Chenggen Quan

National University of Singapore, Tumasik, Singapore

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Publications (188)215.63 Total impact

  • Y. Wang · C. Quan · C.J. Tay
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    ABSTRACT: We propose a new asymmetric optical image encryption scheme based on an improved amplitude-phase retrieval algorithm. Using two random phase masks that serve as public encryption keys, an iterative amplitude and phase retrieval process is employed to encode a primary image into a real-valued ciphertext. The private keys generated in the encryption process are used to perform one-way phase modulations. The decryption process is implemented optically using conventional double random phase encoding architecture. Numerical simulations are presented to demonstrate the feasibility and robustness of the proposed system. The results illustrate that the computing efficiency of the proposed method is improved and the number of iterations required is much less than that of the cryptosystem based on the Yang-Gu algorithm.
    No preview · Article · Mar 2016 · Optics and Lasers in Engineering
  • B. Deepan · C. Quan · C.J. Tay
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    ABSTRACT: In this paper, a novel sequential algorithm for the estimation of phase derivatives from a single fringe pattern using electronic speckle pattern interferometry (ESPI) is proposed. The algorithm is based on empirical mode decomposition (EMD), vortex operator (VO) and Teager-Kaiser energy operator (TKEO). The empirical mode decomposition normalizes the fringe pattern; while vortex operator provides a 2D complex image and the phase derivatives are obtained using a novel image demodulation method called discrete higher order image demodulation algorithm (DHODA). Unlike phase shifting and Fourier transform methods, the proposed method does not require complex experimental setup or more than one fringe pattern for each deformation state. The proposed method is also able to provide phase derivatives in both thex andydirections from a single fringe pattern, which is difficult to achieve using shearography. Since the algorithm provides unwrapped phase derivatives directly, it does not require separate phase unwrapping process. Hence it is suitable for dynamic strain and curvature measurement. The proposed algorithm is validated by both simulation and experiment. The results are found to be accurate and the method requires less computation time than existing phase demodulation techniques.
    No preview · Article · Jan 2016 · Optics Communications
  • Y. Wang · C. Quan · C.J. Tay
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    ABSTRACT: Many phase-truncation-based cryptosystems encounter an information disclosure problem. In this paper, a novel color image encryption using a phase-truncated Fresnel transform and random amplitude mask (RAM) without the risk of information disclosure is proposed. An image is first separated into three channels (red, green, and blue) and using an additional RAM channel the risk of information disclosure encountered in previous encryption methods is eliminated. Moreover unlike previous methods where each channel is encrypted independently, the four channels employed in the proposed method are encrypted using a cascading technique. Robustness of the proposed scheme against attacks is analyzed. Numerical simulations are presented to demonstrate the feasibility and effectiveness of the proposed system.
    No preview · Article · Jun 2015 · Optics Communications
  • Y. Wang · C. Quan · C.J. Tay
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    ABSTRACT: A new nonlinear optical image encryption scheme based on a modified amplitude phase retrieval algorithm is proposed. With two random phase masks that serve as the public encryption keys, one iterative amplitude and phase retrieval process is employed to encode the primary image into a stationary white noise. The two private keys generated in the encryption process are randomly distributed binary matrices to be used to perform one-way binary phase modulations. The proposed encryption process is nonlinear and offers enhanced security. Numerical simulations are presented to demonstrate the feasibility and security of the proposed system. The results also illustrate that the computing efficiency of the algorithm is improved and the number of iterations is much less than that of cryptosystem based on Yang-Gu algorithm, which has two iteration processes.
    No preview · Article · Jan 2015 · Proceedings of SPIE - The International Society for Optical Engineering
  • B. Deepan · C. Quan · C.J. Tay
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    ABSTRACT: Phase retrieval techniques like phase-shifting method and Fourier-transform technique provides accurate phase distribution for static measurements. However, it is extremely difficult to use these techniques for dynamic measurement. In this paper, an automated fringe analysis technique to retrieve phase distribution from single fringe pattern is proposed. The proposed method uses Teager-Hilbert-Huang transform, which is based on empirical mode decomposition (EMD), vortex operator (VO) and Teager energy operator (TEO) for fringe demodulation. The proposed method is suitable for both static and dynamic measurements. In this method, a fringe pattern is normalized using EMD and VO generates a complex field of the signal. Finally TEO is used to obtain the phase and its phase derivatives map. Unlike traditional phase retrieval algorithms, this method provides unwrapped phase derivatives directly. Hence there is no need for a separate phase unwrapping process. The proposed method is validated using simulated fringe patterns and experimental data obtained from electronic speckle pattern interferometry (ESPI). The results show that this method determines the phase map and its derivatives from the single fringe pattern effectively.
    No preview · Article · Jan 2015 · Proceedings of SPIE - The International Society for Optical Engineering
  • Y. Wang · C. Quan · C.J. Tay
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    ABSTRACT: We propose a novel nonlinear multiple-image encryption based on mixture retrieval algorithm and phase mask multiplexing in Fresnel domain. The encryption process is realized by applying the Yang–Gu algorithm cascaded with a modified Gerchberg–Saxton algorithm (MGSA), which generate a private key and an intermediate phase to ensure high security. In the proposed method, all images are encoded separately into a phase only function (POF). Obtained POFs are integrated into a final POF based on phase mask multiplexing. As a result, cross-talk noise is removed resulting in a large improvement of the encryption capacity. A spatial light modulator (SLM) based optical setup has been suggested for decryption. Numerical simulations are presented to demonstrate the feasibility and effectiveness of the proposed system. Results also indicate the high robustness of the system against occlusion and noise attacks.
    No preview · Article · Nov 2014 · Optics Communications
  • B. Deepan · C. Quan · Y. Wang · C. J. Tay
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    ABSTRACT: In this paper, a new multiple-image encryption and decryption technique that utilizes the compressive sensing (CS) concept along with a double-random phase encryption (DRPE) has been proposed. The space multiplexing method is employed for integrating multiple-image data. The method, which results in a nonlinear encryption system, is able to overcome the vulnerability of classical DRPE. The CS technique and space multiplexing are able to provide additional key space in the proposed method. A numerical experiment of the proposed method is implemented and the results show that the proposed method has good accuracy and is more robust than classical DRPE. The proposed system is also employed against chosen-plaintext attacks and it is found that the inclusion of compressive sensing enhances robustness against the attacks.
    No preview · Article · Jul 2014 · Applied Optics
  • B. Deepan · C. Quan · C. J. Tay
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    ABSTRACT: Compressive sensing (CS) is one of the latest signal processing techniques, which facilitates to reconstruct a complete signal from a small number of randomly chosen signal samples. It has been shown that CS can be applied successfully in digital holography. In this paper, a novel approach has been suggested for holographic reconstruction using CS technique for determining displacement and its derivative maps. Off-axis lensless Fourier holography configuration is used to capture a digital hologram and only Fourier transform is used for phase retrieval. Hence the Fourier transform is used as a CS operator in the proposed method and NESTA algorithm is used for signal reconstruction. Speckle noise should be filtered from phase maps for phase unwrapping process. Filtering speckle noise for the phase maps with high fringe density is not a better solution because high density fringes will be worn out while filtering. However, the method suggested in this paper is able to produce super resolution displacement and derivative maps using CS, which overcomes the problem due to high density fringes. In super resolution phase maps, the fringe density will be reduced due to increasing in pixel count. Experimental results demonstrate that the proposed method is able to determine super resolution displacement and derivative maps effectively.
    No preview · Conference Paper · Jun 2014
  • C. Quan · D. Balakrishnan · W. Chen · C.J. Tay
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    ABSTRACT: With the advent of CCD camera and the rapid development of computer technology, digital holographic technique has recently attracted much attention from various research fields. This paper presents spatial phase retrieval techniques in digital holography. In the spatial domain, a novel method using the concept of complex phasor is proposed to determine the phase difference map in digital holography. A simple method based on finite difference is also proposed to compute high quality phase derivatives. Based on a deformation phase map obtained by the complex phasor method, slope, curvature and twist maps can be determined. Unwrapped derivative maps can be determined directly from a wrapped phase map without any phase unwrapping process. Simulation and experimental results demonstrate that the proposed method has high measurement accuracy and can effectively determine high resolution phase derivative with less computational effort. It is shown that the proposed techniques can effectively and accurately overcome theoretical and application problems in digital holography.
    No preview · Article · Jan 2014
  • Z. Liu · C. Quan · C. J. Tay
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    ABSTRACT: In the past two decades, fringe projection profilometry (FPP) has been widely used in three-dimensional (3D) profile measurement for its fast speed and high accuracy. As a branch of FPP, color-encoded digital fringe projection profilometry (CDFPP) has been applied to surface profile measurement. CDFPP has the advantage of being fast speed, non-contact and full-field. It is one of the most important dynamic 3D profile measurement techniques. However, due to color cross-talk and gamma distortions of electro-optical devices, phase errors arise in using conventional phase-shifting algorithms to retrieve the phase in CDFPP. Therefore, it is important to develop methods for phase error suppression in CDFPP and thus realizing fast and accurate profile measurement. In this paper, a phase error suppression technique is proposed to overcome color cross-talk and gamma distortions. The proposed method is able to carry out fast and accurate surface profile measurement. The real data experimental results show that the proposed method can effectively suppress phase errors and achieve accurate measurements in CDFPP.
    No preview · Conference Paper · Jun 2013
  • D. Balakrishnan · C. Quan · C. J. Tay
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    ABSTRACT: The phase unwrapping is the final and trickiest step in any phase retrieval technique. Phase unwrapping by artificial intelligence methods (optimization algorithms) such as hybrid genetic algorithm, reverse simulated annealing, particle swarm optimization, minimum cost matching showed better results than conventional phase unwrapping methods. In this paper, Ensemble of hybrid genetic algorithm with parallel populations is proposed to solve the branch-cut phase unwrapping problem. In a single populated hybrid genetic algorithm, the selection, cross-over and mutation operators are applied to obtain new population in every generation. The parameters and choice of operators will affect the performance of the hybrid genetic algorithm. The ensemble of hybrid genetic algorithm will facilitate to have different parameters set and different choice of operators simultaneously. Each population will use different set of parameters and the offspring of each population will compete against the offspring of all other populations, which use different set of parameters. The effectiveness of proposed algorithm is demonstrated by phase unwrapping examples and advantages of the proposed method are discussed.
    No preview · Conference Paper · Jun 2013
  • Source
    Huicong Liu · Bo Woon Soon · Nan Wang · C J Tay · Chenggen Quan · Chengkuo Lee
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    ABSTRACT: A novel electromagnetic energy harvester (EH) with multiple vibration modes has been developed and characterized using three-dimensional (3D) excitation at different frequencies. The device consists of a movable circular-mass patterned with three sets of double-layer aluminum (Al) coils, a circular-ring system incorporating a magnet and a supporting beam. The 3D dynamic behavior and performance analysis of the device shows that the first vibration mode of 1285 Hz is an out-of-plane motion, while the second and third modes of 1470 and 1550 Hz, respectively, are in-plane at angles of 60° (240°) and 150° (330°) to the horizontal (x-) axis. For an excitation acceleration of 1 g, the maximum power density achieved are 0.444, 0.242 and 0.125 µW cm−3 at vibration modes of I, II and III, respectively. The experimental results are in good agreement with the simulation and indicate a good potential in the development of a 3D EH device.
    Full-text · Article · Nov 2012 · Journal of Micromechanics and Microengineering
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    ABSTRACT: Two MEMS-based piezoelectric energy harvesting (EH) systems with wideband operation frequency range and capability of converting random and low-frequency vibrations to high-frequency self-oscillations have been proposed. In the first EH system (EH-I), by incorporating a high-resonant-frequency (HRF) cantilever as a frequency-up-conversion (FUC) stopper, the vibration amplitude of a low-resonant-frequency (LRF) cantilever with a resonant frequency of 36 Hz is suppressed and the operation bandwidth is increased to 22 Hz at 0.8 g. The HRF cantilever is then triggered to vibrate at 618 Hz. In the second EH system (EH-II), by employing a straight cantilever as the FUC stopper, the operation frequency range of a meandered cantilever which responds to lower frequency vibration is further moved downward from 12 Hz to 26 Hz, and the voltage and power generation are significantly improved. The peak-power densities of the EH-II system are 61.5 μW/cm3 and 159.4 μW/cm3 operating at relatively lower operation frequencies of 20 Hz and 25 Hz at 0.8 g, respectively.
    Full-text · Article · Oct 2012 · Sensors and Actuators A Physical
  • S. Ma · C. Quan · R. Zhu · C.J. Tay
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    ABSTRACT: Digital sinusoidal phase-shifting fringe projection profilometry (DSPFPP) is a powerful tool to reconstruct three-dimensional (3D) surface of diffuse objects. However, a highly accurate profile is often hindered by nonlinear response, color crosstalk and imbalance of a pair of digital projector and CCD/CMOS camera. In this paper, several phase error correction methods, such as Look-Up-Table (LUT) compensation, intensity correction, gamma correction, LUT-based hybrid method and blind phase error suppression for gray and color-encoded DSPFPP are described. Experimental results are also demonstrated to evaluate the effectiveness of each method.
    No preview · Article · Aug 2012 · Optics and Lasers in Engineering
  • Suodong Ma · Rihong Zhu · Chenggen Quan · Lei Chen · Cho Jui Tay · Bo Li
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    ABSTRACT: Structured-light profilometry is a powerful tool to reconstruct the three-dimensional (3D) profile of an object. Accurate profile acquisition is often hindered by not only the nonlinear response (i.e., gamma effect) of electronic devices but also the projection-imaging distortion of lens used in the system. In this paper, a flexible 3D profile reconstruction method based on a nonlinear iterative optimization is proposed to correct the errors caused by the lens distortion. It can be easily extended to measurements for which a more complex projection-imaging distortion model is required. Experimental work shows that the root-mean-square (RMS) error is reduced by eight times and highly accurate results with errors of less than 1‰ can be achieved by the proposed method.
    No preview · Article · May 2012 · Applied Optics
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    ABSTRACT: In this paper, a new S-shaped piezoelectric PZT cantilever is microfabricated for scavenging vibration energy at low frequencies (<30 Hz) and low accelerations (<0.4g). The maximum voltage and normalized power are 42 mV and 0.31 μW g −2, respectively, at input acceleration of 0.06g. For acceleration above 0.06g, the vibration of PZT cantilever changes from a linear oscillation to a nonlinear impact oscillation due to the displacement constraint introduced by a mechanical stopper. Based on theoretical modeling and experimental results, the frequency broadening effect of the PZT cantilever is studied with varying stop distances and input accelerations. The operation bandwidth of the piezoelectric PZT cantilever is able to extend from 3.4 to 11.1 Hz as the stop distance reduces from 1.7 to 0.7 mm for an acceleration of 0.3g, at the expense of the voltage and normalized power at resonance decreasing from 40 to 16 mV and from 17.8 to 2.8 nW g−2, respectively.
    No preview · Article · Apr 2012 · Microsystem Technologies
  • S. Ma · R. Zhu · C. Quan · B. Li · C.J. Tay · L. Chen
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    ABSTRACT: Color-encoded digital fringe projection profilometry (CDFPP) has the advantage of fast speed, non-contact and full-field testing. It is one of the most important dynamic three-dimensional (3D) profile measurement techniques. However, due to factors such as color cross-talk and gamma distortion of electro-optical devices, phase errors arise when conventional phase-shifting algorithms with fixed phase shift values are utilized to retrieve phases. In this paper, a simple and effective blind phase error suppression approach based on isotropic n-dimensional fringe pattern normalization (INFPN) and carrier squeezing interferometry (CSI) is proposed. It does not require pre-calibration for the gamma and color-coupling coefficients or the phase shift values. Simulation and experimental works show that our proposed approach is able to effectively suppress phase errors and achieve accurate measurement results in CDFPP.
    No preview · Article · Apr 2012 · Optics Communications
  • S. Ma · C. Quan · R. Zhu · L. Chen · B. Li · C.J. Tay
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    ABSTRACT: In digital fringe projection profilometry, the gamma effect of the used electronic devices seriously affects the accuracy of three-dimensional (3D) topography measurements. Previous gamma correction methods do not take full advantage of the Fourier spectrum of the captured spatial-carrier phase-shifting fringe patterns. Hence, dozens of phase-shifting fringe patterns are required to carry out gamma pre-calibration. In this paper, a fast and accurate gamma correction technique based on a Fourier spectrum analysis is proposed. Only two spatial-carrier fringe patterns with different pre-encoded gamma values are needed and the number of fringe patterns required for gamma pre-calibration is significantly reduced without loss of accuracy. The proposed method is validated by experiments.
    No preview · Article · Mar 2012 · Optics Communications
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    ABSTRACT: This paper presents the design, microfabrication, modeling and characterization of a piezoelectric energy harvester (PEH) system with a wide operating bandwidth introduced by mechanical stoppers. The wideband frequency responses of the PEH system with stoppers on one side and two sides are investigated thoroughly. The experimental results show that the operating bandwidth is broadened to 18 Hz (30–48 Hz) and the corresponding optimal power ranges from 34 to 100 nW at the base acceleration of 0.6g and under top- and bottom-stopper distances of 0.75 mm and 1.1 mm, respectively. By adjusting the mechanical stopper distance, the output power and frequency bandwidth can be optimized accordingly.
    Full-text · Article · Feb 2012 · Smart Materials and Structures
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    ABSTRACT: A piezoelectric energy harvesting cantilever integrated with Si proof mass has been presented to realize a low resonant frequency of 35.8Hz. This paper describes the design, microfabrication and measurement of such device for harvesting energy from low frequency environmental vibrations. Instead of deposition of PZT bulk film, ten PZT thin film patterns (PZT patterns) are parallel arrayed and electrically isolated on the supporting beam of the cantilever. The performance of output voltage and power of PZT patterns in series and in parallel connections are studied based on the experimental and simulation results. It is shown that PZT patterns in series and in parallel connections produce the same level of power in the corresponding matched load resistance, but PZT patterns in parallel connection is preferred because of lower matched load resistance required.
    Preview · Article · Dec 2011 · Physics Procedia