In order to clarify the effect of process parameters on weld formation of laser-MAG hybrid welding under full penetration state, full penetration welding process experiments at high welding speed had been carried out on 6 mm AH36 high strength steel by hybrid laser-arc welding with disc laser. The effects on the weld formation and mechanical properties of wire feeding speed、laser power、welding speed were studied. The results show that within a certain range, increasing the wire feeding speed or laser power can reduce the back hump. When the laser power is 6.5 kW, the wire feeding speed is 8 m/min, and the welding speed is 2.5 m/min, the weld formation is good and there are no welding defects. The hardness of weld metal is greater than that of the base metal. The tensile strength of the welded joint is greater than that of the base metal.

Underwater repair in the original state is one of the preferred schemes for the spent fuel pool and in-containment refueling water storage tank of nuclear power plant. Using S32101 duplex stainless steel base metal and ER2209 stainless steel welding wire for the spent fuel pool of the third generation nuclear power plant, the experimental exploration of V-groove laser wire filling welding repair process is carried out, and the weld performance is comprehensively tested. The main conclusions include: the composite welding process of laser wire filling welding and laser reheating can obtain good weld formation, The weld structure is mainly composed of ferrite and austenite;According to the nuclear power construction standard, the room temperature tensile, high temperature tensile, low temperature impact, ferrite content and intergranular corrosion resistance of the weld meet the requirements; The research conclusions lay a good foundation for the research of underwater welding technology of spent fuel pool and in-containment refueling water storage tank in nuclear power plant.

Using laser cladding technology, a Ni-based WC cladding layer containing rare earth Y2O3 was prepared on the surface of 40Cr10Si2Mo steel. Compare the effects of different Y2O3 content on the macro morphology, microstructure, phase composition, microhardness, and friction and wear properties of the cladding layer. The results show that: Y2O3 can enhance the fluidity of the molten pool, reduce the first height of the multi-pass cladding layer, optimize the structure of the cladding layer, and purify the cladding layer; the addition of Y2O3 can improve the hardness and resistance of the cladding layer abrasion. Compared with the cladding layer without Y2O3 added at 0.5%, 1.0%, and 1.5%(mass fraction), the average hardness of the cladding layer is increased by 10.1%, 22.3%, and 18.4%, respectively, and the wear amount is decreased respectively 9.7%, 26.7%, 12.7%, when the addition of Y2O3 is 1.0%, the resulting cladding layer has the least defects and the best wear resistance.

In order to optimize the Fe-Ni-Cr powder laser cladding process parameters and get the best process of microstructure and properties of cladding, laser power, scanning speed, powder feeding speed and away from the focal design of four factors three levels orthogonal test L9(43) and arrange the experiment, the surface morphology, dilution rate and microhardness as evaluation indexes, through the comprehensive scoring method to determine the best process parameters, and analyze the optimization of process under the structure morphologies of the cladding layer, microhardness and friction and wear properties. The results show that the optimal process parameters are: laser power 2 400 W, scanning speed 5 mm/s, powder feeding speed 20 g/min, defocusing capacity +5 mm; The optimal cladding layer consists of fine cellular crystals (the grain size is about 8 μm) and columnar crystals (the grain size is about 17 μm). The substrate consists of ferrite and pearlite with a grain size of 27~50 μm.The average hardness of cladding layer is 633 HV, which is 3.6 times that of substrate. The average friction coefficient of the cladding layer is 51% of the base material, and the wear loss is 37.1% of the base material, indicating that the friction reduction and wear resistance of the cladding layer are good.

Ni35+11%WC powder was used to enhance the surface performance and prolong the service life of 45 steel gear, providing reference for surface modification of 45 steel gear. Coatings were prepared on 45 steel surface with different laser power and scanning speed by synchronous powder feeding. By comparing the macroscopic morphology, geometry size and dilution rate of different coatings, the hardness under different scanning speeds was tested, and the XRD phase and microstructure of the coatings and sections were analyzed by XRD diffractometer and metallographic microscope. The results show that when the laser power was 900 W, the scanning speed was 2 mm/s, and the powder feeding rate was 1 r/min, the coating appeared columnar dendrites and isometric organization composed of γ-(Ni, Fe) solid solution, Mn7C3, Cr23C6, W2C, W and Cr3C2 phase composition. The metallurgical combination between the coating and the substrate was good, The highest hardness of the coating was 786.6 HV(2 N loading force), and the average hardness was 737 HV, The average hardness of the coating was 2.81 times higher than that of the substrate.

The laser cladding technology was used to prepare the coating on the surface of 45 steel by adding different content of La2O3 into 304L powder. The microstructure, phase composition, microhardness, friction and wear properties of the coatings with different contents of La2O3 were compared. The results show that rare earth can accelerate the fluidity of molten pool, increase the compactness of microstructure, improve the hardness of cladding layer, and reduce the friction coefficient and wear loss. The results show that the coating with 0.5%, 1.0% and 1.5%(mass fraction) La2O3 has the best performance, the grain structure is finer and more uniform, the average hardness is increased by 20.6%, and the friction coefficient and wear loss are decreased by 14.2% and 24.9%, respectively.

When etching monocrystalline silicon with UV laser, several action mechanisms codetermine the etching result, such as thermal conduction and plasma effect. Thermal conduction leads to material melting and evaporation, plasma effect leads to material breaking and throwing-out. Analyses theoretically the role of relevant process parameters in every action mechanism, tests respectively the key process parameters, ultimately obtains the relationship between the optimal process parameter and the best etching quality. On the basis of analysis and test, the guiding principle is obtained which is used to guide the experiment on how to get the best etching quality. The result shows the guiding principle is reasonable, and the optimal process parameter of etching monocrystalline silicon is achieved. The experiment shows, the power density of single pulse and frequency determines the slot’s depth and width, both power density of single pulse and scanning speed determine the shape and surface quality of the slot.

Fe-based amorphous ribbon is a new structural and functional material with excellent magnetic properties, wear resistance, strength and hardness and so on. Fe78Si9B13 amorphous ribbons were cut by ultraviolet nanosecond laser with 355 nm wavelength. The effects of laser pulse frequency, pulse width and cutting speed on the width of the slit and the width of the heat affected zone were studied. The results show that Increasing the cutting speed can reduce the slit width and the size of the heat-affected zone, and improve the cutting efficiency within a certain range. As the frequency increases, the width of the slit and heat-affected zone decreases. With the increase of pulse width, the width of the slit decreases, but the width of the heat-affected zone increases. The results of thermal analysis showed that some samples were crystallized in the heat-affected area.

The structure of parts produced by additive manufacturing(AM) technology is complex, and usually with overhanging feature structure and symmetric structure. To ensure the mechanical property of symmetric structure and avoid the molding defects caused by overhanging feature structure, it is necessary to extract the feature structure from the part model for special process control before molding. This paper combines the layer upon layer characteristics of part model and the grid information of STL model, then proposes a calculation method of the cantilever inclination angle to effectively identify the overhanging area; and design the box of space surface to accurately extracts the structure and accomplish the operation by 3D modeling software. Finally, a typical symmetric part verification method is selected, and printed it out with better molding quality by SLM additive manufacturing technology. The results show that the method is feasible and effective, and improve the processing capacity and formed quality of parts.

The robust design method is applied to laser microdrilling to overcome the quality fluctuation caused by process uncertainty. Considering the stochastic uncertainty of noise factors (processing time, gas pressure, et al.) to affect the controllable pulse energy, pulse width and defocus in the laser hole-punching process, the exit diameter of hole is analytical robust optimal design. Firstly, through orthogonal experimental design, the quadratic regression equation between quality index and parameters is established by using response surface model. Secondly, the expectation and variance of index are obtained by using Taylor series expansion, and a robust optimal design model with minimum variance as the objective and expectation as the constraint is established. Finally, combining with optimization algorithm in MATLAB obtains the best combination of process parameters, and comparing with the deterministic optimization, which verifies the good effect of the robust method.

Study on the mechanism of laser polishing of titanium alloy Ti6Al4V is of great significance to improve the surface quality and performance. A nanosecond pulsed fiber laser was used to polish an 8 mm×8 mm local area of the titanium alloy with a bow-shaped scanning path. Polarized light microscope and optical surface profilometer were used to observe the two-dimensional and three-dimensional morphology of polished material surface and measure the surface roughness. The effect of different laser power, overlap rate, pulse width, scanning times, and surface roughness on the surface roughness of titanium alloy was studied. The properties of the polished materials were analyzed by automatic microhardness tester, scanning electron microscope and X-ray diffraction analyzer. The results show that with the increase of the average laser power, the spot overlap rate and the scanning times, the surface roughness of the titanium alloy decreases first and then increases. With the increase of pulse width, the surface roughness of titanium alloy shows a downward trend. The greater the original surface roughness is, the greater the reduction rate of the surface roughness polished will be. The smaller the original surface roughness is, the smaller the surface roughness polished will be. The minimum surface roughness of titanium alloy is 0.164 μm, and the roughness reduction rate is 60%. The microhardness of the polished material was increased 6% compared with the matrix. After polishing, the surface structure of the titanium alloy changes from white equiaxed α-Ti6Al4V to fine needle-like martensite α′-Ti6Al4V.

Femtosecond laser processing has the characteristics of short pulse, high peak power, and small heat-affected zone. Even so, there is still a heat accumulation in the material removal process. The heat accumulation between pulses has a direct impact on the processing quality and the heat-affected zone. In this paper, carbon fiber reinforced resin matrix composites (CFRP) are ablated by femtosecond pulsed laser, and a three-dimensional heat transfer model is used to study the temperature field of the pulsed spot, and then the thermal accumulation effect of the femtosecond laser is discussed. The results show that the pulse energy and repetition frequency have a significant influence on the heat accumulation; the calculated results of the 3D heat transfer model are basically consistent with the experimental results. This 3D heat transfer model can provide references for the control of the heat accumulation effect in femtosecond laser processing of CFRP materials.

The laser direct marking of Aluminum alloy (2024) was carried out on 1060nm MOPA laser. The quality grade and contrast of DM codes at different power levels were studied. The surface morphology of the marking was observed by scanning electron microscopy (SEM), and the composition of the marking surface was analyzed by energy dispersive spectrometer (EDS). Through SEM analysis, it was found that the marking surface material with good quality level of DM code is melted, vaporized and ablated, with a large number of holes and granular substances, while the marking surface material with poor quality grade of DM code is only recast and the surface is wavy; EDS analysis shows that the content of oxygen elements in the marking surface materials with higher DM code quality grade increases, indicating that the melted and vaporized metals undergo oxidation reaction, while the amount of oxygen elements on the marking surface with lower DM code quality grade increases less, indicating that the metal oxidation reaction is less under this condition. In this paper, the ablative threshold of the material is calculated to provide theoretical guidance for the test.

High power fiber laser was used to carry out laser cutting process experiments on 15 mm thick 2A12 aluminum alloy. The effect of defocusing amount, cutting speed, auxiliary air pressure, laser power and other parameters on cutting quality was systematically studied. In the research process, the cutting quality was judged based on the morphology of the section stripes and the morphology of bottom slag. First, through single-factor experiments, the optimal parameter range for defocus, cutting speed, auxiliary air pressure, and laser power is determined; then, the optimal process parameters are optimized by experiment, that is, the positive defocus and negative defocus are compared and selected. The best combination of defocus and cutting speed parameters. For 15 mm thick aluminum alloy laser cutting, the best process parameters are: laser power 9 kW, cutting speed 2 000 mm/min, auxiliary air pressure 1.8 MPa, nozzle diameter 3.0 mm, nozzle height 0.8 mm, and defocus +4 mm.

The influence of layer thickness on roughness, relative density, microstructure and mechnical properties of selective laser melting (SLM) 18Ni300 maraging steel were studied in this work. The results shows that when the laser power and hatching space are constant, the relative density first increases and then declines with the decrease of the laser volume energy density under the layer thickness less than or equal to 50 μm; whereas the relative density gradually declines with the decrease of the laser volume energy density under the layer thickness larger than or equal to 70 μm. At the same time, with the increase of the layer thickness and the decrease of the scanning velocity, the cooling rate gradually decrease during the SLM processing, thus the grain size gradully increase. Through the optimization of the SLM parameters, the dense (≥99.0%) 18Ni300 specimen can be obtained under all layer thicknesses 30~70 μm, the hardness, ultimate strengths and elongation gradually declines with the increase of the layer thickness, and the tensile fracture all shows the plastic fracture mechanism.

Laser point cloud data can be used to obtain more accurate terrain data, while the current laser point cloud mainly uses single-band pulse, which cannot provide sufficient and effective spectral information. In this paper, laser point cloud data is combined with the extraction of transmission line corridor information. According to the feature of the transmission line corridor, 3D data of point cloud information is used to identify the feature with different geometric features, and a transmission line corridor automatic recognition technology based on airborne laser point cloud data is designed. Firstly, by calculating the surface feature of point cloud and the dimension feature of neighborhood radius, the transmission line of linear target is selected and extracted. Secondly, the method of cloth filtering is used to distinguish the ground and vegetation point clouds, and a cylindrical model is constructed to determine the tower point according to the prior coordinate information of the tower. Finally, the method proposed in this article is verified through experiments. The results show that the overall classification accuracy is relatively high. Under the identification of four types of features such as transmission lines, towers, vegetation and ground, user accuracy reaches 95.29%, 82%, 95.84%, and 94.3%, respectively, and mapping accuracy reaches 98.54%, 95.64%, 98.3% and 85.38%. The research results can provide certain reference value for the identification of multiple types of transmission line corridors.

The laser acoustic signal has the characteristics of pulse width and frequency width. In a certain range, with the increase of laser energy, the energy distribution in frequency domain remains stable. Wavelet packet technology is used to analyze the acoustic signal characteristics of the target echo signal. In this paper, db4 wavelet base is used to decompose laser acoustic signals. The energy characteristics of decomposed signals are extracted and the energy distribution characteristics of acoustic signals are analyzed. In order to determine the time domain characteristics of the target laser sound signal before and after reflection, the reconstructed signals of different nodes after decomposition are reconstructed, and the correlation analysis between the reconstructed signal and the original signal is conducted to determine the effective filtering frequency band of the signal. The data analysis shows that the wavelet packet analysis method can effectively analyze the transient characteristics of laser acoustic signal, and select the signal filtering frequency band according to the energy characteristic value to effectively filter the signal, which can provide a reference for the research of underwater acoustic target identification.

In order to solve the problems that the existing electronic sensors for measuring the angle of the contact line isolation switch are difficult to obtain electricity and are susceptible to electromagnetic interference, a sensor for measuring the angle of the isolation switch is designed using an optical fiber sensor, using the idea of replacing the curve with straight , The rotation angle of the catenary isolation switch is converted to the optical distance measurement method for measurement, and the curve fitting algorithm is used to compensate for the nonlinearity of the designed optical fiber angle sensor. And install the compensated optical fiber angle sensor together with the high-precision Hall angle sensor on the SBE27.5kV/2000A isolating switch for experimental testing. The experimental results show that: compared with the commonly used BP neural network, the fitting degree of the optical fiber angle sensor corrected by the curve fitting algorithm has increased from 92.47% to 99.94%, and the linearity has increased from 9.66% to 0.84%. The optical fiber angle sensor The accuracy reached 0.677. It shows that the scheme has high accuracy and strong feasibility, and is suitable for monitoring the opening and closing of the catenary isolation switch.

According to the principle of 3D reconstruction of binocular stereo vision, if the dense 3D point cloud data can be obtained, the characteristics of 3D object surface shape can be determined. Therefore, this paper proposes an improved image registration method of BAS. Firstly, SURF algorithm is used to extract the feature points of the image taken by binocular camera, and the feature vector and its corresponding position are extracted from the returned binary or intensity image. Finally, the relationship matrix between the two images is taken as the objective function of the improved BAS to calculate the transformation relationship between left and right images in binocular stereo vision. The two-dimensional point cloud data of the inner surface in one of the images is found by image segmentation, and the corresponding two-dimensional point cloud data is calculated by using the relation matrix, and finally the three-dimensional point cloud data of the inner side is reconstructed. From the comparative analysis of the images, we can find the corresponding points to calculate the relationship matrix, so that the SURF algorithm of image registration can be more accurate by using the rotation translation matrix calculated in this paper.

In the multi-sensor data processing of the Cartographer algorithm, outliers and noise in the point cloud affect the accuracy of point cloud matching, and the accuracy of the pose fusion algorithm is not high. Therefore, an improved Cartographer algorithm based on the hybrid filtering algorithm and the pose fusion algorithm with velocity integral was proposed. First, the selected point measurement was improved to optimize the re-sampling process of the voxel filtering algorithm and improve the filtering efficiency. By introducing straight-through filtering and radius filtering, a hybrid filtering algorithm was proposed to improve the quality of the point cloud. Then, in the algorithm of fusing the observation pose, odometry data and inertial measurement unit data, the pose fusion algorithm with speed integration was introduced to improve the accuracy of point cloud matching. Finally, in the test experiment using the data set to verify the loop detection performance and the localization accuracy of the algorithm, the results show that compared with the cartographer algorithm and the A-LOAM algorithm, the map constructed by the improved algorithm is more accurate and the trajectory error is smaller. Therefore, the algorithm proposed in this paper is feasible and effective for improving localization accuracy and mapping quality.

Traditional ship flat board measurement uses a leather tape to measure manually. This method has low accuracy, large errors and relies on the experience of the surveyor. Since the cutting of straight plates is mostly large plates, the contact measurement method cannot be widely used. The use of embedded line laser vision sensors combined with numerical control machine tools to propose a method for measuring flat plates of large ships can solve the above problems. The sheet is scanned by the line laser vision sensor, and the obtained real-time coordinates of the machine tool and the calibration result of the relative relationship between the vision sensor and the machine tool are used to unify the measurement results in the machine tool coordinate system, Through the optimized point cloud boundary contour feature extraction method, the rapid and accurate extraction of the boundary features of the measured board is realized, and the straight line is fitted from the boundary contour points and the size is calculated. Experiments show that the measurement error of this method is less than 0.1mm and the repeatability accuracy is higher than 0.2 mm, which meets the design accuracy requirements.

In order to suppress the time-delay signature (TDS) of the chaotic signals, a novel filtered optical feedback structure based on a semiconductor ring laser (SRL) is proposed. The fourth-order Runge-Kutta algorithm is used for simulating and the TDS of the chaotic signal output from a SRL is quantified by autocorrelation function and delay mutual information. The results show that, compared with the conventional optical feedback structure, the filtered optical feedback can effectively eliminate the TDS caused by the external cavity feedback delay time. Moreover, through calculating the distribution of autocorrelation and mutual information peaks in the parameter space of filter frequency detuning and filter bandwidth, it is found that TDS has been best concealed in the positive frequency detuning region.

The laser induced breakdown spectrometer (LIBS) is used to quantitatively determine the rare earth elements in the soil samples, and the certified reference materials for the chemical composition of soils is used as a study objects. The laser output energy , gate delay time, spot diameter, laser repetition rate, flow of protective gas (He) and other instrument operating conditions effect on the measurement results, the affection of working parameters on the measurement results is evaluated by the normalization method (measured value compared with the certified value), which is found that the laser output energy and gate delay time have great influence on the measurement results, and the best working conditions of the instrument are selected: 1.6 mJ of the laser output energy, 0.1 μs of the gate delay time, 70 μm of the spot diameter, 20 Hz of the laser repetition rate, 0.3 L/min of the protective gas. Based on this working parameter, 10 certified reference materials for the chemical composition of soils are selected, and multivariate calibration curves are used. The R values were all greater than 0.99, the calibration curve has a good linear relationship, therefore this method can accurately determine the rare earth elements in soil samples.

The mold shaking table is the heart of continuous casting equipment, and its performance evaluation is the key to study the mold shaking table. In order to evaluate the dynamic performance of the crystallizer shaker, firstly, develops a dynamic real-time test system based on laser displacement to measure the overall movement process of the crystallizer shaker; secondly, the original displacement data is measured; afterwards, the displacement data is processed by data processing software to evaluate the vibration dynamic characteristics of the crystallizer shaker; finally, after the test method is implemented in the field and the test data are processed, the performance difference of the mold shaking table in the field under different casting speeds can be well evaluated, which provides guidance for the overhaul and maintenance of the mold in the field.

In order to realize the quantitative detection of surface V-shaped cracks, this paper uses finite element method to study the mechanism of laser-excited ultrasonic surface waves and surface V-shaped cracks. The characteristics related to the length and angle of surface cracks are extracted from the reflected characteristic signal. The influence of the angle and length of the crack on the surface wave signal is analyzed, and the time-frequency analysis of the time-domain signal is carried out, and then a method to quantitatively characterize the length of the surface V-shaped crack using reflected surface wave is proposed. The numerical results show that with the increase of the crack length, the time difference of the reflected echoes also linearly increases, and the transmitted surface wave is more sensitive to the change of the crack angle. Through the relationship between the time difference of the reflected echo arrival and the crack length, the crack length can be quickly judged, and the length of the corresponding crack can be quantitatively characterized. The numerical results are in good agreement with the theoretical results, which provides an efficient and accurate method for the quantitative detection of the length of surface V-shaped cracks.

Tunnel junction (TJ) is one of the key technologies of high voltage vertical multiple photovoltaic cells (HVVMPC). In this paper, the performance comparison of HVVMPC based on Si doped and Te doped AlGaAs / GaAs TJ is introduced. The output performance of the two devices under different optical power and temperature is compared. The power coefficient and temperature coefficient of the two devices are obtained. The results show that Te doped HVVMPC has high efficiency. On this basis, the effects of series resistance, doping concentration and sub cell thickness on the external quantum efficiency (EQE) of HVVMPC under different bias voltage and the relationship between current mismatch characteristics and temperature are also discussed. Based on the correlation analysis and discussion, more ideas are provided for the optimization of HVVMPC with more sub units.

Decontamination and dismantlement are key steps in decommissioning nuclear facilities. Advanced technologies and equipment are required to achieve the goals of safety, efficiency and minimization of decommissioning waste. This paper introduces the application research of a series of laser technologies including decontamination, laser stripping and laser cutting in the decommissioning of nuclear facilities, analyzes the characteristics and application scope of each technology, and discusses the future of laser technology in decommissioning of nuclear facilities. The development trends and issues worthy of in-depth discussion are prospected.

Aiming at the problems of existing calibration methods, such as high cost, complicated steps, little robustness and low precision, a stereo vision inspection system is established, and a secondary calibration method based on high-precision special-shaped gauge block is proposed. The error of the system is compensated based on GA-BP algorithm. Firstly, the transformation between the Pixel coordinate system and the world coordinate system composed of a single CCD and a laser is solved by the quadratic calibration algorithm. Then, the method of laser fringe extraction based on Heisenberg matrix is used to extract the center line of the edge line on the light plane where the light plane of the laser projector intersects the high-precision special-shaped calibration block. Finally, GA-BP neural network algorithm is used to compensate the errors of the data collected by the stereo vision inspection system. The experimental results show that the precision of the special-shaped block is less than 0.05 mm after the width and depth compensation, and the stereo vision detection system is stable, reliable, high precision and strong anti-interference ability.

The fiber mode coupler has become an important choice for the generation of all-fiberultra-short pulsed vortex beams due to its wide working bandwidth and high efficiency mode coupling. In this paper, we first studied the vector mode characteristics of single-mode fiber, few-mode fiber and hollow-core fiber, and designed the single-mode-few-mode fiber (SMF-FMF) mode couplers and single-mode-hollow-core fiber (SMF-HCF) mode coupler for Ytterbium-doped fiber lasers. Then, the numerical simulation software is utilized to study the coupling characteristics of the mode coupler, and analyze the relationship between the core distance and the coupling efficiency. The simulation results show that the SMF-FMF coupler can convert LP01 mode to LP11 or LP21 mode, with a coupling efficiency of over 96%. In addition, the SMF-HCF coupler can convert HE11 into HE21 or HE31 mode with a coupling efficiency of over 82%. The SMF-FMF mode coupler and SMF-HCF mode coupler lay the foundation for obtaining large topologically charged ultra-short pulsed vortex beams based on ytterbium-doped mode-locked fiber lasers.

At present, the common 3D vehicle model reconstruction algorithm is real-time scanning and sampling through mechanical rotating lidar, and the number of points obtained is limited. Due to the unique scanning characteristics of hybrid solid-state lidar, the real-time scanning and sampling vehicle point cloud will have problems such as point trace clutter and vehicle model deformation. In this paper, a dynamic vehicle 3D model reconstruction algorithm for hybrid solid-state lidar is proposed. Based on the conventional 3D vehicle model reconstruction algorithm, the target vehicle is tracked, the vehicle is compensated, all the laser points of the vehicle passing through the detection area are traced back to the 3D contour of the vehicle, and the vehicle model is reconstructed using 3dshader software. At the same time, in order to verify the reliability of the algorithm, the test vehicle is tested for many times at different speeds. The results show that the relative error of the indication is less than 1% and the repeatability is less than 3%, indicating that the algorithm has high measurement accuracy and good stability.

Idiopathic retinal vasculitis aneurvsms and neuroretinitis (IRVAN) is a rare syndrome. The treatment is difficult and the natural prognosis is poor. We herein report a case of 55 years old and female patient. Her chief complaints were the vision loss of both eyes for more than 2 years and the visual distortion of right eye for about 50 days. A large number of retinal hard exudates could been seen in both retinas, and retinal vasculitis aneurvsms could been determined in the superior temporal of right eye and upon the optic disk of left eye. And epiretinal membrane could been seen around the macular area of the right eye. The main diagnosis of the patient is idiopathic retinal vasculitis aneurvsms and neuroretinitis (IRVAN) syndrome. Local laser photocoagulation therapy was been taken for the perfusion-free area. After the laser treatment, the patient's visual acuity was improved, macular edema and retinal hard exudate were reduced. After nearly 2 years of follow-up, the patient's condition was stable. Local laser photocoagulation therapy is an effective means for the patients with IRVAN syndrome.

Low level laser therapy (LLLT) has been widely used in the oral field. Its operation is relatively simple and non-invasive. Studies have shown that LLLT has the ability of anti-inflammatory, relieving pain, accelerating tissue healing and biological regulation. Some studies have suggested that the cellular molecular mechanism of LLLT is mainly related to the number and activity of mitochondria. It can regulate cell metabolism by increasing ATP production. Many scholars believe that LLLT can accelerate orthodontic tooth movement and alveolar bone remodeling, including the increase of the number of osteoclasts and osteoblasts and the deposition of collagen, accelerate the speed of tooth movement and shorten the orthodontic treatment course. It is of great clinical and scientific significance to study the application of LLLT in orthodontic tooth movement. Combined with references, the mechanism of LLLT and its application in orthodontic tooth movement were reviewed.