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 10× 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.
On-chip holographic video is a convenient way to monitor biological samples simultaneously at high spatial resolution and over a wide field-of-view. However, due to the limited readout rate of digital detector arrays, one often faces a tradeoff between the per-frame pixel count and frame rate of the captured video. In this report, we propose a subsampled phase retrieval (SPR) algorithm to overcome the spatial-temporal trade-off in holographic video. Compared to traditional phase retrieval approaches, our SPR algorithm uses over an order of magnitude less pixel measurements while maintaining suitable reconstruction quality. We use an on-chip holographic video setup with pixel sub-sampling to experimentally demonstrate a factor of 5.5 increase in sensor frame rate while monitoring the in vivo movement of Peranema microorganisms.
Recent advances in bidirectional reflectance distribution function (BRDF) acquisitions have provided a novel approach for appearance measurement and analysis. In particular, since gloss appearance is dependent on the directional reflective properties of surfaces, it is reasonable to leverage the BRDF for gloss evaluation. In this paper, we investigate gloss appearance from both soft metrology and hard metrology. A psychophysical experiment was conducted for the gloss assessment of 47 neutral-color samples. In the evaluation of gloss perception from gloss meter measurements, we report several ambiguous correspondences in the medium gloss range. In order to analyze and explain this phenomenon, the BRDF was acquired and examined using a commercial BRDF measuring device. With an improved correlation-to-visual perception, we propose a two-dimensional gloss model by combining a parameter, the standard deviation of the specular lobe, from Ward's BRDF model with measured gloss values.
We propose a dictionary-based phase retrieval approach for monitoring in vivo biological samples based on lens-free on-chip holographic video. Our results present a temporal increase of 9× with 4 × 4 sub-sampling.
Diffuse coarseness (graininess) and glint impression (sparkle) are two aspects of visual perception for special‐effect materials, including car finishes, etc. Previous work has shown that these two attributes become apparent when illuminated under two distinct illumination conditions: diffuse and unidirectional illumination respectively. The effect of glint impression has significant dependency on the viewing geometry. In this work, three psychophysical experiments were carried out, including diffuse coarseness assessment, glint impression assessment, and finding dimensions of glint space. In the experiments, one geometry for diffuse coarseness and three geometries for glint impression were designed. The three viewing geometries were designed according to a commercial device, BYK‐mac, so that the results were used to test the reliability of instrumental measurements. Based on the conclusions drawn from the psychophysical experiments, a further investigation on glint space was conducted using the multidimensional scaling technique. From the visual results, two dimensions, corresponding to two attributes, were extracted and were validated by the instrumental results. Bidirectional reflectance distribution function data were also adopted from another commercial device, Imaging Sphere from Radiant Vision Systems Inc., USA (originally RadiantZemax Inc.), to predict glint impression. Some promising results were obtained.
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