Wen. Chen

Publications (5)5.25 Total impact

• Article: Fourth International Conference on Experimental Mechanics

  Wen Chen, Chenggen Quan, Cho Jui Tay
  [show abstract] [hide abstract]
  ABSTRACT: In this paper, we propose a method for optical image encryption based on fractional Fourier transform (FRFT) and Arnold transform (ART) in phase-shifting digital holography. An input image is first divided into eight bit planes, and each bit plane is encrypted based on double random-phase masks and FRFT. Complex amplitude for the object is retrieved by phase-shifting digital holography in the hologram plane. The real and imaginary parts of the retrieved complex amplitudes for the 0th-7th bit planes are further encrypted using ART algorithm. Numerical results are shown to demonstrate the feasibility and effectiveness of the proposed technique. The sensitivity of security parameters, such as function orders in FRFT and iteration number in ART method, is also analyzed.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
  12/2009;
• Article: Extended depth of focus in a particle field measurement using a single-shot digital hologram

  Wen Chen, Chenggen Quan, Cho Jui Tay
  [show abstract] [hide abstract]
  ABSTRACT: We propose a method to extend the depth of focus in a particle field measurement using a single-shot digital hologram. A focal plane is obtained for each pixel based on an entropy method, and a depth map is subsequently extracted. A synthesized extended focused image is determined correspondingly using the extracted depth map. In addition, a wavelet modulus maxima algorithm and Canny algorithm are further employed to detect the edges of each particle, and the sizes and a three-dimensional localization of the particles are also estimated. Preliminary results are presented to show the feasibility and effectiveness of the proposed technique.
  Applied Physics Letters 11/2009; 95(20):201103-201103-3. · 3.84 Impact Factor
• Article: Measurement of curvature and twist of a deformed object using digital holography.

  Wen Chen, Chenggen Quan, Cho Jui Tay
  [show abstract] [hide abstract]
  ABSTRACT: Measurement of curvature and twist is an important aspect in the study of object deformation. In recent years, several methods have been proposed to determine curvature and twist of a deformed object using digital shearography. Here we propose a novel method to determine the curvature and twist of a deformed object using digital holography and a complex phasor. A sine/cosine transformation method and two-dimensional short time Fourier transform are proposed subsequently to process the wrapped phase maps. It is shown that high-quality phase maps corresponding to curvature and twist can be obtained. An experiment is conducted to demonstrate the validity of the proposed method.
  Applied Optics 06/2008; 47(15):2874-81. · 1.41 Impact Factor
• Source

  Available from: ntu.edu.sg

  Article: Color image encryption based on interference and virtual optics.

  Cho Jui Tay, Chenggen Quan, Wen. Chen, Yu. Fu
  [show abstract] [hide abstract]
  ABSTRACT: We propose two approaches to encrypt color images based on interference and virtual optics. In the first method, a color image is first decomposed into three independent channels, i.e., red, green and blue.Each channel of the input image is encrypted into two random phase-only masks based on interference.In the second method, a color image is first converted into an image matrix and a color map, and only the image matrix is encrypted into random-phase masks based on interference. After the phase masks are retrieved, a concept based on virtual optics is further applied to enhance the security level. Numerical simulations are demonstrated to show the feasibility and effectiveness of the proposed methods. Accepted version
• Source

  Available from: ntu.edu.sg

  Article: Quantitative detection and compensation of phase-shifting error in two-step phase-shifting digital holography.

  Wen. Chen, Chenggen Quan, Cho Jui Tay, Yu. Fu
  [show abstract] [hide abstract]
  ABSTRACT: Phase-shifting digital holographic technique is a powerful tool for the measurement of various physical parameters, such as object deformation and liquid or cell’s refractive index change. However, for an accurate measurement, phase-shifting error in the reference wave path is still a major issue. In this paper, three novel and simple algorithms are proposed to quantitatively detect and correct phase-shifting error for a pure phase object in two-step phase-shifting digital holography. Influence of phase-shifting error is illustrated, and the effectiveness of the proposed algorithms is demonstrated by numerical simulation results. Accepted version