is obtained by pumped the PPKTP crystal via 532nm laser. This work provides a practical light source for quantum sensing detection.
Long baseline optical interferometry, by combining the lights from widely-distributed telescopes, is shown to afford pronounced improvement in the imaging resolution in comparison with a single telescope. However, the noise and photon loss in the transmission between the telescopes would limit the length of baseline of interferometer to a few hundred meters. Here, we present a scheme for enhancement of long baseline optical interferometer by using quantum resources- noiseless linear amplifier (NLA) and displacement operation at the photon transmission channels. We exhibit this enhancement quantitatively by calculating higher fisher information compared with those of conventional optical interferometer.
There has been much recent interest in quantum technology for applications to high resolution imaging and interference measurement. Due to noise and photon loss in the transmission between the telescopes, the current optical interferometers have quite limited baselines to a few hundred meters at most, which limit the resolutions. Here we propose to use noiseless linear amplifier (NLA) to reduce optical loss in the transmission. We also show that NLA can be further improved with local squeezing operator. We envisage that our analysis on this squeezing operator assisted NLA method could help to develop higher resolution interferometers, which would have many applications in stellar observation.
A quantum-enhanced receiver that uses squeezed vacuum injection (SVI) and phase sensitive amplification (PSA) is in principle capable of obtaining effective signal to noise ratio (SNR) improvement in a soft-aperture homodyne-detection LAser Detection And Ranging (LADAR) system over the classical homodyne LADAR to image a far-away target. Here we investigate the performance of quantum-enhanced receiver in Λ-type soft aperture LADAR for target imaging. We also use fast Fourier transform (FFT) Algorithm to simulate LADAR intensity image, and give a comparison of the SNR improvement of soft aperture case and hard aperture case.
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