Quality Control In Production Line Research Articles

Multi-view fringe projection profilometry for surfaces with intricate structures and high dynamic range

Fringe projection profilometry plays an important role for quality control in production line. However, it is facing challenges in the measurement of objects with intricate structures and high dynamic range that involved in precision manufacturing and semiconductor packaging. In this paper, a multi-view fringe projection profilometry system, which deploys a vertical telecentric projector and four oblique tilt-shift cameras, is presented to address the “blind spots” caused by shadowing, occlusion and local specular reflection. A flexible and accurate system calibration method is proposed, in which the corrected pinhole imaging model is used to calibrate the telecentric projection, and the unified calibration is performed by bundle adjustment. Experimental results show that the 3D repeated measurement error and standard deviation are no more than 10 μm within a measurable volume of 70 × 40 × 20 mm3. Furthermore, a group of experiments prove that the developed system can achieve complete and accurate 3D measurement for high dynamic range surfaces with complex structures.

Forward Stimulated Brillouin Scattering Analysis of Optical Fibers Coatings

The proper function of protective coating layers is essential for the handling and application of brittle optical fibers. The elastic parameters of polymer coatings can be studied through off-line analysis of test samples. However, the monitoring of these properties on a working fiber during service is challenging. In this work, we use forward stimulated Brillouin scattering processes in standard single mode fibers to measure the acoustic velocity in several types of coating layers. Pump light launches short acoustic pulses outward from the core of the fiber. Multiple reflections at the boundaries between cladding and coating, and between coating and air, form a series of delayed acoustic echoes across the core. These echoes are monitored, in turn, by photo-elastic phase modulation of probe light. Data are collected at temperatures between 25-120 °C. The thermal dependence of the acoustic velocities in several coatings and of the F-SBS resonance frequencies is investigated. Observations are corroborated by calculations. The proposed technique is well suited for research and development of coating materials, production line quality control, reliability studies and preventive maintenance of working fibers.

Analysis of Phthalate Ester Content in Polyvinylchloride Construction Plastics by RAMAN Spectroscopy

There is serious concern that fat-soluble phthalates such as di (2-ethylhexyl) phthalate, or DEPH. Phthalates are not chemically bonded to the PVC and will with time escape by evaporation or by extraction when in contact with liquids. Raman spectroscopy excited with a 785 nm laser can be used to determine the content of plasticizers in commercial flexible polyvinyl chloride (PVC) construction plastics. This method is very convenient for rapid non-destructive remote determination of phthalates, such as for quality control of production lines, quality control or at customs.

Multivariate Analysis of Transient State Infrared Images in Production Line Quality Control Systems

Manufacturers would like to increase production volumes while preserving the high quality of their products. The long testing times can cause a bottleneck of production processes especially taking into account the observed tendency for testing all produced devices. The main aim of this work consists in the analysis of time changes of features extracted from thermal images using the multivariate approach. The paper shows that if the principal component analysis (PCA), belonging to multivariate methods, is applied for quality control based on infrared images, then the minimum testing times can be estimated. In order to draw the final conclusions regarding testing times and, what is also very important, which principal components should be selected for classification, a detailed temporal analysis for an exemplary production line has been carried out. The future impact of the results includes higher productivity and cost-effectiveness due to the determination of an optimal decision time in production line quality control systems using the proposed approach.

Research on Quality Control of Digital Production Lines in Aviation Enterprises

Focusing on the requirements of efficient quality control of digital production lines in aviation enterprises, the framework quality control system of digital production lines were studied in this paper. First, the quality date categories of digital production lines were sorted out, a multi-source quality data acquisition scheme was proposed,. Second, the importance of key quality characteristics in quality control was discussed as well as a solution to find key quality features was established. Again, a multi-channel statistical quality control framework was constructed and a detailed implementation process was proposed. Finally, a digital production line quality control prototype system was designed and developed and validated in an aviation manufacturing enterprise.

Wavelet analysis of light emission signals in laser beam welding

This paper introduces a compact, robust, and versatile generation of a laser processing head coupled with a single-mode Ytterbium source StarFiber 150 P which not only is used in a wide range of laser material processing applications but also enables in situ and real-time quality control in production lines. In this study, the effect of power density on the weld quality of bead on plate in a SHADOW (Stepless high speed accurate and discrete one pulse welding) welding process was considered. Furthermore, the co-axial back reflected/emitted light from the process zone was measured using three optical sensors; each one measures the light emission in a certain waveband (450–850, 1000–1200, and 1250–1700 nm). From these sensors, the recorded signals were first used as benchmarks to correlate with the weld quality features and defects. Discrete wavelet transform has been used to analyze the signal within the time–frequency domain. The detail signals at different decomposition levels disclosed information with regard to the type (mode) and dynamics of welding process. Accordingly, the deep penetration welding (keyhole) was confidentially distinguished from the shallow (conduction) welding mode. Several defects such as process instabilities (high fluctuations in the keyhole dynamics), formation, and collapse of the keyhole, as well as the lack of penetration, were detected from the corresponding signal signatures. In addition, this information permits us to locate the defect/transition site through the in situ and real-time quality control of the process in production lines. In contrast, porosity and cracks could not be sensed.

Production line quality control using infrared imaging

This paper addresses the problem how to bring advanced data analysis techniques to the reality of a production line in order to increase the productivity and cost-effectiveness while reducing failure rates and increasing reliability of the final product. The main goal was to develop techniques of fast thermal inspection for production line quality control using a knowledge-based machine vision system. The paper contains a description of the system as well as a proposition of the algorithm for automatic classification of devices on the base of information included in their infrared images. Data-driven pattern recognition, infrared imaging, and principal component analysis (PCA) were put together and resulted in a very effective production line quality control system. The algorithm has been validated using real production line data. Experiments revealed some interesting features of the proposed method, e.g. resistance to changes of the ambient temperature and early classification during the thermal transient state.

Introducing measure-by-wire, the systematic use of systems and control theory in transmission electron microscopy

Transmission electron microscopes (TEMs) are the tools of choice for academic and industrial research at the nano-scale. Due to their increasing use for routine, repetitive measurement tasks (e.g., quality control in production lines) there is a clear need for a new generation of high-throughput microscopes designed to autonomously extract information from specimens (e.g., particle size distribution, chemical composition, structural information, etc.). To aid in their development, a new engineering perspective on TEM design, based on principles from systems and control theory, is proposed here: measure-by-wire (not to be confused with remote microscopy). Under this perspective, the TEM operator yields the direct control of the microscope's internal processes to a hierarchy of feedback controllers and high-level supervisors. These make use of dynamical models of the main TEM components together with currently available measurement techniques to automate processes such as defocus correction or specimen displacement. Measure-by-wire is discussed in depth, and its methodology is illustrated through a detailed example: the design of a defocus regulator, a type of feedback controller that is akin to existing autofocus procedures.

Note: A multifunction lens test system for imaging quality evaluation

A novel multifunction lens imaging quality test system is established to overcome the practical problems in the conventional system. This system is compact, cost efficient, user friendly, and suitable for lens quality control in production line. The established system can evaluate the modulation transform function, imaging depth, image distortion, and light intensity distribution of the tested lens by auto-changing the tested patterns. This system consists of a tested lens, a charge coupled device (CCD) camera, a linear motorized stage, a system fixture, an observer liquid crystal display (LCD) monitor, and a notebook for providing patterns. The LCD monitor displays a series of specified tested patterns sent from the notebook. Then each displayed pattern goes through the tested lens and images in the CCD camera. Consequently, the performance of the tested lens can be evaluated by analyzing the image of CCD camera with special designed software. The advantage of this system is that it can complete a whole test quickly without interruption part replacement because the tested patterns are statically displayed on LCD monitor and controlled by the notebook.

EVM measurement of modulation fidelity of π/4 DQPSK baseband modulators

An algorithm for the calculation of optimized error vector magnitude (EVM) and offset vector magnitude (OVM) parameters for m-ary PSK baseband modulators (BMs) is presented. It does not require the regeneration of an ideal reference signal but is based on a mixed time and frequency domain software digital signal processing of a short (256 symbol) random data test signal. The frequency domain processing is required for phase rotation compensation. An automatic test equipment (ATE) implementation of the algorithm as part of an IS-136 π/4 DQPSK baseband modulator IC production line quality control is described, together with some typical measurement results.

Grazing incidence X-ray scattering measurement of silicate glass surfaces

Grazing incidence X-ray scattering measurements have been performed on a series of silicate glass specimens. We show that it is possible to deduce the true roughness using a Born wave approximation (BWA) analysis, provided that the data are corrected for the effects of the diffuse scatter not emerging from the sample surface. The method is valid provided that the lateral correlation length is approximately known and it holds even in the presence of an electron density gradient at the surface. Agreement within experimental error is found with the interface parameters deduced from full simulations of the specular and diffuse scatter using the distorted wave Born approximation (DWBA). We suggest that the analysis may be appropriate for production line quality control of glassy ceramic materials.

Detection of oxygen concentration in silicon wafers using a tunable diode laser

Control of the oxygen concentration in silicon wafers is important for the fabrication of high quality integrated circuits. Techniques for the fast detection of oxygen would be desirable for production line quality control. The oxygen concentration in silicon has traditionally been measured by a Fourier transform infrared spectrometer (FTIS). Due to the slow response time (1-10 min), it is not suitable for wafer screening. In this report, we describe a diode laser spectroscopy technique for the fast (10 ms) detection of oxygen in production line silicon wafers. The results are in good agreement with those measured by the Fourier transform technique.