Abstract
With the advent of modern computing and imaging technologies, digital holography is becoming widespread in various scientific disciplines such as microscopy, interferometry, surface shape measurements, vibration analysis, data encoding, and certification. Therefore, designing an efficient data representation technology is of particular importance. Off-axis holograms have very different signal properties with respect to regular imagery, because they represent a recorded interference pattern with its energy biased toward the high-frequency bands. This causes traditional images’ coders, which assume an underlying 1/f2 power spectral density distribution, to perform suboptimally for this type of imagery. We propose a JPEG 2000-based codec framework that provides a generic architecture suitable for the compression of many types of off-axis holograms. This framework has a JPEG 2000 codec at its core, extended with (1) fully arbitrary wavelet decomposition styles and (2) directional wavelet transforms. Using this codec, we report significant improvements in coding performance for off-axis holography relative to the conventional JPEG 2000 standard, with Bjontegaard delta-peak signal-to-noise ratio improvements ranging from 1.3 to 11.6 dB for lossy compression in the 0.125 to 2.00 bpp range and bit-rate reductions of up to 1.6 bpp for lossless compression.
Highlights
Fringe patterns occur in many applications across different scientific disciplines and are mainly used for the characterization of object shapes and dimensions
We demonstrate how JPEG 2000 can be efficiently used to compress microscopic off-axis holograms by proposing two extensions to the standard: 1. We replace the existing AD Style (ADS) feature such that any decomposition structure becomes available
This means that our proposed code-stream syntax for the XAD marker requires up to 10 times less bits in the header than that of JPEG 2000’s Arbitrary Decomposition (AD) syntax (ADS and down-sampling factor styles (DFS) markers) for equal decomposition styles, and it has a lower implementation complexity
Summary
Fringe patterns occur in many applications across different scientific disciplines and are mainly used for the characterization of object shapes and dimensions. Applications include interferometric synthetic aperture radar, holographic interference microscopy, photoelasticity measurements, digital holography, and even noninterferometric patterns such as structured imaging applications. Such fringe patterns do not possess the typical frequency distributions found in natural photographic imagery, which results in suboptimal compression performance when using common image compression coder-decoder architectures (codecs). Practical applications for optical holography only started to appear in the 1960s, mainly due to the development of the laser. With the advent of high-resolution digital image sensors (like CCDs) and increasingly faster computers, practical implementations and applications of digital holography started to appear in the 1990s. DHM has been successfully utilized for many different purposes such as the analysis of biological samples[2] and materials, characterization of lenses,[3] and tomography
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