scholarly journals Response to “Effect of the fill factor of CCD pixels on digital holograms: comment on the papers ‘Frequency analysis of digital holography’ and ‘Frequency analysis of digital holography with reconstruction by convolution’ ”

2003 ◽  
Vol 42 (9) ◽  
pp. 2772 ◽  
Author(s):  
Thomas M. Kreis
Keyword(s):  
Frequency Analysis ◽  
Digital Holography ◽  
Fill Factor ◽  
Digital Holograms

scholarly journals Providing a Visual Understanding of Holography Through Phase Space Representations

2020 ◽  
Vol 10 (14) ◽  
pp. 4766
Author(s):  
Tobias Birnbaum ◽  
Tomasz Kozacki ◽  
Peter Schelkens
Keyword(s):  
Phase Space ◽  
Frequency Analysis ◽  
Digital Holography ◽  
Joint Space ◽  
Visual Interpretation ◽  
Spatial Frequencies ◽  
Digital Holograms ◽  
Spatial Coordinates ◽  
Visual Understanding ◽  
Space Frequency

Digital holograms are a prime example for signals, which are best understood in phase space—the joint space of spatial coordinates and spatial frequencies. Many characteristics, as well as optical operations can be visualized therein with so called phase space representations (PSRs). However, literature relies often only on symbolic PSRs or on, in practice, visually insufficient PSRs like the Wigner–Ville representation. In this tutorial-style paper, we will showcase the S-method, which is both a PSR that can be calculated directly from any given signal, and that allows for a clear visual interpretation. We will highlight the power of space-frequency analysis in digital holography, explain why this specific PSR is recommended, discuss a broad range of basic operations, and briefly overview several interesting practical questions in digital holography.

Phase-shifting digital holography with an unknown reference beam

2021 ◽  
Author(s):  
Roghayeh Yazdani ◽  
Hamidreza Fallah
Keyword(s):  
Digital Holography ◽  
Phase Retrieval ◽  
Reference Beam ◽  
Phase Shifting ◽  
Retrieval Algorithm ◽  
Reference Field ◽  
Digital Holograms ◽  
Noisy Conditions ◽  
Phase Retrieval Algorithm

In digital holography, errors of the reference field degrade the quality of the reconstructed object field. In this paper, we propose an effective method in phase-shifting digital holography in which the reference field does not need to be known and perfect. The unknown complex amplitudes of both reference and object fields are derived simultaneously. The method employs only five digital holograms and a single execution of a phase retrieval algorithm. So, the required measurements and algorithm executions in this method are fewer than those in other methods; it suggests a simpler and faster method. The effectiveness of the suggested method is indicated by simulation, under noise-free and noisy conditions. Moreover, the capability of the method to extract full information about the phase singularities in both fields is demonstrated.

Auto Focusing in Digital Holography to Study Marine Microorganism

2014 ◽  
Vol 577 ◽  
pp. 767-770 ◽  
Author(s):  
Chun Ming Tang ◽  
Yu Cui Liu
Keyword(s):  
Digital Holography ◽  
Signal To Noise Ratio ◽  
New Method ◽  
Marine Microorganism ◽  
Signal To Noise ◽  
Criterion Function ◽  
Reconstruction Image ◽  
Digital Holograms ◽  
Simulation Results ◽  
Auto Focusing

Auto-focus is an important technique for auto reconstruction of digital holograms, and works by focusing criterion function which influences the effect of the autofocus greatly. Aiming at Marine Microorganism holograms, this paper proposes a new focused criterion function established according to characteristics of detail discrete degree in reconstruction image changing with FD. Simulation results illustrate that, the proposed method, compared with several existing methods, has better single peak, higher sensibility and higher signal to noise ratio (SNR). The new method can realize autofocus of reconstruction distance to implement auto reconstruction of holograms.

Frequency analysis of digital holography

2002 ◽  
Vol 41 (4) ◽  
pp. 771 ◽  
Author(s):  
Thomas M. Kreis
Keyword(s):  
Frequency Analysis ◽  
Digital Holography

scholarly journals Multi-Incidence Holographic Profilometry for Large Gradient Surfaces with Sub-Micron Focusing Accuracy

Sensors ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 214
Author(s):  
Moncy Sajeev Idicula ◽  
Tomasz Kozacki ◽  
Michal Józwik ◽  
Patryk Mitura ◽  
Juan Martinez-Carranza ◽  
...  
Keyword(s):  
Digital Holography ◽  
Fourier Transforms ◽  
Element Approximation ◽  
Fourier Space ◽  
Manual Adjustment ◽  
Large Gradient ◽  
Gradient Surfaces ◽  
Digital Holograms ◽  
Focus Plane ◽  
Numerical Generation

Surface reconstruction for micro-samples with large discontinuities using digital holography is a challenge. To overcome this problem, multi-incidence digital holographic profilometry (MIDHP) has been proposed. MIDHP relies on the numerical generation of the longitudinal scanning function (LSF) for reconstructing the topography of the sample with large depth and high axial resolution. Nevertheless, the method is unable to reconstruct surfaces with large gradients due to the need of: (i) high precision focusing that manual adjustment cannot fulfill and (ii) preserving the functionality of the LSF that requires capturing and processing many digital holograms. In this work, we propose a novel MIDHP method to solve these limitations. First, an autofocusing algorithm based on the comparison of shapes obtained by the LSF and the thin tilted element approximation is proposed. It is proven that this autofocusing algorithm is capable to deliver in-focus plane localization with submicron resolution. Second, we propose that wavefield summation for the generation of the LSF is carried out in Fourier space. It is shown that this scheme enables a significant reduction of arithmetic operations and can minimize the number of Fourier transforms needed. Hence, a fast generation of the LSF is possible without compromising its accuracy. The functionality of MIDHP for measuring surfaces with large gradients is supported by numerical and experimental results.

scholarly journals Shape and deformation measurements of rough surfaces by phase-shifting digital holography

2021 ◽  
Vol 13 (4) ◽  
pp. 70
Author(s):  
Ichirou Yamaguchi
Keyword(s):  
Digital Holography ◽  
Noise Suppression ◽  
Rough Surfaces ◽  
Speckle Noise ◽  
Photonic Devices ◽  
Phase Shifting ◽  
Surface Shape ◽  
Shape Measurement ◽  
Optical Surfaces ◽  
Digital Holograms

In digital holography recording as reconstruction of holograms are performed digitally by modern photonic devices to increase of optical non-contacting measurements of various kinds of surfaces including both specular and rough surfaces. In this article we discusses these features of digital holography using phase shifting techniques that has much extended its capabilities. Full Text: PDF ReferencesG. Bruning, D.R. Herriott, J.E. Gallagher, D.P. Rosenfeld, A.D. White, D.J. Brangaccio, "Digital Wavefront Measuring Interferometer for Testing Optical Surfaces and Lenses", Appl. Opt. 13, 2693 (1974). CrossRef I. Yamaguchi, T. Zhang, "Phase-shifting digital holography", Opt. Lett. 22, 1268 (1997). CrossRef F. Zhang, I. Yamaguchi, L.P. Yaroslavsky, "Algorithm for reconstruction of digital holograms with adjustable magnification", Opt. Lett. 29, 1668 (2004). CrossRef I. Yamaguchi, "Holography, speckle, and computers", Optics and Lasers in Engineering 39, 411 (2003). CrossRef I. Yamaguchi, M. Yokota, "Speckle noise suppression in measurement by phase-shifting digital holography", Opt. Eng. 48 085602 (2009). CrossRef I. Yamaguchi, J. Kato, S. Ohta, "Surface Shape Measurement by Phase-Shifting Digital Holography", Opt. Rev. 8, 85 (2001). CrossRef I. Yamaguchi, J. Kato, H. Matsuzaki, "Measurement of surface shape and deformation by phase-shifting image digital holography", Opt. Eng. 42, 1267 (2003). CrossRef F. Zhang, J.D.R. Valera, I. Yamaguchi, M. Yokota, G. Mills, "Vibration Analysis by Phase Shifting Digital Holography", Opt. Rev. 11, 5 (2004). CrossRef

scholarly journals Measurements of the Characteristics of Transparent Material Using Digital Holography

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Ding Yu ◽  
Shang Wenbin ◽  
Yang Hong ◽  
Yang Yan
Keyword(s):  
Digital Holography ◽  
3D Visualization ◽  
Phase Unwrapping ◽  
Measurement Tool ◽  
Phase Reconstruction ◽  
Transparent Material ◽  
Validation Experiment ◽  
Reconstruction Image ◽  
Digital Holograms ◽  
Transparent Object

Digital holography is applied to measure the characteristics of transparent material. A digital hologram recording system to measure the surface of transparent material was established, and the digital holograms of transparent object were obtained in high quality. For postprocessing of hologram, the least-squares phase unwrapping algorithm was used in phase unwrapping, and the phase reconstruction image of transparent object was obtained. The information of material surfaces was measured and the characteristic was presented in 3D visualization. The validation experiment was conducted by NanoMap 500LS system; the results of validation experiment are well satisfied with the measurement by digital holography, which proved the feasibility of digital holographic technology as a good measurement tool for transparent material.

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