Multiwavelength digital holography with autocalibration of phase shifts and artificial wavelengths.
ABSTRACT A novel implementation of lensless multiwavelength digital holography with autocalibration of temporal phase shifts and artificial wavelength is presented. The algorithm we used to calculate the phase shifts was previously proposed [Opt. Lett.29 183 (2004)] and, to our knowledge, is now used for the first time in lensless holography. Because precise knowledge of the generated artificial wavelength is crucial for absolute measurement accuracy, a simple and efficient method to determine the artificial wavelength directly is presented. The calibration method is based on a simple modification of the experimental setup and needs just one additional image acquisition per wavelength. The results of shape measurement of a metallic test object with a rough surface and steep edges are shown and the measurement accuracy is discussed.
Article: Positioning and localization of two-wavelength interferograms for wavefront reconstruction with volume holographic media.[show abstract] [hide abstract]
ABSTRACT: This work studies both theoretically and experimentally the formation of the contour interference patterns generated by a two-wavelength real-time holographic interferometer. The resulting contour interference fringes are due to the intersection of the measured surface with parallel, equally spaced planes of constant elevation. The theoretical analysis describes how the spatial frequency of the elevation planes, their angular position, and the localization of the fringes depend on parameters of the optical setup. A theoretical model for fringe localization is developed and confirmed by the experiments, showing a strong dependence of the interferogram position on the slope of the studied surface. Due to the thick Bi(12)TiO(20) crystal employed as the storage medium the Bragg selectivity of the holographic readout is also considered.Optics Express 04/2010; 18(9):8743-58. · 3.59 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: This paper presents a novel phase unwrapping architecture for accelerating the computational speed of digital holographic microscopy (DHM). A fast Fourier transform (FFT) based phase unwrapping algorithm providing a minimum squared error solution is adopted for hardware implementation because of its simplicity and robustness to noise. The proposed architecture is realized in a pipeline fashion to maximize throughput of the computation. Moreover, the number of hardware multipliers and dividers are minimized to reduce the hardware costs. The proposed architecture is used as a custom user logic in a system on programmable chip (SOPC) for physical performance measurement. Experimental results reveal that the proposed architecture is effective for expediting the computational speed while consuming low hardware resources for designing an embedded DHM system.Sensors 01/2011; 11(10):9160-81. · 1.74 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: Diffraction calculations, such as the angular spectrum method, and Fresnel diffractions, are used for calculating scalar light propagation. The calculations are used in wide-ranging optics fields: for example, computer generated holograms (CGHs), digital holography, diffractive optical elements, microscopy, image encryption and decryption, three-dimensional analysis for optical devices and so on. However, increasing demands made by large-scale diffraction calculations have rendered the computational power of recent computers insufficient. We have already developed a numerical library for diffraction calculations using a graphic processing unit (GPU), which was named the GWO library. However, this GWO library is not user-friendly, since it is based on C language and was also run only on a GPU. In this paper, we develop a new C++ class library for diffraction and CGH calculations, which is referred as to a CWO++ library, running on a CPU and GPU. We also describe the structure, performance, and usage examples of the CWO++ library.07/2011;