ASM Pacific Technology Ltd.

Kwai, Hong Kong

ASM Pacific Technology Ltd.

Kwai, Hong Kong

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Yuan J.,Hong Kong University of Science and Technology | Fung S.W.,Technology Research Institute Co. | Chan K.Y.,ASM Pacific Technology Ltd. | Xu R.,Hong Kong University of Science and Technology
IEEE Transactions on Instrumentation and Measurement | Year: 2012

The linearity of a pipeline analog-to-digital converter (ADC) is mainly limited by capacitor mismatch and finite operational amplifier (OPAMP) gain, which cause large power and design difficulty in modern nanometer CMOS processes for high-resolution pipeline ADCs. It is a trend of developing digital calibration techniques to compensate the analog error in pipeline stages. This paper systematically introduces a novel interpolation-based digital calibration architecture to compensate both linear and nonlinear errors from pipeline stages. The new method does not require convergence. The effect of calibration error is analyzed in detail in this paper. A prototype 20-MS/s pipeline ADC is fabricated in a 0.35-μm 3.3-V CMOS process. For 12-b resolution, the digital calibration improves the ADC differential nonlinearity and integral nonlinearity from 1.47 LSB and 7.85 LSB to 0.2 LSB and 0.27 LSB. For a 590-kHz sinusoidal signal, the calibration improves the ADC signal-to-noise-distortion ratio and spurious-free dynamic range from 41.3 dB and 52.1 dB to 72.5 dB and 84.4 dB, respectively. With the new calibration technique, low-gain OPAMPs and small capacitors are used in the pipeline. The designed ADC has 0.78-pJ/step figure of merit (FOM), which is among the lowest reported FOMs for high-resolution pipeline ADC designs. The new architecture requires an accurate calibration ADC (CalADC) and two digital decoders. CalADC is implemented on-chip with 6.5% die area and 8.9% power. The decoders are synthesized to have 912 gates and consume 23.4% ADC power. © 2011 IEEE.


Bai T.,ASM Pacific Technology Ltd | Li Y.,City University of Hong Kong | Zhou X.,Zhejiang University of Technology
Advanced Robotics | Year: 2014

In this work, we address the problem of monocular tracking the human motion based on the discriminative sparse representation. The proposed method jointly trains the dictionary and the discriminative linear classifier to separate the human being from the background. We show that using the online dictionary learning, the tracking algorithm can adapt the variation of human appearance and background environment. We compared the proposed method with four state-of-the-art tracking algorithms on eight benchmark video clips (Faceocc, Sylv, David, Singer, Girl, Ballet, OneLeaveShopReenter2cor, and ThreePastShop2cor). Qualitative and quantitative experimental validation results are discussed at length. The proposed algorithm for human tracking achieves superior tracking results, and a Matlab run time on a standard desktop machine of four frames per second. © 2014 Taylor & Francis and The Robotics Society of Japan.


Deng F.,University of Hong Kong | Deng F.,ASM Pacific Technology Ltd | Liu C.,ASM Pacific Technology Ltd | Sze W.,ASM Pacific Technology Ltd | And 4 more authors.
Optical Engineering | Year: 2012

Uneven illumination is a common problem in practical optical systems designed for machine vision applications, and it leads to significant errors when phase-shifting algorithms (PSA) are used to reconstruct the surface of a moving object. We propose an illumination-reflectivityfocus model to characterize this uneven illumination effect on phase-measuring profilometry. With this model, we separate the illumination factor effectively and consider the phase reconstruction from an optimization perspective. Furthermore, we formulate an illumination-invariant phaseshifting algorithm (II-PSA) to reconstruct the surface of a moving object under an uneven illumination environment. Experimental results show that it can improve the reconstruction quality both visually and numerically. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).


Deng F.,University of Hong Kong | Deng F.,ASM Pacific Technology Ltd | Liu C.,ASM Pacific Technology Ltd | Sze W.,ASM Pacific Technology Ltd | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The perspective effect is common in real optical systems using projected patterns for machine vision applications. In the past, the frequencies of these sinusoidal patterns are assumed to be uniform at different heights when reconstructing moving objects. Therefore, the error caused by a perspective projection system becomes pronounced in phase-measuring profilometry, especially for some high precision metrology applications such as measuring the surfaces of the semiconductor components at micrometer level. In this work, we investigate the perspective effect on phase-measuring profilometry when reconstructing the surfaces of moving objects. Using a polynomial to approximate the phase distribution under a perspective projection system, which we call a polynomial phase-measuring profilometry (P-PMP) model, we are able to generalize the phase-measuring profilometry model discussed in our previous work and solve the phase reconstruction problem effectively. Furthermore, we can characterize how the frequency of the projected pattern changes according to the height variations and how the phase of the projected pattern distributes in the measuring space. We also propose a polynomial phase-shift algorithm (P-PSA) to correct the phase-shift error due to perspective effect during phase reconstruction. Simulation experiments show that the proposed method can improve the reconstruction quality both visually and numerically. © 2013 SPIE-IS&T.


Zhou X.,City University of Hong Kong | Li Y.F.,City University of Hong Kong | He B.,Fuzhou University | Bai T.,ASM Pacific Technology Ltd.
IEEE International Conference on Intelligent Robots and Systems | Year: 2013

Tracking multiple moving targets in video is still a challenge because of mutual occlusion problem. This paper presents a Gaussian mixture probability hypothesis density-based visual tracking system with game theory-based mutual occlusion handling. First, a two-step occlusion reasoning algorithm is proposed to determine the occlusion region. Then, the spatial constraint-based appearance model with other interacting targets¶ interferences is modeled. Finally, an n-person, non-zero-sum, non-cooperative game is constructed to handle the mutual occlusion problem. The individual measurements within the occlusion region are regarded as the players in the constructed game competing for the maximum utilities by using the certain strategies. The Nash Equilibrium of the game is the optimal estimation of the locations of the players within the occlusion region. Experiments conducted on publicly available videos demonstrate the good performance of the proposed occlusion handling algorithm. © 2013 IEEE.


PubMed | ASM Pacific Technology Ltd, University of Hong Kong and Shenzhen University
Type: | Journal: Scientific reports | Year: 2016

The control for the processing of precursor liquids determines whether the properties and functions of the final material product can be engineered. An inherent challenge of processing viscous liquids arises from their large resistance to deform. Here, we report on the discovery of an electric approach that can significantly contribute to address this challenge. The applied electric force can induce a straight viscous jet to coil, and the resulting coiling characteristics are governed by the electric stress. We demonstrate the promising use of electrical coiling in the rapid and efficient mixing of viscous liquids. Remarkably, the degree of mixing can be precisely adjusted by tuning the applied electric stress. Our approach of controlling the coiling electrically has important implications on applications such as dispensing and printing of resins, printing patterned surfaces and scaffolds, processing of food and generating non-woven fabrics.


Chan F.Y.M.,ASM Pacific Technology Ltd. | Mudhana G.,Vellore Institute of Technology
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2014

We investigate how the index profile of a few-mode fiber (FMF) can be designed so that group velocities of the two lowest-order modes can be equalized at a normalized frequency, which is below the cut-off frequency of the LP 21 mode. This can be achieved using a single-clad power-law profile with a sufficiently large profile exponent or a double-clad profile consisting of a graded-core surrounded by a sufficiently thick depressed inner cladding without index jump at their interface. The fabrication tolerances, effective index differences, intramodal dispersion differences, and effective mode areas of various single- and double-clad profiles are compared. The results show that, in comparison to single-clad fibers, double-clad fibers are capable of producing higher fabrication tolerances and reduced sensitivity of group delay difference to wavelength by three and two orders of magnitude, respectively. Our analyses provide insights into the design of FMFs, which will facilitate future development of highcapacity mode division long-haul transmission systems. © 2014 Optical Society of America.


Bai T.,ASM Pacific Technology Ltd | Li Y.,City University of Hong Kong
IEEE Transactions on Industrial Informatics | Year: 2014

In this work, we propose a robust and flexible appearance model based on the structured sparse representation framework. In our method, we model the complex nonlinear appearance manifold and the occlusion as a sparse linear combination of structured union of subspaces in a basis library, which consists of multiple incremental learned target subspaces and a partitioned occlusion template set. In order to enhance the discriminative power of the model, a number of clustered background subspaces are also added into the basis library and updated during tracking. With the Block Orthogonal Matching Pursuit (BOMP) algorithm, we show that the new flexible structured sparse representation based appearance model facilitates the tracking performance compared with the prototype structured sparse representation model and other state of the art tracking algorithms. © 2005-2012 IEEE.


Chan F.Y.M.,ASM Pacific Technology Ltd. | Mudhana G.,Vellore Institute of Technology | Shum P.,Nanyang Technological University
Applied Optics | Year: 2015

We present a comparative study of the bandwidth and the sensitivity of the resonance wavelength of long-period gratings (LPGs) to external perturbation fabricated in single-mode fibers (SMFs) and few-mode fibers (FMFs), and their dependencies on the group indices and the dispersion properties of the phase-matched modes. Unlike SMFs, a relatively large core size of FMFs invariably leads to nonuniform index modulation across the fiber cross section under UV exposure, enabling the coupling between modes having dissimilar azimuthal symmetry. Simple analytical formulas for the group/effective index difference, dispersion difference, bandwidth, and wavelength sensitivities are derived for the case of SMFs where light is coupled from the fundamental core mode to the symmetrical cladding modes. Our results show that a two-mode fiber operating at a V -number close to 3 is capable of producing LPGs with broader bandwidth and higher sensitivity as compared with their SMF counterparts, except for a few special cases. Our analyses provide insights into the characteristics of LPGs and facilitate their designs for specific applications. © 2015 Optical Society of America.


Bai T.,ASM Pacific Technology Ltd. | Li Y.F.,City University of Hong Kong | Shao Z.,City University of Hong Kong
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2013

This paper presents a novel algorithm for robust visual object tracking based on the structured sparse representation framework. Conventional structured sparse representation based tracker models the nonlinear appearance manifold with a single subspace that is difficult to handle significant pose and illumination changes. Different from the afore-mentioned method, the proposed algorithm approximates the nonlinear appearance manifold by multiple low dimensional subspaces computed by an incremental learning scheme based on the merging and insert strategy. In order to enhance the discriminative power of the model, a number of clustered background subspaces are also added into the basis library and updated during tracking. With the Block Orthogonal Matching Pursuit (BOMP) algorithm, we show that the complex nonlinear appearance manifold can effectively represent by a sparse linear combination of structured union of subspaces. Experiments on benchmark video sequences show that the new structured sparse representation model improves the robustness of tracking. © 2013 IEEE.

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