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Medical treatments such as high-intensity focused ultrasound, hyperthermic laser lipolysis or radiofrequency are employed as a minimally invasive alternatives for targeted tissue therapies. The increased temperature of the tissue triggers various thermal effects and leads to an unavoidable damage. As targeted tissues are generally located below the surface, various approaches are utilized to prevent skin layers from overheating and irreparable thermal damages. These procedures are often accompanied by cooling systems and protective layers accounting for a non-trivial detection of the subsurface temperature peak. Here, we show a temperature peak estimation method based on infrared thermography recording of the surface temperature evolution coupled with a thermal-diffusion-based model and a time-dependent data matching algorithm. The performance of the newly developed method was further showcased by employing hyperthermic laser lipolysis on an ex-vivo porcine fat tissue. Deviations of the estimated peak temperature remained below 1 °C, as validated by simultaneous measurement of depth temperature field within the tissue. Reconstruction of the depth profile shows a good reproducibility of the real temperature distribution with a small deviation of the peak temperature position. A thermal camera in combination with the time-dependent matching bears the scope for non-contact monitoring of the depth temperature profile as fast as 30 s. The latest demand for miniaturization of thermal cameras provides the possibility to embed the model in portable thermal scanners or medical laser technologies for improving safety and efficiency.

In this paper, we demonstrate a simple, fast and single-step method for fabricating self-enclosed fluidic channels via TPA. Pairs of parallel, polymerized ribs are linked by the subsequent polymerization with correctly predetermined offset between the ribs. The region, where the radicals are initiated but its concentration is below the threshold, we called it a sub-activated region. The subsequent polymerization is triggered by the overlap of the sub-activated regions of the two adjacent ribs. The dimensions of the self-enclosed channels depends on the offset between ribs, the scan speed as well as the laser parameters such as pulse energy, pulsewidth and repetition rate.

To evaluate through roughness parameters measurement the penetration of calcium phosphate stabilized by casein phosphopeptides (CPP-ACP) in the subsurface zone of the incipient caries lesions known in dentistry as white spot lesion (WSL). To our knowledge, there is no data about roughness parameters to evaluate the demineralization-remineralization process in the body of the lesion. WSL was generated in vitro in 10 dental samples and sectioned in half of them (longitudinal section). CPP-ACP was applied on the WSL (3 minutes daily for 60 days). Roughness parameters (Rp and Ra) were measured on the longitudinal section with a laser scanning confocal microscope in the reflection acquisition mode (CLSRM), either in the WSL or sound enamel, before and after applying CPP-ACP. CLSRM is a non-contact method able to detect small irregularities more precisely due to the small spot of laser illumination (0.5 μm). Mixed linear models were carried out, using the treatment as a fixed factor and the tooth as a random factor (significance level 5%). Rp and Ra values in WSL area before applying the remineralization protocol (WSL pre) were significantly higher than in the sound enamel of the same samples. After applying CPP-ACP, Rp and Ra values decreased significantly with respect to the WSL pre and were similar to the values of these parameters in sound enamel. roughness parameters were used as an indirect way to measure the porosity of WSL at subsurface level. The decrease of these parameters could be interpreted as the remineralization of WSL by the ability of CPP-ACP to penetrate the body of the lesion. Clinical significance: WSL is characterized by the loss of minerals from the enamel and an increase in porosity at the subsurface level. The effectiveness of remineralizing substances would be determined by their ability to penetrate the body of the lesion and reduce porosity.

On-machine measurement by a line laser scanner has a great potential in machining large complex components in aerospace and automation applications. This paper proposes a novel approach for path planning of measuring curved surfaces in a 5-axis machine tool, which takes scanning overlap, visual angle, and working distance into consideration. A conformal mapping algorithm is employed to transform a three-dimensional (3D) mesh surface to a 2D parametric plane. The shortest equidistant paths calculated in the 2D plane are transformed into smooth collision-free scanning paths in the 3D surface. The experiments verify that this method can improve the efficiency by 21.4% and the accuracy by 24.9%.

Existing laser scanning approaches for highly reflective surfaces generally require multiple scans to cope with specular reflection. This paper proposes a dual-camera, line-laser scanning strategy ...

We propose an amplitude-modulated continuous-wave laser rangefinder employing Bessel–Gauss beamforming. Our Bessel–Gauss beam was generated by a newly proposed doublet configuration, which is simple and low cost. Such a beam was propagated > 2 m with a mainlobe having the diameter < 1 m m . We have conducted proof-of-concept ranging experiments employing the amplitude-modulated continuous-wave scheme with the Bessel–Gauss beam and obtained ranging results of a measurement distance up to 2 m. To the best of our knowledge, this is the first attempt to apply zeroth-order Bessel–Gauss beamforming to laser rangefinders.

A 3D laser scanning system can achieve the precision of millimetre level in deformation examination of a power line tower; however, it suffers from the high cost of equipment and difficult onsite installation. The Tilt Photography with Unmanned Aerial Vehicle (TP‐UAV) is a relatively lower cost system that offers a more convenient way of 3D measurement; however, with a trade‐off of lower measurement accuracy. In order to take advantage of both technologies and improve the measurement accuracy of the TP‐UAV system, in this research, a 3D laser scanning system is applied as a calibration means for the TP‐UAV to explore the possibility of rapid measurement of the deformation in transmission facilities. A data representation model is proposed for the calibration of the parameters of the TP‐UAV system to make use of the accuracy of the 3D laser scanning, and the systematic error of the TP‐UAV system can be corrected to improve the measurement accuracy by 35%.

In contrast to topographic laser scanning, laser hydrography must take into account the presence of two media. A pulsed laser beam, which enters the water from the air at an oblique angle, is refracted at the air–water boundary in the direction of the plumb line. This change in the direction described by Snellius’ law is caused by a slower speed of the light wave in the water, i.e., the phase velocity. Light scattering caused by turbidity gives rise to further deviations from the straight path. Together, the slower speed and the turbidity-induced path extension cause a longer pulse round trip time in the water than in the air. For an accurate measurement, it is important to correct this propagation time extension. It is a common practice to assume the phase velocity as the velocity for the laser pulses in water. In a dispersive medium, however, the phase velocity is only an approximation of the velocity of a pulse. In media with chromatic dispersion, the pulses propagate with a different velocity, i.e., the group velocity. In water, using the group velocity instead of the phase velocity reduces the range dependent bias of the depth measurement at a laser wavelength of 532 nm by more than 1.5%. We present an easy to perform an experiment, which shows that the group velocity differs so much from the phase velocity that this difference should be taken into account. We further discuss the use of group velocity to explain the depth bias using examples from the literature.

Surfaces processed by scanning with a pulsed laser have an inherent roughness due to the partial overlap of discreet pulses. Experimentally optimising the parameters to minimize roughness is challenging because of the time and effort required. A computational model based on the finite volume method for predicting surface roughness during laser surface processing is presented in this work. The data obtained from a single pulse model is used to predict the surface profile by overlapping the successive pulses based on scanning speed. The model captures numerous physical phenomena such as laser absorption, heating, melting, vaporisation, plasma effects, melt pool flow and solidification, as well as the effect of laser scanning. The surface roughness values (Ra and Rq) obtained using the model are reasonably within the limits of the experimental data. The results reveal that the effect of laser parameters on surface roughness is non-linear. While the ablation depth increases exponentially with a decrease in scan speed, the local maximum and minimum of surface roughness could be in the parameter range's intermediate values. The model developed in this work can be used to optimise the processing time and surface finish in different laser-based surface processing techniques.

In industrial manufacturing of bright steel rods, one important quality factor is the straightness or straightness deviation. Depending on the application, deviations of less than 0.1 mm per meter rod length are desired and can be reached with state-of-the-art manufacturing equipment. Such high-quality requirements can only be guaranteed with continuous quality control. Manual straightness measurements conducted offline using a dial gauge provide accurate results on single positions of the rod. We propose a contactless, optical measurement technique based on laser scanning which has the potential to be used inline during production to inspect all rods over the entire length. Only for calibration of the system the rod needs to be turned around its axis. For the measurement of straightness deviation, it is not required to turn the rod. The method is based on evaluating the intensity signal of the reflected laser radiation against the scan angle. It is shown that in combination with an accurate calibration, this signal can be used to determine the rod’s deviation from a straight rod. We explain the measurement and calibration principle as well as data evaluation. We present the experimental setup and first measurement results on a single position on several samples. For a homogeneous sample surface and neglecting laser drift, accuracy and precision were determined to be in the range of 10–20 μm. We discuss the working principle of a potential inline system.

Purpose : This study was conducted to improve the performance of a low-end f-theta lens for application to laser scanning unit. Methods : A f-theta lens system was newly designed using ZemaxTM program. Results of this study were compared and evaluated in three items, such as spot diagram, ray fan, and Seidel aberrations. Results : The newly designed f-theta lens system reduced the spot size and distortion of the incident laser beam, and particularly its spherical aberration was drastically reduced up to 77%. Conclusion : The f-theta lens system designed in this study has greatly improved overall image quality and performance, and is expected to be applied to laser printer equipment.

The perfect knowledge about the scanned object’s geometry is essential for the empirical analysis of the stochastic properties of terrestrial laser scanners (TLSs). The Bonn reference wall is intended to be used as a reference for TLS quality investigations. Therefore, it is necessary to know the geometry of the wall at each time of scanning to avoid the misinterpretation of possible movements as systematic effects in the scanner. For this reason, we investigate the stability of the Bonn reference wall in this study. This includes the definition of a geodetic datum, the quantification of displacements, and the establishment of a suited deformation model. Since we discover a movement of about 1 mm within one day and up to 7 mm over the year, it is necessary to establish a cause-response deformation model to correct the wall movements in the scans. This study proposes two dynamic deformation models to compensate for the movements of the wall within one day and within a year. Our results show that it is better to measure the initial geometry of the wall each day since 89 % of the relative movements can be reduced to a maximum of 0.25 mm with a standard deviation of 0.16 mm (0.23 mm without modeling). If the shape is not initially known each day, the standard deviation of the displacements can be reduced from 1.10 mm to 0.61 mm, but the largest residuals still amount up to 2.5 mm, which is not sufficient for stochastic TLS investigations.

The urgent need to improve performance in the construction industry has led to the adoption of many innovative technologies. 3D laser scanners are amongst the leading technologies being used to capture and process assets or construction project data for use in various applications. Due to its nascent nature, many questions are still unanswered about 3D laser scanning, which in turn contribute to the slow adaptation of the technology. Some of these include the role of 3D laser scanners in capturing and processing raw construction project data. How accurate is the 3D laser scanner or point cloud data? How does laser scanning fit with other wider emerging technologies such as Building Information Modelling (BIM)? This study adopts a proof-of-concept approach, which in addition to answering the afore-mentioned questions, illustrates the application of the technology in practice. The study finds that the quality of the data, commonly referred to as point cloud data is still a major issue as it depends on the distance between the target object and 3D laser scanner’s station. Additionally, the quality of the data is still very dependent on data file sizes and the computational power of the processing machine. Lastly, the connection between laser scanning and BIM approaches is still weak as what can be done with a point cloud data model in a BIM environment is still very limited. The aforementioned findings reinforce existing views on the use of 3D laser scanners in capturing and processing construction project data.

The main purpose of this work is the evaluation of the potential of Terrestrial Laser Scanning (TLS) technology to perform a reflectance analysis of scanned objects. A laser beam, having a coherent beam in the field of visible light (wavelength between 532nm and 680 nm), can lead to optical diffraction phenomena that allow a correlation between the degree of crystallinity of solids (in particular dispersed crystalline materials) and its reflectivity. Different materials with known crystallinity values have been examined and the diffraction value has been analysed for two types of lasers, one pulsed and the other phase measurement, with two different acquisition conditions (nadiral and oblique position). The results demonstrated the correlation by verifying that the incident laser light beam is more refracted by materials with a higher degree of crystallinity than less crystalline or amorphous materials.

The laser scanning confocal microscope head can axially move and perform z-slicing. The presented confocal microscope head is composed of (1) an optical fiber bundle, (2) a custom-designed mechanical housing and lastly, (3) an embedded electronic system to control the head and gather images from the samples. The dimensions of the housing are 88 × 160 × 110 mm; and it is 3D printed with 30% filling ratio using standard PLA 3D printing material. The presented handheld confocal microscope is capable of moving with 1 µm step size back and forth in axial direction and has a dynamic range of 2 cm. The results show that cost-effective 3D printing methods are suitable for realizing a handheld confocal microscope with an axial movement feature. Using cheap and replaceable 3D printed parts can ease the cleaning and disinfection procedures in clinical practices.

Alongside spatial information, an intensity scalar is also measured by LiDAR (Light Detection And Ranging) sensor systems. It corresponds to the amplitude of the backscattered laser beam after reflection on the scanned surface. This information isn’t directly usable due to dependencies of geometrical parameters occurring during the scanning process and additional processing modifications. The research community, in a growing trend, invests efforts to convert this signal into a value which could bring qualitative and quantitative new applications. We propose in this paper, a review of the theortical background of LiDAR radiometric calibration, from physical background to state-of-art methodology. A comparison of two approaches to eliminate geometrical (range and incidence angle) and instrumental dependencies of intensity measurement is presented. Their application on several homogeneous areas of a real-world case study shows a significant reduction of intensity variation between surfaces with identical material composition. Finally, a linearization process permits to obtain an equivalent Lambertian reflectance value which, by its disciminant potential, could be specifically suitable for some algorithms like segmentation or registration.

Tree improvement programs are critical to establishing high yield seed sources while maintaining genetic diversity and developing sustainable plantation forests. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is commonly used in improvement programs due to its superior strength and stiffness properties. Progeny testing trials in British Columbia (BC), Canada aim to increase stem volume without sacrificing wood quality. As genetically improved stock in BC is entering its fourth generation, wood quality and branch attributes are becoming more important as selection criteria evolve. This study investigates the utility of Airborne Laser Scanning (ALS) to produce metrics that describe branch attributes, and test whether these attributes showed differences in trees of three different genetic gain levels (GL); Wild-Stand (WS), Mid-Gain (MG) and Top-Cross (TC), planted at two different spacings (2.9 m and 4.0 m) in a realized-gain trial. New methods were developed to utilize ALS data to estimate metrics such as branch angle, length and volume using a point clustering approach. The relative impact of GL and spacing on branch attributes were assessed. Spacing was significant for branch angle (2.9 m = 73.53°, 4.0 m = 72.46°), whereas GL (WS = 0.861 m, MG = 0.917 m, TC = 0.948 m) and spacing (2.9 m = 0.884, 4.0 m = 0.942) were significant for length. For all metrics, TC trees at 4.0 m spacing were consistently significantly different whenever GL or the interaction effect was significant. This data provide an insight into how ALS can be used to model branch attributes, whereas the ability to analyse trees by plot, individual tree and individual branch attributes further allows researchers and foresters to maximize the value of ALS data. Findings from this research can be integrated into large-scale programs not just for monitoring trees, but also for identifying new trees that can display attributes associated with larger volumes and increased value.

A laser scanner is a powerful tool for 3-D geometry measurement. The amplitude-modulated continuous-wave (CW) laser scanner, which benefits from high accuracy measurement operating in the intermediate range, is suitable for high-precision 3-D industrial inspection. However, due to the limited dynamic range, laser scanners suffer from data loss and deterioration. This poses challenges for 3-D modeling, conversion of 3-D point cloud data to 3-D solid data, and so on. We chose the operation wavelength in the 1530-nm region. The dynamic range of an amplitude-modulated CW laser scanner was enhanced by the implementation of a combination of a low-noise and high-gain optical preamplifier and p-i-n photodiodes, a pellicle beamsplitter, and automatic gain control using a polarization-independent high-speed variable optical attenuator based on electrooptic ceramics in the receiver. In these manners, receiver sensitivity of −72 dBm was achieved and receiver dynamic range of around 37 dB was realized. We expect that our results contribute to high-definition industrial inspection for Industry 4.0.

Calculation of corrections to gravity measurements is one of the most important stages that determine the whole quality of research. Wrong corrections can lead to incorrect interpretation of the obtained measurements and lead to their false interpretation. To achieve highly accurate results, it is necessary to take into account not only the height, but also the entire array of information about the relief. In this case, level of detail of relief model becomes critically important, especially in case of working with rugged terrain with large number of vertically developed rock formations (outliers, rock faults, steep slopes). Now the methods normally used are based on the use of previously created materials from cartographic archives (topographic maps at a scale of 1:100,000–1:25,000). It is also possible to use open (free) terrain models. These materials have a number of drawbacks, for example, low detail of the microrelief and steep inclined surfaces (slopes, walls, faults, incisions) that have a significant effect on the values measured by gravimeters located at a small distance from such forms. The available methods do not assume ability to work with dense terrain models. These shortcomings lead to wrong corrections during gravimetric measurements. however, using of modern remote sensing methods makes possible to obtain a high-precision terrain models easily. The best opportunities are provided by lIDAR technology. here we describe differences between using lIDAR data and other types of data (1:25,000 maps, open data models), and make comparison between corrections, calculated using different data sources.

The surface morphology of parts made by the laser powder bed fusion (L-PBF) process is governed by the flow of the melt pool. The nature of the molten metal flow depends on the material properties, process parameters, and powder-bed particles, etc., and may result in potentially significant variations along a laser scanning path. This study investigates the formation of transient and steady-state zones through a single-track l -PBF experiment using Inconel 625 powder. Single tracks with lengths of 1 mm and 2 mm were fabricated using 195 W laser power and scan speeds of 400 mm/s or 800 mm/s. The surface morphology of the track was analyzed using a white light interferometer (WLI), and an individual single track can be divided into three distinct zones based on the track width and height. The initial transient region has a wider and taller solidified track geometry, the region near the end of a scan has a tapered profile with a decreasing track width and height, while the steady-state region in the middle has a smaller variation in the width and height. A mesoscale numerical model was further developed using FLOW-3D to examine the formation of the transient and steady-state zones. At the start of a scan, strong flow occurs outward and backward, leading to the formation of a wider track with a bump. As the scan continues, the thermal gradient stabilizes, leading to a steady state, which resulted in a very small fluctuation in the width. Furthermore, the tapered end of the scan track is due to the half-lemniscate shape of the melt pool during laser scanning.

Most aluminum alloys, especially the 7xxx series, are incompatible with laser additive manufacturing due to many factors. In-situ process monitoring technology offers an excellent opportunity for process understanding and control, which improves the component quality and repeatability of AM. In this study, emission spectroscopy and plume imaging were utilized to monitor and understand the laser-directed energy deposition of Al7075 alloy. Characteristics of plasma were analyzed using spectra and plume image signals. Emission lines of Al I, Mg I, and Cr I observed in spectra signals demonstrated that primary elements in Al7075 were evaporated and excited during the AM process forming a plasma plume. The plasma plume intensity increased significantly as the laser power increasing. The periodic fluctuation of plasma was revealed using plume images, indicating that laser powers inputted into the target surface were unstable due to the laser and plasma interaction. The elemental evaporation and inconsistent laser input are the main challenges for Al7075 AM and are potentially monitored by plasma signals. Methods of signal process and feature extraction for spectra and plume images were developed. Experimental results showed that the aluminum emission spectral energy, the average baseline spectral intensity, and the plume area are practical for rough surface monitoring. Correlations between spectral features and key printing parameters were developed, demonstrating an excellent response of spectra features to the laser power and laser scanning speed. This investigation revealed the potentials and challenges of emission spectroscopy in the in-situ monitoring of laser AM, making progress towards intelligent additive manufacturing.

Laser scanning is investigated to measure the deflection of the crystal–melt interface during Czochralski-growth of silicon. A mid-infrared laser is used to take advantage of the IR-transparency of silicon. The method is tested at room temperature on the end-face of three crystal-samples prematurely separated from the melt (‘body-pops’). For these samples, the end-face closely resembles the crystal–melt interface during crystal growth. The laser beam is sent through the crystal boule and detected on the far side, depending on whether it is reflected by the end-face or not. Two scanning methods are tested, one assuming no reflection, i.e. direct transmission, and the second assuming reflection by the end-face, with triangulation used to find the end-face deflection. The transmission scan distinguished the end-face from other changes in transmission in >87% of measurement points along the samples, with the resolution determined by the step-size used (1 mm). The end-face reflection method only worked for two of the three samples, with a mean error of ≤0.3 mm and a standard deviation of ≤0.8 mm. This is sufficient to distinguish normal from abnormal end-face deflections. Challenges for in situ implementation of the methods are discussed.

Marine and coastal applications require now more than ever accurate and expansive understanding of the marine surface topography in the offshore domain, with the relationship of sea surface heights and geoid (equipotential surface of the Earth) being the key components. This study demonstrates some of the under-utilised and unexplored marine applications of airborne laser scanning (ALS) with respect to geoid heights verification and validation, as well as identification of surface waves properties. A synergistic methodology was developed that combines ALS measurements, hydrodynamic models and tide gauge records in conjunction with geoid models. Examination of the determined discrepancies with respect to the ALS-derived sea surface heights reveals concealed characteristics of the geoid and dynamic topography. A sea surface height accuracy of 1.7 cm in terms of standard deviation was achieved using a high-resolution regional geoid model. Furthermore, ALS point cloud data can be used to retrieve surface wavefield properties (waves heights, wavelengths and directions). In this study a direct method approach is presented. Such a deeper insight into the wave dynamics plays an enormous contribution in the understanding and quantification of coastal processes (erosion and sediment transport), as well as validation and calibration of wave models and relevant sensors.

The objective of the study was to analyse of measurement of moving objects by means of the Total Station (TS) method and Terrestrial Laser Scanning (TLS). The subject of the tests was the “Polinka” gondola cable car over the Odra river in Wrocław. Research covered the basic and control measurements. The results of observations of suspension ropes’ deflection of the cable car in kinematical state were compared for various degrees of loading. During the motion of the gondola, the shape of the pull and supporting rope is subject to constant shifts. TS measurements are restricted solely to registering interim positioning of the points of pull lines (measurement of static objects). Laser scanner measurements may reveal changes in the location of many points (i.e. drive lines, catenaries or carriages) within a unit of time. The tests were designed to show whether it is possible to capture the shifts in geometry of the moving object (mainly by means of the TLS methods - in the course of constant vibrating of lines and during the movement of gondolas). The analyses indicated that it is possible to capture the changes of geometry by means of the TLS method, however, upon strictly specified measurement conditions.

Amplitude-modulated continuous-wave (AMCW) laser scanner with focusing optics is expected to realize high-precision 3-D measurement, which requires accuracy of mm or less. Since such a modulation scheme employs periodical intensity modulation, the longitudinal resolution and the unambiguous range are in a tradeoff. Another problematic situation is the case that the target object is large so that the scanning range exceeds the unambiguous range. The acquired 3-D point clouds contain phase jumps at the boundary of the unambiguous range imposed by the modulation frequency. In this article, we propose multiple solutions to cope with these problems. First of all, our system utilizes dual-frequency modulation to overcome the tradeoff between the resolution and the unambiguous range. With appropriate electronics for demodulation, the hardware imposed a longitudinal resolution of 19.2 ± 38 $\mu \text{m}$ and the unambiguous range of 48 ± 614.3 $\mu \text{m}$ were realized. The unambiguous range can be shifted within 5-m range using a mechanical focusing optics. However, such an attractive laser scanner still suffers from ranging ambiguity. The noise on the laser light modulated by the lower modulation frequency results in phase deviation, which can incur ranging errors at the integer times of the half cycle of the higher modulation frequency. We have coped with such ranging ambiguity by synthesizing ranging errors with the data in the correct range. Especially, defocused 3-D point clouds contaminated by severe ranging errors were analyzed and restored. The measurement range can thus be elongated by >20 times of the depth-of-focus using such data processing without manipulating the mechanical focusing optics. Next, we developed an algorithm as a remedy to prevent phase jumps in the unambiguous range. With exploitation of the relationship between the intensity and spatial information, the phase unwrapping was performed to recover the spatial continuity. Thereafter, the unambiguous range can be elongated to be >48 cm. With all the abovementioned configuration and data processing, we have overcome the ranging ambiguity inherent in the AMCW laser scanner.

3D laser scanning has progressed over the last half of the 20th century in an effort to accurately visualize the surface of various territories and objects. Over time, 3D laser scanning has become less complex and easily accessible, and it has become a popular technology for collecting data "as is". Technological advances in data quality, software processing, and ease of use are rapidly expanding the scope of 3D laser scanning. This article will cover the AVEVA E3D software used in 3D laser scanning.

Cutting quality and efficiency have always been important indicators of glass laser cutting. Laser scanning modes have two kinds, namely, the spiral and concentric circle scanning modes. These modes can achieve high-performance hole cutting of thick solar float glass using a 532-nm nanosecond laser. The mechanism of the glass laser cutting under these two different scanning modes has been described. Several experiments are conducted to explore the effect of machining parameters on cutting efficiency and quality under these two scanning modes. Results indicate that compared with the spiral scanning mode, the minimum area of edge chipping (218340 µm2) and the minimum Ra (3.01 µm) in the concentric circle scanning mode are reduced by 9.4% and 16.4% respectively. Moreover, the best cutting efficiency scanning mode is 14.2% faster than that in the spiral scanning mode. The best parameter combination for the concentric circle scanning mode is as follows: Scanning speed: 2200 mm/s, number of inner circles: 6, and circle spacing: 0.05 mm. This parameter combination reduces the chipping area and sidewall surface roughness by 8.8% and 9.6% respectively at the same cutting efficiency compared with the best spiral processing parameters. The range of glass processing that can be achieved in the concentric circle scanning mode is wider than that in the spiral counterpart. The analyses of surface topography, white spots, microstructures, and sidewall surface element composition are also performed. The study concluded that the concentric circle scanning mode shows evident advantages in the performance of solar float glass hole cutting.

This paper reports the design, fabrication, and characterization of a forward-view optical scanner realized by two vertical 2-axis MEMS mirrors integrated on a Silicon Optical Bench (SiOB). The mirror plate sizes of the first and second MEMS mirrors are $0.6\times 0.7$ mm2 and $1.2\times 1.4$ mm2, respectively. With the second MEMS mirror larger, the optical beam will not be truncated even during large-angle dynamic scanning. This dual-mirror configuration also enables multiple scanning modes, e.g. , an enlarged 2D field of view (FoV) by combining the scans of both mirrors, and a decoupled raster scanning by actuating the two mirrors separately. Experiments show that the enlarged 2D FoV reached 28°(h) $\times 31^{\circ }$ (v) and the FoV of the decoupled raster scanning reached 38°(h) $\times 8^{\circ }$ (v). The measured first resonances of the two mirrors were 2.09 kHz and 0.85 kHz, respectively. The overall size of the MEMS scanner was only $5.3\times 5.8\times 3.0$ mm3, and its weight was 20 mg. This 2-axis forward optical scanner is much smaller and lighter than other two-mirror scanning modules, giving it a great potential for applications in miniature LiDAR for micro-robotics. [2020-0081]

The second part of this article examines the transition of midrange terrestrial laser scanning (TLS)–from applied research to applied markets. It looks at the crossover of technologies; their connection to broader developments in computing and microelectronics; and changes made based on application. The shift from initial uses in on-board guid- ance systems and terrain mapping to tripod-based survey for as-built documentation is a main focus. Origins of terms like digital twin are identified and, for the first time, the earliest examples of cultural heritage (CH) based midrange TLS scans are shown and explained. Part two of this history of laser scanning is a comprehensive analysis upto the year 2020.

Three-dimensional metric models of real physical objects are actively used when solving various tasks in the process of a person's professional activity. In the construction industry, 3D modeling helps to capture all life cycles of buildings from engineering surveys to design, operation and demolition work. Three-dimensional models allow quickly performing all the necessary measurements in a computer environment, provide the ability to build two-dimensional drawings and make changes to design documentation. Among all types of three-dimensional models, there are separately those that allow storing various attributive information about an object in addition to geometric information, significantly automate the process of many engineering calculations using a three-dimensional model and provide the ability to automatically create various types of documentation. These types of three-dimensional models are called building information models (BIM). The most appropriate method is laser scanning as a data source for creating BIM. The technique of three-dimensional modeling based on laser scanning data is discussed. The advantages of BIM over simple three-dimensional models created in specialized software for processing laser scanning data and computer-aided design systems are analyzed.

Terrestrial laser scanning (TLS) assists in the detection of the unsafe behaviour of slopes and scarps. It also facilitates the assessment of the stability of earthworks. Earth structures are those that are usually made of qualified ground material. One may distinguish between point structures such as mounds, forts and dams, and linear structures such as roads, railways and flood embankments. This article concerns the problem of monitoring and analysing of the effects associated with the unstable behaviour of selected earth structures. TLS enables remote sensing of surface changes in a simple and automated manner. Regular, multiple measurements with the laser scanner are applied in long-term monitoring of the behaviour of the selected objects. The discrete numerical models using, for example, the finite element method (FEM) take into account geotechnical properties of substrate and allow for the risk assessment and stability testing of such structures. The numerical model of the structure along with the parameters of the substrate are introduced into the FEM package. This allows for the analysis of stresses, strains and displacements, along with different loading cases. The work here presents a few selected earth structures for which the aforementioned analyses have been undertaken.

We present a chaotic lidar for underwater ranging and three-dimension (3D) imaging applications. The lidar transmitter based on a laser diode with free space optical feedback is designed to generate 520 nm wavelength wideband chaotic signal. This transmitter is used with a correlation-based lidar receiver to perform a ranging demonstration in clean water with a measured attenuation coefficient of 0.06 m−1 at 520 nm. The experimental results prove that 1.2 cm mean absolute error (MAE) and 3.4 cm range resolution can be achieved and kept in a range of 140 cm at least. Moreover, employing a two-axis mirror for laser scanning, the possibility of the designed chaotic lidar system for 3D imaging is also verified.

This article presents the origins and evolution of midrange terrestrial laser scanning (TLS), spanning primarily from the 1950s to the time of publication. Particular attention is given to developments in hardware and software that document the physical dimensions of a scene as a point cloud. These developments include parameters for accuracy, repeatability, and resolution in the midrange—millimeter and centimeter levels when recording objects at building and landscape scales up to a kilometer away. The article is split into two parts: Part one starts with early space and defense applications, and part two examines the survey applications that formed around TLS technologies in the 1990s. The origins of midrange TLS, ironically, begin in space and defense applications, which shaped the development of sensors and information processing via autonomous vehicles. Included are planetary rovers, space shuttles, robots, and land vehicles designed for relative navigation in hostile environments like space and war zones. Key people in the midrange TLS community were consulted throughout the 10-year period over which this article was written. A multilingual and multidisciplinary literature review—comprising media written or produced in Chinese, English, French, German, Japanese, Italian, and Russian—was also an integral part of this research.

Laser scanners have emerged as a powerful instrument for high-precision 3-D geometry measurement. However, such attractive laser scanners have failed to address to drop of receiving power due to laser’s interaction with the surface of the object under measurement. This is a serious weakness of laser scanning systems since it can result in data deterioration and data loss in the acquired 3-D point clouds. Numerous studies have been carried out on laser illumination on rough surfaces and have shown that interference between backscattered lights within the laser beam spot forms speckles that affect the level of the receiving power. In this article, we propose a laser scanner having a rapid and continuous polarization scrambling function and cope with the drop in the receiving power. This is the first report of speckle reduction with the depolarization approach in laser scanning used for industrial measurement.

In this paper, we propose a sensitivity-enhanced thermoreflectance microscopy (TRM) system employing an electronic auto-balancing photoreceiver for effective thermal fault localization through a Si substrate. The proposed system in the auto-balanced detection not only improves the system signal-to-noise ratio (SNR) by approximately five times compared to that achievable via normal detection but also mitigates the inherent system noise, such as pseudothermoreflectance signals, by using the optical zooming. Moreover, temperature variations as small as ~47 mK were detectable under the measurement conditions employed in this paper. Finally, we experimentally demonstrated clear localization of a thermal fault, which was dimly visible in the normal backside detection results, in an optical zoomed thermal image.

Using the implemented objects as an example, the advantages of using laser scanning at inspecting technically complex structures and strain monitoring are shown. The practice of using scanning while protecting a cultural heritage object, preparing the initial data for BIM modeling, for examining artificial structures and determining deformations of a road embankment is described. Examples of sharing software products for processing and interpreting laser scanning results are presented. The description of creating a survey justification for working on ground-based laser scanning is given. The advantages of introducing laser scanning technology into theenterprise’s activities are shown. Real examples show that the use of ground-based laser scanning enables restoring lost project documentation, determining the deformation of structural elements, monitoringthe current shape of the embankments, evaluating the volume of sedimentary rocks and solving other problems. It is noted that the use of laser scanning can significantly reduce the time required for field work, which is especially important when working at objects with a limited access mode.

We design, fabricate, and measure high-speed resonant varifocal mirrors for a reflective type focus scanning optical element. A circumference supported type mirror and a node supported type mirror with a 1 mm diameter driven by an electrostatic actuator are investigated. In the node supported type, a larger amplitude compared to that of the circumference supported type was obtained. The fabricated mirror could operate at approximately 450 kHz with axisymmetric deformation. The focal length was calculated to be ±28 mm at an applied total voltage amplitude of 150 V.

This research proposes a novel method of recording the features of mine mills digitally by 3D laser scanner and its application. This method enables to obtain their shape features in short time independent of the expert's drawing skill. It also enables to evaluate the shape feature values, such as the position of the center of gravity, based on the obtained 3D digital data. In addition it may be possible to get a clue to clarify the process of varying the shape of mine mills. The mine mills described in this paper are remains discovered in the mountains of Yu-no-oku gold mine locating in Minami Kuma County in Yamanashi prefecture, Japan.

The intensity data recorded by a terrestrial laser scanner (TLS) are significantly influenced by the distance between the scanned point and the scanner center. In this letter, we propose a new method to estimate the TLS distance–intensity relationship by using naturally homogeneous targets (NHT). Since the original intensity data of the NHT are simultaneously influenced by the incidence angle and distance, the incidence angle effect is first eliminated to obtain a corrected intensity that merely depends on distance. Then, the distance–intensity relationship is derived by analyzing the incidence angle corrected intensity data of the NHT. Results indicate that compared with existing methods the proposed method is accurate and easily implementable. The coefficient of variation for the intensity data can be reduced by 52% after correction by the proposed method.