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Journal articles on the topic 'Optical distance measurement'

Author: Grafiati

Published: 28 June 2021

Last updated: 4 February 2022

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1

Kienle, Patrick, Lorena Batarilo, Markus Akgül, Michael H. Köhler, Kun Wang, Martin Jakobi, and Alexander W. Koch. "Optical Setup for Error Compensation in a Laser Triangulation System." Sensors 20, no. 17 (September 1, 2020): 4949. http://dx.doi.org/10.3390/s20174949.

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Absolute distance measurement is a field of research with a large variety of applications. Laser triangulation is a well-tested and developed technique using geometric relations to calculate the absolute distance to an object. The advantages of laser triangulation include its simple and cost-effective setup with yet a high achievable accuracy and resolution in short distances. A main problem of the technology is that even small changes of the optomechanical setup, e.g., due to thermal expansion, lead to significant measurement errors. Therefore, in this work, we introduce an optical setup containing only a beam splitter and a mirror, which splits the laser into a measurement beam and a reference beam. The reference beam can then be used to compensate for different error sources, such as laser beam dithering or shifts of the measurement setup due to the thermal expansion of the components. The effectiveness of this setup is proven by extensive simulations and measurements. The compensation setup improves the deviation in static measurements by up to 75%, whereas the measurement uncertainty at a distance of 1 m can be reduced to 85 μm. Consequently, this compensation setup can improve the accuracy of classical laser triangulation devices and make them more robust against changes in environmental conditions.

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2

Pillarz, Marc, Axel von Freyberg, Dirk Stöbener, and Andreas Fischer. "Gear Shape Measurement Potential of Laser Triangulation and Confocal-Chromatic Distance Sensors." Sensors 21, no. 3 (January 30, 2021): 937. http://dx.doi.org/10.3390/s21030937.

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The demand for extensive gear shape measurements with single-digit µm uncertainty is growing. Tactile standard gear tests are precise but limited in speed. Recently, faster optical gear shape measurement systems have been examined. Optical gear shape measurements are challenging due to potential deviation sources such as the tilt angles between the surface normal and the sensor axis, the varying surface curvature, and the surface properties. Currently, the full potential of optical gear shape measurement systems is not known. Therefore, laser triangulation and confocal-chromatic gear shape measurements using a lateral scanning position measurement approach are studied. As a result of tooth flank standard measurements, random effects due to surface properties are identified to primarily dominate the achievable gear shape measurement uncertainty. The standard measurement uncertainty with the studied triangulation sensor amounts to >10 µm, which does not meet the requirements. The standard measurement uncertainty with the confocal-chromatic sensor is <6.5 µm. Furthermore, measurements on a spur gear show that multiple reflections do not influence the measurement uncertainty when measuring with the lateral scanning position measurement approach. Although commercial optical sensors are not designed for optical gear shape measurements, standard uncertainties of <10 µm are achievable for example with the applied confocal-chromatic sensor, which indicates the further potential for optical gear shape measurements.

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Wang, Wei Chen, Ding Chen, Hong Tang Gao, and Zi Ben Yang. "Study on Dynamic Measurement of Plane Distance." Key Engineering Materials 625 (August 2014): 91–97. http://dx.doi.org/10.4028/www.scientific.net/kem.625.91.

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Step gauge is the most typical multiple target standard of plane distance with a wide range of applications. The calibration of step gauge is, however, difficult because of its unique structure. In this paper, a new method for measuring plane distance is presented. The principle of light-section microscope is used in accurate positioning of the planes being measured. Then the optical interferometry techniques are used to realize continuous dynamic measurement of the plane distance. Based on this method, a novel optical probe is built and installed on a laser interferometer for length measurements. A series of experiments were carried out for determining the accuracy of positioning the optical probe and repeatability of the measuring system. Experimental results show that measurement repeatability is better than 16 nm, and measurement uncertainty (k=2) is less than 0.03 μm + 1.0×10-6L, for a total length of L being measured in micrometers.

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4

Neitsch, Marie, Iris-Susanne Horn, Mathias Hofer, Andreas Dietz, and Miloš Fischer. "Integrated Multipoint-Laser Endoscopic Airway Measurements by Transoral Approach." BioMed Research International 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/6838697.

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Objectives. Optical and technical characteristics usually do not allow objective endoscopic distance measurements. So far no standardized method for endoscopic distance measurement is available. The aim of this study was to evaluate the feasibility and accuracy of transoral airway measurements with a multipoint-laser endoscope.Methods.The semirigid endoscope includes a multipoint laser measurement system that projects 49 laser points (wavelength 639 nm, power < 5 mW) into the optical axis of the endoscopic view. Distances, areas, and depths can be measured in real-time. Transoral endoscopic airway measurements were performed on nine human cadavers, which were correlated with CT measurements.Results.The preliminary experiment showed an optimum distance between the endoscope tip and the object of 5 to 6 cm. There was a mean measurement error of 3.26% ± 2.53%. A Spearman correlation coefficient of 0.95 (p=0.01) was calculated for the laryngeal measurements and of 0.93 (p<0.01) for the tracheal measurements compared to the CT. Using the Bland-Altman-Plot, the 95% limits of agreement for the laryngeal measurements were satisfactory: −0.76 and 0.93.Conclusions.Integrated multipoint-laser endoscopic measurement is a promising technical supplement, with potential use in diagnostic endoscopy and transoral endoscopic surgery in daily practice.

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5

Gouaux, Flore, Noël Servagent, and Thierry Bosch. "Absolute distance measurement with an optical feedback interferometer." Applied Optics 37, no. 28 (October 1, 1998): 6684. http://dx.doi.org/10.1364/ao.37.006684.

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6

Xu, Xinyang, Ziqiang Zhang, Haoyun Zhang, Haihan Zhao, Wenze Xia, Mingzhao He, Jianshuang Li, Jingsheng Zhai, and Hanzhong Wu. "Long distance measurement by dynamic optical frequency comb." Optics Express 28, no. 4 (February 3, 2020): 4398. http://dx.doi.org/10.1364/oe.381504.

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7

Majumdar, Ayan, and Haiying Huang. "Compact optical fiber whitelight interferometric distance sensor for arbitrary small distance measurement." Applied Optics 48, no. 19 (June 22, 2009): 3702. http://dx.doi.org/10.1364/ao.48.003702.

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8

WANG Zhi-bin, 王志斌, 史国华 SHI Guo-hua, 何益 HE Yi, 丁志华 DING Zhi-hua, and 张雨东 ZHANG Yu-dong. "Application of optical coherence tomography to distance measurement of optical surface." Optics and Precision Engineering 20, no. 7 (2012): 1469–74. http://dx.doi.org/10.3788/ope.20122007.1469.

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9

Junttila, Petri, Kalervo Nevala, and Petter Kroneld. "Enhancing the Accuracy of MRI-Compatible Robots with an Optical Tracking System." Solid State Phenomena 144 (September 2008): 191–95. http://dx.doi.org/10.4028/www.scientific.net/ssp.144.191.

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Magnetic resonance imaging (MRI) is currently a widely used technology for obtaining a three-dimensional image of a patient’s internal structures. This study examines the measurement properties of an optical tracking system utilised in the MRI room. The results were used to assess the suitability of the device to be used as a part of the control system of a surgical robot. The position and orientation of the instrument, MRI scanner and the patient are measured using an optical tracking system in the MRI room. The measurement data can be used to display the instrument used as a part of the image of the patient. The optical tracking system used in the MRI room can also be considered as a part of the control system of a robot located in the room. When considering such use, the operations of the measuring device in different measurement conditions must be known. In terms of robot control, it is important to know the deviation attributed to measurement when defining the translation vector and orientation between two trackers. Five measurement series were carried out using the measurement device to examine the deviation in the translation vector and orientation data between two trackers. The distance and position between the trackers were changed between the measurement series. During the measurement series, the measurement device was moved to different distances from the trackers and the translation vector and orientation between the trackers were defined on the basis of the measurement results obtained. The measurements showed that the deviation of the translation vector did not significantly change as the measurement distance increased, but the deviation of orientation data between different trackers increased significantly. Deviation in the translation vector increased as the distance between trackers increased, but deviation in orientation did not change significantly.

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10

Li Zhidong, 李志栋, 江月松 Jiang Yuesong, 桑峰 Sang Feng, 王林春 Wang Linchun, 邓士光 Deng Shiguang, 辛遥 Xin Yao, and 郭泾平 Guo Jingping. "Interferometry for Absolute Distance Measurement." Acta Optica Sinica 31, no. 3 (2011): 0314001. http://dx.doi.org/10.3788/aos201131.0314001.

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11

Daliga, Karol, and Zygmunt Kurałowicz. "EXAMINATION METHOD OF THE EFFECT OF THE INCIDENCE ANGLE OF LASER BEAM ON DISTANCE MEASUREMENT ACCURACY TO SURFACES WITH DIFFERENT COLOUR AND ROUGHNESS." Boletim de Ciências Geodésicas 22, no. 3 (September 2016): 420–36. http://dx.doi.org/10.1590/s1982-21702016000300024.

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Interest in the influence of the incidence angle of a laser beam to distance measurements can be seen in many areas of science and technology: geodesy, glaciology, archaeology, machine automation, and others. This paper presents results of measurements of the effect of the incidence angle of a laser beam to distance measurements to the surfaces of different colour and roughness by Topcon's electro-optical total station with an accuracy of 3 mm. Measurement method and the method of elimination of test stand errors are presented. The results of measurements have been analysed and the influence of selected factors (surface colour and roughness, lack of instrument rectification) on the distance measurement have been discussed. It is also shown the critical incidence angle above which it can be impossible to measure distances to reflective foil with tested total station

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12

Zhao Lijie, 赵力杰, 周艳宗 Zhou Yanzong, 夏海云 Xia Haiyun, 武腾飞 Wu Tengfei, and 韩继博 Han Jibo. "Overview of distance measurement with femtosecond optical frequency comb." Infrared and Laser Engineering 47, no. 10 (2018): 1006008. http://dx.doi.org/10.3788/irla201847.1006008.

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13

Hariyama, Tatsuo, Hiroaki Kasai, and Masahiro Watanabe. "Development of Distance Measurement Technique Using Optical Comb Laser." Journal of the Japan Society for Precision Engineering 86, no. 5 (May 5, 2020): 347–52. http://dx.doi.org/10.2493/jjspe.86.347.

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14

Seta, Katuo, Tadanao Ohishi, and Shoichi Seino. "Optical Distance Measurement Using Inter-Mode Beat of Laser." Japanese Journal of Applied Physics 24, Part 1, No. 10 (October 20, 1985): 1374–75. http://dx.doi.org/10.1143/jjap.24.1374.

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15

Wu, Hanzhong, Fumin Zhang, Tingyang Liu, Fei Meng, Jianshuang Li, and Xinghua Qu. "Absolute Distance Measurement Using Optical Sampling by Cavity Tuning." IEEE Photonics Technology Letters 28, no. 12 (June 15, 2016): 1275–78. http://dx.doi.org/10.1109/lpt.2016.2538266.

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16

Wu, Hanzhong, Fumin Zhang, Tingyang Liu, Petr Balling, Jianshuang Li, and Xinghua Qu. "Long distance measurement using optical sampling by cavity tuning." Optics Letters 41, no. 10 (May 12, 2016): 2366. http://dx.doi.org/10.1364/ol.41.002366.

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17

Shimizu, Yuki, Hiraku Matsukuma, and Wei Gao. "Optical Angle Sensor Technology Based on the Optical Frequency Comb Laser." Applied Sciences 10, no. 11 (June 11, 2020): 4047. http://dx.doi.org/10.3390/app10114047.

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A mode-locked femtosecond laser, which is often referred to as the optical frequency comb, has increasing applications in various industrial fields, including production engineering, in the last two decades. Many efforts have been made so far to apply the mode-locked femtosecond laser to the absolute distance measurement. In recent years, a mode-locked femtosecond laser has increasing application in angle measurement, where the unique characteristics of the mode-locked femtosecond laser such as the stable optical frequencies, equally-spaced modes in frequency domain, and the ultra-short pulse trains with a high peak power are utilized to achieve precision and stable angle measurement. In this review article, some of the optical angle sensor techniques based on the mode-locked femtosecond laser are introduced. First, the angle scale comb, which can be generated by combining the dispersive characteristic of a scale grating and the discretized modes in a mode-locked femtosecond laser, is introduced. Some of the mode-locked femtosecond laser autocollimators, which have been realized by combining the concept of the angle scale comb with the laser autocollimation, are also explained. Angle measurement techniques based on the absolute distance measurements, lateral chromatic aberration, and second harmonic generation (SHG) are also introduced.

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18

Pillarz, Marc, Axel von Freyberg, and Andreas Fischer. "Determination of the mean base circle radius of gears by optical multi-distance measurements." Journal of Sensors and Sensor Systems 9, no. 2 (August 20, 2020): 273–82. http://dx.doi.org/10.5194/jsss-9-273-2020.

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Abstract. The required reliability of wind turbine gearboxes increases the requirements for large gear measurements. Extensive measurements to reliably assess the geometry of large gears in the single micrometer range are necessary. Due to an individually fixed measuring volume, standard methods like coordinate and gear measuring instruments reach their limits for large gears with diameters > 1 m. Therefore, a scalable optical measurement approach consisting of a single sensor in combination with a rotary table for multi-distance measurements with subsequent model-based evaluation of shape parameters of gears is presented. The scalable measurement approach is to be extended to a multisensory system in further work. As a fundamental shape parameter the mean base circle radius using the example of spur gears is determined. The base circle radius is used due to the geometric relationship to further shape parameters for example to the profile slope deviation. The theoretically achievable measurement uncertainty of the mean base circle radius due to sensor noise is estimated to less than 5 µm (k=2) for a small and a large gear, which verifies the scalability of the sensor system. In order to show a general proof of principle, two series of optical measurements on a gear with a diameter of 0.105 m are performed and referenced with a tactile measurement. As a result, random errors of 1.2 µm for k=2 are determined. The remaining systematic deviations to the reference value amount to 4.3 and 1.6 µm, respectively. Hence, the total measurement uncertainty is currently limited by systematic effects, and the defined aim of a total uncertainty of less than 5 µm (k=2) is narrowly missed by 1.5 µm. The random errors of 1.2 µm (k=2) show, however, that an adequate measurement precision is achieved and that the multi-distance measurement approach has the potential to reach the aimed measurement uncertainty with appropriate strategies to compensate for the systematic influences. The experimental and theoretical results prove the principle applicability of the proposed single sensor multi-distance approach for the precise inspection of gears.

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19

Li, Wenliang, Xinghua Qu, Xianyu Zhao, and Fumin Zhang. "Absolute distance measurement of rough surfaces using asynchronous optical sampling." Optical Engineering 58, no. 09 (September 5, 2019): 1. http://dx.doi.org/10.1117/1.oe.58.9.094101.

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20

Zhang, Hongyuan, Haoyun Wei, Xuejian Wu, Honglei Yang, and Yan Li. "Absolute distance measurement by dual-comb nonlinear asynchronous optical sampling." Optics Express 22, no. 6 (March 13, 2014): 6597. http://dx.doi.org/10.1364/oe.22.006597.

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21

Fonseca, Joao Antonio Santos Dias, Antonio Baptista, Ma Joao Martins, and Joao Paulo N. Torres. "Distance Measurement Systems Using Lasers and Their Applications." Applied Physics Research 9, no. 4 (July 24, 2017): 33. http://dx.doi.org/10.5539/apr.v9n4p33.

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Optical measuring systems came to offer new ways to determine distances, deformations or vibrations through more accurate and greater range methods. Technological progress has allowed a significant improvement of several components, including the optical ones. Thus, the development of essential measurement methods is crucial to keep up with technological advances.In this paper, the three basic methods of measurement are studied – triangulation, telemetry and interferometry, covering their main applications, advantages and disadvantages, and theoretically substantiating each of the methods. The results of simulation routines for each method are shown along this work. For the triangulation method we made two experiments which demonstrate the functioning of the method in measuring distances and surfaces.For the telemetry method, experimental setups were studied to apply the method of pulse telemetry and phase comparison telemetry to measure distances,Thus, it is intended to set up the basis for the future development of more complex methods.

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22

Babković, Kalman, László F. Nagy, and Damir Krklješ. "Self-Calibrating Optical Displacement Sensor." Key Engineering Materials 543 (March 2013): 59–62. http://dx.doi.org/10.4028/www.scientific.net/kem.543.59.

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Commercially available reflective optical sensors can be used as displacement sensors which in turn can be used in vibration monitoring, positioning, force-measurement and other applications. The sensor output depends in all cases on the distance between the component and a suitable reflective surface. In this paper a sensor system applicable to vibration measurement (e.g. monitoring a vibration-generating machine mounted on elastic isolation mountings) is presented where a special mechanism enables the controlled adjustment of the reflective surfaces position. This feature allows continuous operating point adjustment while the sensor measures vibration. On the other hand, during the intervals when the vibration measurement is not active (e.g. the machine is not in use), the system can be used to automatically calibrate the sensor, i.e. to measure the dependence of the optical sensor output from the distance to the reflective surface. This allows accurate measurements under various circumstances: temperature change, optical component replacement, staining of the reflective surface, ingress of dirt etc. The reflective surface adjustment system is controlled by an embedded digital system which also controls the calibration procedure. Range depends largely on the type of reflective sensor. In case of the component TCRT1000 used in the experiments, range is up to 4 mm.

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23

Karam, Frederick Khalil, Karla Zancope, Thiago de Almeida Prado Naves Carneiro, Murilo Navarro de Oliviera, Caio César Dias Resende, and Flávio Domingues das Neves. "Comparative analysis of Optical Microscopy, Scanning Electron Microscopy, and Micro-Computed Tomography on measurements." Brazilian Journal of Oral Sciences 16 (December 15, 2017): 1–9. http://dx.doi.org/10.20396/bjos.v16i0.8651056.

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Microscopic measurements are widely used in scientific research and the correct equipment to realize these evaluations could be critical to determine study results. Regarding microscopic measurements, three of the most used methods are: Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Micro-computed Tomography (MCT). It is important to select the best method for assessing diverse parameters, considering operational characteristics of the method, the equipment efficiency, and the machinery cost. Therefore, the main objective of this study was to define which is the most useful measurement method for assessing magnitudes below 0.4 mm. Ten dental implants, with known dimensions as defined by the manufacturer were randomly distributed. Two blinded observers assessed the distance between the second and the third screw vortex of the implants using three suggested methods. The true distance was defined to be 0.5 mm. The assessed distances were: 0.597±0.007mm for OM, 0.578±0.017mm for SEM, and 0.613±0.006mm for MCT. The assessed distances were significantly different when the methods were compared (P>0.01). All measurements were into the CAD tolerances. It was possible to conclude that linear measurements between 595 and 605 μm could be performed by any of the described technologies.

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24

Onoe, Taro, Satoru Takahashi, Kiyoshi Takamasu, and Hirokazu Matsumoto. "Development of a Non-Contact Precision Measurement Technique Using Optical Frequency Combs." Key Engineering Materials 523-524 (November 2012): 877–82. http://dx.doi.org/10.4028/www.scientific.net/kem.523-524.877.

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We develop a new method for high-resolution and contactless distance measurement based on self frequency beats of optical frequency combs. We use two optical frequency comb lasers with Rb-stabilized repetition frequencies for doing accurate distance measurement. The repetition frequencies of the optical frequency combs are different, thus parts of the high frequencies such as several gigahertz of self beats are beat-downed to several megahertz without an RF frequency oscillator. The phases of the beat signals of several megahertz frequencies are measured by a lock-in amplifier with a high resolution and high sensitivity. The new method is applied to distance measurement for objects which have rough-surface in the distance range of several-meters.

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25

Bartel, Norbert. "Determinations of Distances to Radio Sources with VLBI." Symposium - International Astronomical Union 129 (1988): 175–84. http://dx.doi.org/10.1017/s0074180900134424.

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The most direct method of determining distances to galactic sources outside the Solar System is the measurement of annual parallaxes. Using as an example astrometric observations of the quasars 3C345 and NRAO512 which are separated by ∼ 0°.5 at the sky, we show that under certain conditions, annual parallaxes of galactic radio sources can be determined with VLBI with an accuracy of 50 μas (standard error). This accuracy is about tenfold higher than any annual parallax accuracy ever obtained with optical astrometry.The, so far, most direct method of determining distances to extragalactic sources combines VLBI measurements of a supernova's angular expansion velocity with optical spectroscopic measurements of the supernova's radial expansion velocity. We have estimated the distance to SN1979C in M100 in the Virgo cluster to be a lower bound on the distance to SN1980K in NGC6946 to be 5 Mpc, and H0 to be with the uncertainties intended to represent standard errors.

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26

Wilson, B. "Laboratory Measurement of Optical Fibre Communication Parameters." International Journal of Electrical Engineering & Education 23, no. 3 (July 1986): 211–21. http://dx.doi.org/10.1177/002072098602300304.

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A teaching laboratory experiment to measure the main engineering parameters of an optical fibre is described. Using relatively inexpensive equipment, the fibre length, attenuation per unit length and bandwidth-distance product of a PCS fibre are calculated. The approach is easily adaptable for use by 2nd year or final year undergraduates and M.Sc. course students, depending upon the detail and complexity presented in the experimental script.

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27

Duong, Chen, and Chen. "Absolute Depth Measurement Using Multiphase Normalized Cross-Correlation for Precise Optical Profilometry." Sensors 19, no. 21 (October 28, 2019): 4683. http://dx.doi.org/10.3390/s19214683.

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In a multifrequency phase-shifting (MFPS) algorithm, the temporal phase unwrapping algorithm can extend the unambiguous phase range by transforming the measurement range from a short fringe pitch into an extended synthetic pitch of two different frequencies. However, this undesirably amplifies the uncertainty of measurement, with each single-frequency phase map retaining its measurement uncertainty, which is carried over to the final unwrapped phase maps in fringe-order calculations. This article analyzes possible causes and proposes a new absolute depth measurement algorithm to minimize the propagation of measurement uncertainty. Developed from normalized cross-correlation (NCC), the proposed algorithm can minimize wrong fringe-order calculations in the MFPS algorithm. The experimental results demonstrated that the proposed measurement method could effectively calibrate the wrong fringe order. Moreover, some extremely low signal-to-noise ratio (SNR) regions of a captured image could be correctly reconstructed (for surface profiles). The present findings confirmed measurement precision at one standard deviation below 5.4 µm, with an absolute distance measurement of 16 mm. The measurement accuracy of the absolute depth could be significantly improved from an unacceptable level of measured errors down to 0.5% of the overall measuring range. Additionally, the proposed algorithm was capable of extracting the absolute phase map in other optical measurement applications, such as distance measurements using interferometry.

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Zhang, Haoyun, Xinyang Xu, Haihan Zhao, Fanpeng Dong, Zhiwen Qian, and Bin Xue. "Water Temperature and Salinity Measurement Using Frequency Comb." Applied Sciences 9, no. 23 (November 22, 2019): 5043. http://dx.doi.org/10.3390/app9235043.

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Water temperature and salinity are key parameters in many fields such as industry, forestry and agriculture. In this paper, we, theoretically and experimentally, demonstrate a method which is capable of water temperature and salinity measurement based on a laser frequency comb at 518 nm. We have developed a simple Michelson interferometer system. By scanning a mirror on a precision displacement platform, a pair of cross-correlation patterns can be obtained. The real-time optical distance information from these cross-correlation patterns can be used to calculate the optical distance difference changes. Temperature and salinity can be measured via these changes, aided by the empirical formulas. Compared with the reference values, our results show the differences of below 0.12 °C for temperature measurements, and 0.06 ‰ for salinity measurements. The obtained results indicate that our method can offer a powerful scheme for future temperature and salinity measurement.

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Idesawa, Masanori. "Acquisition of 3-D Optical Information." Journal of Robotics and Mechatronics 1, no. 4 (December 20, 1989): 255. http://dx.doi.org/10.20965/jrm.1989.p0255.

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In order for a machine to have the capacity to operate flexibly in a 3-D environment, it is indispensable for it to be equipped with space information acquisition capability, and tools for distance measurement are in turn indispensable for obtaining space information. Indeed distance measurement is basic and important not only for a robot, but also for science and technology in general. Many methods have been proposed for obtaining distance information, ranging from the mechanical contact type through optical and acoustic to electric and magnetic methods, and many are in practical use. Among them the optical method permits measurement of distance without contact and from a remote position, advantages which have led to it being widely applied. One of the most important principles for measuring distance is the triangulation principle. This permits determination of the position of an object from the distance between two observation points together with the angles in the triangle formed by these two points and a target point on the object. Based on this principle, the detection of one specific point in each of the two images obtained from two sets of image input equipment installed at two observation points permits determination of coordinate values in 3-D space. However, this extraction of the point in the second image corresponding to a specified point in the first image is a very difficult subject of study, and no universal method has been developed. To cope with this, active methods, which evade the problem by applying projection of laser light on the surface of an object to identify a bright point or bright line, are widely used. The special feature articles on obtaining 3-D optical information in this issue present some principles and new trial applications of distance acquisition methods for 3-D information, the optical method in particular. There are three reports on active method optical systems developed for robots. These include (1) a high speed measurement method applying space encoding which employs a liquid crystal lattice to project light in changing lattice patterns onto an object dynamically; (2) realization of high speed measurement through projecting and processing multiple light spots; (3) development of a visual sensor for disaster prevention use which can detect objects in flames and smoke utilizing projection of a CO2 gas laser. These are nearly at the level of operational use and are expected to become visual sensors for robots.

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30

Zhang, Chengyang, Xishuang Jing, Siyu Chen, Xuanzhe Ling, Jiarong Zou, and Gang Zhao. "Method of improving large-scale measurement accuracy of laser tracker based on photogrammetry." Measurement and Control 52, no. 9-10 (April 15, 2019): 1220–27. http://dx.doi.org/10.1177/0020294018813644.

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Background: When performing the spatial large-scale measurements, the measurement accuracy of laser tracker would decreased with the increase of the measurement distances due to the refraction difference of most optical digital measurement devices. Therefore, this paper proposed a method based on photogrammetry system to improve the large-scale measurement accuracy of the laser tracker. Purpose: The purpose of this method is to improve the large-scale measurement accuracy of the laser tracker by considering the advantages of photogrammetry system such as high measurement accuracy and good portability. Methods: The measurement data from the photogrammetry system would be used as a reference to do correction on measurement results from laser tracker. The coordinate correction method based on Rodrigues’ rotation formula has been discussed. The measurement accuracy of the long-distance point of laser tracker can be significantly improved through the coordinate correction method. Conclusion: Based on the advantages of using photogrammetry system, the proposed method can achieve higher accuracy when measuring the common points at a closer distance than the laser tracker can do when measuring objects far away from instrument. The feasibility of the proposed method has been demonstrated by experiment.

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31

Yasui, Takeshi, Yasuhiro Kabetani, Yoshiyuki Ohgi, Shuko Yokoyama, and Tsutomu Araki. "Absolute distance measurement of optically rough objects using asynchronous-optical-sampling terahertz impulse ranging." Applied Optics 49, no. 28 (September 22, 2010): 5262. http://dx.doi.org/10.1364/ao.49.005262.

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32

Rüeger, J. M. "REFRACTIVE INDEX OF WATER AND ELECTRO-OPTICAL DISTANCE MEASUREMENT THROUGH RAIN." Survey Review 35, no. 271 (January 1999): 11–22. http://dx.doi.org/10.1179/sre.1999.35.271.11.

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33

Xue, Bin, Zhiyang Wang, Kai Zhang, Jianshuang Li, and Hanzhong Wu. "Absolute distance measurement using optical sampling by sweeping the repetition frequency." Optics and Lasers in Engineering 109 (October 2018): 1–6. http://dx.doi.org/10.1016/j.optlaseng.2018.05.002.

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Cui, Pengfei, Linghui Yang, Yin Guo, Jiarui Lin, Yang Liu, and Jigui Zhu. "Absolute Distance Measurement Using an Optical Comb and an Optoelectronic Oscillator." IEEE Photonics Technology Letters 30, no. 8 (April 15, 2018): 744–47. http://dx.doi.org/10.1109/lpt.2018.2814680.

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Cui Pengfei, 崔鹏飞, 杨凌辉 Yang Linghui, 林嘉睿 Lin Jiarui, and 邾继贵 Zhu Jigui. "Application of Femtosecond Optical Frequency Comb in Precise Absolute Distance Measurement." Laser & Optoelectronics Progress 55, no. 12 (2018): 120011. http://dx.doi.org/10.3788/lop55.120011.

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Zhang, Tianyu, Xinghua Qu, Fumin Zhang, and Bo Peng. "Long Distance Measurement System by Optical Sampling Using a Femtosecond Laser." IEEE Photonics Journal 10, no. 5 (October 2018): 1–10. http://dx.doi.org/10.1109/jphot.2018.2869839.

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Lages Martins, Luís, José Manuel Nunes Vicente Rebordão, and Álvaro Silva Ribeiro. "Thermal Influence on Long-Distance Optical Measurement of Suspension Bridge Displacement." International Journal of Thermophysics 35, no. 3-4 (April 2014): 693–711. http://dx.doi.org/10.1007/s10765-014-1607-3.

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Hei, Kefei, Kaszubowska Anandarajah, Eamonn P. Martin, Guang Shi, Prince M. Anandarajah, and Nandini Bhattacharya. "Absolute distance measurement with a gain-switched dual optical frequency comb." Optics Express 29, no. 6 (March 2, 2021): 8108. http://dx.doi.org/10.1364/oe.413478.

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Bräuer-Burchardt, Christian, Christoph Munkelt, Ingo Gebhart, Matthias Heinze, Stefan Heist, Peter Kühmstedt, and Gunther Notni. "A-Priori Calibration of a Structured Light Underwater 3D Sensor." Journal of Marine Science and Engineering 8, no. 9 (August 20, 2020): 635. http://dx.doi.org/10.3390/jmse8090635.

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In this study, we introduce a new calibration method for underwater optical stereo scanners. It uses air calibration, additional underwater parameters, and extended camera modeling. The new methodology can be applied to both passive photogrammetric and structured light three-dimensional (3D) scanning systems. The novel camera model uses a variable principal distance depending on the radial distance to the principal point instead of two-dimensional distortion functions. This allows for an initial improvement of 3D reconstruction quality. In a second step, certain underwater-specific parameters—such as refraction indices, glass thickness, and view-port distances—are determined. Finally, a correction function for the entire measurement volume can be obtained from a few underwater measurements. Its application further improves the measurement accuracy. Measurement examples show the performance of the new calibration method in comparison to current underwater calibration strategies. A discussion of the possibilities and limits of the new calibration method and an outlook for future work complete this work.

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Kovalev, S. V., and D. A. Shapovalov. "Kovalev passive rangefinder." Geodesy and Cartography 969, no. 3 (April 20, 2021): 12–18. http://dx.doi.org/10.22389/0016-7126-2021-969-3-12-18.

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The authors present the results of longtime research on the development and improvement of a passive geodetic rangefinder based on the inbasis method of distance measurement. Actually, active laser range finders are not always effective at field works. An original compact optical scheme of a passive rangefinder based on a theodolite telescope and a mould photo receiver with application of digital methods for coordinate calculation is proposed. The distance and dimensions of the object are defined. The former is identified by the shift between the images on the horizontal axis. The merit of such a system is the absence of mechanical displacements. Its main advantage is an extremely simple optical path. The technical result is reduction in overall dimensions and weight, while maintaining an acceptable error in the passive range measurement. The use of Kovalev passive rangefinder is promising at performing geodetic measurements with total stations. There is also a description of the rangefinder sample as well as the calculations results according to the distance measurement accuracy.

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Szabo, Roland, and Aurel Gontean. "Sun Tracker Robotic Arm Optical Distance Measurement Evaluation at Different Positions Using Six Sigma Tools." Infocommunications journal, no. 1 (2019): 54–60. http://dx.doi.org/10.36244/icj.2019.1.7.

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This paper presents an optical distance evaluation solution, for a sun tracker robotic arm, with the help of Six Sigma. With the help of statistical tools any measurement system can be evaluated and a measurement system analysis (MSA) can be easily made. Like every measurement system, optical distance measurement can have errors. Six Sigma tools can evaluate the measurement system and can give useful data about its accuracy. Sometimes measurement system evaluation is done twice. First, initial tests are done, after some fine tuning and error correction is performed, and finally a repeated test is done, to show that the measurement errors were corrected.

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Sy, Luke Wicent F., Nigel H. Lovell, and Stephen J. Redmond. "Estimating Lower Limb Kinematics Using a Lie Group Constrained Extended Kalman Filter with a Reduced Wearable IMU Count and Distance Measurements." Sensors 20, no. 23 (November 29, 2020): 6829. http://dx.doi.org/10.3390/s20236829.

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Tracking the kinematics of human movement usually requires the use of equipment that constrains the user within a room (e.g., optical motion capture systems), or requires the use of a conspicuous body-worn measurement system (e.g., inertial measurement units (IMUs) attached to each body segment). This paper presents a novel Lie group constrained extended Kalman filter to estimate lower limb kinematics using IMU and inter-IMU distance measurements in a reduced sensor count configuration. The algorithm iterates through the prediction (kinematic equations), measurement (pelvis height assumption/inter-IMU distance measurements, zero velocity update for feet/ankles, flat-floor assumption for feet/ankles, and covariance limiter), and constraint update (formulation of hinged knee joints and ball-and-socket hip joints). The knee and hip joint angle root-mean-square errors in the sagittal plane for straight walking were 7.6±2.6∘ and 6.6±2.7∘, respectively, while the correlation coefficients were 0.95±0.03 and 0.87±0.16, respectively. Furthermore, experiments using simulated inter-IMU distance measurements show that performance improved substantially for dynamic movements, even at large noise levels (σ=0.2 m). However, further validation is recommended with actual distance measurement sensors, such as ultra-wideband ranging sensors.

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Iwamoto, Taro, Koji Ohara, and Koji Shibuya. "Fast Distance Measurement Method by Parallel-Shift Arrangement Stereoscopic Camera." Journal of Robotics and Mechatronics 15, no. 3 (June 20, 2003): 314–21. http://dx.doi.org/10.20965/jrm.2003.p0314.

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Computation time of stereo matching process for distance measurement has been greatly reduced by parallel-shift optical arrangement stereoscopic camera from that of cross arrangement camera. This stereoscopic camera consists of two camera units which are combined in parallel. Image planes (CCD) of these camera units are motor-driven to shift then from its central position in order to change the location of camera axis crossing point. This optical arrangement eliminates keystone distortion and horopter becomes a vertical flat plane at the crossing point and epipolar lines of right and left images become fully corresponding horizontal lines. Therefore, matching process can be achieved only on one sweep line. This feature simplifies the matching algorithm and matching process can be faster than a conventional 2 dimensional correlation method. Computational cost for this stereo matching process is estimated more than 88% reduction to cross arrangement method.

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Hatakeyama, Naoya, Tohru Sasaki, Kenji Terabayashi, Masahiro Funato, and Mitsuru Jindai. "Position and Posture Measurement Method of the Omnidirectional Camera Using Identification Markers." Journal of Robotics and Mechatronics 30, no. 3 (June 20, 2018): 354–62. http://dx.doi.org/10.20965/jrm.2018.p0354.

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Recently, many studies on unmanned aerial vehicle (UAVs) that perform position control using camera images have been conducted. The measurements of the surrounding environment and position of the mobile robot are important in controlling the UAV. The distance and direction of the optical ray to the object can be obtained from the diameter and coordinates in the image. In these studies, various camera systems using plane cameras, fisheye cameras, or omnidirectional cameras are used. Because these camera systems have different geometrical optics, one simple image position measurement method cannot yield the position and posture. Therefore, we propose a new method that measures the position from the size of three-dimensional landmarks using omnidirectional cameras. Three-dimensional measurements are performed by these omnidirectional cameras using the distance and direction to the object. This method can measure three-dimensional positions from the direction and distance of the ray; therefore, if the optical path such as the reflection or refraction is known, it can perform measurements using a different optical system’s camera. In this study, we construct a method to obtain the relative position and relative posture necessary for the self-position estimation based on an object with an omnidirectional camera; further, we verify this method by experiment.

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de Sanctis, Ugo, Carlo Lavia, Marco Nassisi, and Savino D’Amelio. "Keraring Intrastromal Segment Depth Measured by Spectral-Domain Optical Coherence Tomography in Eyes with Keratoconus." Journal of Ophthalmology 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/4313784.

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Purpose. To evaluate agreement between measured and intended distance of Keraring (Mediphacos, Belo Horizonte, Brazil) intracorneal ring segments from the anterior and posterior corneal surfaces.Methods. Twenty-six Keraring ICRS implanted in 24 keratoconic eyes were examined. The distance from the Keraring apex to the anterior corneal surface and the distance from the inner and the outer corners to the posterior corneal surface were measured 3 months postoperatively using spectral-domain optical coherence tomography. Agreement between measured distance and intended distance was assessed by calculating the absolute differences and 95% limits of agreement (95% LoA).Results. The mean absolute difference was significantly lower (p<0.001) for the measurements taken at the inner corner (23.54±15.90 μm) than that for those taken at the apex (108.92±62.72 μm) and the outer corner (108.35±56.99 μm). The measurements taken at the inner corner were within ±25 and ±50 μm of the intended distance in 15/26 (57.7%) and 24/26 (92.3%) cases, respectively, and showed the narrowest 95% LoA with the intended distance (−57.61 to 55.15 μm).Conclusions. The distance of the inner corner from the posterior corneal surface showed the best agreement with the intended distance. This measurement is suitable for determining whether the actual Keraring depth matches the intended depth.

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Wang Yilin, 王一霖, 杨凌辉 Yang Linghui, 林嘉睿 Lin Jiarui, 刘洋 Liu Yang, and 邾继贵 Zhu Jigui. "Absolute Distance Measurement Based on Coherent Detection by Femtosecond Optical Frequency Comb." Acta Optica Sinica 39, no. 1 (2019): 0112003. http://dx.doi.org/10.3788/aos201939.0112003.

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Frost, Susan, Leslie Yates, and Hiroyuki Kumagai. "Bioinspired Optical Sensor for Remote Measurement of Small Displacements at a Distance." Biomimetics 3, no. 4 (October 30, 2018): 34. http://dx.doi.org/10.3390/biomimetics3040034.

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Identifying appropriate sites for landing a spacecraft or building permanent structures is critical for extraterrestrial exploration. By tracking the movement of land masses and structures on a planetary surface, scientists can better predict issues that could affect the integrity of the site or structures. A lightweight, low-cost, low-power bioinspired optical sensor is being developed at the National Aeronautics and Space Administration (NASA) Ames Research Center to remotely measure small displacements of land masses on either side of a fault. This paper describes the sensor, which is inspired by the compound eye vision system found in many insects, and the algorithms developed to estimate displacement. The results are presented for indoor and outdoor tests using the sensor to measure the displacement of a specially designed target that is located 0.35, 6, and 30 m from the sensor and is moved 10 mm to the left and right of a centered position, simulating the displacement of land masses on either side of a fault. Measurement uncertainties estimates were a few tenths of a millimeter when the target was located 0.35 and 6 m from the sensor. At the 30 m distance, corrections were required to obtain accuracies in the order of 1 mm.

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Tang, Guoqing, Xinghua Qu, Fumin Zhang, Xianyu Zhao, and Bo Peng. "Absolute distance measurement based on spectral interferometry using femtosecond optical frequency comb." Optics and Lasers in Engineering 120 (September 2019): 71–78. http://dx.doi.org/10.1016/j.optlaseng.2019.02.013.

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Obaton, A.-F., A. Quoix, and J. Dubard. "Uncertainties on distance and chromatic dispersion measurement using optical low-coherence reflectometry." Metrologia 45, no. 1 (January 18, 2008): 83–92. http://dx.doi.org/10.1088/0026-1394/45/1/012.

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Kervevan, Luc, Hervé Gilles, Sylvain Girard, Mathieu Laroche, and Yves Monfort. "Absolute distance measurement with heterodyne optical feedback on a Yb:Er glass laser." Applied Optics 45, no. 17 (June 10, 2006): 4084. http://dx.doi.org/10.1364/ao.45.004084.

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