339 research outputs found
Coefficients Quantization at Off-axis Digital Hologram Wavelet Compression
Digital holographic information is compressed for storage of 2D- or 3D-objects amplitude and phase distributions, fast transmission, analyzing and displaying of these data. In this paper features of application of wavelet transforms for off-axis digital holograms compression are considered. The combined technique based on zero and twin orders elimination, wavelet compression of the amplitude and phase components of obtained Fourier spectrum and further additional compression of wavelet coefficients by thresholding and quantization is analyzed. Numerical experiments on reconstruction of images from the compressed holograms are performed. The comparative analysis of applicability of various wavelets and additional quantization of coefficients is performed. Obtained results demonstrate possibility of 180 and more times compression using iterative and noniterative methods of coefficients quantization and threshold zeroing less 80% of wavelet coefficients.
Keywords: digital holography, hologram compression, wavelets, quantization, thresholding, digital image processing
Compressive Holographic Video
Compressed sensing has been discussed separately in spatial and temporal
domains. Compressive holography has been introduced as a method that allows 3D
tomographic reconstruction at different depths from a single 2D image. Coded
exposure is a temporal compressed sensing method for high speed video
acquisition. In this work, we combine compressive holography and coded exposure
techniques and extend the discussion to 4D reconstruction in space and time
from one coded captured image. In our prototype, digital in-line holography was
used for imaging macroscopic, fast moving objects. The pixel-wise temporal
modulation was implemented by a digital micromirror device. In this paper we
demonstrate temporal super resolution with multiple depths recovery
from a single image. Two examples are presented for the purpose of recording
subtle vibrations and tracking small particles within 5 ms.Comment: 12 pages, 6 figure
Digital hologram recording systems: some performance improvements
The work presented in this thesis was performed under the EU's Framework
7 (FP7) project, 'REAL3D'. The aim of this project is to develop methods
based on digital holography for real time capture and display of 3D objects.
This thesis forms a small subset of all the work done in this project. Much of
the research work was aimed towards fullling our part of the requirements
of the REAL3D project. The central theme of the research presented in
this thesis is that of improving the performance of the digital holographic
imaging system for its use in 3D display. This encompasses research into
speed up of reconstruction algorithms, understanding the in
uence of noise
and developing techniques to increase resolution and angular perspective
range in reconstructions.
The main original contributions of this research work presented in this thesis
are:
A computer-interfaced automatic digital holographic imaging
system employing `phase shifting' has been built. This system
is capable of recording high-quality digital holograms of a real world
3D object. The object can be rotated on a rotational stage and a full
360 range of perspectives can be recorded. Speckle reduction using
moving diusers can be performed to improve the image quality of the
reconstructed images. A LabView based user friendly interface has
been developed.
Novel methods based on space-time tradeo and xed point
arithmetic have been developed and implemented for speed-
ing up the reconstruction algorithm used in digital holography.
This has resulted in the publication of one peer-reviewed journal pub-
lication and one conference proceeding [1, 2].
The in
uence of additive noise, particularly quantization noise
in digital holography has been studied in detail. A model
has been developed to understand the in
uence of noise on the re-
constructed image quality. Based on this model, a method has been
developed to suppress quantization noise in a memory ecient man-
ner. This work led to the publication of two peer-reviewed journal
publications [3, 4].
A novel method of removing the twin image has been devel-
oped.
Methods to increase the perspectives in holography based on
synthetic aperture have been implemented.
Apart from these primary contributions, the author of this thesis has
also contributed in the form of assisting in experiments, creating gures
for various papers, writing computer programs and discussions during
group meetings. In total, 6 peer-reviewed journal papers (3 being
primary author) have been published and 6 conference proceedings (3
being primary author) have been published. Additionally, 2 talks have
been given at international conferences
Roadmap on optical security
Postprint (author's final draft
- …