2016 Vol. 45, No. 9
column
- Invited paper
- Optical data storage technology
- Outstanding doctoral dissertation in optical engineering
- Infrared technology and application
- Laser technology and application
- Photoelectric measurement
- Optical design and simulation
- Micro-nano optics
- Photoelectric devices and microsystem
- Advanced optical material
- Terahertz technology and application
- Optical communication and optical sensing
- Scene information processing
2016, 45(9): 902001.
doi: 10.3788/IRLA201645.0902001
In the application of space target detection, due to the characteristics of small target and great distance, the returned signal is very weak, even a few of photons or less than a photon per pulse. Such weak signal can't be detected by traditional laser radar. Moreover, the space target detection now not only needs the range information, but hopes to get the intensity, polarization and more multi-dimensional information. Therefore, high sensitivity photon polarization laser radar system was proposed based on the four-way Gm-APD single photon detector. The intensity formula of weak signal was deduced from the Poisson probability model of Gm-APD detector. Then, the polarization information of the returned signal was obtained through four-way intensity results. Finally, the principle prototype of four-way Gm-APD photon polarization laser radar system was established in the laboratory, and the relevant experiment was conducted. When the average energy of returned signal per pulse is 7.7810-19 J, the experimental results show the linear polarization error of 3.95% and the elliptical polarization error of 5.84%.
2016, 45(9): 902002.
doi: 10.3788/IRLA201645.0902002
Ideally, to achieve optimal production in agriculture, crop stress needs to be measured in real-time, and plant inputs managed in response. However, many important physiological responses like photosynthesis are difficult to measure, and current trade-offs between cost, robustness, and spatial measurement capacity of available plant sensors may prevent practical in-field application of most current sensing techniques. This paper investigates a novel application of laser speckle imaging of a plant leaf as a sensor with an aim, ultimately, to detect indicators of crop stress:changes to the dynamic properties of leaf topography on the scale of the wavelength of laser light. In our previous published work, an initial prototype of the laser speckle acquisition system specific for plant status measurements together with data processing algorithms were developed. In this paper, we report a new area based statistical method that improves robustness of the data processing against disturbances from various sources. Water and light responses of the laser speckle measurements from cabbage leaves taken by the developed apparatus are exhibited via growth chamber experiments. Experimental evidence indicates that the properties of the laser speckle patterns from a leaf are closely related to the physiological status of the leaf. This technology has the potential to be robust, cost effective, and relatively inexpensive to scale.
2016, 45(9): 935001.
doi: 10.3788/IRLA201645.0935001
The history and status quo of optical data storage was reviewed in this paper. In big data era, the usage and meaningfulness of optical disc was discussed. Because of the low capacity and slow rate of optical disc, the effective technique solution of Optical Library was introduced. In the last the holographic data storage technologies as the next generation of optical disc were described. Collinear Holography is one of the technologies which can be compatible with existing disc storage systems, like CD and DVD, and enable us to store the Big Data with its high density, high data rate and long life time.
2016, 45(9): 935002.
doi: 10.3788/IRLA201645.0935002
A system concept called ORAID(Optical Replicated Arrays of Independent Disks) was presented in which the hard disks and optical media were converged into high performance WORM(Write Once Read Many) appliances in a way so that no additional tier was added to the existing storage system architecture. An ORAID product typically includes a full-range of non-redundant hard disk array on the front end and an optical library in the background where the optical library is hidden and therefore invisible to the user interface. The hard disk array can be formed as a NAS(Network Attached Storage) merged together with a database-driven hidden library. The user can access their file systems as usual with all the ease and comfort without additional integration efforts. ORAID effectively uses the lifetime of each individual hard disk in the array so the data migration overhead and the data loss risk can be significantly reduced. Unlike the conventional redundant technologies like RAID(Redundant Arrays of Independent Disks) or erasure coding where the number of defective disks allowed is limited, there is no correlation between the hard disks, and data on an ORAID system will never be lost no matter how many HDDs (Hard Disk Drives) are defect. Because of its physical nature the WORM/compliance will be ensured for optical media and this feature can also be realized for the hard disk front end by using HASH coding. In case of disk failure or any HDD absence the related data on the optical media will be automatically activated so that the data availability will be guaranteed when hard disks are somehow not accessible, e.g. during the hard disk rebuild process or replacement work. In an ORAID system, data on HDD and optical media is mutually protected. A health check process is keeping the integrity and safeguards against media failure. ORAID implements an integrated hybrid media storage in which the explicit backup process can also be eliminated. The logical consequence of greatly reduced workload for the optical drives and robotics will lead to less maintenance overhead on the library side and significant improvement of the working lifetime of the optical drives.
2016, 45(9): 935003.
doi: 10.3788/IRLA201645.0935003
More and more digital information needs long term preservation, a cost-efficient storage system is needed to ensure long term data availability. Using tape and hard disk as storage medium can not meet the demands of long-term data preservation. Current blu-ray inorganic disc is able to store data more than 50 years, the fact that the drive and optical disc is separate makes it easy for optical disc to be stored. Optical disc is proved to be a choice for long term preservation. But the capacity of optical disc is too small compared to tape and hard disk, which limits its use in archival storage system. A novel large-scale Automation optical library system is introduced, a standard rack contains more than 10 000 discs, provides 1 GB/s throughput. The fundamental thought is tiered storage with HDD, SSD and optical disc and storage virtualization. HDD and SSD works as cache for optical storage level, thus improve performance; all the optical discs are set to a virtual volume pool. Optical library system implements automatic mechanical dispatch, file access and disc recording by the integration design controll and inner data structure. A common file system interface is provided to users. Experiments result shows that the system can automatically read and record files.
2016, 45(9): 935004.
doi: 10.3788/IRLA201645.0935004
Polychromatic reconstruction(PCR) is a novel nondestructive readout method that utilizes a spectrally broad light source for the probe beam. The stored image can be completely reconstructed even though the probe wavelength is very different from the recording one. The large spectral width of the polychromatic probe beam also causes adverse effect on the storage density. But this can be overcomed if an additional optical component is inserted in the imaging system. Therefore, PCR has a great potential to achieve nondestructive readout and large storage density simultaneously. In addition, PCR enables us to design a simple memory system because its readout tolerance is quite large as compared to the conventional monochromatic readout. Unique and attractive features of the polychromatic reconstruction method was theoretically and experimentally demonstrated.
2016, 45(9): 935005.
doi: 10.3788/IRLA201645.0935005
This review presents a reflection-type holographic memory using three-dimensional(3D) speckle-shift multiplexing. First, the schematic of the proposed memory system was described. Then, experimental demonstrations of multiplexing in plane and along the depth direction were presented. The estimated storage capacity of single layer recording was introduced and the maximum storage capacity was discussed. To increase the storage capacity, the multi-layered recording was described. In the multi-layered recording, the storage capacity can be increased by appropriate arrangement of holograms in each layer.
2016, 45(9): 935006.
doi: 10.3788/IRLA201645.0935006
Collinear Holography was proposed by OPTWARE Corporation, in which the information and reference beams were aligned co-axially and modulated by the same SLM. With this unique configuration the optical pickup can be designed as small as the DVD's, and can be placed on one side of the recording disc. A 2-dimensional digital page data format was used and the shift-multiplexing method was employed to increased recording density of HVD. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disc in the recording and the reconstructing process, a vibration isolator is no longer necessary. In HVD, the pre-formatted meta-data reflective layer was used for the focus/tracking servo and reading address information, and the dichroic mirror layer was used for detecting holographic recording information without interfering with the preformatted information. Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. HVD will be compatible with existing disc storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems.
2016, 45(9): 934001.
doi: 10.3788/IRLA201645.0934001
A first-order Polarization Mode Dispersion(PMD) monitoring technique for phase-modulated optical signals was proposed utilizing the cross-phase modulation(XPM) effect between the input signal and the inserted continuous-wave probe in parallel connection. Because of accumulation of PMD, the XPM effect in nonlinear fiber leads to variation of pump phase. This can cause spectrum broadening resulting in variation of pump power. The technique can suppress the influence of PMD in one branch of the two signals in parallel connection. Then the difference of the two pump power at the same band was used to monitor PMD. The simulation shows that the technique can monitor PMD of 40-Gb/s non-return-to-zero differential quadrature phase-shift keying (NRZ-DQPSK) from 0-30 ps. The dynamic range over 3 dB can be used in accurate monitoring compared to existing methods. Study of the effect of signal rate, CD, pump power and filter bandwidth on the new technique was conducted in detail.
2016, 45(9): 904001.
doi: 10.3788/IRLA201645.0904001
LW HgCdTe thin films were passivated by CdTe/ZnS composite passivation layer, and the growth process of passivation films was improved. The MIS devices and photodiodes were fabricated by using different passivation process. The SEM, C-V and I-V measurement were used to analyze the interface characteristics and its effect on the performance of devices. The results show that the CdTe film grown by improved process is more compact and has no large hole, the lattice structure order degree of CdTe/HgCdTe interface is improved; The C-V curve of MIS device fabricated by improved passivation process reveals high frequency characteristics, and interface fixed charge layers density is decreased from 1.671011 cm-2 to 5.691010 cm-2. The photodiode with general process has large surface channel leakage current under high reverse bias voltage, whereas the surface leakage current of the device with new process is effectively suppressed.
2016, 45(9): 904002.
doi: 10.3788/IRLA201645.0904002
In order to effectively control the temperature of infrared detectors on carbon dioxide under complex heat flux, detailed thermal design was presented. According to the analysis of heat flux around the infrared detectors, positions of heat dissipation surfaces were confirmed. Based on the space thermal environment and the characteristics of complex heat flux, high power consumption and low thermal control index, the thermal solutions of infrared detectors were proposed. The thermal analytic calculation of the finite element model was carried out, and the temperature range of the infrared detectors was -31.8℃ to -26.9℃ in different postures of angle, the results met the design requirements. A thermal balance test of carbon dioxide was actualized to verify the thermal design, the temperature of the infrared detectors was from -32.6℃ to -30.1℃. These results conform with the calculated ones and meet the thermal controlling requirements, the thermal design is reasonable and adaptable in complex heat flux.
2016, 45(9): 904003.
doi: 10.3788/IRLA201645.0904003
The long-wave infrared detectors present the characteristics of large dark current, high background, large charge capacity readout circuit was need to design. A designing scheme of a high readout efficiency and large charge capacity readout circuit for 320256 LW infrared focal plane arrays(IRFPAs) in the finite cell area of FPAs was proposed by adopting the circuit structure of time-shared the integrating capacitor. The input stage circuit used the capacitor feedback transimpedance amplifier (CTIA) preamplifier structure, which has a high injection efficiency, low noise and good linearity. The simulation and the simulation after completing the layout were carried out based on CSMC 0.35 m standard CMOS process model, the output swings of circuit were larger than 2 V and the nonlinearity is less than 1%, the frame rate is 100 f/s, after adopting the circuit structure of the time-shared integrating capacitor, the effective charge capacity reached 57.5 Me-/pixel.
2016, 45(9): 904004.
doi: 10.3788/IRLA201645.0904004
High temperature exhaust plumes of warship power system is an important source of infrared radiation. In this paper, the flow field of ship exhaust plumes was calculated based on CFD methods. Then, a calculation method of high temperature exhaust plume's infrared radiation was obtained by utilizing the C-G approximation method laced on a narrow-band model. Based on this model, the influence of the combined speed on the flow field and the infrared radiation of ship exhaust plumes were analyzed. According to the simulated result, the combined speed has an obvious influence on the shape and distributing area of the exhaust plumes. In addition, when the combined speed increased, the average radiation intensity of ship exhaust plumes decreased about 48.1 percent in the mid-wavelength infrared range. The physical factors for the error of the simulation model are discussed preliminarily.The carbon particles caused by the incomplete combustion have a significant impact on the plumes' infrared radiation transmission.
2016, 45(9): 904005.
doi: 10.3788/IRLA201645.0904005
IR guidance weapons, especially IR imaging guidance weapons, has brought great threat to modern aircraft. Airborne surface-type IR decoy is an effective countermeasure to jamming IR imaging guidance weapons. By analyzing the principle and disadvantage of IR imaging guidance, the jamming mechanism and efficiency index of airborne surface-type IR decoy were researched. The active weapons of airborne surface-type IR decoys was summarized. The recent research and manufacturing technology of airborne surface-type IR decoys, including pyrophoric foil IR decoy and pyrophoric liquid IR decoy, were also introduced. The present research condition of IR decoys' jamming effectiveness was summarized in the respects of experimental research, simulation research, simulated images, jamming strategy and so on. Finally, a simulation project on the jamming effectiveness of the IR decoy based on exploratory analysis was brought out, which can give the jamming strategy with the integration of the different elements.
2016, 45(9): 906001.
doi: 10.3788/IRLA201645.0906001
The polarization lidar returns exist a depolarization signal due to the occurrence of multiple scattering when detecting the microphysics characteristics of liquid water clouds by using lidar. The depolarization information can be used to quantitatively retrieve the clouds characteristics. The semi-analytic Monte Carlo simulation was used to study the backscattering depolarization ratio of polarization lidar with the wavelength of 0.532 m to the height of clouds base, size of the clouds droplets and the extinction coefficient. From the results, if the receiving angle of field remains constant, the depolarization ratio increases with the increase of the distance between the lidar and the clouds and the increase of the extinction coefficients. The impacts of multiple scattering increase with the increase of the receiver field of view angles, so a bigger receiver field of the angle will generate a bigger depolarization ratio. The depolarization ratio is bigger for the clouds with a smaller clouds droplets when the penetration depth is small, but it will be bigger for the clouds with a bigger clouds droplets when the penetration depth is more deeply.
2016, 45(9): 906002.
doi: 10.3788/IRLA201645.0906002
In order to make the lidar images of space target indicating its active state in orbit as real as possible, combined with the information of the detector parameters in orbit, a lidar imaging simulation method for complex space target was proposed in this article. A visibility algorithm based on the area method was presented. Firstly, the method which was used to simulate the lidar imaging was explained in detail. Then, the method was used to simulate the lidar imaging of a simple cube cabin. The emulation results show that the method was feasible to simulate the lidar imaging of the space target, which has significance for the researches of target detection, recognition and tracking techniques.
2016, 45(9): 906003.
doi: 10.3788/IRLA201645.0906003
Based on the Poisson probability model of Gm-APD, in the long dead-time case, a new approach to improve the detection performances of Gm-APD lidar was proposed. The formulas of detection performances(detection probability, false alarm probability, and range error) of multiple pulses detection Gm-APD lidar were obtained and analyzed. By using an attenuator to control the intensity of signal and noise, the detection and false alarm probabilities, and range error of multiple pulses detection Gm-APD lidar were all improved. With the change of transmissivity of attenuator, the detection probability has a maximum, and the range error has a minimum. While the target is at the distance of 1.5 km, with the increase of the pulse number and the controlled transmissivity of attenuator between 0.33 and 0.20, the detection probability can be doubled with the sharp decline in false alarm probability, and the range error can be decreased from meters to centimeters.
2016, 45(9): 906004.
doi: 10.3788/IRLA201645.0906004
Direct detection Doppler wind lidar based on Fabry-Perot etalon is an effective detection means of middle-upper atmospheric wind field. The long-term stabilization of system is basic requirement to perform a task. Firstly, the invalid detection data of DWL was analyzed, the relative drift of laser frequency was the main factor of invalid data. Then, the experiment was set up. To verify the mechanism of seed laser environment temperature changes and the environment temperature changes of locking etalon and the transmission of locking etalon, the result was obtained, which 1℃ temperature change of seed laser environment in Nd:YAG laser systems would cause the change of etalon transmission up to 46.1% and it was equivalent to 1.536 GHz frequency drift of laser, 1℃ temperature change of etalon environment would cause about 737.7 MHz relative drift of laser frequency. To ensure the precision less than 1 m/s resulted from system error, the method of three-step temperature control would be established. The operating room's temperature of DWL would be controlled with precision of 1℃ in the first, and then, the seed laser and the etalon would be placed in the constant temperature box with temperature control precision of 0.001℃, respectively, and the accuracy of wind field detection would be achieved.
2016, 45(9): 906005.
doi: 10.3788/IRLA201645.0906005
Range estimation technology, which plays a decisive role on the properties of the laser radar system, is always the core technology of laser radar technology. A range estimation technology based on Artificial Neural Network which contains two layers of network was proposed. The contrast experiment with the Cross-correlation range estimation technology demonstrates this technology can provide more accurate range estimation result. A simulation experiment on intensity image was conducted, and experiment result show this technology can provide more accurate intensity data than the peak judgment technology. The correlation between the neuron amount of hidden layer and range estimation accuracy was also analyzed, and the result shows too many or too few neurons will decrease the range estimation accuracy.
2016, 45(9): 906006.
doi: 10.3788/IRLA201645.0906006
The Fabry-Perot(F-P) etalon was commonly used in direct detection Doppler wind lidar. As a considerable affect would be caused by laser frequency drift in transmittance curve estimation, a new transmission curve fitting algorithm based on spectrum estimation was presented. Firstly, the scan result of F-P etalon was reconstructed into observation matrix. The pseudo-spectrum by MISIC algorithm was conducted. Then spectrum peak was searched and the FSR by linear least squares estimation method was calculated. Secondly, the else parameters by nonlinear least square estimation method was estimated with the estimation above. The performance of the proposed method was analyzed by simulation and verified through the real data, the results show that the proposed algorithm is more stable and accurate under limited amount of data. The relative error is less than 1% when SNR is 10 dB and sample interval is 50 step. This method has lower sweep time, less error and realty utility value.
2016, 45(9): 906007.
doi: 10.3788/IRLA201645.0906007
In order to solve the problems of huge volume backscattering signal data and time-consuming calculations when retrieving wind velocity in high repetition frequency coherent lidar, a parallel retrieval algorithm based on multicore Digital Signal Processor(DSP) was proposed. In this algorithm, a high performance DSPC-8681 card integrating four Texas Instruments(TI) TMS320C6678 processor with eight cores in each processor was employed. The digital data from Analog-to-Digital Convertor(ADC) was allocated equally to each core in each processor and processed in Single Instruction Multiply Data(SIMD) way. The wind velocity was retrieved by maximum likelihood discrete spectrum peak estimation. On the condition of 10 000 pulses accumulation, the time resolution of 1 s was realized. The performances of the developed coherent wind lidar are demonstrated by experiments, which are listed as follow:detection range in line of sight is 3 600 m; range resolution is 60 m; velocity range is 30 m/s; time resolution is 1 s; velocity accuracy by rotating hard target is better than 0.48 m/s.
2016, 45(9): 906008.
doi: 10.3788/IRLA201645.0906008
Coherent beam combination technology is a significant approach for achieving high power laser beam with good beam quality. Based on mutual injection and evanescent wave characteristics of corner-cube resonator, it reveals that far field output of corner-cube laser was the inner reason and mechanism of coherent combining distribution by theory of evanescent wave. Evanescent wave coupling phase-locked combining characteristic in solid state laser was studied emphatically. The results indicate that the phase locking output is influenced by the distribution of laser beams and some other factors. When the distribution of laser beams is same, the cavity length and duty ratio determine the phase locking result. The longer cavity length and larger duty ratio, the stronger evanescent wave coupling is, so the phase locking result is much better, running to an in-phase mode output. Theories and experiments indicate that corner cube is a natural coherent combination element, and coherent beam combination technology by corner cube has important scientific value.
2016, 45(9): 917001.
doi: 10.3788/IRLA201645.0917001
The measure method of Solar Irradiance Absolute Radiometers(SIARs) is investigated and revised in order to extend the dynamic measurement range and improve the measure uncertainty of lower laser power. The sensitivity of each laser power was repeatedly measured. The impact of the system error of sensitivity on the measure uncertainty was analyzed. The revised method was proposed. The sensitivity in the narrow power interval and near the optical power was corrected pass through two electrical calibrations. Different laser powers were measured with the new method and the traditional method. The measure uncertainties were compared. Experimental result indicate that the relative uncertainty of the sensitivity achieved from the wide power interval is 2.7%. The system error of sensitivity cannot be neglect when measuring lower laser power. When laser power is lower than 20 mW,the relative measure uncertainty of the new method is still 0.1%. The new method possess a better stability. The error of sensitivity is compensate. Therefore,the difference between electrical and optical calibration is extremely large,and does not have comparability. The total dynamic range calibration needs the combination of electrical and optical calibration. The dynamic measurement range is extend by the new measure method,which is significant for calibrating SIRAs.
2016, 45(9): 917002.
doi: 10.3788/IRLA201645.0917002
A photoelectric encoder measurement system was designed to achieve dynamic encoder measurement and improve the efficiency of the measurement in mass production. Firstly, error sources of photoelectric encoders were analyzed, and their features were recognized. Secondly, based on the feature, encoder measurement was accomplished by adopting differential method, and the detection system was designed by software and hardware. Lastly, experiments were conducted to verify the system. The results showed that the system is capable to detect encoder errors at speeds ranging 0-8 r/s, and the results are straightforward, accurate, and swift, which highly improve the efficiency of encoder measurement.
2016, 45(9): 917003.
doi: 10.3788/IRLA201645.0917003
By analyzing the roles of target motion parameter filter used in photoelectric tracking control system and the principle of IMM(Interacting Multiple Model), application of IMM filter used in photoelectric tracking control system was proposed. Simulator model of Application of IMM used in photoelectric tracking control system was established. By analyzing different target tracking data in simulation environment, the interactive multiple model algorithm could be used as a feedforward control data acquisition algorithm of combinational control technology in photoelectric tracking control system, photoelectric tracking control system uses interactive multiple model algorithm was more suitable than using -- filter for tracking of maneuvering targets.
For the low precision of in-plane displacement measurement using traditional digital speckle correlation methodin frequency domain, a new frequency domain correlation method based on fractal interpolation was proposed. Based on traditional digital speckle correlation in frequency domain, this method utilizes Hanning window function to filter the images in order to overcome the influence of edge effect on final displacement values. Considering theself-similarity of the sub-region and the whole imagein structure morphology and gray characteristics, fractal interpolation was adopted to improve the sub-pixel interpolation, which couldlocate relevant pointsand get more accurate sub-pixel displacement values. Experimental results show that this method could reduce the absolute error within 0.01 to 0.03 pixel and maintain the measurement speed as well. Moreover, the reliability of the algorithm is tested through the rigid translation experiments.
2016, 45(9): 918001.
doi: 10.3788/IRLA201645.0918001
With the development of optical technology, optic-mechanical-electric technology becomes a trend. An integrated, arrayed and miniaturized optical system was required. Binary optical element is famous for its excellent performance in light-wave transformation. Double-layer binary optical element has high diffraction efficiency over wide wavelength range. However, in the fabrication of double layer BOE, many errors occurred, such as height error, periodic error, multi-mask fabrication error etc.A theoretical analysis of these errors was carried out based on scalar diffraction theory, and a MATLAB simulation was implemented. The simulation result indicated that the diffraction efficiency deteriorated if the height errors occurred in different direction rather than in the same direction. Therefore, height errors from different direction should be avoid in fabrication. If the multi-mask fabrication error is occurred from different direction, the diffraction efficiency will decrease more quickly than from the same direction, so multi-mask fabrication error from different direction should be avoid as much as possible. Compared to height error and multi-mask fabrication error, other four errors have varying degrees of impact on the diffraction efficiency.
2016, 45(9): 918002.
doi: 10.3788/IRLA201645.0918002
The temperature variety of the outer baffle for space camera directly affects the temperatures of optical components around the baffle. The thermal deformation of optical components would decrease the quality of image. Three different thermal control approaches were stated out for the baffle of a high-resolution space camera and the analysis and comparison among them were accomplished. Firstly, the most common thermal control means of baffle for space camera were introduced. The orbit heat flux and heat resistant between the baffle and the main body of camera, which affect the temperature of the baffle, were calculated and discussed. Then temperatures and powers of active heaters in three cases were obtained via simulation analysis. After comparison, the third design approach was adopted because of the low power of active heater and high temperature stability. Finally, the thermal design was validated in the thermal balance test and temperature test in orbit. The temperature range of the baffle is between 4.8℃ to 13.6℃ and the second mirror is between 17.8℃ to 17.9℃. The data in orbit are consistent with the analysis results, which indicate that the thermal design is valid and reasonable which can meet the mission requirements.
2016, 45(9): 918003.
doi: 10.3788/IRLA201645.0918003
A 3-DOF parallel 3-PRS mechanism, which could realize one translational and two rotational motions as well as support secondary mirror used in laser beam focusing, was proposed. According to the analysis of motion mode, traditional Euler angle for describing the motion of moving platform was adopted, and based on that, kinematic model of a 3-DOF mini mechanism was built to analyze its inverse kinematics performance. The inverse dynamics modeling with principle of virtual work was derived by introducing a mass distribution factor of link legs. Based upon the established model, two control systems were implemented on the mini 3-PRS parallel manipulator. Then, control accuracy of the robot was obtained by combining ADAMS/Control with MATLAB/Simulink. Moreover, the quality of laser speckle was evaluated by applying the mini 3-PRS robots into an actual optical system. The derived results prove that a mini 3-DOF mechanism can fulfill the design requirements of the structure for supporting secondary mirror.
2016, 45(9): 918004.
doi: 10.3788/IRLA201645.0918004
Under the constrains of single-viewpoint and the requirements of the specific detector and vertical field of view, the equations of eccentricity, thickness of the hyperbolic mirror, install distance and the geometric constraints of single viewpoint hyperbolic catadioptric infrared panoramic imaging system which utilizes the quadratic surface of reflective mirror were derived. At the same time, as for the hyperbolic mirror, the equation of the resolution which include instantaneous field of view in the vertical direction and instantaneous field of view in the horizontal direction of the single viewpoint hyperbolic catadioptric infrared panoramic imaging system were deduced. Under the situation of ideal atmosphere, high target contrast, the simplest range equation which combined with the NVThermIP model was established. The simulation was under the conditions of different size and sensitivity of the detector. The simulation results show that:the spatial resolution of the system increases with the increase of the size of the detector; the range performance of the system increases with the increase of the size and sensitivity of the detector. However the increase of sensitivity is not obvious to the improvement of the range performance.
2016, 45(9): 918005.
doi: 10.3788/IRLA201645.0918005
The adaptive optics(AO) system in which one turbulence layer is corrected has a good compensation performance only over small field of view. The technology of multi-conjugate adaptive optics(MCAO) can overcome the limitation. The elementary structure and working principle of layer oriented multi-conjugate adaptive optics(LOMCAO) system was presented. Simulation method of LOMCAO system was investigated, including how to generate dynamic turbulence wavefront data, wavefront reconstruction algorithm of pyramid wavefront sensor and close-loop modal control procedure of deformable mirror. Simulations for single layer-conjugate and two layer-conjugate AO systems were carried out. The simulation results show that LOMCAO system has better correction performance over a larger field of view than single-conjugate AO system due to the face that much more guide stars are used and two layer turbulence are compensated in LOMCAO system.
2016, 45(9): 916001.
doi: 10.3788/IRLA201645.0916001
The influence of spherical resonant cavity on the radiative characteristics of silver was studied, and the results show that the absorptance is increased in the resonance wavelength. As for a good conductor, the absorption spectrum of silver shows the feature of narrow-band absorption. The absorption peak of the resonance wavelength was shifted to the long wavelength compared to the peak of the resonance wavelength formed by a perfect conductor. Due to the presence of skin depth, the resonant cavity was equivalent to a resonant cavity formed by a perfect conductor with a slightly larger size. With computational results, the effects of structural parameters such as the depth of the resonant cavity, the radius of the cavity, the lattice period, the incident angle and the polarization angle on the absorptance of the spherical resonant cavity were discussed. The results indicate that the optimal narrow-band absorption effect can be obtained by reasonably designing the structure size of the spherical resonant cavity and this implies an effective approach for fabricating narrow-band emitter.
2016, 45(9): 916002.
doi: 10.3788/IRLA201645.0916002
With continuous development and improvement of the microchannel plate production technology, it becomes more and more difficult to enhance its performance by improving traditional crafts. New technologies and new crafts of microchannel plate need to be developed urgently. Development of nano film material and mature preparation technology provide an excellent opportunity for the development of microchannel plate. The channel inner walls are deposited with layer of alumina nano film as secondary electron emission layer by using atomic layer deposition technology, it can increase the secondary electron emission coefficient of channel walls as well as the gain of microchannel plate. The alumina nano films can be deposited in the channel inner walls uniformly with optimized process parameters. The results show that microchannel plate gain changes with alumina thickness, especially it will achieve a high gain up to 56 000 which is about 12 times the gain of normal microchannel plate when the bias voltage is 800 V and the alumina thickness is 60 cycles.
2016, 45(9): 920001.
doi: 10.3788/IRLA201645.0920001
The development of the optically addressed spatial light modulator (OASLM) was reported. Its structure and working principle was introduced in detail. Meanwhile, the photosensitive response curve, static wave-front distortion and temporal waveform distortion was investigated in detail in the process of experiment. Besides, OASLM was successfully demonstrated in the online experiment. The results show that OASLM not only has the ability to achieve the desired transmittance distribution, but also has no additional effect on the high-power laser system. Finally, the shaping effect of spatial filter in the laser system was analyzed. The result shows that the size of spatial filter was also an important factor which determined the shaping precision when this device was used in high power laser systems.
2016, 45(9): 920002.
doi: 10.3788/IRLA201645.0920002
Complicated battlefield electromagnetic environment seriously affects the safety, reliability and technical index of airborne electro-optical platform. Electromagnetic shielding of minitype airborne electro-optical platform was designed in order to improve its battle efficiency. Firstly, the shielding effectiveness of electromagnetic shielding was expounded. Design of electromagnetic shielding was carried out for minitype airborne electro-optical platform from the aspects of circuit board, ABS shell, gaps and video transmission. The shielding effects were verified by electromagnetic compatibility test. The test results show that the video image is normal, conduction emission value is reduced by about 20 dBV, radiation emission value was reduced by about 10 dBV/m, and other items test are improved to varying degrees, which provide a reference for the design of electromagnetic compatibility for minitype airborne electro-optical platform.
2016, 45(9): 921001.
doi: 10.3788/IRLA201645.0921001
Transparent Conductive Films(TCFs) electrode electro-optic pockels cell is an ideal switch device for high repetition rate laser system. High repetition leads to heat accumulation on the electro-optic crystal, which cause thermal-optical effect, elasto-optical effect and bulk displacement, then results in the generation of wavefront distortion. Aimed at 1 kJ output energy and 16 Hz repetition frequency laser system, the TCFs electrode pockels cell was designed using liquid cooling technology. Thermal analysis models of pockels cell were established using the finite element analysis. The influence of crystal thickness and convective heat transfer coefficient on wavefront distortion were researched, and the optimal value of crystal thickness was got. Considering the distribution of liquid flow, the thermal designed data were analyzed. Besides, the temperature, bulk dispalcement and sress distribution were simulated to get the related wavefront distortion and optimal structure value. The researched results can be used to guide the design of the repetitive frequency electro-optic switch.
2016, 45(9): 921002.
doi: 10.3788/IRLA201645.0921002
The surface of the K403's thin slice specimen uses laser shock processing technology in order to strengthen the surface on the nanocrystallization, located on the surface of the specimen, for the cast parts of the nickel-based superalloy K403, which produced cracks, corrosion, and wear. The formation mechanism of the nano-crystal layer on the surface was analyzed by these technologies using X-ray diffraction(XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that a nanocrystalline layer of 226 nanometers thick could be prepared by laser-induced high-pressure plasma shock wave on the specimen's surface. The results of XRD and SEM showed that it will not change the phase structure by that laser shock processing the refined surface grain structure. Under the high pressure, the surface microstructure of K403 specimen generated a great number of dislocations and refinement grains into nanoscale.
2016, 45(9): 925001.
doi: 10.3788/IRLA201645.0925001
An equivalent circuit model of mixing Schottky diode with cut-off frequency of 5 THz was reported based on DC measurement and 3-D electromagnetic(EM)simulation combined of EM simulator and circuit simulator. The model of nonlinear Schottky junction and 3-D periphery structure full-wave simulation model was researched carefully, the four-ports model considered real circuit topology was established. The equivalent circuit model can be used for design of mixers worked at the lower end of terahertz band, the methodology of this diode model was a reference of much more higher terahertz frequency. A sub-harmonic 220 GHz wideband mixer was designed based on the model, the double sideband conversion loss was less than 10 dB in the range of 192 GHz to 230 GHz, the measured result was well with the simulated result.
2016, 45(9): 922001.
doi: 10.3788/IRLA201645.0922001
Aiming at two kinds of typical optical fiber sensor based on SPR effect, which are traditional multimode optical fiber sensor coated with metal film whose cladding is corrosion, and a novel single-mode optical fiber grating sensor coated with metal film, SPR theoretical model and processing method were presented. First of all, according to the structural characteristics of traditional fiber SPR sensor, using the theory of plate SPR effect, reflection spectra of this sensor were given. Meanwhile, it is pointed out and proved that thin film optical theory and theory of SPR are equivalent in the flat structure. Secondly, according to the structure characteristics of novel SPR fiber grating sensor based on mode coupled theory, combined with the feature of SPW mode, the theory processing method of SPR in fiber grating was put forward, the transmission spectra of triple-cladding LPFG coated with gold film were given. Finally, the comparative analysis on the sensing characteristic of two kinds of typical optical fiber sensor based on the SPR effect was carried out, and the results show that two kinds of structure have high resolution of environment refractive index, but the resolution novel optical fiber grating SPR sensor is higher 3 orders of magnitude than that of traditional fiber SPR sensor.
2016, 45(9): 922002.
doi: 10.3788/IRLA201645.0922002
The transmission performances of polarization information in various scattering systems were introduced based on Stokes vectors and Monte Carlo(MC) simulation algorithm. According to the Stokes vectors' scattering characteristics of polarized light, the polarization retrieve(PR) method was proposed theoretically, which is aiming at reducing the scattering impact on incident polarized light and increasing the transmission efficiency of light signals. In order to prove the availability and practicability of PR method, simulations on the polarization transmission and reconstruction in atmosphere and underwater, were complemented in different actual environmental circumstances. The results demonstrate that the PR method is more applicable to disordered media with relatively larger particles and the longer wavelengths can reduce the loss of polarization information effectively. Furthermore, the simulated results reveal that the downlink and uplink are not exchangeable in an inhomogeneous atmospheric medium. In underwater, the PR method is also used to reduce the scattering impacts on the degree of polarization(DoP) of the light, and the maximal enhancement of the degree of linear polarization(DoLP) can reach to about 16% by PR method. These results are significant to the quantum secure communication in atmosphere and underwater in future.
2016, 45(9): 922003.
doi: 10.3788/IRLA201645.0922003
The 2D gimbal servo mechanism of the satellite-borne laser communication terminal, which is a pointing-regulating mechanism with high precision, has a strict requirement of temperature level and uniformity at the working time. The acute change of the orbital heat flux is the external factor that induces the temperature volatility. The thermal control scheme of the 2D gimbal servo mechanism of the GEO satellite-borne gimbal-type laser communication terminal was proposed. In the scheme, the structure design and material selection based on the structural/electrical/thermal concurrent design, active tracking temperature control, thermal dissipation and insulation design were all used to realize the precise control of the stability and uniformity of the temperature field of the space 2D gimbal servo mechanism with large scale and high precision. Meanwhile, the scheme was verified by both the thermal simulation and experiment test. The results show that the temperature range of the servo mechanism's core component is from 22.3℃ to 34.6℃ and its temperature difference is less than 4℃ in the whole lifetime on the working orbit.
A new edge detection method based on Fuzzy C-means clustering and Canny operator was proposed to detect the defects of infrared thermal imaging with large noise, edge information ambiguity and so on. In this method, the gray scale transformation of the input infrared image was carried out, and the image was segmented, extraced, and binarizated by the Fuzzy C-means clustering; then each area was superimposed to make the edge of infrared image continuous. Finally, the image was processed by the Canny algorithm, and the edge of the infrared image was continuous. Canny operator was used to detect the edge of the image, and the defect recognition was realized. Based on the image edge detection, the relative error between calculated and actual defects position was analyzed, and the geometric size quantitative detection of defects was realized. The results show that the proposed method can detect the defect edge completely and clearly, and has higher accuracy and anti-noise ability, which is advantageous for the identification and quantitative detection of defects.
2016, 45(9): 928002.
doi: 10.3788/IRLA201645.0928002
In fog and haze weather conditions, scattering of atmospheric particles greatly reduces the outdoor visibility. Images captured by vision system suffer from serious degradation. Haze removal using the dark channel prior is considered to be a good solution due to its advantage of simple implementation and pleasing result with little constraint. While the selection of scale(radius of patch size) determines quality of the recovered image. For different scenes, there is no generally applicable scale. To solve this problem, in this paper, a scale adaptive method was proposed. It adjusted the range of scale adaptively according to features of color and edge, and get the pixel-level scale of dark channel. Proposed method has both advantage of little color distortion and little halo artifacts. In addition, an improved method of atmospheric light estimation was proposed. By this approach, the estimation point robustly fell into the background region, and that was physically sound. Experimental results on a variety of outdoor hazy images demonstrate that the proposed method is general applicable. The method also achieves pleasing results of haze removal with good color atmosphere and higher contrast.
