For defect detection or undesired object in commercial products, it is required to develop a fast measurement system that can obtain three-dimensional distribution of surface of the opaque medium such as metal or inside of the transparent medium. For this purpose, we fabricated a digital holographic microscope using a fast image sensor when the phase object is put on a fast movable stage. In the fabricated system, an image sensor operated at maximum frame rate of 2000 fps and a movable stage operated at maximum speed of 300 mm/s are introduced. Under the continuous wave illumination, motion-blurred phase object is reconstructed. By using numerical processing such as deconvolution filter, the reconstructed phase distribution is much improved. Numerical results are presented.
One of fast measurement systems of μm-size phase objects based on digital holographic microscope with transmission geometry is presented. For building a 3D inspection system of the phase objects, the improvement of recovered phase image is discussed. Under the CW laser illumination, the movement afterimage of phase object was observed. The phase object is recovered by deconvolution filter. Experimental and numerical evaluation are presented.
Multi-modal digital holographic microscopy is a combination of epifluorescence microscopy and digital holographic microscopy, the main function of which is to obtain images from fluorescence intensity and quantified phase contrasts, simultaneously. The proposed system is mostly beneficial to biological studies, with the reason that often the studies are depending on fluorescent labeling techniques to detect certain intracellular molecules, while phase information reflecting properties of unstained transparent elements. This paper is presenting our latest researches on applications such as randomly moving micro-fluorescent beads and living cells of Physcomitrella patens. The experiments are succeeded on obtaining a succession of wide-field fluorescent images and holograms from micro-beads, and different depths focusing is realized via numerical reconstruction. Living cells of Physcomitrella patens are recorded in the static manner, the reconstruction distance indicates thickness of cellular structure. These results are implementing practical applications toward many biomedical science researches.
KEYWORDS: Digital holography, Phase shifts, 3D image reconstruction, Holograms, Image sensors, 3D metrology, Holography, High speed cameras, Cameras, Polarization
Digital holography is a technique of 3D measurement of object. The technique uses an image sensor to record the interference fringe image containing the complex amplitude of object, and numerically reconstructs the complex amplitude by computer. Parallel phase-shifting digital holography is capable of accurate 3D measurement of dynamic object. This is because this technique can reconstruct the complex amplitude of object, on which the undesired images are not superimposed, form a single hologram. The undesired images are the non-diffraction wave and the conjugate image which are associated with holography. In parallel phase-shifting digital holography, a hologram, whose phase of the reference wave is spatially and periodically shifted every other pixel, is recorded to obtain complex amplitude of object by single-shot exposure. The recorded hologram is decomposed into multiple holograms required for phase-shifting digital holography. The complex amplitude of the object is free from the undesired images is reconstructed from the multiple holograms. To validate parallel phase-shifting digital holography, a high-speed parallel phase-shifting digital holography system was constructed. The system consists of a Mach-Zehnder interferometer, a continuous-wave laser, and a high-speed polarization imaging camera. Phase motion picture of dynamic air flow sprayed from a nozzle was recorded at 180,000 frames per second (FPS) have been recorded by the system. Also phase motion picture of dynamic air induced by discharge between two electrodes has been recorded at 1,000,000 FPS, when high voltage was applied between the electrodes.
It will be useful in biological applications if two or more physical parameters are simultaneously measured in a digital holographic microscope. In this paper, we present a hybrid digital holographic microscope that can measure simultaneously three-dimensional (3D) phase and 3D fluorescence distributions. This property has big advantage compared with conventional optical microscopes such as phase contrast microscope and fluorescence microscope. We present an optical setup for measuring both phase and fluorescence images. In the experiments, two objects that are fluorescence beads and egera densa are used. The separation method of phase and fluorescence images is presented.
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