Edge enhancement in digital holo-microscopy
15 Jun 2015-Vol. 9654, pp 164-167
TL;DR: In this article, a simple edge enhancement technique in the digital holo-microscopy is presented, which is accomplished by multiplication of the digitally stored hologram with a digital model of the reference wave and subsequent numerical determination of the diffracted field of the object in a defined image plane.
Abstract: A simple edge enhancement technique in the digital holo-microscopy is presented here. In Digital Holo-microscopy
(DHM) the intensity distribution of the CCD is produced by the interference of a plane reference wave and that
scattered by the object. The reconstruction is accomplished by multiplication of the digitally stored hologram with a
digital model of the reference wave and subsequent numerical determination of the diffracted field of the object in a
defined image plane. Hence, a focused and a defocused version of the object may be reconstructed from only one
recorded hologram by varying the reconstruction distance during numerical reconstruction. The edge enhancement
of the object is possible by simply subtracting this numerically reconstructed defocused real image from the focused
real image. It is interesting to note that using this technique edge enhancement technique is possible for amplitude
and phase objects. The simulation and experimental results presented validate our theoretical expectations.
References
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TL;DR: Off-axis holograms recorded with a magnified image of microscopic objects are numerically reconstructed in amplitude and phase by calculation of scalar diffraction in the Fresnel approximation to show that the transverse resolution is equal to the diffraction limit of the imaging system.
Abstract: We present a digital method for holographic microscopy involving a CCD camera as a recording device. Off-axis holograms recorded with a magnified image of microscopic objects are numerically reconstructed in amplitude and phase by calculation of scalar diffraction in the Fresnel approximation. For phase-contrast imaging the reconstruction method involves the computation of a digital replica of the reference wave. A digital method for the correction of the phase aberrations is presented. We present a detailed description of the reconstruction procedure and show that the transverse resolution is equal to the diffraction limit of the imaging system.
1,174 citations
TL;DR: It is demonstrated that spatial resolution in the reconstructed plane can be written as a convolution product of functions that describe these influences of each of the physical effects invoked in digital holography.
Abstract: We present a detailed analysis of image formation in digital Fresnel holography. The mathematical modeling is developed on the basis of Fourier optics, making possible the understanding of the different influences of each of the physical effects invoked in digital holography. Particularly, it is demonstrated that spatial resolution in the reconstructed plane can be written as a convolution product of functions that describe these influences. The analysis leads to a thorough investigation of the effect of the width of the sensor, the surface of pixels, the numerical focusing, and the aberrations of the reference wave, as well as to an explicit formulation of the Shannon theorem for digital holography. Experimental illustrations confirm the proposed theoretical analysis.
193 citations
TL;DR: In this article, a Bessel-like amplitude modulated spiral phase filter was used in a real-time spatial image edge enhancement system in optical microscopy for biological sample imaging.
Abstract: We experimentally demonstrate that a Bessel-like amplitude modulated spiral phase filter can be used in a real-time spatial image edge enhancement system in optical microscopy for biological sample imaging. Compared with previous methods based on a conventional spiral phase filter, a dark-field spiral phase filter and the Laguerre–Gaussian modulated spiral phase filter, the proposed technique further reduces the imaging diffraction noise. Experimental verifications in edge enhancement are implemented by a phase-only spatial light modulator for realizing the amplitude modulated spiral phase. It is shown that the proposed technique is able to efficiently suppress the diffraction noise and achieve high quality edge enhancement images for biological samples.
28 citations