Scanning Operation Research Articles

An optimized strategy for automatic optical scanning of objects in reverse engineering

The paper reports on a methodology for complete automation of the process of scanning the surface of an unknown object through the utilization of optical range sensors. An incremental model representing object surface and workspace occupancy is used to define an optimization strategy for selecting the best scanning viewpoints and generate adaptive collision-free scanning trajectories. The optimization strategy proposed attempts to select the viewpoints that maximize the knowledge of the object taking into account the status of the current model and the constraints associated with the range sensor and positioning system. One of the novel aspects of this work is the fact that viewpoint selection and scanning path definition are performed automatically on the basis of a simple volumetric model in situations where potential collisions may arise. The ability to control the quality of acquired data and the reduction in global scanning trajectories when compared with manual scanning operations are other important aspects. The proposed approach is sufficiently general to be used in different scanning system configurations.

Endoscope-assisted KTP laser sinus clear-out procedure for recurrent ethmoid polyposis.

Surgery for recurrent sinusitis with diffuse polyposis is challenging since tortuous sinus anatomy and bleeding tendency can make revision surgery particularly difficult. We report the efficacy in using KTP laser under the assistance of endoscope to perform sinus clear-out procedure for patients with recurrent ethmoid polyposis. Thirteen patients with recurrent ethmoid polyposis underwent this procedure between November 1996 and July 2000. All were available for follow-up. Patients all had a KTP sinus clear-out procedure (15-20 W continuous mode, spot size 0.4-0.8 mm, contact or near-contact approaches) assisted by endoscope. Sinus endoscopic findings, CAT scan data, operation records and perioperative courses were retrospectively reviewed. The mean follow-up period was 24.7 +/- 11 months. Surgeries all went smoothly with minimal bleeding incurred. All patients demonstrated significant improvement in their sinonasal symptoms. Two cases (15.4%) had localized recurrent polyps. With its excellent capabilities in hemostasis, great intra-nasal maneuverability, and flexible operation modes, KTP laser is an ideal alternative to manage recurrent ethmoid polyposis for selected cases.

Nanoscale friction reduction and fatigue monitoring due to ultrasonic excitation

DLC film interfacial fatigue and changes in friction coefficient phenomena were investigated during quasi-static nanoindentation/scratch while the sample surface was excited ultrasonically. An original experimental setup combines nanoindenter, SPM scanner and ultrasonic transducer operating in an elastic standing wave mode. Nanoindentation loading–unloading curves revealed delamination induced excursions after a certain number of ultrasonic loading cycles. Drastic changes in quasi-statically monitored friction coefficient during nanoscratch were correlated with sample vibration amplitude and loading force. Resulting indentation/scratch film delamination effects and surface wear patterns were examined by an in situ SPM technique. Ultrasonically excited nanoindentation and nanoscratch techniques can be considered as fast and qualitative methods to characterize critical tribo surfaces for data storage devices.

On the use of random limited-scan to improve at-speed random pattern testing of scan circuits

A method is proposed for improving the fault coverage that can be achieved by random patterns for circuits with scan. Under the test application scheme considered, primary input sequences are applied at-speed between scan operations. The proposed method uses limited scan operations to improve the fault coverage. Under a limited scan operation, the circuit state is shifted by a number of positions which may be smaller than the number of state variables. Limited scan operations are inserted randomly to ensure that the complete test set can be generated by a random pattern generator. Experimental results show that complete fault coverage is achieved by the proposed method, i.e., the proposed method detects all the detectable circuit faults, for all the benchmark circuits considered.

Test compaction for at-speed testing of scan circuits based on nonscan test. sequences and removal of transfer sequences

Proposes a procedure for generating compact test sets with enhanced at-speed testing capabilities for scan circuits. Compaction refers here to a reduction in the test application time, while at-speed testing refers to the application of primary input sequences that contribute to the detection. of delay defects. The proposed procedure generates an initial test set that has a low test application time and consists of long sequences of primary input vectors applied consecutively. To construct this test set, the proposed procedure transforms a test sequence T/sub o/ for the nonscan circuit into a scan-based test by selecting an appropriate scan-in state and removing primary input vectors from T/sub o/ if they do not contribute to the fault coverage. If T/sub o/ contains long transfer sequences, several scan-based tests with long primary input sequences may be obtained by replacing transfer sequences in T/sub o/ with scan operations. This helps reduce the test application time further. We demonstrate through experimental results the advantages of this approach over earlier ones as a method for generating test sets with minimal test application time and long primary input sequences.

Automated laser scanning system for reverse engineering and inspection

Recently, laser scanners have been used more often for inspection and reverse engineering in industry, such as for motors, electronic products, dies and molds. However, due to the lack of efficient scanning software, laser scanners are usually manually operated. Therefore, the tasks that involve inspection and reverse engineering processes are very expensive. In this research, we propose an automated measuring system for parts having a freeform surface. In order to automate a measuring process, appropriate hardware system as well as software modules are required. The hardware system consists of a laser scanning device and setup fixtures that can provide proper location and orientation for the part to be measured. The software modules generate optimal scan plans so that the scanning operation can be performed accordingly. In the scan planning step, various scanning parameters are considered in the generation of optimal scan paths, such as the view angle, depth of field, the length of the stripe, and occlusion. In the scanning step, the generated scan plans are downloaded to the industrial laser scanner and the point data are captured automatically. The measured point data sets are registered automatically and the quality of point data is evaluated by checking the difference between the CAD model and the measured data. To demonstrate an automated measuring system, a motorized rotary table with two degrees of freedom and a CNC-type laser scanner with four degrees of freedom are used.

실시간 연관규칙 탐사를 위한 능동적 후보항목 관리 모델

미디어의 발달과 생활 패턴의 변화를 토대로 새롭게 나타나고 있는 다양한 판매 패턴들을 분석하는데 있어 단일한 분석 방법을 적용하는 것은 효과적이지 못하다. 특히 신선 식품이나 기념일 주변에서 집중적인 매출이 발생하는 품목들은 제한된 시간 내에 판매를 최대로 해야 하는 시간적 제약을 갖는다. 그러나 기존의 연관규칙 탐사 기법은 대규모 거래 데이터베이스로부터 반복적 스캔 연산을 통해 연관규칙 탐사를 수행하기 때문에 제한된 시간안에서 빈번히 필요로 하는 패턴을 분석하기에는 비효율적이기 때문이다. 따라서 이 논문에서는 시간 제약을 갖는 특수한 판매 패턴에 대한 실시간 연관규칙 탐사가 가능하도록 하기 위해 트리거와 저장 프로시져를 이용한 점진적 후보항목 관리 모델을 제안한다. 아울러 이 논문에서는 제안 모델의 구현 및 실험을 통해 그 성능 특성의 분석도 수행한다. 특히 이 논문에서 제안하는 방법은 이중 해쉬 기법을 이용함으로써 연산의 성능을 향상시킨다. Considering the rapid process of media's breakthrough and diverse patterns of consumptions's analysis, a uniform analysis might be much rooms to be desired for interpretation of new phenomena. In special, the products happening intensive sails on around an anniversary or fresh food have the restricted marketing hours. Moreover, traditional association rule discovery algorithms might not be appropriate for analysis of sales pattern given in a specific time because existing approaches require iterative scan operation to find association rule in large scale transaction databases. in this paper, we propose an incremental candidate set management model based on twin-hashing technique to find association rule in special sales pattern using database trigger and stored procedure. We also prove performance of the proposed model through implementation and experiment.

An Efficient Deterministic Test Pattern Generator for Scan-Based BIST Environment

To obtain satisfactory fault coverage for testing a logic circuit, linear feedback shift registers (LFSRs) have been used to generate not only the pseudorandom, but also the deterministic patterns in the scan-based built-in self-test environment. However, like other scan-based methods, the LFSR based pattern generation schemes take a long test application time to feed deterministic patterns from the LFSR into a scan chain. In this paper we derive a general relationship between the bits in the scan chain and the states of the LFSR and show that any bit to be generated by an LFSR in any future clock cycle can be pre-generated by a linear function of the current LFSR state. With this relationship, we can divide a scan chain into multiple sub-chains and use one LFSR-based multiple sequence generator to simultaneously generate all the subsequences required by the sub-chains, hence can greatly reduce the test application time for deterministic patterns. Moreover, due to the scan time reduction, test power wasted during the scan operation can also be significantly reduced.

NONLINEAR CONTROLLER DESIGN BASED ON OPTIMAL MATRIX ASSIGNMENT

Matrix assignment of linear control design is extended to nonlinear control. Linear and nonlinear controllers based on higher powers in the state variable are used for solving this optimization problem. The method presented addresses a scanning operation in the state-space region under consideration and minimizes the maximum deviation to the linear control design target. In addition, emphasis is put on Lyapunov conditions for stability and on controller norm restrictions.

Reduction of power consumption in scan-based circuits during test application by an input control technique

This paper proposes a novel technique to minimize the switching activity of full-scan circuits during test application time. The basic idea is to identify an input control pattern (CP) for a full-scan circuit such that by applying the pattern to the primary inputs of the circuit during the scan operation, the switching activity in the combinational part can be reduced or even eliminated. A D-algorithm-like CP generator is developed to generate the CP. This input control technique can be utilized together with the existing vector ordering or latch ordering techniques. Experimental results show that the vector ordering and the latch ordering techniques can achieve 22.37% of average improvement by redoing the experiments in previous work using our test sets, while 34.23% average improvement can be achieved if the input control technique is employed after the latch ordering and vector ordering techniques.

Simulation study and experiment on laser-ablation surface cleaning

A study of the ablation effects of an ultra-short pulsed Nd : YAG laser was carried out. Using a 21 μm Zn-coated carbon steel plate as the target, the relationship between ablation rate and laser fluence was investigated through computer simulation and experiment, and the optimal processing conditions were determined. The tendency of the scanning operation curve was confirmed and the data obtained were taken as a guide for the practical utilization of this technique. Finally, a decontamination factor was introduced and satisfactory cleaning was obtained.

A Framework for Laser Scan Planning of Freeform Surfaces

This paper proposes a framework that can be used for automatic planning of the laser scanning operation. Highly complex and freeform shaped parts are used in industry more and more; however, it is difficult to capture the part accurately in a short time using a conventional measuring machine. The technology of the laser scanner has been developed greatly and this machine can now meet the requirements. There are few planning systems, however, that can support the scanning operation. The planning system proposed in this paper considers various system parameters, such as depth of field, view angle, and length of laser stripe, to develop an accurate measuring plan. The algorithms in the planning system consist of two steps, estimation of the initial scan plan and a feedback routine that checks for the scanning constraints and generates the final scan plan. The developed algorithms were verified by examining a part with Bezier surfaces.

Fiber-optic confocal microscopy using a spatial light modulator

We present a novel fiber-optic confocal microscope in which the scanning operation is achieved by use of a spatial light modulator (SLM) to sequentially illuminate individual fibers or patterns of multiple fibers. Experimental images are presented, and the optical-sectioning capability of the device is demonstrated. The novel SLM-based system is more optically efficient, achieves higher contrast, and has improved optical-sectioning capabilities compared with those of other proposed instruments for confocal microendoscopy.

N-Dodecane melting studied by the combined use of different calorimetric modes

The solid–liquid phase transition of n-dodecane has been studied with a modulated adiabatic scanning calorimeter (MASC). The well-known features of melting — such as the existence of a pre-melting region and the dependence of the melting curve on the scanning rate — were observed, together with completely new features which, to the best of our knowledge, have never been reported before, such as the presence of a small secondary, non-reproducible peak in the melting curve. This last result was obtained working in the scanning operation mode, at rates lower than 3.3×10 −4 K s −1. The complex melting process occurring in the sample was studied inside the melting temperature interval, using the temperature step scanning and the adiabatic-like enthalpy step operation mode of MASC. A very slow rate of attainment of equilibrium was observed when the liquid and solid phases were co-existing. Temperature modulation, in both the continuous scanning mode and the quasi-isothermal step-scanning mode, was also used to obtain a clearer characterisation of the melting kinetics. The melting transition of n-dodecane is discussed in the light of the results obtained by applying to one and the same sample different operation modes. The transition enthalpy values measured are compared to the data in the literature. The two peaks observed in the melting curve of n-dodecane are analysed and possible explanations for the second peak are discussed.

Theoretical demonstration of beam scanning and switching using spatial solitons in a photorefractive crystal

The operation of photorefractive scanning and switching devices is investigated both analytically and numerically. It is based upon the time dependent interaction of two (1D + 1) solitary beams in a photorefractive crystal. The applications are supported by a numerical demonstration and an analytical model obtained with a split-field approach.

Algebraic PET image reconstruction with pre-computed reconstruction operators using subsets of sensitivity functions

Algebraic reconstruction methods have been successfully used to improve quality of positron emission tomography (PET) images by accurate modeling of measurement system, but they have computational burden. The authors propose a fast PET image reconstruction method based on an algebraic technique. In this method, reconstruction operators are pre-computed approximately using subsets of sensitivity functions. The subsets contain the sensitivity functions that contribute significantly to each point to be reconstructed. The proposed method was applied to simulated data and experimental data for the ECAT EXACT HR+ (Siemens/CTI) scanner operating in 2D mode. These results show that the proposed method produces images with almost the same quality as the conventional algebraic methods do and has a similar computation time to the filtered backprojection method.

Automated inspection planning of free-form shape parts by laser scanning

The inspection operation accounts for a large portion of manufacturing lead time, and its importance in quality control cannot be overemphasized. In recent years, due to the development of laser technology, the accuracy of laser scanners has been improved significantly so that they can be used in a production environment. They are noncontact-type-measuring devices and usually have the scanning speed that is 50–100 times faster than that of coordinate measuring machines. This laser-scanning technology provides us a platform that enables us to perform a 100% inspection of complicated shape parts. This research proposes algorithms that lead to the automation of laser scanner-based inspection operations. The proposed algorithms consist of three steps: firstly, all possible accessible directions at each sampled point on a part surface are generated considering constraints existing in a laser scanning operation. The constraints include satisfying the view angle, the depth of view, checking interference with a part, and avoiding collision with the probe. Secondly, the number of scans and the most desired direction for each scan are calculated. Finally, the scan path that gives the minimum scan time is generated. The proposed algorithms are applied to sample parts and the results are discussed.

Quality assurance for MRI: practical experience.

The aim of this study is to propose guidelines for quality assurance (QA) in MRI, based on a comprehensive assessment of QA parameters undertaken on a busy clinical MRI scanner over the course of 1 year. QA phantoms supplied by the scanner manufacturer were used together with the Eurospin MRI phantom set. Signal-to-noise ratio (SNR) and image uniformity were measured daily from spin echo images acquired using a quadrature send-receive head coil and from a gradient echo sequence using the Helmholtz body coil. The voltage of the transmit radiofrequency (RF) amplifier was noted. Monthly measurements of slice thickness, geometric distortion, slice position, image resolution and image ghosting were acquired using the head coil. In addition, SNR was measured monthly on a selection of commonly used coils. Apart from some drift of the RF amplifier voltage, all measurements were within acceptable limits and were stable over the course of 1 year. Satisfactory measurements of SNR were possible using the simple phantom supplied with the scanner. The SNR, geometric distortion and RF amplifier voltage are simple to determine and can be measured in less than 15 min by the scanner operator, using the scanner software. Weekly recording of these parameters is recommended for busy clinical MRI scanners, as this should allow deviations from acceptable limits to be identified early. Such in-house checks can usefully be compared with the less frequent estimations performed by the service engineer. Comprehensive QA routines are discussed for systems used for quantitative measurements.

InP-based photonic micro-sensor for near field optical investigations

This article describes the fabrication process for an InP-based atomic force microscopy (AFM)-type cantilever that is equipped with a micro-photonic sensor. This cantilever, intended to be associated with a diamond supertip, will make it possible to obtain synchronous AFM and near field optical (NFO) images in a scanning operation. The mechanical, electrical and optical performance of the photonic sensor is detailed. This photonic sensor was successfully used as a photodetector. It is possible to integrate the system into a hybrid data processing circuit. Such a cantilever could be used simultaneously in the NFO mode and in AFM operations.

Efficient support for interactive scanning operations in MPEG-based video-on-demand systems

In this paper, we present an efficient approachfor supporting fast-scanning (FS) operations in MPEG-based video-on-demand (VOD) systems. This approach is based onstoring multiple, differently encoded versions of the samemovie at the server. A normal version is used for normalplayback, while several scan versions are used for FS. Eachscan version supports forward and backward FS at a givenspeedup. The server responds to an FS request by switching from the normal version to an appropriate scan version.Scanning versions are produced by encoding a sample of theraw frames using the same GOP pattern of the normal version. When a scanning version is decoded and played back atthe normal frame rate, it gives a perceptual motion speedup.By being able to control the traffic envelopes of the scanversions, our approach can be integrated into a previouslyproposed framework for distributing archived, MPEG-coded video streams. FS operations are supported using no or littleextra network bandwidth beyond what is already allocatedfor normal playback. Mechanisms for controlling the trafficenvelopes of the scan versions are presented. The actionstaken by the server and the client's decoder in response tovarious types of interactive requests are described in detail.The latency incurred in implementing various interactive requests is shown to be within an acceptable range. Stripingand disk-scheduling strategies for storing various versions atthe server are presented. Issues related to the implementationof our approach are discussed.