Short-range Measurement Research Articles

Higher Precision Encoder Using Hologram Scale

Semiconductor manufacturing equipment requires improvement of the accuracy by a linear encoder in a short measurement range. The error in the short range involves the interpolation error and other errors. Improvement in the interpolation error had already achieved in existing research. In contrast, this paper describes the development of a grid interferometer-type linear encoder using a hologram scale with excellent accuracy in a short measurement range. The developed encoder can achieve the error excluding interpolation error less than 10-6 magnitude per measurement range of 50 μm. In the development, error factors in the short-range measurement were examined. An equipment to identify the accuracy in this short-range measurement with high resolution and accuracy was then developed. Error analysis by the developed accuracy measurement equipment made it possible to improve a linear encoder accuracy. As a result, the accuracy of grid interferometer type linear encoder was able to reach at ±20 pm in the measurement range of 50 μm.

High-accuracy calibration method for an underwater one-mirror galvanometric laser scanner.

Three-dimensional (3D) perception of deep-sea targets is the key to autonomous operation of underwater equipment (e.g., underwater robots). Underwater one-mirror galvanometric line-laser scanner has advantages for short-range measurement, but it is difficult to achieve high calibration accuracy due to installation errors and refraction effects. For this reason, in this paper, a high-accuracy refraction-considered and installation-error-independent calibration method is proposed for the vision system. Firstly, to address the difficulty of aligning the incident light plane with the galvanometer shaft, a high-accuracy land-based installation-error-independent model is proposed, which avoids the influence of the installation errors and allows the real shaft axis and the light-plane cluster poses to be calculated using only three light planes. Subsequently, considering the underwater refraction, a 3D model is established for simulating refractive behaviors of the light-plane cluster, and then a partition-based method is proposed for calibrating the underwater light-plane cluster, which further improves the calibration accuracy of the scanner in underwater measurement scenarios. Finally, a one-mirror galvanometric laser scanner is developed in the laboratory to verify the calibration accuracy and to perform the 3D measurement experiments of underwater targets. The results show that the calibration accuracy of the proposed land-based installation-error-independent model is improved 2 times more compared with the traditional installation-error-dependent model. Additionally, the measurement accuracy of the scanner for the standard sphere is 11.98 µm and 12.75 µm in the air and underwater measurement scenarios, and the two measurements are in good agreement. The above results comprehensively verify the high accuracy of the calibration method proposed in this paper.

Design of Planar Array Transducers Based on Connected 1–3 Piezoelectric Composites

To improve the transmission performance and preparation of a transducer array, two planar array transducers based on connected 1–3 piezoelectric composites as a matrix were designed. Each transducer contained 25 array elements with a gap of 1 mm between them. The length, width and height of each array element were 1 mm, 26 mm and 5 mm, respectively. Two kinds of array transducers were tested through finite element simulation and experiments. The array transducer prototype was fabricated based on two kinds of composite materials, and the fabrication cycle was short. Our results show that the maximum transmission voltage response of the two-phase 1–3 full array driver is up to 179 dB at 200–400 kHz and the acoustic radiation intensity can be increased by up to 22% compared with the traditional splicing transducer array. It is suitable for short-range target positioning and measurement. Moreover, in the single element mode, the beam of the three-phase 1–3 transducer has no sidelobe and a single element −3 dB beam width of up to 91°. Furthermore, the beam width of the two-phase 1–3 type is 54°, and the acoustic radiation breadth is improved by 40.6%. The three-phase 1–3 type array transducer has the characteristics of concentrated acoustic transmission energy of the whole array, and its −3 dB beam width is 3.5°. The beam width decreased by 12.5%, indicating that the three-phase 1–3 type transducer is suitable for short-range target detection and perception. The two array transducers have their own advantages in transmitting the voltage response and beam width, which must be selected on the basis of the requirements of practical applications.

Dynamic Internal Motion of GPCR on Live Cells

G protein-coupled receptors (GPCRs) are seven-transmembrane receptors, which transmit extracellular signals inside cells via activation of G proteins. GPCRs are involved in a wide variety of physiological functions such as signal sensing, immune system, and neurotransmission. Indeed, half of the drugs directly or indirectly target GPCRs. Although structures and function of GPCRs have been well studied, little has been known about the real-time dynamics in signal transduction. In this study, we used Diffracted X-ray Tracking (DXT) and Diffracted X-ray Blinking (DXB) techniques for the analysis. They elucidate protein dynamics through the analysis of diffraction spots from the gold nanocrystals labeled on the protein surface, and are very precise single-molecular analytical techniques. Serotonin receptor subtype 2A (5-HT2A) was transiently expressed on HEK 293 cells, and the gold nanocrystals were attached to the N-terminally introduced FLAG-tag. Short range measurement was performed by DXT (100/frame), which tracks the movement of diffraction spots. At microsecond time scale, internal motion of 5-HT2A was much higher in the ligand-free condition (2.70 Å/ms) than that of the ligand-binding condition (0.87 Å/ms). In contrast, long range measurement by DXB (100 ms/frame) presented opposite results. DXB analyses the continuation of signals by calculating the auto-correlation function of each pixel from recorded data. At millisecond time scale, internal motion of the ligand binding 5-HT2A was faster than that of ligand-free condition. These dual-natured data may suggest that we succeeded in extracting two different modes of 5-HT2A motion on live cells; fluctuation of 5-HT2A on the cell membrane at micro-second range, and ligand-induced dynamic motion of 5-HT2A at milli-second range. This is probably a first report to demonstrate the ligand induced intramolecular motion of GPCRs on live cells.

The development and tests of remote data acquisition and transmission system on civil engineering structural vibration

ABSTRACT Aiming at the difficult problem of on-site real-time vibration responses monitoring and remote data transmission of the civil engineering structures, based on LabVIEW a remote data acquisition and transmission system is designed. In the system NI data acquisition card and DataSocket protocol of the LabVIEW software platform are used to realize data collection, remote transmission and control. That is, the civil engineering structural vibration responses can be monitored through internet at anytime and anywhere. The vibration parameters of a cantilever beam is detected and transmitted in real-time by using this system. The test parameter values are compared with the theoretical calculating value. The results show that relative to the traditional cable measurement and wireless short-range measurement, this system can effectively realize the remote real-time data acquisition, transmission, display, storage and control. Furthermore, the accuracy of data transmission is high. On the other hand, the system is easy to be built and maintained.

The analysis and measurement of motion errors of the linear slide in fast tool servo diamond turning machine

This article proposes a novel method for identifying the motion errors (mainly straightness error and angular error) of a linear slide, which is based on the laser interferometry technique integrated with the shifting method. First, the straightness error of a linear slide incorporated with angular error (pitch error in the vertical direction and yaw error in the horizontal direction) is schematically explained. Then, a laser interferometry–based system is constructed to measure the motion errors of a linear slide, and an algorithm of error separation technique for extracting the straightness error, angular error, and tilt angle error caused by the motion of the reflector is developed. In the proposed method, the reflector is mounted on the slide moving along the guideway. The light-phase variation of two interfering laser beams can identify the lateral translation error of the slide. The differential outputs sampled with shifting initial point at the same datum line are applied to evaluate the angular error of the slide. Furthermore, the yaw error of the slide is measured by a laser interferometer in laboratory environment and compared with the evaluated values. Experimental results demonstrate that the proposed method possesses the advantages of reducing the effects caused by the assembly error and the tilt angle errors caused by movement of the reflector, adapting to long- or short-range measurement, and operating the measurement experiment conveniently and easily.

A Study on Multi DOF Magnetic Scale for Motion Control Compensation of Machine Tool

Following to the previous paper reporting the motion control compensation for machine tool by 2 dimensional scale system, we hereby propose the Magnetic principle special scale for motion control compensation of machine tool. The authors investigated the compensation of the collateral movement orthogonal to the principle direction, which will affect the accuracy of the machine, by adding the orthogonal, 2-directional, short range measurement. The authors expected the improvement of compensation accuracy by continuously monitoring the relative motions between the movement of the bed and machine components with respect to the principle direction as well as to the direction of collateral movement, because the monitoring prompts re-acquisition of compensation data when the deviation from the initial compensation data becomes significant, enabling additional compensation for the dynamic motion error caused by cutting force etc. Firstly, this paper estimates the amount of motion error due to cutting force, the weight and acceleration force of the bed, using middle sized machine tool model. Then the paper presents the approximate required performance of the multi DOF scale. Finally, the paper reports the basic and elemental performance of magnetic multi DOF scales for motion error compensation, by prototyping the rotary scales.

Low-cost resolution improvement technique for short distance measurement systems

In this work, a new scheme for short-range distance measurement is presented. It reduces significantly the amount of signal processing needed for frequency-modulated continuous-wave radar or Lidar systems to obtain a good resolution in beat frequency measurement. In this article, a low cost and easy to implement technique is proposed. This resolution improvement is achieved by simple previous processing of the beat signal. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1496–1498, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25243

Estimating marine sediment attenuation at low frequency with a vertical line array

This paper presents a method of determining the compressional wave attenuation in marine sediment from a short range measurement. The data were collected on a vertical line array at a range of 230 m during the Shallow Water 2006 experiments. The sediment attenuation is extracted from the signal strength ratio of the sea bottom reflection to a sub-bottom reflection at different frequencies from 1.75 to 3.15 kHz. Linear frequency dependence of the attenuation is found from the estimation. The sediment attenuation estimate is lower than the values estimated from the inversions of acoustic field data previously done in the vicinity.

CRLB analysis of wireless cognitive location with different short-range measurements

Because of the wide application and great market potential of location-aware services, the research of wireless location techniques for the fourth generation (4G) mobile communications is being paid more attention. Wireless cognitive location (WCL) techniques for next generation wireless networks have been proposed in recent years. This article investigates the changes of the positioning accuracy of WCL algorithm when different methods are adopted to measure the short-range (SR) information. By first completing Cramér-Rao lower bound (CRLB) analysis of the WCL algorithm with SR measurements based on time of arrival (TOA) and received signal strength (RSS), it is discovered that TOA-based or time difference of arrival (TDOA) -based SR measurement can make WCL algorithms achieve higher accuracy than RSS mode, which is also verified by numerical simulation in the article. The conclusions can instruct the design of novel WCL-based location algorithms.

Short-range displacement detection from speckle interference using transparent thin-film photodiode

Speckle interference in space was monitored by using a newly developed transparent thin-film photodiode, which was fabricated by micromachining techniques. Since the sensitive region of the developed photodiode was thinner than one-half of the wavelength, an optical standing wave generated by the interference between two waves propagating in opposite directions was detected. This photodiode was used in a short-range displacement measurement in a speckle field. Using the sinusoidal phase modulation technique, object displacement was sensed with an accuracy of about 30 nm in a speckle granular structure.

High precision, short range ultrasonic sensing by means of resonance mode-locking

This report describes a novel method of continuous-wave operation of ultrasonic transducers, which enables short-range measurement with a resolution much finer than the sound wavelength. The transducer is locked into a particular resonant mode of the transducer-gap-reflector system by a resonance-locking phase-locked loop. The resonant frequency depends on the relative coherence of the transmitted and reflected waves, so that a change in the position of the reflecting surface will require a corresponding change in the resonance frequency if the resonant mode is to be retained. A simple system of this type has been implemented using a cheap, commercially available transducer with far-from-optimum characteristics. The system has been found to operate successfully in a range well below the typical ring-down range of a corresponding pulse-echo system, and has displayed a resolution much finer than the sound wavelength for the transducer.

Comparison of short range and asymptotic measurements of the kinetic energy distributions of laser ablated aluminum atoms

We compare the kinetic energy distributions of ultraviolet excimer laser ablated A1 atoms measured within 1 cm of the metal surface by optical transient absorption, to those measured over 20 cm from the surface by pulsed photoionization time-of-flight mass spectrometry. For the mild ablation conditions used the distributions are the same. This result demands the existence of a good one-to-one correspondence of atomic velocity to distance traveled from the ablated surface on the ∼1 μs timescale of the short range measurement, suggesting that the duration of the A1 atom production period is ≤100 ns. This study establishes the viability of a novel concept for a compact velocity selection scheme for faster laser ablated neutral species.

Automatic short‐range measurement of the cloud flash to ground flash ratio in thunderstorms

The principle of operation of an instrument designed for automatic long‐term measurement of the cloud flash to ground flash ratio in thunderstorms is described. The instrument uses a simple antenna to detect the electric field of lightning and is designed to have an effective range of about 14 km and a maximum range of about 20 km. Wave‐shape feature measurement is used to distinguish between the electric field wave‐shapes corresponding to cloud and ground flashes and is based principally on the presence of relatively large, well‐spaced, positive‐going changes (R changes) in the field changes caused by ground flashes. From observations with the instrument over two thunderstorm seasons from September 1982 to May 1984 in Brisbane, Australia, the cloud flash to ground flash ratio was 3.0. Large variations were observed in the ratio of cloud flashes to ground flashes for individual thunderstorm days. For days on which at least 100 total registrations occurred, the range was 0.9 to 24.7. Possible applications of an instrument of this type in atmospheric electricity studies are discussed.

A completely automatic pressure measurement apparatus

A description is given of a fully automatic vapour pressure measurement apparatus. The equipment uses the static method with a glass spoon gauge. The pressure range is 0.01-760 Torr. The temperature range is -100 to 300 degrees C. The principal control units of the apparatus are described separately. The accuracy of pressure measurement is 0.01 Torr and the temperature stability for short range measurement is 0.1 degrees C and for long range measurement 0.5 degrees C. As a test the experimental vapour pressure values of water are given in the region. -10 to 78 degrees C. There is good agreement with the accepted values in the literature.

THE SECOND R.I.C.S. LAND SURVEYORS CONFERENCE AT SHRIVENHAM, 10—12 APRIL, 1970

Abstract A general account of this Conference, concentrating on the domestic issues, has already appeared in the Chartered Surveyor for June 1970 (Vol. 102, No. 12, pp. 576–578). This review of the Conference will therefore be confined to the technical side of it. The author's thanks are due to Messrs. J. R. Smith and J. D. Leatherdale, from whose notes and tape recording it has been compiled. There were two technical sessions on subjects of considerable interest to land surveyors—desk computers and short-range electromagnetic distance measurement.