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Digital holography microscopy

Grant number: 09/10177-0
Support type:Research Grants - Visiting Researcher Grant - International
Duration: October 04, 2009 - January 03, 2010
Field of knowledge:Physical Sciences and Mathematics - Physics - Condensed Matter Physics
Principal researcher:Mikiya Muramatsu
Grantee:Mikiya Muramatsu
Visiting researcher: Kiyofumi Matsuda
Visiting researcher institution: National Institute of Advanced Industrial Science and Technology, Tsukuba (AIST), Japan
Home Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Digital holographic microscopy is a promising technique for visualization and quantitative measurement of phase objects. Typically, in digital holographic microscopy of small objects, like biological cells, a magnified image of the object is recorded with the help of a microscope objective. This method limits the working distance that depends on the microscope objective. We have recently proposed a lens-less Fourier transform digital holographic microscope, in which, a phase object to be imaged is placed inside an expanding beam, and a magnified hologram is recorded on a CCD sensor. This technique eliminates the use of any objective lens and therefore is aberration free. The reconstruction is carried out numerically to obtain the magnified image. However, the accurate determination of a reconstructed image is difficult and it takes a long processing time in a computer. We also proposed a digital holographic microscope using an image correction technique . A phase object to be imaged is placed in one of the two expanding beams and the other beam is used as a reference beam in a holographic recording scheme. In this way, a magnified and blurred image of the object is projected on a CCD. If the blurred image is corrected, a magnified image of the object can be obtained. Since phase information of the object is required for the perfect recovery of the blurred image, a holographic recording allows this correction. The digitized hologram is numerically processed by taking its Fourier transform and dividing by the optical transfer function from the object plane to the CCD. After a filtering process, in which the zero order and a first order diffracted beam are selected and inverse Fourier transformed, a complete amplitude and phase information of the object is obtained in an interferogram. Magnified image of the object can be obtained by mapping out the phase profile extracted from this interferogram. (AU)