On the basis of the principle of integral imaging and the relation between camera array and display lens array, a pick-up system using a camera array for three-dimensional integral imaging was analyzed according to the geometric imaging theory and the ray tracing method, and the dependence of main recording parameters on display characteristics of integral imaging was obtained. A parameter design method for elemental images was proposed according to the display specifications and a pick-up system was designed by the proposed method in a pick-up distance of 49.6 cm and a camera space of 25 mm. The experimental results demonstrate that the pick-up system using the camera array can record the 3D information for a scene completely and the 3D display characteristics reach to the design requirements. Furthermore, the relationship between the pick-up parameters of the camera array and the display characters coincides with theoretical analysis, which verifies the display performance of designed system and the feasibility of the proposed method as well. The system can generate elemental images with large scenes and high resolution for mismatched full optical integral imaging systems.

The electrical characteristics of Silicon Photomultipliers(SiPMs) were analyzed on the basis of the behavior model of a micro plasma electron in the SiPMs, and an optimum design scheme for the SiPM front was proposed. The working principles of SiPM arrays were introduced, the electrical behavior model of a SiPM was given, and the advantage of SiPM for the underwater three-dimensional depth sounder was discussed. Based on the echoing characteristics of the underwater depth sounder, a high speed, high bandwidth preamplifier was designed, and an alternating current analysis and a transient analysis were performed. Results show that the preamplifier circuit has much high gain flatness in the bandwidth and the phase margin is more than 60°, which ensures the integrity of signals and the waveforms of laser pulse signals. Analysis and test results indicate that the SiPM arrays and the circuit design can satisfy the requirement of underwater three-dimensional depth sounder, and can improve the target acquisition performance of the laser underwater imaging systems.

The polishing principle of Double-Swing Method (DSM) was introduced, the relative movement characteristic between polishing lap and workpiece was analyzed, and the influence of polishing parameters on the relative movement was discussed. A mathematical model of the DSM in a movement state was established and its movement was simulated in a programming language. Then, simulation effects under different parameters was compared. The shape model of the polishing lap was presented, and the material removal character of the polishing lap with diffident shapes was verified.Finally,a rectangle off-axis aspheric mirror in a size of 224 mm×108 mm was polished by the DSM. The experiment result shows that to manufacture the off-axis aspheric mirror by the DSM can control the middle-frequency error and can obtain high working efficiency, and the surface precision is about λ/30 (rms, @633nm). Therefore, the DSM benefits the development of the manufacture technique for off-axis aspheric mirrors.

Ion beam etching technologies for developing large aperture Diffractive Optical Elements (DOEs) were reviewed. To meet the requirements of large aperture DOEs in high-power laser systems, an integrated graphite mask for ion beams and a multi-position etching strategy were investigated for a self-established KZ-400 etching facility to improve the uniformity for ion beam etching and the uniformity of ±1% for ion beam current along the major axis of the ion source was achieved in a range of 1430 mm. On-line optical measurement methods and experimental setups for Multilayer Dielectric Gratings (MDGs) and transmission DOEs were presented to measure the 1D spatial distribution of diffraction intensity and the ion beam etching depth based on fringes of equal thickness,respectively, by which the quantitative control of ion beam etching for large size DOEs was completed. Based on above techniques, a series of large aperture DOEs, especially MDGs with diffraction efficiencies more than 95% at 1 064 nm, beam sampling gratings,color separation gratings and beam sampling gratings for synchrotron radiation were fabricated successfully.

As 808 nm single emitter diode lasers have low output powers,they are limited to pump neodymium-doped double-cladding fiber lasers in end pumping. In order to enhance the pumping efficiency of the fiber laser by using single emitters,a fiber coupled module with several single emitter diode lasers was developed. First, the fast axis and slow axis of each diode laser were collimated by a micro-lens. Then, the output beams of diode lasers were combined with reflecting prisms. Finally, a suit of optical system designed by ourselves was utilized to expand and focus the beam into a optical fiber. Experiments show that this approach can greatly increase the brightness of the module with fiber coupled LDs. Four LDs with continuou output power of 5 W are coupled in a 105 μm multimode optical fiber with a core diameter of 105 μm and a numerical aperture of 0.2 when the working current is 5.8 A,it can offer the fiber output power of 15.22 W, coupling efficiency of 74% and the brightness over 1.4 MW/cm2·sr.

To reduce the fluctuation of frequency response of a Distributed Feedback (DFB) fiber laser used in underwater sound detection, an encapsulated structure with orifices was designed.With the encapsulated structure, both ends of the DFB fiber laser were fixed along the axes of the structure by the tension of polyurethane,and the fluctuation of mid-frequency response was restrained. The dynamics of the encapsulated structure was numerically analyzed with ANSYS, and a prototype of the new kind of hydrophone based on the structure was produced and tested with the vibration fluid column method. The results show that the fluctuation of frequency response of the DFB fiber laser is restrained effectively from 20 Hz to 800 Hz, and the acoustic pressure sensitivity reaches to -131 dB with the fluctuation less than ±1.5 dB. These results demonstrate that the performance of the DFB fiber laser hydrophone has been improved by the protection of the encapsulated structure and the tension of polyurethane.

A UV standard detector calibration method was researched to improve the calibration accuracy. A High Accurate UV Radiometer (HAUVR) was established, and the standard response of the UV radiometer was deduced. In calibration, the HAUVR was used to transfer standard and the substitution method was adopted to eliminate some uncertainty factors. Finally, two kinds of calibration methods, namely, standard light source and standard detector calibration methods, were taken to calibrate the irradiance of an untested light and the irradiance response of an ozone vertical detector. Calibration results show that the uncertainty of calibration has been decreased to 1.6% by standard detector calibration method, which proves the efficiency and high accuracy of the UV standard detector calibration method. It realizes the engineering applications of the UV detector calibration method.

The photothermal effect and thermal induced photorefraction change of aerosols in the atmosphere were researched. The method to improve detection sensitivity by increasing the number of photothermal effect zones and to reduce the costs by low coherence interferometry was proposed. A mathematics model to measure the aerosol absorption coefficients by photothermal low coherent interferomtry was established, the detection sensitivities from two ways, interferometric orthogonal measurement and interferometric fringe subdividing detecting, were analyzed, and the detecting limit in low coherent polarized interferometry was discussed. Experiments demonstrate that the detection sensitivity in theory can be 1×10-6 m-1. If a longer interaction length and more number interaction zones are choosen, higher sensitivity can be arrived. The theory and method proposed in this paper can provide references for aerosol measurements.

To eliminate the scatter light and central ghost in a classical fundus camera, the optical system of a catadioptric fundus camera with a field of view 40° and a working distance of 48 mm was designed. An off-axial reflecting ophthalmic lens with free form surfaces was designed to correct the off-axial aberrations. Two free-form-surfaces were introduced in the imaging objective system to correct the residual off-axial aberrations of the reflective ophthalmic lens. In the optimization of the imaging system, an eye model with varying defocuses was proposed to eliminate the negative effect of eye aberrations as well as to accommodate the eye with different refractive errors. Three adjacent illumination rings were introduced in the illumination part to avoid the undesirable light reflected by the eye optical system. Experiments show that the accommodation range of the system is between -10 m-1 and 10 m-1, the resolution at the object plane is 33 lp/mm across the entire field of view,and the maximum distortion is less than 8.5%.Furthermore, the illumination non-uniformity is less than 15% in the conditions without scatter light and central ghost. The designed catadioptric fundus camera with a free-form-surfaces show a satisfactory large field of view and a large working distance, and removes the undesirable scatter light and central ghost greatly.

To develop a Φ510 mm SiC ultra-lightweight mirror, this paper proposes an ultra-lightweight structure with a section in ship form, an internal structure in regular-triangle, and a face plate reinforced with regular-hexagon. When the design weight is 1.85 kg, the structure performance is compared with those of other two lightweight structures with the same weight by adjusting all structure parameters. It is shown that in the same 6 point supportings on mirror backs, this ultra-lightweight structure owns absolute advantages in the gravitational deformation of mirror surface (RMS) as comparing with other two structures when the optical axis is pointed to the zenith. Furthermore, Patran＼Nastran finite element software is used to simulate and calculate the gravitational deformation of the mirror surface when the axis is pointed to the horizon, and its thermodynamic and dynamical characteristics are analyzed. The results present that all performance indexes of this ultra-lightweight mirror meet requirements of applications. Finally, according to the design, a mirror blank with a weight about 2.2 kg and surface density about 10.8 kg/m2 is fabricated. With excellent perforultra-lightweight mirror; SiC mirror; reaction bonding; Patran＼Nastranmance, it has been up to the today's advanced level in the SiC ultra-lightweight mirror field.

To get the high accuracy 2-D spectra of a self-designed echelle spectrograph,a high performance area CCD camera was designed. Based on the characteristics of echelle spectrograph and CCD chip, the timing generator circuit, drive circuit and the data processing circuit for the CCD camera were developed,by which the low noise, high sensitivity and high dynamic rang were realized at the same time. Then, the test software of CCD camera was programmed with LabVIEW. Finally, the 2-D spectra of a Hg lamp were tested by using the area CCD camera. The result demonstrates that the area CCD camera can get the sharp 2-D spectra with high SNR. After reducing the spectra of Hg lamp, the standar spectral line is obtained. This CCD camera is steady, reliable and meets the needs of echelle spectrograph completely.

To measure the roll angle between two spacecrafts at the last-phase of spacecraft-docking accurately, a roll angle measurement system based on square wave magneto-optic modulation was present. A model of the modulated signal was present according to the Faraday effect and Malous law, and the relationship equation between the modulated signal and the roll angle was established according to the character of modulated signal. The combination of the variation trend of the modulated signal was used to delete the extraneous roots of the equation, then the roll angle measurement model based on square wave magneto-optic modulation was acquired. Simulation results indicate that the new method has higher measurement precision, and the measurement scale is -90~90°, wider than that of the traditional method. Furthermore, the new method shows advantage on data acquisition and data process.In conclusion,the method can provide a new reference for measuring the roll angle between spacecrafts in higher precision and wider scale for spacecraft docking.

A signal processing technique based on all-phase spectral analysis was proposed to reduce the displacement measurement error of a self-mixing interferometer. Self-mixing interference principle and signal processing technique were analyzed. First, the mathematical model and signal characteristics for the self-mixing interferometer were presented based on the model of laser oscillation cavity with three mirrors. Then, the displacement principle based on self-mixing interference was introduced. A all-phase spectral analysis was used to extract the phase of self-mixing interference signal to reconstruct the displacement of a reflective target and the signal processing algorithm was investigated with arithmetic simulation. Finally,an experiment system was established and the calibration result of bimorph PZT was presented. Experimental results indicate that the displacement error can be decreased to 4.4 nm by using all-phase spectral analysis. It concludes that the all-phase spectral analysis can reduce the displacement error of the self-mixing interferometer to nanometer level without increasing the number of optical elements.

A displacement measurement method for microcantilevers based on integrated dual gratings and a CCD image measurement system were presented. The displacement detection range was extended by using two gratings with a phase shift about π/2. The sensor chips were fabricated by surface sacrificial process. Grooves with the depth about 1/8 of the incident laser wavelength were etched on the glass substrate and two adjacent gratings patterned inside and outside of the groove and the reflective undersurface of a cantilever formed two phase sensitive integrated gratings, respectively. The integrated grating units formed an image on the CCD sensing surface through the 1st order diffraction light, and the gray value change of the light spot was related to the displacement change of the corresponding cantilever. Experimental results show that although the phase difference between the gratings deviates from π/2 caused by the depth errors of the etched grooves, the integrated dual gratings extend the range of displacement detection to multi periods. The insensitive areas at peaks and valleys for sinusoidal variation signal of interferometric displacement detection method are avoided by using alternately intensity signals from the two gratings. In the experiment, the measured displacement change of the cantilever is 650 nm.

To calculate the focal length of an off-axis Three Mirror Anastigmat(TMA) camera precisely and to guarantee its mapping precision,this paper researches and amends the classic mapping model and related formulas. First, the intersection angle of the off-axis TMA camera is re-defined,and the classic calculating formula for the focal length is modified. Then, the effect of earth curvature on the calculating focal length is analyzed, and the formula is further corrected. Examples indicate that when GSD is set to be 2 m,and the size of CCD, orbital altitude and the off-axis angle are 8 μm,700 km and 7°, respectively, the relative error of the focal length of a tilt-looking camera calculated by the classic formula and that calculated by the modified formula can reach to 2.6%, which will effect significantly on the mapping precision. Therefore,it suggests that the calculating formula for focal length of tilt-looking camera should take the off-axis angle into account when a off-axis TMA camera is used in photography.Furthermore, the classic calculating formula is still applicable for the ortho-looking camera.

A series numerical models were conducted by using the computational fluid dynamic software ANSYS CFX to research the internal temperature distribution of the hydrostatic thrust bearings of aspherical ultra-precision machine tools.An experiment was performed on the hydrostatic bearings and the spindle performance parameters of the worktable were obtained in 0,300,500 kg loads,respectively.The results show that the initial temperature of the oil lumen area is 20 ℃,the temperature arises from resistive oil edges towards,and the lateral temperature is higher than that of the medial.The respective highest temperature is 20.29 ℃ or 21.72 ℃ with a lubricant film thickness of 33 μm or 23 μm, and the thinner the oil film is,the higher the temperature is. The difference of the simulation and the tests are 3.33%,8.33%,1.32%, respectively,which proves the validity of design and simulation methods for hydrostatic thrust bearings.

As conventional transmission mechanism is difficult to realize coaxial rotation transmission in a narrow radial space,a coaxial transmission mechanism based on cylindrical cams is proposed.On the basis of the structure of a lens, the transmission mechanism is combined by two cylindrical cams,and one is initiative cam and the other is passive cam. Spiral slots are opened on the surface of both cams. When the spiral lead of the passive cam is n times that of initiative cam, the transmission mechanism can offer a transmission ratio of n. Transmission efficiency and transmission accuracy are analyzed and the relation between the angle of initiative cam’s spiral slot and the transmission efficiency and transmission accuracy is discussed. An experiment is performed to test transmission accuracy, which shows the transmission ratio accuracy is less than 1.6%. Obtained mechanism has compact structure,high accuracy and can be locked automatically.

To design a non-overlap vertical electrostatic combdriver for the optical translational micromirror of an optical phase modulator, a mathematic model based on the conformal mapping was built to research the driving performance of the combdriver in detail. According to the theory of complex variable function, an analytical model was established for the electrostatic field of comb actuator by conformal mapping. Then, the electrostatic force in a certain displacement range was deduced by the analytical model for researching the movable comb finger. The results were compared with the corresponding resolution by the Finite Element Method (FEM). Finally, a non-overlap vertical combdriver was successfully fabricated by Micro Electronic Mechanic System(MEMS) process, and an optical Michelson interference system was constructed to measure the static driving charateristics of the comb driver. The result shows that the displacement of proposed non-overlap vertical electrostatic combdriver is 325 nm (phase difference 2π) with a dc driving voltage of 28 V and the offset vertical comb actuator can be actuated to 2.07 μm under a dc driving voltage of 90 V. The measured results accord excellently with the simulated results using the conformal mapping and FEM method, which proves proposed analytical model to be correct. It can provide theoretical and pratical bases for design of non-overlap vertical electrostatic combdrivers.

An acceleration Feedback(AFB) is introduced to the servo system to improve the dynamic performance of a moving base optoelectronic stability platform. As it is difficult to establish a model for the moving base optoelectronic platform according to a moving object,the proposed acceleration feedback is realized by measuring angle acceleration signals directly. Simulation and analysis indicate that the dynamic stiffness of servo system can be enhanced and the starting and braking performance is improved with the AFB. Experiments show that the capability of resisting friction moment is increased significantly. The capability of resisting periodic disturbance is increased by 9.3db and the overshoot of speed step response is decreased by 4.9%, while the transition process has been greatly improved.The servo system has simpler structure,higher robustness,and shows better universality.

The measurement of continuous bending deformation for a circuit board surface was achieved by using digital off-axis Fresnel holographic interferometry. 1 501 holograms were recorded by applying a displacement load to both ends of the circuit board from 0 to 15 mm by the step of 0.01 mm.The interference phase difference was obtained by subtracting the complex amplitude phase distributions of two adjacent holograms with numerical reconstruction. Then, the out-of-plane displacement of the lighting measurement area was obtained according to the relationship between the phase difference and the out-of-plane displacement, and the measurement results were obtained by accumulating the bending deformation of the displacement load from 1 mm to 15 mm. By calculating the out-of-plane displacements of the same capacitor center in the lighting measurement area from five pieces of circuit boards with the same specifications, it indicates that the measurement results are no more than 0.008 mm for the type A uncertainty,no more than 0.003 5 mm for the type B uncertainty from a loading clamp and no more than 0.008 7 mm for the combined uncertainty. The results show that the method based on digital off-axis Fresnel holographic interferometry for measuring the continuous bending deformation of the object with a large displacement load has good repeatability and stability.

To reduce the system dividing error of a grinding machine in gear grinding and to improve the machining accuracy of gears, the relationship among the dividing error of grinding machine, gear eccentricity installation, and the pitch deviation was analyzed, and the calculation method for dividing errors of the gear was obtained. By adjusting the grinding machine according to the calculated dividing error, the dividing error of grinding machine and the cumulative pitch deviation of the gear were decreased and the manufacturing accuracy was enhanced. The method was verified by taking the flat-faced wheel grinding machine Y7125 as an example. Firstly, a mathematic model on gear eccentricity installation and profile deviation was established to figured out the amplitude and phase angles of gear eccentricity installation. Then, based on the relationship among gear eccentricity installation, the dividing error of grinding machine and the pitch error, the value of dividing error was obtained. Finally, the indexing plate of grinding machine was adjusted and calibrated according to the computed dividing error. The experiment demonstrates that the dividing error has been reduced from 17.7 μm to 3.3 μm, and the cumulative pitch deviation of the machined gear is lowered from 46.9 μm to 11.5 μm. Furthermore, the accuracy of pitch is up to grade three. The results prove that this method can be used to reduce the dividing error of grinding machine effectively, so as to reduce the cumulative pitch deviation.

As the integral carbon fiber slice for a locking device is not easy to disassemble and the one-off locking device can not repeat locking/unlocking in a magnetic bearing flywheel, a novel repeated clamping locking device based on a separate elastic slice as release mechanism was presented. The composition, operating principles and the scheme of elastic slice for the device were introduced. To be equivalent the elastic slice for a cantilever beam-mass mode, the static and dynamic analysis was performed for the device. Upon this, the structure parameters of high sensitivity were selected as design variables, and the structural strength, unlocking force and the first resonance frequency were concerned. Then, the software of multidisciplinary design optimization (iSIGHT) was used for the optimization of elastic slice. The results indicate that the total mass of elastic slices has been reached to the minimum of 207 g corresponding to 10 elastic slices, which is reduced by 56.6% compared with initial mass of 477 g. According to optimization results, a locking device was manufactured and it is verified by sine-swept vibration and random vibration. The verification shows that the locking device can protect magnetic bearing flywheels and has great significance and values for space applications of magnetic bearing flywheels.

On the basis of femtosecond laser cutting and micro electric resistance slip welding,a forming process named Micro Double-staged Laminated Object Manufacturing(Micro-DLOM) was proposed to fabricate a complex 3D micro-structure,and the feasibility of the forming process was demonstrated by fabrication of a complex 3D micro-cavity mold. Firstly, 0Cr18Ni9 stainless steel foils with the thickness of 10 μm were cut by a femtosecond laser to get a 2D microstructure under a femtosecond laser power of 110 mW,a cutting speed of 0.1 mm/s and the cutting compensation quantity of 0.75 μm. Then, the influence of laser power, cutting speed on cutting precision was analysed,and the foils were welded together to get the 3D microstructure.For further study, the weld-zone was analysed by X-ray Diffractometry(XRD) and it was found that the phase of weld zone has not been changed but the content of phase changed. Compared with UV-LIGA,the Micro-DLOM can fabricate the 3D micro-structure with a free-form surface and the unrestricted ratio of depth to width. Moreover,the thinner the stainless steel foils the, the higher the processing accuracy is. Compared with femtosecond laser ablation,the Micro-DLOM only needs to cut every layer’s outline and has a higher forming efficiency. Compared with micro-EDM,the 3D micro-structure fabricated by Micro-DLOM has a large surface roughness, but it needs not fabricate different microelectrode faces and can fabricate the 3D micro-structure with unrestricted ratio of depth to width.

For the low accuracy of image reconstruction in Electrical Capacitance Tomography (ECT), a image reconstruction method for the ECT was proposed based on the particle filter algorithm. Firstly, the principle of image reconstruction of the ECT was analyzed. Then, the search process of the optimal solution for image reconstruction of the ECT was described as a system state estimation process, and a state space model was established. Furthermore, to obtain the minimum variance estimation of image reconstruction, the image reconstruction result of Linear Back Projection (LBP) algorithm was taken as the initial state, and the optimal weights of random samples obtained from the state space were calculated by the measured information. Finally, the simulation experiments with five different flow regimes were performed. The experiment results show that the average image error of reconstruction results by proposed method is 42.93%, and the average correlation coefficient with the original image is 0.813 9, which is much better than corresponding indicators obtained by LBP algorithm, Landweber iterative algorithm and IMNSNOF algorithm. In conclution,the image reconstruction method with high efficiency and accuracy can provide a new way for ECT research.

As conventional imaging systems suffer from the excessive noise from Analog-digital Converters(ADCs) at low signal levels,this paper proposed an imaging method based on Geiger-mode single photon counting Avalanchen photodiode(GM-APDs) to realize all-digital detection of weak optical signals. The photon response model for the GM-APDs was established,and the performance of GM-APDs with dead-time effects was analyzed by using Markov renewal process. Then,the relationship between the digitlal pulse frequency measured by GM-APD and the input photon rate was deduced.Furthermore, a 2D scan imaging system was also built to verify this method. In the experiment, the photon counting images with different input photon rates were obtained. By using standard mutual information to assess image quality, it is demonstrated that the experimental system can achieve visual imaging with an input photon rate of 3.0×104 count/s, and the value of standard mutual information is over 0.5 with 2.7×105 count/s. It concludes that this system can realize photon counting imaging at low signal levels efficiently.

To prepare a lunar local base map for the lunar orbiter scene aided navigation and landing,the preparing method and related problems for the lunar local base map were researched in this paper. Based on real data from Chang-E 2 mission, error generation and restriction ways for the local base map were analyzed combining with constraints from measurement, tracking and navigation. A set of algorithm for preparing the lunar local base map was proposed according to the global base map by Lunar Reconnaissance Orbiter Camera(LROC) in LRO mission. Experimental results show that pixel features from the generated local base map are consistent with corresponding features from Chang-E 2 orthographic projection images,the maximum coordinate location error by projection is 7.065 1 m, and the distortion error is 6.18 m for the observing map size in 20 km×20 km. These results meet the precision requirement of the scene aided navigation for the lunar orbiter very well.

In consideration of the affects of rainfall on the radar wave propagation and wave parameter inversion in the sea cluter remote sensing by a radar, a new method combined quality control with the three-dimensional evaluation parameters of surface roughness and signal-to-noise ratio(SNR) is proposed to identify and deal with the rain data to improve the parameter accuracy. Firstly, it analyses the influence of the rainfall on the radar remote sensing and the characteristics of sea clutter,and uses the quality control to identify the data available or not. Then, according to the change trend of the three-dimensional evaluation parameters of surface roughness of radar images and SNR, the reasons that radar images are unavailable are determined and those images affected by the rainfall are identified. Finally, those images which are not seriously affected by rain are chosen to be filtered in frequency domain, and the inversion results with and without filtering are compared with the references.Experiment results show that the relative error of wave period has improved by 19.13%, and the measurement error of wave direction has decreased by 10.54 °. This method can distinguish the rain and non-rain data, and can deal with rain data effectively to improve the accuracy of inversion results.

An optical fiber transmission system was designed to implement the long-distance and real-time transmission of traffic guidance image data. To overcome the defects of traditional optical terminal machines,a complete system architecture was built according to the needs of the transmission system. The design ideas of a physical layer and a data link layer were analyzed based on Ethernet relative protocol, some design principles of the important modules were also given,then the memory addressing and bandwidth estimation were calculated in details. The test results show that the image data with a maximum resolution of 1 024 pixel×768 pixel, and refresh rate of 60 Hz can be transferred in a single optical fiber in real-time with a maximum transmission rate of 1.5 Gbps and the distance of 5-10 km. Compared to the original system,the proposed system reduces additional optical equipment and the fiber utilization rate is increased by 80%. Moreover,the cascade function of the receiver end has reduced the laying costs.With reliable performance, the system can implement the transmission task of real-time image data from a traffic command center to the guidance LED display in most of the cities.

To improve the efficiency and accuracy of calibration in frequency domain for a distributed electromagnetic receiver, a calibration method based on multi-frequency pseudo-random signal was proposed and the generation and detection of the signals were investigated. According to the analytical expression of multi-frequency pseudo-random signals, the amplitude and distribution characteristics of the main frequency were analyzed,and a high-precision bipolar calibration source was produced through a Field Programming Gate Array(FPGA) to achieve the encoding synthesis of pseudo-random signals. Based on the noise suppression principle of correlation detection, an iterative method with multiple times for the amplitude and phase of a noisy multi-frequency calibration output signal was given,then it was validated by a simulation. Finally, the acquisition channels of the distributed dual-channel electromagnetic receiving system and a magnetic field sensor were calibrated actually. The results indicate that the amplitude error and the phase error are less than 2% and 1°,respectively, while the outside noise is not greater than the calibration output signal. The calibration method is fast, accurate and can be used in the frequency-domain calibration of distributed electromagnetic receiving systems in various field environments.

As traditional rotating laser construction can not give all considerations to the speed, range and the precision of leveling, this paper developed a new self-leveling mechanism to solve the problem above mentioned. Firstly, by improving the angle sensor in a traditional rotating laser construction, a kind of electronic bubble with the compensative function was designed to meet the accuracy requirement. Then, based on the PID controlling method, a closed loop control system for the self-leveling was designed, while the fuzzy control method was induced to the index of leveling speed. Finally, the general layout of the system was optimized, and the range of self-leveling was enlarged. The experimental result indicates that the leveling accuracy is 10″ and the leveling time is less than 10 s while the inclining angle is from -10° to +10°. In conclusion, the new construction has the characteristics of higher leveling precision, larger leveling ranges and faster leveling speeds as compared with the traditional one.