The high-precision self-calibration radiation reference source is currently the research focus of satellite remote sensing calibration. In order to meet the requirements of quantitative applications such as climate monitoring, low-light radiation metering and single photon source radiance measurement, in view of the application requirements and technical requirements of visible to near infrared low-light radiometer, a compact three-channel low-light radiance meter based on correlated photon self-calibration is designed. This design method can improve the measurement accuracy of low light irradiance by using objective physical effect instead of physical standard, reducing the cumulative error caused by standard transfer chain. The absolute calibration of the detector responsivity can be achieved by the spontaneous parameter downconversion effect, and the absolute radiation observation can be achieved without relying on the external reference. Based on this study, combined with the special application requirements of radiance meter, a numerical model of spectral rate and geometric transmission characteristics of wide spectrum correlated photons is established, and two basic operating modes of self-calibration and radiation observation are determined. The interaction between 355 nm pump source and nonlinear medium generates three-wave mixing, and the correlated photons are generated by class I non-collinear spontaneous parametric downconversion, the combined effect of monochromatic pump photon flow and quantum vacuum noise on non-centrosymmetric nonlinear crystal makes each incident photon spontaneously split into two photons with lower energy with a certain probability, called signal photons and idle photons respectively, they have a wide sptrum distribution from pump wave frequency to lattice resonance frequency. Correlated photon source has the technical characteristics of time and space correlation, natural wide spectrum and absolute reproducibility, so it has high absolute accuracy. Integrated design of self-calibration and radiation observation can monitor and correct changes in response characteristics in real time, maintain long-term stability of response characteristics, and improve traceability and accuracy of observation data. This design method solve the key technologies such as preparation and value transfer of correlated photon sources, suppression of pump stray light, high precision and high efficiency coupling of correlated photons, UV radiation resistance of space single-photon detectors, packaging reinforcement technology of space single-photon detectors, self-calibration and integrated design of radiation observation. The spectral measurement range of the low-light radiance meter is from 460 nm to 1 550 nm,the measurement range of radiance is 1x10(-9)similar to 1x10(-6) W/(cm(2)center dot sr center dot nm). In the design,the integration,miniaturization and modularization of the whole system are considered,and the eight spectral bands are integrated into a three-channel structure, solving the preparation of wide spectrum dependent photon source, optical multiplexing of calibration optical path, radiation measurement, high precision coincidence measurement and full optical path calibration of radiance meter, and achieving high precision radiation observation from visible to near infrared and periodic self-calibration research targets. In the self-calibration mode,the multiplex optical path module periodically introduces the spontaneous parametric down-conversion correlated photons,and the photon counting and coincidence detection module are used to calibrate the absolute quantum efficiency of the three channels. In the radiation observation mode,the multiplex optical path module introduces the low-light level target radiation and obtains the absolute spectral radiance of the observation target in the band of 460 similar to 1 550 nm at the same time. The calibration coefficient obtained by the self-calibration mode is used to correct the observation results. The effects of link error limited by radiation reference value transfer,optical decay of optical path and electronic decay of optical path on the measurement accuracy of microradiance are fundamentally solved. The visible near-infrared band adopts free space coupling mode and the short-wave infrared band adopts multi-mode fiber coupling mode. Through design optimization analysis,the focusing spots of the first and second channels meet the 300 mu m pixel requirement of Si single photon detector, and the focusing spot of the third channel meets the 62.5 mu m core diameter and 0.22 numerical aperture requirement of multi-mode fiber,all of them can be received by the detector photosensitive surface,meeting the design objectives. The method based on correlated photon calibration does not need to trace the high-precision primary standard in the laboratory and the lengthy standard transfer chain. By using the correlated photon generated in the process of parametric down-conversion,the calibration source of time,space and polarization can be obtained,and the high-precision observation of the low-light spectrum radiance from visible to near infrared band can be realized. The solution to the scientific problem of low-light observation instrument in space platform measurement can obtain higher calibration accuracy,and play an important role in climate monitoring,low-light radiation metrology,single-photon source radiance measurement and so on.

Modulation transfer function (MTF) is one of significant parameters for designing and evaluating an photoelectric imaging system. As the traditional MTF measurement algorithm cannot meet the need of discrete sampling characteristics for photoelectric system, an automatic interpolaton and sub-pixel matching algorithm based on slit tilting method is proposed.Through the least-square analysis of line spread function (LSF),the tilting angle can be automatically calculated, and interpolaton of sub-pixel data can be precisely reconstructed. The noise of oscillation can be effectively restrained by a hanning window function. A device composed of target generator system, off-axis reflective collimator, mechanical adjustment, electrical control system, video acquisition module and comprehensive software was setup. The validity of the method was verified by experiments. The repeatability reached 0.007。

Streak images obtained by the streak tube imaging lidar (STIL) contain the distance-azimuth-intensity information of a scanned target, and a 3-D reconstruction of the target can be carried out through extracting the characteristic data of multiple streak images. Significant errors will be caused in the reconstruction result by the peak detection method due to noise and other factors. So as to get a more precise 3-D reconstruction, a peak detection method based on Gaussian fitting of trust region is proposed in this work. Gaussian modeling is performed on the returned wave of single time channel of each frame, then the modeling result which can effectively reduce the noise interference and possesses a unique peak could be taken as the new returned waveform, lastly extracting its feature data through peak detection. The experimental data of aerial target is for verifying this method. This work shows that the peak detection method based on Gaussian fitting reduces the extraction error of the feature data to less than 10%; utilizing this method to extract the feature data and reconstruct the target make it possible to realize the spatial resolution with a minimum 30 cm in the depth direction, and improve the 3-D imaging accuracy of the STIL concurrently.

With the development of the technology of streak tube device, the application of streak tube as a transient optical device is no longer confined to the field of high speed photography and optical spectroscopy. A streak tube imaging LIDAR (STIL) for underwater imaging is devised, the streak images are obtained, and the extraction of feature data and 3D reconstruction are performed. The difference in distance of the two objects, which is calculated by the theory, is close to the actual value, so the feasibility of using this system as laser imaging is verified. The experimental results show that the STIL has a high resolution, and has a good application prospect.

Laser range-gated imaging is one of the effective techniques of underwater optical imaging. It could make the viewing distance up to 4 to 7 times with the video image processing technology. Accordingly, the control and image processing technologies come to be the key technologies for the underwater laser range-gated imaging system. In this article, the integrated platform of controlling and digital video processing for the underwater range-gated laser imaging system based on FPGA has been introduced. It accomplishes both the communication for remote control system as the role of lower computer and the task of high-speed images grabbing and video enhance processing as the role of high-speed image processing platform. The host computer can send commands composed to the FPGA, vectoring the underwater range-gated laser imaging system to executive operation.

Laser Rayleigh-Brillouin scattering is a powerful diagnostic tool for the study of gas flow properties. It provides an effective method for non-intrusive measurement of density, temperature and velocity in the gas flow. The received scattered laser light power is proportional to the gas density, the linewidth of the Rayleigh-Brillouin scattering spectrum is related to the gas temperature, and the Doppler frequency shift of the peak of the Rayleigh-Brillouin scattering spectrum is related to the gas velocity. The Rayleigh-Brillouin scattering spectrum can be measured by a Fabry-Perot interferometer operated in the imaging mode where an intensified CCD camera is frequently used to record the interference patterns of the Fabry-Perot interferometer. The Rayleigh-Brillouin scattering spectrum is then reconstructed from the measured data deconvolved with the Fabry-Perot instrument function. In this paper, the analysis and design of an imaging Fabry-Perot interferometer for the measurement of the Rayleigh-Brillouin scattering spectrum in the gas flow is presented. Some factors that limit the performance of the imaging Fabry-Perot interferometer are analyzed and discussed.

In the preceding paper (referred to here as paper I), we presented a general signal-to-noise performance analysis of a streak tube imaging lidar (STIL) system within the framework of linear cascaded systems theory. A cascaded model is proposed for characterizing the signal-to-noise performance of a STIL system with an internal or external intensified streak tube receiver. The STIL system can be decomposed into a series of cascaded imaging chains whose signal and noise transfer properties are described by the general (or the spatial-frequency dependent) noise factors (NFs). Equations for the general NFs of the cascaded chains (or the main components) in the STIL system are derived. This work investigates the signal-to-noise performance of an external intensified STIL system. The implementation of the cascaded model for predicting and evaluating the signal-to-noise performance of the external intensified STIL system is described. Some factors that limit the signal-to-noise performance of the external intensified STIL system are analyzed and discussed.

Streak tube imaging lidar (STIL) is an active imaging system using a pulsed laser transmitter and a streak tube receiver to produce 3D range and intensity imagery. The STIL has recently attracted a great deal of interest and attention due to its advantages of wide azimuth field-of-view, high range and angle resolution, and high frame rate. This work investigates the signal-to-noise performance of STIL systems. A theoretical model for characterizing the signal-to-noise performance of the STIL system with an internal or external intensified streak tube receiver is presented, based on the linear cascaded systems theory of signal and noise propagation. The STIL system is decomposed into a series of cascaded imaging chains whose signal and noise transfer properties are described by the general (or the spatial-frequency dependent) noise factors (NFs). Expressions for the general NFs of the cascaded chains (or the main components) in the STIL system are derived. The work presented here is useful for the design and evaluation of STIL systems.