2017 Vol. 46, No. 7
column
- Outstanding doctoral dissertation in optical engineering
- Laser technology and application
- Laser radar technology
- Laser technology
- Infrared technology and application
- Ocean optics
- Optical communication and optical sensing
- Optical design and simulation
- Photoelectric measurement
- Photoelectric device and microsystem
- Information acquisition and identification
- Space debris detection
2017, 46(7): 734001.
doi: 10.3788/IRLA201746.0734001
The heat value of coal is one of the most important coal properties that affects the operation of coal -fired boilers. The on -line analysis of heat value of coal can provide important reference for optimizing and adjusting the boiler operation in real time. The heat values of bituminous coal samples were quantitatively analyzed by laser -induced breakdown spectroscopy (LIBS). The 1 064 nm laser radiation emitted by a Q-switched Nd:YAG laser was utilized for laser ablation and plasma generation in air. The partial least square (PLS) method and the dominant factor based PLS method were used to improve the measurement accuracy of heat value of coal. In the dominant factor based PLS model, the molecular emissions of C2 and CN were utilized to build the dominant factor model. The coefficient of determination and the root-mean-square error of prediction of the PLS model were 0.94 and 1.46 MJ/kg, respectively; and those values for the dominant factor based PLS model were 0.99 and 1.18 MJ/kg, respectively. The results show that LIBS has great potential for the on-line analysis of heat value of coal.
2017, 46(7): 706001.
doi: 10.3788/IRLA201746.0706001
A scheme for laser jamming using quasi parallel light interference was proposed. On the basis of the interference theoretical analysis, the multi -beam quasi parallel light interference images and interference intensity maximum value of two beams, three beams and four beams were obtained by HeNe laser, and the interference images and the light intensity distribution were got by simulation. Both theoretical and experimental results show that the patterns of quasi parallel light interference images depend on beam direction angle. In certain direction angle, there is bright stripes or bright spots of interference in the middle of the interference field. The distance between interference stripes or spots is decided by the angle between two beams of light. When the value of the angle between two beams is no more than 0.5 mrad, the experiment data is consistent with the simulation data, and the interference intensity maximum is close to the result of theoretical maximum, that is the light intensity maximum of two, three and four beams of quasi parallel light interference are four, eight, fifteen times the size of the light intensity of single beam. The effect evaluation and the test of validity of laser jamming scheme were given.
2017, 46(7): 706002.
doi: 10.3788/IRLA201746.0706002
To choose the optimal estimating method to evaluate micro-Doppler characteristic of target,the research on the Cramer -Rao Bounds (CRBs), which was used to evaluate the performance of the estimating method, was indispensable. The closed form of CRBs for lidar signals with Gaussian noise was derived strictly in this paper. The relationships between the CRBs and factors including the target position, the length of processing data and SNR were analyzed. The simulation results indicate that decreasing the azimuth angle and pitch angle or increasing the data length and SNR can minish the CRBs of estimated parameters, while, the lower bounds are insensitive to the information of the noise variance. The mean square error of two frequently used estimators for micro -Doppler parameters were simulated and compared with the CRBs. In the end, the meaning of the strict derivation of CRBs in this paper was presented by comparing with the result got from approximate process.
2017, 46(7): 706003.
doi: 10.3788/IRLA201746.0706003
In laser fuze, target detection and recognition by pulse laser is a key technical point in laser fuze short -range detection technology, and the influence of the target's surface scattering properties on detection is a major research key in efficient damage and precise strike on targets through laser short-range detection. The target's surface roughness and the attachment largely influence the strength of laser echo signal. Therefore, it is necessary to study the scattering properties shown by target surfaces with different roughness during laser short -range detection. Firstly, echo signal model was obtained through simulation, and then echo power experiment on surfaces with different roughness was carried out to verify the simulation results. In the experiment, target plates with different surface roughness were used, and methods such as changing the angle, changing the distance, etc., were adopted to observe the voltage curve, thereby obtaining the final result.
2017, 46(7): 706004.
doi: 10.3788/IRLA201746.0706004
The power and energy are very high, as a result, laser energy meters are easily damaged and measurement uncertainties are increased. The domestic and overseas methods to directly measure high energy laser(HEL) energy were compared and summed up, and the benefit and the drawback of the technologies were thoroughly analyzed, finally, the development trends of the technologies to directly measure HEL energy were expatiated. The research shows that it's the most effective measures to improve the measurement capacities to increase heat exchange efficiency, and especially when the body-absorbing model and the compelling heat exchange model were adopted, these effects are better; it's the key to improve the measurement accuracy of passive-absorbing-type HEL energy meter to eliminate the effects of temperature gradent in the absorber on specific heat of material and response time of temperature sensors; while it's the key to improve the measurement accuracy of water-absorbing-type HEL energy meter to eliminate the effects of phase change of water, and uneven of water temperature. Nowadays all kinds of higher heat exchange efficiency and new mechanism methods are quickly developing and applied, as a result, the measurement capacities and measurement accuracy are improved, and the energy-accumulating-type energy meters are replaced by power-equilibrium-type energy meter to adapt to longer duration of lasers in the future.
2017, 46(7): 706005.
doi: 10.3788/IRLA201746.0706005
A novel measurement method for the dynamic characteristic of ring laser gyroscope was proposed, based on a new laser Doppler vibrometer. The research on the dynamic characteristic of Ring Laser Gyroscope as a contacting system has important implications. A PZT angular vibration table was used to generate sine angular vibration, and the related measurement of the Ring Laser Gyroscope and the laser Doppler vibrometer were compared. The related experiments were conducted. Experimental results show that the property of transfer function of mechanism is a major factor affecting Ring Laser Gyroscope measure distortion under high frequency. The measurement of Ring Laser Gyroscope is accurate under low frequency and the amplitude frequency curve has been taken.
According to demand on the micro radian order angle of divergence of 3D-imaging multi-beam lidar and high registration precision of multi-element parallel condition, the receiving-transmitting registration technology was studied and verified. A receiving-transmitting registration method of multi-beam lidar was proposed, a receiving-transmitting optical system with high precision was realized by using separated receiving and transmitting optical system based on fiber optics. Element divergent angle of transmitting laser was 20rad which approached the diffraction limit, receiving field of view was 60rad, 51 elements linear parallel receiving-transmitting were realized at near infrared 1 064 nm wavelength. Meantime, the precision of receiving-transmitting registration was under 10rad. Experimental verification result indicates that the receiving-transmitting registration method is feasible. Registration precision reaches theory demand. Through temperature analysis, the optical system has good stability during a reasonable temperature range, which can satisfy the engineering application requirements of the 3D-imaging lidar system.
2017, 46(7): 730002.
doi: 10.3788/IRLA201746.0730002
Interferometric lidar is a device to achieve high precision distance detection by phase estimation. The phase sensitivity of the traditional interferometric lidar is limited by the standard quantum limit, this affecting the precision of ranging. In order to further break the limit and improve the system precision, a scheme of super-sensitivity interferometric quantum lidar with squeezed-vacuum injection was put forward, thus phase sensitivity breaking through the standard quantum limit. And the phase sensitivity of the system was derived with Z detection, intensity difference detection and parity detection method. Then, the ascension of performance was compared and analyzed by simulation calculation. Finally, on the basis of best detection method-parity detection, a phase sensitivity model with transmission loss was establised, and the maximum transmission loss allowed by super-sensitivity was discussed.
2017, 46(7): 730003.
doi: 10.3788/IRLA201746.0730003
In order to study the distributed situation of the middle atmosphere, a self-developed Rayleigh scattering lidar used to remote sensing in the altitude range 25-40 km was introduced, which was located at Hefei(31.90 N; 117.170 E), China. Rayleigh scattering lidar with 532 nm wavelength made the measurements of atmospheric density and temperature. The results obtained by Rayleigh scattering lidar were compared with the data provided by NRLMSISE-00 Atmosphere Model to prove the Rayleigh scattering lidar system performance and the reliability of the data processing method. Through comparison and analysis of the result data, it can be found that the density ratio of Rayleigh scattering lidar to NRLMSISE-00 Atmosphere Model is from 0.99 to 1.03, and the temperature biases between Rayleigh scattering lidar and NRLMSISE-00 Atmosphere Model are about 2.8 K from 25 km to 40 km. Especially under the altitude 38 km, the temperature biases is about 1.6 K. These results indicate that atmospheric density and temperature profiles obtained by Rayleigh lidar show the coincident distribution with the data of NRLMSISE-00 Atmosphere Model over the altitudes of 25 km to 40 km, and the Rayleigh scattering lidar can represent the distribution of the atmospheric density and temperature between the altitude 25 km and 40 km over Hefei.
2017, 46(7): 705001.
doi: 10.3788/IRLA201746.0705001
In order to overcome the defect that the energy distribution is non-uniform and the shape of the spot does not match with the PV cells in the laser wireless power transmission receiving system, a trapezoid secondary concentrator was designed and processed. Based on edge ray principle, the design method of trapezoid secondary concentrator was analyzed and simulated by Tracepro software. And a trapezoid secondary concentrator was processed by four right angled trapezoid mirrors. Then the effect of the trapezoid secondary concentrator was studied through laser wireless power transmission system. The photoelectric conversion efficiency of PV cells under Fresnel lens single concentrator and combining with the trapezoid secondary concentrator was compared. Experimental results indicate that the value of photoelectric conversion efficiency of united concentrators was improved about 6%-7% compared with Fresnel lens single concentrator under the same received power of PV cells. If adding the loss of the secondary concentrator, the value of photoelectric conversion efficiency of united concentrators was improved about 2%-3%. It indicates that the trapezoid secondary concentrator could enhance the performance of laser wireless power transmission receiving system.
2017, 46(7): 705002.
doi: 10.3788/IRLA201746.0705002
A tunable acousto-optic Q-switched CO2 laser was presented using a blazed grating. The tuning principle of CO2 laser was analyzed, and it was found that changing the intra-cavity loss of lines is an effective way to realize the laser wavelength tuning. Then the relationship between diffraction efficiency of blazed grating and the laser wavelength were researched. The theoretical calculations show that the grating has highest diffraction efficiency when the auto-collimating angle of laser line equals to blaze angle of grating. Two blazed gratings with blaze angle of 31.97 (blaze wavelength 10.59 m) and 28.71(blaze wavelength 9.60 m) were employed and the tuning performances of acousto-optic Q-switched CO2 laser were researched on experiments. Laser emission lines of 65 and 75 were obtained separately. The emission lines were richer when blaze wavelength of grating equals to the laser wavelength with lower gain, which accorded with the theoretical calculations. When the repetition frequency is 1 kHz, the maximum average power of 4.2 W, pulse width of 160 ns, peak power of 26.25 kW are achieved at the wavelength of 10.59 m, showing good stability.
2017, 46(7): 704001.
doi: 10.3788/IRLA201746.0704001
The main radiation gas components are completely different in different propellant rocket engine exhaust plume, the gas spectral parameter database need to be built to quickly and accurately solve the infrared radiation characteristics of different propellant rocket exhaust plume using the spectral band model. A method of constructing the gas spectral parameter database and the program were proposed, based on the method and HITEMP2010, CO2 and H2O spectral parameter databases were establised with the wave number interval 5 cm-1 and the temperature interval 100 K; the model and the program were verified to be correct through comparing the calculated absorption coefficient distribution with the experimental measurements and comparing the calculated transmittance distribution with that calculated using the line-by-line method. Based on that, CO, OH, NO and NO2 spectral parameter databases were established based on HITEMP2010 and HITRAN 2012, and the transmittance distributions on different temperatures and different optical strokes were comparatively analyzed combined with the line-by-line method.
2017, 46(7): 704002.
doi: 10.3788/IRLA201746.0704002
The InAlSb/InSb material of p-i-n structure was grown by Molecular Beam Epitaxy(MBE) on(100) InSb substrate. The current suppression effect of the barrier layer on the dark current was verified by growing a barrier layer with a wide gap between the absorber layer and the contact layer. The electrical properties of photodiode fabricated by InAlSb epitaxial material were compared with that of traditional InSb bulk material. When the external bias voltage is -0.1 V, the reverse bias current of p+-p+-n--n+ InAlSb device and p+-n--n+ InAlSb device is 3.410-6 Acm-2 and 7.810-6 Acm-2 at 77 K, respectively. The p+-p+-n--n+ InAlSb device suppresses the dark current at a very low level. It provides an important foundation for improving operating temperature of the infrared detector.
On the basis of the heat transfer, a one-dimensional heat conduction model was proposed. The quantitative relationship among the thickness of coating, thermal diffusivity, the slope and intercept of the surface temperature difference-frames line was established. The thermal barrier coating specimens with different thickness were used. Transmission infrared thermal wave method excited by pulse laser was adopted and thermal imager was used to collect coating surface temperature-frames curve fitting. The slope and intercept of the temperature difference-frames line were obtained by linear fitting and the thickness of coating was calculated finally. The results show that it is fairly feasible to utilize laser transmission infrared thermal wave method in rapid, non-contact and accurate measurement of thermal barrier coating thickness.
2017, 46(7): 704004.
doi: 10.3788/IRLA201746.0704004
Ultrasonic infrared lock-in thermography is a novel nondestructive testing technology, which mainly combines the modulated excitation and lock-in technology to achieve infrared thermography test. With the lack of study on the frictional heating simulation and interior heating mechanism during the defect heating and diffusion, the electric-force analogy method was utilized to build the finite element model of the ultrasonic transducer and the metal plate with the fatigue crack. Simulation results show that the crack heating periodically increases with the modulated ultrasonic excitation, and the heating area of crack faces is closed to the excitation side by the influence of the engagement force. Based on the simulation results and the Green function, a theoretic model was introduced to describe the heat diffusion of the crack frictional heating and the heat distribution of the crack vicinity was demonstrated. Further,the depth of the heat source was estimated with the ratio between top and lower surface of the test plate(P-value), which shows consistency between simulation and theoretic results. This study aims to enrich the theoretic basis in ultrasonic infrared lock-in thermography.
2017, 46(7): 712001.
doi: 10.3788/IRLA201746.0712001
Constructing the theory and simulation for multilayer phase screen of underwater turbulence were the main problems of the research for underwater turbulence. Considering the statistical property of underwater turbulence, here 3D covariance matrix was used to model the statistical property and continuity of underwater turbulence. Here overlapping allocation matrix was put forward and the simulation of multilayer phase screen was optimized. Furthermore, the relation between computational efficiency and the characterization of statistical property of underwater turbulence was analyzed. The results show that overlapping allocation matrix can improve the computational efficiency for a layer of phase screen. Also utilizing 3D covariance matrix could obtain the correlation of phase screens, which is in conformity with theory for statistical property in a layer. However, utilizing 3D covariance matrix led to deviation in small scale and large scale. This research expends original independent 2D phase screen into the multilayer phase screen which has spatial correlation. And that is why this model is more correspond to the reality of underwater turbulence.
2017, 46(7): 712002.
doi: 10.3788/IRLA201746.0712002
In order to accomplish the high temporal-spatial resolution and continuous measurement of the ocean temperature-depth profile, a new measurement system of combining ship towing application and optical fiber sensing technology was developed. The fiber Bragg grating (FBG) pressure sensors were integrated into the temperature drag chain for the first time, so as to obtain the depth information and judge the drag chain attitude. The development of the towing temperature-depth chain system and the situation of the sea trial were introduced, including the system equipment and the laboratory calibration results of pressure sensor before sea trial and static and dynamic test of pressure sensor at sea. The correlation coefficient of pressure sensor and ALEC Compact-TD reaches 0.999 837 and the measurement error was less than 0.1 m by analyzing the test data, which further verifies that the towing temperature-depth chain system has been initially available.
2017, 46(7): 722001.
doi: 10.3788/IRLA201746.0722001
In order to meet the urgent needs of online metrology of the ultra-high current in the field of industry, national defense and key scientific research, a value transfer method of the ultra-high current standard based on the range self-expansion characteristic of the fiber-optic current sensor (FOCS) was presented. The mathematical model of the sensing coil was established by utilizing the differential Jones matrix methods. The effect mechanism of the linear birefringence on the range self-expansion characteristic of the sensor was analyzed, and the excellent range self-expansion capability of the FOCS with a spun high-birefringence sensing fiber coil was proved. By means of the magnification effect of the number of fiber loops to the Faraday effect, the sensor can be calibrated with the relatively low equivalent ampere-turn current. The flexible interferometer-type FOCS utilizing the digital closed-loop signal-detecting scheme was developed. The spun high birefringence optical fiber was packaged into a sensing element, which can be bent into a sensing coil without opening the current-carrying bus bar. It is shown by the experimental results that the sensor achieves the accuracy within 0.1% for the DC equivalent current between 10 kA and 210 kA. For a power-frequency equivalent current of 25 kA, the scale factor error of the sensor can meet the need of 0.2S accuracy class specified in IEC 60044-8. The bandwidth of the sensor is more than 10 kHz.
2017, 46(7): 722002.
doi: 10.3788/IRLA201746.0722002
Negative pressure wave signal caused by pipeline leakage and attenuation along the pipe was relative to pipe length, working condition and leaking hole diameter. In order to solve the problems of low precision and poor reliability in traditional monitoring methods, a negative pressure wave-based pipeline leak monitoring method using optical fiber pressure sensors was proposed. According to the propagation law of negative pressure wave in the pipeline, by increasing the density of sensors along the pipeline, the signal attenuation would be reduced, and a clearer negative pressure wave falling inflection information could be acquired. According to the leak difference in sensor section, a new adaptive method based on leaking distance was proposed for calculating the velocity of negative pressure wave. Finally, the optical fiber and traditional negative pressure wave leakage monitoring methods were analyzed respectively, experimental results showed that the leakage location error of fiber optic monitoring method was less than 1.6% when the leakage was 5% of the total pipeline transportation. Compared with traditional monitoring method, fiber optic monitoring method could obtain higher sensitivity and positioning accuracy, has more broad application prospects.
2017, 46(7): 722003.
doi: 10.3788/IRLA201746.0722003
The intensity and phase of the beam propagated in the atmospheric turbulence were modulated by the effects of atmospheric turbulence, and then the speckle was formed in the far field. The partially coherent Gaussian-Schell Model (GSM) beam was taken as the research object. According to the generalized Huygens-Fresnel principle and the mode of the modified Von Karman spectrum, the expressions of the effective radius and the mean speckle radius of receiver beam were derived. The expressions were used to analyze the effects of the beam source parameters and atmospheric turbulence on the effective radius and the mean speckle radius. The numerical results show that the greater the waist radius of the beam source, the smaller the coherent length is, the smaller the wavelength is, and then the smaller the effects of atmospheric turbulence on the effective radius and the mean speckle radius of receiver beam are. The smaller refractive-index structure constant, the greater the beam spread and the smaller the mean speckle radius is. The effective radius and the mean speckle radius of receiver beam decrease with increasing inner-scale of turbulence, but have nearly no change with increasing outer-scale of turbulence. An important reference value will be provided for the design of the Acquisition, Tracking and Pointing (ATP) in atmospheric laser communication system.
2017, 46(7): 722004.
doi: 10.3788/IRLA201746.0722004
There are some inevitable problems such as vibration, instable connection between the optical elements, hot expansion and cold contraction in the practical application of optical voltage transducer (OVT) based on Pockels effect. These factors cause the deviation between the optical elements, which affects the internal electric field distribution in the electro-optic crystal. The OVT based on convergent polarized light interference was adopted as an example. The simulation analysis and experimental research show that when the incident light has a 0.5 deviation or the BGO crystal has a 1 deviation, it leads to electric field integral errors of about 0.107% or 0.124%, respectively. As the OVT needs to guarantee the accuracy of 0.2%, the effect induced by the electric field integral errors cannot be ignored. Therefore, a new method of medium enwrapping was proposed and the alumina ceramic was selected as the medium to wrap out of the electro-optic crystal. So that the maximum electric field integral errors can be reduced to 0.001% or 0.003% respectively. The experimental result and its applications show that the medium enwrapping method is simple, practical and effective.
2017, 46(7): 718001.
doi: 10.3788/IRLA201746.0718001
The compliance of the tangent bipod kinematic mount was investigated in order to realize the design of high precision kinematic mount. The design principle of the tangent bipod kinematic mount was introduced in detail. The equivalent compliances Cx, Cy and Cz of the bipod in the X-axis, Y-axis, and Z-axis directions were deduced based on the compliance equations of the single-axis right circular flexure hinge. The compliance equations of bipod were verified by the finite elements and experiments. The results show that the theoretical results are in agreement with the finite element results and experimental results, and the deviation is less than 9.8%. The influence of the flexible groove depth R and minimum thickness t on the compliances of the bipod was analyzed. It was concluded that the equivalent compliances Cx, Cy and Cz of the tangent bipod were proportional to the flexible groove depth R and inversely proportional to the minimum thickness t. It provides a theoretical reference for the design of tangent bipod kinematic mount which is widely used to support scientific instruments in space camera.
The probe of the X-ray polarization in high-energy astrophysics has been a research focus over the past 40 years, and it has been an efficient way to reveal matters' behaviors under circumstances of extreme magnetic and gravitational fields, and to understand the causation of polarization. The small-scale soft X-ray polarization telescope usually focus soft X-ray into the detection zone, and the surface type of the telescope is paraboloid. The mirror of the telescope is deposed with multilayer, it can reflect soft X-ray with a rather high reflectivity and a high energy resolution, which satisfies the Bragg condition. Here, two kinds of design configurations for a soft X-ray polarimetry mission based on paraboloidal surface shape were presented. Some calculations and analyses were done under the limitation of a specific size of the whole system. The relation was summarized between collected area, the complexity of the fabrication, and other practical application factors. The result of the optimization demonstrates that the optimized choice for the design can guarantee the practical utilization in reality.
2017, 46(7): 718003.
doi: 10.3788/IRLA201746.0718003
A lightweight and optimization design method for a medium aperture rectangular mirror supported in centre was proposed to meet the requirement of designing lighter and better satellite cameras. By choosing the method of rear support in centre by single point, the mass of both mirror and subassembly was decreased and the design of the support structure was simplified. By using multi-objective optimization design, the surface figure accuracy under the load case of gravity in Z-direction was improved. A flexible support structure dedicated to the mirror supported in centre was designed to overcome its shortcomings of low stiffness and low dynamic reliability. The integrated performance of the mirror was simulated and compared with that of the mirror mounted via rear three points. It shows that the mirror supported in centre has a lighter mass of 3.36 kg and the lightweight ratio is 87% compared with the solid mirror, and that the mass of the mirror subassembly is decreased 24% of the one supported by three points. The surface figure accuracy RMS of the mirror reaches respectively 2.2, 2.1 and 7.5 nm when gravity load is applied in the directions of X, Y and Z axes, which is better than that of the one supported by three points. Furthermore, the RMS is 2.8 nm when the mirror subassembly is under the load condition of uniform temperature rise of 4℃, which is far less than the requirement of RMS 12 nm. Otherwise, the first order natural frequency of the mirror subassembly is 135 Hz, and the maximum rigid body displacement is 3.96m. The proposed design method not only reduces the mass of the mirror with its support structure extremely, but also ensures the surface figure accuracy of the mirror and the dynamic and static rigid of the mirror subassembly requirement, provides a new approach to lightweight and optimization design for the same type space mirrors.
2017, 46(7): 718004.
doi: 10.3788/IRLA201746.0718004
According to the high thickness and low illuminance uniformity of traditional direct-down type LED panel light, a design of direct-down type LED panel light with the curved surface plate was proposed. Some experiments were designed by applying the Taguchi method and simulated via the TracePro software. After that, the ANOVA theory was integrated to evaluate the influence of the control factors on the illumination, so that the control factors can be optimized efficiently, and the simulation results were verified by experiments. The results show that the arrangement of LEDs has most influence on the uniformity of illumination and the average illumination, which account for 47.4% and 50.2% respectively. When the optimized parameters were set as hexagonal chips arrangement, inclination angle was 30, there was no microstructure and light mixing distance was 25 mm, the uniformity of illumination on the diffusion plate was 88.3%, which were consistent with the experimental results, and the thickness of panel light was reduced by more than 37.5% compared with the current one. After simulating the illumination of conference room, the results completely conform to the national building lighting standards. This paper provides a theoretical basis to design a direct-down type LED panel light.
2017, 46(7): 718005.
doi: 10.3788/IRLA201746.0718005
The design goal of the large-diameter reflector used in the space remote sensor is high specific stiffness. In order to limit the launch costs, reduce the mass of reflector as far as possible and ensure the function requirements of the reflector, improve the structure stiffness of the reflector itself as much as possible, the reflector lightweight design is more important along with the rise of the reflector aperture. In this paper, aimed at the lightweight design of some Ф2 m-level space-based large-diameter reflector, the integrated optimization design method, which was a combining method with the traditional experience design, the topology optimization design and the size parameter optimization design, was applied. Compared with traditional optimization design method of the large-diameter reflector, it can make the design result fast converge, getting the optimal design structure. The mass of the Ф2 m reflector designed with the integrated optimization design method was 326 kg, the lightweight rate of the Ф2 m reflector was as high as 82.5%, the shape error variation RMS of the reflector which characterized the image quality of reflector and depended on the reflector stiffness was 4.9 nm when the reflector optical axis was vertical and the gravity load of 1 g was applied, and 4.3 nm when the reflector optical axis was horizontal and the gravity load of 1 g was applied. The results show that the mass of the reflector is smaller than the design requirement of 340 kg, and that the shape error variation RMS is better than the design requirement of 5 nm, satisfying the requirement of the high specific stiffness of the reflector.
2017, 46(7): 718006.
doi: 10.3788/IRLA201746.0718006
To meet the requirements of femtosecond laser micro-nanofabrication systems for high precision and wide region, the features and design specifications of infinity microscope objectives which were important components of the systems were determined. Based on the theory of primary aberration of thin lens system, the conditions to meet were concluded to correct Petzval curvature and second order spectrum for femtosecond wavelength. The objective consisted of 11 spherical lens, and all materials were glass made in China, and the use of cemented lens composed of three lens was avoided. A near infrared flat-field microscope objective, whose working wavelength was 785-815 nm, numerical aperture was 0.9, field of view in image space was 22.5 mm, magnification was 40, was designed. Designing results show that the objective has excellent MTF, RMS wavefront errors of all fields are less than 0.08, and various geometrical aberrations are deeply under tolerances, the results meet the conditions of flat field and apochromatism, and energy concentration is high. Compensators are used to slacken material tolerance, manufacturing tolerances and alignment tolerances. RMS wavefront errors of all fields get less than 0.09 after tolerances attribution and the objective can be applied actually.
2017, 46(7): 717001.
doi: 10.3788/IRLA201746.0717001
A new method and a Fizeau type interference system were introduced in this paper, cylindrical coordinates and cartesian coordinates can be mutual transformation, through a high precision 90℃onical reflector. This system was suitable for the test of 360rotatory cylindrical surface, and the whole surface information can be achieved with one measurement without stitching. The error correction matrix was established in cylindrical coordinates, after analyzing the main component system errors, and simulating their effect with Matlab. A metal ring was tested to prove the feasibility and validity of this method and system. The principal error correction result was consistent with the measurement result by Taylor Hobson, and it was very close to the roundness value, which was calculated through the least square circle (LSC) assessment method. The experimental results show that:this method and system can realized the 360℃ylindrical surface measurement, and the problems of rotary elements testing, low efficiency will be solved.
2017, 46(7): 717002.
doi: 10.3788/IRLA201746.0717002
Infrared extra-large radiation area blackbody was used to simulate certain infrared characteristic target, widely used in different infrared detection, controlling and guiding equipment's field test. With the aperture of the IR imager used in space becoming larger, the area of the area blackbody was also becoming larger. Extra-large radiation area blackbody must be calibrated in vacuum cryogenic environment, for its performances satisfy the need of test. But there is still no measurement standard at home, it can not guarantee the accuracy and reliability of test results. A calibration device for infrared extra-large radiation area blackbody was presented in this paper, the calibration for emissivity, radiation temperature, uniformity of temperature field and stability of radiation temperature was realized, and good results were achieved. The calibration of infrared extra-large radiation area blackbody in vacuum cryogenic environment was realized by this device.
2017, 46(7): 717003.
doi: 10.3788/IRLA201746.0717003
A white light interference system was developed with a speed-variable scanning technology to improve signal utilization precision and short measuring time for a large step structure measurement. A Fourier transform and unilateral step evaluation algorithm were performed for processing the scanning interference images. A calibrated standard step height of 9.9760.028 m was measured by the white light interference system using the speed-variable scanning method, the measuring time was 35 s, which was much shorter than a conventional measuring time of 222 s. A 10-times-repetitive-measurement shows a result of 9.971 m with a standard deviation of 0.007 m, illustrates that the system has accuracy and high-efficiency in the measurement of large step structure.
2017, 46(7): 717004.
doi: 10.3788/IRLA201746.0717004
A pixel matching method in on-line three-dimensional measurement based on normalized equiphase plane was proposed. Only one fixed sinusoidal fringe was needed to project on a measured object moving on the pipeline. While the object was coming to some positions with a certain adjacent displacement, the deformed patterns modulated by the object were captured synchronously by the CCD camera. Dealing the captured deformed patterns with FTP method, the phase information of the object in those positions could be predicted and normalized, and the normalized equiphase plane was transformed into integer as the mask to assist the pixel matching, which not only realized the one-to-one corresponding of the object, but normalization reduced the error introduced by these differences of the object's unwrapped phase in different positions caused by the object's movement, further binarization of the phase feature improved the pixel matching's speed as well. The simulation result of the peaks function object with the max height 8 mm showed the RMS was 0.021 mm. Meanwhile, as for time spent of the pixel matching, the average time spent with the proposed method was about 2 multiples faster than the method based on phase prediction. The object measurement also showed its feasibility and validity of the proposed method. The proposed method could not only guarantee the accuracy of the online 3D measurement, but improve the measurement speed apparently.
2017, 46(7): 717005.
doi: 10.3788/IRLA201746.0717005
The in-situ calibration technology of phased array radar antenna has been researched. The principle of phased array antenna in-situ calibration based on the microwave photonic technology was introduced. By taking advantage of Pockels effect of the electro-optical crystal in the optical probes erected on the phased array antenna, the optical signal reflected from the probe was modulated by the measured electromagnetic field. Then the amplitude and phase information of the measured phased array antenna units can be obtained through photoelectric conversion and coherent detection of the optical signal. Experimental results demonstrate that the measurement amplitude and phase accuracy of radiation electromagnetic field respectively reach 0.3 dB and 2. And this calibration method has the advantages of low aggressiveness, strong anti-jamming ability, small volume, etc. which can meet the practical demands of phased array antenna calibration and have very strong engineering practical value.
2017, 46(7): 717006.
doi: 10.3788/IRLA201746.0717006
A pixel frequency error compensation method of star sensor was introduced in detail, and the compensation effect was verified by the experimental data. At first, based on threshold segmentation algorithm for star extraction, the main reasons of pixel frequency error were analyzed. Then, the original point spread function of centroid location was improved and a pixel frequency error compensation method based on sub-pixel coordinates was proposed. Last, through the micro-pace experiment of star sensor, it was compared with sine curve method. Experimental results show that:in the center of the field of view, the pixel frequency error of the sampling point is reduced by 65.2% using this method, which is better than 52.7% of the sine curve method; using the error compensation formula of the field of view to compensate for the sampling point of the field of view, the pixel frequency error is reduced by 58.7%, which is better than 41.9% of the sine curve method. By the experimental results, compared with sine curve, this error correction method not only has better error compensation effect, but also has strong versatility within the field of view.
2017, 46(7): 720001.
doi: 10.3788/IRLA201746.0720001
Real-time detection and recognition of target is a hot issue in the field of interferential infrared imaging spectrometer, and the real-time spectrum recovery of the spectrometer is the prerequisite to solve the problem effectively. The interference pattern signal was obtained by using the visible light camera to simulate the interferometer, and the real-time spectrum recovery system of interferential infrared imaging spectrometer was designed by using the FPGA chip, which had high speed and large capacity. The system is mainly composed of interferogram data processing module, real-time spectrum recovery module and spectrum display module, running in line way and output the target's real-time spectrum information. It has the advantages of high speed, small size and the algorithm is easy to upgrade. The system can establish a good technical foundation for the real-time detection and recognition of the target by the spectrometer.
2017, 46(7): 720002.
doi: 10.3788/IRLA201746.0720002
Ge20As20Se15Te45 chalcogenide glass was prepared by a melt-quenching method. Testing results show that this glass posses high nonlinear characteristics and wide infrared transmission windows in the infrared region. The third-order nonlinear coefficient was tested to be n2=6.7210-18 m2/W@4 m by a Z-scan technique. Two kinds of chalcogenide glass infrared fiber grating optical switches were designed with this glass. The reflection spectrum and grating wavelength shift of optical switches were calculated with the distributed time-domain transfer matrix method (TD-TMM) and non-linear coupling equations. Results show that the Bragg wavelength can be flexibly tuned by modulating the input intensity and optical switch can be achieved. It was found that the power threshold is about 1.6 GW/cm2 for an optical switch with a modulation depth of 110-3 in a uniform chalcogenide Bragg fiber grating and the power threshold can be significantly reduced to about 210 MW/cm2 in a phase-shift chalcogenide fiber grating with a modulation depth of only 310-4.
2017, 46(7): 720003.
doi: 10.3788/IRLA201746.0720003
The coupled structure of metal nanoparticles and metal film has more superior physical properties than unit structure. In order to provide theoretical basis for experimental study on the application of silver nanocube coupled with silver film in sensing, the electric properties of the coupled system were analyzed using FDTD excited at the wavelength of 514.5 nm. The results show that the electric field distribution of the coupled structure of silver nanocube and silver film was affected by the size of silver nanocube and the thickness of the dielectric spacer between silver nanocube and silver film. The local electric field of the coupled structure was stronger than that of unit of silver nanocube. When there was no dielectric spacer, the local electric field was mainly localized on the upper surface of the silver nanocube for the coupled structure. When there was dielectric spacer, the local electric field would be partially localized in the dielectric spacer. Therefore, the ideal local electric field can be obtained by adjusting the size of silver nanocube or the thickness of spacer between silver nanocube and silver film for requirement.
At a single snapshot without any mechanical movement, real-time compact multispectral imaging (MSI) is capable of capturing multiple 2-dimensional (XY) images that are corresponding to different characteristic spectrums () of the target. Real-time compact MSI has desirable features including high efficiency, robust to vibration, and a small volume. A two-dimensional narrow band multichannel micro-filter array (2DNBMFA) is an essential part to apply real-time compact MSI to in-vivo optical pathological diagnostic fluorescent imaging, and ultimately result in a real-time compact multispectral fluorescent imaging technology (MSFI). Firstly, the structural pattern was designed and the important technical parameters of the 2DNBMFA were determined, which was the key element to be used in the real-time compact MSFI. Secondly, the 2DNBMFA was manufactured which had a 2-dimensional spatial resolution and a high optical density. Experimental results indicate that the developed micro-filter array has a spatial resolution of 52 m52 m, full-width at half-maximum of 24 nm, optical density of 4, weak cross-talk between different optical channels. All these suggest that the real-time compact MSFI technology is technically feasible, which has the potential to capture the 2-dimensinal distribution of multiple fluorescent probes at any instant time. The real-time compact MSFI, if successfully be developed, would have great significance in medical in-vivo diagnostic imaging and in biological research area where it is hot to use multiple fluorescent probes as biological markers for a better understanding of various life processes.
2017, 46(7): 726001.
doi: 10.3788/IRLA201746.0726001
In the process of obtaining high dynamic range(HDR) image using the fusion of multiple shot images, the selection of exposure time in traditional method is blind, which makes the image information redundant and thus affects the fusion efficiency. In this paper, a method of multi-exposure control based on maximum local information entropy was proposed. The relationship between information entropy and exposure time of low dynamic scene was discussed. It was concluded that the image information entropy of a low dynamic range scene increased first and then decreased with the increase of exposure time. And information entropy achieved the maximum at a certain exposure time. For a high dynamic range scene, firstly, the range of exposure time was determined by using the approximate linear relationship between the gray level of the image and the exposure time. Secondly, the high dynamic range scene was divided into several low dynamic range(LDR) regions by using the histogram of the image. At last, the optimal exposure time of each region was searched. The method combined the local information entropy with the exposure time, which maked different exposure to different regions and avoided the shortcomings of the traditional exposure control effectively. Experimental results show that the image obtained with the proposed method has a good effect.
2017, 46(7): 726002.
doi: 10.3788/IRLA201746.0726002
How to detect infrared dim targets accurately under complex background and low SCR condition is of great significance for the development of precision guided weapons and infrared warning. In order to improve the SCR and detect the dim targets effectively, a new method for infrared dim target detection based on the gray contrast between the central region and its neighborhood was proposed. The contrast of the target was improved by calculating the contrast map and saliency map of the input image while suppressing the background clutter. The adaptive threshold was set on this basis to separate the dim targets. Experimental results show that the proposed method can achieve higher detection rate and lower false alarm rate compared with conventional LCM(Local Contrast Measure) method. The proposed method has an outperformance compared with other algorithms, especially in the case of complex background.
2017, 46(7): 729001.
doi: 10.3788/IRLA201746.0729001
The existence of space debris has been causing great threats to the security of spacecraft in orbit. Space debris will occupy the limited and precious orbit capacities, so more and more debris generated in the space will also be a huge threat. The real-time high precision orbit determination of debris based on laser ranging technology can effectively avoid the collision between the debris and the spacecraft. In order to make high precision laser ranging to small size space debris, the 53 cm diameter binocular was developed here, which was capable of fast and steady tracking space targets of 400 km above the ground. Combined with low-power high-repetition-rate sub-nanosecond laser generator and single photon detecting technology, the space debris laser ranging technique was implemented on this binocular telescope. According to the laser ranging formulas, the detecting capability of this space debris laser ranging system was researched and analyzed. When the space debris was 1 000 km away from the ground station, the minimum size of the echo photon which can be detected is about 478.5 cm. This space debris laser ranging system has been putting into observation, and the practical observation results indicate this system has the capability to detect meter level debris in ca. 1 000 km distance.
