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Issue 11 ， 2013
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Improvement of high-gain shot-noise detector
Abstract：Based on the special demands of quantum optical experiments for low noise detectors, a high gain and shot noise detector was designed by combing an AC current coupled trans-impedance pre-amplify circuit and an ETX500 photodiode. Compared with existing detectors, the designed detector shows better characteristics in gain, bandwidth and AC & DC saturation. The output characteristics of the detector were measured by using a 1 064 nm single frequency laser as a source and a frequency spectrum analyzer as the measuring instrument. Measuring results show that the power noise spectrum of the detector is 10 dB higher than that of electronic noise spectrum when the injecting power for the detector is more than 850 μW at 2 MHz. Furthermore, the bandwidth of the shot noise detector reaches 5 MH when the input infrared laser power is above 1.62 mW. The remarkable linearities for the DC and AC currents are available when the input infrared laser power is increased to 36 mW. Considering its higher gain and better DC & AC saturation characteristics, the detector is advantageous to quantum optic experiments.Keywords：quantum optics;trans-impedance pre-amplify circuit;shot noise detector;gain;saturation characteristic- 54
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Published：2020-08-12 -
Short-range experiment of passive ranging by oxygen absorption
Abstract：By using an acousto-optic tunable hyperspectral imaging spectrometer as measurement equipment and a halogen as the target, a short-range experimental program was designed to verify the passive ranging technology based on oxygen absorption. The basic principles and experimental program of the passive ranging technology based on oxygen absorption were introduced. Then, experimental equipment and a target were chosen based on ranging principles and assumptions, and the passive ranging technology was tested and verified under short-range conditions. Experimental results proof that this passive ranging technology also has the ranging capability when the target radiation and atmospheric conditions are unknown, which shows the feasibility and advantages of this ranging technology. The measuring range is solved by a software simulation curve and a model fitting curve, and the results give that the 4.26% ranging error comes from the model fitting curve and 6.23% ranging error from the software simulation curves. This result demonstrates that the model fitting curve based on experimental data not only can invert the target range in higher accuracy, but also can solve the measuring range of a far-range target by the curve extrapolation.Keywords：passive ranging;oxygen absorption;hyper-spectral imaging;baseline strength- 48
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Published：2020-08-12 -
Processing FBG sensing signal with three-point peak-detection algorithm
Abstract：To obtain the center wavelength of a Fiber Bragg Grating(FBG) sensing system, an improved peak detecting method, three-point peak-detection，was proposed. After researching on the process of algorithm, three elements(window sizes, sparse data and wavelength intervals)that impact the accuracy of peak-detection were determined. As selecting window sizes reasonably would enhance the accuracy of peak-detection, a derivation method was used to determine the size of the spectral processing window. Then, by setting sampling intervals, spectral window data were re-sampled to obtain sparse spectrum data and perform a polynomial fitting for the sparse data. Finally, the wavelength interval was chosen to determine the coordinates of three points and to search the peak of FBG wavelength. The results of experiment and simulation indicate that the number of spectrum data is three, when the size of processing window is chosen to be 0.4 nm and the re-sampling interval is 0.18 nm. Moreover, when the wavelength interval is chosen to be 0.22 nm, the peak error of proposed method is 0.4 pm, better than that of other methods. It will meet the requirements of FBG sensing systems for demodulating precisely.Keywords：Fiber Bragg Grating(FBG);peak detection;spectral window;sparse spectral data;sample interval- 73
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Published：2020-08-12 -
Design of uniformity correction masks based on shadow matrix
Abstract：To control the thickness distribution accurately in optical coatings for optical elements, correction masks should be designed according to details of coating machines and substrates. However, the shapes of correction masks are hard to predict for restrictions from many factors. Normally, a laborious method is used to correct masks by slightly adjusting their shapes repeatedly. To solve this problem, the concept of the shadow matrix was proposed. Based on this concept, a design method of correction masks for coating thickness was proposed. The relation between thickness distribution and mask shape was established based on partitioning of the mask reasonably. Therefore, mask shapes could be derived without additional mending processes. A uniformity mask was designed and manufactured for a planetary fixture by using this method. Experiments show that the measured uniformity is better than 0.3% PV or 0.1% rms on the range of φ300 mm. The results prove the validity of this method and indicate that it can meet the requirement of optical elements in coating processing for adjusting thickness uniformity in higher efficiency and reliability.Keywords：thermal evaporation;Coating thickness uniformity;Planetary fixture;Correction mask;Shadow matrix- 59
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Published：2020-08-12 -
Multi-channel fiber-optic displacement sensor based on data fusion
Abstract：A multi-channel fiber-optic displacement sensor was proposed based on the multi-sensor data fusion theory. By using a fiber as the input channel, and three fibers as the output one, every two channels constructed a two-channel fiber-optic displacement sensor. Then, the data from different two-channel fiber-optic sensors were fused to extend the measurement range of the sensor. Furthermore, the sensor measurement results were normalized to obtain the plurality of output characteristic curves of the sensor. By selecting the appropriate area from the plurality of output characteristic curves, the operation range of the sensor was determined. Finally, the data were processed by regression analysis and neural network algorithm respectively and the range of application, advantages and disadvantages of the methods were discussed. The results show that the measurement accuracy and stability have been improved. The greatest relative error by the Radial Basis Function(RBF) neural network is less than 1.0%, and the dynamic range of three channel fiber optic displacement sensor is extended to 1.5 times that of dual channel sensors with appropriate data fusion.Keywords：fiber optic displacement sensor;multi-channel;data fusion;regression analysis;Radial Basis Function(RBF) neural network- 40
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Published：2020-08-12 -
Simultaneous and on-line detection of multiple gas concentration with tunable diode laser absorption spectroscopy
Abstract：Generally, Tunable Diode Laser Absorption Spectroscopy (TDLAS) can detect only one kind of gas because of its narrow line-width. To detect the multi-component gas in real time simultaneously or near simultaneously, three kinds of detection methods were reported by taking 1 578 nm-H2S, 1 747 nm-HCl and N2 mixture for examples. The three methods are called timeshare-sawtooth method (10 kHz sin wave, 30 Hz asynchrony sawtooth wave), optical-switch method (same frequency 10 kHz sin wave, 30 Hz sawtooth wave) and multi-frequency modulation method (10 kHz and 20 kHz sin wave). The experimental results for the three methods show as follows: the method one gives fewer effects on measuring results apart from amplitude changes. The method 2 shows slightly unstable moments in the switching process, but it has no effect on concentration inversion in the later stage of the experiment. Moreover, in the method 3, the Signal-to-noise Ratio (SNR) and the anti-interference ability are improved, and the SNR has increased about 0.95 and 3.17 times for monitoring HCl and H2S when lasers are on or off. The three methods mentioned above have advantages on less investment, simple adjusting, and easy operation, also they can monitor many kinds of gases with the changing modulation parameters or switch channels, simultaneously.Keywords：Tunable Diode Laser Absorption Spectroscopy (TDLAS);Multi-component gases;Timeshare-sawtooth;Optical-switch;Multi-frequency sin-wave modulation- 58
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Published：2020-08-12 -
Testing system for radiation effects of CCD and CMOS image sensors
Abstract：A radiation effect test system for Charge Coupled Device(CCD) and Complementary Metal Oxide Semiconductor Transistor Active Pixel Sensor(CMOS APS) image sensors was developed to further study the space radiation effects of these devices and to accurately evaluate their space radiation adaptability. The system is an integrated optic-mechanical-electric equipment, and contains three subsystems for testing photoelectric responses, spectrum response and processing output data. It is able to comprehensively and quantitatively test and analyze the photoelectric response and spectral characteristics of the devices. The system shows its spectrum range and spectrum resolution to be 0.38 to 1.1 μm and 1 nm, respectively. The system has been combined with the irradiation facilities in Xinjiang Technical Institute of Physics & Chemistry to constitute a platform for radiation effect simulation experiments and anti-radiation performance evaluation of photo-electronic imaging devices. Currently, the system has provided a strong support for the research &development of domestic anti-radiation CCD and CMOS APS devices, including type-selection, examination and evaluation of imaging devices of space sectors. The results show that this system can satisfy the requirements of radiation effect research on CCD and CMOS devices.Keywords：CCD;CMOS APS;Radiation effect;anti-radiation performance- 54
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Published：2020-08-12 -
Stability of demodulation system for fiber Bragg grating
Abstract：The demodulation based on a linear filter determines the changes of external temperatures and pressures according to the ratio of optical powers from two beams. However, this paper points out that the ratio of two beams changes with the reduction of total powers of a light source under the same state of temperature and pressure by practical experiments and it effects the system stability seriously. In order to improve the stability of the system, this paper analyzes the changes of ratio of optical power from two beams, and obtains that the background noise is the significant reason that affects the two beams′ ratio. Then it processes the background noise by a processed method. The experiment result shows that the Fiber Bragg Grating (FBG) sensor has a constant ratio under different temperatures and changed light source powers after processing the background noise. Experiments demonstrate that the method has improved the stability of the system and it also applies to the stability measurement in strain and pressure experiments.Keywords：optical fiber sensor;modulation system;noise analysis;Fiber Bragg grating(FBG);linear filtering- 75
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Published：2020-08-12 -
Multi-mode Optimization Technique for Large Optical Aspheric Mirror
Abstract：Abstract: In order to manufacture a large aspheric mirror in high efficiency and precision, a new method which uses multi-mode optimization was introduced. This method is based on matrix calculate, use different tool influence functions at one time when calculating dwell time, extending conventional calculation of dwell time to algorithm which uses a set of different TIF, extend solution area of dwell time. In the end did a simulation of polishing an error map with actual parameters using multi-mode method. The simulation result shows that compared to conventional way using multi-mode technique can improve efficiency by 50%, convergence rates of the RMS value better than before. When simulation on the real surface RMS changes from 0.115 to 0.0044, the convergence rates is 0.6212 which is satisfied for real manufacture. Multi-mode technique can improve polishing efficiency and maintain good precision, it can forms an attractive solution for the large optical aspheric mirror fabrication capability and has large potential.Keywords：Key words optical fabrication;multi-mode technique;matrix equation;convergence rates;large aspheric mirror- 77
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Published：2020-08-12 -
Smoke detection based on multispectral separation
Abstract：Smoke detection is very important in early-warning of forest-fire. Because of the limitations of lower anti-interference ability, traditional technology is hard to distinguish fire smoke, water fog, the grass and other false information. Therefore, a new smoke detection method based on multispectral separation is proposed. First, band pass filters in the region of 460~520 nm, 540~570 nm, and 580~610 nm were used to seize the principal components in spectra emitted by the things under monitoring. Then, plane of the transform domain was build from these principal components, with simple algebraic judgment on the plane, classification and recognition of the smoke, fog and grass were performed. Finally, with as many as 1000 times Monte Carlo simulation, the three-band spectral analysis method proposed has the maximum separability, and easy operation. The proposed method could overcome the shortcoming which cannot distinguish smoke and water fog in traditional image and video detection methods, it no longer needs complex spectra classification algorithms, has certain practical value in the field of fire monitoring.Keywords：Smoke detection;multispectral;PCA;separation- 57
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Published：2020-08-12 -
The application status of the optical fiber Bragg grating in the field of welding monitoring
Abstract：Optical Fiber Bragg Grating(FBG) should be metallized prior to using in the field of welding monitoring, thus a nice proctection can be acquired and the temperature sensitivity will be enhanced. Several topics concerning the mornitoring of the welding process using FBG were analyzed. Firstly, the status of the protection and sensitivity enhancement of FBG was briefly summarized, the merits and shortcomings of each method were pointed out based on the comparision of the melt coating, vacuum evaporation, sputtering, chemical plating and electroplating. Secondly, two important issues for the application of FBG in the welding mornitoring were analyzed, i.e. (i) calibration of the sensing singal and sensitivity of the FBG and (ii) distinguishing the coupled sensing data. After that, the illustrations of the real-time monitoring of welding using FBG concerning temperature and strain were introduced, i.e. the FBG-mornitoring of FSW, MIG and TIG welding. The associated issues, (i) the sensors installation and layout, (ii) protection and (iii) reference sensors selection, were systematically analyzed. In addition, the feasibility and prospect of the application of the FBG in the monitoring of the ultrasonic welding and brazing were analyzed. At the same time, the issues and difficulties in the real-time mornitoring of welding process were pointed out, i.e. (i) difficulties for monitoring the inside of welding joint; (ii) the data errors induced by the poor conduction between the gule pasted FBG and the weld surface, (iii) temperature and strain cross sensitivity.Keywords：FBG;metallization;Welding;real-time monitoring- 58
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Published：2020-08-12 -
Mathematical Model of Contacting Freeform Surface Contour Measurement
Abstract：To unwind the requirement of a freeform surface for the position adjustment and to provide high precision measurement results in a high precision contacting freeform surface contour measurement, this paper proposes a mathematical model based on the least square method. The model can fit the measured dada to obtain optimized position parameters. After analysis of possible causes for the measurement error of Coordinate Measuring Machine(CMM), the model can be used to correct the errors caused by the rotation in the X, Y, Z axes and the eccentricity in the X, Y, Z direction that exist in the positioning of freeform surface. By mathematical simulations, it is proved that this model achieves high precision in correction of the errors for eccentricity less than 1 cm and inclination less than 0.1 °and shows a very reliable and effective result. It provides loose workpiece positioning conditions, high precision and reliable measurement results. The analysis principles proposed also offer a reference for other contacting freeform surface contour measurement methods.Keywords：Freeform surfaces;contour measurement;Coordinate Measuring Machine(CMM);mathematical model;least square method- 42
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Published：2020-08-12 -
Highly sensitive and multi-parameter optical detection for whole blood on centrifugal microfluidic chip
Abstract：The absorbance measurement method has a shorter optical path due to the microfluidic chip with smaller sizes. Therefore, a multireflection structure based on a quasi Fabry-Perot cavity was proposed to enhance the optical path length and complete the highly sensitive and multi-parameter detection for the whole blood on the centrifugal microfluidic chip. First, the optimal condition of the largest path length and the proper Signal and Noise Ratio(SNR) were analyzed theoretically. The results indicate that the maximum path length is only inversely proportional to the square of the beam diameter and the SNR is dependent on the reflectivity of the mirror and the number of reflections. Then, a detection pool was designed, the structure sensitivity of the pool was verified by the methylene blue solutions with different molar concentrations, and its path length was proved to be improved by two orders. Finally， the albumin and glucose in the whole blood on the centrifugal microfluidic platform was measured, and the good linearity with typical R2(linear relation coefficient) values of 0.999 07, 0.993 94, and 0.992 87 were obtained. From these results, it concludes that the quasi Fabry-Perot cavity is suitable for the whole blood biochemical detection and can satisfy the requirements of accuracy.Keywords：Microfluidic chips;Quasi Fabry-Perot cavity;Pathlength;SNR;R2 value- 50
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Published：2020-08-12 -
High Accuracy Temperature Response Modeling of Projection Lens under Thermal Disturbance
Abstract：In consideration of the repetitive disturbance, time lag and a larger time constant in a temperature control system for the projection lens, a temperature control experimental platform of projection lens was built. The structures, data preprocessing method and modeling algorithm for the experimental platform were researched, and a high precision temperature response model was established. Firstly, Taking into account the request of a lithographic machine for stringent vibration and cleanliness, the long-distance range cascade water cooling control system was designed. Then, the step response experiment of projection lens on the temperature was carried on, and the temperature response transfer function of projection lens was established with the two-point method(coarse model). Furthermore, pseudo random input signal was designed on the basis of the transfer function, and the input and output data were preprocessed by using the piecewise linear method. Finally, the iteration least square algorithm was designed to obtain the ARMAX temperature response model of projection lens. The temperature control experiment based on the model show that the temperature stability of the projection lens achieves ±0.001 ℃ in environment temperature with a fluctuation amplitudes up to 0.6 ℃ and thermal disturbance of 3 W, which meets the requirements of projection lens of lithography for ultra-high-precision temperature control.Keywords：Projection objective;thermal disturbence;Pseudo-random signal;System identification;temperature control- 72
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Published：2020-08-12 -
Design of voice coil force actuator in thin mirror active optical system
Abstract：A contactless surface correction method for the surface deformation of a primary mirror was designed based a voice coil motor to improve the performance of a thin mirror active optical system. The working principle of the voicecoil motor was discussed , the contactless voice coil force actuator with high linearity and a small size was designed, then the performance of the force actuator was simulated and verified. After comparing the structures of traditional actuators, the overall structure of the voice coil force actuator was designed according to the requirements of application in the thin primary mirror experiment system, the physical model and mathematical model were also established and the parameters of voice coil force actuator were proposed. The experimental results show that the voice coil force actuator is a contactless linear system, and its output force is up to ±0.5 N. Whin this range, the linearity is less than 0.09%.Keywords：Optical telescope;active optics;Thin mirror;force actuator;voice coil motor;magnetic field analysis- 38
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Published：2020-08-12 -
Design of digital handle control system
Abstract：A digital handle control system was established to overcome the voltage attenuation and poor accuracy come from the handle control equipment far from the servo system in a special environment. Firstly, the design scheme of the system hardware was introduced and the design theory of the main circuit was described particularly. Then, the system software and its working mode were given. Finally, three kinds of communication modes were discussed. The digital handle control system can simulate AD sampling, AD transform and data processing for voltage values by a handle level and can complete data communication with a digital computer and a digital servo controller by a RS422 serial directly. Experimental results indicate that the sampling precision of the digital handle control system can achieve 10 bit and the error is 0.098%. These results satisfy the system requirements for digitalization, miniaturization, integration, modularization, higher precision, as well as strong anti-jamming.Keywords：handle control system;Single Chip Machine(SCM);digitalization;Wireless communication;CAN communication- 63
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Published：2020-08-12 -
Structure optimization of parallel CMM
Abstract：A novel style Coordinate Measuring System(CMM) based on the 3-PUU parallel mechanism was proposed to realize 3D measurement with only one linear grating and two precision guides. On the basis of a previous prototype with passive motion, a prototype with active motion was re-designed after optimizing the structure parameters of the previous prototype. Firstly, dimensions and positional parameters of main components were decided by the 6-bar direct kinematics model and the principle of maximum measuring space. Then, by re-designing and arranging the pose of each joint, the measuring space of CMM was ensured. Finally, according to the motion characteristics and parameters of the designed CMM prototype, the deformation of key components was processed by Finite Element Analysis (FEA) to control and decease the affect of deformation on the precision of the CMM. As compared with the previous prototype, the proposed design has a measuring space of 1 050 mm×535 mm×426 mm，which enlarges the measuring space 92% in x axis, 134% in y axis, 113% in z axis, respectively, and its mechanical properties can be improved greatly.Keywords：parallel mechanism;coordinate measuring machine (CMM);structure design;Finite Element Analysis(FEA)- 49
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Published：2020-08-12 -
Type synthesis of 3-DOF parallel support system for telescope secondary mirror
Abstract：To realize tip/tilt and focus adjustment for a telescope secondary mirror, several types of parallel support systems were designed and their dynamic characteristics and construct selection were analyzed. First, the screw theory was used to realize the type synthesis for 2R1T (two-rotation and one-translation degrees of freedom) parallel mechanisms with 3 symmetrical branches. 12 types of feasible mechanisms with the fewest joint in each branch, the smallest inertia and linear actuators were selected for the support systems. Then, the selected mechanisms were classified according to the actuating characteristics and constraint properties and the kinematics models were established respectively, including actuation models and constraint models. Moreover, ZXZ Euler angels were introduced to describe the orientation of moving platform and to simplify the description and analysis of orientation and parasitic motion for 2R1T parallel mechanisms. Finally, a 1.2 m telescope was taken as an illustrative example to calculate the parasitic motion induced by the constraints. The results indicate that 7 types of mechanisms with constraint force parallel to the static platform have smaller parasitic motions no more than 0.27 mm. The kinematic model and design results provide theory basis for the following analysis on accuracy and stiffness.Keywords：telescope;3-dof parallel support;type synthesis;Kinematics modeling;parasitic motion- 60
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Published：2020-08-12 -
Self-temperature compensation for high quality factor Micro-machined gyroscope
Abstract：A temperature compensation system was build by using the drive-mode natural frequency as a virtual temperature sensor to achieve high-precision temperature compensation for the scale factor and zero bias of a micro-machined gyroscope. The temperature characteristics of the drive-mode natural frequency were explore, and its coefficient （-26.9±2.03）×10-6 ℃ was obtained. The frequency stability was translated to temperature precision to be 0.075 ℃ at 1 s average and 0.004 ℃ at 20 s average. On the basis of analysis of the temperature characteristics of scale factor and zero bias, a second-order temperature compensation scheme was proposed, and the principle and block-diagram of compensation algorithm were given. Finally, the scale factor and zero bias were compensated using the drive-mode natural frequency. The experiment results show that the maximum relative change of scale factor is reduced from 2.1% to 0.05% and that of zero bias is reduced from 8.9% to 0.1% at -40 ℃ to 60 ℃. The zero bias experiment at room temperature for 2 hours shows that the bias nonstability is reduced from 4.1(°)/h to 0.42(°)/h after compensation. These results satisfy the demand of micro-machined gyroscopes for high-precision temperature compensation.Keywords：micro-machined gyroscope;temperature compensation;natural frequency;scale factor;Zero bias- 41
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Published：2020-08-12 -
Joint calibration of multi-sensor measurement system
Abstract：In combination of a coordinate measuring machine and a monocular vision measuring system, a multi-sensor joint calibration method was proposed by a flip-over probe and a vision probe. A 4 mm smooth ring gauge was used as a calibration part and a rotary table, a precise sliding table and a vision system were taken to adjust the imaging plane of the gauge. Then, the vision measurement system was used to extract the inner hole center image coordinate of the ring gauge, involving in setting the Region of Interest（ROI）, binarization, morphologic denoising, sub-pixel edge detection and the extraction of cycle center image coordinates by the least square method. Furthermore, by fitting the inner cylinder of the ring gauge to obtain an axis line, the coordinate under the instrument coordinates of the same point was extracted by a trigger probe. Finally, joint calibration was completed by solving the equation using least square method. The experiment results show that calibration error is within 6 μm, which is better than that of existed other calibration methods and can meet the need of joint measurement for measuring accuracy.Keywords：Monocular vision measurement system;Touch trigger probe;Multi-sensor;Joint calibration;coordinate measuring machine (CMM)- 42
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Published：2020-08-12 -
Field balancing of magnetically levitated motor in high-efficiency and high-accuracy
Abstract：A new balancing method based on zero-displacement control for a Magnetically Levitated Rotor (MLR)was proposed to reduce the vibration and to improve the levitation performance of the magnetically Levitated motor (MLM). First, the static/dynamic unbalance models of MLR were discussed in polar coordinates, and the relationship between MLR parameters and correction-masses was derived. After analyzing the characteristics of the above relationships in different control modes, a conclusion was obtained as follows: the correction-masses can be solved from the control current directly in zero-displacement mode, as the electromagnetic force is a linear function of the control current and can be offset by unbalanced centrifugal force. Then, a general frequency selector was utilized to control the rotor to spin around its geometric axis to achieve the zero-displacement mode and the synchronous control currents were extracted to compute the correction-masses. Finally, based on the current stiffness learning errors, the second balancing was completed in high-accuracy by correcting conversion coefficient matrix on line. The experimental results show that the correction-masses can be obtained through a single start-up, and the rotor vibration and control current have reduced by 98.6% and by 98.7% respectively after the second balancing using the corrected conversion-coefficient-matrix. The status of zero-displacement and zero-current are achieved after the field balancing with high-efficiency and high-accuracy.Keywords：Magnetically levitated rotor;Field balancing;Zero-displacement control;Synchronous control current- 43
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Published：2020-08-12 -
Growth and Characterization of Lead Zirconate Titanate (PZT) Thin Films
Abstract：This paper explores how to prepare the Pb(ZrxTi1-x)O3(PZT) thin films by using the sol-gel method on a silicon substrate, then it tests the film characteristics by different methods. The solution with different compositions and proportions is designed according to the molecular formulas, and then the solution is coated on Titanium (Ti) or Platinum/Titanium (Pt/Ti) substrates. The X-ray diffraction (XRD) analysis is used to characterize the orientation and crystalline quality of the PZT thin films, and the Atomic Force Microscopy(AFM) is used to study their morphologies. The influences of different heat treatment temperatures on the crystalline quality and surface morphology are analyzed. Based on this, a Micro-electro-mechanical System(MEMS) process is developed for the PZT thin film structure to measure their ferroelectric properties, and a sawyer tower circuit is used to measure the polarization electric hysteresis. The results show that PZT thin films prepared by the sol-gel method have good ferroelectric property and morphologies at heat treatment of 400 ℃ and annealing treatment of 650 ℃, and can be applied to the PZT-based MEMS and nano devices.Keywords：Lead zirconate titanate thin film;heat treatment;annealing;ferroelectric properties;Sol-gel method- 44
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Published：2020-08-12 -
Design of diamond carriage system for large diffraction grating ruling engine
Abstract：The diamond carriage system of a grating ruling engine was designed. The diamond lifter part was installed on the plate which could be free to revolve around the saddle-shaped slider. The diamond lifter part and the load-bearing part were separated by the hinge to reduce the error of the diamond position caused by the saddle-shaped slider’s deformation and offset. The movement error of the diamond carriage as well as its influence on the diamond position were analyzed, then a optical detection structure was proposed to measure the displacement of the diamond carriage relative to the guide rail at the movement stage by a dual-frequency laser interferometer. The measuring results at the stage of about 70 mm show that the maximum displacement of the diamond carriage relative to the guide rail is up to 60 nm in the ruling stage. As the diamond is constrained by the coatings, the error of the diamond position is even more less. A diffraction grating with 70 mm×70 mm area and 600 gr/mm has been ruled with the changed diamond carriage and it shows a weaker stray light and good quality as compared with traditional gratings.Keywords：Grating ruling engine;diamond carriage system;Dual-frequency laser interferometer;detection path- 48
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Published：2020-08-12 -
Poselets for Pedestrian Detection
Abstract：A part-based mixture model(Poselets) was ultilized to alleviate the problem of pedestrian detection under occlusion and articulation. Firstly, Procrustes distances between similar pedestrian parts were calculated to gather training exmaples with the same configurations. Then, common parts of frontal pedestrian described by Histogram of Oriented Gradient(HOG) were trained to get discriminative models. A test was carried out on a validation set to find out which parts were more accurate,and those pictures which were not detected formed the hard set.Other complementary parts were explored on the hard set, afterwards, all these parts formed the final Poselets detector. While detecting, Poselets were clusterd if the symmetrized KL-divergence between two Poselet activations were small. The bounding box of a pedestrian was inferred by the bounding boxes of the Poselets in a cluster. Based on the test of the INRIA pedestrian dataset, it is showed that the detection rate increases from 77% of Poselets to 81% in this paper while False Positive Per Image(FPPI) is 0.5. It is concluded that the part selection mechanism proposed in this paper promotes the detection rate with speedup rate about twice of the traditional method, meanwhile it reduces the number of models.Keywords：Histogram of Oriented Gradient(HOG);Poselets;support vector machine;Pedestrian detection- 50
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Published：2020-08-12 -
Rapid and parallel image compression system with ultra-low delay for unmanned aerial vehicles
Abstract：A hardware parallel image compression system was designed according to the special requirements of unmanned aerial vehicles (UAVs) for image compression in low delay and high speed coding. A compression algorithm based on the wavelet analysis theory combined with zero-run-length coding index Columbus was designed for source coding techniques. In the algorithm, the wavelet analysis was applied to remove the redundancy of pixels, and the optimal quantization was introduced to remove the redundancy of pixel probability by zero-run-length encoding and exponential Columbus. The proposed algorithm was realized in a Field Programming Gate Array( PFGA) by a designed mode of the parallel processing, which makes the image sample, transformation and the coding of the each wavelet offspring coefficient executed in synchronization. Experimental results show that this compression system can satisfy four pieces of high resolution images with a resolution of 2 048 pixel×2 048 pixel×12 bit, and the capacity of data throughput achieves 280 Mpixel/s. Moreover, image codec propagation delay is less than 100 ms for the format of 1 024 pixel×768 pixel.Keywords：unmanned aerial vehicle;image compression;source coding;Parallel processing;wavelet analysis;ultra-low delay- 46
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Published：2020-08-12 -
Hyperspectral Remote Sensing Image Classification Based on SDE
Abstract：Sparsity Preserving Projection(SPP) is a new algorithm for reducing dimensions of dataset based on a weighted graph( l1-Graph), which reconstructs the weighted graph by the sparse relationship of train samples. However, SPP is an unsupervised learning method essentially, and it doesn’t employ any prior knowledge of class to extract identification features. For this issue, a novel algorithm, Sparsity Discriminant Embedding (SDE) is proposed. Unlike SPP, the SDE adopts the class information of train samples when it constructs weighted graph of sparse reconstruction relationship. The projection matrix of the SDE is obtained via optimizing objective function and making different kinds of data points separate in the low-dimensional embedding space via a projection. By combining both interclass manifold structure and sparse property, the SDE keeps the sparse reconstructive relationships of dataset, and employs the class information of train samples to increase the classification rate. The experimental results obtained from operations on Urban and Washington DC Mall datasets show that the classification efficiency of the SDE has improved greatly as compared to those of other algorithms. The obtained classification accuracy has been 73.47% and 98.35%, respectively, when 16 samples of each class are randomly selected for training.Keywords：Hyperspectral remote sensing image;dimensionality reduction;Sparsity representation;manifold learning;Sparsity discriminant embedding- 64
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Published：2020-08-12 -
Shadow detection based on texture feature in gray sequence images
Abstract：Moving object detection is usually effected by moving shadows from the object and it is easy to produce serious problems because the object and the shadow have the same moving characteristic. This paper proposes a method for moving shadow detection based on texture feature under the assumption that shadow regions in the current image have the same texture feature with a corresponding background image. For the discrimination between shadows and foregrounds, several texture similarity measurements are used and the shadows and foregrounds in current image are distinguished by computing the similarity of current image and background image. Furthermore, an adaptive method for segmentation of shadows and foregrounds is presented based on Ostu algorithm. In the end, experiments are carried on the video extracted from indoor or outdoor environments. Analysis indicates that the method has a excellent detection result in a video sequence with outstanding texture features. However, detection accuracy will be reduced when the image suffers blurring or noising. The obtained results verify the efficiency of the proposed method by using both of subjective evaluation and objective evaluation.Keywords：Gray sequence images;shadow detect;Ostu algorithm;Texture similarity measurement- 33
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Published：2020-08-12 -
Astronomical image restoration basedMaximum-likelihood incorporated parameter estimation
Abstract：The effective approximation mode based on Maximum-likelihood (ML) function proposed by Benvenuto was analyzed for astronomy image restoration, then a new image restoration algorithm with convergence faster than that of traditional ML method was proposed. In this algorithm, PSF known a priori was not required. The turbulence PSF was estimated from observed blur images to make the PSF estimation more accordance with an imaging environment. By incorporating adaptive estimation of PSF into ML restoration, an enhanced ML algorithm was presented. Additionally, the PSF was updated successively during iteration, and the ML restoration and denoising were performed alternatively in iteration. The results show that the proposed algorithm works much better than ML does. Taking the point source image for an instance, proposed method improves the image quality by 96.64%，69.26% and 25.6% respectively on the peak signal to noise ratio, mean square error and the correlation coefficient. In conclusion, the algorithm allow the iterative process in ML algorithm to converge stably and the image quality to be improved. Experiment results show that the presented method can be used routinely in astronomical image restoration.Keywords：image restoration;Space Image;maximum-likelihood;Point Spread Function(PSF) estimation;mixed Gaussian and Poisson noise- 41
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Published：2020-08-12 -
Time synchronization protocol based on dynamic route list for wireless sensor network
Abstract：To reduce the error accumulation of time synchronization in multihops for large-scale wireless sensor networks, a Dynamic Route List based Time Synchronization Protocol (DRL-TSP) is proposed. The protocol uses an available synchronization route list in each node, and allows the node to choose an optimal synchronization route to reduce the error accumulation. An identification called TTA (Time to Available) is used to deal with the synchronization failure and to ensure the reliability of the synchronization process. Experimental results indicate that the synchronization error in single hop is 5.29 μs when the optional upper links are 12 for each node, and the synchronization error is controlled under 11.10 μs within 10 hops. Moreover, the nodes of synchronization failure caused by time scale node invalidation are more low than that of Timing-sync Protocol for Sensor Network(TPSN) and close to that of Flooding Time Synchronization Protocol(FTSP). Experimental results show that the proposed protocol has a better performance than the current protocols in precision and reliability.Keywords：Wireless sensor networks;Synchronous Route Optimization;Dynamic Route List;Error Accumulation;Time Synchronization- 69
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Published：2020-08-12 -
Review of remote sensing image registration techniques
Abstract：Remote sensing image registration is an indispensable part for remote sensing image fusion, multispectral classification, environmental monitoring, image mosaicing and so on. In this paper, the important and latest registration methods for remote sensing are discussed and are divided into four types, including area-based methods, feature-based methods, hybrid-based model methods and physically-based model methods. Then, the classic algorithms of each type are analyzed respectively, and their advantages and shortcomings are also stated. The scale invariant feature transform algorithms are mainly discussed. Furthermore, the difficulties of remote sensing image registration techniques are summarized, including the multi-source remote sensing image registration, the real-time registration of remote sensing image, the nonlinear registration of remote sensing image and the accuracy evaluation of remote sensing image registration. Finally, the prospects of image registration are pointed out.Keywords：image registration;remote sensing image;feature extraction;Physical model.- 103
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Published：2020-08-12 -
Image compression algorithm based on adaptive exp-Golomb coding
Abstract：According to the low-calculation image compression algorithm introduced by Xu Yong, et al., a new image compression algorithm based on adaptive Exp-Golomb coding was proposed to implement the high-speed image compression. Firstly, the image with 4-level 5/3 was transformed with wavelet transform to obtain the optimal quantization step for each wavelet subband according to wavelet subband data model. Then, the JPEG_LS algorithm was employed to predict the value for the LL subband and to encode for all the wavelet subband data in the Zero-Run-Length algorithm. Finally, the adaptive Exp-Golomb coding was adopted to encode the data after Zero-Run-length algorithm. Experiment results show that the proposed algorithm can achieve a little better performance than Xu′s algorithm, when the bit rate is greater than 0.25 bpp; and the Peak Signal-to-noise Ratio (PSNR) of the proposed algorithm can increase by 0.2-2 dB when the bit rate is less than 0.25 bpp. It means that the algorithm improves the performance of compression. The Exp-Golomb coding model is extraordinary simple and can be implemented by the hardware completely.Keywords：image compression;wavelet transform;quantization model;adaptive Ex-Golomb coding- 56
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Published：2020-08-12 -
CCD irradiance calibration algorithm for HDR image acquisition
Abstract：To acquire a High Dynamic Range(HDR) image from the Low Dynamic Range(LDR) image acquisition equipment, the HDR image production technology was researched based on different exposure images in the same scene. Then, a CCD irradiance calibration method which doesn't require low noise images as the input was proposed. To avoid the deviation from the global optimum solution by excessive number of parameters, an energy function with fewer parameters consisting of the parameter model of CCD irradiance response curve, a residual penalty function, and a weighting function was proposed. The energy function was optimized by a low fitting error EMoR parameter model, squared residual penalty function suppressing image Gaussian noise, and the weighting function balancing image noise with deadline domain interference. Then the parameters were solved by minimizing energy function with Levenberg Marquardt(LM) algorithm which switched from rapid iteration to accurate iteration. Experimental results indicate that, with different number of model parameters and intensities of image noise, the response curve fitting Root Mean Squared Error(RMSE)∈\[0.0022, 0.0163\], the accuracy is increased by 39%-90%, the processing time is reduced by 38%-56%, and the obtained HDR-LDR mapping image is more similar with LDR image sequences and all the details of bright and dark regions are visible clearly.Keywords：High Dynamic Range(HDR) image;CCD;Irradiance calibration;Energy function- 53
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Published：2020-08-12
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