2016 Vol. 45, No. 6
column
- Outstanding doctoral dissertation in optical engineering
- Invited paper
- Biological optics
- Laser technology and application
- Infrared technology and application
- Advanced optical material
- Advanced optical imaging technology
- Photoelectric measurement
- Photoelectric device and material
- Photoelectric devices and material
- Optical communication and optical sensing
- Optical design and simulation
- Ocean optics
- Photoelectric navigation and control
- Terahertz technology and application
2016, 45(6): 634001.
doi: 10.3788/IRLA201645.0634001
Metasurfaces have been one of the quickly developed cutting edge research fields with potential important applications. In this paper, our previous research achievements of Pancharatnam-Berry type metasurfaces composed of nanorods were introduced, whose phase modulation presents interesting features. Such metasurface is capable of generating dispersion-less interfactial phase discontinuities and controlling the light propagation. Several functional applications were proposed and demonstrated, including anomalous refraction, dual-polarity metalens, broadband vortex beam generator, helicity-dependent surface plasmon polariton unidirectional excitation and three-dimensional metasurface holography.
2016, 45(6): 602001.
doi: 10.3788/IRLA201645.0602001
Fluorescent microscopy (FM) is an essential means for the Life Sciences research in micro-scale. By use of these advanced techniques, the most finest structures of in vivo biological tissue could be observed, as well as the dynamics mechanism at different levels be traced in realtime. At present, 3D in vivo FM with high spatiotemporal resolution through the deep scattering tissue is full of challenges. Being experienced nearly one decade development, the Adaptive Optics methodologies have been proven to be an effective way to correct the wavefront aberrations in space-variant caused by the heterogeneous tissue. In this paper, the imaging requirements and characteristics of 3D in vivo FM were summarized firstly. Then many feasible AO applications attaching to the Confocal Microscopy, Stochastic Optical Reconstruction Microscopy, Photoactivated Localization Microscopy, Stimulated Emission Depletion Microscopy, Two-Photon/Multi-Photon Microscopy were presented, respectively. Finally, some probable research points and further trend were given.
2016, 45(6): 633001.
doi: 10.3788/IRLA201645.0633001
Polarization imaging with mueller matrix can be used to obtain the physiological information of superficial biological tissue, which has significant importance in early diagnosis and prevention of cancerous disease. However, the mueller matrix deduced by the polarization information collected from the commercial CMOS sensor directly is not correct, which limits the application of commercial micro CMOS sensor in the endoscopic imaging. The study on commercial area CMOS sensor indicates its non-linear input to output mapping relationship for sensed light intensity. Considering the inherent background noise, a calibration-based method was proposed to mapping the output of the CMOS sensor to obtain the correct polarization information for tested samples. Experiment results demonstrate that the correct mueller matrix can be deduced according to the corrected polarization information, and the error compared to the standard air mueller matrix is below 3%. The effectiveness of this method is demonstrated by the experiment implemented on silk sample. The results of the proposed method reveal the possibility to apply commercial micro CMOS sensor on the endoscopic tip for in vivo biological tissue mueller matrix measurement.
In high power excimer laser system, angular multiplexing technique is employed to achieve both high energy and narrow pulse output. In this article, angular multiplexing technique was introduced, and a multiplexing encoding method was presented. This method encoded seed beam in two steps by sequential amplitude splitting. The optical elements were arranged in rectangle arrays and piled by layers. A specific optical design was made for XeCl high power excimer laser system in this laboratory. This method of angular multiplexing encoding has advantages of compacted space, small encoding error, good compatibility with alignment and measurement, and is also easy to fabricate and assemble. This design is adopted in the system and performs well.
2016, 45(6): 606002.
doi: 10.3788/IRLA201645.0606002
The second harmonic generation(SHG) technique can effectively extend the existing laser wavelengths range. It is widely applied in atomic, molecular physics and optical physics, biomedicine and other fields. Long-term stable locking of the optical frequency doubling cavity is a significant technology for the continuous wave frequency doubling technique, which is directly related to the laser output power stability and reliability. At present, the commercial SHG lasers have off-locking phenomena at different level. In this paper, an automatic locking scheme based on analog integral scanning technique was proposed. With this technique, the system could continuously work in the absence of artificial regulation, and no additional power monitoring and scanning signals were required. The system could automatically restore the locking state after it is out of locking. As a result, the long term and stable SHG laser output is obtained.
2016, 45(6): 606003.
doi: 10.3788/IRLA201645.0606003
The semiconductor laser is widely used in industrial fields, and fiber coupling enables flexible transmission. Accordingly, a 500 W high-efficiency fiber-coupled module was designed. The technologies of beam shaping, spatial multiplexing, polarization multiplexing and fiber coupling were used to couple ten bars into a laser beam. Ten bars were collimated by fast axis collimation lens. Then the beams were transformed, and collimated by slow axis collimation optics. And then the beam were combined. All the beam were focused into a multimode fiber(400m core diameter, NA=0.22) after expanding. Experimental results show that the laser output from the module can reach to 545 W in the current of 70 A, corresponding the laser output from fiber could reach to 518 W. High coupling efficiency as 95% was obtained, electro-optic conversion efficiency is 43%, which makes a foundation for kilowatt fiber-coupling semiconductor laser.
2016, 45(6): 606004.
doi: 10.3788/IRLA201645.0606004
To study the jamming effects of laser on CMOS image sensor, jamming experiments with 632.8 nm CW laser were conducted. With the increasing of laser power, the phenomenon of instauration, saturation and full screen saturation were observed. Pixel upset effect in the maximum laser intensity site of the irradiated CMOS sensor was discovered when the intensity was greater than 1.4 W/cm2 and the full screen saturation had not appeared at this time. Even the laser intensity at the photosensitive surface was up to 95.1 W/cm2, the camera could still image normally when the laser irradiation was terminated. It indicated that the pixel upset effect was not caused by laser damage. Analysis based on the device structure, signal detection and processing of the sensor chip was then carried out. It shows that one possible reason is that the two measurements of pixel output voltage(Vsignal and Vreset) are gradually approaching to each other for the electric charges of photodiode capacitance will be quickly reduced by excessive photo-carriers, and the Vreset will be subtracted from Vsignal in correlated double sampling.
2016, 45(6): 606005.
doi: 10.3788/IRLA201645.0606005
For the purpose of effectively coping with the danger from infrared imaging guided weapons, Directional Infrared Countermeasure (DIRCM) technology is greatly developed in recent years, which has got promising to be the main trend of future Infrared Countermeasure (IRCM) technology. Focused on the research requirement for infrared image-forming system's performance on the conditon of DIRCM laser's irradiation, the whole process of DIRCM laser's interaction with atmospheric environment and infrared image-forming system, including laser's emitting, lasing atomspheric transmission, optic transmission and detector's response of the input laser into infrared image-forming system, was well investigated and modeled, upon which the simulation model of infrared image-forming system's performance under DIRCM laser's irradiation was built. Finally, the proposed calculation method and simulation model in this paper were demonstrated valid for simulating infrared image-forming system's real reaction performance to DIRCM laser's irradiation, which are able to obtain efficient simulation results not only on the DIRCM laser's infrared imaging grey level, facula appearance and grey texture, but also on the infrared image-forming system's saturation and damage effects caused by the DIRCM laser's irradiation at different situations, such as different distances, illuminations, etc. Meanwhile, above results were verified by real experiment which employed laser to irradiate real infrared thermal imaging system, the simulation data were testified close to real experiment datas, the validation of proposed method and model also gets proved. The proposed work provides foundation for further research into DIRCM's jamming performance against infrared imaging guided weapons.
2016, 45(6): 606006.
doi: 10.3788/IRLA201645.0606006
Sum-frequency term of the rate equation theory of passively Q-switched intracavity sum-frequency Raman laser was derived from the sum-frequency theory. Based on rate equations of passively Q-switched Raman laser, passively Q-switched intracavity sum-frequency laser rate equations were derived and normalized, and eight comprehensive parameters were obtained. The normalized expression of the peak power and the single pulse energy were derived. The influence of these comprehensive parameters on the peak power, the energy of single pulse and the pulse duration was observed by numerical simulation. The influences of each parameter were analyzed, and it was found that the sum-frequency factor and the normalized Raman gain coefficient need to be matched with each other to achieve the high efficiency output of the sum-frequency. Finally, the numerical simulation results of passively Q-switched intracavity sum-frequency Raman laser rate equations were compared with those of passively Q-switched intracavity frequency doubling Raman laser rate equations.
2016, 45(6): 606007.
doi: 10.3788/IRLA201645.0606007
Massive electromagnetic pulses could be generated by the interactions between intensive laser and solid targets in inertial confinement fusion (ICF), leading to the inaccuracy of experimental data and even the malfunction of diagnostic facilities. A method for diagnosing electromagnetic pulses (EMP) generated by laser illuminating solid targets was presented. A conical antenna was designed and simulated to obtain the attenuation coefficient, 3D gain and other parameters of the antenna physical model. The in situ monitoring the target process was performed to evaluate the value of electromagnetic radiation and electric voltage, by which the time-domain distribution of electromagnetic impulse was expected. The experimental results indicate that the intensity of electromagnetic radiation is related to many factors, such as the power of laser, the way of laser shooting, and angle of incidence. As for planar targets, if image and material are the same, EMP engendered by laser with different power has the similar energy spectral density (ESD) and the identical characteristic frequency. The results are expected to offer significant experiment information to study physics mechanism regarding the interactions between laser and target, which will also lay foundation for the later EMP shielding design for the important diagnostic facilities in ICF experiment.
2016, 45(6): 604001.
doi: 10.3788/IRLA201645.0604001
Due to the particular structure of interference infrared imaging spectrometer, its online nonuniformity calibration and correction is always a difficult technical problem which has not been solved in engineering. Based on the in-depth analysis of principle and structure to the space-modulated interference infrared imaging spectrometer, an effective method of online nonuniformity calibration and correction was developed for this type spectrometer. The corresponding simulation model for the algorithm was given. The simulation results had shown the correctness and validity of the algorithm, which should make it possible for the on-orbit nonuniformity calibration and correction of spaceborne interference infrared imaging spectrometer.
2016, 45(6): 604002.
doi: 10.3788/IRLA201645.0604002
Due to the particular structure of interference infrared imaging spectrometer, its online nonuniformity calibration and correction is always a difficult technical problem which has not been solved in engineering. Based on the in-depth analysis of principle and structure to the space-modulated interference infrared imaging spectrometer, an effective method of online nonuniformity calibration and correction was developed for this type spectrometer. The corresponding simulation model for the algorithm was given. The simulation results had shown the correctness and validity of the algorithm, which should make it possible for the on-orbit nonuniformity calibration and correction of spaceborne interference infrared imaging spectrometer.
2016, 45(6): 604003.
doi: 10.3788/IRLA201645.0604003
Surface plasmon polariton (SPP) are waves that propagate along the metal-dielectric interface with exponentially decaying electromagnetic fields in both sides of the media. The strip surface plasmon waveguide has long been considered a useful device to achieve highly integrated optics. Analysis of SPP excitation and propagation characteristics in the waveguide by relying on a classic model, namely, Drude was presented. This research is conducted from visible light to near infrared incident wavelength. Strip SPP metal waveguide mode field distribution was studied. Results show that when the thickness of the metal remains constant and its width increases, the electromagnetic field distribution becomes increasingly concentrated in both sides of the strips. When the width of the strip is unchanged, thickness increases and the electromagnetic field distribution becomes increasingly focused on the metal inside. A long incident wavelength means that the concentration of metal strip around the electric field is small. Long incident wavelength can also lead to inter-channel interference. That is, having a large wavelength means one must select a wide strip waveguide. This study, which is about spontaneous radiation characteristics from 840 nm to 910 nm strip waveguide, reveals that a small part of radiation is evanescent to the metal area in the surface plasmon evanescent radiation patterns. Application design and analysis indicate that complete transfer of energy only occurs once in the limited transmission distance of the strip SPP waveguide. When the wavelength is long, the concentration field is reduced and coupling is reinforced. The designed coupler can realize optical WDM in 1 310 and 1 550 nm.
2016, 45(6): 604004.
doi: 10.3788/IRLA201645.0604004
Due to fast heat conduction of metals, the thermal equilibrium state can be reached within a short period of time, which causes a significant difficulty in measuring the transition of metal models when using infrared thermal imager. To solve the problem, an alternative method was presented in this paper by CARDC (China Aerodynamics Research and Development Center) to spray the thermal-insulating coating on the surface of a metal rotor airfoil model in the 3.2 m low speed wind tunnel. Then the infrared thermal imager can be used to measure the temperature distribution, and the transition position of model can be determined through the temperature jump. Since the infrared thermal imager was usually fixed to the test section, therefore, when adjusting the angle of attack, the position of model varied in the obtained infrared images, making it inconvenient to compare the transition positions. Thus, the infrared thermal imager was fixed to the rotating platform during the experiment, to synchronize with the rotation of the model, which eliminated the position difference of model images under different angles of attack. In this way, a highly accurate transition position and a more precise mapping between the infrared thermal images and model coordinates were obtained.
2016, 45(6): 621001.
doi: 10.3788/IRLA201645.0621001
Surface antireflection properties are of great value in many fields including solar utilization, optoelectronic products, infrared sensing/imaging, stealth, aerospace technologies, etc. Here, the applications, the artificial realization routines of surface antireflection properties were summarized, as well as the state of the art in the surface antireflection structures. Currently, scientists have achieved ultra-broad-band antireflection performances through carbon nanotube coatings and silicon nanotip array structures. However, there is still much room for the improvement of the antireflection properties of metal surface micro/nano structures. Based on the next generation high power high repetition rate ultrafast laser system, the Laser Materials Processing Research Grouop in Tsinghua University has successfully fabricated diverse metal surface micro-nano structures and conducted systematic research on their antireflection properties. The average reflectance of metal surfaces in the UV-VIS, UV-NIR, UV-MIR, and UV-FIR regions are reduced down to around 2%, 6%, 5%, and 8%, respectively, exhibiting ultra-broad-band highly effective antireflection properties. Besides, these antireflection performances show little change within the incident angle range of 0-60. Further, macro-micronano-nanowire hierarchical structures are also developed, reaching an ultralow total reflectance of 0.6% at the infrared wavelength around 16-17 m and keeping steadily below 3% over a broad band of 14-18 m. The outstanding ultra-broad-band spectrum antireflection properties are anticipated to have good prospects in various applications in future.
The scattering, gradient and net forces exerted on the metallic microspheres with the thick shell were calculated and the axial trapping force exerted on the oxidized copper microspheres with a force model were analyzed for a single-beam gradient trap on a core-shell (metal/dielectric) microsphere. Unlike the case for a purely metallic Mie particle, a metallic microsphere with thick dielectric shell can be trapped easily, but not be trapped in the high intensity region of focused beam. In the experiment the copper microparticles coated with copper oxide can be trapped in the focused Gaussian beam and also transported horizontally. The optical characteristics of core-shell structured metal particles could be analyzed with the theoretical analysis and experimental results, which extend the applications of optical tweezers.
2016, 45(6): 621003.
doi: 10.3788/IRLA201645.0621003
Improving the spectral transmittance of CdS window layer used in CdTe-HgCdTe tandem solar cells has a significant impact on the effective utilization of sunlight and increases the device short-circuit current density (Jsc). Herein, the average transmittance (T) and Jsc losses of as-deposited and CdCl2 annealed CdS films prepared by chemical bath deposition (CBD), near space sublimation (CSS) and magnetron sputtering(SPUT) are studied. The results show that:in the range of 520-820 nm, the as-deposited and annealed CdS films by CBD exhibit the highest T and the lowest Jsc losses of the CdTe top cell; in the range of 820-1 150 and 520-1 150 nm, the as-deposited and annealed CdS films by SPUT exhibit the highest T and the lowest Jsc losses of the HgCdTe bottom cell and the CdTe-HgCdTe tandem solar cells. In the range of 520-820, 820-1 150 and 520-1 150 nm, the CdCl2 annealing can greatly increase T of CdS films and decrease the Jsc losses of the CdTe top cell, the HgCdTe bottom cell and the CdTe-HgCdTe tandem solar cells.
2016, 45(6): 621004.
doi: 10.3788/IRLA201645.0621004
Since plasma generated by laser ablating takes on the distribution of Gauss form, it's difficult to gain uniform films on the large substrate especially on the hemispherical substrate by the method of pulsed laser deposition technology, which badly limits the actual application of this technology. Setup that could rotate at constant velocity along with swinging at variable velocity was designed. The films could be deposited continuously on different area of hemispherical substrate by using of this setup, which made sure the uniformity of the film. And the math model for distribution of the thickness was founded. Uniform diamond-like carbon film on large hemispherical substrate with 200 mm diameter was deposited by the setup based on the model simulation. The thickness asymmetry of the film was less than 5% in the range of 80. Large area homogeneous diamond-like carbon film prepared on hemispherical substrate by pulsed laser deposition method has great application foreground in some especial flied like space detection, and this setup can extend to deposit other films.
2016, 45(6): 621005.
doi: 10.3788/IRLA201645.0621005
To improve the photoluminescence intensity of ZnO, the optical properties of ZnO/Ag structures were systematically investigated. The radio-frequency magnetron sputtering technique was adopted to deposit ZnO and Ag thin films on Si substrates. The optical properties of ZnO/Ag structures that significantly different from those of pure ZnO thin films at different sputtering time were demonstrated in detail. The photoluminescence intensity of ZnO/Ag films was carried out compared with that of the pure ZnO. The results reveal that, the photoluminescence spectra of bare ZnO film showed a weak bandgap emission at around 378 nm and a broad defect-related emission band centered at 470 nm. After adding Ag film, it resulted in an increase and decrease of the near band edge, meanwhile, the position of UV peak has as lightred-shift compared with that of pure ZnO thin film. The optical features can be influenced by the evolution of the Ag film varied with the deposition time. The reasons for the enhancement of the band edge emission which caused by the surface plasmon resonance coupling of the near band edge emission between Ag and ZnO was detailed discussed.
2016, 45(6): 624001.
doi: 10.3788/IRLA201645.0624001
Stimulated emission depletion (STED) is a kind of super resolution fluorescence microscopy imaging technology. It can break through the traditional optical diffraction limit, and make the far field optical resolution improved to less than 100 nm, which is widely used in biomedical field, and becomes one of the hotspots in optical imaging research. A STED microscope system based on ultra-continuous spectrum picoseconds pulsed white laser source was introduced, and super-resolution imaging was realized. The optimized results were discussed from the aspects of precise collimation, pulse delay and residual intensity of the STED light, therefore the best imaging effect was obtained. The experiments data of the about 25 nm diameter fluorescent microspheres imaging shows that the resolution of the system is about 60 nm, which is much higher than the diffraction limit. In addition, the system succeeds in realizing super resolution imaging of nuclear pore complexes, microtubules and microfilaments and a series of biological samples. Some obscure structures imaged in confocal microscopy can be legible in STED imaging.
2016, 45(6): 624002.
doi: 10.3788/IRLA201645.0624002
As a high-order approximation model to Radiative Transfer Equation, simplify spherical harmonic (SPN) approximation has become a hot research topic in optical molecular imaging research. However, low computational efficiency imposes restrictions on its wide applications. This paper presented a graphics processing units (GPU)-parallel accelerated strategy for solving SPN model. The proposed strategy adopted compute unified device architecture (CUDA) parallel processing architecture introduced by NVIDIA Company to build parallel acceleration of two most time-consuming modules, generation of stiffness matrix and solving linear equations. Based on the feature of CUDA, the strategy optimized the parallel computing in tasks distribution, use of memory units and data preprocessing. Simulations on phantom and digital mouse model are designed to evaluate the accelerating effect by comparing the time for system matrix generation and average time of each step iteration. Experimental results show that the overall speedup ratio is around 30 times, which exhibit the advantage and potential of the proposed strategy in optical molecular imaging.
2016, 45(6): 617001.
doi: 10.3788/IRLA201645.0617001
Digital zenith camera has high precision in astrogeodesy. Identifying the star partially and setting the approximate position are needed when using digital zenith camera to orient. The scope is around the approximate position during star identification partially. Generally, the scope is usually replaced by field of view angle of digital zenith camera. Actually, this is not correct. The scope of star identification partially was deduced based on the analysis of the field of view angle of digital zenith camera. Then, the approximate position was analyzed according to the scope. The experimental data demonstrates that the range of longitude and latitude of identified stars should be above the field of view angle of digital zenith camera. Also, the recognized star number will rise when the approximate position is close to the true position.
2016, 45(6): 617002.
doi: 10.3788/IRLA201645.0617002
Laser tracker is an important optical instrument for precise geometric coordinate measurement in large scale. Position sensitive detector (PSD) is a core miss-distance detecting sensor in laser tracking system, which achieves precise position tracking of cooperation target. The detecting precision has remarkably direct influence on the performance of tracking and measurement. Firstly, one laser tracking measurement system was presented, and the working principle of the system's tracking unit based on PSD was introduced. Then the miss-distance detecting module was designed and built based on PSD according to the actual demand. The module's signal process circuit for weak signal detection was emphatically analysed, which met the requirements of PSD driving, I/V conversion, signal amplification, analogy signal filtering, parameter matching and efficient using of AD resources simultaneously. The output signal of PSD module was acquired by a four-channel and synchronous analogy to digital converter. The signal was processed by FPGA which worked in the form of finite state machine. A composite digital filtering algorithm revised from median and mean filtering method was proposed to reduce noise interfering. Based on FPGA an extended divider was put forward to improve accuracy of measurement. Through omitting the low-order byte of the numerator of coordinate formula, one two-step operation of the divider was used to extract effective decimal places. The experimental result shows that the stability of spot position is better than 2.0 m in the square effective area 4 mm4 mm. The further tracking experiment indicates the miss-distance detection method can well meet the demand of the precise and rapid target tracking.
2016, 45(6): 617003.
doi: 10.3788/IRLA201645.0617003
In low-light imaging, range-gated imaging is an effective method to obtain the 3D information of the target. As for the static targets, the different strobe distance target image can be obtained by the target slice imaging, and then the 3D image of the target is obtained by binary algorithm or centroid algorithm. For moving targets, in the same time of slice imaging, the spatial position of the target will change. Therefore, it is necessary to register different distance image before it can get a three-dimensional image of the object. Firstly,the range-gated ICCD experimental system was bulit, and mutual information image registration algorithm based on image quality evaluation was proposed for the image target registration. Then the 3D laser image was obtained by cross-correlation algorithm and the image number of laser image was gradually reduced on the basis of ensuring accuracy. Finally, the experiment of 3D reconstruction was carried out compared with the binary algorithm and centroid algorithm. Experimental results show that mutual information registration algorithm can effectively match laser image, mutual correlation algorithm for 3D imaging accuracy is higher than the binary method and centroid method. The 3D image can be obtained by using the two images, greatly reducing the difficulty of moving targets three-dimensional imaging.
In this work, a radio over fibre link with improved receiver sensitivity was reported. The basical mechanism of this prototype was to realize optical single sideband modulation with an optimum optical carrier-to-sideband ratio(OCSR). To do this, both polarization modulation and optical interleaving technology were employed. The linearly polarized incident light was firstly oriented at an angle of (0 or 90) relative to one principal axis of the polarization modulator (PolM), which is biased by V and driven by RF signals. Then a polarizer with its polarization direction (0 or 90) relative to one principal axis of the PolM was used to linearize the polarization state. Finally, optical double sideband signal was converted to optical single sideband signal by using a standard optical interleaver. It is found the OCSR is only dependent on the values of two polarization angle, and . With careful adjustment, the OCSR can be reduced to 0 dB, which is the optimum value for a single RF tone modulation. The receiver sensitivity of the fibre link is analyzed by theory and then verified by simulation. It can be greatly improved by using this technique.
2016, 45(6): 617005.
doi: 10.3788/IRLA201645.0617005
In order to reduce the random noise of fiber optic gyroscope (FOG) and eliminate the disturbance from singular sampled signal, a robust smoothing filtering algorithm was proposed. Each sampled data of FOG were iteratively weighted by weighting function with giving outliers a low weight and allocating a relatively high weight to high quality data. Then the robustness of smoothing filter can be improved evidently. The operation speed of smoothing filtering algorithm is increased effectively by generalized cross validation (GCV) and discrete cosine transform (DCT). Simulation and practicable test results show that the proposed algorithm can restrain the interference by singular sampled signal or random noise of FOG and has better signal tracking capability.
2016, 45(6): 617006.
doi: 10.3788/IRLA201645.0617006
A 3D shape measurement method combining sinusoidal pulse width modulation fringe with phase coding fringe was proposed. Two kinds of coding fringes were projected onto the object with defocus. Using a phase-shift algorithm, the wrapped phase was obtained by the sinusoidal pulse width modulation fringe, the fringe order was got by the phase coding fringe. Then, the three-dimensional shape of the measurement object can be restored. The experimental results demonstrate that the proposed method has two merits:(1) It can decrease the measurement error because of filtering the harmonics with slight defocus;(2) It can measure the different contrast object because it is based on phase code.
2016, 45(6): 617007.
doi: 10.3788/IRLA201645.0617007
A control model identification method based on eigensystem realization algorithm (ERA), was proposed for the opto-electronic tracking turntable driven by a large power permanent magnet synchronous motor (PMSM). Firstly, the test configuration was designed based on the vector control theory of PMSM. Secondly, the frequency response function of the system was acquired through the power spectrum density function, which analyzed the sequence of the input and output data. Finally, to acquire the control model of the opto-electronic tracking turntable, the ERA was adopted to identify the Markov parameters of the control system. The experiment results demonstrate that the control model of the turntable can be identified accurately through the ERA, and the control model, which reflects the dynamics of the system better, can provide theory basis for the controller design. The results also confirm that the proposed method is practical.
For exact analysis of cooling ability of thermoelectric cooling system, accurate extraction of thermophysical parameters is of vital importance. Cooling capacity is the measure of system's cooling ability. Based on the datasheet of thermoelectric module and empirical formulas evaluating temperature-dependent parameters, performance curves assuming constant and temperature-dependent material properties were plotted respectively. The standard value of cooling capacity and performance curve were obtained with differential equations for energy conservation along the TE element. Through numerical comparison and analysis, it was found that the maximum absolute error of cooling capacity was 6 W for constant parameters estimated from the datasheet and could be minimized by applying a proper set of constant parameters. The maximum absolute error of cooling capacity was 1.5 W for temperature-dependent parameters calculated with empirical formulas. The accuracy of the numerical model assuming temperature-dependent material peoperties was confirmed and it could be used to accutately evaluate thermoelectric cooling performance.
2016, 45(6): 617009.
doi: 10.3788/IRLA201645.0617009
Studied the maximum power point tracking system, dual stage Maximum Power Point Tracking (MPPT) method of Particle Swarm Optimization (PSO) and incremental conductance algorithm was proposed. The proposed method can solve the problems of incremental conductance algorithm's worse tracking precision under large step and slower tracking speed and larger power fluctuation in the dynamic tracking process under small step tracking. The proposed method consists of two stages:the stage of optimal duty prediction and the stage of MPPT. The stage of optimal duty prediction uses improved PSO to search the working voltage and current near the maximum power point of the photovoltaic cells, next calculates the optimal duty according to the searched voltage and current. This stage can solve the problems of slower tracking speed and larger power fluctuation under small step tracking. The optimal duty is received and the system is controlled by the incremental conductance algorithm when the duty generated by the incremental conductance algorithm is closed to the optimal duty, or the optimal duty is used to control system in the stage of MPPT. Simulation results show that the proposed method can acquire faster tracking speed, have better tracking precision, and reduce the power fluctuation in the dynamic tracking process. So the proposed method can achieve the maximum power point tracking bitterly.
2016, 45(6): 617010.
doi: 10.3788/IRLA201645.0617010
In order to improve the measurement accuracy of planar sheet metal parts when the measurement scales increase, upper and lower edge distinguishing method and thickness converting model were proposed. Firstly, edge distribution characteristics of parts image which include upper edges and lower edges were proposed by analyzing the edge feature of different thickness of metal parts placed in back-lighting. Sub-pixel edges of parts were extracted by the Canny and polynomial fitting algorithm. Then, upper or lower edges were distinguished by distance-mean method. Finally, accurate edges on the calibration plane were located basing on thickness converting model. Dimensional measuring of metal part could be calculated using the calibration data. Experimental result shows that the precision of the 1-5 mm thickness and 500 mm500 mm parts in the range of 10.75 m2 is up to 0.05 mm. It can satisfy the requirement of the sheet metal cutting measurement.
2016, 45(6): 617011.
doi: 10.3788/IRLA201645.0617011
A quantitative analysis model of mine gas concentration based on improved support vector machine (SVM) was adopted. Five mine gases were used for experiment, which included methane, ethane, propane, n-butane and carbon dioxide. Mid-infrared spectral data of these five gases and mixed gases were collected with Fourier infrared spectrometer. 236 groups of these mixed gases were divided into 186 groups for calibration set and 50 groups for validation set. Principal component analysis (PCA) was used to reduce the dimensionality of the infrared spectral data, and 3 eigenvalues were extracted as input, which helped to improve convergence speed and reduce calculation time. Particle swarm optimization (PSO) and genetic algorithm (GA) were used to optimize parameters of support vector machine (SVM) method respectively, and PSO was adopted for its better optimization effect over GA. The mixed gases were detected through this algorithm, and experiment results show that the average errors of concentration predictions of five gases are all less than 1.78%, and the maximum errors of concentration predictions of five gases are all less than 4.98%. The time cost for concentration prediction is all less than 103 s for the 50 groups. This suggested that the improved SVM method based on PSO can be used to predict the gas concentration accurately, and can meet the requirement of real-time detection of mine gases, which has great value in the study of concentration prediction of mine gases.
2016, 45(6): 617012.
doi: 10.3788/IRLA201645.0617012
Regarding outfield test and calculation of the pod laser indication precision, a sine algorithm computing the deviation angle of the laser indication based on the sighting axis coordinate system was advanced in this paper. The least-square fitting of orthogonal polynomial was adopted for this algorithm to capture the pod track as well as estimating the measurement precision of the pod coordinate. Further, an error model of the laser indication precision was established and an impact factor of the error source was also calculated according to the analysis of the test error source. It indicates that the error of the sine algorithm is three digit classes lower than the cosine algorithm under a small deviation angle, and it is the best way to reduce the testing error of the laser indication precision by improving the position measurement precision of the laser spot. In addition, this algorithm reduces obviously the calculating error of the pod laser by around 2-3 digit classes, and provides an evidence for the performance demonstration of the measuring system of the laser spot.
2016, 45(6): 620001.
doi: 10.3788/IRLA201645.0620001
Fabrication of micro lens arrays has been a research hotspot in the area of micro optics. By using two X-ray moving lithography, the polymethyl methacrylate (PMMA) as the positive photoresist, the micro lens array was manufactured on PMMA plate, and its fabrication principle was described in detail. The related mask pattern for fabricating micro lens arrays was designed. Through designed mask patterns simulation, the shape of the actual micro lens could be predicted. After the first moving X-ray lithography, theoretically the semi-circular columnar micro 3D structure was formed on the PMMA substrate. If the mask mounted vertically was rotated 90 after the first X-ray lithography and the second X-ray lithography was carried out, eventually the 3030 micro lens array was obtained on the 10 mm10 mm PMMA substrate, the diameter of each micro lens was about 248 m, the depth was about 82 m. The relationships between the amount of X light exposure and the depth of PMMA etching was studied. The micro lens array profile measurement shows that the new method for the fabrication of micro lens array is proved to be feasible.
2016, 45(6): 620002.
doi: 10.3788/IRLA201645.0620002
In order to improve mems-sensor application and the characteristic of parameters, the micro-nano optical fiber ring resonator structure was designed, which was a small size, low dissipation, and high quality factor. The characteristics of micro-nano optical fiber and optical transmission mode were analyzed theoretically, through the electric field of transfer matrix, the function relationships among wavelength, perimeter, effective refractive index for micro ring resonator were obtained under the acceleration effect. The results of simulation analysis show that electric field of waveguide fluctuates significantly, and coupling efficiency of waveguide is better. Spectral intensity and 3 dB bandwidth change smaller. Q value reaches 104. When mass increases 10 g, output spectrum drifts to the right about 3 nm. Acceleration and drift quantity of resonant wavelength are almost linear. Drift of resonant wavelength can be used to measure acceleration. The results can provide variety of optical waveguide devices for all-optical networks and micro-electromechanical system.
2016, 45(6): 620003.
doi: 10.3788/IRLA201645.0620003
In the field of integrated optics, optical wavelength splitters is a key element in light signal redistribution. A optical wavelength splitter was presented for 1.31m and 1.55m wavelengths with TE mode. The device was based on the operating principle of a directional coupler in two parallel LiNbO3 photonic wire, and can be designed and simulated by finite element method. The calculated steady-state field distributions indicate that the wavelengths of 1.31m and 1.55m light waves are spatially separated. In this device, transmittances at the 1.31 and 1.55m wavelength are 91% and 86% respectively. The size of this device is only 26.2m10.1m.
2016, 45(6): 622001.
doi: 10.3788/IRLA201645.0622001
A ring cavity fiber laser based on the filter of up-tapered Mach-Zehnder interferometer (MZI) was proposed and demonstrated for displacement sensor experimentally. The up-tapered MZI was easily fabricated by using a commercial fusion splicer. The peak wavelength of the laser bule-shifted with the different bending direction by decreasing the distance between the two stages. The maximum sensitivity of 4.49 nm/mm and extinction ratio of more than 50 dB were achieved. The configuration of up-tapers were strong in strength, therefore, the bending radius of the whole fiber were almost the same. Note that this kind of configuration is easy in fabrication and low in cost which is beneficial for engineering application.
2016, 45(6): 622002.
doi: 10.3788/IRLA201645.0622002
Based on the rigorous couple-wave analysis (RCWA) method, columned antireflective microstructure on surface of Si substrate though the MATLAB software was optimized and antireflective effect combination structure parameters were obtained, and periodic two-dimensional array of cylindrical micro-structure expression was deduced, so that the reflectance of the design value was 3%. The single and double microstructure were fabricated by reactive ion etching and binary exposure technology, and its surface topography was analyzed by thermal field emission scanning electron microscopy (SEM), combined with infrared imaging spectrometer for measurement and analysis of its production structure. The results reveal that the reactive gas flow rate, Radio Frequency (RF) power and chamber pressure are critical for the morphology of the microstructure and the steepness of sidewall. The effect of profile shape of the anti-reflective properties in actual manufacturing process was discussed, and its surface topography was analyzed by thermal field emission scanning electron microscopy (JSM-7800F), combined with infrared imaging spectrometer (Spotlight 400) for measurement and analysis of its production structure. The experimental results illustrate that the double-sided columned microstructure can have excellent average anti-reflective rate preferably about 8%. Basic design reaches the design requirements.
Space-time trellis code (STTC) has the advantage of high spectrum efficiency. A STTC coding scheme was proposed for M-PSK modulated intensity modulation/direct detection (IM/DD) atmospheric optical communication system. By using the proposed mothed, the problem that conventional STTC is unable to be directly applied to IM/DD link was eliminated by employing the IFFT symmetry and a direct-current (DC) component. The system BER performance in different atmospheric scintillation and modulation index was evaluated by Monte Carlo method. Simulation results show that the proposed scheme has the advantage of mitigating the scintillation effect caused by atmosphere turbulence, and the link BER performance improves with the increase of diversity gain particularly in strong turbulence channels.
2016, 45(6): 622004.
doi: 10.3788/IRLA201645.0622004
The intrinsic linear birefringence and its temperature characteristic of the BGO crystal seriously restricts the development of optical voltage sensor, thus the study on the intrinsic linear birefringence is of great significance to improve the performance of the optical sensors. An interference fringes method employing a crystal wedge was proposed in this paper, and the measurement for the intrinsic linear birefringence of the crystal inside the sensing head can be realized by measuring the fringes' displacement. The theoretical deduction of the measuring principle was given taking Jones matrix as a mathematical tool, the application example and the verifying results were also given, which indicates that the intrinsic linear birefringence and its temperature characteristic can introduce an error of about 1% to the voltage sensor. Compared with the traditional intensity method, the measured results of this method are insensitive to the power fluctuation of light source, and there is no adjustment of any optical components during the whole experiment, so no additional error will be induced. The measurement accuracy is improved by about one order of magnitude.
In order to solve the problem of missing alarm due to the polarization induced fading (PIF) in -OTDR fiber-optic distributed disturbance sensor, a space-domain difference based location method was proposed and investigated. By determining the time-domain and space-domain thresholds, respectively, the detected optical intensity was processed by both of current time-domain and our proposed space-domain difference methods. Then, the missing alarm rate induced by PIF can be effectively reduced. The proposed location method was verified by experiment. By a long-term test in the case of space resolution of 50 m and fiber length of 25.05 km, compared with current single time-domain location method, the missing alarm rate is reduced to be 2% from 18.5%, and the accurate alarm rate is improved to be 89% from 76%. The proposed work in this paper can be the theoretical direction and technical reference for optimization and improving performances of -OTDR fiber-optic distributed disturbance sensor in practical applications.
2016, 45(6): 618001.
doi: 10.3788/IRLA201645.0618001
A pair of quadrupole lens has excellent imaging performance, electrostatic quadrupole lens can focus the electron beam into a line, quadrupole lens pairs have the ability to focus the electron beam into a point. The point-focusing property of a quadrupole lens pair was investigated in this paper, using the electron ray tracing simulation program SIMION. The simulation of electron distribution quantitatively showed that the fringing field at both ends and the aberration in the crossover image caused an electron beam blur. The aberration of a quadrupole lens pair as a function of the electron initial kinetic energy was discussed, and the result indicated that the aberration would be effectively reduced if the kinetic energy of electrons increased. 10 000 electrons were flown in a SIMION simulation and the entry angle 0 is randomly varied so that -101, the size of diffuse spot at the focal plane reduced to 3.2 m28 m as the kinetic energy of electrons increased to 1105 eV.
2016, 45(6): 618002.
doi: 10.3788/IRLA201645.0618002
Based on the 3rd vector wavefront aberration theory of axial symmetry optical system, the vector aberration expansions of off-axis optical system was obtained by pupil zoomed factorial and pupil decenter vector in this paper,. It is known through the analysis that the off-axis optical system's aberration are still composed of 3rd spherical aberration 3rd coma and 3rd astigmatism. Due to the impact of pupil zoomed factorial, the decrease of the off-axis optical system's aberration coefficients were different proportion. The higher-order pupil aberration of coaxial system will induce low-order pupil aberration into off-axis mirror system. For example, if the coaxial system is not corrected for 3rd spherical aberration, it will introduce not only the spherical but also the constant coma and astigmatism into off-axis system. The aberration of off-axis system will not be asymmetry by the field center because the induced low-order aberration, and there maybe have an aberration zero point outside the center field of the view.
High flux of cold atoms is one of the key technologies to realize high-precision cold atom interferometer. The approach of concatenation of two-dimensional Magnetic Optical Trap (2D-MOT) and three-dimensional Magnetic Optical Trap (3D-MOT) is generally used to obtain high flux of cold atoms. The magnetic field distribution of 2D-MOT is the key influencing factor in this appliance. In this paper, three different (rectangular, race-track and saddle) mathematical models of Anti-Helmholtz coils in 2D-MOT were established to analyze the magnetic field distribution. Then, the magnetic field zero drift and the change of magnetic field gradient caused by the error of eccentricity, coils asymmetry, parallelism and inside diameter asymmetry were analyzed, which were produced in the manufacture and installation process using finite element analysis. Results show that the magnetic field gradient provided by saddle coils is more conducive to produce high flux of cold atoms when eccentricity error is less than 1.14 mm, coils asymmetry error is less than 0.016 A and parallelism error is less than 1.02. This work may provide theoretical guidance for the design and fabrication of magnetic system of 2D-MOT of cold atom interferometer.
2016, 45(6): 618004.
doi: 10.3788/IRLA201645.0618004
For the measurement needs of space three-dimensional coordinates, a 3D laser radar optical system was designed. This system used the structure of transmitting/receiving common path and based on Gaussian optics theory. It can not only improve system concentricity, reduced external interference, and also simplify the system structure, reduce the volume of the instrument. The system uses expanded beam collimation structure to achieve eight times beam expander. Through small defocus, by changing the distance between 28.203-14.671 mm of the transmission optical system between a first lens and the second, it can achieve ranging accuracy 0.02 mm+10m/m when the measuring range of 2-18 m.
2016, 45(6): 618005.
doi: 10.3788/IRLA201645.0618005
Based on the consideration of the influences of decenter element to aberration, the positions of pupil center and image center as functions of lens decenter was derived and the relationships of adjustment and aberration increment was established. Then, the calibration method on lateral displacement transmission-type system based on aberration theory was advanced, which cover the shortages of calibration method based on Gauss optics. An example was also set up to prove the effectivity of this method. The result showed that the adjust programme chose by this method caused the minimum aberration increment which reduced the influence to the imaging quality. This theory could be used to instruct the calibration on misalignment system.
2016, 45(6): 612001.
doi: 10.3788/IRLA201645.0612001
Aiming at the necessity of underwater single-beam scanning detection system detecting near field target, optical parameters were optimized to suppress the backscatter by sea and improve system SNR. Blind distance formula, echo power equation of underwater target and sea backscatter were derived to analyze the relationship among detection area, system SNR and optical parameters. The optical parameters were optimizationally calculated based on particle swarm optimization (PSO) under different water qualities. The results showed that, for the system detection area was 6-10 m, when the transmitted beam was parallel to receiving field, half receiving FOV was 9 mrad, and the baseline distance was 10.6 cm, the system got the best SNR. To prove the correctness of the theoretical model, optical simulation system of underwater laser detection was designed to test system SNR under different optical parameters, the experimental result was consistent with theoretical result. The optimization results can provide theory basis for designing optical parameters of underwater single-beam scanning detection system.
2016, 45(6): 631001.
doi: 10.3788/IRLA201645.0631001
Integral proportional navigation law which can be applied to strapdown laser semi-active seeker is a kind of typical guidance law. In order to analyze the precision with this kind of guidance law, the analysis based on adjoints was put forward. Firstly, the model of integral proportion navigation guidance is constructed and the implement of the integral proportional navigation law was given. Secondly, based on the analysis of characteristic of different kind of error sources, the influence of these error sources with adjoints was got. The result shows that precision has a close correlation with navigation constant N and dynamic behavior of autopilot. These conclusions are significant for the application of the strapdown laser semi-active seeker in engineering.
2016, 45(6): 625001.
doi: 10.3788/IRLA201645.0625001
Terahertz is an emerging technology developed rapidly in the field of information science. The interaction mechanism between terahertz and material needs further exploration. Solid samples pretreatment is needed before terahertz measurement. In this paper, soil samples were selected for studying tablet-making process for terahertz time-domain spectroscopy measurement. Problems during tablet-making process were analyzed and the process was then optimized. Sample weight (130 mg, 180 mg, 220 mg, 280 mg, 330 mg, 400 mg) and the tablet-making pressure (every 0.5 t between 0.5-5 t, 1 t=1 000 kg) were selected as variables for studying the most suitable parameters for tablet-making for terahertz spectrum measurement. As a research, sample weight at 220 mg/tablet and tablet-making pressure at 2.5 t were determined as the most suitable parameters. This research provides effective data for Terahertz measurement of soil samples using tablet-making method, and also provides a scientific reference for tablet-making method of other solid sample and THz measurement.
