With the development of military industry and intelligence, accelerometer with high-performance will be demanded imminently. The resonant graphene accelerometer combines excellent mechanics and mechanism properties of graphene with the technique of MEMS accelerometer, with the advantages of high-performance, low-energy consumption, lowcost and mass production. An optically driven resonant graphene accelerometer is resonated by a laser beam with periodically varying intensity. A single-layer graphene fixed on its substrate is heated by the laser beam to make the graphene film resonate. When there is external acceleration, a proof mass fixed on the single-layer graphene film can change the resonant frequency by adding a force on the film. The acceleration can be calculated through the variation of the resonant frequency. However, the deadly drawback of the optically driven resonant graphene accelerometer is its low quality factor, which is large dissipation. In this paper, the mechanism of the squeeze-film air damping of a resonant graphene accelerometer is theoretically modeled. The influential parameters are optimized to decrease the damping. The results show that the effect of squeezefilm damping on quality factor can be significant, while that on resonant frequency can be negligible. Meanwhile, the squeeze-film damping will increase as the pressure, free and fixed edges of the single-layer graphene grow. The influence on the quality factor by changing the size of the free edges is more remarkable, compared to that of fixed edges. Therefore, decreasing the pressure and geometrical size of the single-layer graphene, especially the free edges, is an effectively method to reduce the damping of the resonant graphene accelerometer.
The Chinese National Steering Committee of Optics and Photonics (CNSCOP) is appointed by the ministry of education of China. The members of the committee are selected from 18 representative domestic Universities, 4 Chinese Academic Institutes and major enterprises. Through designing National high education standards for optic and Photonics; establishing Teacher’s training Center; Organizing National annual conference on Optics and Photonics education; setting up the Optics and Photonics Teaching Resource Sharing Platform etc., the CNSCOP has developed many process in order to improve the Chinese optical education quality and to promote the high achievements of students for whole country. In this paper, we will give brief introduction of all these activities.
The “Unity of Knowing and Doing” (UKD) theory is proposed by an ancient Chinese philosopher, Wang Shouren, in 1508, which explains how to unify knowledge and practice. Different from the Chinese traditional UKD theory, the international higher education usually treats knowledge and practice as independent, and puts more emphasis on knowledge. Oriented from the UKD theory, the College of Opto-electric Science and Engineering (COESE) at National University of Defense Technology (NUDT) explores a novel training model in cultivating opto-electric professionals from the aspects of classroom teaching, practice experiment, system experiment, design experiment, research experiment and innovation experiment (CPSDRI). This model aims at promoting the unity of knowledge and practice, takes how to improve the students’ capability as the main concern and tries to enhance the progress from cognition to professional action competence. It contains two hierarchies: cognition (CPS) and action competence (DRI). In the cognition hierarchy, students will focus on learning and mastering the professional knowledge of optics, opto-electric technology, laser, computer, electronics and machine through classroom teaching, practice experiment and system experiment (CPS). Great attention will be paid to case teaching, which links knowledge with practice. In the action competence hierarchy, emphasis will be placed on promoting students’ capability of using knowledge to solve practical problems through design experiment, research experiment and innovation experiment (DRI). In this model, knowledge is divided into different modules and capability is cultivated on different levels. It combines classroom teaching and experimental teaching in a synergetic way and unifies cognition and practice, which is a valuable reference to the opto-electric undergraduate professionals’ cultivation.
In the past two decades, the development of nanophotonics, particularly photonic crystals, plasmonics, metamaterials and 2D material photonics, has led to the demonstration of many new and exotic optical phenomena that greatly changed our understanding of optics and electromagnetics. Bringing such cutting-edge knowledge to optical courses for undergraduate and postgraduate students can not only help the students better understand the fundamental principles of optics but also significantly increase their study interests. We have done this in the past several years and here we show some examples ranging from metamaterials to the optical responses of graphene.
The combination of the strap-down inertial navigation system(SINS) and the celestial navigation system(CNS) is one of the popular measures to constitute the integrated navigation system. A star sensor(SS) is used as a precise attitude determination device in CNS. To solve the problem that the star image obtained by SS is motion-blurred under dynamic conditions, the attitude-correlated frames(ACF) approach is presented and the star sensor which works based on ACF approach is named ACFSS. Depending on the ACF approach, a novel device-level SINS/ACFSS deeply integrated navigation method is proposed in this paper. Feedback to the ACF process from the error of the gyro is one of the typical characters of the SINS/CNS deeply integrated navigation method. Herein, simulation results have verified its validity and efficiency in improving the accuracy of gyro and it can be proved that this method is feasible.
This paper is concerned with the acceleration sensing based on graphene resonator using finite-element software COMSOL Multiphysics. Based on the ordinary graphene resonator structure, a proof mass is attached to the surface of graphene sheet in order to sense acceleration and force more effectively. The rectangle-shaped gold proof mass is positioned at the center of the graphene sheet. Through COMSOL Multiphysics, the simulations about how the graphene sheet and mass’ dimension affect resonance frequency were performed and proper size parameters for the graphene resonator were chosen. By adopting these parameters, the analysis about the resonance frequency’s change responding to the acceleration or working force was carried out, which lays a foundation for further research of graphene resonator for acceleration sensing.
Star centroiding accuracy decreases significantly when star sensor works under highly dynamic conditions or star images are corrupted by severe noise, reducing the output attitude precision. Herein, an adaptive iteration method is proposed to solve this problem. Firstly, initial star centroids are predicted by traditional method, and then based on initial reported star centroids and angular velocities of the star sensor, adaptive centroiding windows are generated to cover the star area and then an iterative method optimizing the location of centroiding window is used to obtain the final star spot extraction results. Simulation results shows that, compared with traditional star image restoration method and Iteratively Weighted Center of Gravity method, AWI algorithm maintains higher extraction accuracy when rotation velocities or noise level increases.
The Strap-Down Inertial Navigation System (SINS) is a widely used navigation system. The combination of SINS and the Celestial Navigation System (CNS) is one of the popular measures to constitute the integrated navigation system. A Star Sensor (SS) is used as a precise attitude determination device in CNS. To solve the problem that the star image obtained by SS under dynamic conditions is motion-blurred, the Attitude Correlated Frames (ACF) is presented and the star sensor which works based on ACF approach is named ACFSS. Depending on the ACF approach, a novel device-level SINS/ACFSS deeply integrated navigation method is proposed in this paper. Feedback to the ACF process from the error of the gyro is one of the typical characters of the SINS/CNS deeply integrated navigation method. Herein, simulation results have verified its validity and efficiency in improving the accuracy of gyro and it can be proved that this method is feasible in theory.
Recently, heterostructures, combining the unique advantages of both graphene and transition metal dichalcogenides (TMDs, also known as MX<sub>2</sub>), have exhibited extraordinary photo-electrical properties, thus attracted tremendous interests worldwide. In this paper, we overviewed recent progress of MX<sub>2</sub>/Graphene van der Waals heterostructures, including the preparation methods, relevant parameters in opto-electronic measurements, physical mechanisms, existing experimental results and encountered problems. Here, we focus to cover the development of entire field, and provide a comprehensive and accurate understanding concerning this field, which may be helpful for interested researchers in this area.
Ship deformation is the main error source of partial reference. Such deformation can be estimated by laser gyro units and Kalman filter technology. For Kalman filter, deformation was divide into two parts, dynamic deformation, and static deformation. Traditionally, dynamic deformation is treated as AR2 model .In this paper, dynamic deformation is taken as a kind of ARX model. Based on actual data measured by Yuanwang-3 Space Survey Ship, simulation experiments are studied. Results show that the novel model can improve the measurement precision.
Lever arm effect has to be considered in transfer alignment technology. Between static lever arm and dynamic lever arm, the former has larger amplitude, and it is the major error source in transfer alignment. How to measure and solve it become an important problem. This paper takes vehicle as a rigid body. Assume that static lever arm does not change in a short time, based on two inertial measurement units(IMU), data are measured and constituted several matrixes properly. After that, by using least square method, static lever arm is solved finally. Simulation experiments are implemented, results show that static lever arm can be solved effectively. Further study shows that, the precision of the method can be improved by preprocessing low pass filter.
Smartphones are widely used at present. Most smartphones have cameras and kinds of sensors, such as gyroscope, accelerometer and magnet meter. Indoor navigation based on smartphone is very important and valuable. According to the features of the smartphone and indoor navigation, a new indoor integrated navigation method is proposed, which uses MEMS (Micro-Electro-Mechanical Systems) IMU (Inertial Measurement Unit), camera and magnet meter of smartphone. The proposed navigation method mainly involves data acquisition, camera calibration, image measurement, IMU calibration, initial alignment, strapdown integral, zero velocity update and integrated navigation. Synchronous data acquisition of the sensors (gyroscope, accelerometer and magnet meter) and the camera is the base of the indoor navigation on the smartphone. A camera data acquisition method is introduced, which uses the camera class of Android to record images and time of smartphone camera. Two kinds of sensor data acquisition methods are introduced and compared. The first method records sensor data and time with the SensorManager of Android. The second method realizes open, close, data receiving and saving functions in C language, and calls the sensor functions in Java language with JNI interface. A data acquisition software is developed with JDK (Java Development Kit), Android ADT (Android Development Tools) and NDK (Native Development Kit). The software can record camera data, sensor data and time at the same time. Data acquisition experiments have been done with the developed software and Sumsang Note 2 smartphone. The experimental results show that the first method of sensor data acquisition is convenient but lost the sensor data sometimes, the second method is much better in real-time performance and much less in data losing. A checkerboard image is recorded, and the corner points of the checkerboard are detected with the Harris method. The sensor data of gyroscope, accelerometer and magnet meter have been recorded about 30 minutes. The bias stability and noise feature of the sensors have been analyzed. Besides the indoor integrated navigation, the integrated navigation and synchronous data acquisition method can be applied to outdoor navigation.
In order to enhance the imaging speed of the 3D imaging lidar (light detection and ranging) and implement high-speed
3D imaging under static conditions, we propose a novel high-speed 2D laser scanner with an asymmetric 16-plane
rotating mirror. Firstly, this paper analyzes the principles and characteristics of common laser scanners used in 3D
imaging lidars, which mainly include a symmetric rotating mirror scanner, a vibrating mirror scanner, a oval line scanner
and a double optical wedge scanner. And then we propose an asymmetric 16-plane rotating mirror with a novel structure,
which can carry out faster scanning in 2D field with only one rotating mirror. The scanning principle and main structure
of the rotating mirror is introduced in detail. Based on the proposed asymmetric rotating mirror, a new high-speed laser
scanner for the 3D imaging lidar is implemented with some advantages: high scanning speed, large scanning field and
high reflectivity. Finally, the laser scanning experiment has been carried out with the proposed laser scanner. The
experimental results show that the scanning speed is above 30 frames per second, the scanning field is about 32°×12°,
the vertical resolution of each frame is 16, and the laser reflectivity is above 0.9. The proposed laser scanner can be
applied to areas such as groundborne, vehicleborne and airborne 3D imaging lidars.
In order to enhance the imaging speed of the 3D imaging lidar (light detection and ranging) and implement high-speed
3D imaging under static conditions, we propose a new 3D imaging lidar based on a laser diode and a high-speed 2D laser
scanner. The proposed 3D imaging lidar is mainly composed of a transmitter, a laser scanner, a receiver and a processor.
This paper introduces the components and principle of the proposed 3D imaging lidar first. And then some experiments
have been carried out to evaluate the performance of the 3D imaging lidar, in terms of scanning field, measuring
precision, scanning speed, image resolution and etc. The results show that the scanning field of the 3D imaging lidar is
about 26°×12°, the measuring precision is better than 5 cm (4 m distance), the scanning speed is greater than 30 fps
(frame per second) and the image resolution can reach 16×101. In addition, the 3D imaging lidar can obtain both the 3D
image and intensity image for the given target at the same time.
In order to enhance the measurement precision and detection range of the 3D imaging lidar (light detection and ranging), we propose a new broadband low-noise detection circuit for the pulse laser, which mainly includes a high-speed APD (Avalanche Photodiode) detector and a broadband low-noise transimpedance amplifier. In the detection circuit, a high negative bias voltage is applied to the APD detector and used to set the static input current of the amplifier NE5210 to 200 μA with a proper bias method. By this bias method, the allowable input current range of the amplifier NE5210 is enhanced by about 1 time. This paper introduces the main framework and performance of the detection circuit. The output noise voltage, output signal voltage and voltage SNR (Signal-to-noise Ratio) of the detection circuit are analyzed and calculated as well. Some experiments have been carried out with the proposed detection circuit, showing that the detection circuit can detect a narrow pulse laser with about 4 ns pulse width. Based on our experiments and analyses, the pass band of the detection circuit ranges from 0.56 MHz to 200MHz approximately, the allowable input current of the amplifier NE5210 varies from -460 μA to 0, and the effective output differential voltage ranges from -1.6 V to 1.4 V. The proposed detection circuit is implemented and tested in a high-speed 3D imaging lidar. As well as 3D imaging lidars, the detection circuit can be applied to the pulse laser range finder and other pulse laser detection system.
In order to enhance the time discrimination precision in the 3D imaging lidar, we propose a new time discrimination circuit, which improves both the delayer and the attenuator in the previous CFD (Constant Fraction Discriminator) circuit. The proposed circuit mainly includes a delayer, a low-pass filter, and a comparator. The delayer is implemented with a series of inductors and capacitors, which has some advantages: low signal distortion, small volume, easy adjustment, etc. The low-pass filter attenuates the signal amplitude and broadens the signal width, as well as reduces the noise by decreasing the equivalent noise bandwidth, and increases the signal slope at the discrimination time. Therefore, the time discrimination error is reduced significantly. This paper introduces the proposed circuit in detail, carries out a theoretical analysis for the noise and time discrimination error in the proposed circuit and compares them with the previous CFD circuit. The comparison results show that the proposed circuit can reduce the time discrimination error by about 50% under the same noise level. In addition, some experiments have been carried out to test the performances of the circuit. The experiments show that the time delay of the circuit is about 14ns, the time discrimination error is less than 150 ps when the voltage SNR ranges from 18.2 to 81.8, and the time discrimination error is less than 100 ps when the signal amplitude ranges from 0.2 V to 1.86 V. The tested time discrimination error is well in accordance with the theoretical calculation.
Proc. SPIE. 8538, Earth Resources and Environmental Remote Sensing/GIS Applications III
KEYWORDS: Clocks, LIDAR, Laser range finders, Field programmable gate arrays, Time metrology, Precision measurement, Picosecond phenomena, Analog electronics, Defense technologies, Temperature metrology
In order to reduce the negative influence caused by the temperature and voltage variations of the FPGA (Field
Programmable Gate Array), we propose a new FPGA-based time-to-digital converter. The proposed converter adopts a
high-stability TCXO (Temperature Compensated Crystal Oscillator), a FPGA and a new algorithm, which can
significantly decrease the negative influence due to the FPGA temperature and voltage variations. This paper introduces
the principle of measurement, main framework, delayer chain structure and delay variation compensation method of the
proposed converter, and analyzes its measurement precision and the maximum measurement frequency. The proposed
converter is successfully implemented with a Cyclone I FPGA chip and a TCXO. And the implementation method is
discussed in detail. The measurement precision of the converter is also validated by experiments. The results show that
the mean measurement error is less than 260 ps, the standard deviation is less than 300 ps, and the maximum
measurement frequency is above 10 million times per second. The precision and frequency of measurement for the
proposed converter are adequate for the 3D imaging lidar (light detection and ranging). As well as the 3D imaging lidar,
the converter can be applied to the pulsed laser range finder and other time interval measuring areas.
Proc. SPIE. 8202, 2011 International Conference on Optical Instruments and Technology: Solid State Lighting and Display Technologies, Holography, Speckle Pattern Interferometry, and Micro/Nano Manufacturing and Metrology
A high-perform and compact subwavelength binary blazed grating optical switch was designed based on
TiO<sub>2</sub>-on-SiO<sub>2</sub>. By appropriate choice of grating parameters including thicknesses, periods, height, and fill factor, to
optimize the diffraction properties, a relative high diffraction efficiency and large diffraction angle was obtained
simultaneously. The diffraction efficiency of the first switching channel is about 80% with a 45° diffraction angle, and
the diffraction efficiency of the second channel is around 90% with a 30° diffraction angle. The device layout is simple,
feasible, one-step etch, and compatible with standard CMOS technology processing.
Lidar and CCD camera have the excellent ability of capturing 3D information of objects and they are widely used for 3D
modeling. The effective fusion of 3D lidar image and CCD camera color image can give better results. The major
problem of fusion lidar data and CCD camera data is the coordinate calibration between them. In consideration of the
traits of lidar and CCD camera, a special 3D calibration object was designed, and an improved coordinate calibration
method was proposed, which fits a plane using principal components analysis and can highly improve the calibration
precision. After the lidar and CCD camera has been calibrated, the data they captured are transferred to fusion computer
by USB and network. Data processing and display are achieved in fusion software written in C++ and OpenGL.
Experiment results show that our real time image fusion system gives good result in the 3D reconstruction of objects, the
imaging rate of the system can get to 5 frames per second.
The steam flow in low-pressure turbine contained abundant water droplets, which will decrease the work efficiency and
pose potential threaten to operation safety, so measurement of steam wetness has brought great interest in electricity
generation industry. In this paper, a new measuring method using CCD (Charge Coupled Device) imaging technique was
proposed to determine the wetness in steam turbine based on the forward small angle light scattering theory. A simulated
steam turbine facility was designed to generate the wet steam, and light scattering experiments were carried out at
various working conditions in this device. The steam wetness parameters and droplet size distribution were obtained by
means of numerical inversion of the light intensity distribution based on Mie scattering theory. The results demonstrate
that the obtained data from the present analysis is in good agreement with the results of the theory analysis and previous
study, and the proposed method is proved to be suitable for steam wetness measuring and monitoring by further
A new extremely fast and high-power laser diode driver module is introduced, which is made of a fast high-power MOSFET and based on discharging capacitor. The main factors are analysed in theory, which determine the main performance of this kind of laser diode driver module. The whole performance of the laser diode driver module is simulated with SPICE module in detail, and the testing results of the produced laser diode driver module are described. The main methods to change the output peak power and current pulse width of the laser diode driver module are presented. The output peak power of the laser diode driver module is very high, which can reach 50 W. The output current pulse width of the laser diode driver module is very short, which is less than 8 ns. The laser diode driver module can directly drive many kinds of pulse laser diode in the market, and be used as the high performance transmitter driver module of time-of-flight ladar and laser range finder.