Laser Position Research Articles

Monitoring and Control of Irradiation with Carbon Ions During Radiobiological Experiments at the RBS Experimental Set-Up

The RBS experimental set-up has been working in every accelerator session of the U-70 accelerator complex since 2015. The main users of the set-up are radiobiologists and physicians. The direction of research is radiobiological experiments with extracted beams of accelerated carbon ions and preclinical studies aimed at the development of domestic methods of ion therapy. The requirements for irradiation of samples with carbon ions are very high: irradiation uniformity is no worse than 95%, positioning accuracy is no worse than 0.1 mm, dose delivery accuracy is no worse than ±2.5%. The article describes the instruments and devices that are used to support radiobiological experiments at the RBS installation: a plane-parallel ionization chamber, a mosaic ionization chamber, a water phantom with a 3D movement system, a 6-axis table, a degrader, a laser positioning system, clinical dosimeters. Programs for working with this equipment and archiving the data obtained are described.

Application and Prospect of Strapdown Inertial Navigation System in Coal Mining Equipment.

In recent years, with the rapid construction of a safe, clean, efficient and sustainable modern energy system, the intelligence of coal mining has become the inevitable direction of the development of the coal mining industry. The intelligence of coal mining system and equipment is the core of intelligent mining, and the positioning technology of mining equipment is the key to underground intelligent mining. The strapdown inertial navigation system can make up for the shortcomings of traditional GPS positioning systems and laser positioning because of its strong anti-interference, high precision and real-time monitoring, and ability to carry out real-time dynamic positioning of mining equipment in underground coal mines. This paper briefly introduces the basic principle of the strapdown inertial navigation system, analyzes the application of the existing strapdown inertial navigation system in mining equipment, and lists and analyzes the research status of the improvement strategy of the inertial navigation system, such as zero speed correction and integrated navigation technology. Finally, by analyzing the application and future development trend of inertial navigation systems in mining equipment, this paper provides more data and method support for the positioning of mining equipment in the future.

Femtosecond laser assisted cataract surgery in a cataract patient with low vaulted ICL following LASIK: a case report

BackgroundApart from the conventional utilization of ICL implantation for the correction of refractive errors, its recent applications extend to correcting refractive errors post laser refractive surgery. Notably, the development of cataracts stands out as a prevalent postoperative complication, often associated with low vault. Previous cases have demonstrated successful management of cataracts with ICL through the combination of FLACS and ICL removal coupled with IOL implantation, resulting in favorable postoperative visual outcomes. Herein, we present a case of cataract with low vault ICL following LASIK and its subsequent management.Case presentationA 46-year-old male presented with vision loss in the right eye for 9 months, and he had undergone LASIK 22 years prior and had ICL implantation in both eyes 2 years ago to correct refractive error. One day after ICL implantation, both eyes exhibited the UDVA of 1.2 and 1.0, well-positioned ICLs, and approximate vault of 150 μm and 200 μm. Six months ago, the patient became aware of blurred vision in the right eye for a duration of 3 months. Examination revealed cloudy lens cortex in the right eye. During the current review, the UDVA of the right eye was 0.6, where nasal wedge-shaped clouding was evident and worsened, while the left eye lens remained transparent. AS-OCT demonstrated the vault of 54 μm in the right eye and 83 μm in the left eye. Considering the patient’s history of LASIK and the presence of right eye cataract, a monovision approach was adopted. The patient underwent FLACS combined with ICL extraction and monofocal IOL lens implantation in the right eye. At 10 days postoperatively, the patient exhibited the UDVA of 1.0.ConclusionsOur report confirms the feasibility of FLACS in managing cataracts in patients with low vault ICL following LASIK. This procedure does not pose significantly greater challenges than in typical cataract cases, although meticulous care remains essential throughout every step of the surgery, particularly during laser scanning and positioning. With adequate preoperative preparation and precise calculation of the IOL power, surgical outcomes can meet expectations fully.

Acoustic emission monitoring of a laser powder bed fusion process

Additive manufacturing (AM) metal parts offers opportunities for various industrial applications. From individual production of spare parts for unique mechanical components to prototyping of complex structures, the possibilities of production using the additive manufacturing process are manifold. One common AM technique is the Laser Powder Bed Fusion (PBF-LB/M) process, where a laser is used to selectively melt metal powder and create the parts layer wise as designed in a model. During manufacturing certain defects like pores, cracks and lack of fusion may be created in the built parts. As AM parts often have complex geometries, a postprocess non-destructive testing is difficult or even not possible. Thus, different optical monitoring techniques are applied to detect flaws during the build process with the aim to detect and repair defects right away during the manufacturing process. However, optical monitoring system require a clear view of the melt pool and quite expensive equipment. Acoustic monitoring by AE sensors attached to the built plate would be a cheaper alternative which also can be used without visual contact to the building chamber. This paper shows a first approach of an AE based process monitoring. The build plate of a PBF-LB/M machine therefore was adapted to hold four AE sensors that are then used to monitor the process. The build process itself creates AE signals caused by the melting and cooling and the mechanical application of powder. The formation of pores and cracks is expected to create additional acoustic emissions that will be distinct from the AE pattern from the printing process. This AE signals can be linked to the different layers of the printed part or in the long run to the laser position. Results from the first tests in a customized LPBF machine will be shown as well as the implementation of AE into the PBF-LB/M machine.

Research on the Positioning and Tracking Technology of Surgical Instruments Based on Laser Localization

Abstract Addressing the complexities and low accuracy of traditional surgical instrument positioning processes, a low-cost, high-precision surgical instrument tracking and positioning strategy is proposed. By integrating the VR laser positioning system, Lighthouse, with oral medicine, the positioning process and principles of the system are elucidated. Based on the initial system calibration, static positioning accuracy tests were conducted, and the positioning and tracking of the surgical instrument endpoints were achieved through the least squares method. Experimental results demonstrate that both static and dynamic positioning errors of the system are less than 0.3mm, meeting the requirements of oral surgical navigation.

Tuning effect and switching behavior of sunlight field on lateral photovoltaic effect of Zn0.95Cu0.05O/p-Si heterojunction

In this paper, the Zn0.95Cu0.05O/p-Si heterojunction with lateral photovoltaic effect (LPE) is prepared that has the tuning effect and switching behavior of sunlight field. The dependence of the lateral photovoltage (LPV) on the laser position shows high sensitivity (20 mV mm−1) and strict linearity. Interestingly, the LPV eventually decreased to 0 mV as the sunlight intensity increased to 48 mW, under the constant laser intensity and position, indicating the application potential of a photo-switch. This light field effect results from the irradiation of sunlight, which changes the position of quasi-Fermi level, reduces the drive power for carriers by the space charge region in the heterojunction, and increases the concentration of carriers resulting in increased the scattering between carriers to decrease the lifetime of carriers produced by the laser. This work can expand the application of LPE in the field of multifunctional devices such as photo-switches, position sensors and self-powered devices.

Local augmentation of phonon transport at GaInN/GaN heterointerface by introducing a graded variation of InN mole fraction

The pump and probe technique in Raman spectroscopy of the E2 (high) mode is exploited to uncover the enhancing factor of the phonon transport across Ga1−xInxN/GaN interfaces. Two samples are investigated: one with a uniform x of 0.09 and another one with a graded variation in x from 0.17 to 0 along the depth direction. Lateral phonon transport is obtained by scanning the 532-nm probing laser from the irradiation position of the 325-nm heating laser. No difference in the lateral diffusion length is observed between the two samples, while the transport probability across the interface is higher for the sample with the graded variation in x than the sample with the uniform x of 0.09. The microscopic images of the decrease in the mode energy or the increase in temperature of the GaN layer reveal that the local phonon transport across the heterointerface is enhanced in regions with low differences in the phonon mode energy between the GaN and GaInN rather than the difference in crystal quality.

Chemically accelerated laser processing of SDSS-2507 uniquely under in-situ prepared environments: A comparative study on material dissolution behavior and surface characteristics

Composed of thermochemical reactions, chemically accelerated laser processing (CALP) is a hybrid process that integrates thermal energy with chemical processes. It uses laser activation of material dissolution in chemical environments via localized temperature gradients for streamlined processing, notably for self-passivating materials. This research sheds light on how the dynamic interaction occurs during the fabrication of multiple patterns on SDSS-2507 uniquely by employing an orbit-in-orbit laser positioning strategy in CALP. Current CALP and fabricated surface feature may be useful for micro-reactor applications. So artificial chemical environments (H3PO4, NaCl, and NaNO3) and their concentration, along with controllable laser processing windows like energy and scan factors, were used to simulate actual CALP conditions to study SDSS-2507′s material dissolution and surface characteristics. As SDSS-2507 holds a dual phase with varied thermal characteristics, this article examined each phase’s sensitivity to laser-induced chemical reactions and attacks from aggressive and non-aggressive ions during CALP. In order to acquire insight into the CALP effect on SDSS-2507, phase analysis, surface morphology, CALP-induced crack behavior, surface chemistry, crystallite size, residual stress, mechanical property, and lattice strain were also studied. In the post-CALP, the SDSS-2507′s resistance against aggressive Cl- ions was also scrutinized through electrochemical corrosion analysis. It has been found that, by taking advantage of orbit-in-orbit scan mode during CALP, NaCl exhibited superior performance in terms of material dissolution rate among the three chemical environments, whereas the H3PO4 environment solely performed well in terms of a clean surface without any leftover residue compared to NaCl and NaNO3. In comparison to NaNO3, NaCl, and before CALP, a decrease in crystallite size of up to 22.49%, 19.12%, and 26.23% was also seen. On top of that, when compared to NaCl, NaNO3, and before CALPed surfaces, the corrosion rate was found to be 62.63%, 19.04%, and 35.84% lower, respectively. The findings suggest that, CALP in H3PO4 environment significantly refines the grains compared to B-CALP. This, in turn, stimulates the CALP to somewhat further strengthen the grain boundary and increase its corrosion resistance.

Experimental Modeling, Statistical Analysis, and Optimization of the Laser-Cutting Process of Hardox 400 Steel.

Fiber laser cutting machines are widely used in industry for cutting various sheet metals. Hardox steel is widely used in the construction of machinery and equipment that are subjected to wear and impact due to its anti-wear properties and good impact resistance. In this experimental study, the effect of input parameters including laser output power (LOP), laser-cutting speed (LCS), and focal point position (FPP) of fiber laser on the surface roughness and kerf width of Hardox 400 steel sheets are studied. In addition, the optimization of input parameters to achieve the desired surface roughness and kerf width are investigated and analyzed using the response surface methodology (RSM). The experiments are performed using a 4 kW fiber laser-cutting machine and the output results including surface roughness and kerf width are measured using roughness meters and optical microscope. The results of the analysis of variance (ANOVA) for surface roughness and kerf width show that the FPP and LCS are the most significant process parameters affecting the surface roughness and kerf width. With a positive focal point, the surface roughness decreases while the kerf width increases. With increasing the laser-cutting speed, both the surface roughness and kerf width decrease.

Flexible automated system for laser modified layer by layer assembly.

An open-source automated system for laser modified layer by layer assembly is described. This flexible system, the first designed to be used with this process, can be used to fabricate a range of laser patterned, layer by layer thin films. The Arduino microcontroller-based system features a stepper motor-controlled turntable that holds solutions and water rinses for dipping. The substrate can be moved vertically to be dipped into each of the solutions throughout the process. A semiconductor laser is used to modify the thickness of the thin film during the chosen dipping cycles. Several aspects of the robotic system are easily controlled via software, including the average laser power, irradiation time, horizontal laser position, and vertical substrate position. The system is fully automated and, once started, does not require any user interaction. To demonstrate the capability of the automated system for patterning, electrochromic thin film devices using 50-bilayer laser patterned films using the polymers poly(allylamine hydrochloride) and sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] are presented. One device is patterned with the shape of a large "C," created by irradiating the sample (55 mW average power, 405nm) while the substrate was moved vertically up and down or the laser was moved horizontally. The laser irradiates the sample during only the dipping in the polycation polymer solution. A second electrochromic thin film device is based on a sample with five parallel laser patterned lines, where each line is fabricated with different average laser powers and, hence, different thicknesses. The thicknesses of the lines vary by about 30nm.

A Pulsed Ultraviolet Laser Positioning System Based on 4H-SiC Four-Quadrant Photodetectors

A Pulsed Ultraviolet Laser Positioning System Based on 4H-SiC Four-Quadrant Photodetectors

Off-plane quartz-enhanced photoacoustic spectroscopy.

In this work, we developed off-plane quartz-enhanced photoacoustic spectroscopy (OP-QEPAS). In the OP-QEPAS the light beam went neither through the prong spacing of the quartz tuning fork (QTF) nor in the QTF plane. The light beam is in parallel with the QTF with an optimal distance, resulting in low background noise. A radial-cavity (RC) resonator was coupled with the QTF to enhance the photoacoustic signal by the radial resonance mode. By offsetting both the QTF and the laser position from the central axis, we enhance the effect of the acoustic radial resonance and prevent the noise generated by direct laser irradiation of the QTF. Compared to IP-QEPAS based on a bare QTF, the developed OP-QEPAS with a RC resonator showed a >10× signal-to-noise ratio (SNR) enhancement. The OP-QEPAS system has great advantages in the use of light emitting devices (LEDs), long-wavelength laser sources such as mid-infrared quantum cascade lasers, and terahertz sources. When employing a LED as the excitation source, the noise level was suppressed by ∼2 orders of magnitude. Furthermore, the radial and longitudinal resonance modes can be combined to further improve the sensor performance.

Performance evaluation of computed tomography scanners in Indonesia: recommendation from a nation-wide study.

In this study, an evaluation of the compliance test data from 684 computed tomography (CT)-scanners in Indonesia for the 2019-22 test period was carried out. The study was aimed to describe the performance profile of CT-scanners in Indonesia and evaluate the testing protocol. A total of 87.8% of the CT-scanners unconditionally passed the tests, 8.8% passed the tests with conditions and 3.4% failed the tests. Of the devices conditionally passed the tests, the top two causes were water CT number accuracy (45.2%) and laser position accuracy (41.9%). Meanwhile, 75.0% of the failed devices were due to failing to meet the patient dose test criteria. The failure of the test for the water CT number accuracy parameter was caused by variations in the type of phantom used in the test, where several types of phantoms did not use water as material of the homogeneity module. Failures in laser position accuracy test were caused by the passing criteria that adjust to the minimum slice thickness, so that modern CT-scanner with small detector sizes and collimations tend not to pass. On the other hand, the failure on dose aspects was due to the frequent unavailability of baseline values for comparison. Of these top three failure causes, two of them, namely the CT number and dose test parameters, have been accommodated in the latest regulation (BAPETEN Regulation No. 2/2022) with a change in the evaluation method, while for the laser position accuracy test it is recommended to alter the passing criteria to an absolute value, namely 1mm.

Skin marker combined with surface-guided auto-positioning for breast DIBH radiotherapy daily initial patient setup: An optimal schedule for both accuracy and efficiency.

By employing three surface-guided radiotherapy (SGRT)-assisted positioning methods, we conducted a prospective study of patients undergoing SGRT-based deep inspiration breath-hold (DIBH) radiotherapy using a Sentine/Catalys system. The aim of this study was to optimize the initial positioning workflow of SGRT-DIBH radiotherapy for breast cancer. A total of 124 patients were divided into three groups to conduct a prospective comparative study of the setup accuracy and efficiency for the daily initial setup of SGRT-DIBH breast radiotherapy. Group A was subjected to skin marker plus SGRT verification, Group B underwent SGRT optical feedback plus auto-positioning, and Group C was subjected to skin marker plus SGRT auto-positioning. We evaluated setup accuracy and efficiency using cone-beam computed tomography (CBCT) verification data and the total setup time. In groups A, B, and C, the mean and standard deviation of the translational setup-error vectors were small, with the highest values of the three directions observed in group A (2.4±1.6, 2.9±1.8, and 2.8±2.1mm). The rotational vectors in group B (1.8±0.7°, 2.1±0.8°, and 1.8±0.7°) were significantly larger than those in groups A and C, and the Group C setup required the shortest amount of time, at 1.5±0.3min, while that of Group B took the longest time, at 2.6±0.9min. SGRT one-key calibration was found to be more suitable when followed by skin marker/tattoo and in-room laser positioning, establishing it as an optimal daily initial set-up protocol for breast DIBH radiotherapy. This modality also proved to be suitable for free-breathing breast cancer radiotherapy, and its widespread clinical use is recommended.

Combined 3D scanning measurement method based on guidance of full-space laser positioning system

Combined 3D scanning measurement method based on guidance of full-space laser positioning system

Goniometric accuracy and compensation methods for full-space laser positioning systems

The accurate large-scale positioning system is a novel full-space laser positioning system that has the advantages of automatic and multi-node parallel measurement and sub-millimeter positioning accuracy, and it has become an important component in the digital manufacturing of large equipment. Goniometric accuracy is particularly important for the evaluation of system function and accuracy improvement. An improved goniometric accuracy calibration method is proposed to assess the goniometric accuracy by using multiple measurement points to fit the mapping relationship between the goniometric measurement of the system and the goniometric measurement of the multi-tooth indexing table. The feasibility of the accuracy assessment method is verified by establishing a geometric model and performing modeling and simulation analysis. The method is verified using an all-space laser positioning system, and the dynamic performance of the base station is optimized to improve the overall goniometric accuracy. The maximum value of the goniometric error is 0.008″ and the goniometric accuracy is 0.026″ after fitting the curve by the mapping relation, demonstrating high stability, and the fluctuation of the goniometric error after optimization is improved from the original ±15″ to ±7.5″, verifying the effectiveness of the goniometric compensation method. This method solves the problem of coaxiality calibration in goniometric evaluation and provides the basis for the traceability of the goniometric accuracy.

In Situ Real-Time Observation of Photoinduced Nanoscale Azo-Polymer Motions Using High-Speed Atomic Force Microscopy Combined with an Inverted Optical Microscope.

High-speed atomic force microscopy (HS-AFM) is an indispensable technique in the field of biology owing to its imaging capability with high spatiotemporal resolution. Furthermore, recent developments established tip-scan stand-alone HS-AFM combined with an optical microscope, drastically improving its versatility. It has considerable potential to contribute to not only biology but also various research fields. A great candidate is a photoactive material, such as an azo-polymer, which is important for optical applications because of its unique nanoscale motion under light irradiation. Here, we demonstrate the in situ observation of nanoscale azo-polymer motion by combining tip-scan HS-AFM with an optical system, allowing HS-AFM observations precisely aligned with a focused laser position. We observed the dynamic evolution of unique morphologies in azo-polymer films. Moreover, real-time topographic line profile analyses facilitated precise investigations of the morphological changes. This important demonstration would pave the way for the application of HS-AFM in a wide range of research fields.

Pose Control of Millimeter-Scale Objects in a Laser-Powered Thermocapillary Manipulation Platform

The miniaturization of technological components requires tools capable of manipulating them. Noncontact micromanipulation has recently gained popularity since it minimizes component damage and adhesion problems. However, the simultaneous position and orientation (pose) control using noncontact tools remains an open challenge. In this work, we propose the pose control of millimeter-scale structures at the air–water interface using laser-powered thermocapillary flows. We achieve autonomous pose control by steering two laser spots around the structure in a closed-loop manner. The controller consists of a linear pose controller and a model inversion. The pose controller defines the required force and torque to reach the target. The model inversion defines the required laser positions to obtain said force and torque. This inversion is performed with an optimization algorithm, without any prescribed strategy. The pose stabilization was validated experimentally, obtaining a position and orientation precision of 0.15 body lengths and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{\circ }$</tex-math></inline-formula> , respectively. Additionally, we show the experimental path-following with independent orientation control, obtaining a similar position precision.

Design, Development and Commissioning of the Boldrewood Towing Tank – A Decade of Endeavour

The process of design, build and eventual commissioning of the towing tank on the Boldrewood Innovation Campus is described. The design brief required a facility that would have a capability to test models at a commercial scale but that would be effective as teaching environment for the next generation of Naval Architects as well as providing a flexible space for future fundamental research. Each of these provided their own challenges but the eventual solution of a 138 m long, 3.5 m deep, 6 m wide facility has more than met the initial aspirations. Equipped with 12 independent 0.5 m wavemaking flaps at the West end, a passive beach at the East end, a deployable side beach along the South wall for post run wave absorption and a monocoque Aluminium alloy carriage, the Boldrewood towing tank has now been successfully operating for more than a year. The carriage position and speed are controlled by a twin winch arrangement using a laser positioning system and low embodied energy composite cables. The carriage can reach a maximum speed of 10 m/s with controllable acceleration rates and can have up to four constant speed phases per run. Initial commissioning results and comparisons with benchmark data for the KCS hull confirm the accuracy and repeatability of the facility. In particular, the position and speed of the carriage are known to a high level of precision. To date research and consultancy work has spanned the performance of high speed vessels, uncrewed underwater and surface vessels, wave energy and tidal current systems, floating platforms for wind turbines, performance sport work for sailing, kayaking, rowing and swimming, open water propeller tests as well as conventional displacement vessel testing for self-propulsion and resistance. All ship science and maritime engineering students use the facility as part of their taught modules in every year of their programme as well as for individual, MSc and group projects as appropriate. It has also made a strong impact on the many thousands of visitors a year to the campus for science and engineering open days.

Laser Positioning Method Based on Line Endpoint Direction Matching

Laser Positioning Method Based on Line Endpoint Direction Matching