2,776 research outputs found
Noise and aliases in off-axis and phase-shifting holography
We have compared the respective efficiencies of off-axis and phase-shifting
holography in terms of noise and aliases removal. The comparison is made by
analyzing holograms of an USAF target backlit with laser illumination, recorded
with a charge-coupled device camera. We show that it is essential to remove the
LO beam noise, especially at low illumination levels
Digital Holography at Shot Noise Level
By a proper arrangement of a digital holography setup, that combines off-axis
geometry with phase-shifting recording conditions, it is possible to reach the
theoretical shot noise limit, in real-time experiments.We studied this limit,
and we show that it corresponds to 1 photo-electron per pixel within the whole
frame sequence that is used to reconstruct the holographic image. We also show
that Monte Carlo noise synthesis onto holograms measured at high illumination
levels enables accurate representation of the experimental holograms measured
at very weak illumination levels. An experimental validation of these results
is done
(DH) Noise and Signal scaling factors in Digital Holography in week illumination: relationship with Shot Noise
We have performed off axis heterodyne holography with very weak illumination
by recording holograms of the object with and without object illumination in
the same acquisition run. We have experimentally studied, how the reconstructed
image signal (with illumination) and noise background (without) scale with the
holographic acquisition and reconstruction parameters that are the number of
frames, and the number of pixels of the reconstruction spatial filter. The
first parameter is related to the frequency bandwidth of detection in time, the
second one to the bandwidth in space. The signal to background ratio varies
roughly like the inverse of the bandwidth in time and space. We have also
compared the noise background with the theoretical shot noise background
calculated by Monte Carlo simulation. The experimental and Monte Carlo noise
background agree very well together
Heterodyne Holography with full control of both signal and reference arms
Heterodyne holography is a variant of phase shifting holography in which
reference and signal arms are controlled by acousto optic modulators. In this
review paper, we will briefy describe the method and its properties, and we
will illustrate its advantages in experimental applications
Assessment of speckle denoising filters for digital holography using subjective and objective evaluation models
Digital holography is an emerging imaging technique for displaying and sensing three dimensional objects. The perceived image quality of a hologram is frequently corrupted by speckle noise due to coherent illumination. Although several speckle noise reduction methods have been developed so far, there are scarce quality assessment studies to address their performance and they typically focus solely on objective metrics. However, these metrics do not reflect the visual quality perceived by a human observer.
In this work, the performance of four speckle reduction algorithms, namely the nonlocal means, the Lee, the Frost and the block matching 3D filters, with varying parameterizations, were subjectively evaluated. The results were ranked with respect to the perceived image quality to obtain the mean opinion scores using pairwise comparison. The correlation between the subjective results and twenty different no-reference objective quality metrics was evaluated.
The experiment indicates that block matching 3D and Lee are the preferred filters, depending on hologram characteristics. The best performing objective metrics were identified for each filter.info:eu-repo/semantics/publishedVersio
Roadmap on holography
From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful.This work was supported by Ministerio de EconomĂa, Industria y Competitividad (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER), and by Generalitat Valenciana (Spain) under project PROMETEO II/2015/015
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Using complex light modulation for holographic applications
Complex light modulation is the ability to control a light-wave’s phase and amplitude, thereby allowing complete control of the light-wave at any spatial location. The applied optics group at The University of Texas at Austin Electrical and Computer Engineering Department created a fully complex hologram by a combination of spatial light modulators. A digital micromirror device (DMD) was used to produce a precise amplitude profile, and a liquid crystal spatial light modulator (SLM) was used to produce the phase profile. A band-limited 4-f imaging system imaged the DMD onto the SLM to create a fully complex modulated wavefront, which reconstructed a holographic image at the desired location. With this capability, it is possible to create improved imaging methods for the consumer, medical, and defense industries as well as applications in holography. Our previous research has successfully created phase-only holograms (POH), amplitude-only beam-shaping patterns, and published simulation results on full-complex modulation. This thesis provides an in-depth experimental analysis of the full-complex hologram.Electrical and Computer Engineerin
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