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Acoustic imaging is an advanced technique for acoustic source localization and power reconstruction from limited noisy measurements at microphone sensors. To solve this ill-posed inverse problem, the Bayesian inference methods using proper prior knowledge have been widely investigated. In this paper, we propose to use a hierarchical Variational Bayesian Approximation for the robust acoustic imaging...
We have constructed two portable parallel phase-shifting digital holography systems. One is an A3-sized parallel phase-shifting digital holography system and the other is an A4-sized parallel phase-shifting digital holography system. The size and weight of the A3-sized system are 450 mm (L) × 250 mm (W) × 200 mm (H) and 7kg, respectively. The system was constructed by use of ready-made optical components...
We develop a variational algorithm for reconstructing phase objects from a series of bright field micrographs. Our mathematical model is based on the transport-of-intensity equation (TIE), which links the phase of a complex field to the axial derivative of its intensity. To reduce reconstruction artifacts, we formulate TIE in a regularized fashion by introducing a family of penalty functionals based...
Phase retrieval is an iterative method that has been developed to recover the lost phase information in coherent diffraction imaging. The most widely used algorithm is the hybrid input-output (HIO) algorithm because of its ability to avoid local minimum. Unfortunately the presence of noise in the images acquired disturbs the convergence of the algorithm. A few solutions have been proposed in order...
This paper reviews a recently developed technique in the research field of coherence-based image formation and spectral recovery. The developed method enables to obtain a hypermultispectral set of three-dimensional images for spatially incoherent, polychromatic object. The review includes a description of the method and experimental demonstrations to show the validity of the method.
Spatial Light Modulators currently available lack of resolution to display large hologram, it is then necessary to find some technique to broaden the size of the reconstructed image. For example, time multiplexing can be use to tile several elementary holograms via a high speed scanning system. However, the best compromise to exploit the bandwidth of the SLM is to use binary data, holograms acquired...
Multimedia security can be foiled thanks to Slepian's permutation modulation. Originally proposed in 1965 for standard problems of channel and source coding in communications, permutation codes can also provide optimum solutions in two relevant fields: steganography (foiling hidden information detection tests) and counterforensics (foiling forensic detection tests). In the first scenario, permutation...
We describe computational imaging techniques based on single-pixel detection providing multidimensional information of an input scene. The key element of the optical recording stage is a spatial light modulator which sequentially generates a set of intensity light patterns to sample the scene. In this way, it is possible to use single-pixel detectors to measure different optical parameters such as...
The use of an “inverse problems” algorithm for self-calibration of a digital holographic set-up is proposed. Taking into account a precise imaging model for the process of calibrated pattern hologram makes possible an accurate estimation of setup parameters. Self-calibration of an astigmatic reference beam holographic configuration and measurement of the camera pixel fill factor is demonstrated.
In this paper we present a new approach for the measurement of multiple digital holograms at different positions in space that can be combined to one high resolution hologram. The reconstruction is based on a phase shifting approach, where the CCD sensor and the reference wave are moved simultaneously along different positions in x and y. An inclination of the reference wave induces a phase shift...
Holographic data storage based on polarization techniques is proposed. Angular and shift multiplexing techniques, as well as polarization multiplexing, are developed to increase storage capacity. Some experimental results are presented.
Computational holography based on the mutual conversion between ray information and wavefront is introduced. By dealing with ray and wavefront domains properly in the hologram calculation process, the proposed method can be compatible both domain's advantages. In the optical experiment, some main features of proposed method; the photorealistic image reconstruction by using computer graphics technique,...
We demonstrate an optical profilometer composed of an optical frequency comb source, a single pixel camera, and an optoelectronic interferometer in radio frequecny range. The system enables us to measure an object with a large depth much more than a light wavelength. The wide dynamic range is achieved by the high stability of the RF signal. The single pixel camera is used for two-dimensional imaging...
The moirés appearing in the contact-type 3 dimensional displays are chirped by the thickness of the viewing zone forming optics (VZFO) in the displays. Due to the thickness, the patterns of the display panels for the displays are refracted on to the pattern plane of VZFO to superpose with the pattern on the plane. The moirés formed this way can have chirped fringe patterns, and change numbers and...
Steady-state visual evoked potential (SSVEP) is one of the most effective modalities for brain-computer interaction. However, its flickering visual stimuli may cause discomfort, even induce migraine and seizure attacks among its viewers. This paper presents a novel approach to induce SSVEP with high signal-to-noise ratios (SNRs) using composite color lights flickering near or above its critical flicker...
We demonstrate how to measure accurately the transmission matrix of a complex medium. With this information, we show how to focus light, recover an image, and even perform efficient reconstruction of a sparse object.
We propose a new geometric super resolving approach that overcomes the geometric resolution reduction caused due to the spatially large pixels of the detection array while the improvement process is obtained by applying axial scanning and a phase retrieving procedure. In the scanning process, several images are captures corresponding to focus made on different axial plains. By applying iterative Gerchberg-Saxton...
A novel platform suitable for fundamental investigations of light propagation through micro- and nano-structures will be discussed. This platform is based on a dielectric multilayer that sustains Bloch surface waves (BSWs). BSWs are electromagnetic surface waves excited at the interface between a truncated periodic dielectric multilayer and a surrounding media. The modification of the top surface...
We describe spatial coherence encoding in an LED array microscope, where a programmable array of LEDs is used in the source plane to pattern the spatial coherence of the illumination. Using this simple setup, we demonstrate various imaging functionality enabled by coherence manipulation: bright-field, darkfield, 3D phase imaging, and enhanced resolution. Our synthetic large NA imaging is an extension...
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