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.

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.

scholarly journals Combined Reduced Phase Dual-Directional Illumination Digital Holography and Speckle Displacements for Shape Measurement

2019 ◽  
Vol 2019 ◽  
pp. 1-6
Author(s):  
Davood Khodadad
Keyword(s):  
Phase Difference ◽  
Digital Holography ◽  
Relative Phase ◽  
Groove Depth ◽  
Phase Unwrapping ◽  
Shape Measurement ◽  
Phase Ambiguity ◽  
Holographic Method ◽  
Height Range ◽  
Phase Differences

We present a digital holographic method to increase height range measurement with a reduced phase ambiguity using a dual-directional illumination. Small changes in the angle of incident illumination introduce phase differences between the recorded complex fields. We decrease relative phase difference between the recorded complex fields 279 and 139 times by changing the angle of incident 0.5° and 1°, respectively. A two cent Euro coin edge groove is used to measure the shape. The groove depth is measured as ≈300  μm. Further, numerical refocusing and analysis of speckle displacements in two different planes are used to measure the depth without a use of phase unwrapping process.

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.

scholarly journals Amplitude and phase reconstruction of photorefractive spatial bright-soliton in LiNbO_3 during its dynamic formation by digital holography

2007 ◽  
Vol 15 (13) ◽  
pp. 8243 ◽  
Author(s):  
M. Paturzo ◽  
L. Miccio ◽  
S. De Nicola ◽  
P. De Natale ◽  
P. Ferraro
Keyword(s):  
Digital Holography ◽  
Bright Soliton ◽  
Phase Reconstruction ◽  
Dynamic Formation

Investigation on Phase Unwrapping Algorithms in Digital Holography

2009 ◽  
Vol 29 (12) ◽  
pp. 3323-3327 ◽  
Author(s):  
张亦卓 Zhang Yizhuo ◽  
王大勇 Wang Dayong ◽  
赵洁 Zhao Jie ◽  
万玉红 Wan Yuhong ◽  
江竹青 Jiang Zhuqing ◽  
...  
Keyword(s):  
Digital Holography ◽  
Phase Unwrapping

Speckle removal in phase reconstruction of digital holography for structured surfaces

2016 ◽  
Vol 45 (7) ◽  
pp. 0726002
Author(s):  
张晓磊 Zhang Xiaolei ◽  
张祥朝 Zhang Xiangchao ◽  
肖 虹 Xiao Hong ◽  
徐 敏 Xu Min
Keyword(s):  
Digital Holography ◽  
Phase Reconstruction ◽  
Structured Surfaces

Continuous-wave off-axis and in-line terahertz digital holography with phase unwrapping and phase autofocusing

2018 ◽  
Vol 426 ◽  
pp. 612-622 ◽  
Author(s):  
Haochong Huang ◽  
Dayong Wang ◽  
Lu Rong ◽  
Spozmai Panezai ◽  
Donglei Zhang ◽  
...  
Keyword(s):  
Digital Holography ◽  
Continuous Wave ◽  
Phase Unwrapping

Phase reconstruction using compressive two-step parallel phase-shifting digital holography

2018 ◽  
Vol 57 (04) ◽  
pp. 1 ◽  
Author(s):  
Prakash Ramachandran ◽  
Zachariah C. Alex ◽  
Anith Nelleri
Keyword(s):  
Digital Holography ◽  
Phase Shifting ◽  
Phase Reconstruction
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