2016 Vol. 45, No. 5
column
- Invited paper
- Infrared technology and application
- Laser technology
- Photoelectric devices and microsystem
- Advanced optical material
- Optical design and simulation
- Laser radar technology
- Terahertz technology and application
- Space optics
- Atmospheric optics
- Advanced optical imaging technology
- Optical remote sensing
- Optical communication and optical sensing
- Photoelectric navigation and control
- Photoelectric measurement
- Information acquisition and identification
2016, 45(5): 502001.
doi: 10.3788/IRLA201645.0502001
The modeling, design, implementation and experimental verification of dual-wedge scanning system was introduced, which as the key components of the large airborne LiDAR. In order to achieve large size, wide field of view and high precision pointing of dual-wedge scanner system, the dual-wedge which was 16 wedge angle and 320 mm diameter and corresponding PID biaxial scanning control module were designed, and the sources of system error and error control method were analyzed. In the ground test of 45 m away, rotating wedge mirror every 3.6, for 100 times, companed with the measurement true value, and through calibration and validation, the scanning point error was less than 50 rad. The flight experiments are carried loading with the integrated airborne LiDAR, the measured scanning field of view is 32.03, verifies the validity of dual-wedge scanning system in further.
2016, 45(5): 504001.
doi: 10.3788/IRLA201645.0504001
Reducing the thermal stress of the functional module is one of the key goals in the process of design and fabrication of focal plane assembly. As a result the characterization and measurement of the deformation of the module at low temperature is required. Generally the thermal stress is characterized by indirect parameters such as the deformation in engineering. Based on this, a measurement method including its error analysis of laser interference used to acquire the deformation of the cooled infrared detector was discussed. This method overcomes the difficulty of temperature control and frosting inherent in the other method. It uses the interference pattern produced in the surface of the standard mirror by interference of coherent light to characterize the deformation of the sample. Tests show that this method can realize the measurement of deformation of real-time temperature changes. As a result an in situ measurement of the deformation of the FPA module packaged in the dewar is realized.
2016, 45(5): 504002.
doi: 10.3788/IRLA201645.0504002
A modeling method of infrared dynamic radiation characteristics of the space target was presented. Infrared radiation of the target consists of self-emitted infrared radiation and reflected background infrared radiation. A physical model of radiation characteristics of the space target was established according to target and background characteristics. The target surface was divided into regions and grids based on material properties. According to thermal equilibrium equation of outer space target, a mathematical model on infrared radiation characteristics of the space target was presented based on conservation of energy principle. Bidirectional Reflection Distribution Function (BRDF) was introduced to describe infrared reflection characteristics of the target surface element, and a mathematical model on infrared reflection characteristics of the target was built by superimposing all the reflection components of surface elements. Finally, a body coordinate system was set and the relative positions of the target, the background radiation sources and the detector were determined in terms of coordinate conversion. Simulation of the target infrared characteristics in orbit was achieved according to its given orbital parameters, physical dimension and physical parameter of the target. The calculations show the model is valid and it can provide reference data to visible detection and recognition of space targets.
2016, 45(5): 504003.
doi: 10.3788/IRLA201645.0504003
Numerical generation method of random surface was used to simulate the topography of satellite undulating surface. Considering the radiative flux of space environment, the surface temperature distribution was calculated through the energy equation, with the transfer coefficients determined by Monte-Carlo method. Undulating surface infrared characteristics were calculated and analyzed, through the model by the Torrance-Sparrow bidirectional reflectance distribution function, which is based on the common material and aluminized polyimide film. Simulation results show that infrared characteristic of the undulating surface is quite different from those of ideal plane surface. The surface temperature distribution and infrared characteristics are strong correlative with the surface topography, which provides the research of space infrared detection technology with more effective support.
2016, 45(5): 504004.
doi: 10.3788/IRLA201645.0504004
The infrared focal plane arrays(IRFPA) have been applied in various areas, e.g. safety, space exploration, environmental monitoring, industry control. Due to the characteristics of small amount and high price, reliability has become a major bottleneck problem for IRFPAs' development. As failure pixel, bad pixel is an objective reflection of IRFPA's performance, so it is very suitable for failure analysis and reliability evaluation. Bad pixels were divided into initial bad pixels(IBPs) and used bad pixels(UBPs) by the boundary of delivery time, and their characteristics were analyzed such as type, nature, quantity, location and distribution et al. At the same time, according to hybrid IRFPAs' structure, the cause of bad pixel was studied by three aspects: the detector chip, indium bump and ROIC. Meanwhile, the feasibility to study IRPFAs' damage stress, failure position, damage mechanism and device evaluation were discussed all around. The research of bad pixel can be used to optimize the structure and process, and it also can improve the accuracy of bad pixel identification and replacements.
2016, 45(5): 504005.
doi: 10.3788/IRLA201645.0504005
In order to improve the phase calculation speed and detection efficiency of Pulse Phase Thermography(PPT), a fast phase algorithm optimized from Fast Fourier Transform(FFT) was proposed, with which the calculation speed could be increased by 1.9-12.4 times. To solve the optimal sampling length of thermal image sequence and frequency ratio, the calculation method for optimal sampling length was proposed based on the heat diffusion formula. Experiment was carried out on aluminium and iron specimens. Results show that the optimal sampling length is 1.1 s and 3.9 s for aluminium and iron specimens respectively and the phase difference at fundamental frequency has the best capability to distinguish defects. The calculation speed is evidently improved by the proposed fast algorithm and the optimal sampling length can be directly calculated by the improved numerical formula. Operation subjectivity and random settings of parameters can be avoided and the detection efficiency of pulse phase thermography can be improved.
2016, 45(5): 504006.
doi: 10.3788/IRLA201645.0504006
According to the difference between theory detection and battlefield detection ability of airborne IRST system, the relation between airborne IRST and operational requirement or detection ability was analyzed firstly. Secondly, considering the operational factors as relative entering angle, azimuth angle, pitch angle, environmental background radiation and so on, the models of detection ability in level and pitching angle on airborne IRST were built. Finally, the concept of detection probability envelope was put forward based on operational environment and the character of detection probability, and the model of detection probability envelope on operating range and the ability of airborne IRST and its probability were analyzed quantificationaly in different battlefield situations. It can be seen from the results of simulation that when meeting the demands of false alarm probability and SNR, the detection probability envelope has optimum detection point, which provides theoretical reference for guiding aircraft to change the situation and develop the operational effectiveness of airborne IRST. Meanwhile, it also provides theoretical support for simulating real battlefield environment and test in lab.
2016, 45(5): 505001.
doi: 10.3788/IRLA201645.0505001
In the field of precision measurement, He-Ne lasers are the prior choice to manufacture laser interferometer, which takes the wavelength as the scale in measurement. Therefore, the frequency stability is of great significance. The theories of frequency stabilization in dual-frequency lasers was studied and the isocandela points of the parallel and vertical light were utilized as frequency stabilization points. By designing thermal servo control circuit based on light intensity balance and controlling in both analog and digital methods, the frequency stabilization in Zeeman-birefringence He-Ne dual-frequency lasers was accomplished. Beat frequency experiments were carried on a Zeeman-birefringence He-Ne laser with 7.95 MHz frequency difference, the frequency stability index can reach the level of 10-9. The uncertainty in frequency was better than 1.07410-8(k=2) in repeated measurements. Meanwhile, the stablity of the frequency difference was measured. The variation of the frequency difference was within 8 kHz and the relative deviation was 0.001, which can totally meet the demands of commercial dual-frequency laser interferometers.
2016, 45(5): 505002.
doi: 10.3788/IRLA201645.0505002
Thermal effects could dramatically destroy the performances of the orthogonal-polarized He-Ne laser featured with an integrated Y-shaped cavity. To explore detailed impacts on the output frequency difference stability, one thermal model was established via the ANSYS software. Material disposals and heat source loading were presented, including the calculations of heat flux density and transfer coefficients. Thermal features were shown and discussed both in steady-state and transient-state. Later practical experiments were employed with a thermal infrared imager. The differences between simulations and experimental results were barely smaller than 1%, which had validated the accuracy and reliability of the simulations. After the laser setting to work, heat gradually transmitted from gain area to non-gain area. When the temperature distribution of the laser was in steady state, the cavity surface regions had maximum thermal gradient. The points maximum temperature were always near the cathode, while those with minimum temperature were close to the underlying surfaces of the sub-cavities. The temperature difference was about 0.05℃ between the surfaces of the sub-cavities, and the resulted frequency drift was about 0.067 MHz. It reveals that the time-dependent temperature divergences between two sub-cavity is still the main restricting factor in the stability of the laser output frequency difference, which can provide some important guidance for improving the stability of laser frequency difference and optimizing the design of laser geometry construction.
2016, 45(5): 505003.
doi: 10.3788/IRLA201645.0505003
2.1 m GaInSb/AlGaAsSb double quantum well lasers were reported. With optimization of epitaxial design and ohmic contact, these uncoated broad-area lasers exhibited a maximum power conversion efficiency of 9.8% which was 1.5 times greater than previous value, a room temperature continuous wave output power of 615 mW and a pulsed wave output power of 1.5 W were achieved. The threshold current density of these lasers was as low as 126 A/cm2, and the slope efficiency was as high as 0.3 W/A. By testing lasers with different cavity lengths, the internal loss and the internal quantum efficiency were measured as 6 cm-1 and 75.5%, respectively, which were all improved compared with previous device. The output power of laser diode operated in CW mode shows no apparent degradation after 3 000 h.
2016, 45(5): 505004.
doi: 10.3788/IRLA201645.0505004
To make the laser diode(LD) pump source of laser operate reliably in a wide ambient temperature range without temperature control system, and improve the absorption efficiency and stability of the pump light, the spectral properties of LD and the absorption spectrum properties of Nd:YAG were analyzed, then a new theory and method to design LD pump source with multi-wavelength were proposed, and the absorption length in the gain media was increased to overcome the disadvantage produced by the mismatch between the LD wavelength and the absorption peak of Nd:YAG. A LD pump source with three wavelengths(802.35 nm@25℃, 813.15 nm@25℃ and 810.95 nm@25℃) was designed. The simulation result shows that the pump light absorption efficiency can reach 73.96% under a certain absorption length, and while the ambient temperature changes from -15.7℃ to 65.7℃, the instability of the output energy is less than 5%. The influence of the absorption length and the doped concentration of Nd3+ in the laser crystal on the pump light absorption efficiency was also simulated.
2016, 45(5): 520001.
doi: 10.3788/IRLA201645.0520001
Based on space applications, avalanche photodiode (APD) optimal gain control was investigated in terms of space borne laser range finder. By introducing current SNR(signal to noise ratio) model, the key factors were analyzed which mainly affects SNR of APD in space borne laser range finder. According to special application of space borne laser range finder, optimal gain control of APD was studied. Temperature feedback control circuit for APD optimal gain was designed, temperature digital feedback control algorithm for APD optimal gain was deduced, and the validity and temperature adaptability of the control circuit and the algorithm were demonstrated. It is shown from the experiment that, because of the designed control circuit and algorithm, the gain factor of APD maintains is constant in the temperature range from -25℃ to 60℃, which meets the requirement for space borne applications.
2016, 45(5): 520002.
doi: 10.3788/IRLA201645.0520002
In order to study the dark current of the devices, in this paper, the dark current of In0.83Ga0.17As p-i-n photodiodes was analyzed. Extended wavelength In0.83Ga0.17As p-i-n photodiodes with mesa type configuration were fabricated by two different processes. The first process(device marked M135L-5) was: rapid thermal annealing (RTA) was performed after mesa etching. The second process(device marked M135L-3) was: RTA was performed before mesa etching. Dark current mechanisms for extended wavelength In0.83Ga0.17As p-i-n photodiodes with different device fabrication processes were studied by means of the current-voltage curves at different temperatures and bias voltages. In contrast to M135L-5, M135L-3 had a lower dark current at the same test temperature from 220 K to 300 K. The ratio of perimeter-to-area(P/A) was used to characterize the perimeter-dependent leakage current and the area-dependent leakage current. The results show that M135L-3 has a lower area-dependent leakage current. Activation energy of devices served as a method to estimate the dark current composition was extracted from current-voltage curves. The results indicate that the dark current of M135L-5 is dominated by diffusion current at reverse 0.01-0.5 V bias voltage and at 220-270 K. The dark current of M135L-3 is dominated by diffusion current at 250-300 K as well as dominated by generation recombination current and surface recombination current at reverse 0.01-0.5 V bias voltage and at 220-240 K. Meanwhile, the results of dark current fitting also show the same conclusions. The studies have shown that M135L-3 with annealing treatment and optimization process is better than M135L-5 for reducing dark current because the RTA decrease the bulk dark current.
2016, 45(5): 520003.
doi: 10.3788/IRLA201645.0520003
Electro-optic modulator is one of the most important components for optical communication system. Its performance determines the transmission performance of an optical communication system. For the electrode, its structures, species and designs have a significant influence on the property of modulator. For designing and researching the electrode of novel electro-optic modulator based on FBG, the relationship among the overlap of mode field, structural parameters of electrode and FBG's center wavelength shift were discussed in this paper by numerical calculation methods. It has a significance of manufacture of polymer electro-optic modulators based on FBG, and promotes the development of electro-optic modulator.
2016, 45(5): 520004.
doi: 10.3788/IRLA201645.0520004
The design of a CMOS-technology compatible SiGe/Si single photon avalanche photodiode was presented. The influence of doping condition on electric field distribution, the bandwidth characteristic and the quantum efficiency of detector were discussed in detail. A shallow-junction, Geiger-mode avalanche photodiode to provide single-photon-counting capability at 1.06 m with a low-breakdown voltage(30 V) was designed. A separate absorption and multiplication(SACM) structure was used to fabricate the SiGe/Si avalanche photodiodes, where Si material was taken as the multiplication region. Taking advantage of the higher silicon carrier ionization coefficient, noise was reduced, the quantum efficiency of SiGe detector is 4.2% at 1.06 m, which has a 4 times enhancement compared with the Si detector. Simulation results indicate the optimum doping conditions can realize a suitable e-field distribution, thus obtaining good bandwidth characteristic at the required breakdown voltage of the APD.
2016, 45(5): 520005.
doi: 10.3788/IRLA201645.0520005
An analytical modeling of In0.53Ga0.47As/In0.52Al0.48As avalanche photodiode(APD) was proposed with In0.52Al0.48As charge layer between the absorption and multiplication region(SACM). Numerical study and theoretical analysis were performed to design a high performance In0.53Ga0.47As/In0.52Al0.48As APD. An In0.52Al0.48As barrier layer was adopted to block minority carriers originated from contact regions in our APD. Simultaneously, double-doped multiplication layer was used to improve the electric field gradient change of the multiplication region and reduce the dark current. In addition, the influence of different doping level and different thickness of every layer on the energy band, the electric field distribution, breakdown voltage and current-voltage characteristics were also investigated by using device simulation software ATLAS from SILVACO international. The photodetector exhibits a high responsivity of 0.9 A/W at the unity gain. The gain is 23.4 at the operating voltage(0.9 Vb). Furthermore, the dark current is only in the nano-ampere orders of magnitude at 0.9 Vb.
2016, 45(5): 520006.
doi: 10.3788/IRLA201645.0520006
The effect of electron irradiation on CMOS image sensor was studied, focusing on average dark current and light intensity response. The CMOS image sensors, some in operating mode and the others in non-operating mode, were radiated simultaneously. The data were collected when the total dose of radiation reached 5103 rad, 1104 rad, 7104 rad, 1105 rad, 5105 rad, respectively. The results showed that, when the total dose of radiation exceed a threshold between 7104 rad and 1105 rad, dark current of the imager showed a basically linear relationship with the total dose of radiation. When concerning the light intensity response, for the imagers which were radiated in non-operating mode, radiation have no effect on the response; while for the imagers which were radiated in operating mode, with the total dose of radiation exceed a threshold, 7104 rad, the response curves shifted down and the slopes decreased with the total dose of radiation increased. In other words, radiation reduced sensitivity of the imagers. At last, the model of dark current versus total dose of electron radiation was developed after theoretical analysis. It is shown that after working in the space for a long time, CMOS image sensors are easily affected by the total dose effect of radiation, thus reasonable protection measures against radiation are needed.
2016, 45(5): 520007.
doi: 10.3788/IRLA201645.0520007
In order to develop the small, low-cost, high-resolution spectrometer, a miniaturization Fourier transform infrared spectrometer was design. By selecting electro-thermal MEMS micro-mirror as the moving mirror of Michelson interferometer to make the Fourier spectrometer miniaturization and portability. At the same time, to ensure a higher resolution, the folding double S Bimorph drive structure of double displacements was designed. The beam splitter was external for selection different wave band flexibly to achieve full spectrum range. Moreover, it used 1 310 nm laser as a reference light source, and tungsten lamp as interference light signal, through the signal acquisition, filtering, interpolation and spectrum recovery steps to complete that signal collected and absorption spectra recovery process. The results show that the displacement of electro-thermal micro-mirror can reach 500 m, and the theoretical resolution of the spectrum can be up to 1 nm, and the spectrometer machine size as small as 62 mm62 mm28 mm. Also the test results show that the baseline noise is 0.000 04, the repeatability of baseline is 0.000 32 and repeatability of absorbance is 0.000 48. The performance can meet spectrum detection applications of the food safety, drug testing, petrochemical and other fields.
2016, 45(5): 520008.
doi: 10.3788/IRLA201645.0520008
In order to improve the application of optoelectronic oscillator, a kind of embedded electrical gain ring resonator mini optoelectronic oscillator structure was introduced in this paper. The demonstrated principle of the electrical gain ring resonator optoelectronic oscillator was using the electrical splitter and amplifier realizing a ring resonator cavity which was equal to a filter comb to select the right mode of the optoelectronic oscillator, combined with directly modulated DFB laser, simple mode fiber and photo-detector, a mini optoelectronic oscillator structure was realized. The principle of the electrical gain ring resonator was analyzed and verified by the simulation. In the experiment, a high quality RF signal with the center frequency of 12.624 GHz was realized, the phase noise of the generated signal was -102 dBc/Hz at 10 kHz offset. The proposed scheme can generate higher quality RF signal with a simple structure, it can be a solution to the practical application of optoelectronic oscillator.
2016, 45(5): 520009.
doi: 10.3788/IRLA201645.0520009
The gain and excess noise of multi-gain-stage superlattice InGaAs APD was mainly studied in this paper, and a new multiplication-excess noise model of carriers was established. Based on the conventional Dead Space Multiplication Theory, we analyzed its working principle. Additionally, we considered initial energy from pre-heat electric field and energy band offset, and the modification of dead space length around heterojunction's boundary when carriers entered high-field multiplication layer, as well as the effect of phonon scattering on impact ionization coefficients. Thus we proposed a modified Dead Space Multiplication Theory to guide the calculation of the gain and excess noise factor of this type of APD device. The results demonstrated that under the same condition, multi-gain-stage superlattice InGaAs APD has both higher gain and lower noise than conventional SAGCM APD with a single multiplication layer, and the modified Dead Space Multiplication Theory can be extended to superlattice InGaAs APD structure with more gain stages. On the premise of low excess noise, its mean gain can be improved by increasing number of gain stages.
2016, 45(5): 521001.
doi: 10.3788/IRLA201645.0521001
Infrared lasers at 2 m wavelength have great application value and good prospects in the environmental detection, wind-measuring radar, tissue ablation as well as optoelectronic countermeasure. The films at 2 m wavelength were often prepared by sulphide, arsenide and other soft material which have high refractive index. In order to promote the damage performance of these films, the oxide material was used whose refractive index was relatively lower but the bandgap was wider to prepare the film. The content of OH and the absorption of the film were characterized by using Fourier infrared spectrometer and the weak absorption tester. By optimizing the fabrication process, the multilayers dielectric thin films which satisfy the requirements of the 2 020 nm Tm laser were successfully prepared. The damage morphologies of the films after the laser damage testing were observed by the differential interference microscope, combining with the electric field distribution and the stress in the film, the damage mechanism of the films were analyzed and further optimization method of damage character was put forward.
2016, 45(5): 521002.
doi: 10.3788/IRLA201645.0521002
To achieve fast zooming by using electro-optic (EO) crystal, the EO crystal and electrode structures are required to be designed properly. Based on electro-optic effect, the basic principle and way of the EO crystal design were proposed. By means of simulation and comparison of internal non-uniform electric field and total additional optical path between linear EO crystal(lithium niobate crystal) and square EO crystal(tantalum potassium niobate crystal), the optimization of the EO crystal and electrode design were obtained. On this basis, the performance of the EO crystals for fast zooming was simulated and analyzed. The influence of the applied voltage and crystal thickness on the total additional optical path was discussed. Results show that the curvature radius of additional optical path decreases with the increasing of the control voltage, while increases with the increasing of the crystal thickness for a given applied voltage. In practical applications, the crystal thickness and applied voltage need to be considered comprehensively to achieve better zooming effect.
2016, 45(5): 518001.
doi: 10.3788/IRLA201645.0518001
In order to increase spatial resolution, five-mirror afocal optical system with axial-symmetric primary mirror was designed, which was used for principal system of image space scanning system. The system was well compact and axial-symmetrical. The method of five mirror afocal system design based on primary aberration was explored. The structural parameters were calculated according to magnification and obscuration ratio of each mirror. The conic parameters were calculated according to primary aberration coefficient. The procedure for calculating initial structural parameters was programmed. Then a five-mirror afocal system was designed with an entrance pupil diameter of 1 m, a field of view of 50.1, the operating wave band of 8-10 m, compression ratio of 10 times. The results indicate that the maximum root mean square (RMS) wavefront error is less than 0.065(=9 m), the maximum optical path difference(OPD) is less than /4(=8-10 m). It has high imaging quality and the modulation transfer function (MTF) is approached to the diffraction limit. The method of afocal system design can be widely used for high spatial resolution multichannel imaging.
2016, 45(5): 518002.
doi: 10.3788/IRLA201645.0518002
Based on the requirement of the laser guidance weapon platform with small caliber and large instantaneous field of view, the scheme of a small strapdown defocused refraction optical detection system was proposed. According to the target detection model of strapdown semi-active laser guidance and the ideal defocused optical system model, the optimal system parameters were obtained with the consideration of the application of laser guidance. Based on these parameters, ZEMAX was used to optimize the defocused optical detection system with the work wavelength of 1 064 nm. The critical effective detection half field of view of this system were 5.89 degrees, the critical detection half field of view were 13 degrees, and the length diameter ratio was 1.27. The aberration from the dome was solved well. The linear relationship between spot centroid position and target position deviation angle was presented. The experimental results show that the error of the designed optical defocused detection system is less than 0.15 degrees, meeting the requirement for target position deviation angle detection of large field of view.
2016, 45(5): 518003.
doi: 10.3788/IRLA201645.0518003
A new optical system to increase the Bessel beam's diffraction-free distance was designed and simulated based on traditional axicon method and geometric optical effects of concave lens. In the system, the concave lens was placed in front or in rear of the axicon. By simulating this program with Math CAD and comparing with traditional axicon method, some results were obtained that the diffraction free distance was increased from 244 to 638 mm, with central spot magnified when the concave was placed in front, and was increased to 406 mm when the concave was placed in rear. He-Ne laser was used as light source, the experimental results are consistent with the theoretical analysis and numerical simulation. Therefore, a certain curvature radius of the concave lens and the position according to actual requirements can be chosen to obatin the Bessel beam with a longer diffraction free distance and higher quality.
2016, 45(5): 518004.
doi: 10.3788/IRLA201645.0518004
The small angle lighting is always a thorny problem in the LED lighting field. The LED lenses and reflectors were important optical devices, which was the key to solve the above problem. So the design of lens and reflectors has been a hot research topic recently. The theory of geometrical optics was used to calculate the coordinates on the lens surface in this paper. Then, the lens model can be constructed based on the coordinates. In order to facilitate understanding, the 30and 45 lighting lens were taken as examples to introduce the design process. The research findings show that these lenses can concentrate light rays within the predetermined small angles. Furthermore, the efficiency and uniformity are more than 80% and 85% respectively, which can meet the needs of the modern lighting.
2016, 45(5): 530001.
doi: 10.3788/IRLA201645.0530001
Differential absorption lidar is an effective methods for high-precision CO2 concentration measurements. In this paper, the major error sources of airborne differential absorption lidar CO2 measurement were studied, and CO2 concentration errors caused by them were analyzed. The airborne differential absorption lidar principle was introduced first, CO2 concentration errors from atmospheric temperature, pressure and water vapor uncertainties, laser frequency stability and the aircraft speed and attitude measurements uncertainties, as well as random error were analyzed. The results show that airborne differential absorption lidar measured CO2 column concentration error is about 0.71 ppm(1 ppm=10-6) for 380 ppm atmosphere CO2 concentration, which meets the 1 ppm accuracy requirement of CO2 concentration measurement.
2016, 45(5): 525001.
doi: 10.3788/IRLA201645.0525001
In this paper, terahertz spectroscopy technique was used for the investigation of human renal cancer by comparing the response of tumor tissue and normal tissue adjacent to tumor. Based on the measurement and analysis of fresh tissue and lyophilized tissue respectively, the absorption coefficient and refractive index from 0.2 THz to 1.2 THz were obtained. The result shows that water content of biological tissue has great influence on terahertz wave absorption signal amplitude. Meanwhile, difference of cell structure and composition also affect the transmission of terahertz signal. For example, as the different structure and composition of the cancer and normal cell, the absorption coefficient and refractive index of these tissues are completely different. The result indicates that terahertz spectroscopy technique is an important technology and has a broad prospect of application in biological tissue investigation and clinical medicine such as tumor disease diagnosis.
2016, 45(5): 513001.
doi: 10.3788/IRLA201645.0513001
During the onboard imaging process of space camera with large field of view, due to the effects of earth rotation, satellite attitude maneuverings, jittering and other factors, image motion velocity field of the focal plane has a non-linear anisotropic distribution. To overcome this problem, a novel image motion velocity field modeling method which is based on kinematics of rigid body was proposed. In this model, off-axis angle parameter was introduced and formulas of image motion velocity field in the large view off-axis three-mirror system were derived. Taking a certain large field space camera as an example, influences of synchronous and asynchronous velocity matching models on the camera image qualities were analyzed. Results show that, under a constraint of 5% drop and with scroll angle of 15, if integral stages are larger than 10, asynchronous velocity matching models should be adopted. Especially when integral stages are fixed to 32, its dynamic MTF on focal plane can be improved to 0.970 2 while it is 0.340 8 in the synchronous model case. However, synchronous velocity matching model outperforms in the condition of 16 integral stages and 12.3 scroll angle. Onboard imaging experiments proved the accuracy of the models which will provide a reliable basis for large field space camera image motion compensation.
2016, 45(5): 511001.
doi: 10.3788/IRLA201645.0511001
Growing urban pollution leads to the rise of the carbonaceous particle content in the atmospheric environment. To further research the influence of the humidity on transmission characteristics of polarized light, radius, refractive index and the other parameters of aerosol particles at different humidities were studied, and through Monte Carlo method the transmission process of different incident light in carbonaceous medium was simulated, which could get the Stocks simulation pattern and polarization characteristics of the emergent light. The results show that the change of increase of the relative humidity can influence the polarization characteristic regularly. With the increase of the relative humidity, when the incident light is linear polarization, the polarization characteristics of emergent lights will have a increasing tendency, and can keep their polarization states; When the incident light is circular polarization, the degree of polarization(DOP) of the emergent light will have a maximum value at the humidity of 85%, and there will be no obvious regularity in the fluctuation of DOP and polarization angle. Therefore, when the incident light is linearly polarized light, the emergent light has a more advantageous in the polarization state keeping and polarization characteristic enhancement with the increase of the relative humidity.
2016, 45(5): 511002.
doi: 10.3788/IRLA201645.0511002
The particle image velocimetry (PIV) and high-speed photographic camera (HSC) photography were employed to study two-phase flow properties of gas flow field and burning particle flow field in the flame of the pyrotechnics. Particle image velocimetry tested the gas flow field of burning flame of pyrotechnic powder, while the high-speed photographic apparatus captured the pyrotechnic flame of burning particles through full-course after filtering out the impact of gas flame radiation and soot by setting the exposure time. The coordinate of each burning particle in the image was determined by the image processing method. Moving trajectory for each burning particle was calculated according to continuous images, and then got the velocity vector diagram of burning particles. Furthermore, particle and gas flow fields of burning particles were comparatively analyzed. This study provided a simple method of analyzing the flame structure of burning particles for the combustion mechanism of pyrotechnics.
2016, 45(5): 524001.
doi: 10.3788/IRLA201645.0524001
Image plane intersection interference imaging spectroscopy is a kind of compact imaging spectrometer technology, which has characteristics of small volume and light weight, and is used for small satellite remote sensing mission or airborne photoelectric reconnaissance. Image plane intersection interference imaging spectroscopy was studied. The design scheme of angle shear beam splitter was given based on Mach-Zehnder composed of prisms. Work principle and design method were discussed in detail. The angle shear of beam splitter based on Mach-Zehnder was analyzed under certain spectrum resolution combined design example. At same time, object characteristics of image plane intersection interference imaging system was studied. Image plane intersection interference imaging spectroscopy technology was verified in experiment.
2016, 45(5): 514001.
doi: 10.3788/IRLA201645.0514001
In order to make full use of meteorological information and to improve the safety index of the carrier aircrafts, based on an objective analysis for the features and advantage of meteorological information, a safety evaluation model was put forward for the use of carrier aircrafts under pure marine meteorological background. The model was composed of two parts, namely taking off landing safety index and the round-trip safety index. the main relevant factors and evaluation method were given according to the practical use, including the fitting formulas. For the taking off landing safety index, a judge matrix was used to determine the weight of different meteorological factors, a new concept objective meteorological index and it's way of calculation were firstly put forward, then, the taking off landing safety index can be calculated by the way of linear weight adding. For the round-trip safety index, the main calculation method was focused on the covering effect for the aircrafts of clouds and fog.
2016, 45(5): 514002.
doi: 10.3788/IRLA201645.0514002
Electron Multiplying Charge Coupled Device(EMCCD) can realize read out noise of less than 1e- by promoting gain of charges with the charge multiplication principle and is suitable for low light imaging. With the development of back illuminated CMOS technology CMOS with high quantum efficiency and less than 1.5e- read noise has been developed by Changchun Institute of Optics, Fine Mechanics and Physics(CIOMP). Spaceborne low light detection cameras based on EMCCD CCD201 and based on CMOS were respectively established and system noise models were founded. Low light detection performance as well as principle of spaceborne camera based on EMCCD and spaceborne camera based on CMOS were compared and analyzed. Results of analysis indicate that signal to noise(SNR) of spaceborne low light detection camera based on EMCCD will be 23.78 as radiance at entrance pupil of the camera is as low as 10-9 Wcm-2sr-1m-1 at the focal plane temperature of 20℃. Spaceborne low light detection camera worked in starring mode and the integration time is 2 s. SNR of low light detection camera based on CMOS will be 27.42 under the same conditions. If cooling systems are used and the temperature is lowered from 20℃ to -20℃, SNR of low light detection camera based on EMCCD will be improved to 27.533 while SNR of low light detection camera based on CMOS will be improved to 27.79.
A tunable optical millimeter-wave generation scheme was proposed theoretically which was capable of obtaining high multiplication factor(MF), and the performance of Radio over Fiber (RoF) downlink was numerically analyzed. The scheme was based on a dual-driving Mach-Zehnder modulator(DD-MZM) which was driven by triangular wave instead of sine-wave. More harmonics can be generated by using triangular wave sweep. With the help of uniform fiber Bragg grating(UFBG), two of the harmonics can be selected to generate millimeter-wave signal of different MFs. The MF can be tunable by adjusting the Bragg wavelengths of two UFBGs respectively. Millimeter-wave signals with MFs of 4, 6, 8, 10 and 12 were achieved. The RoF downlink transmission performance of all these MFs was evaluated. The eye diagram after 10 km transmission is still wide open under the conditions of all the MFs. The results demonstrate that such a scheme can offer realistic solution to support future wireless systems.
2016, 45(5): 522002.
doi: 10.3788/IRLA201645.0522002
To select the best optimization model on parameter extraction in Lorentzian Brillouin scattering spectrum and improve the accuracy of the temperature or strain measurement, taking the objective functions based on linear and nonlinear least-squares fits as the study objects, the influence of the optimization model on the accuracy of the parameter extraction was systematically investigated. Brillouin scattering spectrum signals with different signal-to-noise ratios, scanned frequency intervals, g0, vB and vB were numerically generated. The accuracy and computing time of parameter extraction and temperature/strain measurement of the linear model were compared to that of the nonlinear model. The results reveal that, if the signal is ideal and free from noise, the two models are free of any errors. The errors of the two models will increase with increasing in noise level/scanned frequency interval. However, the error of the nonlinear model is appreciably lower than that of the linear one. In engineering practice the nonlinear model should be selected. The analysis is validated with the experimental Brillouin scattering spectrum signals.
2016, 45(5): 522003.
doi: 10.3788/IRLA201645.0522003
Scattering characteristics and surface roughness on the surface of the materials make a very important influence on the performance of the product. The multi-wavelength fiber sensor for measuring surface roughness and surface scattering characteristics based on laser scattering was investigated. The special geometric design was used by the probe of fiber optic sensor, specimens with different surface roughness were analyzed by using 650 nm, 1 310 nm and 1 550 nm laser as the light source, respectively. The working distance of 2 mm was chosen as the optimum measurement distance. The experimental results indicate that under the same wavelength, the reflection intensity measured from the reflective surface of grinding samples decrease with the increase of surface roughness. Under the same roughness, the incident wavelength is longer, the reflection intensity is bigger. The multi-wavelength fiber sensor can accurately measure surface roughness, and can effectively reduce the system error. The range of relative error of fiber sensor by analyzing system error is about 3.56%-7.43%.
2016, 45(5): 531001.
doi: 10.3788/IRLA201645.0531001
In order to solve the problem of the declining tracking accuracy for O-E theodolite caused by maneuvering target model inaccurate, the single hidden layer feedforward networks(SLFNs) model was built for maneuvering target, then an dual extended Kalman filter(DEKF) on-axis tracking control method was proposed. The key state parameters of the mathematical model were estimated by the dual extended Kalman filter(DEKF). In the simulation and experiments, the predicted target velocity error is about 0.070 9()/s at the peak of velocity and the tracking accuracy is 2.42' when tracking the equivalent sine object of 83.33sin0.6t, the tracking accuracy reaches 2.96' when tracking the optical dynamic target with 4.5 s rotation period. Tracking results show that SLFNs mode is matched for maneuvering target, DEKF can fast track and estimate the state parameters. As compared with other control methods, the proposed method has higher accuracy and improves the system tracking precision significantly.
2016, 45(5): 531002.
doi: 10.3788/IRLA201645.0531002
In an integrated location system, the establishment of mutual attitude relationships between different subsystems is accomplished by the alignment processing. When the inertial component is used for positioning, the attitude and heading reference system(AHRS) is generally based on geographic coordinate system(E-N-U) as the navigation coordinate system. However, during indoor navigation task, the navigation coordinate system is generally based on the users' requirement such as marked points or workpiece coordinate system. In this paper a new alignment method based on direction cosine matrix was proposed for the integrated positioning system of indoor mobile object. The transformation between geographic coordinate system and external reference coordinate system can be achieved by the method.Then coordinate system of laser tracker became navigation reference and real-time and precise transformation between different coordinate systems can be realized by this new alignment method.Experimental results show that the measured RMS errors for attitude angles after transformation are less than 0.25 while the AHRS is in arbitrary position and orientation.
2016, 45(5): 531003.
doi: 10.3788/IRLA201645.0531003
In order to improve response and decrease the settling time, the structure response of the open loop system will be identified. According to the requirements of the structural dynamics performance of the control system, the design of the rotator control system is significant to improve the system performance. In this paper, a new method was proposed for the system model identification, the sin sweep signal was applied at the input of the open rate loop to excite the plant dynamic, the real time position feedback signal of the rotator was measured at the encoder, each frequency component of the rotator dynamics was analyzed to identify and obtain a meaningful transfer function, and in this article, the theory of the method was analyzed first, and the time series input is a sinusoidal sweep signal. The test of the system frequency response and the transfer function identification were realized through the testing experiment platform using this new method, the experiment chooses a controller designed by C8051F120 and CPLD, the output signal drives the rotator through the driver to verify this approach, and proving its feasibility.
2016, 45(5): 517001.
doi: 10.3788/IRLA201645.0517001
As for using just one laser tracker to measure several points, a new method of visual-guided laser tracking was presented. A camera was set on the top of the laser tracker, and rotates around the laser tracker's Z axis. When measuring, the camera rotated a single revolution with the laser tracker, and captured the positions of all the laser interferometers. The coordinates of the positions in the camera frame can be converted to the laser tracker frame, and then the laser designator projected a laser sheet to the laser interferometers. A planar round hole target was used, and the center of the holes were measured simultaneously by the camera and the laser tracker. The corresponding coordinates in the two frames which were processed using mean method becomes the corresponding vectors in the two frames. The translation of the two group vectors is the rotation matrix of the two frames. Using Cayley transformation, the rotation matrix of the two frames can be calculated, and then the whole relationship between the two frames can be obtained by using any two corresponding coordinates. The advances of the algorithm are the solving process is simple and the results are stable. Simulation is shown that, when the number of the target placing is more than 50, the influence of the image noise is stable, and the measuring error is less than 1 mm. The proposed method is simple, has strong stability, and has very high practical value.
2016, 45(5): 517002.
doi: 10.3788/IRLA201645.0517002
In order to solve the problem of large optical convex spherical mirror testing, a stitching model was established, which was based on global optimization algorithm and least-square method. The full aperture map can be achieved with this relative algorithm. At the same time, based on our model, a 120 mm convex spherical mirror was tested. In the testing, five subapertures were tested. It can be seen that the stitching map is smooth and continuous, with no stitching mark. To evaluate the stitching accuracy, a subaperture called self-calibration subaperture was tested. Comparing the stitching map with the self-calibration map point by point, the residual map can be got. It can be seen from the residual map that the PV value is 0.014 and the RMS value is 0.003, proving the reliability and accuracy of the stitching algorithm.
2016, 45(5): 517003.
doi: 10.3788/IRLA201645.0517003
To measure the dynamic performance of the thirty meter telescope tertary mirror, the model based on the accerleration signal was established for parameters calculation and identification. First and foremost, under the TMT requirement, the procedure to obtian the dynamic property of the system by acceleration signal was presented. Then, by the output to the unknown excitation, the free response can be reached. After that, the polynomials fitting was used to process the transfer function obtained from the previous step to identify the model parameters. This method was then applied to a four-meter scale system, the first two orders of strcture were correspondingly 88 Hz and 107 Hz. What is more, the mode shape is also calculated and the parameters in the modle are modified by it. The work of this artile is expected to be helpful for the accomplishent of the thirty meter telescope.
2016, 45(5): 517004.
doi: 10.3788/IRLA201645.0517004
To calibrate the phase characteristic of a Liquid Crystal Variable Retarder(LCVR) attached with a compensator. For LCVR, under 25℃, 405 nm wavelength, the total of 141 experimental samples were obtained by the built setup based on Stokes parameters, in which 71 samples(calibration set) were used for model calibration, and 70 samples(prediction set) were used to validate the calibrated model independently. Least Squares Support Vector Machine(LSSVM) and Support Vector Machines(SVM) was used to calibrate model. Test results show, for prediction model based on GASVR, PSOSVR, LSSVM, the maximum wavelength deviation are respectively 0.013 6、0.013 7 and 0.004 5, the mean square error is increased by 2 times, and the phase retardation of all the wavelengths and all the voltage values of LCVR in the effective working range could be rapidly and accurately obtained by the LSSVM model, thies the prediction model based on LSSVM was an effective mean for LCVR phase calibration.
2016, 45(5): 517005.
doi: 10.3788/IRLA201645.0517005
In order to improve the pointing precision of photoelectric detecting system, parametric and non-parametric model kinematic calibration algorithms were proposed. Firstly, based on the component of system, the pointing error sources of photoelectric detecting system were analyzed. Subsequently, in times of the parametric model, pointing error model was established by multi-body system theory, and the least square method was used to calibrate the model. Then, aiming at the non-parametric model, bilinear interpolation algorithm was used to calibrate the pointing error. Finally, structure of the experimental platform, and two groups of data were measured to do the kinematic calibration and verify the calibration model. The experimental results demonstrate that the pointing precision has been improved from 141.7 to 22.2 by parametric model calibration, and from 141.7 to 27.9 by non-parametric model calibration. These two algorithms can both improve the pointing precision. As for the system mentioned in this paper, the pointing precision of parametric model calibration is slightly higher, but non-parametric model calibration has simple modeling process and small computational complexity.
2016, 45(5): 526001.
doi: 10.3788/IRLA201645.0526001
The detection for mutation point which suddenly appear and vanish has received much attention in IRST application. With the development of multi-wave band IRST system, a sequential infrared target trajectory detection algorithm based on generalized cumulative sum was proposed. The research extended the single band detection into multiple band detection, which improved the detection probability, greatly reduced the average detection delay and signal-to-noise ratio(SNR) under a certain false alarm rate. Results of simulation analysis show that the modified algorithm has excellent detection performance for infrared mutation point target. In case of a certain false alarm rate, the SNR threshold can be decreased to 60% and dual band detection delay can be reduced about a half comparing with the traditional detection method.
2016, 45(5): 526002.
doi: 10.3788/IRLA201645.0526002
A kind of image fusion system which contained short wave infrared detection, medium wave infrared detection and laser ranging device had been developed. The system realized three functions which were remote scene monitoring, remote target ranging and detecting the laser beam at 1.06 and 1.57 m bands during all day and through the fog. In order to ensure the fusion image quality of system and improve the registration accuracy, an optical axis parallelism correction method to realize the coarse registration between the short wave infrared image and medium wave infrared image has been proposed; a new iteration optimization method which found the optimal register parameters to get the best fusion results has been put forward. This method used definition index of the fusion image interesting region to improve the register process, and used particle swarm optimization algorithm to solve joint optimization problem and to realize the accurate registration. The experimental results demonstrated the potential of the system for applications like remote scene monitoring and battlefield situational awareness.
2016, 45(5): 526003.
doi: 10.3788/IRLA201645.0526003
The phase of space remote-sensing camera CCD signal varies slightly with the temperature shift and the aging of devices. Especially in the field of high speed applications, the change of analog signal phase is non-negligible so that the sampling positions which are determined and programmed with traditional method are no longer suitable. So the SNR of image drops drastically and even in some worse cases images cannot be displayed normally. To solve the problems mentioned above, an adaptive adjustment method for sampling position of space camera CCD signal was proposed in this paper. With the proposed method, the real-time phase variation of CCD analog signal was monitored and the variation parameters of sampling position were calculated. With the calculated sampling position parameters, the circuit adjusted the phase of sampling clocks on line. The sampling position can remain in optimal state although the temperature varied in large range in the life span of the camera and the SNR of images kept high stably. Tests show that with this method, phase variation of less than 100 ps can be detected and the sampling positions keep in optimal state. So the method is effective and has a good application prospect in the field of high resolution remote sensing cameras.
2016, 45(5): 526004.
doi: 10.3788/IRLA201645.0526004
The random frequency signal format not only reduces the instantaneous band-width and data sampling rate, but also has the good characteristics of the radio-frequency immunity. However, the frequency of the signal changes randomly, which makes the traditional methods of scattering-center estimation invalid. Herein, the model of random frequency signal echoes was derived, and a novel parameter estimating method for scattering-center model was proposed based on the analysis of the radar echoes' sparse characteristic. The parameters estimation was converted to the problem of sparse signal reconstruction in the framework of Compressed Sensing(CS). The performance of the sensing matrix was investigated. Experiment results show that the presented method is effect even for low sampling-rate condition.
