Isaac Y August

Isaac Y August
Shamoon College of Engineering | SCE · Department of Electrical and Electronics Engineering

Doctor of Electro-Optics and Photonics engineering

About

68
Publications
10,166
Reads
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533
Citations
Introduction
Featured research
Article
Full-text available
Extraction of spectral information using liquid crystal (LC) retarders has recently become a topic of great interest because of its importance for creating hyper-and multispectral images in a compact and inexpensive way. However, this method of hyperspectral imaging requires thick LC-layer retarders (50 µm-100 µm and above) to obtain spectral modulation signals for reliable signal reconstruction. This makes the device extremely slow in the case of nematic LCs (NLCs), since the response time of NLCs increases proportionally to the square of the LC-layer thickness, which excludes fast dynamic processes monitoring. In this paper, we explore two approaches for solving the speed problem: the first is based on the use of faster nanospiral ferroelectric liquid crystals as an alternative to NLCs, and the second is based on using a passive multiband filter and focuses on multispectral extraction rather than hyperspectral. A detailed comparative study of nematic and ferroelectric devices is presented. The study is carried out using a 9-spectral bands passive spectral filter, covering the visible and near-infrared ranges. We propose the concept of multispectral rather than hyperspectral extraction, where a small number of wavelengths are sufficient for specific applications.
Article
Full-text available
Liquid crystal phase retarders are utilized by photonic devices and imaging systems for various applications, such as tunable filtering, light modulation, polarimetric imaging, remote sensing and quality inspection. Due to technical difficulties in the manufacturing process, these phase retarders may suffer from spatial non-uniformities, which degrade the performance of the systems. These non-uniformities can be characterized by measuring the spectral transmission at each voltage and each point on the liquid crystal cell, which is time consuming. In this work, we present a new fast and simple method for measuring and computationally estimating the spatial variations of a liquid crystal phase retarder with planar alignment. The method is based on measuring the spectral transmission of the phase retarder at several spatial locations and estimating it at others. The experimental results show that the method provides an accurate spatial description of the phase retarder and can be employed for calibrating relevant systems.
Article
Full-text available
Hyperspectral (HS) imaging involves the sensing of a scene’s spectral properties, which are often redundant in nature. The redundancy of the information motivates our quest to implement Compressive Sensing (CS) theory for HS imaging. This article provides a review of the Compressive Sensing Miniature Ultra-Spectral Imaging (CS-MUSI) camera, its evolution, and its different applications. The CS-MUSI camera was designed within the CS framework and uses a liquid crystal (LC) phase retarder in order to modulate the spectral domain. The outstanding advantage of the CS-MUSI camera is that the entire HS image is captured from an order of magnitude fewer measurements of the sensor array, compared to conventional HS imaging methods.
Article
Full-text available
It is generally held that subtle changes in sandy environments are very difficult to detect in imagery. Nonetheless, this study demonstrates how synthetic aperture radar (SAR) interferometric decorrelation can be used to identify changes in individual sand dunes. The use of coherence maps over time facilitates the analysis of dune dynamics, both temporally and spatially. The Ashdod-Nizzanim coastal dunes, along the southern coastal plain of Israel, were chosen as an illustrative example of the analysis of dune dynamics. High-resolution TerraSAR-X (TSX) radar images covering the entire research area were acquired for the period February to July 2012, together with meteorology data (wind and rain) for the area. The coherence results enabled the stability of individual dunes to be described as a function of time. It was found that the dune crests were more stable than the windward slopes and that the degree of stability was dependent on the distance of the dune from the sea. The results of this study show the potential of using interferometric synthetic aperture radar (InSAR) decorrelation for aeolian studies, even in areas characterized by low coherence.
Additional affiliations
January 2017 - June 2018
Ben-Gurion University of the Negev
Position
  • Fellow

Publications

Publications (68)
Article
In this paper, we present a novel method for measuring the location and estimating the dynamics of fast-moving small objects in free space. The proposed 3D localization method is realized by a space-to-time optical transform and measurement of time-of-flight. We present the underlying physical and mathematical model of the method and provide an exa...
Article
Full-text available
Extraction of spectral information using liquid crystal (LC) retarders has recently become a topic of great interest because of its importance for creating hyper-and multispectral images in a compact and inexpensive way. However, this method of hyperspectral imaging requires thick LC-layer retarders (50 µm-100 µm and above) to obtain spectral modul...
Article
Full-text available
Liquid crystal phase retarders are utilized by photonic devices and imaging systems for various applications, such as tunable filtering, light modulation, polarimetric imaging, remote sensing and quality inspection. Due to technical difficulties in the manufacturing process, these phase retarders may suffer from spatial non-uniformities, which degr...
Conference Paper
Compressive spectral imaging with spectral only encoding may exhibit several advantages over spatial-and-spectral encoding methods. We overview compressive spectral imaging systems that use modified Fabry-Perot resonators that perform only spectral encoding.
Article
Full-text available
Hyperspectral (HS) imaging involves the sensing of a scene’s spectral properties, which are often redundant in nature. The redundancy of the information motivates our quest to implement Compressive Sensing (CS) theory for HS imaging. This article provides a review of the Compressive Sensing Miniature Ultra-Spectral Imaging (CS-MUSI) camera, its evo...
Article
In this Letter, we present a new snapshot hyperspectral (HS) camera based on a multi-aperture design. The technique uses an array of modified Fabry–Perot resonators together with a lens array in order to acquire an array of spectrally multiplexed modulated sub-images. Then the original HS image is reconstructed using a compressive sensing reconstru...
Conference Paper
The parametrization of light rays in form of light fields (LF) have become the standard and probably the most common way for the representation, analysis and processing of rays emitted from 3D objects or from 3D displays. Essentially, the LFs are 4D maps representing the spatial and angular distribution of the intensity of the rays. Nowadays, with...
Article
Light fields are four-dimensional parametrizations of rays, extensively used for the representation of the rays emitted from three-dimensional objects. With the increasing availability of spectral imagers, conventional light fields can be augmented by the additional spectral information, yielding a five-dimensional ray parametrization referred to a...
Article
The acquisition of hyperspectral (HS) image datacubes with available 2D sensor arrays involves a time consuming scanning process. In the last decade, several compressive sensing (CS) techniques were proposed to reduce the HS acquisition time. In this paper, we present a method for near-infrared (NIR) HS imaging which relies on our rapid CS resonato...
Article
Full-text available
It is generally held that subtle changes in sandy environments are very difficult to detect in imagery. Nonetheless, this study demonstrates how synthetic aperture radar (SAR) interferometric decorrelation can be used to identify changes in individual sand dunes. The use of coherence maps over time facilitates the analysis of dune dynamics, both te...
Conference Paper
Recently we presented a Compressive Sensing Miniature Ultra-spectral Imaging System (CS-MUSI)1 . This system consists of a single Liquid Crystal (LC) phase retarder as a spectral modulator and a gray scale sensor array to capture a multiplexed signal of the imaged scene. By designing the LC spectral modulator in compliance with the Compressive Sens...
Conference Paper
We review two compressive spectroscopy techniques based on modulation in the spectral domain that we have recently proposed. Both techniques achieve a compression ratio of approximately 10:1, however each with a different sensing mechanism. The first technique uses a liquid crystal cell as a tunable filter to modulate the spectral signal, and the s...
Article
Full-text available
An optical-digital tunable depth of field (DOF) methodology is presented. The suggested methodology forms a fused image based on the sharpest similar depth regions (SDRs) from a set of source images taken with different phase masks. Each phase mask contains a different degree of DOF extension and implemented by using an annular liquid crystal spati...
Article
Compressive sensing theory was proposed to deal with the high quantity of measurements demanded by traditional hyperspectral systems. Recently, a compressive spectral imaging technique dubbed compressive sensing miniature ultraspectral imaging (CS-MUSI) was presented. This system uses a voltage controlled liquid crystal device to create multiplexed...
Article
We present a new fast compressive spectroscopic technique based on the resonance spectrometric mechanism. This technique uses an appropriately designed Fabry-Perot resonator and a photo-sensor in order to acquire different multiplexed spectral modulations, from which the original signal is reconstructed using a compressive sensing reconstruction al...
Conference Paper
We overview the capability of a new compressive spectral imaging technique that we have recently introduced to capture spectral image datacubes that have giga entries by taking an order of magnitude less samples.
Article
In this Letter, we present a method for hyperspectral imaging of three-dimensional objects. A compressive sensing approach is utilized to remedy the acquisition effort required to capture the large amount of data. The spectral dimension is compressively sensed by means of a liquid crystal-based encoder, and the volumetric data are captured using a...
Conference Paper
The theory of compressive sensing (CS) has opened up new opportunities in the field of imaging. However, its implementation in this field is often not straight-forward and the optical imaging system engineer encounters several hurdles on the way of compressive imaging (CI) realization. The principles of CI design may differ drastically from the pri...
Conference Paper
Recently we introduced a Compressive Sensing Miniature Ultra-Spectral Imaging (CS-MUSI) system. The system is based on a single Liquid Crystal (LC) cell and a parallel sensor array where the liquid crystal cell performs spectral encoding. Within the framework of compressive sensing, the CS-MUSI system is able to reconstruct ultra-spectral cubes cap...
Article
In various applications, such as remote sensing and quality inspection, hyperspectral (HS) imaging is performed by spatially scanning an object. In this work, we present a new compressive hyperspectral imaging method that performs along-track scanning. The method relies on the compressive sensing miniature ultra-spectral imaging (CS-MUSI) system, w...
Article
Full-text available
Spectroscopic imaging has been proved to be an effective tool for many applications in a variety of fields, such as biology, medicine, agriculture, remote sensing and industrial process inspection. However, due to the demand for high spectral and spatial resolution it became extremely challenging to design and implement such systems in a miniaturiz...
Conference Paper
We overview the capability of a new compressive spectral imaging technique that we have recently introduced to capture spectral image datacubes that have giga entries by taking an order of magnitude less samples.
Article
Hyperspectral imagery involves capturing and processing a tremendous amount of data, which sets severe system resource requirements. This has motivated the application of compressive sensing for different spectroscopic and spectroscopic imager systems. Several new compressive hyperspectral architectures have been designed to stretch the common limi...
Conference Paper
Recently we have proposed a new compressive spectral sensing method based on modulation in the spectral domain, without the need of diffractive or dispersive elements. Here, we expand the compressive sensing spectrometry to hyperspectral imaging.
Conference Paper
Full-text available
Recently we introduced a hyperspectral compressive sensing scheme that uses separable projections in the spatial and spectral domains. The separable encoding schemes facilitates the optical implementation, reduces the computational burden dramatically, and storage requirements. Owing to these benefits we have been able to encode the hyperspectral c...
Conference Paper
Full-text available
The theory of compressive sensing and sparse representations broke the traditional linkage between the resolution of the optical signals and the bandwidth of the acquisition process. As such, it opened the path to new optical super-resolving systems; that is, methods and systems that are able to capture optical signals with resolution beyond the cl...
Conference Paper
Full-text available
Recently we presented a method for compressive spectrometry based on a liquid crystal cell. Here we describe the spectrum reconstruction dependence on the type of sparsifier used in the reconstruction process.
Conference Paper
Full-text available
In this paper we overview three hyperspectral compressive imaging methods that we have developed. The first method is an efficient extension of the single-pixel camera to include compressive spectrometry. The second method is an extension of a Radon-based compressive imaging technique to perform spectral sensing. The third method is based on a rece...
Article
Full-text available
We present a new type of compressive spectroscopy technique employing a liquid crystal (LC) phase retarder. A tunable LC cell is used in a manner compliant with the compressive sensing (CS) framework to significantly reduce the spectral scanning effort. The presented optical spectrometer consists of a single LC phase retarder combined with a single...
Conference Paper
Full-text available
The PS-InSAR method results are highly depending on the Persistent Scatters Candidate (PSC) selection process. This study implements a new algorithm for detection of PSC in open fields and natural areas based on high resolution TerraSAR-X images. The main challenge in PSC detection in natural areas is the lack of strong reflected targets in these a...
Article
Full-text available
Abstract: A new imaging technique that combines compressive sensing and super-resolution techniques is presented. Compressive sensing is accomplished by capturing optically a set of Radon projections. Superresolution measurements are simply taken by introducing a slanted twodimensional array in the optical system. The goal of the technique is to ov...
Conference Paper
Full-text available
The theory of compressive sensing (CS) has opened up new opportunities in the field of optical imaging. However, its implementation in this field is often not straight-forward. We list the implementation challenges that might arise in compressive imaging and present some solutions to overcome them.
Conference Paper
Full-text available
Hyperspectral imaging is a natural field for the implementation of compressive sensing because typical captured hyperspectral datacubes involve large amount of data which is also often very redundant. Compressive hypersepctral systems compress the hyperspectral data already in the acquisition step, thus remedy the severe storage and processing requ...
Conference Paper
Full-text available
Compressive hyperspectral imaging is based on the fact that hyperspectral data is highly redundant. However, there is no symmetry between the compressibility of the spatial and spectral domains, and that should be taken into account for optimal compressive hyperspectral imaging system design. Here we present a study of the influence of the ratio be...
Article
Full-text available
An efficient method and system for compressive sensing of hyperspectral data is presented. Compression efficiency is achieved by randomly encoding both the spatial and the spectral domains of the hyperspectral datacube. Separable sensing architecture is used to reduce the computational complexity associated with the compressive sensing of a large v...
Article
Full-text available
Our goal in this work is to demonstrate that detectors behave differently for different images and targets and to propose a novel approach to proper detector selection. To choose the algorithm, we analyze image statistics, the target signature, and the target's physical size, but we do not need any type of ground truth. We demonstrate our ability t...
Conference Paper
Full-text available
Introduction: Monitoring geomorphic changes on other planets is always a puzzle while on Earth measur-ing geomorphological dynamics can involve field work, i.e., ground truth. Dunes, wind streaks and other aeolian morphologies have been identified on Earth, Mars, Venus and Titan. These morphologies can be subjected to rapid and continuous changes w...
Conference Paper
Full-text available
Monitoring geomorphic changes on other planets is always a puzzle while on Earth measuring geomorphological dynamics can involve field work, i.e., ground truth. Dunes, wind streaks and other aeolian morphologies have been identified on Earth, Mars, Venus and Titan. These morphologies can be subjected to rapid and continuous changes when the surface...
Conference Paper
Full-text available
The PSI (Persistent Scatterers Interferometry) method relies on identifying a small group of scatterers that maintain high phase reliability over a relatively long period of time. This study demonstrates a new algorithm to identify natural PSC (persistent scatterer candidates) targets in non-inhabited areas. The application of our PSC selection pro...
Conference Paper
Full-text available
1. ABSTRACT The PSI (Persistent scatterers Interferometry) method re-lies on identifying a small group of scatterers that main-tain high phase reliability over a relatively long period of time. This study demonstrates a new algorithm to iden-tify natural PSC (persistent scatterer candidates) targets in non-inhabited areas. The application of our PS...
Conference Paper
Full-text available
Image registration is one of the important steps in processing remote sensing data. In the process of SAR interferometry (InSAR) there is use of multiple data sets from different times or different look angles. Generally, data registration processes contain two steps; the first step is estimation of the transformation of coordinates from the refere...

Projects

Project (1)
Project
Developing advanced compressive imaging systems.