Digital image correlation assisted absolute phase unwrapping.

This paper presents an absolute phase unwrapping method for high-speed three-dimensional (3D) shape measurement. This method uses three phase-shifted patterns and one binary random pattern on a single-camera, single-projector structured light system. We calculate the wrapped phase from phase-shifted images and determine the coarse correspondence through the digital image correlation (DIC) between the captured binary random pattern of the object and the pre-captured binary random pattern of a flat surface. We then developed a computational framework to determine fringe order number pixel by pixel using the coarse correspondence information. Since only one additional pattern is used, the proposed method can be used for high-speed 3D shape measurement. Experimental results successfully demonstrated that the proposed method can achieve high-speed and high-quality measurement of complex scenes.

Semi-Global Matching Assisted Absolute Phase Unwrapping.

Measuring speed is a critical factor to reduce motion artifacts for dynamic scene capture. Phase-shifting methods have the advantage of providing high-accuracy and dense 3D point clouds, but the phase unwrapping process affects the measurement speed. This paper presents an absolute phase unwrapping method capable of using only three speckle-embedded phase-shifted patterns for high-speed three-dimensional (3D) shape measurement on a single-camera, single-projector structured light system. The proposed method obtains the wrapped phase of the object from the speckle-embedded three-step phase-shifted patterns. Next, it utilizes the Semi-Global Matching (SGM) algorithm to establish the coarse correspondence between the image of the object with the embedded speckle pattern and the pre-obtained image of a flat surface with the same embedded speckle pattern. Then, a computational framework uses the coarse correspondence information to determine the fringe order pixel by pixel. The experimental results demonstrated that the proposed method can achieve high-speed and high-quality 3D measurements of complex scenes.

One-time ray-tracing optimization method and its application to the design of an illuminator for a tube photo-bioreactor.

This study details a one-time ray-tracing optimization method for the optimization of LED illumination systems [S.-C. Chu and H.-L. Yang, "One-time ray-tracing method for the optimization of illumination system," in Proceedings of International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN, 2013), 87692M]. This method optimizes the performance of illumination systems by modifying the light source's radiant intensity distribution with a freeform lens, instead of modifying the illumination system structure. Because illumination system structures are unchanged in the design process, a designer can avoid the common problems faced when designing illumination systems, i.e., the repeated and time-consuming ray-tracing process when optimizing the illumination system parameters. The easy approaches of the proposed optimization method to sample the target illumination areas and to divide the light source radiant intensity distribution make the proposed method can be applied to both direct-lit and non-direct-lit illumination systems. To demonstrate the proposed method, this study designs an illuminator for a tube photo-bioreactor using the proposed one-time ray-tracing method. A comparison shows that in the designing of the photo-bioreactor, tracing all rays one time requires about 13 hours, while optimizing the light source's radiant intensity distribution requires only about twenty minutes. The considerable reduction in the ray-tracing time shows that the proposed method is a fast and effective way to design illumination systems.

Portable high-resolution automated 3D imaging for footwear and tire impression capture.

The forensic science community raised the need for improved evidence recognition, collection, and visualization analytical instrumentation for field and laboratory use. While the 3D optical techniques for imaging static objects have been extensively studied, there is still a major gap between current knowledge and collecting high-quality footwear and tire impression evidence. Among optical means for 3D imaging, digital fringe projection (DFP) techniques reconstruct 3D shape from phase information, achieving camera-pixel spatial resolution. This paper presents a high-resolution 3D imaging technology using DFP techniques dedicated to footwear and tire impression capture. We developed fully automated software algorithms and a graphical user interface (GUI) that allow anyone without training to operate for high-quality 3D data capture. We performed accuracy evaluations and comparisons comparing with the commercial high-end 3D scanner and carried out qualitative tests for various impressions comparing with the current practices. Overall, our technology achieves similar levels of accuracy and resolution with a high-end commercially available 3D scanner, while having the merits of being (1) more affordable; (2) much easier to operate; and (3) more robust. Compared with the current practice of casting, our technology demonstrates its superiority because it (1) is non-destructive; (2) collects more evidence detail than casts, especially when an impression is fragile; (3) requires less time and money to collect each piece of evidence; and (4) results in a digital file that can easily be shared with other examiners.

[Analysis of genetic characteristics of ECHO6 virus isolated from an epidemic outbreak of encephalitis in Longyan, China].

This study aimed to analyze the etiology of the encephalitis outbreak in Longyan, Fujian Province, China in 2010, in order to provide valuable information for this prevention and control of this disease. Pathogens were confirmed from cerebrospinal fluid samples with fluorescent RT-PCR, virus isolation (RD cells), and neutralization tests. Then, the VP1 fragments or whole genome nucleotide sequences were determined for four virus strains using PCR. Homology was assessed using the MegAlign software, and a phylogenetic evolutionary tree was drawn using Mega 4.0 software. The results confirmed that the etiology of the outbreak was the ECHO6 intestinal virus, and the nucleotide sequence of the VP1 segment indicated that the C2 subtype was responsible. The genome sequence consisted of 7407 nucleotides, and resembled the genome of other ECHO and CoxB viruses with homology levels of 78.5%-87.3%. The encephalitis outbreak in Longyan in 2010 was caused by the ECHO6 C2 subtype intestinal virus, and its complete genome sequence length is similar to the standard strain (U16283) with a sequence homology of 80.4%.

Modulation of the polarization state of light using a weak anisotropic thin film.

The polarization state of light is modulated by an anisotropic thin film. An anisotropic MgF(2) film is deposited onto a plate that is put in contact with a BK7 prism to form a BK7 prism/film/air configuration. It is shown that the polarization state of reflected light can be easily modulated from a linear state to a circular state by rotating the thin-film plate.