Accuracy Of Position Detection Research Articles

3D Position Detection of A Moving Object in Active Stereo Vision System with Multi-DOF Motion

This paper describes a strategy to improve the accuracy of 3D position detection of a moving object. Stereo vision is one of powerful methods to detect a target position. However the measurement accuracy depends on the configuration of a target object and two cameras of vision system. In this case, these exist a camera configuration that enables to improve the measurement accuracy of object position. On the other hand, the camera system requires a multi-DOF motion to realize fast tracking of moving object. To address the above issues, a stereo vision system with multi-DOF motion is developed in this research. The constructed vision system has two hand-eye system that are controlled independently. In the proposed strategy, two performance indices are considered to determine the manipulator motion of hand-eye system. One is camera configuration index to evaluate the performance of the position detection by the stereo vision. The other is a manipulability measure of the manipulator in the hand-eye system. Considering both indices to determine the motion of hand-eye system, the tracking performance of stereo vision system is improved. Numerical and experimental results show the availability of the proposal method.

Electromagnetic articulograph based on a nonparametric representation of the magnetic field.

Electromagnetic articulograph (EMA) devices are capable of measuring movements of the articulatory organs inside and outside the vocal tract with fine spatial and temporal resolutions, thus providing useful articulatory data for investigating the speech production process. The position of the receiver coil is detected in the EMA device on the basis of a field function representing the spatial pattern of the magnetic field in relation to the relative positions of the transmitter and receiver coils. Therefore, the design and calibration of the field function are quite important and influence the accuracy of position detection. This paper presents a nonparametric method for representing the magnetic field, and also describes a method for determining the receiver position from the strength of the induced signal in the receiver coil. The field pattern in this method is expressed by using a multivariate spline as a function of the position in the device's coordinate system. Because of the piecewise property of the basis functions and the freedom in the selection of the rank and the number of the basis functions, the spline function has a superior ability to flexibly and accurately represent the field pattern, even when it suffers from fluctuations caused by the interference between the transmitting channels. The position of the receiver coil is determined by minimizing the difference between the measured strength of the received signal and the predicted one from the spline representation of the magnetic field. Experimental results show that the error in estimating the receiver position is less than 0.1 mm for a 14 x 14-cm measurement area, and this error can be further reduced by using a spline-smoothing technique.

Scintillator identification and performance characteristics of LSO and GSO PSPMT detector modules combined through common X and Y resistive dividers

Combining signal channels from detector arrays can reduce complexity and minimize cost but, potentially, at the expense of other performance parameters. The authors evaluated a method that reduces the number of signals by combining the anode outputs of three position-sensitive photomultiplier tubes (PSPMTs) through a common X resistive charge divider and three individual Y resistive charge dividers. Field flood images at 511 keV of two LSO modules combined with a single GSO module were compared to images obtained when the modules were illuminated separately. At moderate count rates only a small reduction in position detection accuracy was observed in the combined tubes. Event mis-positioning was minimal for total count rates <300,000 cps. At higher rates, pulse pileup degraded accuracy. Delayed charge integration, a method for identifying scintillators by differences in their light decay times, allowed the LSO and GSO arrays to be distinguished from one another and also reduced the effect of pulse pileup. Thus, combining PSPMTs anodes through common X and common Y resistive dividers may be useful in reducing signal number from PSPMT detector modules while maintaining good event localization and scintillator identification accuracy at reasonable event rates.

Development of groove recognition algorithm with visual sensor. Practical development of visual sensor for welding robot (1st Report)

Summary To improve the automation or artificial intelligence of welding operations, it is necessary to develop high-performance sensors. Laser visual sensors are designed to recognise the configuration or detect the position of a weld by irradiating a slit light on to the welded joint, receiving the light with a CCD camera, and converting the two-dimensional information into three-dimensional information by image processing. The visual sensors for welding robots must be free from the influences of welding process disturbances, such as arc light, heat, spatter and fume. This paper describes optical component arrangements and image processing algorithms. The optical component of a sensor head helps avoid optical window contamination caused by spatter or fume. The image processor used can process image data quickly and accurately even if welding arc light illuminates the workpiece surface. The accuracy of weld position detection is within ±0.2 mm.

A study of inter-crystal scatter in small scintillator arrays designed for high resolution PET imaging

Inter-crystal scatter causes mispositioning of scintillation events, which is of particular concern in imaging detectors based on small discrete scintillator elements. Because it is difficult to measure the scatter and its effects on detector intrinsic spatial resolution, a Monte Carlo simulation has been used to study inter-crystal scatter effects for evaluating and optimizing the design of a high resolution animal PET detector based on an array of small scintillator crystals. In this simulation, the authors quantitatively assess the mispositioning of events due to inter-crystal scatter as a function of parameters such as different scintillator materials, crystal geometry, /spl gamma/-ray incident angle and applied energy threshold. In analyzing the tradeoff between the detector efficiency and the position detection accuracy, the authors found that the mispositioning is not sensitive to the energy threshold, however it does change rapidly with the crystal length and the gap between crystals. The authors also compared four different crystal positioning algorithms to provide a theoretical estimate of positioning accuracy and to determine the best algorithm to use. To study how inter-crystal scatter affects detector spatial resolution, the authors analyzed the coincidence line spread function with and without inter-crystal scatter and found that the inter-crystal scatter had very little effect on the FWHM and FWTM of the coincidence line spread function.

Integrated photocapacitive position-sensitive detector made in CMOS technology

Abstract An integrated photocapacitive edge-detector consisting of a circle-circular ring device and two charge-balancing converters is described. The integrated sensors are produced using a conventional 1.5 μm CMOS technology. The theoretical background and design as well as the operation are explained. Experimental results of optical edge-detection show an accuracy of position detection of the centre of the sensor structure of about 2 μm.

Global tracking of the ocular fundus pattern imaged by scanning laser ophthalmoscopy

This paper presents an algorithm for the automatic global tracking of ocular fundus landmarks in video image sequences generated by scanning laser ophthalmoscopy (SLO). The tracking algorithm is based on the computation of the discrete unnormalized cross-correlation of an interactively preselected small template and respective images in time sequences of fundus patterns. The correlation is executed with binary images derived from an automatical threshold limitation of the grey-value images. Due to the { +1 −1 } representation of the binary images the unnormalized correlation functions directly relate to the Hamming distance of the template and the objects in the images. Experiments show that even templates with features distorted by noise are accurately recognized at any position. The accuracy of position detection is better than 0.4%. Possible hardware implementations of the algorithm which would reduce computation time are briefly mentioned.

Required accuracy in manufacturing process of three‐wire transmission line used in inductive radio system for detecting linear motor vehicle position

AbstractThe three‐wire transmission lines consisting of square‐wave‐formed line conductors has a structure in which any two of the three line conductors iterate narrow and wide sections at a specified interval along the longitudinal direction. Among those sections, the narrow section has the following problem. If line conductors deviate even a little from their normal positions due to the inaccuracies in the manufacturing process, relatively large unbalances will be produced in the mutual impedances and admittances between them. This leads to the crosstalk between the positive and negative phase sequence components of the signal and consequently to the detection error in the position of the vehicle. We considered the case where the manufacturing inaccuracies distribute at random or uniformly along the longitudinal direction. A quantitative analysis is made for the problem arriving at a guide for the manufacturing accuracy of the transmission line, which is required to ensure the desired accuracy of position detection. It is desirable in the narrow section that the two conductors maintain a distance above a certain value. It is also desirable that the radius of the line conductor be as small as possible, as long as the transmission loss of the line is within the tolerable value. Compared with the transmission line consisting of helically wound conductors, which we have already reported, there will still be a more strict requirement on the manufacturing accuracy on the transmission line consisting of square‐wave‐formed conductors.

微分処理により抽出された特徴点の３次元位置を検出するレーザ光走査型センサ

This research deals with an active three-dimensional position sensor with laser beam. The sensor has a unique function of differentiation processing of a linear image to extract only the points to be detected at which luminous intensity changes. Since it is composed of a linear image sensor and a one-dimensional PSD, both with high resolution, it is designated to be of high speed and accuracy.In the present paper, the structure of the sensor and the sensing mechanism with image processing are described and a signal processing circuit to improve the accuracy of position detection is considered. Finally, the sensor is installed as a vision to a manipulator, to detect points on a stair-shaped object.

Accurate position detection of targets in noise image

Targets at various positions in a noise image were detected by the optical matched filtering technique. In this case the thermoplastic optical recorder was used as a matched filter recorder. High accuracy of position detection was obtained, i.e. the position error was 2% or less.

A dual grating alignment technique for x-ray lithography

In order to realize a highly accurate alignment technique for submicron x‐ray lithography, we have developed a new dual grating alignment technique capable of detecting both the lateral position and gap with resolutions of 0.01 and 0.1 μm, respectively. In a conventional dual grating alignment scheme, the alignment signal is the difference in intensities of +1st and −1st order diffracted light from a pair of grating marks on the mask and wafer. However, it is difficult to apply the above scheme to a practical alignment system in spite of its high detection sensitivity capability. The reason for this is that the alignment signal is very sensitive to variations in the gap between the mask and wafer. To overcome this disadvantage, we have analyzed the influence of the gap variations on position detection accuracy, and found that the sum of intensities between +1st and −1st order diffracted light reaches maximum when the gap is equal to a specific value. This characteristic applies to any lateral displacement value. Therefore, it is easy to control the gap by detecting the sum of diffracted light intensities. On the other hand, at the specific gap value mentioned above, the intensity sum reaches minimum or maximum, respectively, when the relative lateral displacement is equal to 0 or 1/2 grating pitch. In this case, the lateral displacement which indicates the maximum or minimum intensity is not affected by gap variations. Therefore, it is possible to align the lateral position by detecting the sum of intensities. By using this new dual grating alignment technique, very high accuracy alignment in a proximity mode can be realized.

The Effect of Random Perturbation on Position-Detection Accuracy

A random perturbation about the true position of a target image is shown to improve the position-detection accuracy of systems which operate on quantized data. For a two-sensor receptor the random perturbation is shown to decrease the position error measurably. For a multisensor receptor the random perturbation is shown to drive the position error to zero.

Experimental Verification of Signal Perturbation Applied to the Accuracy of Position Detection

Photodiodes and photo transistors are presently being applied to many fields to convert optical signals into electrical signals. One application of these devices is in a position detection system. The accuracy of such a system is limited by nonlinearities due to these devices. Through signal perturbation, a method in which an extra signal of higher frequency is added to the input of the receptor, the nonlinearities can be altered and the accuracy improved. The theory for this technique is well understood; however, very little experimental data have been reported. This method has been experimentally tested and the results have been compared with those predicted by the theory.

On the Improvement of Position-Detection Accuracy Using Signal Perturbation Theory

It is shown that a triangular perturbation signal provides increased position-detection accuracy over that provided by a sinusoidal perturbation signal [1]. Triangular perturbation is applied to a two-element photosensor receptor, resulting in perfect position detection within the dimensions of the receptor. It is also shown that perfect position detection can be obtained over as large a range as desired by using a many-element zero-deadband one-dimensional receptor subjected to triangular perturbation.