2016 Vol. 45, No. 3
column
- Review
- Invited paper
- Infrared technology and application
- Laser technology and application
- Laser technology
- Photoelectric devices and microsystem
- Space optics
- Optical design and simulation
- Advanced optical material
- Laser radar technology
- Photoelectric navigation and control
- Spectrum detection and analysis
- Photoelectric measurement
- Optical communication and optical sensing
- Information acquisition and identification
2016, 45(3): 301001.
doi: 10.3788/IRLA201645.0301001
Dynamic precise measurement of movement information constructs the foundation of guidance,navigation and control of various vehicles. The inertial technology is the only independent means to establish the position and attitude reference of a vehicle in all kinds of environments, so it is the basis of dynamic precise measurement of movement information. The development of inertial technology, including optical gyroscope and its inertial navigation system, MEMS gyroscope and accelerometer, atom gyroscope and accelerometer, other kinds of gyroscope and accelerometer, micro-technology for positioning, navigation and timing, and inertial executer, was reviewed in this paper, and the main technology problems of these gyroscopes, accelerometers and inertial navigation systems which are needed to be resolved in aerospace field were proposed. The main application of these inertial technologies in domain aerospace field was described, including application in satellites, launch vehicles, manned aerospace and moon explore. Finally, three development trends of the inertial technology in aerospace field were given.
2016, 45(3): 302001.
doi: 10.3788/IRLA201645.0302001
Frame processing method offers a model-based approach to Inverse Synthetic Aperture Radar (ISAR) imaging. It also provides a way to estimate the rotation rate of a non-cooperative target from radar returns via the frame operator properties. In this paper, the relationship between the best achievable ISAR image and the reconstructed image from radar returns was derived in the framework of Finite Frame Processing theory. We show that image defocusing caused by the use of an incorrect target rotation rate is interpreted under the FP method as a frame operator mismatch problem which causes energy dispersion. The unknown target rotation rate may be computed by optimizing the frame operator via a prominent point. Consequently, a prominent intensity maximization method in FP framework was proposed to estimate the underlying target rotation rate from radar returns. In addition, an image filtering technique was implemented to assist searching for a prominent point in practice. The proposed method is justified via a simulation analysis on the performance of FP imaging versus target rotation rate error. Effectiveness of the proposed method is also confirmed from real ISAR data experiments.
2016, 45(3): 302002.
doi: 10.3788/IRLA201645.0302002
According to similarity principles, an infrared imaging experimental test system was set up based on scale model, several different working conditions in the condition of scale model were designed based vehicle volume, submerged depth, movement, wake discharging, and etc., so that it was possible to realize the static and dynamic thermal wake detection tests of scaled model. The aim is to determine the detectability of thermal wakes from submerged vehicle on one side, and find the influencing factors at thermal wakes detection and changing rules of the wakes to lay a foundation for future work.
2016, 45(3): 304001.
doi: 10.3788/IRLA201645.0304001
The first step of self-adaptive infrared stealth is the obtention of occlusion background image, this image is a part of the background which is covered by the object when the observer observes this object somewhere. When observing the object in different viewpoints, the background that is covered by the object is different, the object and the occlusion background have a relation of perspective projection. For obtaining the relation between object and the occlusion background, three coordinate systems were established which consist of object's body-fixed coordinates, viewpoint coordinates and thermal imager coordinates, then the corresponding model between the point on object and the point on the thermal image got by thermal imager was derived by coordinate transformation between these three coordinates. At last an experiment was carried out to verify the model, the result shows that the occlusion background is obtained in different viewpoints by this model. The model lays a foundation of practical engineering application.
2016, 45(3): 304002.
doi: 10.3788/IRLA201645.0304002
The advantages and disadvantages in nonuniformity correction(NUC) algorithms based on calibration and scene of infrared focal plane arrays(IRFPA) were analysed separately. The combined NUC algorithm was presented. The thermal imaging system extracted the gain and offset factor from the FLASH which storged beforehand according to the substrate temperature of the IRFPA at the moment of power on. These factor was adopted to remove the nonuniformity of the detector simply. Based on the analysis of the characteristic of residual noise after initial correction, the P-M filter was used to replace the linear spatial average filter in the Neural Network nonuniformity correction algorithm(NN-NUC),which could preserve the image edge. Experimental results show that the proposed algorithm can accelerate the rate of convergence, reduces the correction error largely, and avoids the image degradation caused by the response drift of IRFPA.
2016, 45(3): 304003.
doi: 10.3788/IRLA201645.0304003
The aim of this paper is to study and solve the disadvantage of standing wave on the damage detection by ultrasonic thermal wave testing technology. The vibration characteristics and acoustic chaos phenomena of the structure under ultrasonic excitation were numerically analyzed. Firstly, by establishing a composites finite model with a crack, the resonance models of the structure under different excitation frequencies were analyzed. It is found that the harmonic wave response of the structure under harmonic ultrasonic wave with the response frequency was equals to the excitation frequency, and the standing wave easily appeared. Then, by improving the composites finite model, the influences on the testing result caused by acoustic chaos were analyzed. The numerical results show that, under the same excitation frequency, the standing wave was effectively eliminated by acoustic chaos. Acoustic chaos is beneficial to the detection by increasing the surface temperature difference at the damage, and the probability of acoustic chaos generated is increased by increasing the excitation frequency. And the detection capability and conditions can be improved according to this result.
2016, 45(3): 304004.
doi: 10.3788/IRLA201645.0304004
To obtain the absolute radiation calibration coefficient of IRS B08 in 2013,TERRA/MODIS was used as the reference sensor, Qinghai lake was taken as the research object, twin-channel difference model was applied to cross-calibration. By comparing the influence of different observation angles and different of imaging receiving time on calibration precision, it can be concluded that the best cross-calibration condition is the observation angle within 30 and the difference of imaging receiving time about 1 hour. Under this condition, calibration accuracy of regression fitting is the highest. According to the precision verification using satellite-ground synchronous experiment data around Ningde area on 26, October, 2013, result shows that error of apparent radiance and brightness temperature is within 0.02 Wm-2m-1sr-1 and 0.15℃ respectively. Besides, compared with the historical calibration coefficients from 2008 to 2010, the new calibration coefficients of 2013 increased by 98.50%, 98.24%, 90.21%, 20.87% and 98.31% respectively. Overall, the obtained calibration coefficient has a high accuracy, that can be used to the IRS B08.
2016, 45(3): 304005.
doi: 10.3788/IRLA201645.0304005
Research on the detection reliability of ultrasonic infrared imaging is of great importance. Probability of detection for different defects under given test conditions is workhorse statistical technique for the detection reliability assessment. In this paper, a series of 45 steel containing fatigue cracks were tested. Experimental results show that the increase of the crack size will enhance the crack heating response, and the relationship between the logarithmic form of measured response and the crack size appears to be linear. Based on the above statistic characteristics, the linear regression analysis and Delta method were adopted to estimate the probability of detection and its confidence interval. The research conclusion will provide a quantitative basis for detection reliability in ultrasonic infrared imaging.
2016, 45(3): 304006.
doi: 10.3788/IRLA201645.0304006
By using the correlativity between image gray value and temperature, the temperature that is hard to measure can be accurately obtained in some fields. The correlativity analysis between image gray value and temperature was proposed based on infrared target(IT). Self-developing infrared target was taken as a research object, which was a method to collect the infrared images which were taken at different temperatures (60-110℃) by infrared target with circular apertures. Matlab was used to extract the infrared image gray values (IIGV) of certain regions at different temperatures, which could ensure the correlativity between infrared target image gray value(ITIGV) and its temperature. The correlation coefficient of 0.962 was obtained. Experimental results reveal a good linear correlation between the average gray value of area of interest (AOI) in the infrared target images and temperature. With the change of infrared target temperature, infrared image gray values has changed. Both of them show a good linear correlation. The correlativity between image gray value and temperature based on infrared target has an outstanding effect on straw self-ignition in paper mill, medical security, road construction, etc.
2016, 45(3): 304007.
doi: 10.3788/IRLA201645.0304007
The fact that infrared radiation of sea surface is polarized has been proved by many experiments. Searching and detecting ability of infrared polarization imaging systems in sea-surface environment was a major concern for polarization imaging research. Sea surface was realized by using a statistical model of oceanographic literature which originated from the spectrum for long and short wind-driven waves proposed by Eifouhaily. A Monte Carlo reverse ray-tracing method was used to investigate the behavior of mid/long-wave infrared Stokes radiance which included the information of radiance intensity, degree of polarization and angle of polarization, at the realized wind roughed sea surface. The minimum resolvable temperature difference(MRTD) parameters for Stokes-vector components were proposed based on standard error propagation method. Finally, detectable range of infrared polarization imaging used in sea surface environment was analyzed by comparing apparent-temperature differences(ATD) between target and sea background with the MRTD of Stokes-vector components.
2016, 45(3): 304008.
doi: 10.3788/IRLA201645.0304008
The effectiveness evaluation of fighter's infrared countermeasure is the key of operational use of weapon equipment. In allusion to simple infrared environment, fixed operational situation and single component, traditional effectiveness evaluation methods are researched, which can't fully reflect the authenticity and exhaustiveness of infrared countermeasure. So the effectiveness evaluation method of fighter's infrared countermeasure was put forward. The process of infrared countermeasure that was divided into three phases was studied in accordance with actual countermeasure process, such as detecting target phase, occupying phase, and killing target phase. The probability weights of different phases were confirmed based on probability methodology. And an effectiveness evaluation method based on infrared countermeasure whole process was proposed. At last, the success probabilities of accomplishing fighter's infrared countermeasure mission were obtained. Comparisons show that the effectiveness evaluation of infrared countermeasure is valid and correct, which can provide theoretical basis for infrared attacking strategy and infrared defensing strategy.
2016, 45(3): 304009.
doi: 10.3788/IRLA201645.0304009
The interference of marine environment and vessel by decoys cannot be neglected in the complicated marine background. The characteristics of infrared decoys were indicated based on its spatial and temporal distribution characteristics and infrared radiation model. According to the mechanism of radiation energy from decoys and the marine environment, the marine surface scattering model was built based on bidirectional reflectance distribution function(BRDF). A GPU-based parallel computing framework of marine interference scens with infrared decoys was designed, and a 3D real-time simulation of interference of compliected marine scene was performed before and after marine-/aerial-decoys launch. The influence on the imaging by marine-/aerial-decoys established, and the vessel contrast variation with decoys launch angle and observing height were analyzed. The research provides the basis for the study of marine objectives detection algorithms and decoy development.
2016, 45(3): 306001.
doi: 10.3788/IRLA201645.0306001
In order to study the pyrolysis of composites, an experimental investigation of carbon fiber reinforced epoxy resin composites was carried out. The samples, protected by tangential nitrogen flow, were subjected to a lower power density laser. The influence laws of laser irradiation time and power density on the pyrolysis of composites were obtained and discussed. The results reveal that, along with the laser irradiation time increase, the mass loss of samples increases monotonically while the thermal ablation rate of samples decreases gradually and will tend to be steady. On the other hand, the mass loss of samples is proportional to the laser power density. However, the thermal ablation rate increases significantly at first along with the power density increase, and then slowly since it enters into the glacis.
2016, 45(3): 306002.
doi: 10.3788/IRLA201645.0306002
Endurance time of laser powered unmanned aerial vehicle(LPUAV)is prolonged significantly for energy supply. But non-uniform laser spot leads to serious power loss of photovoltaic receiver. Output characteristic models of series and parallel photovoltaic module were derived firstly. Based on the models, output characteristics of photovoltaic module, e.g. I-V and P-V curves, efficiency of photovoltaic cells and module, were analyzed. The relationship between efficiency and non-uniformity of illumination was also studied. The result indicates photovoltaic cell diverges from its maximum power point which leads to efficiency drop of series photovoltaic module. On the contrary, parallel connection with low voltage is less influenced by non-uniform illumination. An experiment was also conducted to study laser wireless power transmission. Output characteristics of series and parallel photovoltaic module were measured and analyzed correspondingly. The feasibility of improving efficiency of photovoltaic receiver by designing a suitable circuitry connection is proved.
2016, 45(3): 306003.
doi: 10.3788/IRLA201645.0306003
Using neutral chromium atoms for the fabrication of nanometer-scale ordered structures is a new method of generating nanostructures on a substrate. But all the information of nano-gratings deposited by laser standing wave field can not be given only through one-dimensional or two-dimensional analysis. Three-dimensional analysis of the effects of atomic beam divergence angle on the process of fabricating nano-grating was discussed based on the three-dimensional motion model of Cr atoms in Gaussian standing wave laser field. The study shows that the preparation of a high-collimated and transversely cooled atomic beam, typically under 0.6 mrad, is essential to minimize the severely disadvantageous effects for deposition of atoms in laser standing wave.
2016, 45(3): 306004.
doi: 10.3788/IRLA201645.0306004
To accurately measure the zero signal of rockets during takeoff, a measurement method was put forward herein combining laser active imaging and range-gated technology, under which the zero signal was obtained by calculating the change in optical flow and then the amount of displacement. Existing zero signal measurement methods were analyzed to determine the range-gated ICCD imaging method, and combined with the feature of the target rising vertically, an anti-light interference algorithm was proposed combining the target contour and HS optical flow. Results show that as the simulated target is rising in uniform velocity, when the light changes little, either edge detection or HS optical flow detection algorithm could detect the upward trend of the target independently; when the light changes drastically, both edge detection and HS optical flow detection algorithm show serious errors, while edge detection combined with HS optical flow algorithm eliminates the interference inside the target, and the target pixel displacement amount obtained is basically consistent with the real ascending amount with the error in sub-pixel. If the image frame frequency is 25 fps, the time accuracy is 80 ms, which is in full compliance with the requirements of zero signal extraction.
2016, 45(3): 306005.
doi: 10.3788/IRLA201645.0306005
Laser beam image generated by atmosphere backscattering has been widely used to monitor the laser pointing in Satellite Laser Ranging(SLR). The phenomenon that the brightness of beam image differs from sky sections influences the satellite aiming. Based on the SLR system of Shanghai Astronomical Observatory, Chinese Academy of Sciences, the mechanism of this phenomenon was figured out that the efficiency of splitter mirror was generally related to the polarization state of incident light. Accordingly, a new method was proposed that a half-wave plate was deployed in transmitting path, and rotating it realized the real-time control of different brightness for beam imaging. The model of outgoing laser polarization direction with the pointing of telescope was established. Compared with the use of splitter mirror whose efficiency is independent of polarization direction, the method is more flexible, simpler and less cost. The method can be applied in improving laser beam pointing accuracy in SLR and Signal-to-Noise Ratio(SNR) of star image etc.
2016, 45(3): 306006.
doi: 10.3788/IRLA201645.0306006
The beam expender of a space-borne laser range finder was an afocal telescope, the alignment requirement of which was rigorous. The alignment accuracy was the key factor of the capability of the laser range finder. The sensitivity of optical element and the compensator were obtained by means of computer aided alignment. High precision coordinate measuring and dual-path centering technology were presented, being aimed at the characteristic of performance parameter determined by distance of elements. Finally the wavefront of the system was tested by the 1 064 nm interferometer, the divergence angle was tested using a pin-hole. The result demonstrates that the RMS of the system is better than 0.225 and the divergence angle is 0.41 mrad. The results meet the requirement of design.
2016, 45(3): 306008.
doi: 10.3788/IRLA201645.0306008
To evaluate the jamming effect effectively, the research on the jamming influence of the laser high repetition which is made by interference factors of interfering frequency, wave door width, encoded mode and jamming moment was carried out. Firstly, three models of wave gate setting, coding identification and high repetition jamming were set up through deeply analyzing the anti-interference key technology and jamming mechanism. Secondly, a scheme was put forward, which was about judging the jamming signal in time gate and simulating the trajectory by the judge. Finally, based on the proportional guidance with over gravity compensation trajectory simulation platform, the effects of different factors on the high frequency jamming were evaluated. The result shows that interference frequency and wave gate width have a greater influence on the jamming effect, and the higher the frequency and the wider the wave gate are, the better the jamming effect is; the anti-interference performance of long cycle code is better than short cycle code; when the interference frequency reaches 100 kHz and wave door width reaches 20 s, two space code can be completely jammed and miss distance can reach 510.4 m; jamming moment has a smaller effect on jamming effect. The results may provide some reference and basis for the development and application of high repetition jamming equipment.
2016, 45(3): 305001.
doi: 10.3788/IRLA201645.0305001
The Nd:YVO4 self-mode-locked picosecond laser was designed and studied, and also the best conditions of the mode-locked lasers were explored. The period-doubling self-mode-locked pulses and the quasi-periodic self-mode-locked pulses in the picosecond laser were observed and analyzed, and the output characteristics of the self-mode-locked laser with straight cavity in compact structure was studied and measured. The resonant cavity was concave flat chamber, under the condition of no other clamping device, the Nd:YVO4 crystal as a laser gain medium and Kerr medium, and the high efficiency continuous mode-locked 1 064 nm laser pulses were outputted. The Nd:YVO4 laser crystal is 16 mm from the input mirror, and the cavity length is 90 mm. The four kinds transmittance in 1 064 nm of output mirror are 10%, 20%, 30% and 50%, respectively, meanwhile the output characteristics of the laser were analyzed in comparison with different output mirrors. By optimizing the design, when the transmittance in 1 064 nm of output mirror is 10%, the output power of the laser is 2.76 W at 8 W incident pump power, and the slope efficiency is up to 43.2%, the repetition rate of mode-locked laser is 1.43 GHz, the laser achieves a high powered and stable continuous wavelength mode-locked.
2016, 45(3): 305002.
doi: 10.3788/IRLA201645.0305002
Mid-IR laser in 3-5 m wavelength region is in the range of atmospheric transmission window, it is in great demand for a variety of applications including molecular spectroscopy, remote sensing for environmental monitoring, industrial process, free space communication, optoelectronic countermeasures. One of the most promising approaches to reach mid-IR spectral range is based on direct lasing of Transition Metal (TM) doped II-VI chalcogenide crystals. Fe2+ ions doped ZnSe laser crystals offer a special blend of physical and spectroscopic parameters that make them the gain media of choice for cost effective broadly tunable lasing in Mid-IR wavelength region. Spectroscopic properties and fabrication methods of Fe:ZnSe crystal were introduced, the development history and technology status of Fe:ZnSe laser were summarized. There are still several challenges to be overcome in the development of affordable room temperature Fe:ZnSe laser including fabrication of high optical quality gain elements and developing high efficient, high energy short pulse pump sources in 3 m wavelength region. The key problems developing high energy, high power Fe:ZnSe laser at room temperature were analyzed.
2016, 45(3): 320001.
doi: 10.3788/IRLA201645.0320001
The study on effect of gamma() ray irradiation on silicon photodiodes for on-orbit calibration was carried out. Silicon photodiodes were irradiated by 20 krad(Si), 35 krad(Si) and 50 krad(Si) gamma doses resepctively. The darkness current and spectral responsivity were measured before and after irradiation. It's found that the darkness current and spectral responsivity have no dramatic change under less than 35 krad(Si) gamma doses. Under 50 krad(Si) gamma doses, the darkness current of the sample increases slightly, but the influence on the application of calibrator can be ignored. The results suggest that silicon photodiode under test can be used as a candidate device for on-orbit calibrator in visible spectral bands due to its good long-term stability and reliability in the space irradiation environment.
2016, 45(3): 320002.
doi: 10.3788/IRLA201645.0320002
At present, SPASER(Surface Plasmon Amplification by Stimulated Emission of Radiation) is the smallest nanoscale active device, which is the first to function under visible light. In this paper, the MIM(metal-insulator-metal) waveguide structure of a double steady state was designed, which introduces the SPASER technology, namely, the surface plasmon wave amplifier. The amplifier was obtained by deriving from the Bloch equation using the SPASER laser theory. When the pumping rate was less than the threshold value, the number of the gain medium inversion particles remained 0. Otherwise, the number of the inversion particle grew linearly. The geometrical characteristics of the system could be completely described by the eigenmode function. On the central eigenmode, the system property entirely depended on the material parameters. Choosing the appropriate material parameters could make each state of the relaxation characteristic time remain at the level of the picosecond magnitude. The calculated results of the model show that the improved structure does not change the strong localized characteristics of the SPPs(Surface Plasmon Polaritons). The device solves the limitation on the surface plasmon net profit elimination caused by SPASER internal feedback.
2016, 45(3): 320003.
doi: 10.3788/IRLA201645.0320003
A nanostructure of broadband surface plasmons logic AND gate was presented. The two input ports were composed of broadband infrared directional couplers which were a pair of two parallel slot nano-antennas milled into gold film. An array of couplers arranged on an arc-shaped circle was capable of focusing the surface plasmons to the circular center when it was illuminated with radially polarized beam. The same two focused surface plasmons spots were coupled into two groove-shaped waveguides, respectively, and then interfered each other at the cross point. The intensity was four times that of intensity produced by a single arc-shaped nanostructure when two arc-shaped nanostructures produced the surface plasmons in the center with the same amplitude, polarization direction and zero phase difference. The nanostructure and device principle were theoretically analyzed. The relation between input ports and output port along with broadband property were simulated with the finite difference in time domain method.
2016, 45(3): 313001.
doi: 10.3788/IRLA201645.0313001
International completed optical/infrared telescopes were reviewed, and the construction of the next generation of telescopes was analyzed, including scientific purposes, optical structure, carry instruments, performance parameters and so on. This paper was focused on the summarization of optical design/diameter and site/orbit of next generation astronomical telescope. Their collaboration observation of ground-based/space-based, modular universal design, observation result big data sharing etc shows the technical characteristics and trend. Combining lessons from abroad with the reality of our country, our own advantages can be formed. Some thoughts and suggestions on long-term planning, private capital opening and others were put forward.
2016, 45(3): 313002.
doi: 10.3788/IRLA201645.0313002
In order to ensure the surface form precision of a mirror whose caliber is 320 mm changes as small as possible before and after bonding, while static and dynamic stiffness of the mirror components meet the requirements, bonding technique of primary mirror in space camera was studied. Firstly, specific bonding parameters of six bonds and round bonds were achieved. Then, the finite element analysis for two bonding options was carried out to analyze static stiffness and optical properties. Finally, when the mirror's surface form precision was 0.030(=632.8), the surface form precision of the mirror was tested. Besides, vibration test of mirror components was conducted. Analysis and experiment results indicate that after using six bonds option to assemble the mirror components, its first order frequency is 144.194 Hz and static and dynamic stiffness meet the requirements. Compared to round bonds option, the surface form precision of the mirror improves 13.5%. This results mean that the six bonds option is better for bonding the mirror whose caliber is near 320 mm.
2016, 45(3): 318001.
doi: 10.3788/IRLA201645.0318001
R-C optical system was a commonly used optical system in modern optical engineering, a case study of alignment technique of R-C optical system was stuided. The alignment theory of R-C optical system was analyzed. The main mirror was the adjustment datum, the five degree of freedom of secondary mirror was adjusted to improve the wavefront error of the whole optical system. The relationship between secondary mirror misalignment and Zernike coefficient of the whole system was obtained by computer-aided alignment and was used to guide alignment of secondary mirror. By use of this method, the alignment purpose was very clearly, that was adjusting the position of secondary mirror to reduce Zernike coefficient. The alignment period was then reduced. After alignment, wavefront error of the whole optical system was better than 1/10(RMS). It satisfies the design requirement. The images obtained from laboratory and outfield indicate the alignment is valid.
2016, 45(3): 318002.
doi: 10.3788/IRLA201645.0318002
Dynamic modeling of an input-output coupled piezoelectric fast steering mirror(FSM) was discussed, especially in case that the sampling frequency of the sensor is so high (e.g., high-speed camera or position sensitive device is used) that the dynamics of the FSM is significant and can't be neglected. The dynamics and input-output coupling in the FSM was analyzed. A method was proposed to model the dynamics and input-output coupling in the FSM, based on the input-output data and the subspace identification algorithm. Experiments were carried out for data collection and validation of the proposed method. The results show that the variance-account-for(VAF) of the dynamic input-output coupled model is as high as 95%, indicating high accuracy of the model. Comparison was made between the proposed model and static model as well, showing significant improvement on the model accuracy. The result can be applied in optimal feedback controller design for closed-loop FSM systems, to improve the closed-loop performance in laser beam drifting correction.
2016, 45(3): 321001.
doi: 10.3788/IRLA201645.0321001
Cobalt ferromagnet/carbon and nickel cobalt copper ferromagnet/carbon nano composite were prepared. Infrared and ultraviolet-visible spectra were tested in range of 2.5-25 m and 200-800 nm, while the extinction coefficients were calculated by using Lambert-Beer law. The extinction coefficients of cobalt ferromagnet/carbon composite, especially nickel cobalt copper ferromagnet/carbon composite increased after calcination. Nickel cobalt copper ferromagnet/carbon composite attained at 0.36 m2g-1 and exceeded 0.15 m2g-1 in the range of 3-16 m. When the ratio of Nickel cobalt copper ferromagnet/carbon composite to acetylene black is 5:1, the extinction coefficient of the mixture reached 1.25 m2g-1 and exceeded 0.90 m2g-1 in the range of 3-5 m and 8-14 m. For ultraviolet-visible band, both cobalt ferromagnet/carbon composite and nickel cobalt copper ferromagnet/carbon composite exhibited show excellent extinction property. The different of main mechanism between infrared and ultraviolet-visible range were discussed. The reflectivity curves were test by adopting Arch Method in the range of 2-18 GHz. Mixing ferromagnet/carbon composite, the reflectivity curve of FeNi/carbon fiber moved to lower frequencies, as well as the absorbing bandwidth broadened.
2016, 45(3): 330001.
doi: 10.3788/IRLA201645.0330001
A new mobile lidar system with day and night capability has been developed for the application research of test engineering and environmental monitoring. The lidar system was composed of a horizontal measurement module and vertical measurement module, which can receive the Mie scattering and Raman scattering signal that come from the action of laser and aerosol particles, water vapor molecule, nitrogen in atmosphere. Atmospheric horizontal visibility, vertical aerosol extinction coefficient and water vapor mixing ratio can be retrieved. The lidar system can provide continuous observation day and night, the actual measurement results and comparison experiments show that the measurement error of atmospheric horizontal visibility is less than 10%, and the error of the vertical aerosol is below 10% under the height of 6 km, and the maximum error of water vapor is not exceeding 20%. The mobile lidar system can be provided to meet the various application requirements for atmospheric parameters measurement.
2016, 45(3): 331001.
doi: 10.3788/IRLA201645.0331001
The remote sensing investigation ability of a mobile platform is promoted by setting a fast steering mirror which to reduce the servo error of inertially stabilized loop in the access of optical detection, then the platform's pointing precision, track velocity and stabilized accuracy of line-of-sight will be improved effectively. A inertially stabilized gimbal and fast steering mirror were transformed into a parallel Dual-Input Single-Output(DISO) system. Based on the difference of actuator range and frequency between inertially stabilized gimbal and fast steering mirror, a combined control method was presented, which was used to assure the auxiliary pointing stability, and then the pointing precision and track velocity can be improved through this method. A simulation experiment was carried out to verify the effectiveness of the method which reduce the servo error of inertially stabilized platform from 0.018 to under 0.005 by putting in a fast steering mirror.
2016, 45(3): 323001.
doi: 10.3788/IRLA201645.0323001
Cryogenic imaging spectrometer with wide spectrum and high resolution can be used to detect interplanetary mineral component and atmospheric composition. Due to the temperature of detected target in space exploration is very low, the infrared spectra in imaging spectrometer has to work in cryogenic environment to limit the noise from the imaging spectrometer itself to promote its spectral resolution. That is a challenge for the design of cooling system. Based on survey results about the cooling system of VIRTIS for Venus and Comet, the cooling system for cryogenic imaging spectrometer with wide spectrum and high resolution was designed and simulated. The simulation results show the temperature gradient of M and H detector is only 410-2 K. Detector temperature is less than 70 K. The shell temperature is 1301 K and frame temperature is 2001 K. All the results demonstrate the designed cooling system meets the design requirements. The results are significant for cooling system design in cryogenic imaging spectrometer, which is used widely in space exploration.
2016, 45(3): 323002.
doi: 10.3788/IRLA201645.0323002
The spectral response measurement of space infrared camera with large aperture was introduced. The measure system had been developed, which included visible and infrared light source, monochromator, standard detectors, data acquisition system, parallel light tube, vacuum tank, turntable and the test camera. The bands of test camera were concentrated in water vapor, CO2 absorption bands. In order to eliminate the impact of atmospheric absorption bands, parallel light tubes, test camera, turntable should be placed under vacuum condition, and the monochromator should be purged with nitrogen. The results show that, after purged with nitrogen, the spectrum precision is greatly improved and the spectrum at atmospheric absorption bands can be accurately measured.
2016, 45(3): 323003.
doi: 10.3788/IRLA201645.0323003
The efficient onboard lossless compression is very important for the real-time transmission of hyperspectral images. Due to the shortages of the traditional joint encoding and decoding algorithms of hyperspectral images, a lossless compression algorithm based on distributed source coding (DSC) was proposed. To make use of the local spatial correlation, multiple linear regression was employed to construct the side information of each block, and the optimal predictive order was determined for each block in order to make full use of the local spectral correlation. According to the principle of (n, k) linear grouping codes, distributed lossless coding of hyperspectral images was realized by using multilevel coset codes. Experimental results show that the proposed algorithm achieved competitive compression performance and low complexity compared with those existing classical algorithms, which is suitable for the onboard compression of hyperspectral images.
2016, 45(3): 317001.
doi: 10.3788/IRLA201645.0317001
In order to acquire the original wavefront information in radial shearing interferometry, wavefront reconstruction is necessary, the iterative algorism for wavefront reconstruction was deduced in this paper, based on which an numerical simulation using Matlab with different iteration number and shearing ratio was conducted. The simulation comes to the following conclusion: Properly selection of the shearing ratio can simplify the computational complexity. Compared with the small distortion wavefront reconstruction, more but appropriate iteration number in large distortion wavefront reconstruction is needed. Preferred shearing ratios for different measured wavefront PV values are summarized as follows: a. if WPV 10, beta 0.7; b. if 6 WPV 10, 0.5 beta 0.7; c. if WPV 6, beta 0.5.
2016, 45(3): 317002.
doi: 10.3788/IRLA201645.0317002
The three-dimensional small angle measurement system based on Fresnel biprism was an improved autocollimation method which replaced the single mirror by two mirrors with a certain angle. It measured the space angle change through solving the mathematical relationship between the reflected spot displacement and the mirror rotation angle. The traditional modeling method always predetermined a rotation order to indirectly establish the mathematical relationship between the state of the object space angle change and the rotation angle, which had not one result for the predetermined rotation order was random. A new modeling method was proposed which directly established the mathematical relationship between the initial object state and the final state after rotation, which didn't need to predetermine a rotation order making one rotation state having only one mathematical relationship. This method was objective, direct and could be used to measure bigger range of three-dimensional angle. Finally, the correctness of this modeling method by using simulation calculation was verified.
2016, 45(3): 317003.
doi: 10.3788/IRLA201645.0317003
A digital test system was presented, used to measure the angle of shot gun bore axis deviates from exit surface. Based on the principle of laser tracker space coordinates measurement, by measuring the 3D coordinates of the gun barrel, the system accounts for the linear equation of space before and after the adjustment of gun, thus the deviation angle of the gun was calculated, and the problems of low precision, low efficiency, too much staff and structure dispersion were analyzed in the measurement method of gun bore axis deviation angle from the exit surface in view of the current GJB method. Comparing the experimental measurements with the current GJB method, the experimental data show that by using this method to measure the deviation angle of the gun, the efficiency and accuracy are improved obviously.
2016, 45(3): 317004.
doi: 10.3788/IRLA201645.0317004
Cryogenic radiometer currently is used as the supreme standard for the measurement of light power, whose accuracy evaluation can be acquired through the results between different cryogenic radiometer equipment. With trap detector serving the transfer standard and the calibration optical path in cryogenic radiometer being distinct, a comparison experiment was carried out between two equipments for the first time in China. The absolute spectral responsivity of transfer standard was calibrated at 633 nm wavelength. The results show that the consistence of absolute spectral responsivity is 3.610-3 and the combined uncertainty is 3.310-4(k=1). It is proved that the two cryogenic radiometer equipments are of high reliability and accuracy.
To evaluate inhibitory effect of diversity transceiver technology on the atmospheric turbulence in the application of offshore laser communication system, experiment verification scheme of multi-channel synchronous acquisition of laser spot based on 1 550 nm was designed. Extraction of target center position and target gray statistical of real time image processing system were realized by using terminal triggered with the FPGA+ multi-core DSP architecture, and then the arrival angle fluctuation variance and the scintillation index from the laser transmitting terminal to the receiving terminal were obtained. Under the conditions of equal power, arrival angle fluctuation variance and the scintillation index were compared between single way transmitting and double way transmitting, double aperture receiving and equivalent single aperture, and the effect of double aperture receiving was compared under different spans. Experimental results show that the same transmitting power, the arrival angle fluctuation variance and the scintillation index are effectively inhibited caused by atmospheric turbulence with dual way transmitting compared with single way transmitting; in condition of same reception area, the arrival angle fluctuation variance and scintillation index is more weak through single aperture receiving compared with double aperture receiving. In a certain range, double size span exists optimal values.
2016, 45(3): 322002.
doi: 10.3788/IRLA201645.0322002
In order to address the problem that disturbance compensation effect of traditional active disturbance rejection controller(ADRC) decreased rapidly with the increase of disturbance frequency, a new ADRC method based on modified linear extended state observer(ESO) was proposed in this paper. Firstly, the coarse tracking system was analyzed, simplified and identified, and then the disturbance observation theory of ESO was derived and demonstrated, and its disadvantages were pointed out theoretically. According to that, an improved linear ESO was proposed and its advantages were illustrated by theory and simulations. Finally, the ADRC of coarse tracking system was realized with the improved linear ESO and PID adjuster. The experimental results show that as for the external position disturbance with the magnitude of 1 and frequency of 0.5-2.5 Hz, the disturbance isolation degree declines significantly with the increase of disturbance frequency adopting the traditional ADRC. While the disturbance isolation degree improves at least 4.416 dB adopting the improved ADRC in this paper, and the disturbance isolation degree increases stably with the increase of disturbance frequency, which is almost the same at 2.5 Hz and 0.5 Hz. What's more, the proposed method is robust and the change within 20% of the controlled object is allowed. In conclusion, theoretical analysis, simulation analysis and the physics experiment prove this method is effective, and it has some reference value for similar photoelectric tracking system.
2016, 45(3): 322003.
doi: 10.3788/IRLA201645.0322003
Accurate threshold is the key factor for reducing both of missing and nuisance alarm rates, which is essential for the -OTDR distributed fiber-optic sensing system. In order to solve this problem effectively, the algorithm based on the selective average was proposed. During this proposed algorithm, a pre-selection scheme was achieved using the correlation difference method to determine a signal template. Then, the match of threshold template can be realized. Theoretical and experimental results show that by the proposed algorithm the threshold can be obtained to decrease the missing and nuisance alarm rates, and improve the signal-to-noise ratio(SNR) of the -OTDR distributed fiber optic sensing system. In comparison with current direct and moving average algorithm, the missing alarm rate is decreased by 2%, and the nuisance alarm rate is decreased by 5% and 3%. What's more, the SNR is increased by 2.55 dB and 1.1 dB, respectively. In conclusion, the proposed algorithm was also useful to improve the real-time reliability of the system for the practical applications.
2016, 45(3): 322004.
doi: 10.3788/IRLA201645.0322004
During the spacecraft's in-orbit running, its structure could get a micro angular vibration due to various moving parts inside, which has relatively small amplitude and high frequency and could result in quality reduction of the optical load's imaging. With broad bandwidth and high sensitivity, the FOG can output angular increment in a sample cycle, making it the perfect sensor of micro angular vibration. But FOG can't be sampled evenly considering the spacecraft's whole scheduling. This paper proposes a frequency spectrum analysis method for nonuniform sampling, which transforms time sequence in a complete nonuniform sampling cycle to the fourier space to obtain original signal's amplitude and frequency so as to achieve high precision measurement of the micro angular vibration. The method has a precision better than 0.04, which was validated by digital simulation and 6-DOF micro vibration test.
The imaging characteristic of background in elliptical orbit infrared platform is the basis of infrared image data processing. Firstly, the geometric projection model and signal transfer model of elliptical orbit infrared platform were established, and the imaging model of infrared sensor was given. Secondly, the effect of platform attitude, relative movement of background ontology and orbit on imaging characteristic of background were analyzed and the mathematical influence model was deducted. Finally, simulation experiments verified the correctness of the model, and the synthetic simulation results of imaging characteristics of background were given. The analysis results show that new features of background are presented in the detect image of infrared surveillance platform running on the elliptical orbit, and new requirements for infrared imaging data process are requested.
2016, 45(3): 326002.
doi: 10.3788/IRLA201645.0326002
The defect of the existing imaging registration algorithms which are applied in remote sensing image assembling and registration was analyzed. According to the imaging characteristic of interleaving assembly for space camera, a registration model based on homologous points tracking for assembly imaging was proposed. The collinearity equation of perspective projection under assistant space coordinate was established. Then, the strict mathematical realationship of image point, camera imaging center and ground point was established. The locus of homologous points at image plane could be tracked accurately. Combined with the restrict of TDICCD on image plane, the number of pixels in direction of longitudinal and transverse displacement of pair of homologous points was calculated. Finally, according to the analysis based on image bands camera imaging on the track and satellite assistant datas, multiple of image points were selected to be registrated. The error of homologous points registration was less than 1 pixel. The feasibility of registration algorithms was proved. Compared with traditional registration algorithms for remote sensing image, this method is a strict registration with meaning of geometry, and there is no need to know the content of image. The method applied to the checking and calculating on correlative camera, has better adaptability and predictability. The model is easy to be applied to the imaging registration and assembling for others kinds of space camera.
