Scan Pitch Research Articles

Laser machining micro-structures on diamond surface with a sub-nanosecond pulsed laser

Micro-structure surface on diamond material is widely used in a series of industrial and scientific applications, such as micro-electromechanical systems (MEMS), nanoelectromechanical systems (NEMS), microelectronics, textured or micro-structured diamond machining tools. The efficient machining of micro-structure on diamond surface is urgently demanded in engineering. In this paper, laser machining square micro-structure on diamond surface was studied with a sub-nanosecond pulsed laser. The influences of laser machining parameters, including the laser power, scanning speed, defocusing quantity and scanning pitch, were researched in view of the ablation depth, material removal rate and machined surface topography. Both the ablation depth and material removal rate increased with average laser power. A reduction of the growth rate of the two parameters was induced by the absorption of the laser plasma plume at high laser power. The ablation depth non-linearly decreased with the increasing of the scanning speed while the material removal rate showed an opposite tendency. The increasing of the defocusing quantity induced complex variation of the ablation depth and the material removal rate. The maximum ablation depth and material removal rate were achieved at a defocusing position. The ablation depth and material removal rate oppositely varied about the scanning pitch. A high overlap ratio was meaningful for achieving a smooth micro-structure surface topography. Laser machining with a large defocusing quantity, high laser power and small scanning pitch was helpful for acquiring the desired micro-structure which had a large depth and smooth micro-structure surface topography.

Efficiency improvement of thin-sheet-metal bending by femtosecond laser peen forming

Femtosecond laser peen forming is die-less incremental sheet forming using laser induced shock waves. It was applied to bending of thin sheet micro parts. When severe curvatures are requested, the process needs dense laser pulse irradiation, which reduces sheet thickness remarkably owing to excessive laser ablation. High bending efficiency per pulse is necessary to realize a small radius of curvature without sheet thickness reduction. The authors attempted to improve the bending efficiency by changing scanning velocity and scanning pitch. Optimized scanning achieved 40% smaller radius of curvature than conventional one, in spite of same irradiated pulse density. Obtained knowledge is effective in miniaturization and productivity increase.

Application of Dual-Source CT TurboFlash Coarse Pitch Scanning in Coronary Artery Imaging

Objective: To compare and analyze the image quality and radiation dose of three scanning modes of dual-source CT coronary artery retrospectively, and to discuss the application value of TurboFlash coarse pitch scanning mode. Methods: The imaging data of 100 patients who underwent CT coronary angiography (CCTA) using Siemens force CT retrospective gated triggering spiral scan (RES-SPIRAL), adaptive prospective gated triggering sequence scan (SEQ) and prospective coarse pitch scan (TurboFlash) retrospectively was collected. The image quality was evaluated by objective and subjective methods. The effective radiation dose of patients was compared and analyzed, and the indications of the three scanning modes were analyzed. The application value of dual-source CT TurboFlash coarse pitch scanning in coronary artery imaging was evaluated. Results: The results showed that the left main coronary artery, the right coronary artery and their tertiary branches could be clearly displayed in the three groups of images: the left anterior descending branch, the left circumflex branch, and their three-level branches. There was no statistical difference in subjective image quality among the three groups of pictures (P > 0.05). There was no statistical difference in objective evaluation indexes, such as CT value, SNR, CNR and Noise among the three groups (P > 0.05). The patient radiation dose results showed that the effective radiation dose ED of RES-SPIRA scan was (9.22 ± 1.33) mSv. The dose of SEQ was (2.88 ± 2.47) mSv, and the dose of TurboFlash was (0.51 ± 0.16) mSv. There was significant difference in comparison of the three groups (P 0.05). RES-spiral scanning had the highest radiation dose and TurboFlash coarse pitch scanning (TurboFlash) had the lowest radiation dose. Conclusion: TurboFlash coarse pitch scanning is low in dosage, fast in speed and wide in adaptability. It is especially suitable for the elderly, children, coma and other patients who cannot cooperate with breath-holding examination, as well as for the screening and examination of coronary artery diseases in asymptomatic population. Undoubtedly, it is a worthy method of heart coronary artery examination.

Monte Carlo based analysis of confocal peak extraction uncertainty

Localisation of axial peaks is essential for height determination in confocal microscopy. Several algorithms have been proposed for reliable height extraction in surface topography measurements. However, most of these algorithms use nonlinear processing, which precludes estimating the peak height uncertainty. A Monte Carlo based standard uncertainty analysis model is developed here to evaluate the precision of height extraction algorithms. The key parameters of this model are the vertical sampling deviation and the size of the scanning pitch. Height extraction uncertainty of the centroid algorithm and nonlinear fitting algorithms were calculated using simulations. Our results offer a reference for selecting algorithms for confocal metrology.

Internal Structure Research of Shungite by Broadband Ultrasonic Spectroscopy

The internal structure of plane-parallel plates of shungite is studied. The broadband ultrasonic pulses are used to measure the velocities of longitudinal and shear elastic ultrasonic waves. The accuracy of measurements is 0.3% in the case of longitudinal wave velocity and 0.5% in the case of shear wave velocity (scanning pitch over the surface of specimens was 0.5 mm). Local elastic moduli of shungite (Young modulus, shear modulus and Poisson's ratio) are uniquely determined from the velocities of elastic waves.

Detectability of corrosion damage with circumferential guided waves in reflection and transmission

There is an increasing interest in high frequency short range guided waves to screen or monitor for corrosion. This contrasts with long range guided waves (LRGWs) which screen pipes for large patches of corrosion and have been successfully used in corrosion management for the past twenty years. The fundamental setup described in this paper uses circumferential guided waves, which are excited at a single location on a pipe and travel around the pipe wall and are detected at the same location. The study uses a finite element model assisted method to evaluate the detection capability of two short range circumferential guided wave setups which use both the reflected and transmitted signals. The setups themselves consist of either an axial array of transducers, for monitoring, or a single transducer which axially scans a pipe. Both setups have an array or scan pitch between either adjacent transducers or measurements. The detection capability of the fundamental Lamb wave modes (A0 and S0) in both reflection and transmission have been compared, as well as a hybrid shear horizontal wave setup, which uses the SH0 mode in reflection and the SH1 mode in transmission. A sensitivity analysis was conducted using two separate methods to determine the probability of detection (POD) for either the reflection or transmission signals. Both methods determine a POD for a specific defect, noise level, and array or scan pitch. Probability images are produced which map the POD for a range of defect sizes. For the parameters investigated in this study, it was found that in transmission large diameter defects have a higher detectability, whereas deep, narrow diameter defects are more detectable in reflection. A generalised overview of the sensitivity of short range guided waves is presented by combining both the reflection and transmission PODs. The data fused sensitivity of the S0 and SH hybrid modes are given as 0.6% and 0.75% cross sectional area (CSA) respectively, allowing for the comparison with LRGWs. The A0 mode was excluded from the POD analysis because it was much less sensitive than the other two modes.

A method to improve the quality of 2.5 dimensional micro-and nano-structures produced by focused ion beam machining

The present work deals with a new technique to produce complex micro- and nano-scale patterns with high accuracy by FIB micro machining. The proposed method is related to the production of stream file, which is optimized through a software interface. A unique sampling approach is used to optimize the conversion from a 3D meshed CAD object to the focused ion beam (FIB) digital to analogue converter (DAC). The method uses a novel scan strategy, sensitive to the pattern local geometry and size, to define the optimal ion beam path, dwell time and the scanning pitch. This not only allows to minimize the redeposition but also to obtain accurate and scalable milling routines. In order to show the applicability of the method, a hemisphere and a pyramid shape are milled and compared to the shapes obtained using the conventional techniques. Results show that the method is very effective in producing complex shapes while overcoming the detrimental effect of conventional raster/serpentine FIB strategies, such as redeposition. Lastly, a fish-net structure with a pitch of ∼200nm as well as a series of truncated cones with sub-micrometrical details are realized to show the potential impact of this new method. Results show that a spatial resolution of less than 100nm is achievable with the help of this method.

The effect of ultraviolet on direct current potentials of the human skin

Aim of the study. investigation of the suntan on the level of omnipresent electrical potential of skin in frames of development of the hypothesis about the melanocyte participation in skin electrical activity formation. Material and methods. 11 men and 11 women on summer holyday took part in investigation. The relationship between the levels of skin omnipresent electrical potential and the reflection factor were investigated. The omnipresent electrical potentials were registered as the potential differences between the two areas on skin using the Orion 261S pH meter and the liquid Ag/AgCl electrodes of the same company. The reflecting factor was estimated with the help of the spectroradiometer LI-1800 (“LI-COR”) using the included intgrational sphere 1800-12 coated with barium sulfate. Hole size was 1,45 cm. The reflection factor was estimated at the wave band 375-800 nanometers with the scanning pitch 1 nm. Main results. There is a mathematical relation between the magnitudes of potential differences and the reflection factors of the areas of sunburnt skin and the areas of the skin not affected with sun at wave light 620-729 nm. The relationship could be approximated in linear equation. Spearman correlation factor between these two parameters was -0,43 (p = 0,045), between the differences in levels of skin omnipresent electrical potential and the reflection factors of the sunburnt skin was r = -0,52 (p = 0,01), between the differences of the electrical potentials of sunburnt skin and the skin not affected with sun was r = -0,28 (p = 0,2). The presented results of investigation and the data from literature allow to conclude that there is a positive correlation between the level of omnipresent electrical potential of skin and the quantity of melanosomes filled with melanin. Conclusion. It is suggested that melanocytes take part in formation of the skin electrical activity via melanosomes filled with melanin. At the same time the melanocyte contribution in skin electrical activity is not assessed.

超短パルスレーザーピーンフォーミングによる薄板曲げにおける曲率半径の微小化

Ultrashort-pulsed laser peen forming is a method of thin-sheet-metal forming using laser-induced shock waves. The authors have applied the process to microsheet parts bending, which is accomplished by repeating line scanning. However, when a severe curvature is requested, nonnegligible reduction of sheet thickness is induced by laser ablation. In order to restrict the thickness reduction, the authors attempted to improve the bending efficiency, which would allow a reduction in the number of necessary pulses. Scanning velocity and scanning pitch were changed, while the total irradiated pulse number was constant. The obtained results showed that a scanning velocity higher than the conventional one is favorable for improving the bending efficiency. In addition, smaller scanning pitches were adopted to reduce the radius of curvature. The influence of the scanning pitch on the bending efficiency was much weaker than that of scanning velocity. From the results of the evaluation of efficiency and scanned surface asperity, a scanning velocity of 20 mm·s-1 was judged to be the best. The best scanning condition achieved a 40% smaller radius of curvature than the conventional one.

Surface Morphology Evolution Induced by Multiple Femtosecond Laser Ablation on 4H-SiC Substrate and Its Application to CMP

4H silicon carbide (SiC) substrates were processed by multiple femtosecond (fs) laser ablation. Its surface morphologies changed dramatically at different scanning pitches, different scanning velocities, different repetition rates and near-threshold fluence. The evolution of surface morphologies and the uniformity of rippled structures were respectively investigated and discussed. The overlapped zones of adjacent pulses were focused in discussion. In the case of high repetition rate, periodic ripples with average spatial periodicities ranging from 145 nm to 196 nm were induced; whereas in the case of lower repetition rate, coarse ripples (roughly 440 nm) and fine ripples (about 117 nm) were simultaneously formed. Large amount of agglomeration was fabricated in the case of scanning pitch 0.05 μm and scanning velocity ≤ 5 mm/s. At near-threshold fluence, 4H-SiC surface was partly ablated. When the rippled structures induced in Transverse Irradiation Mode were further ablated in Cross Scanning Mode, horizontal ripples changed into vertical ripples. X-ray diffraction and Raman spectra were utilized for surface analysis. Confirmatory experiment was carried out, demonstrating that chemical mechanical polishing (CMP) process could be promoted by fs laser ablation.

On the probability of detecting wall thinning defects with dispersive circumferential guided waves

Two ultrasonic techniques are well established for pipe inspection and monitoring: highly sensitive ultrasonic spot thickness measurements, which can be presented in C-scan form, or low frequency guided waves that rapidly screen large areas for big defects. Recently there has been a growing interest in pipe inspection and monitoring systems exploring the middle ground between these two techniques by using higher frequency guided waves over shorter distances. In this paper the use of an axial transducer array (more suitable for monitoring applications) or a single axially scanned transducer (more suitable for inspections) that sends and receives dispersive circumferential guided waves around a pipe has been studied. The presence of a defect is detected as a result of a change in the wave travel time around the pipe circumference as a result of the thickness reduction. Both measurement modalities have a pitch between adjacent transducers/measurements. By approximating the pipe to a plate, a finite element model assisted method to evaluate the detection capabilities (probability of detection-POD) of this short range guided wave technique as a function of scan or transducer pitch is presented. The performance of three guided wave modes (A0, S0, and SH1) are compared in a 10mm thick plate. The results help to optimize the pitch and defect sensitivity of the setup. For the parameters investigated in this study, it was found that the S0 mode, at 2MHz.mm, is the most suitable for detecting wide shallow defects. For the same detection capabilities a much wider pitch can be used for S0 mode transducers as compared to SH1 mode transducers. Whereas the SH1 mode, at 3MHz.mm, is better suited to detecting narrow and deep defects using a relatively small pitch. The S0 mode is much less sensitive to these defects. The A0 mode was excluded from the POD analysis because it had a much higher variability in average thickness measurements, at comparable SNRs, compared to the other two modes.

Monte Carlo modeling of cavity imaging in pure iron using back-scatter electron scanning microscopy

Backscattered electrons (BSE) in a scanning electron microscope (SEM) can produce images of subsurface cavity distributions as a nondestructive characterization technique. Monte Carlo simulations were performed to understand the mechanism of void imaging and to identify key parameters in optimizing void resolution. The modeling explores an iron target of different thicknesses, electron beams of different energies, beam sizes, and scan pitch, evaluated for voids of different sizes and depths below the surface. The results show that the void image contrast is primarily caused by discontinuity of energy spectra of backscattered electrons, due to increased outward path lengths for those electrons which penetrate voids and are backscattered at deeper depths. Size resolution of voids at specific depths, and maximum detection depth of specific voids sizes are derived as a function of electron beam energy. The results are important for image optimization and data extraction.

Azimuthal angle- and scanning pitch-dependent colorization of metals by ultrashort laser pulses

We report the modification of optical properties of 304 stainless steel surfaces by femtosecond laser direct writing with different scanning pitches. Regularly arranged ripples with a spatial period of ~700 nm were obtained, rendering vivid structural colors when we illuminated the surface with white light. Diffraction spectra were generated to investigate the spectral properties of the structural colors. Results indicate that the diffraction maximum strongly depends on scanning pitch and azimuthal angle, but that the central wavelength is insensitive to both of them. The reflectance properties were also investigated. This study adds a new parameter, the scanning pitch, to the list of parameters in the production of controllable colorized metal, which may find a range of applications in color display, decoration, and so on.

Height Resolution of Antibody Spots Measured by Spinning-Disk Interferometry on the BioCD

Spinning-disc interferometry (SDI) is a high-speed laser scanning approach to surface metrology that uses common-path interferometry to measure protein spots on a BioCD disk. The measurement sensitivity depends on the scanning pitch and on the time-base. Based on high-resolution laser scanning images of printed antibody spots, we quantify the protein sensitivity as a function of the scan parameters. For smoothly printed antibody spots scanned with a transverse spatial resolution of 1 μm, the surface height precision for a single 100 μm diameter protein spot is approximately 1 pm. This detection sensitivity sets the fundamental limit of detection for label-free BioCD biosensors performing immunoassays.

Femtosecond laser cleaning the surface of reflective mirror in telescope

Metallic mirror is the core component of the imaging system in the reflective astronomical telescope. However, because the telescopesare usually located in the wild, they are often contaminated by dust and other pollutants which will greatly reduce the imaging quality. Therefore, the surface of reflective mirror in telescope should be cleaned routinely in order to recover high performance of telescope. Currently, the artificial ice cleaning is the most common method employed in the cleaning of mirror surface, which is complicated and costly. Besides, the micron particles adhered on the surface of the mirror are especially difficult to be removed by dry ice flow when their diameters are less than 20 μ m because of the Van der Waals force between the particles and metal mirror. Moreover, an ordinary method with wipe and cleanser is also used in which the friction between wipe and mirror may damage the telescope. To overcome these shortcomings, this work proposed a laser cleaning strategy in which amplified femtosecond pulsed lasers was used to clean the reflecting mirror surface. As a new cleaning method, laser cleaning technology which is non-contact and frictionless has been applied successfully in the cleaning of industrial molds, buildings, precision machinery components. For the advantages of femtosecond laser, such as short pulse duration, small thermal effects, high pulse energy, it has been used in the cleaning of cultural relics and has good achievement in recent years. This article firstly studied the interaction between the femtosecond laser and the reflective aluminum mirror. The laser damage threshold of aluminum mirror was measured about 60 mJ/cm2, which would reduce to 57 mJ/cm2 for dirty mirror because of the microparticles adhered on the surface of reflector mirror. Then, by optimizing laser parameters including the scan rate, the scan pitch, and the laser energy, it could be found that when the laser energy density ranges from 30 to 55 mJ/cm2, micron dust particles with diameters less than 20 μ m on mirror surface could be cleaned with excellent clean effect and the reflectivity in the visible light region has been greatly improved. Finally, through the dust particles and aluminum mirror substrate spectrum analysis, we ruled out that the removed microparticles were thermal melted by laser energy. The results indicated that thermal expansion plays the key role in laser cleaning of metal mirror. This work shows that femtosecond laser cleaning has a good effect on the removing of micron particles. As a simple and easy way, femtosecond laser cleaning has a good prospect in cleaning of astronomical telescope.

Selective electrode patterning of ITO films using pulsed ultraviolet laser

A method combining laser annealing and chemical etching is proposed for the selective patterning of indium tin oxide (ITO) films. ITO films with a thickness of 100 nm are deposited on glass using a radio frequency magnetron sputtering system. The as-deposited films have a transmittance of 75 % at a wavelength of 550 nm and a sheet resistance of 81 Ω/□. The ITO films are annealed using an ultraviolet (UV) laser system and are then immersed in oxalic acid etchant. It is found that the laser annealing process readily induces micro-cracks or voids in the ITO thin films, and therefore prompts electrical failure. However, through an appropriate specification of the scanning pitch, laser pulse energy and overlapping rate, the optoelectronic and crystalline properties can be significantly improved. Under the optimal annealing conditions, the transmittance is increased to 82 % and the sheet resistivity is reduced to 50 Ω/□. Notably, the surface roughness of the corresponding etched sample is just 1.5 nm, while the residual stress is equal to 417 MPa.

Advanced researches of additive manufacturing for medicine in Japan

Advanced researches of additive manufacturing for medicine in Japan

レーザ誘起湿式改質における走査ピッチが純チタン表面の改質層形成に及ぼす影響

レーザ誘起湿式改質における走査ピッチが純チタン表面の改質層形成に及ぼす影響

Optimalisasi Citra dalam Penghitungan Calsium Scoring dengan Variasi Scan Type dan Slice Thickness (Studi Pendahuluan Dilakukan Dengan Menggunakan Modifikasi Phantom Thorax di RS Telogorejo Semarang)

Background : Examination of Calcium scoring in Radiology Departement Telogorejo Hospital Semarang using CINE scan type and recon phase images using a slice thickness of 2.5mm, this affect will be plaque with small size cann’t to calculate. Aim : The Purpose of this study was to determine the variation of parameters of calcium scoring MSCT scan examination right in calculating optimal plaque.Methods : The study was preceded by Pre experiments using a thorax phantom with an added 3-calcium artificial heart is likened to the RCA, LCX, LAD and have determined the weight and volume. Experiments with 10 patient samples by applying the best parameters from the pre experiment. Statistical analysis of the results of research conducted by Paired T-Test, while the assessment of the quality radiographs evaluated by an expert in this specialist radiology by providing anatomical criteria scores with 3 choices of items (not clear = 1, is quite clear = 2 and obvious = 3)Result : The volume of plaque is embedded in the thorax Panthom 900mm3. Results of pre experiments with hellical scan type and pitch of 0.5, 0.9, 1.3 in a score of plaque volume is 104mm3, 67mm3, 60mm3. While the scan type CINE with slice thickness 0.625mm, 1.25mm, 2.5mm produces a score of volume plaque is 880mm3, 878mm3, 867mm3. Further experiments were performed by applying parameters with the best result is CINE scan with variations slice thickness 0,625mm, 1.25mm, 2.5mm. To determine the best parameters assessment of image quality with the results on slice thickness 0.625mm was 2.2 (quite obvious), slice thickness 1,25mm scoring average of 2.7 (quite obvious), and slice thickness 2.5 mm average scoring 2.9 (obviously). While image noise on the slice thickness 0.625mm, 1.25mm, 2.5mm, namely 2.7(very high), 1.6 (low), 1.1 (low).Conclusions : Selected parameters that calculate optimal scoring calcium and low noise image for MSCT scan calcium scoring in Telogorejo Hospital Semarang is Scan type CINE with slice thickness variation 1,25mm

Blackening of metals using femtosecond fiber laser.

This study presents an unprecedented high throughput processing for super-blackening and superhydrophobic/hydrophilic surface on both planar and nonplanar metals surfaces. By using a high pulse repetition rate femtosecond (fs) fiber laser, a light trapping microstructure and nanostructure is generated to absorb light from UV, visible to long-wave infrared spectral region. Different types of surface structures are produced with varying laser scanning conditions (scanning speed and pitch). The modified surface morphologies are characterized using scanning electron microscope and the blackening effect is investigated through spectral measurements. Spectral measurements show that the reflectance of the processed materials decreases sharply in a wide wavelength range and the decrease occurs at different rates for different scanning pitches and speeds. Above 98% absorption over the entire visible wavelength region and above 95% absorption over the near-infrared, middle-wave infrared and long-wave infrared regions range has been demonstrated for the surface structures, and the absorption for specific wavelengths can go above 99%. Furthermore, the processing efficiency of this fs fiber laser blackening technique is 1 order of magnitude higher than that of solid-state fs laser and 4 times higher than that of picosecond (ps) laser. Further increasing of the throughput is expected by using higher repetition and higher scanning speed. This technology offers the great potential in applications such as constructing sensitive detectors and sensors, solar energy absorber, and biomedicine.