2016 Vol. 45, No. 11
column
- Invited paper
- Laser technology
- High energy laser technology
- Laser technology and application
- Infrared technology and application
- Photoelectric measurement
- Optical design and simulation
- Laser radar technology
- Teraherta technology and application
- Optical communication and optical sensing
- Space optics
- Space debris detection
- Advanced optical imaging technology
- Information acquisition and identification
2016, 45(11): 1103001.
doi: 10.3788/IRLA201645.1103001
In order to realize the recognition and detection of remote material, a no-contact pulse gated Raman detection system was designed and established, by using the high energy density of strong pulsed laser (~106 W) enhanced the Raman scattering signal from the substances detected, a large aperture lens system was used to improve Raman light collection efficiency, while using synchronous delay system to control the open and integral time of ICCD, the background interference light and fluorescence were removed to improve the signa-t-noise ratio, thus increasing the Raman spectrum detection distance. The influence of different lens aperture was studied, the clear Raman spectra of sulfur elements and water were also obtained at a detection distance of 950 mm.
2016, 45(11): 1105001.
doi: 10.3788/IRLA201645.1105001
The investigation on 808 nm CW lase-diode pumped all soli-state linearly tunable Nd:YVO4 laser was conducted in this paper. By utilizing methods of short cavity, inclined thin etalon and frequency stabilization including gain medium temperature control, mechanical vibration damping of the laser base and aerial isolation of external turbulence and noises, single frequency laser output at 1 064 nm was achieved with a maximum output power of 140 mW. Frequency characteristics was monitored by a Fabr-Perot interferometer and beam density distribution was also scanned, beam quality M2 was measured to be about 1.05 by knife technique. Electr-optical RTP crystal was fixed in the cavity and connected to a high power source, which allowed cavity length modulation by linear electr-optical effect. During the cavity length tuning process, mode hops were avoided by the real time angle tilting of the thin etalon. Frequency tuning range of the 1 064 nm laser reaches 1.35 GHz. Programed sa-tooth with a 2 200 V amplitude was further applied on the RTP and a 20 Hz periodical linear frequency tuning laser with an average power of 85 mW was obtained.
2016, 45(11): 1105002.
doi: 10.3788/IRLA201645.1105002
A near singl-mode 1.2 kW al-fiber laser oscillator with optica-optical efficiency of 70.8% and beam quality of Mx21.03, My21.55 was reported. The laser is bidirectional pumped by laser diodes with locked wavelength of 976 nm. Therefore, the fiber laser takes on nearly linear output power versus pump power from threshold current to full current, and the instability capacity of output power is less than 2% during 8 h operation. The laser can be operated within wide temperature scope, the excellent temperature uniformity is shown on temperature cycle test.
2016, 45(11): 1105003.
doi: 10.3788/IRLA201645.1105003
Yb3+:KGd (WO4)2 crystal has been paid much attention in the recent years because of its broad gain bandwidth and high dopant concentration and it is considered as an ideal laser medium for constructing a mode-locked femtosecond or a radiatio-balanced laser system. A quas-thre-level kinetic model has been built to carry out the theoretical analyses for both the seed part and the amplification part in a Yb3+:KGd(WO4)2 laser system with en-pumped configurations. The research first investigated the physical characteristics of the seed part based on analyses of the rate equations and found that the optimal crystal length and optimal output coupler reflectivity should exist in a lasing oscillator. Because the thermal conductivity of a Yb3+:KGd (WO4)2 crystal was relatively low, the research employed a master oscillator powe-amplifier (MOPA) to realize the 30 W-output power. Finally, the output physical features of the MOPA part was analyzed. The research results are thought to be useful for construction of a practical Yb3+:KGd(WO4)2 laser system.
2016, 45(11): 1105004.
doi: 10.3788/IRLA201645.1105004
In recent years, monolithic integrated multi wavelength laser array (MLA) has become a hot research topic, as an ideal light source in the wavelength division multiplexing system. A lo-cost distribute-feedback (DFB) laser array light source module based on reconstructio-equivalen-chirp(REC) technology was demonstrated. The output of this module was amplified by Erbiu-doped fiber amplifier (EDFA) and adjusted by PID control program. The center wavelength spacing of the light source module was uniform. The average interval was 1.64 nm, and the wavelength spacing deviation was less than 0.2 nm. The total output power of the light source was more than 50 mW and the output light power change was less than 0.02 dBm.
2016, 45(11): 1105005.
doi: 10.3788/IRLA201645.1105005
For antimissile, antisatellite, or such kind of strategic defense application, laser weapon is expected to emit 100 kW power or higher level. By considering the development and its object of laser weapon, a new damnification method using mult-mode laser was presented. Using the lasers, different in wavelength, pulsed and continuous wave, frequency verified, focused on target commutatively or synchronously to get more effective result. A complex damnification model was conceived and simulated by using finite element method. A 2 kW continuous wave laser and a long pulse width laser were used in the damage comparison experiments. Both the simulation and experiments results indicate that pulsed laser is better than continuous in metal ablation, furthermore, complex laser is much better. Comparing with pulsed laser, complex laser inspires nonlinear avalanche ablation effect, which makes the ablated metal 13 times more than using pulsed laser. This nonlinear avalanche ablation effect makes a base for mult-mode coaxial combined laser weapon.
2016, 45(11): 1105006.
doi: 10.3788/IRLA201645.1105006
An i-depth study of the localization properties of a random laser cavity is equivalent to the introduction of the theoretical analysis rate equation under external optical feedback lasers designed for magnetic optical crystal isolation devices to achieve improved random lasers. Using Nd:YAG laser, experimental results demonstrate that improved laser scattering loss can be reduced to achieve directional UV laser output. Finit-difference tim-domain simulation results further show that the TE mode waveguide optical gain is approximately twice the planar waveguide, the coupled signal and pump intensity in improving the guide structure is significantly improved, and the output power results confirm the structure to reduce random laser scattering losses. Results of the application of random laser have an obvious reference value.
2016, 45(11): 1105007.
doi: 10.3788/IRLA201645.1105007
As the driving current fluctuation can affect distributed feedback (DFB) laser's emitting wavelength and optical power, a high stable DFB lasers driver was designed and developed by using hybrid digita-analog closed loop method, which was based on TMS320LF28335 core controller. In terms of hardware design, the proposed laser driver utilized operational amplifier deep feedback theory to increase the stability of the whole system (better than 410-5). In software design, Ziegle-Nichols PID algorithm was introduced to eliminate the micro deviation between the real driving current and the theory current value (less than 0.5%). Meanwhile, the driver possessed surge protection circuit when power was on/off, time delay soft start circuit and over current protection circuit, et al. Using the aforementioned driver, a driving test was performed on a DFB laser with a center wavelength of 1 742 nm. Experiments show that the stability of driving current is better than 410-5 (RMS) during long term (220 h) stability performance test, which meets the requirement of DFB laser and has good practical significance.
2016, 45(11): 1105008.
doi: 10.3788/IRLA201645.1105008
By matching the length of the OPO cavity and the fundamental laser cavity, the Q-switched mod-locking intr-cavity Optical Parametric Oscillator (OPO) was realized. The design of fundamental laser and OPO cavity proved synchronously pumping and the Q-switched mod-locking signal pulse was experimentally obtained. The signal profile, output energy and spectroscopy were also measured in experiment. It is concluded that the repetition of signal mod-locking pulse depends on the fundamental and the depth of mode lock can reach 100% with 12.8 J pump energy and 20 kHz electr-optical (EO) repetition. The output energy of signal light depends on the pump energy and EO repetition.
2016, 45(11): 1136001.
doi: 10.3788/IRLA201645.1136001
Laser plasma ignition(LPI) is viewed as a promising ignition technique for aerospace propulsion systems with its many merits over conventional ignition techniques, including easier control of the ignition position and timing, wider working condition, less electromagnetic interference, rapid response and feasibility of reliable r-ignitions, etc.. Firstly, an introduction to the technical benefits and physical processes of the LPI technique was given. Then the developments in the applications of the LPI in aerospace propulsion systems were summarized, especially the achievements that had been made in National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology. Finally, the challenges and prospects in the application of the LPI in aerospace propulsion systems were analyzed. The LPI has demonstrated great prospects in reliable r-ignition of the rocket engines fueled with no-toxic no-hypergolic propellants and scramjet engines fueled with hydrocarbon fuels. However, to facilitate the in orbit and on board applications, further progress should be made in the integrated system design of the LPI system with the propulsion systems, and in the miniaturization and engineering design of the LPI system.
2016, 45(11): 1136002.
doi: 10.3788/IRLA201645.1136002
The thermal distortions of deformable mirror with such materials as mon-crystalline silicon, silica and nucleated glass (ULE), irradiated with diod-pumped soli-state laser (DPL) were calculated and analyzed using FEA software. The results show that when the power density of input laser is 0.225 kW/cm2, and the reflectivity of the deformable mirror thin film are 99.9%, the temperature rising and thermal distortions of the deformable mirror are separately 0.804, 6.751 and 7.122℃, and 0.049 3, 0.034 8 and 0.005 4m respectivel, under the radiation time of 10 seconds. By comparison, the temperature rising of deformable mirror with mon-crystalline silicon substrate is smaller; the deformation and stress of ULE is the lowest, which would be a kind of more promising material for producing deformable mirror in future DPL laser system. In the end, some results of the long pulse laser irradiation were calculated and analysis.
2016, 45(11): 1136003.
doi: 10.3788/IRLA201645.1136003
Laser induced plasma ignition (LIPI) is a new technique for engine ignition. It is revealed that LIPI has benefits in many aspects, including reduction of erosion effects, increase of engine efficiency, shorter combustion time, more accurate location of ignition, and multipoint ignition simultaneously. Therefore it has a wide developing prospect. This paper mainly aimed at the key componen-laser source, of LIPI and made a comprehensive review for the development of the laser source and the latest achievements. Furthermore, the development prospect of this kind laser was also predicted.
2016, 45(11): 1136004.
doi: 10.3788/IRLA201645.1136004
Based on the Nonlinear Schdinger Equation(NLSE), the theoretical model of psssively mod-locked Er3+-doped fluorid fiber laser using a saturable absorber was set up, by which the mechanism of generating mi-infrared ultrashort pulse in the fiber laser was investigated. The numerical simulation focused on the evolution process of the mi-infrared ultrashort pulse in fluorine fiber laser. The impact of the Er3+:fluorine gain fiber length and the saturable absorber unsaturated loss on the generation of mod-locked pulse was analyzed in detail, and the reasonable parameter range was determined. It is found that for a given set of smal-signal gain, unsaturated loss, and net intracavity dispersion, the stable mod-locked pulses are achieved by tuning the Er3+:fluorine gain fiber length within a certain range. With increasing the Er3+:fluorine gain fiber length, the output pulse duration decreased gradually, while the increase of the spectrum width (FWHM) and the peak power are observed. Meanwhile, for a given set of Er3+:fluorine gain fiber length, net intracavity dispersion and smal-signal gain, the stable mod-locked pulses are also obtained by adjusting the saturable absorber unsaturated loss within a certain range. With the increase of the saturable absorber unsaturated loss, the output pulse duration decreases gradually, however spectral width broadens and then narrows, and peak power increases gradually.
2016, 45(11): 1106001.
doi: 10.3788/IRLA201645.1106001
In indirec-drive inertial confinement fusion facilities, aimed at the cylindrical hohlraum with two cones of laser quads and the laser quads configuration, the propagation model of laser quads in the cylindrical hohlraum was built up based on the beam smoothing schemes. On the basis, the irradiation characteristics of laser quads on vacuum cylindrical hohlraum wall were analyzed, and the laser quads arrangement was optimized preliminarily according to all the spots arrangement on hohlraum wall. Results indicate that, with the increasing of the incident angle of laser quads, the spot size of laser quads on hohlraum wall decreases, while the fractional hot spot has no significant change, and the polarization characteristics also remain almost unchanged. By further analysis of the intensity distribution and fractional hot spot of all the laser quads on hohlraum wall, it indicates that the overlap of the inner and outer cones on the hohlraum wall increases the peak intensity and raises the proportion of the hot spot in relevant area. By appropriate adjustment of the location of the focal plane and the incident angle of the inner cone laser quads, the irradiation characteristics of all the laser quads on hohlraum wall may be improved.
2016, 45(11): 1106002.
doi: 10.3788/IRLA201645.1106002
The ability of temporal pulse reshaping is an important content in high power laser facility operation and fusion ignition experiment. In order to verify reshaping effect, the diagnostic system was optimized by optical and electrical power splitting, the system detected laser pulse shapes with two hig-speed vacuum biplanar photodiodes (VPD), coupled to a fou-channels 8 GHz oscilloscope. The effective dynamic range of the diagnostic system for measurement of pulses with hig-power contrast was increased by splitting the signal from every VPD evenly into two channels of the oscilloscope with different sensitivity setting, the detected pulse from the four channels was stitched back together to form the complete pulse. The result show that the detector and oscilloscope combination has a 10% to 90% rise time of 60 ps, the diagnostic reaches 2 500:1 dynamic range for contrast ratios up to 100:1 at an within 2% uncertainty.
2016, 45(11): 1106003.
doi: 10.3788/IRLA201645.1106003
Because of the extremely high saturation gain of a diod-pumped alkali laser (DPAL), the master oscillator powe-amplifier (MOPA) system is an ideal selection to achieve powe-scaling of DPALs. In this report, a theoretical model based on the kinetic algorithm was established for construction of the 3-stage amplification configuration in which the en-pumped structures were adopted. Then the amplification factors at different temperatures were calculated when the cell lengths in the MOPA system are 3, 5, and 7 cm, respectively. According to the simulation results, a 3 c-long vapor cell was employed for the pr-amplification, a 5 c-long vapor cell was chosen for the first mai-amplification, and a 7 cm-long cell was used for the second mai-amplification. With such a designed MOPA system, the output power over 1000W for a 50mW Rb-DPAL seed light can be optained. In addition, the power of fluorescence and generated heat are evaluated for this 3-stage MOPA system. The research could provide some design schemes and theoretical methodology for realization of a powe-scaled DPAL-MOPA system.
2016, 45(11): 1106004.
doi: 10.3788/IRLA201645.1106004
The accuracy of strapdown inertial navigation system (SINS) is affected by many error parameters. So it should be calibrated and compensated before put into service. For calibrating error parameters more efficiently, a te-position systematic calibration method was designed. Firstly, through a simplified error parameter model and the equation of velocity error gradient, linear relationships between navigation errors and all error parameters were established. Secondly, because of the velocity error through designed te-position consecutive rotation plan, the data of gyros and accelerometers were used to calculate all twent-four error parameters using Kalman filtering method. In addition, this method was simple and feasible. Through the simulation, gyro bias errors are lower than 0.000 75 ()/h; accelerometer bias errors are within 5g; installation angle errors of gyros and accelerometers are better than 1.5, scale errors are better than 2 ppm, accelerometer quadratic term is better than 0.1510-6 s2/m. Through three groups of experiments, the repeatability of the method is verified, and the method is proved useful.
2016, 45(11): 1106005.
doi: 10.3788/IRLA201645.1106005
Mobile mapping technology provides an efficient means of data acquisition, which can be used in many areas such as smart city construction. It is an advantage to integrate 3D laser scanner into MMS for the feature of quick speed and high accuracy. The mounted parameter calibration of 3D laser scanner had been studied and three improvements were made on the existing calibration method. Firstly a simpler mathematical model was put forward to reduce the calculation complexity. Secondly, ma-made targets of retr-reflective material were used to improve calibration accuracy. Lastly on-station calibration scheme was adopted to improve the efficiency. According to the measured data, the calibration accuracy of the method was 6 mm, and the overall design accuracy of the system is 5 cm, so the scheme can meet the requirements of the accuracy of the vehicle system.
2016, 45(11): 1106006.
doi: 10.3788/IRLA201645.1106006
A machine vision measurement method for diameters of large rotary parts based on the intersections of laser stripes was proposed to realize o-line and no-contact measurement in industrial field. Combined with geometric constraints, feature information of measurement for diameters was constructed with hig-strength and hig-directivity lasers. Feature points for measurement were emphasized by projecting intersecting laser stripes on the surfaces of large rotary parts. A hig-precision extraction method was proposed based on the distribution character of intersections on the surfaces of large rotary parts. The space coordinates of intersections were reconstructed through calibration results and the diameters can be calculated by modeling the corresponding elliptic. Measurement experiment for diameters was carried out in a laboratory, of which the results show that the measurement error was 0.5%. It provides a reliable technology for o-line and no-contact measurement for large rotary parts.
2016, 45(11): 1106007.
doi: 10.3788/IRLA201645.1106007
When CCD was jammed by laser, the study of laser transmission was one of the most important parts for the jamming image simulation and jamming effect evaluation. The transmission of laser considering the reflection of the detection plane was studied. First, laser was focused by the lens. Because the detection plane of CCD was griddin-like structure, the focused laser reflected by the plane was modulated. According to the calculation of the laser transmission through the lens, the periodical spots appeared on the aperture plane. The simulation of the transmission proved that after the spots were reflected by the aperture plane, periodical spots image appeared on the detection plane. The experimental result was in accordance with the theory.
2016, 45(11): 1106008.
doi: 10.3788/IRLA201645.1106008
In the study of the interaction between the ultra intense laser and material, it is often focused on the needed quality light source to diagnose the dynamic material structure. In order to obtain a hig-quality X-ray source featured with high luminance, quas-monchromaticity and good contrast, the changes in the structure of matters and materials are often investigated to enhance the absorbability of the ultra intense laser energy and improve the conversion efficiency from the laser radiation to the X-ray. Based on a porous structure principle, the velvet Cu targets were developed with a diameter of 200 nm and the density ratio of 70% solids of Cu. Experiments had been carried out on XG-Ⅲ laser facility in Laser Fusion Research Center, China Academy of Engineering Physics. The laser intensities in these experiments ranged from 4.3 J to 6 J on the target surface. A singl-photo-counting X-ray CCD was used to measure K spectrum of the X-ray source. The X-ray yield was counted to achieve K peak photons of 3.6108 photonssr-1s-1 from femtosecond irradiated velvet Cu target. The K X-ray conversion efficiency (CE) reaches the maximum value 0.008 68%. Compared with the average CE of the pressed foil Cu target, that of velvet Cu increased 1.2 times. The experimental data showed that the velvet structure can effectively enhance the energy absorption of femtosecond laser and improve the conversion efficiency from the ultr-intense laser to the hot electron and X-ray.
2016, 45(11): 1106009.
doi: 10.3788/IRLA201645.1106009
In order to solve the problems when designing supe-light structure part such as needing complex design techniques, long design cycle, difficult to add skin if making it by additive manufacturing technology, based on selective laser melting technology, a method which can automatically add skinned supe-light structure to traditional metal part CAD model was put forward in this paper. Considering the selective laser melting process characteristics, through an algorithm, a skinned supe-light quas-honeycomb structure part model with a preset porosity can be automatically designed by transforming an original CAD model. And the new part model data format can direct drive a selective laser melting machine for additive manufacturing without any data format transformation. The construction and design method of the skinned supe-light structure of metal part were studied. Through process analysis, appropriate processing unit length and reasonable skin tissue of supe-light structure metal part were gotten. The above method was tested successfully on a part model with complex shape in a selective laser melting experiment. The error of porosity is 2.79%, which means that this method can accurately reduce part mass according to preset porosity value. Therefore, in this way, skinned supe-light structure part can be design automatically and quickly based on an original CAD model without supe-light structure, the burden to design this kind of parts will be greatly reduced, and the practicability of the parts made through this method will be improved greatly.
2016, 45(11): 1104001.
doi: 10.3788/IRLA201645.1104001
A method to determine the aliasing effects of infrared focal plane arrays was proposed, and specifically the aliasing value in each direction was determined based on the angular dependence of both sample transfer function and aliasing equation. The mean value as the aliasing value of the array was defined. Further, this model was used to calculate the aliasing value of the rectangular and hexagonal lattices of the same pixel, showing that the hexagonal lattice's aliasing value is higher by 4%. The equivalent bandwidth in each direction of the staring array was corrected allowing for the degradation caused by the aliasing effects. The image quality of rectangular and hexagonal lattices with aliasing effects was quantified, showing that the rectangular lattice in the sense of imag-quality is superior to the hexagonal lattice by 11%.
2016, 45(11): 1104002.
doi: 10.3788/IRLA201645.1104002
It is an important research content for analysis of space security to detect the small targets with spac-based observation platform. But it's difficult to develop a fast, robust and automatically processing algorithm for some reasons:there are too many stars which have similar appearance with targets in space image and the observation platform moves irregularly. Based on analyzing star image model, a method of space target detection was proposed by triangle matching and maximum projection. First step is the sequence images registration with feature triangle and for reducing computation, the star centroid coordinate matrix was calculated. Then the maximum projection transformation for image sequences was used for detecting the moving small targets. Finally, simulation and test demonstrate the method can achieve real time and accurate targets detection with 200 sequence images.
2016, 45(11): 1104003.
doi: 10.3788/IRLA201645.1104003
In order to solve the problem of close range image registration of mult-source image fusion system with a separate optical axis structure, a registration model of binocular imaging system was established to analyze the impact of the lens center distance on the registration accuracy. The incidence angle difference of object points to different lenses was considered in this model, which determined the registration accuracy. In this way, the relationships of registration accuracy, lens center distance and object distance were analyzed. Finally, considering the angular resolution of detectors and optical axis calibration accuracy, computational formula of the distance range of pixe-level registration of separate optical axis system was given, which could be adjusted for variable close range image registration by the initial angle of two optical axes and the pixel translation of the image. Calculation results indicate that the separate optical axis system can achieve pixe-level registration from a closest distance to infinity, when the optical axes are parallel. If the system is adjusted to register for a closer distance, the registration range will become finite. Smaller lens center distance and higher optical axis calibration accuracy will help to expand the registration range. Finally, with the calculated registration range and the measured target distance, the variable close range image registration of infrared and visible light image fusion system with separate optical axis structure has been achieved.
2016, 45(11): 1117001.
doi: 10.3788/IRLA201645.1117001
The wMPS was a 3D coordinate system based on laser scanning, which was widely applied in larg-scale metrology. The orientation parameters calibration was the critical technique of the system as it could solve the problem between the large measurement scale and high accuracy. This paper focused on a novel orientation parameter calibration method by using high precise thre-dimensional coordinate control network after the mathematic model of the system was stated. Several calibration points with known coordinates were set in the workspace to establish the precise 3D coordinate control network. After the novel model of orientation parameters calibration had been explained, both calculation method for optimization and the produce of the initial iteration value were given. As indicated by the results of the verifying experiment, the accuracy and efficiency of the orientation calibration could be distinctly improved by using the proposed method. The experimental data show that the 3D coordinate measurement error is less than 0.15 mm as a merit of the proposed method.
2016, 45(11): 1117002.
doi: 10.3788/IRLA201645.1117002
A larg-scale 3D coordinate measurement method based on orthogonal cylindrical imaging cameras was proposed. The camera was consisted of one orthogonal cylindrical imaging system and two orthogonal linear CCDs, which were used to detect the horizontal angle and vertical angle of a measurement point, respectively. One camera determined two angles, therefore, the 3D coordinate of the measurement point can be measured by the intersection of two cameras. The proposed method has prominent advantages in precise coordinate measurement and especially in dynamic positio-tracking. A flexible intrinsic parameters calibration method was used to calibrate the orthogonal cylindrical imaging cameras. After intrinsic parameters calibration, the average of angle measurement error in the horizontal and vertical direction of the camera is 1.85 and 2.16, respectively. In addition, the extrinsic parameters calibration of the two cameras is also introduced. After extrinsic parameters calibration, the coordinate measurement accuracy of the system is better than 0.52 mm. The experimental results show that the proposed 3D coordinate measurement method is valid with good measurement accuracy.
2016, 45(11): 1117003.
doi: 10.3788/IRLA201645.1117003
As the investigation deepened, it is necessary to detect the hydrogen concentration with large quantities of points, in the field of nuclear power station, aerocraft engine, gaseous fuel, et al, but the existing optical fiber hydrogen sensing systems are able to measure only one point at a time. A Wavelength Division Multiplexed (WDM) optical fiber hydrogen sensing system was proposed for the detection of mult-point hydrogen. The topology, principle and advantage of WDM optical fiber hydrogen sensing system were expatiated, and the technical feasibility of the novel system was introduced in detail. According to the analysis, a WDM optical fiber hydrogen sensing system was assembled with four measuring channels using the components well developed in the telecommunication industry, and an additional scheme was also developed for the hydrogen experiment. The results show that the novel optical fiber hydrogen sensing system is able to measure mult-point hydrogen simultaneously, and different measuring channels do not interfere with one another by measuring spectral evolvement and power of the optical signal. The performance test shows that good stability (less than 1% in an hour) and small error (less than 2%) are achieved within the measuring range from 0 to 4%. The research results will provide a valuable reference for the optical fiber hydrogen sensing system to measure the hydrogen concentration with large quantities of points.
2016, 45(11): 1117004.
doi: 10.3788/IRLA201645.1117004
Stimulated Brillouin scattering is widely used in microwave photonics frequency measurement, however systems based on stimulated Brillouin scattering have long scanning period and low response speed. To improve the scan efficiency, an improved scheme using frequency combs pump and vernier effect was studied. The improved system was analyzed and simulated, and the scanning number was reduced to 7% of the original result under 100 MHz precision and 50 GHz bandwidth. Moreover, when the precision and scanning number are fixed, the improved system has a greater bandwidth which indicates that the property of the system is greatly enhanced.
2016, 45(11): 1117005.
doi: 10.3788/IRLA201645.1117005
For the engineering problem of low efficiency of defects inspection and assessment of pipe with existing method, an i-pipe internal inspection system based on active stereo omnidirectional vision sensor(AODVS) was presented to acquire 3D coordinates of point cloud and detect the defects on the inner surface of pipes in real time. First, inner surface panoramic images and laser streak panoramic images were captured with AODVS, Inner surface images were processed as follow:unwrapping, preprocessing, feature extracting and defects classification, Laser streak images reflecting the shape of inner pipe were processed to calculate 3D coordinates of the point cloud of inner surface. Finally, the pipe's triangular grid model with real texture information was reconstructed by 3D modeling technique. Experiment results show the efficiency of proposed method to detect racial variation, holes, cracks and corrosions with high accuracy, this system provide a new online inspection approach to 3D measurement and reconstruction of industrial pipes.
2016, 45(11): 1117006.
doi: 10.3788/IRLA201645.1117006
The area built TianMa telescope (in brief, TM65 m hereafter) belongs to soft soil layer. Consequently, in order to keep the high level pointing accuracy, it is necessary to build steady foundation to support the high accurate azimuth track. Based on the closed method, the accuracy of foundation settlements and track was measured by the precise leveling survey system for total 11 times from July 2012 to July 2015. The results show that the foundation tends to even settlement and the root mean square error of the track surface is 0.47 mm. At the same time, the results also show that there are relevant between foundation settlements and track heights with variation of the azimuth angle, which illustrates that the foundation settlements directly affect on the track accuracy. In addition, the methods of experiment, simulation and theory were combined to analyze the azimuth axis errors induced by the track unevenness in the eas-west and sout-north direction. Firstly, the measured track data were linear interpolated and, at some azimuth angle, the heights of some 6 supporting points of azimuth wheels were extracted. Then, the constrained boundary conditions of height differences were applied to the finite element model. Finally, the azimuth axis tilts at different azimuth angles were obtained by simulating. Simultaneously, the track unevenness was measured by inclinometer. The relationship between the azimuth axis tilt and corresponding azimuth angle and the x and y data measured by inclinometer was established and the curve of the variation of the azimuth axis tilt with the azimuth angle was achieved. The simulation results show a good agreement with the theoretical analysis and the effect of track unevenness on the pointing accuracy is within 4 arcsec, which provides basis for the pointing model modification.
2016, 45(11): 1117007.
doi: 10.3788/IRLA201645.1117007
Based on the urgent need of calibration on hig-resolution optical load, a series of calibration device for hig-resolution optical load by spectrally tunable source were designed. The spectrally tunable source can produce any spectral display light from 300-800 nm, which is turned by spatial modulation and being at infinity, clear target. Spectrum parameter, radiation parameter, imaging performance parameter can be calibrated by the device. The calibration device's spectral radiance ranges from 5.6410-4-3.1410-1 (Wsrm-2nm-1). The calibration device's spatial resolution accuracy is 0.059 mrad. The calibration device's field of view ranges from 0 to 1 3' 30. The spectral radiance response no-uniformity is 0.39%. The basic principle, system design of the calibration device and detailed test results were introduced. Thus, the calibration device for the optical load has the advantages of arbitary spectrum modulation, scalable, high resolution.
In order to insure the accuracy in linear polarimetry, a fou-beam method was presented to calibrate the retardance of quarter wave plate. The method was based on spatial modulating optical structure, which was composed of quarter wave plate, combo birefringent wedge and polarizer. Variety of polarization measurement and polarization measuring accuracy was researched by simulation approach, when degree of circular polarization of target was changed. It was indicated that the measuring accuracy of Qi, Ui and degree of linear polarization were better than 10-3 with retardance calibration, when degree of linear and circular polarization is randomize between 0.1 to 0.2 and 0 to 0.2 respectively. Accuracy of polarization parameter measuring, except Qi, is about 14 times higher than those without retardance calibrating process.
2016, 45(11): 1117009.
doi: 10.3788/IRLA201645.1117009
Spatial heterodyne spectroscopy (SHS) is a new spectroscopic technique which applies to astrometry and atmospheric remote sensing. A method of using wavelet transform to correct the baseline was proposed to eliminate the baseline drift during its application. Through the analysis of the influences of the different wavelet functions and decomposition layers on the results of baseline correction, the original spectrum was decomposed by wavelet transforms to get detail coefficients and approximate coefficients, and set the approximate coefficients to zero, the spectrum was reconstituted to realize the baseline correction. In the end, the results were compared with the results of the threshold fitting correction. The results show that the correlation coefficient of the two methods is 0.999 9 and the results are consistent, but the method of wavelet transform is more than ten times the time of the procedure. It is proved that using wavelet transform to carry out the baseline correction of spatial heterodyne interferometry is an effective, time saving and convenient method.
2016, 45(11): 1118001.
doi: 10.3788/IRLA201645.1118001
Active constrained layer damping treatments were applied to the secondary mirror supporting structure for space telescopes in order to improve its dynamic performance. Active constrained layer damping treatments, which apply piezoelectric actuators and viscoelastic materials to flexible structures, promise to be an effective means of vibration suppression in flexible structures. A finite element model for active constrained layer damping treatments was developed and a proportional derivative control law was applied on piezoelectric ceramics. Effects of key parameters, such as viscoelastic layer thickness and control gain were investigated. It is shown that the increase of viscoelastic layer thickness and control gain could both enhance the damping capability. However, the actuation ability of piezoelectric ceramics is reduced by the viscoelastic layer. Analysis results of the telescope indicate that natural frequencies of the supporting structure decrease slightly after employing active constrained layer damping treatments. However, the frequency response at the secondary mirror is suppressed apparently and the surface accuracy is improved as well.
2016, 45(11): 1118002.
doi: 10.3788/IRLA201645.1118002
The amplitude of the output voltage signal of ring resonator which consisted of right trapezoid prisms would be modulated in the mechanical vibration. From the perspective of engineering exploration, a new symmetry structure compacted with symmetry prisms to improve the ring resonator performance was put forward and discussed in the first time. The propagation property of the laser beam and the stress distribution in prisms of those two kinds of resonators was analyzed by theoretical computation and finite element analysis method. Results show that, as for the laser resonator that wavelength is 632.8 nm, the symmetry structure has a symmetry stress distribution, and the value is much lower than that in asymmetry one in prism by 15%. Compared with the asymmetry cavity' s output energy, the deviation extent of the symmetry one decreased more than 52.63% in one excitation period. From the results of simulation, using the symmetry resonator structure could reduce the stress induced birefringence in prism and of-axis range of the laser beam trajectory in the cavity, and improve the stability of output laser intensity and output signal quality effectively. The symmetry structure provides a new way for optimization design and reduction amplitude modulation for the ring resonator.
2016, 45(11): 1118003.
doi: 10.3788/IRLA201645.1118003
A new method of the finite element cavity surface segmentation was presented to simulate the propagation of light in the cubic cavity, and the linear formula between the average reflex optical path length(Lave) and cavity length of closed cubic cavity was calculated with MATLAB. At the same time, the Lave of cubic cavities with different cavity lengths were obtained by Tunable Diode Lave Absorption Spectroscopy (TDLAS) technique. Results show that the Lave will increase linearly with the increase of cavity length. Compared with the previous theoretical values, the experimental values have a better agreement with the simulated values of the finite element cavity surface segmentation and the relative errors between simulated values are no more than 2.5%. The linear formula between the Lave and cavity length can be used to decide the cavity length and enhances the inversion accuracy of TDLAS gas measurement system based on cubic cavity.
2016, 45(11): 1118004.
doi: 10.3788/IRLA201645.1118004
Because measured objects are far away, it is difficult to establish a high accurate common measurement reference in the measurement of large spatial angle. In order to achieve the larg-scale spatial angle measurement conveniently, a novel large spatial angle measurement method based on inertial reference was proposed. Firstly, the measuring principle of large spatial angle measurement was explained in detail and the measurement system was designed. Meanwhile, the pointing uncertainty of optical axis based on the two dimensional galvanometer in measurement system was studied and the influence of different errors on optical axis pointing was analyzed. Finally, the pointing uncertainty of optical axis caused by different errors was evaluated using Monte Carlo simulation. The research can lay a foundation for error allocation and pointing accuracy evaluation of the measurement system.
2016, 45(11): 1118005.
doi: 10.3788/IRLA201645.1118005
The application and implementation of total light scattering were studied to monitor particulate matter mass concentration in large areas. By means of structural design and modern technology, it removed the influence of environment background light in the process of photoelectric conversion, in order to avoid the disturbance on the system's stability because of light source intensity's fluctuation, the light intensity feedback was applied to compensate for it. Using the multiple wavelength method, combined with the Lamber-Beer law and Mie scattering theory, it implemented particle concentration detection in wide open spaces. Compared the system's calculated results with the standard instrument, the Pearson correlation coefficient is 0.988 9, it indicates that the data has good consistency, the range can reach 0-400 mg/m3, the response time is 1 min. It provides a rapid and rea-time method to monitor particulate matter mass concentration in large areas.
2016, 45(11): 1118006.
doi: 10.3788/IRLA201645.1118006
To realize the fast, efficient alignment of of-axis thre-mirror anastigmatic (TMA) system, a computer aided alignment (CAA) method was proposed. First, the aberration characteristics in the misaligned of-axis TMA system was theoretically analyzed to determine the evaluation parameters in CAA. Second, the key alignment parameters to be adjusted were given by combining the misalignment characteristics with the actual situation of the optical assembly. Finally, the magnitudes and orientation of the alignment parameters were calculated with the measurement data and CAA model. In order to verify the method, an of-axis TMA system was aligned according to this CAA method. The wav-front error (WFE) of the center and extreme edge FOVs were measured by wav-front sensor. After only once calculation and alignment, the measured root mean square (RMS) WFEs were reduced from 0.32 to 0.067(=632.8 nm). The experiment results demonstrate that this CAA method is feasible.
2016, 45(11): 1118007.
doi: 10.3788/IRLA201645.1118007
The least square support vector machine (LSSVM) was applied for the online modeling of the deformable mirror, and it could be used to forecast the wavefront control voltage at the same time. The drift characteristic of the response matrix was analyzed in the beginning, which attribute mainly to the temperature varying and nonlinearity of the actuator, and the principle of the LSSVM and its updating mechanism were introduced in the following. The optical and electr-mechanical integrated model was built in the early stage for the study of the deformable mirror, and the LSSVM model was combined into the simulation model. When the deformable mirror run in the integrated model, the control voltages and the surface profile data were collected. The data were send to the LSSVM model for the online training and updating, and the control voltages for the following step were predicted by the LSSVM model at the same time. The deformable mirror which employing 97 actuators was taken as an example to illustrate the above processes, and the simulation results were presented in details. It could conclude that the LSSVM use for the online modeling of the control voltage of the deformable mirror is adaptive and sel-refreshing, so it could improve the control precision of the adaptive optical system.
2016, 45(11): 1130001.
doi: 10.3788/IRLA201645.1130001
The tropospheric profile of the atmospheric refractive index structure characteristic is required for several applications, including performance analyses of astronomical adaptive optics systems, astronomical site surveys, and validation of atmospheric turbulence prediction models. Based on the research of differential image motion detection principle and feasibility, a turbulence profile LiDAR for measuring range profiles of atmospheric optical turbulence was developed. Compared with traditional techniques, this system was insensitive to instrumental problems, such as defocus and vibrations. The profiles of the strength of refractive turbulence and differential image motion were measured initiatively and in real time by this system. In the field experiment, the turbulence in 200-8 000 m atmosphere was measured. The range resolution of this system is 200-1 000 m, altogether 13 measured positions. Each position observed 20 seconds and got 1 000 images with a 50 Hz frame rate ICCD camera, the differential image motion of each position calculated through those images, and retrieve the result to the strength of refractive turbulence profile. Preliminary data of this field experiment shows that the LiDAR is operating properly.
2016, 45(11): 1130002.
doi: 10.3788/IRLA201645.1130002
Research status of synthetic aperture ladar (SAL) at home and abroad was introduced. Technical system, working mode and optical system characteristics were discussed. The system scheme of spaceborne SAL for space target observation was presented, and its performance and key technology were analyzed. The result shows spaceborne SAL can achieve high-resolution imaging of remote space target with high data rate and large squint angle.
2016, 45(11): 1125001.
doi: 10.3788/IRLA201645.1125001
The range of THz frequency (0.1-10 THz) and its characteristics enable THz wave to have a higher spatial resolution and atmospheric parameter sensitivity. Moreover, the important role of THz radiation playing in the earth's radiation balance determines that THz radiation has great research value and broad application prospects in the atmospheric sounding field. The research progress of THz technology application in the atmospheric sounding field was presented, as well as the analysis of the principles, characteristics and existing problems of THz wave remote sensing for the atmospheric humidity profiles, atmospheric temperature profiles, cirrus clouds microphysical parameters and atmospheric trace gas composition. In the last section, several suggestions were put forward for THz wave atmospheric sounding technology research and the frontier and hotspot issues of the research were pointed out.
2016, 45(11): 1125002.
doi: 10.3788/IRLA201645.1125002
The relationship between THz wave and medium, as well as the transmission characteristics of THz wave are not only the basic topic in the THz technology research area, but also the critical evidence for the system designations of THz wave detection, imaging and non defective detection applications. As for the transmission problem of THz wave through medium, some models were constructed respectively for the homogenous medium and idea defective medium with the methods of system analysis, which was also motivated by the electromagnetic theory and some associated experimental results presented in some home and abroad literature references. The corresponding transmission functions were also deduced and presented. Finally, simulation experiments validated the effectiveness and reasonability of such models. The results follow the basic physical principles, and are consistent with the phenomenon observed in practical experiments. The conclusions made in this paper are meaningful for the deepened comprehension about the mechanism THz wave transmitting through medium.
2016, 45(11): 1125003.
doi: 10.3788/IRLA201645.1125003
The quiet zone of terahertz tim-domain spectroscopy experiment system was measured, which was very important for targets measurements. Experimental data had been processed with software packages of MATLAB and Origin respectively and corresponding fitting curves were gotten as a result. Relative to the travelling direction of electromagnetic wave, different fitting formulas including Gaussian were found describing the electric field intensity distribution very well in the cross section of the quiet zone transversely and vertically. However, there was fluctuation in quiet zone longitudinally. Additionally, the linear relationship between peak scattered electric field and metal sphere diameter was studied with this experiments.
The sid-vie-image methods are playing important roles in the location and alignment of birefringent axes of Polarization Maintaining (PM) fibers. However, due to be restricted by ligh-intensity distribution characteristics, almost all of the sid-vie-image methods were of low applicability. In order to improve the applicability of sid-vie-image methods, a new alignment algorithm based on the peak's sharpness degree of correlation coefficient profile was developed. Correlation coefficient profiles were acquired by calculating the correlation among ligh-intensity profiles, then the peak's sharpness degree of correlation coefficient profiles was denoted as characteristic value. Compared with traditional sid-vie-image methods, the novel method was not restricted by ligh-intensity characteristics, so it shows excellent applicability. To improve the precision of angle orientation, alignment accuracy was measured on different observation planes in a series of experiments and the observation position with high alignment precision was acquired. Finally, the alignment precision of these position was analyzed with the help of practical experiment. According to the experiment result, alignment accuracy better than 0.9 is achieved.
2016, 45(11): 1122002.
doi: 10.3788/IRLA201645.1122002
Resonator fiber optic gyro (RFOG) is a high accuracy inertial rotation sensor based on Sagnac effect. As one of reciprocity noises in RFOG, input intensity fluctuation of fiber ring resonator (FRR) would lead to detection error. Firstly, the mechanism of noise induced by FRR input intensity fluctuation was investigated. Transmission characters of FRR and demodulation output with different input intensities were researched theoretically and experimentally. The expression of detection error caused by input intensity fluctuation was derived. When rotation rate was 500 ()/s and input intensity was 0.69 mW, a variation of 0.0075mW would cause an error as large as 5.26 ()/s. Secondly, the effect of input intensity fluctuation on scale factor was studied. It was found that the linear region of demodulation curve would be distorted as input intensity fluctuation increase and scale factor nonlinearity of gyro output would deteriorate too. This work proved a reference for estimating input intensity fluctuation noise in a RFOG system.
2016, 45(11): 1122003.
doi: 10.3788/IRLA201645.1122003
In the application of coherent space optical communication, traditional lasers have the problems of wide linewidth and severe intensity noise, which tends to lead to losing lock of phase locking loop. Singl-frequency Nd:YAG no-planar ring oscillators (NPROs) were developed, with linewidth smaller than 1 kHz and relative intensity noise (RIN) lower than -150 dB/Hz. An optical phase locking loop was constructed and phase locking of two NPRO lasers was realized with -67 dBm signal laser power. The analog communication experiment was conducted at the signal frequency is 10 MHz and 1.25 GHz. When the signal light power is -60 dBm or -53 dBm, respectively, relative ideal eye diagram could be observed. In the digital communication experiment, the receiver sensitivity is -50 dBm at 2.5 Gbps transmission rate, the bit error (BER) is 3.210-6. System sensitivity of quantum limit could be approached, which is much better than that in traditional IM/DD mode. This performance is suitable for long distance, large capacity space communication.
2016, 45(11): 1113001.
doi: 10.3788/IRLA201645.1113001
Based on the structural complexity and high performance requirements of space remote sensor reflector component, the design method of space remote sensor reflector component was studied. A method which was a combining method with the experience design, the topology optimization design and the size parameter optimization design was put forward, which can make the design result fast convergence, getting the optimal design structure. A reflector component structure design of a space remote sensor was achieved with this method, by means of the finite element analysis techniques, the shape error variation RMS and PV of optical reflector component which characterized the image quality of the component were got, and dynamic simulation calculation was carried out. Finally, the correctness of the finite element analysis results and the rationality of the design were validated by environmental testing. The test results show that the RMS meet the design index under the comprehensive influence of gravity load, thermal load which is in the control range, reflector surface machining residual error and assembly error, and that the overall structure has a high enough dynamic stiffness and reasonable distribution of modal, the dynamic performance of the reflector component is good and meets the application requirement. In view of the reflector components design, this method is an effective and reliable design method.
2016, 45(11): 1113002.
doi: 10.3788/IRLA201645.1113002
Calibration method and process for spatial modulating optical structure composed of quarter wave plate, composite birefringent wedge and polarizer was studied, and the calibrating equations of spectrum and radiation were presented. Based on the polarization principle of spatial modulation, linear least square method for calibration of polarization was provided. By simulation analysis, it is indicated that calibrating accuracy of linear least square method is higher than that of standard fou-point method, the modulating coefficient deviation of linear least square method has the maximum of about 210-4, and moreover, distributes stochastically in the modulating period.
2016, 45(11): 1113003.
doi: 10.3788/IRLA201645.1113003
Aiming at problems such as complicated calibration models and trivial test progress, which are occurred during the calibration of installation error for star sensors, a novel ground calibration method of installation error based on three positions was introduced. Firstly, a mathematical model of installation error was established according to Euler transformation of coordinate systems. Secondly, a new ground calibration strategy of installation error based on three typicall-selected positions on a triaxial precise turntable was put forward. The least square method and three positions method were adopted to conduct simulation contrast experiments. Simulation results demonstrate that calibration result stability of three positions method increases by nearly 10 times than calibration result stability of least square method. Furthermore, three positions method has simplified the calibration test procedure, which has important practical reference value to improve the operational accuracy of star sensor.
2016, 45(11): 1129001.
doi: 10.3788/IRLA201645.1129001
It has been found that ballistic coefficient is a critical parameter in low Earth orbit(LEO) space debris orbit determination (OD) and orbit predication (OP) while using sparse tracking data. Ballistic coefficient of more than 2 000 space debris objects with perigee height below 850 km were estimated using the lon-archived tw-line elements (TLE) data and the drag perturbation equation of the sem-major axis of the orbit. Two applications of estimated ballistic coefficient values were discussed. In the first experiment, ballistic coefficient of 14 LEO space debris objects with high area to mass ratio(HAMR) were r-computed after TLEs of suspicious quality were removed through a TLE quality examination process in which the ballistic coefficient value was used to estimate a reasonable variation of the mean sem-major axis. Consequently, the errors of all the r-computed ballistic coefficient values were reduced. The newly estimated ballistic coefficient values were tested using a number of space debris objects with external ballistic coefficient values and agreements of about 20% were achieved. In the second experiment, ballistic coefficient of GRACE-B was used as initial value in the s-called TLE-OD/OP method. It is confirmed that the TLE-OD/OP method results have better OP accuracy than standard Simplified General Perturbations-4(SGP4).
2016, 45(11): 1124001.
doi: 10.3788/IRLA201645.1124001
The Point Spread Function (PSF) is a typical analytical method of traditional imaging. Using it for reference, the theory of Correlated Imaging(GI) was r-deduced and the PSF of Ghost Image(GI) was derived. Based on this theory, the PSF and GI formula were derived when turbulent was considered in optical paths. Finally, numerical simulation was done and the result indicates that GI process can be described by PSF properly. The variation caused by distance, source size and turbulence intensity can be quantitatively analyzed.
2016, 45(11): 1126001.
doi: 10.3788/IRLA201645.1126001
In the deep space exploration, astronomical optical autonomous navigation was used. The apparent magnitude of navigation stars for optical autonomous navigation was high. In order to obtain the clear star image, the star tracker's focal length and exposure time were long. Besides, star trackers were easily influenced by complicated motion. All these reasons resulted to the blurring and smearing star images. What was worse, it was difficult to restore the blurred star images by hardware methods. Studying the modeling method based on complicated motion was helpful to make sense the influence on the image quality which was caused by relative motion between the star tracker and the navigation star and to restore blurred star images by software methods. So that the star tracker's dynamic performance was improved. It was hard to simulate blurred star images which were caused by the complicated motion of star trackers for the lack of definite motion models. The angular motion and vibration were analyzed and an innovative method was proposed to simulate the blurred star images and then the ste-by-step simulation method was compared with the new method in this paper. The simulation results indicated that the simulation method based on the separable kernel could describe the real physical image process better than the ste-b-step method and the complicated motion had great influence on the extraction errors of star spot centroids, even leading to the failure of attitude determination of star trackers.
2016, 45(11): 1126002.
doi: 10.3788/IRLA201645.1126002
Mult-spectral true color synthesized images have the prospects of broad application in the interpretation of remote sensing image, target recognition and information processing etc. The technique of true color synthesis depends on the accuracy of the obtained tristimulus values CIE-XYZ, which is used to establish the right relationship between the system of camera's RGB and human being's visual color. So, a method of true color image synthesis based on the information of artificial target was proposed by laying the ma-made targets when the satellite passes. And, the transformation matrix between camera's RGB trichromatic system and human being's visual color system was estimated from the reflectance spectrum of ma-made targets. Eventually, the suitable true color correction model was established in the certain atmospheric conditions. Experiment of true color correction was conducted on the mult-spectral images of GF-1 satellite, and the results show that good color correction effects has been exhibited on even every image with different degrees of color's richness.
2016, 45(11): 1126003.
doi: 10.3788/IRLA201645.1126003
A method of reconfigurable parallel information processing in GNC was proposed for conflicting issues between high calculation performance and low power consumption in information processing of cubesats. An architecture of tightly coupled reconfigurable parallel processing was adopted in the method and complex algorithms which require many iterations and are not suitable for CPU operations in GNC information processing were achieved by dynamically partial reconfigurable unit of the hardware circuit (DPR). A mult-core parallel reconfigurable resource scheduling algorithm based on mutex was adopted in the method and optimized hardware acceleration of the software algorithms was completed through mult-core CPU parallel calls by DPR unit. The experimental results indicate that rea-time information processing of GNC is effectively achieved in cubesats and reduces power consumption up to 50%. The method can be widely used in the field of imformation processing for resourc-constrained satellites and possesses a great application prospect.
