Improving an interactive simulator for computer systems with learning objects

In the 21st century, learning is a crucial activity through which people can assimilate or acquire new knowledge. However, many existing e-Iearning systems contain complicated knowledge structure that hinders the reuse or sharing of knowledge. In a previous project awarded by the Microsoft Research Asia, we successfully developed an interactive simulator to facilitate the learning of essential concepts related to computer systems through live animations. Here, we propose to integrate learning objects and relevant technologies into our interactive simulator to illustrate the underlying knowledge structure and, more importantly, facilitate the sharing and reuse of relevant concepts. Through adopting the IEEE learning object metadata (LOM) standard, our simulator can easily exchange relevant learning objects with other e-Iearning systems. The system design and prototype implementation of our LOM-based simulator is considered in this paper to evaluate how general and experienced users can benefit from our LOM-based simulator in various ways. © 2010 IEEE.published_or_final_versionThe 2nd International Conference on Education Technology and Computer (ICETC 2010), Shanghai, China, 22-24 June 2010. In Proceedings of the International Conference on Education Technology and Computer, 2010, v. 3, p. 16-2

Applying an evolutionary approach for learning path optimization in the next-generation e-learning systems

Learning analytics is targeted to better understand and optimize the process of learning and its environments through the measurement, collection and analysis of learners' data and contexts. To advise people's learning in a specific subject, most intelligent e-learning systems would require course instructors to explicitly input some prior knowledge about the subject such as all the pre-requisite requirements between course modules. Yet human experts may sometimes have conflicting views leading to less desirable learning outcomes. In a previous study, we proposed a complete system framework of learning analytics to perform an explicit semantic analysis on the course materials, followed by a heuristic-based concept clustering algorithm to group relevant concepts before finding their relationship measures, and lastly employing a simple yet efficient evolutionary approach to return the optimal learning sequence. In this paper, we carefully consider to enhance the original evolutionary optimizer with the hill-climbing heuristic, and also critically evaluate the impacts of various experts' recommended learning sequences possibly with conflicting views to optimize the learning paths for the next-generation e-learning systems. More importantly, the integration of heuristics can make our proposed framework more self-adaptive to less structured knowledge domains with conflicting views. To demonstrate the feasibility of our prototype, we implemented a prototype of the proposed e-learning system framework for learning analytics. Our empirical evaluation clearly revealed many possible advantages of our proposal with interesting directions for future investigation. © 2013 IEEE.published_or_final_versio

Bit-pairing codification for binary pattern projection system

In a previous work, we proposed a new binary-light projection mechanism that had a much reduced system size that made it particularly suitable for 3D shape inspection of semiconductor products. The inspection speed of the mechanism was governed by the number of required images which also equaled the number of shiftings of the grating. In this paper we address how inspection speed could be gained, i.e., how the number of required images could be reduced, by the incorporation of two neighboring bits in the codification of each scene element. We provide an optimal design of such a codification strategy. A solution to the shifting strategy optimization is also proposed that is applicable to any given binary patterns. Theoretical analysis and real image experiments are presented to illustrate the workability of the solutions. © 2006 IEEE.published_or_final_versio

A three-dimensional imaging system for surface profilometry of moving objects

Non-contact optical imaging system design and the corresponding surface profilometry algorithm are critical components in various metrology applications, such as surface inspection of semiconductor components on the production line. For such challenging industrial applications, the most important considerations are often automation, precision and speed of the inspection. In this work, we propose a mathematical framework and a dynamic phase-shift algorithm (D-PSA) for a dense surface profilometry of moving objects. We also present a fringe pattern projection system with projector and camera arrays, with an aim to reduce the undesirable effects such as the uneven illumination and the perspective geometry effect on the reconstructed surface using a large field-of-view inspection system. This system is then applied to the inspection of the surface of moving printed circuit boards along a conveyor belt. Experimental results show that our approach can reconstruct the object surface effectively and efficiently. © 2013 IEEE.published_or_final_versio

Reference-free detection of semiconductor assembly defect

This paper aims at developing a novel defect detection algorithm for the semiconductor assembly process by image analysis of a single captured image, without reference to another image during inspection. The integrated circuit (IC) pattern is usually periodic and regular. Therefore, we can implement a classification scheme whereby the regular pattern in the die image is classified as the acceptable circuit pattern and the die defect can be modeled as irregularity on the image. The detection of irregularity in image is thus equivalent to the detection of die defect. We propose a method where the defect detection algorithm first segments the die image into different regions according to the circuit pattern by a set of morphological segmentations with different structuring element sizes. Then, a feature vector, which consists of many image attributes, is calculated for each segmented region. Lastly, the defective region is extracted by the feature vector classification. © 2005 SPIE and IS&T.published_or_final_versio

Regularized multiframe phase-shifting algorithm for three-dimensional profilometry

In many industrial inspection systems, it is required to have a high-precision three-dimensional measurement of an object under test. A popular technique is phase-measuring profilometry. In this paper, we develop some phase-shifting algorithms (PSAs). We propose a novel smoothness constraint in a regularization framework; we call this the R-PSA method and show how to obtain the desired phase measure with an iterative procedure. Both the simulation and experimental results verify the efficacy of our algorithm compared with current multiframe PSAs for interferometric measurements.published_or_final_versio

Three-dimensional reconstruction of wafer solder bumps using binary pattern projection

As the electronic industry advances rapidly, the shrunk dimension of the device leads to more stringent requirement on process control and quality assurance. For instance, the tiny size of the solder bumps grown on wafers for direct die-to-die bonding pose great challenge to the inspection of the bumps' 3D quality. Traditional pattern projection method of recovering 3D is about projecting a light pattern to the inspected surface and imaging the illuminated surface from one or more points of view. However, image saturation and the specular nature of the bump surface are issues. This paper proposes a new 3D reconstruction mechanism for inspecting the surface of such wafer bumps. It is still based upon the light pattern projection framework, but uses the Ronchi pattern - a pattern that contrasts with the traditionally used gray level one. With the use of a parallel or point light source in combination with a binary grating, it allows a discrete pattern to be projected onto the inspected surface. As the projected pattern is binary, the image information is binary as well. With such a bright-or-dark world for each image position, the above-mentioned difficult issues are avoided. Preliminary study shows that the mechanism holds promises that existing approaches do not. © 2005 SPIE and IS&T.published_or_final_versio

Structured-light based sensing using a single fixed fringe grating: Fringe boundary detection and 3-D reconstruction

Advanced electronic manufacturing requires the 3-D inspection of very small surfaces like the solder bumps on wafers for direct die-to-die bonding. Yet the microscopic size and highly specular and textureless nature of the surfaces make the task difficult. It is also demanded that the size of the entire inspection system be small so as to minimize restraint on the operation of the various moving parts involved in the manufacturing process. In this paper, we describe a new 3-D reconstruction mechanism for the task. The mechanism is based upon the well-known concept of structured-light projection, but adapted to a new configuration that owns a particularly small system size and operates in a different manner. Unlike the traditional mechanisms which involve an array of light sources that occupy a rather extended physical space, the proposed mechanism consists of only a single light source plus a binary grating for projecting binary pattern. To allow the projection at each position of the inspected surface to vary and form distinct binary code, the binary grating is shifted in space. In every shift, a separate image of the illuminated surface is taken. With the use of pattern projection, and of discrete coding instead of analog coding in the projection, issues like texture-absence, image saturation, and image noise of the inspected surfaces are much lessened. Experimental results on a variety of objects are presented to illustrate the effectiveness of this mechanism. © 2008 IEEE.published_or_final_versio

An illumination-invariant phase-shifting algorithm for three-dimensional profilometry

Image Processing: Machine Vision Applications V, Burlingame, California, USA, 22 January, 2012Uneven illumination is a common problem in real optical systems for machine vision applications, and it contributes significant errors when using phase-shifting algorithms (PSA) to reconstruct the surface of a moving object. Here, we propose an illumination-reflectivity-focus (IRF) model to characterize this uneven illumination effect on phase-measuring profilometry. With this model, we separate the illumination factor effectively, and then formulate the phase reconstruction as an optimization problem. To simplify the optimization process, we calibrate the uneven illumination distribution beforehand, and then use the calibrated illumination information during surface profilometry. After calibration, the degrees of freedom are reduced. Accordingly, we develop a novel illumination-invariant phase-shifting algorithm (II-PSA) to reconstruct the surface of a moving object under an uneven illumination environment. Experimental results show that the proposed algorithm can improve the reconstruction quality both visually and numerically. Therefore, using this IRF model and the corresponding II-PSA, not only can we handle uneven illumination in a real optical system with a large field of view (FOV), but we also develop a robust and efficient method for reconstructing the surface of a moving object. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).link_to_subscribed_fulltextpublished_or_final_versio

Projection optics design for tilted projection of fringe patterns

A challenge in the semiconductor industry is 3-D inspection of the miniaturized solder bumps grown on wafers for direct die-to-die bonding. An inspection mechanism proposed earlier requires the projection of a binary fringe grating to the inspected surface from an inclined angle. For high speed and accuracy of the mechanism, the projection optics has to meet these requirements: (1) it allows a tilt angle between the inspected surface and the projector's optical axis; (2) it has a high bandwidth to let high-spatial-frequency harmonics contained in the binary grating pass through the lens and be projected onto the inspected surface properly; (3) it has a high modulation transfer function; (4) it has a large field of view; and (5) it has an adequate depth of field that matches the depth range of the inspected surface. In this paper, we describe a projection optics design, consisting of a fringe grating and several pieces of spherical lens, that addresses the requirements. To reduce the lens aberrations, the grating is laid out with an angle chosen specifically to make the grating, the lens, and the average plane of the inspected surface intersect in the same line. Performance analysis and tolerance analysis are shown to demonstrate the feasibility of the design. © 2008 Society of Photo-Optical Instrumentation Engineers.published_or_final_versio