There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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Flow The Psychology Of Optimal Experience

This paper presents a new reflectance model for rendering computer synthesized images. The model accounts for the relative brightness of different materials and light sources in the same scene. It describes the directional distribution of the reflected light and a color shift that occurs as the reflectance changes with incidence angle. The paper presents a method for obtaining the spectral energy distribution of the light reflected from an object made of a specific real material and discusses a procedure for accurately reproducing the color associated with the spectral energy distribution. The model is applied to the simulation of a metal and a plastic.

A reflectance model for computer graphics

Methods of manufacturing a liquid crystal device including depositing a layer of liquid crystal material on a substrate and imprinting a pattern on the layer of liquid crystal material using an imprint template are disclosed. The liquid crystal material can be jet deposited. The imprint template can include surface relief features, Pancharatnam-Berry Phase Effect (PBPE) structures or diffractive structures. The liquid crystal device manufactured by the methods described herein can be used to manipulate light, such as for beam steering, wavefront shaping, separating wavelengths and/or polarizations, and combining different wavelengths and/or polarizations.

Virtual and augmented reality systems and methods

In this work, we report the set-up and results of the Liver Tumor Segmentation Benchmark (LITS) organized in conjunction with the IEEE International Symposium on Biomedical Imaging (ISBI) 2016 and International Conference On Medical Image Computing Computer Assisted Intervention (MICCAI) 2017. Twenty four valid state-of-the-art liver and liver tumor segmentation algorithms were applied to a set of 131 computed tomography (CT) volumes with different types of tumor contrast levels (hyper-/hypo-intense), abnormalities in tissues (metastasectomie) size and varying amount of lesions. The submitted algorithms have been tested on 70 undisclosed volumes. The dataset is created in collaboration with seven hospitals and research institutions and manually reviewed by independent three radiologists. We found that not a single algorithm performed best for liver and tumors. The best liver segmentation algorithm achieved a Dice score of 0.96(MICCAI) whereas for tumor segmentation the best algorithm evaluated at 0.67(ISBI) and 0.70(MICCAI). The LITS image data and manual annotations continue to be publicly available through an online evaluation system as an ongoing benchmarking resource.

The Liver Tumor Segmentation Benchmark (LiTS)

Broadband achromatic metalens and meta-deflector based on integrated metasurface

View management techniques are commonly used for labelling of objects in augmented reality environments. Combining with image analysis, search space and adaptive representations, they can be utilized to achieve desired labelling tasks. However, the evaluation of different search space methods on labelling are still an open problem. In this paper, we propose an image analysis based view management method, which first adopts the image processing to superimpose 2D labels to the specific object. We then conduct three search space methods to an augmented reality scenario. Without the requirements of setting rules and constraints for occlusion among the labels, the results of three search space methods are evaluated by using objective analysis of related parameters. The evaluation results indicate that different search space methods could generate different time costs and occlusion, thereby affecting the final labelling effects.

Evaluation of labelling layout methods in augmented reality

In this paper, a switchable micro-focusing Fresnel device based on phase-change materials (PCMs) is proposed, which can selectively display the functions of transmission and reflection without the use of mechanical adjustment on micro scale. The switchable function is realized by combining Fresnel structure with PCM. A four-level switchable Fresnel device consisting of a typical PCM Ge3Sb2Te6 (GST-326) is designed to focus light into a focal length of 30 µm at wavelength of 3.1 µm. The optical performance of the switchable device has been analyzed by using finite-difference time-domain (FDTD) method, showing bright convergence point near pre-designed focal length with focusing efficiencies larger than 18%, depth of focus (DOF) less than 4.65 µm and the full width at half-maximum (FWHM) not larger than 1.30 µm. Furthermore, by precisely manipulating the variation of PCM thickness, we also obtain a device that possesses the characteristics of a transmission-reflection focusing beam splitter. The devices show good potential for the combination of traditional binary optical devices and PCM to produce new functions, and provides a promising innovative approach for miniature focal length switching device.

Design and modeling of a transmission and reflection switchable micro-focusing Fresnel device based on phase-change materials.

Recently, in the field of surgical visualization, augmented reality technology has shown incomparable advantages in oral and maxillofacial surgery. However, the current augmented reality methods need to develop personalized occlusal splints and perform secondary Computed Tomography (CT) scanning. These unnecessary preparations lead to high cost and extend the time of preoperative preparation. In this paper, we propose an augmented reality surgery guidance system based on 3D scanning. The system innovatively designs a universal occlusal splint for all patients and reconstructs the virtual model of patients with occlusal splints through 3D scanning. During the surgery, the pose relationship between the virtual model and the markers is computed through the marker on the occlusal splint. The proposed method can replace the wearing of occlusal splints for the secondary CT scanning during surgery. Experimental results show that the average target registration error of the proposed method is \(\text{1.38}\pm \text{0.43 mm}\), which is comparable to the accuracy of the secondary CT scanning method. This result suggests the great application potential and value of the proposed method in oral and maxillofacial surgery.

Novel Augmented Reality System for Oral and Maxillofacial Surgery.

Holographic display has been considered as a promising display technology. Currently, low-speed generation of holograms with big holographic data is one of crucial bottlenecks for three dimensional (3D) dynamic holographic display. To solve this problem, the acceleration method computation platform is presented based on look-up table point source method. The computer generated holograms (CGHs) acquisition is sped up by offline file loading and inline calculation optimization, where a pure phase CGH with gigabyte data is encoded to record an object with 10 MB sampling data. Both numerical simulation and optical experiment demonstrate that the CGHs with 1920×1080 resolution by the proposed method can be applied to the 3D objects reconstruction with high quality successfully. It is believed that the CGHs with huge data can be generated by the proposed method with high speed for 3D dynamic holographic display in near future.

Yongtian Wang

Papers

Broadband achromatic metalens and meta-deflector based on integrated metasurface

Evaluation of labelling layout methods in augmented reality

Design and modeling of a transmission and reflection switchable micro-focusing Fresnel device based on phase-change materials.

Novel Augmented Reality System for Oral and Maxillofacial Surgery.

The optimizations of CGH generation algorithms based on multiple GPUs for 3D dynamic holographic display