In order to investigate the shape and size information of the molten pool in the laser cladding process, the CMOS camera integrated with the laser head is used to shoot the molten pool. With the help of the image acquisition and image processing functions of the LabVIEW vision module, a set of real-time processing system for the laser cladding molten pool image is developed. Through the system, the molten pool features of laser cladding process is monitored and extracted quickly and effectively, and the effects of three main process parameters on the length, width and area of the molten pool are obtained. The single track laser cladding experiment of 316L stainless steel powder was carried out by using semiconductor lasers. The results show thatthe area and width of the molten pool increase, and the fluctuation of the molten pool length relative to the average value of its single track increases when the scanning speed decreases from 6 mm/s to 2 mm/s, and the laser power increases from 700 W to 1300 W. The length and area of the molten pool increase as the amount of powder feeding increases in the range of 4.2 g/min to 14.8 g/min, and the change in molten pool width is not obvious. The detection results of molten pool can be used as the output of closed loop control of laser cladding, and the stability of the molten pool is maintained by controlling the input parameters, therefore, the good effect of the cladding is obtained, which lays the foundation for the study of the closed loop control of laser cladding.

Multi-beam selective laser melting (SLM) has been adopted to enhance the production rate and to enable the production of parts with dimensions exceed the layout of traditional single-beam SLM apparatus. Several overlapping methods can be applied to connect different scanning zones to form a large scanning layout, in the meantime the forming qualities of the components are affected by the overlap methods due to different melting/solidification behaviors in the overlap zones. In this paper, two kinds of overlap methods were designed: direct overlap and interleave overlap, to study the effect of overlap methods on the forming qualities, both the forming precision of top surface and metallurgical defects in overlap zones were analyzed. The results show that the join interfaces in the interleave overlap samples are alternative with each other in different layers, thus the ill bonding defects can be suppressed and the remelting effect from the repeating laser scanning can be effectively controlled; interleave overlap method is better for the forming of dense components with high precision when compared with direct overlap method.

Aiming at the need of edge damage repair of thin wall parts of TC17 titanium alloy, the laser deposition repair test of TC17 titanium alloy damage specimen was carried out by using TA15 titanium alloy powder. By optimizing the process parameters, the less penetration and no defect repairing specimen was obtained. The microstructure, tensile properties and hardness distribution of laser deposited specimens were studied. The results show that the microstructures of the repair zone of TA15 are coarse columnar β crystals, α / β basket structure in grains, α lamellar orientation is random, compared with the TC17 substrate, the α lamellar structure in the heat-affected zone appears to be refined,the aspect ratio is improved. The tensile strength of the repaired specimens at room temperature reached 90.2% of that of the TC17 forgings, which was 10.6% higher than that of the TA15 forgings, the elongation after break is 4.3%, slightly lower than that of TC17 and TA15 forgings. The microhardness of the heat-affected zone was slightly higher than that of the substrate and the repair zone of TA15, which was lower than that of the TC17 substrate and higher than that of the TA15 forging hardness.

NiCr/Cr3C2 coatings were prepared on H13 steel by laser cladding. The microstructure and hardness of the coating were characterized by scanning electron microscope and microhardness tester. Then the wear resistance properties of the coating and H13 steel were tested by dry sliding friction and wear tester at room temperature. The wear resistances of the coating were investigated according to the wear morphology, the wear weight loss and the friction coefficient curve. The results show that the coating consists of dendrite, columnar crystals and cellular columnar crystals. In addition, the microhardness of the coating is higher than that of the matrix because the average microhardness of the coating is 2.5 times of the matrix. In the same wear condition, the wear resistance of the coating is obviously better than that of the matrix. The average friction coefficients of the coating and substrate are 0.488 3 and 0.678 7. And the average wear amount of the substrate is 3.6 times of the coating. Besides, the wear mechanism of the H13 steel matrix is mixed adhesion and abrasive wear while the coating is abrasive and fatigue wear. The results show that laser cladding NiCr/Cr3C2 alloy on H13 steel can significantly improve its wear resistance.

ZL114A casting aluminum alloy was repaired by laser deposition repair (LDR) using a fiber laser. Morphology analysis showed that the repaired region and the substrate form a good metallurgical combination. Under the control of temperature gradients and solidification rate, the microstructure of laser deposition layer transformed from columnar dendrites at the bottom of laser deposition layer into isometric crystal at the top of the last deposition layer. Tensile tests showed that laser deposition sample exhibited a superior tensile property, the tensile strength of the repaired region reaches 87.5% of Al alloy casting standard, and the elongation is much higher than that of Al alloy casting standard. Fracture analysis showed that the fracture mechanism of ZL114A casting aluminum alloy is brittle fracture, but the fracture mechanism of the repair zone is toughness fracture. Residual stress analysis showed that there exists the stress concentration issue, and the peak of residual stress locates in the joint between the substrate and the repaired region. After stress relief annealing, the residual stress of laser deposition samples decline by 10-23 percent.

Preparation of Al2CoCrCuFeNi high-entropy alloy coating with thickness of 150μm on the surface of H11 steel by laser cladding technology was studied. The optimized multi-pass lap process parameters were obtained: the current was 270A; the scanning speed was 3mm·s-1; the defocus was fixed at-14mm; 40% track overlapping condition was used. The microstructure, microhardness and wear resistance of the coating were investigated. The results show that Simple solid solution phases were formed in the coating layer with a typical microstructure at the top of the cladding zone consists of equiaxed grains while that at the bottom consists of columnar grains, And metallurgical bonding is formed between the substrate/coating. The average microhardness of the coating layer shows 70% enhancement compared with that (HV 250) of the H11 substrate; The wear rate of the coated sample is 30% that of the H11 substrate. The coating layer exhibits great enhancement in microhardness and wear resistance compared with the H11 substrate.

The (B2O3+WO3+C) Ni-based cladding layer has been prepared successfully by laser cladding on steel 45# substrate. The microstructure of the cladding layer was analyzed by scanning electron microscope, and the microhardness of the cladding layer was measured by microhardness meter. The result shows that laser power and(B2O3+WO3+C)powder content have a significant effect on the microhardness of the cladding layer. At a laser power of 1.8 kW, (B2O3+WO3+C) powder content of 15%, scanning speed of 2 mm/s and defocusing of 50 mm, the average microhardness of the cladding layer is as high as HV0.31300, which is about 6.5 times the average microhardness of the substrate, which greatly improves the hardness and wear resistance of the cladding layer.

In order to study the optimal process parameters of laser welding of Q235/316 dissimilar thin steel plate, the laser tailor welding test was carried out by Nd: YAG pulsed laser. Five factors and four levels of orthogonal experiments were designed to study the effects of various process parameters on elongation and tensile strength after fracture. The welding parameters were optimized by range analysis method, and the comprehensive optimal parameter combination was found by multi-objective fuzzy comprehensive evaluation method. The results show that the factors affecting the elongation and tensile strength of the process parameters are defocus amount>pulse width>frequency>scanning speed>current, and the defocusing amount D is the most important influencing factor of welding quality; The optimal combination of the rate is A4B4C4D4E1, and the optimal combination of tensile strength is A1B4C3D4E2. After the fuzzy comprehensive evaluation, the integrated optimal process parameters are current P of 150 A, pulse width T of 2.4 ms, frequency f of 22 Hz, defocusing. The quantity h is -17 mm and the scanning speed v is 250 mm/min; after optimization, the welding quality of the sample is stable and the mechanical properties are good.

In this paper, the laser welding process of 1 mm-thickness 316L stainless steel sheet was studied, and the effect of laser welding parameters on the penetration was analyzed by orthogonal experiment. The results show that with the increase of laser power, the penetration increases correspondingly; with the increase of welding speed, the penetration decreases correspondingly, and the penetration is almost inversely proportional to the welding speed. When the welding speed is greater than 0.03 m/s, the penetration decreases significantly; when the forward defocusing is adopted, the penetration decreases with the increase of defocusing. When the defocusing is greater than 8 mm, the penetration decreases obviously; when Ar, He and N2 are used as protective gases, the penetration is arranged in the order of He>N2>Ar; metallographic analysis results show that when the power is greater than 1 600 W, the penetration of welds reaches more than 1 mm. The best welding parameters are as follows: power is 1 800 W, welding speed is 0.026 m/s, defocusing is 7 mm, shielding gas argon and gas flow is 10 L/min.

In this paper, a diode laser was used to conduct laser transmission welding experiments on polycarbonate with aluminum film as the absorption layer. The welding process parameters were optimized by the combination of single factor experiment method and response surface method with different aluminum film width as the main influencing factor, combined with laser power and welding speed. The fitting equation and the optimal welding process parameters were obtained. The relationship between the width of the aluminum film and the width of the weld was analyzed. The finite element model based on the middle layer of aluminum film was established by COMSOL software. The temperature field distribution under the welding process parameters was studied. The results show that the simulated weld width is consistent with the experimental weld width.

Aiming at the fiber laser welding of 1.2 mm thick TC4 titanium alloy sheet, the effects of different welding parameters on the mechanical properties of the weld were studied by orthogonal test. The optimum process parameters of TC4 laser welding were obtained. The differences in microstructure and properties of weld samples and base metal samples under optimal welding parameters were compared by optical microscopy, microhardness, tensile test and bending test. The results show that the laser power has a great influence on the tensile strength, while the defocusing and the welding speed have the same level of influence. When the welding specification is reasonable, the tensile strength of the joint reaches more than 93% of the base metal, and the elongation is more than 83% of the base metal. The fracture site mainly appears in the base metal area, the fracture is ductile fracture, and the dimple morphology is visible.

In this study, the adjustments and changes of subwavelength ripples induced by ultrafast laser on titanium are experimentally investigated. In our experiments, 1064 nm picosecond laser and 800 nm femtosecond laser are used to irradiate the surface of metal titanium. The effects of incubation on the formation of subwavelength ripples are studied by changing pulse number and irradiation modes. The experimental results show that: 1) the overall trend of ripples areas, ablated areas and periods of rippled structures increases as the number of pulses increases; 2) due to the incubation effects, the increase is different; 3) by designing laser pulse irradiation modes, samples firstly irradiated by several shots and then by remaining shots, have better surface morphologies. Hence, large-area, uniform rippled structures can be adjusted by designing laser pulse modes and pulse number.

Picosecond laser precision processing of diamond and other hard brittle materials are currently the hot spot in the technology frontier and the best engineering solution. The cutting surface edge breakage <5 μm and the roughness of the cutting surface roughness Ra1.6 can be achieved by conventional laser light source with pulse width ≤20 ps.Now the low-cost picosecond fiber laser with a pulse width of 200 ps was used. Laser power, cutting speed and other process parameters were optimized. Beam shaping was done through an external optical path shaping system. And focus lens optimization design and other key technologies for research and development. The maximum edge breakage width ≤6μm and the processing quality of the surface roughness Ra1.6 were achieved . The processing efficiency was consistent with 20 ps laser precision processing technology. The production cost was significantly reduced. The need of precision cutting of diamond tools was met. And the follow-up polishing problem of drawing die and cutting edge machining can be solved.

In order to explore the TC4 titanium alloy aircraft skin materials of laser cutting technology, the laser cutting process is analyzed theoretically and a mathematical model is established in this paper. The initial perforation and cutting process of laser cutting are simulated by ANSYS finite element software, the reasonable piercing time of titanium alloy specimens with a certain thickness, the propagation rule of temperature in the plate during cutting and the distribution of temperature field at different cutting speeds are obtained. The results show that When the laser starts to perforate, the perforation time of 1000W power is the shortest, which is 0.12s; the perforation aperture is larger and not affected by the power change; the power and spot diameter are constant, the slower cutting speed is easier to penetrate the titanium alloy plate, but the slit increases with the cutting speed decreasing. Through piercing and cutting experiments on titanium alloy plate, the morphology of the initial hole and the cutting edge was observed on the CCD image measuring instrument. It was found that the initial aperture was 1.35 times the width of the cutting edge; the cutting seam is inverted cone from top to bottom, and the upper part has high precision and the lower part has large slag hanging. This further explains the law of temperature propagation in the cutting process. These conclusions provide a reference and basis for the application of laser cutting technology to the cutting of aircraft skin materials.

First of all, using a carbon dioxide laser with a wavelength of 10.6 μm, the surface of TC4 alloy was polished. The surface roughness of the material was measured with a three-dimensional profile instrument. The influences of factors on the surface roughness such as laser power, defocus amount, scanning speed, and scanning pitch were analyzed in combination with the micro-morphology of the material surface before and after polishing. Obtaining the ideal process parameters, the minimum surface roughness of the TC4 alloy was 117.62 nm. However, thecarbon dioxide laser polishing caused serious heat accumulation and obvious surface cracks. Then, using a fiber laser with a wavelength of 1080 nm polished the TC4 alloy.Similarly, The effects on the surface roughness such as surface morphology, defocus amount, and scanning path were analyzed. Innovatively using multiple moving scanning polishing, theoptimal polishing effect was achieved. The minimum surface roughness of the TC4 alloy was148.91 nm. The experimental results show that the using of the fiber lasers for multiple shifting scans can more quickly and effectively polish the TC4 titanium alloy. And due to the low laser energy density, there is no obvious deformation and cracks on the surface of the TC4 alloy.

In this paper, the morphology of micro-holes on PMMA thin plate manufactured by excimer laser is studied. The influence of laser pulse number on the micro-hole depth is firstly analyzed, and the influence of laser pulse number, laser single pulse energy and laser pulse frequency on the micro-hole taper is further explored. Drilling efficient was observed by optical microscope and SEM. It was showed that in a certain range, the pore depth increases linearly with the number of laser pulses, while the micro-hole taper decreases linearly with the number of laser pulses, and the micro-hole taper decreases linearly with the laser single pulse energy, All the effects are significant. Meanwhile, the laser pulse frequency has no effect on the micro-hole taper. By selecting proper number of laser pulses and low single pulse energy properly, a conical micro- hole with good quality can be obtained with a large depth and a certain taper.

The processing effect of excimer laser Direct Writing in the case of surface machining will show the phenomenon of uneven processing and inconsistent processing line width. etc. The main work of this study is to realize the monitoring and compensation of the machining position in the surface micromachining process of excimer laser. The reference distance is selected before the operation of the device, and the machining position of each moment is tracked during the operation of the device. When the machining point is located at the lower deviation point or upper deviation point of the surface bias, the electric pan is reverse compensated to pull the point back to the baseline. In this way, the equal processing distance of each moment is ensured, which means that the machining platform in real time with the same fluctuation changes on the surface of the workpiece, so that the size of the workpiece on the surface remains unchanged. In order to achieve this goal, the hardware scheme of compensation device is constructed, and the sensor parameter matching and follow-up tracking software are developed. A set of excimer laser surface micromachining compensation device which can be applied to the processing of metal and non-metallic materials is developed, of which the move speed is more than 100μm/s and the compensation error is less than 20μm. Furthermore, the compensation performance and compensation processing effect of the device are verified by experiments.The maximum deviation were greater than 20μm in 18 of 100 compensation performance tests, and 2 of those were over 30μm. The device is composed of six-axis electric translation table, motion control card, laser sensor head, Laser sensing controller and PC computer. Secondly, based on the MFC framework, the follow-up software of excimer laser surface machining is written by C + + language, and the control signal sent by the software can flexibly control the response of electric translation table.

The edges of machined parts usually produce burrs, which affect the use of parts. In order to remove burrs from parts, a 800 W fiber laser with a wavelength of 1 064 nm and a pulse width of 200 ns was used to deburr the edges of six series of aluminium alloys. Laser cutting is to melt and evaporate the irradiated surface by the energy released when the laser beam irradiates the workpiece, so as to cut the workpiece. This characteristic can be used to cut the big burr of the workpiece. Secondly, the energy density can be reduced by changing the size of laser spot, so that the irradiation surface can only melt without evaporation, and the melting fillet can be realized. Based on the above two points, the deburring effect of aluminium alloy parts was experimentally studied. The influence of laser power, scanning speed, scanning times and defocusing amount on deburring quality and the weight of each parameter are studied. The optimum parameters are obtained as follows: laser power 560 W, scanning speed 50 mm/s, focal position 3mm and laser power 640 W, scanning speed 60 mm/s and focal position 3 mm. It can remove parts burrs and melt round corners.

The adhesion coefficient between the wheel and rail has a significance influence on the safety and stability of the train operation. In winter a thin film of ice presemed onrail will greatly reduce the wheel-rail adhesion coefficient. In this paper the contact region of wheel/rail will be divided into two regions, that is the solid contact region of ice-steel and the mixed lubrication contact region of water-steel according to the phase diagram of ice and the principle of pressure melt. The adhesion coefficient of high-speed wheel/rail is investigated with the variation of speed from 100 km/h to 500 km/h under the temperature region from -21 ℃ to 0 ℃ based on the unified Reynolds equation. Regular patterns on wheel surface, such as longitudinal, transverse and rhombus, formed by laser texturing, will improve the adhesion coefficient of wheel/rail under ice-water mixed lubrication. The investigation is helpful for adhesion controlling technology of high-speed railway.

In this paper, 18Ni300 samples were prepared by laser melting (SLM) technology. The heat treatment was studied by different heat treatment processes and cooling methods. The mechanical properties of the materials after different heat treatment were obtained by tensile test, Rockwell hardness and metallographic examination. Among them, 550 samples were annealed by stress-free annealing. After heat treatment at 820 + ageing 490, the metallographic structure is fine plate martensite with hardness up to 54HRC and tensile strength up to 1800 MPa. It has good comprehensive mechanical properties. This paper can provide reference for heat treatment of SLM printed metal parts.

In this paper, based on laser-ultrasonic conversion technology, the internal defect detection method of SF6 gas-insulated enclosed combined electrical appliances (GIS) is studied. Through the analysis of the operation of GIS equipment in Shenyang Electric Power Bureau, the characteristics of partial discharge, the comparison of the causes of partial discharge and the analysis of the characteristics of laser-ultrasonic conversion technology, the sensor layout, detection process, diagnostic basis and characteristics of partial discharge detection of internal defects in GIS equipment are discussed. The principle is analyzed, and the diagnosis process of partial discharge in GIS based on ultrasonic conversion technology is analyzed. The results show that the maximum position of the signal is 1/4 of the height below the upper flange of the circuit breaker. Based on one circle of the circuit breaker tank, the stable partial discharge signal can be diagnosed. The signal has a small amplitude of 5.5 mV. Based on this position, the amplitude attenuation trend of the downward signal and the upward signal is obvious. In one circle of the tank, the stable partial discharge signal can be diagnosed, so it can be inferred that the discharge source is not in the shell but in the central conductor. Finally, some suggestions for partial discharge detection and diagnosis in GIS are put forward to provide reference for equipment maintenance strategy.

The detection of surface target objects is a prerequisite for unmanned ship to identify surface objects or avoid obstacles. Based on the absorption characteristics of laser signal by water body, a method of detecting surface target by 3 d laser scanning is designed in this paper. The method obtains the point cloud of the surface float by 3D laser scanning, then defines the effective point cloud set by conditional filtering, and divides the water surface target object by the Kd-tree based nearest neighbor clustering method, finally uses the axial bounding box(Axis Aligned Bounding Box, AABB)calculates the position of the target relative to the lidar. Three sets of surface object detection experiments are designed in this paper. The data shows that the method can detect the floating objects on the water surface and can complete the position measurement.

In this paper, a comprehensive analysis and research is carried out on the actual railway traffic engineering area in Liaoning Province. Laser displacement sensor is used to design the deformation detection system of subway tunnel structure, which can give full play to the function of three-dimensional laser scanning technology. Finally, the following conclusions are drawn. In the tunnel deformation monitoring project, three-dimensional laser scanning point cloud data is used to extract tunnel section. The collection period is 10 periods and the time span is 55 days. The characteristic section of a metro tunnel in Liaoning Province is analyzed and monitored. From the third to the sixth period, it is found that the load and settlement of the tunnel will change greatly with the continuous construction of super high-rise buildings, of which the latter is gradually in a stable state. Combining with the actual engineering data, the settlement value of the observation period is the largest at 3.35 mm. Analyzing the results of the three-dimensional laser scanner and the traditional level settlement detection, it is found that the variation trend and variation of tunnel settlement can be approximately the same. This shows that the method proposed in this paper can analyze tunnel cross-section deformation more comprehensively and intuitively.

High-order Bessel beams are widely used in laser processing and precision measurement. For the realization of high-order Bessel beams, a spatial light modulator is used to load the high-order phase hologram instead of the real spiral phase plate and the axicon. The distribution of light field in two modes of axicon combination and phase superposition is analyzed theoretically, and the beam modulation in two modes is designed and compared experimentally. The results show that the modulation effect of the phase superposition method is better than that of the axicon combination method. Meanwhile, the operation is flexible and the processing error can be reduced. It is an effective method for generating high-order Bessel beams.

In this paper, the characteristics of focused ultrasound are studied based on laser focused ultrasound enhancement technology. The results show that the focused ultrasound characteristics are measured by the laser focused ultrasound enhancement system. The results show that the acoustic power increases gradually with the increase of the excitation voltage. When the excitation voltage increases by 85 V, the acoustic power reaches 169 W. By verifying the stability and consistency of the working state of the excitation power supply and the ultrasonic transducer system, it lays a foundation for further study of the ultrasonic characteristics. The finite element analysis is carried out with ANSYS10.0 software, and the theoretical relationship between thermal effect and ultrasonic duration is obtained. The simulation results show that the temperature value is stable when the step number is 45-105. The maximum temperature of the system increases by 0.001 5 ℃ when the duration of ultrasound is 5 μs and 0.054 ℃ when the duration of ultrasound increases to 105 μs. This shows that there will be a minimal thermal effect in the test experiment, and the impact on the test is very small.

In view of the demand for high precision automatic extraction of power lines in the application of airborne laser radar technology, an improved algorithm for automatic extraction of power lines in complex terrain background is proposed. First, the ground and non-ground points are separated by the point cloud filtering algorithm for normalization, and the candidate point cloud is obtained based on the elevation characteristics of the power line point cloud and its continuous distribution in Z direction. Secondly, the Hough transform is improved by the peak enhancement local operator, and the precision extraction of the power line point cloud is realized. Finally, a single powerline can be obtained by the nearest growth algorithm based on the spatial continuity of the power line point cloud. The experimental results show that the extraction rate reaches more than 95% by using this algorithm. The algorithm can accurately extract power line points from the influence of terrain undulating and complex terrain, and can identify single line of power lines accurately.

A compact portable laser-induced fluorescence detector, which includes an excitation source of 405nm stable spectra diode laser, a fluorescence collection module based on a fluorescence optical fiber probe and fibre, a fluorescence analysis module of a grating spectrometer. The study on the photodynamic diagnosis of squamous cell skin carcinoma of SKH-1 hairless mouse using the 405nm laser-induced fluorescence spectra of PpIX induced by ALA was done.

Objective: to investigate the clinical efficacy of pulsed holmium laser(Nd:YAG laser)in the treatment of acute pericardial periodontitis, and to observe the effect of Nd:YAG laser on microbial changes in the periorbital pocket.Methods:126 patients with acute pericoronitis were randomly divided into control group (conventional treatment group) and experimental group (conventional treatment+laser-assisted treatment group).Only partial crown irrigation was performed in the control group.The blind bags were continuously washed with 3.0% hydrogen peroxide and 0.9% normal saline for 3 days(once per day).The experimental group was dealed with Nd:YAG laser for 3 days (once per day)and taken the exudate of the blind pocket on the 1st day before and after laser treatment.The pain degree,mouth opening and gingival index (GI value)of the two groups were evaluated before treatment and after the 1, 2, 3, 5and 7th day of treatment. The changes of dominant bacteria before and after laser-assisted treatment were observed on the 1st day. We compared the effectiveness of the two groups after 7th day of treatment.Results:After 1, 2and 3 days of treatment, the pain index, degree of mouth opening improvement and gingival index were better in the experimental group than in the control group.The difference was statistically significant(P0.05).The number of microbes in the peri-cryophytes of the experimental group was significantly decreased before and after treatment on the 1st day (P0.05).Conclusion:Through clinical observation and microbiological analysis the application of Nd:YAG laser in the treatment of acute wisdom tooth pericoronitis can effectively reduce the pathogenic bacteria in the periorbital pocket, reduce pain and inflammation.Meanwhile we can improve the degree of opening, shorten the course of disease.Nd:YAG laser in the treatment of acute wisdom tooth pericoronitis is simple and safe.To a certain extent,the use of antibiotics is reduced and it is suitable for a wide range of people,and it is worthy of being widely used in clinical practice.

Objective: to discuss the effect of CO2 fractional laser assisted with ultrasonic basic fibroblast growth factor(bFGF) delivery on acne scars and its influence on adverse reactions. Methods: 79 cases of patients with acne scars in our hospital from January 2016 to February 2019 were analyzed retrospectively, according to the different treatment methods, the patients were divided into the control group (n=43, CO2 fractional laser treatment) and the study group (n=36, CO2 fractional laser treatment + ultrasonic bFGF delivery treatment). The clinical efficacy of the two groups was compared, and the wound healing time, erythema duration, time of missed work, incidence of adverse reactions, comfort and appearance satisfaction of the patients in the two groups were recorded. The scar ECCA score, erythema index, melanin index, transepidermal water loss (TEWL) and cuticle moisture content before and after treatment in the two groups were observed.Results: ①The total effective rate in the study group was 91.67% (33/36), higher than that in the control group (79.07%(34/43), but the difference was not statistically significant (P>0.05).②The wound healing time, duration of erythema and time of missed work in the study group were shorter than those in the control group, and the incidence of adverse reactions was lower than that in the control group, with statistically significant differences (P0.05) before treatment between the two groups, ECCA score, erythema index, the index of melanin TEWL significantly decreased (P<0.05) and cuticle moisture content significantly increased (P<0.05) after treatment in the two groups, but the improvement of ECCA score, melanin index, TEWL and cuticle moisture content in the study group was greater than that of the control group (P<0.05).Conclusion :Ultrasonic bFGF delivery can improve the efficacy of CO2 fractional laser in the treatment of acne scars and reduce adverse reactions.