Direct wavefront gradient algorithm directly establishes correspondence between measurands of the wavefront sensor and response characteristics of the deformable mirror. The voltage can be directly calculated by the algorithm. We use Hartmann wavefront sensor with 64 sub-apertures to detect the distorted wavefront. Based on the hypothesis that of deformable mirror is the weighted addition of the influence function, each of the voltage values applied on the drive is solved by the algorithm. The simulated 32 units of deformable mirror can be controlled and then distorted wavefront can be restored. The simulation result shows that direct wavefront gradient algorithm can effectively adjust the distorted wavefronts.

With the characteristics of high sensitivity and low noise, balanced homodyne detection technique has been one of the main methods in quantum noise measurement. Based on the Kirchhoff's law, a balanced homodyne photoelectric detector with two-stage amplification is designed and studied. The differential photocurrent of two similar photodiodes is primarily amplified by a trans-impedance amplifier, and then sent into the secondary differential amplifier. Experimental results show that the saturation power of this detector is 5 mW, and the signal response bandwidth is about 140 MHz. When the input laser power is equal to 2 mW and the frequency is lower than 30 MHz, the optical shot noise is 10 dB larger than the electronic noise. Near 20 MHz, the common mode rejection ratio of the detector could reach 55 dB.

A 2.0 kW six-axis robot fiber laser cutting system is used to study the impact of cutting process parameters on the kerf width, bevel angle, cutting surface roughness and incision microscopic state of 6 mm thick steel plate. The results show that the optimum cutting process parameters are cutting speed about 2.0 m/min, auxiliary gas pressure 14.7 N/cm2, focusing lens focal length f=200 mm, laser spot diameter 0.3 mm, defocusing amount +4~+5 mm, cutting nozzles diameter 0.8 mm. Under the optimum cutting process parameters, the kerf width is 0.5~0.6 mm, the cutting tilt angle is 0.2°~0.5° and the cutting surface roughness is small. Cutting surface is divided into two different parts because of the top and bottom sections show different flatness. The temperature in the bottom is higher, the gap between oxidation rate and cutting rate is greater than that on the top, so the flatness is poor. Compared with CO2 laser cutting, fiber laser cutting surface roughness is better and the cutting power efficiency is increased by 2.6 times.

Optical burst switching (OBS) is a promising solution for the next generation backbone internet which can exploit the hugy bandwidth of dense wavelength division multiplexing(DWDM) technology and the flexibility of electronic switching. An improtant issue in OBS technology is burst contention which causes performance degradation. The optical buffer resolution based on segmentation segments burst firstly, and then the segmented burst is buffered. The wavelength conversion conflict resolution based on segmentation segments burst firstly, and then the segmented burst is wavelength converted. Comparison between the two contention resolutions is made. The result of comparison shows that when the network load is high, the optical buffer conflict resolution based on bust segmentation can efficiently reduce the burst loss probability. When the network load is low, the wavelength conversion conflict resolution based on bust segmentation can efficiently reduce the burst loss probability.

In order to acquire temperature-insensitive optical filter which also has good channel isolation, a novel Sagnac loop cascaded . lter based on highly birefringent photonic crystal fiber (HiBi-PCF) is proposed. Theoretical analysis and numerical simulation are conducted to the two-order cascaded Sagnac loop filter with Jones matrix theory. When the length ratio of the two segments of HiBi-PCFs in cascaded filter is 2:1, the full-width at half-maximum (FWHM) of transmission spectrum is 0.4 nm, which is only 1/3 of that of the single Sagnac loop filter, so as to effectively improve the filter channel isolation degree. The results show that this kind of filter possesses a good filtering effect and is also insensitive to the temperature change, which can be applied to 50 GHz dense wavelength division multiplexing (DWDM) system.

In recent years, the fiber optical communication system that uses optical soliton to transmit information has shown its advantages in long transmission distance and large capacity. It will play a great role in the new generation of communication and business. The transmission of optical soliton in optical fiber obeys the nonlinear Schr.dinger equation. In this paper, three commonly used methods for solving nonlinear Schr.dinger equation, i.e., Jacobi elliptic function expansion method, trigonometric function assumption, and trial function method, are analyzed and compared from the aspects of seeking traveling wave transformation, solving process and physical significance of solution, and so on. Moreover, we introduce the newly proposed (G′/G) expansion method. Calculation shows that (G′/G) expansion method is easier than the other three methods in traveling wave transformation and calculation process. Besides, it also has relatively rich solutions. Therefore, this expansion method solving the nonlinear Schr.dinger equation and the related equations has a wide application prospect.

The characteristics of distributed side-coupled cladding-pumped fiber laser are studied with simulation based on a coupled rate equation model. Both the distributed side-coupled cladding-pumped fiber lasers and the end-pump double-cladding fiber lasers are simulated, and the distributions of the pump light and laser of the two models are given out. Then the optimum fiber length is discussed. The results show that the pump light in the signal fiber of distributed side-coupled cladding-pumped fiber is well-distributed and the thermal load of the two ends is released. The laser is produced linearly so that the heat is dispersed to the whole fiber. It is a great advantage to be applied to high power fiber lasers and provides a new road to the higher fiber lasers.

In order to obtain higher performance in space-to-ground optical communications, the acquisition, pointing and tracking (APT) system needs to have high precision. The vibration of satellites is the most important factor which affects the accuracy of APT. The suppression effect of traditional feedback control is bad in the mediumto-high frequency range of satellites′ vibrations. For this situation, adaptive algorithm is introduced into feedforward control and two kinds of adaptive feedback composite algorithms based on the least mean squares (LMS) and recursive least squares (RLS) algorithms are designed. Feedback control, LMS composite control and RLS composite control are verified by simulations. The results show that the effect of adaptive feedforward composite control is better for the medium-to-high frequency vibrations and the use of adaptive algorithms with faster convergence and higher steady-state precision can improve the suppression effect.

A digital coding and decoding method on recoding Fresnel diffraction distribution of multiple threedimensional (3D) objects in the same hologram is discussed. Firstly, fast Fourier transform algorithm is used to calculate the complex amplitude distribution of the three- dimensional objects in the holographic plane, and then the object wave data are preprocessed to avoid digital spectrum aliasing, and finally different carrier frequency coefficients are controlled to produce interference hologram. The method of digital reconstruction is based on extracting effective spectral components in the digital spectrum hologram and then calculating discrete Fresnel inverse transform to rebuild the original three- dimensional objects. The simulation results show that the proposed method can record multiple three- dimensional objects with different production parameters at the same time and has good reproduction quality. The hologram production parameters such as wavelength, reproduction distance, carrier frequency coefficients can also serve as a key to realize encryption storage for multiple three-dimensional objects.

Technique of combining time- average digital holography with digital imaging to measure the amplitude field of object is proposed, the imaging lens is introduced into the optical system of time- average digital holography, and the vibration of large objects can be analyzed by time- average digital holographic technique. The basic theory of this technique is described, the related optical system is designed, and the results are verified by experiments with the help of a round piezoelectric ceramic piece.These experiments show that the digital holographic interferogram recorded and reconstructed by digital imaging time- average holographic technique agree well with that recorded and reconstructed by traditional time- average holographic interferometry under identical condition. Error of amplitudes of both obtained by calculating through comparisons is very small.

Most existing feature point tracking algorithms only consider two adjacent frames at a time and neglect the feature information of previous frames. In this paper, based on the original Kanade-Lucas-Tomasi (KLT) algorithm, a new feature tracking method is presented that learns an eigenspace representation of training features online, and finds the target feature point with Gauss-Newton style search method, effectively avoiding the troubles introduced by target dimension, large angular changes and occlusion. By analyzing the performance of the algorithm by the actual image, it is compared with other algorithms. Meanwhile, we design a hardware platform using the eight-core digital signal processor (DSP) TMS320C6678 as the core processor, in combination with field programmable gate array (FPGA) digital video image acquisition device. A series of strategies of the algorithm optimization are proposed. Finally, tracking of moving target is achieved by the realtime transmission of video images.

Normal distribution transform (NDT) algorithm is a point cloud registration algorithm applied in simultaneous localization and mapping (SLAM). According to the characteristics of terrestrial laser scanning (TLS) technique, we propose an improved NDT algorithm based on speeded up robust feature (SURF) algorithm so that it can be applied conveniently in TLS. In this algorithm, firstly the corresponding relation between the point cloud and the image is created for the point cloud visualization; the feature points are extracted from the image by using SURF algorithm and the matching feature points are identified; according to the corresponding relation, the transformation matrix is calculated, and the initial registration of point clouds is completed. In the NDT, the initial matrix is set as a unit matrix, and the point clouds are divided into three-dimensional voxel grids and registered precisely by the probability distribution function. The experimental results show that this algorithm is not only applicable to the registration for TLS, but also exhibits higher registration accuracy and less calculating time, and it has especially a good registration effect for the point clouds with different resolutions.

We propose an algorithm to fuse infrared and visible images based on variational method and gradient enhancement. Firstly, the gradient features of infrared and visibe images are fused in an adaptirely weighted way, and the original fused gradient field is obtained. Then the enhancement model for gradient features is constructed to get the enhanced gradient field of fusion image. Finally, the fusion problem is transformed to an optimization problem by using variational method. Thus a fusion image with the gradient field approaching the preriously obtained enhanced gradient field can be achieved. Experimental results show that, in comparison with existing fusion algoritnms based on multi-resolution concept such as Laplace decomposition, wavelet transform and variation-based fusioin, our algorithm results in the maximal gradient feature and the best visual effects. The effectiveness of the proposed algorithm is proved.

In order to improve the recognition ability of joint transform correlator in complex background, we propose a joint transform correlator based on wavelet transform edge detection. Multi-scale analysis of wavelet is used to detect the joint image edge, so that the edge can keep more details, and the ability of target recognition in complex background can be improved. Computer simulations and optical experimental results show that, our proposed method can enhance the intensity of the correlation peaks and improve the ability of correlation recognition greatly.

A 3D reconstruction method based on linear-structured light stripe and binocular vision is proposed. The key points are extracted by the contour curvature, and are used to extract the normal vector of the contour. With the characteristics of the skewness of the distribution, the stripe center is extracted based on the barycenter method. The 3D reconstruction process is finished while the image coordinate of the welding seam are transformed to the word coordinate. The experimental results show that this method is quick and accurate, and is suitable for the requirements of the structure light welding system.

Shadows caused by tall buildings and trees and color distortion in visible image make that traditional color quantization cannot accurately describe the spectral difference of different objects on the ground. This defect declines classification accuracy finally. In view of shadows and color distortion problem in the lowquality visible image, we put forward an improved method. On the first stage of our algorithm, the problem of missing spectrum information caused by shadows is solved through sampling, analysing, and extracting shaded regions by double-threshold method and then classifying different kinds of shaded regions by object-oriented method. On the second stage, we obtain accurate areas of trees by fusing discriminative information [lidar intensity, digital surface model (DSM)] in order to compensate incomplete extraction caused by color distortion. The experimental results in comparison with ground truth obtained by manual work show that the classification accuracy is improved obviously compared with the results obtained by traditional Dempster-Shafer (D-S) fusing method.

The characteristics of correlation for pseudo-thermal light source have much effect on the quality of image in ghost imaging. The correlated characteristics of pseudo-thermal light have relations with contrast, signal to noise ratio and resolution. On the same condition of experiment, the higher the peak value of the twoorder correlation, the higher the contrast of the image, and the better for the randomness of the pseudo-thermal light, the higher for the signal to noise ratio of the image. Recently, varieties of schemes for correlated imaging have emerged, and pseudo-thermal light correlated imaging based on space light modulator（SLM） has good prospect. The theory of pseudo-thermal light based on different modulation is presented, by which we have simulated the two-order correlation of pseudo-thermal light when different modulations have been sent to SLM, and a conclusion has come that when SLM is modulated by the mixture of phase and amplitude, the peak value of the two-order correlation is the highest, especially when the probability distribution for amplitude is Rayleigh distribution and the phase is evenly distributed between 0~2p, and the peak value of the two-order correlation can come to 2, and the characteristic of pseudo-thermal light is ideal.

In order to obtain a clear retinal image resolution of the human eye, the deformable mirror in adaptive optics system must be able to track and compensate the eyes aberration information in real time. The capability of wavefront aberration correction, especially the dynamic wavefront aberration, is not only depending on the performance of the deformation mirror and other hardwares, but also closely related to the control algorithm of adaptive optics system. Without increasing hardware complexity, a human eye aberration correction optimal control model based on Kalman filter and linear quadratic Gaussian (LQG) control is proposed. Firstly, the dispersion of adaptive optics system is analyzed and it is shown that the study of adaptive optics system under the discrete model is feasible. Then, the LQG optimal control model based on the Kalman filtering is established, and the aberration correction algorithm based on LQG optimal control model is proposed. Finally, the simulation experiment demonstrates the feasibility and effectiveness of the proposed algorithm.

An interferometric method for the absolute testing of optical flats, three- flat testing, is studied. This method needs three flats, which are combined in pairs in different positions, and measurements yield a vertical profile of data and a horizontal data profile along the diameter of the reference flat. According to Matlab and VC mixed programming, three- flat test of mutual inspection procedures is designed to quickly calculate experimental data with the help of an interferometer. Experiments are done to achieve high accuracy flatness measurement, and the calculation error is 3% relative to the Zygo software.

High precision bearing is a kind of cylindrical parts. A machine vision based online detection system is designed and implemented to meet the need of high curvature surface defects detection of cylindrical parts. During the measurement, a special light source and a lighting system are used to solve the problem of the reflections on the metal surface. Through the combination of optical systems and mechanical rotating platform, cylindrical parts are imaged by the optical system in the process of rotation, then a complete cylindrical surface image can be acquired. Micron surface defects and dimensions of bearing can be detected after using the fast image processing technique. Through the analysis on the morphology of surface defects, the type of defects can be determined. Experiments show that the proposed system has the features of high efficiency, high accuracy and ease of use. It can effectively meet the needs of high precision bearing detection and dimension online detection.

Based on the extended Huygens-Fresnel principle, the propagation expression of Hermite-cosine-Gaussian beam through the negative refractive index materials slab is derived and the numerical calculations are performed. The calculated results show that the negative refractive index of materials slab changes the position of the Hermite-cosine-Gaussian beam focusing, and the beam parameters of Hermite-cosine-Gaussian beam can affect the axial and transverse light intensities. However, the position of the maximum intensity is constant.

The velocity of aerobat can be measured by laser Doppler velocimetry system and its accuracy is seriously affected by the attitude measurement errors. To precicely measure the three-dimensional (3D) velocity, an all-fiber triple-beam laser doppler velocimetry (TLDV) system based on coherent detection principle is proposed. Mathematical model of velocity measurement is described. According to the simulations, it is found that, firstly, effect of the attitude errors on the velocity measurement accuracy should not be neglected; secondly, with the pitch angle changing, influence of the pitch error and roll error on velocity measurement accuracy change; thirdly, the relationship between velocity accuracy and roll error is linear, while that between the accuracy and pitch error is nonlinear. The conclusions can be used for the design and velocity error correction of laser Doppler velocimetry system.

A model for laser scanning confocal microscopy with three media is given to calculate the point spread functions. (PSFs) According to Hammoum’s representations, we obtain the representations for three media. The effect of the dipole orientation on the PSFs is discussed. Several PSFs are compared. Then we analyze the effects of the pinhole on the PSFs, the energy collected and the signal to noise ratio. Calculations show that the detection PSF for the dipole averaged over all orientations is better than those for the dipoles along the x axis and the z axis. The total is smaller than the illumination PSF and the detection PSF. The total PSF after the pinhole diminishes as the pinhole decreases. The curves of the energy collected for the circular pinhole and the square pinhole are similar, but the signal to noise ratio for the circular pinhole is better than that for the square pinhole.

All-optical atomic magnetometer with high sensitivity is an important technique to detect weak magnetic field. The Cs vapor cell is the core component of the atomic magnetometer. He gas is used as buffer to reduce diffusion to the walls where spin coherence is rapidly lost. The buffer gas decides the pump light frequency. In this work, we analyze the principle of all-optical Cs atomic magnetometer and the influence of pump light frequency on the sensitivity of all-optical Cs atomic magnetometer as the buffer gas pressure is about 1.333×104 Pa. Rate equation is used to calculate the orientation of the atomic spin for different pump light frequency. The result shows that the maximum sensitivity appears as the pump light frequency and the probe light frequency are locked to Cs D1 transition F =3 → F′ = 4 and Cs D2 transition F =4 → F′ =5，respectively.

Numerical simulations based on the finite-difference time-domain technique are performed to investigate the transmission spectrum of defects in the two-dimensional (2D) rectangular lattice photonic crystal. The results show that the defect modes within the band gap are created by either decreasing or increasing the radius of normal GaAs rods and there exists a one-to-one correspondence between the two defects which possess different radius but similar resonance. In addition, the defect modes generated by decreasing size are single modes while those created by increasing size are doubly degenerate modes or multimodes. More importantly, the former defects are insensitive to the intensity of electric field while the latter ones exhibit strong dependence on the intensity of electric field. The conclusion might be used in the design of photonic crystal devices based on point defects.

A kind of tracking error of shipboard electro- optical tracking system is caused by the rotation of vessel. In order to solve this problem, a method using coordinate transformation based on quaternion is proposed. By analyzing the viewing field in each coordinate system, the effect of vessel attitude on the viewing field is deduced. Meanwhile, the effect of the installation misalignment on the viewing field is deduced too. The result provides a theoretical basis for real-time despinning of shipboard electro-optical tracking system.

Stimulated Brillouin scattering (SBS) is a third-order nonlinear optical effect. Stimulated Brillouin scattering phase conjugate mirror (PCM) is a self pumped PCM based on SBS. SBS-PCM can compensate wavefront distortion caused by system thermal aberration and material inhomogeneity and improve laser beam quality. The applications of SBS-PCM are becoming more and more extensive. We review the typical laser configuration with SBS-PCM. Research progress in this field at home and abroad is briefly summarized. Some problems to be resolved are also put forward.

Precision moving tables are playing an important role in machine tools and measuring machines. In order to achieve higher motion accuracy, it is necessary to measure the motion errors of the moving table and feed back them to control the motion. In the six motion errors, rolling error is the most difficult one to measure. Several developed methods of rolling angle measurement are described in detail． The principle，the status of development and the application situations of each method are displayed．The advantages and disadvantages of them are compared．The trends in the fields are discussed.

Due to the robust single- mode performance, mode- distortion- free splicing and compact coiling, chirally-coupled core (CCC) fiber, as a novel fiber, has provided a new method for the development of the next generation high peak power and high energy fiber laser system and aroused wide public interest over the recent years. In this paper, we describe the chirally-coupled core fiber structure and mode coupling theory in this fiber. Recent development and some important applications about the novel fiber are also reviewed.

We review the experiment design and development of the lunar laser communication demonstration (LLCD) on the Lunar Atmosphere and Dust Environment Explorer spacecraft launched by the National Aeronautics and Space Administration (NASA) of USA on September 6th, 2013. When the space terminal is in orbit, bidirectional communications are performed with the main lunar laser communication ground terminal or with the European Space Agency's lunar laser communication optical ground system, but only downlink communications are performed with the Jet Propulsion Laboratory's lunar laser communication optical communications telescope laboratory (OCTL) terminal. Besides laser communication, bidirectional time-off light measurements are performed by LLCD system with sub-centimeter ranging accuracy. The future NASA laser communication relay demonstration will be developed on the basis of LLCD system. Finally we discuss the knowledge learned from LLCD.

A new method for detecting carbaryl residues in duck meat is proposed using three- dimensional fluorescence spectroscopy and partialleastsquares regression (PLSR),according to the carbaryl derivatives with strong fluorescent properties. The two- dimensional contour spectrograms of samples are analyzed, the results indicate that the characteristic peaks of carbaryl and duck meat are separated obviously, which located at 300/365 nm and 320/460 nm in carbaryl-duck systemrespectively. Prediction model of carbaryl contents in the duck meat is established using PLSR, the coefficient of determination (R2) and the root mean squared prediction error (Prms) are 0.9883 and 3.103, respectively. The results show that the method which combining three- dimensional fluorescence spectroscopy with PLSR could be used to measure thecarbaryl residue in duck meat,it has the advantages of rapid and accuracy determination, and an effective means is provided for detection of pesticide residue in duck meat.

Using direct ultraviolet-visible (UV-visible) spectroscopy method to detect water quality parameters has some advantages such as rapid detection speed, low cost, no secondary pollution, on-line and in-situ measurements. However, the detection system based on this method has been difficult to promote be cause of the limitation of to the accuracy of spectral detection and the cost of equipment. In this paper, we use the industrial-grade USB2000+ spectrometer and pulsed xenon light source of Ocean Optics to build a low- cost, rapid water quality spectral detection system. Furthermore, on the basis of a comprehensive analysis of the system noise sources, we use the soft thresholding wavelet packet method to denoise the raw spectral data. In order to effectively evaluate the denoising effect, we use scientific-grade spectrometers QE65000 of Ocean Optics with stable deuterium tungsten light source to build a standard spectral detection system, and carry out UV-visible absorption spectrum acquisition on the same sample solution. Experimental results show that the proposed system can capture the raw spectral data stabl and effectively. Then using soft thresholding wavelet packet to denoise the original data, on the premise of retaining water samples UV-visible absorption spectrum characteristics, various noises of the original spectra are effectively removed and the signal-to-noise ratio, which makes a foundation for the low-cost spectral detection device for the analysis of water quality parameters.