In the traditional fringe projection profilometry system,the projector and the camera light center are both spatially virtual points.The spatial position relationships specified in the model are not easy to obtain,lea...In the traditional fringe projection profilometry system,the projector and the camera light center are both spatially virtual points.The spatial position relationships specified in the model are not easy to obtain,leading to inaccurate system parameters and affectingmeasurement accuracy.This paper proposes a method for solving the system parameters of the fringe projection profilometry system,and the spatial position of the camera and projector can be adjusted in accordance with the obtained calibration parameters.The steps are as follows:First,in accordance with the conversion relationship of the coordinate system in the calibration process,the calculation formula of the vertical distance from the camera light center to the reference plane and the calculation formula of the distance between the projector and the camera light center are given respectively.Secondly,according to the projector calibration principle,the position of the projector light axis perpendicular to the reference plane is gained by comparing the parallel relationship between the reference plane coordinate system and the projector coordinate system’s Z-axis.Then,in order to fulfill the position restriction that the line between the projector light center and the camera light center must be parallel to the reference plane,the camera’s spatial location is adjusted so that the vertical distance between it and the reference plane tends to that between the projector light center and the reference plane.And finally,the three-dimensional(3D)reconstruction of the target object can be finished using the phase height model’s system parameters once the aforementioned position limitations are put into practice.Experimental results demonstrate that the method improves the measurement accuracy,and verifies that it is effective and available in 3D shape measurement.展开更多
A method for measurement of ultra-low flying height in head-disk spacing is described. Three different wavelengths are selected out from white light by filters to measure the spacing simultaneously. Besides solving th...A method for measurement of ultra-low flying height in head-disk spacing is described. Three different wavelengths are selected out from white light by filters to measure the spacing simultaneously. Besides solving the ambiguity problem, a more reliable result is achieved by using weighted average of measurement results from three different wavelengths, where the weight is dependent upon spacing. Fringe-bunching correction algorithm (FBC) and spot-tilling technique are adopted to suppress calibration and random errors. Moreover, incident bandwidth correction (IBC) method is introduced to compensate the error caused by low monochromaticity of incident light. Based on dynamic flying height tester (DFHT Ⅱ), with the redesigned of photo-electric conversion and signal acquirement module, an instrument has been developed. And comparing the experimental data from the instrument with those from a KLA-FHT D6, the discrepancy is less than 5%. It indicates that the instrument is suitable to perform ultra-low flying height measurement and satisfies the reauirement of magnetic heads manufacturing.展开更多
Droplet clusters levitating over the locally heated water surface are considered a very promising phe-nomenon of microfluidics for the potential use of the droplets as unique microreactors for microbio-logical experim...Droplet clusters levitating over the locally heated water surface are considered a very promising phe-nomenon of microfluidics for the potential use of the droplets as unique microreactors for microbio-logical experiments.A new optical method is suggested for precise measurements of the sub-micron levitation height of single droplets.The method is based on the analysis of variable colors of the inter-ference halo around the droplet.For the first time,it is possible to measure the extremely low downward velocity of droplets,which grow due to steam condensation.This velocity was found to be 5-8 nm/s.The height of the levitation of various droplets just before their coalescence with a layer of water was also determined.Such measurements might be used for the verification of sophisticated models for the droplet levitation to be developed for a very thin layer of humid air under the droplet when the Knudsen effect should be taken into account.展开更多
Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry.Since the environmental temperature is not controlled in man...Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry.Since the environmental temperature is not controlled in many measurements,or is even varied on purpose,quantification of its effects on AFM dimensional measurements is needed.In this paper,the influences of the temperature in the entire environment of the AFM(excluding only the controller and computer)and that in the local environment around the tip–sample are investigated.The results show that lateral dimensional measurements are affected mainly by the entire environmental temperature.However,vertical measurements are influenced by the temperature of both the entire environment and the local environment.The effects become significant for temperatures higher than some threshold,here between 35 and 40 XC.展开更多
In the twin-roll strip casting process, hot cast strips can be broken or tom if the casting speed does not match the rolling speed. Usually, a certain length of hot steel strip is hung freely between the caster and ro...In the twin-roll strip casting process, hot cast strips can be broken or tom if the casting speed does not match the rolling speed. Usually, a certain length of hot steel strip is hung freely between the caster and rolling mill to deal with the effect of this speed difference. In this paper,the freely hanging hot steel strip is referred to as the free loop of hot steel strip. Accurately measuring and controlling the height of this free loop is the key factor in maintaining a stable casting operation. Several methods for measuring the loop height of a steel strip are discussed and a method for accurately measuring and controlling the free loop height of hot steel strip is presented. Based on the results of the casting loop quantity change curve, this control method is confirmed to be effective and able to meet the requirements of continuous casting strip production.展开更多
Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitud...Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.展开更多
基金This work described in this paper is supported by Foundation of Jilin Province Department of Science and Technology under Grant YDZJ202201ZYTS531。
文摘In the traditional fringe projection profilometry system,the projector and the camera light center are both spatially virtual points.The spatial position relationships specified in the model are not easy to obtain,leading to inaccurate system parameters and affectingmeasurement accuracy.This paper proposes a method for solving the system parameters of the fringe projection profilometry system,and the spatial position of the camera and projector can be adjusted in accordance with the obtained calibration parameters.The steps are as follows:First,in accordance with the conversion relationship of the coordinate system in the calibration process,the calculation formula of the vertical distance from the camera light center to the reference plane and the calculation formula of the distance between the projector and the camera light center are given respectively.Secondly,according to the projector calibration principle,the position of the projector light axis perpendicular to the reference plane is gained by comparing the parallel relationship between the reference plane coordinate system and the projector coordinate system’s Z-axis.Then,in order to fulfill the position restriction that the line between the projector light center and the camera light center must be parallel to the reference plane,the camera’s spatial location is adjusted so that the vertical distance between it and the reference plane tends to that between the projector light center and the reference plane.And finally,the three-dimensional(3D)reconstruction of the target object can be finished using the phase height model’s system parameters once the aforementioned position limitations are put into practice.Experimental results demonstrate that the method improves the measurement accuracy,and verifies that it is effective and available in 3D shape measurement.
基金National Basic Research Program of China(973 Program,No. 2003CB716207)National Natural Science Foundation of China(No.50775091)
文摘A method for measurement of ultra-low flying height in head-disk spacing is described. Three different wavelengths are selected out from white light by filters to measure the spacing simultaneously. Besides solving the ambiguity problem, a more reliable result is achieved by using weighted average of measurement results from three different wavelengths, where the weight is dependent upon spacing. Fringe-bunching correction algorithm (FBC) and spot-tilling technique are adopted to suppress calibration and random errors. Moreover, incident bandwidth correction (IBC) method is introduced to compensate the error caused by low monochromaticity of incident light. Based on dynamic flying height tester (DFHT Ⅱ), with the redesigned of photo-electric conversion and signal acquirement module, an instrument has been developed. And comparing the experimental data from the instrument with those from a KLA-FHT D6, the discrepancy is less than 5%. It indicates that the instrument is suitable to perform ultra-low flying height measurement and satisfies the reauirement of magnetic heads manufacturing.
基金support by the Ministry of Science and Higher Education of the Russian Federation (project No.FEWZ-2023-0002).
文摘Droplet clusters levitating over the locally heated water surface are considered a very promising phe-nomenon of microfluidics for the potential use of the droplets as unique microreactors for microbio-logical experiments.A new optical method is suggested for precise measurements of the sub-micron levitation height of single droplets.The method is based on the analysis of variable colors of the inter-ference halo around the droplet.For the first time,it is possible to measure the extremely low downward velocity of droplets,which grow due to steam condensation.This velocity was found to be 5-8 nm/s.The height of the levitation of various droplets just before their coalescence with a layer of water was also determined.Such measurements might be used for the verification of sophisticated models for the droplet levitation to be developed for a very thin layer of humid air under the droplet when the Knudsen effect should be taken into account.
基金the National Natural Science Foundation of China(No.51675504)the Fundamental Research Funds for the Central Universities(No.WK2090000022).
文摘Atomic force microscopy(AFM)is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry.Since the environmental temperature is not controlled in many measurements,or is even varied on purpose,quantification of its effects on AFM dimensional measurements is needed.In this paper,the influences of the temperature in the entire environment of the AFM(excluding only the controller and computer)and that in the local environment around the tip–sample are investigated.The results show that lateral dimensional measurements are affected mainly by the entire environmental temperature.However,vertical measurements are influenced by the temperature of both the entire environment and the local environment.The effects become significant for temperatures higher than some threshold,here between 35 and 40 XC.
文摘In the twin-roll strip casting process, hot cast strips can be broken or tom if the casting speed does not match the rolling speed. Usually, a certain length of hot steel strip is hung freely between the caster and rolling mill to deal with the effect of this speed difference. In this paper,the freely hanging hot steel strip is referred to as the free loop of hot steel strip. Accurately measuring and controlling the height of this free loop is the key factor in maintaining a stable casting operation. Several methods for measuring the loop height of a steel strip are discussed and a method for accurately measuring and controlling the free loop height of hot steel strip is presented. Based on the results of the casting loop quantity change curve, this control method is confirmed to be effective and able to meet the requirements of continuous casting strip production.
基金supported by the Equipment Pre-research Project(GK202002A020068)。
文摘Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.