Optical manufacturing and craftwork
2019, 48(7): 742001.
doi: 10.3788/IRLA201948.0742001
Single Point Diamond Turing(SPDT) technology has been widely used in the infrared optical surface manufacturing field. However, the micro-nano texture of turned surface is influenced by the turning parameters, the infrared material properties, tip's parameters of the diamond tools and so on. Based on the detailed analyses of the factors which will affect the turned surface quality during the infrared optical surface SPDT process, a new type of cutting movement that called Evenly tool marks Space and Constant linear Velocity(ESCV) cutting method was proposed for obtaining high surface quality in the paper. The principle of the ESCV method was introduced in detail, the process of cutting parameters determination of the ESCV was given out, and the curve of spindle speed and federate of the ESCV was simulated based on the cutting parameters. A CVD ZnS workpiece was turned via ESCV method, it's best cutting linear velocity was 3.14 m/s, the Ra value of whole surface roughness was decreased from 6.4 nm to 4.1 nm before and after ESCV. The uniform quality turned surface is gained.
2019, 48(7): 742002.
doi: 10.3788/IRLA201948.0742002
Chalcogenide glass lens is one of the important components for novel temperature-adaptation IR optical systems. With the development of thermal imaging civil market, the demand for industrialization technology of chalcogenide glass lens is increasing rapidly. Precision molding of As2Se3 chalcogenide glass aspheric lens were studied systematically. A series of molding process parameters were investigated and optimized for As2Se3 chalcogenide lens with a diameter of 21 mm. Through the compensation correction of the mould, chalcogenide lens that met the design precision of PV 0.7 m were fabricated successfully. Effect of molding on the physical properties of As2Se3 chalcogenide glass was also investigated. The results show that after molding, the density, hardness, and glass transition temperature of As2Se3 glass decrease, whereas its maximum transmittance increases. With the help of Raman spectra, the microstructural origin of these abnormal phenomena was analyzed and discussed. This work would provide data and reference for future fabrication of large-aperture aspheric chalcogenide lens.
2019, 48(7): 742003.
doi: 10.3788/IRLA201948.0742003
Non-hydrogen silicon carbide (SiC) films were deposited on germanium substrate by pulsed laser deposition. The effects of laser energy on the microstructure, composition and infrared optical properties of SiC films were investigated. The infrared transmittance spectrums of SiC films were measured by Fourier transform infrared spectroscopy (FTIR). The spectroscopy analysis showed that the characteristic absorption peak of Si-C bonding was found at 785 cm-1, and the SiC films had good transmittance in the range of 4 000-1 300 cm-1. The optical constants of the SiC films were derived by fitting transmittance spectrum curves. It was found that the refractive index and the extinction coefficient of SiC films increased monotonicly with laser energies increasing in the range of 2.5-7.7 m. The refractive index changed from 2.15 to 2.33 as laser energies increased from 400 mJ to 600 mJ. The extinction coefficient was of the order of 10-3 when laser energies were of 400 mJ and 500 mJ. This study indicates that the SiC film is an excellent optical film material between 2.5 m to 7.7 m.
2019, 48(7): 742004.
doi: 10.3788/IRLA201948.0742004
The Fe0.5NiCoCrCuTi high entropy alloy coating was prepared by laser cladding on 40Cr steel surface. The microstructure, hardness, wear resistance and corrosion resistance of Fe0.5NiCoCrCuTi high entropy alloy were investigated by means of scanning electron microscopy and energy dispersive spectroscopy(SEM/EDS), micro/Vickers hardness tester, friction and wear tester and electrochemical workstation. Experimental results show that Fe0.5NiCoCrCuTi high entropy alloy is mainly composed of coating, heat affected zone and the substrate. The coating has no pores, cracks and other defects, metallurgical bonding with substrate; the coating is mainly composed of two kinds of lamellar microstructure morphology, the grains closely arranged, fine particles are distributed on the grain surface. There is element segregation in the coating, but to a relatively small extent. Under the combined action of fine-grained strengthening, solid solution strengthening and precipitation strengthening, the Fe0.5NiCoCrCuTi coating has high hardness, the maximum surface hardness is 857 HV, about 3.3 times as much as the 40Cr steel. High hardness and fine scale precipitates provided a guarantee for the wear resistance of the coating. The corrosion resistance of Fe0.5NiCoCrCuTi high entropy alloy coating in 3.5% NaCl and 0.5 mol/L in H2SO4 solutions are excellent, compared with 304 stainless steel, the corrosion current density were decreased by 2 and 3 orders of magnitude respectively, the corrosion potential were shift toward positive direction for 0.230 V and 0.161 V respectively.
2019, 48(7): 718001.
doi: 10.3788/IRLA201948.0718001
One laser oscillating mode would split into two with an optical wave plate being inserted in the resonator. The frequency difference of splitting modes can be measured to obtain the wave plate phase retardation. Based on the principle, a measuring instrument for wave plate was designed with optical path along vertical direction, which could choose certain measuring method according to oscillating modes altered by frequency difference. The half-cavity laser, the detection of laser intensity and frequency difference, the controlling program were described in detail. In order to automatically measure wave plate with high precision, the instrument utilized the equal intensity point of two orthogonally polarized lights as working point, and compensated the systematic errors from initial phase retardation and slightly tilted wave plate. In testing experiments, the instrument can automatically discriminate and measure arbitrary retardance wave plates. The measurements show standard deviation of about 0.01 and uncertainty of 0.03 (less than /10 000) as to a multi-order quartz wave plate. The instrument has traceability and only the frequency difference of laser modes is acquired in measurement.
The calibration of the spectral responsivity of Fourier transform infrared(FTIR) spectrometer is the basis for accurate spectrum measurement. The spectral responsivity of FTIR spectrometer measurement system with high temperature blackbody infrared radiation characteristics, established at National Institute of Metrology, China(NIM), was calibrated based on piecewise linear calibration via the ThermoGage HT9500 high temperature reference blackbody furnace from NIM. A calculation model of the spectral responsivity calibration of FTIR measurement system was established and described. The infrared spectrum of the blackbody radiation source was measured in the temperature range of 1 273-1 973 K in the wavelength range of 1-14 m. The results indicate that the method of piecewise linear calibration is practicable. The measured infrared spectrum in the temperature range of 1 373-1 873 K in the wavelength range of 1-14 m was compared with the calculation which showed the signal divergence was less than 1%. The calculated temperature obtained by inverse calculation in this temperature region was compared with the actual temperature which showed the temperature divergence was less than 0.45%.
2019, 48(7): 718003.
doi: 10.3788/IRLA201948.0718003
In order to adapt to the application requirements of different field of view spectrometers, a continuous zoom medium-wave infrared spectrum imaging system based on offner scheme was designed. The front zoom system to achieve continuous zoom in the range of 60-300 mm was introduced in the system, and a grating-type offner concentric structure was used for spectral splitting and imaging. The working band was 3-5 m, the cooled medium-wave infrared detector was used, the F#=4.0 in this system. According to the object image exchange principle and the power distribution principle, the initial structure of the front zoom system and the relay system were calculated, and the zemax software was used to optimize each subsystem to meet the design parameters. The modulation transfer function of the final continuous zoom medium-wave infrared spectrum imaging system based on offner scheme was close to the diffraction limit at a spatial frequency of 33 lp/mm, and the root mean square radius of the spot was smaller than one pixel. The design results show that the system structure is simple, and the image quality is good and meets the design indicator requirements at each focal length position and each spectral segment.
2019, 48(7): 718004.
doi: 10.3788/IRLA201948.0718004
In view of the functional requirements of high surface shape error accuracy, high reliability and high stability of mirror support for space remote sensor, a three-point back support structure applied in the mirror support in the field of space was designed, the back support structure included taper sleeve, flexible segment and adjusting pad. The in-depth study was done about support principle and engineering realization of the three-point back support structure. The error source which caused the variation of surface shape error of the three-point back supporting mirror component was summarized, the theory of surface shape variation caused by various error sources was studied, and the corresponding design of the supporting structure was carried out to alleviate the variation of the surface shape error of the mirror caused by various error sources. Firstly, the static and dynamic simulation of the design results were carried out by means of finite element analysis, then the assembled and processed mirror assembly was tested. The results show that the surface shape error of mirror with the three-points support structure is better than /60(=632.8 nm), the rigid body displacement of mirror is smaller than 0.01 mm, the dip angle is smaller than 2,the mass of the mirror component is smaller than 4.5 kg. The component has a reasonable distribution of modal, the fundamental frequency is 254 Hz, which is higher than the requirement of 120 Hz. The maximum magnification rate of the mirror assembly under sine vibration and random vibration is 1.73 times, and the maximum stress under sine vibration and random vibration is 369 MPa, far lower than the yield limit of the selected material.
2019, 48(7): 718005.
doi: 10.3788/IRLA201948.0718005
In order to improve the relative aperture of the star sensor and broaden the spectral range of the detection, the detector sensitivity calculation model was applied to determine the parameters of the optical lens in a star sensor, then an optical lens based on satellite platform was designed. The lens was composed of 7 spherical lenses, with the spectral region of 500-800 nm, the focal length of 50 mm, the relative aperture of 1/1.25, the field of view(FOV) of 8.458.45, and the total length was 83.33 mm. This lens used the telecentric structure in the image to reduce measurement errors caused by image defocus and other factors. After the optimization, the lens distortion was less than 0.5%, the center of mass color deviation was controlled within 2 m, and the diffraction encircled energy (within 33 pixel) was greater than 80%, the maximum magnification chromatic aberration was -0.073 m, the dispersion spot energy concentration of all the fields of view was almost the same. In different temperature environments, the small change in focal length of the system verified the athermalization. The optical lens had good image quality.
2019, 48(4): 442001.
doi: 10.3788/IRLA201948.0442001
In order to improve the edge quality of the continuous phase plate in magnetorheological polishing and realize the full aperture polishing of the components, the edge extrapolation of the original error profile must be carried out. In view of the shortcoming of the existing edge extrapolation algorithm, a two-dimensional Gerchberg bandlimited extrapolation algorithm was proposed to realize the edge extrapolation technique that was frequency domain matching for continuous phase plate. Firstly, Zoom Fourier transform was applied to the original error profile to get its high and low cutoff frequencies. Then, the modified two-dimensional Gerchberg extrapolation algorithm was used to fill data in extrapolation region around the original region to get the same spectral structure as the original region. At last, an magnetorheological polishing experiment was performed on a 100 mm100 mm continuous phase plate element with complex frequency spectrum structure. The experimental results show that the edge processed by the method is more regular and the edge effect radius is reduced from 5 mm to 2 mm, and the residual error RMS is reduced from 19.3 nm to 9.7 nm. It indicates that the modified Gerchberg edge extrapolation technique can obviously improve the edge quality and the overall convergence precision of continuous phase plate.
2019, 48(4): 442002.
doi: 10.3788/IRLA201948.0442002
With the coming of 2025 in China, it is an irresistible trend to use industrial robots to process agricultural machinery online. In order to grasp workpiece intelligently, industrial robots need to identify the type of workpiece and pose of workpiece. In view of the difficulty in identifying the types of work pieces on the pipeline, an online recognition method based on the 3D point cloud of laser scanning was proposed. This method can identify which workpiece is the moving piece. First, the disordered workpiece on the assembly line was scanned, the 3D laser point cloud data of the workpiece was obtained, and the 3D laser point cloud data was initially denoised. Using MATLAB software to slice the 3D laser point cloud, the main view slicing, top view slicing, left view slicing was obtained. By using the HALCON software, the boundary information of the center slice was extracted, enhanced, segmented, and the characteristic parameters of the extracted area were extracted. Then the type of the workpiece was identified. Experimental results show that the accuracy of recognition is 96.67%. This method can be used for reference to similar problems.
2019, 48(2): 242001.
doi: 10.3788/IRLA201948.0242001
Since the invention of lasers in the 1960s, the pulse duration has been continuously shorten down to the sub-picosecond and even femtosecond regime. It makes the laser processing technology in the ultrashort pulse laser era. Compared with other methods, the ultrashort pulse laser drilling of micro-hole is independent of the size and materials, and it has the advantages of high precision and automation. The advantages, such as the cold processing, breaking the diffraction limit, for ultrashort pulse laser drilling of micro-hole were presented. Three classical models were demonstrated, which were the threshold fluence-hole diameter model, the multi-pulse cumulative model and the single-pulse ablation depth model. The experimental studies for ultrashort pulse laser drilling of micro-hole were analyzed. Furthermore, the challenging issues and prospects were concluded.
2019, 48(2): 242002.
doi: 10.3788/IRLA201948.0242002
In order to reduce the substrate deformation and residual stress during laser direct manufacturing of TC4 components, the influence of different scanning orders on the deformation and residual stress of the parts formed by subarea scanning strategy were studied. The newly-defined outside-in and inside-out scanning orders, and a randomized scanning order were applied and compared. The deformation was measured by the surface structure light measurement system and the residual stress was measured by the X-ray diffraction method. The results show that different scanning orders have significant effects on the deformation and residual stress. The maximum substrate deformation is reduced by 60% by the outside-in scanning order compared with that by the randomized scanning order, while larger residual stress is introduced, which is even up to 392 MPa. Oppositely, the randomized scanning order makes a more uniform residual stress distribution and the maximum residual stress is only 93 MPa. Therefore, it is beneficial to balance the substrate deformation and residual stress of large TC4 forming parts by applying the outside-in and randomized scanning orders in the front and back forming period respectively.
2019, 48(2): 242003.
doi: 10.3788/IRLA201948.0242003
Circular groove bulkhead can be finished by laser circular scanning without mould. Therefore, research of the curved surface deformation rule and characteristics was of important significance for engineering applications. Firstly, the influence of the scanning number n, the circular scanning radius R, the plates' width W and the length from baseline to the free end L on the curved surface deformation were analyzed in detail. Secondly, combining with the effect of various parameters on the surface deformation and surface deformation test measurement data, obtained surface deformation experience function about the parameters. Then the surface deformation change rule and trend were analyzed. Finally, the strategy of laser circular scanning has obtained the circular groove bulkhead samples and its two side wall of the mean curvature radius are 84.51 mm and 86.77 mm respectively. This study lays a solid foundation of both the circular groove structure and the double circular grooved structure by laser circular scanning.
In order to realize high-precision mass production of small diameter dual aspherical chalcogenide glass lenses, cooling gap in cooling stage was studied to reveal its influence on lens molding quality through simulation and experiments. Firstly, high temperature viscoelastic mechanical, structural relaxation and interface heat transfer model of the chalcogenide glass molding was analyzed and applied to simulation study. Secondly, molding simulation of target lens was carried out, and influence of cooling gap conditions on internal temperature, stress distribution, and profile deviation of the lenses were discussed. Finally, the molding experiments corresponding to simulation were conducted. The influence of cooling gap conditions on the surface form accuracy PV, surface roughness Ra and profile deviation of the molded lenses were analyzed, and simulation and experimental results were also compared to verify the validity of simulation model and its results. Simulation results show that the stress was the smallest when cooling gap is 0.1 mm, which is 3.897 MPa. The profile deviations of molded lens ASP1 and ASP2 were 1.054 m and 0.858 m, respectively. The experimental results show that surface quality of molded lens with cooling gap of 0.1 mm was the best. The PV values of ASP1 and ASP2 are 170.8 nm and 223.6 nm respectively, Ra values are 22.7 nm and 24.9 nm respectively, and maximum profile deviations are 0.896 m and 0.738 m respectively. Therefore, minimum cooling gap is 0.1 mm. The simulation results showed good agreement with experimental results. The cooling gap has some influence on molding quality of small diameter dual aspherical chalcogenide glass lenses. The determination of minimum cooling gap can effectively improve surface quality of molded lenses.
2018, 47(11): 1142002.
doi: 10.3788/IRLA201847.1142002
To realize the engineering application of the high frequency and high precision tiling error compensation, a novel method for error compensation of large-aperture tiled-grating compressor was presented by using a small-aperture mirror. The relationship between the amount of mirror compensation and the tiling error was analyzed for two-pass Z-type compressor. The influence of the compensated tiling error on the focus energy was quantitatively compared with the numerical simulations, which was combined with the ray-tracing method and principle of Fraunhofer far field diffraction. The validity was verified and the error tolerances for direct drive and mirror compensation were obtained. The results show that this method can decrease the precision demand significantly for tiled-grating.
