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)

Image projection systems are widely used in modern applications. To enlarge the field of view (FOV), especially for curved-surface projection, multiple projectors are used to display different images, and the images are spliced with increasing system volume. For a single projector, chromatic aberration caused by the edge of the complex optical system is unavoidable during the enlargement of view angle. We propose and designed a projection system using a metallic nanorod antenna array metasurface with polarization control to enlarge the FOV with a slim structure and realize achromatic multicolor display on curved surfaces. With far-field computational simulations, three output images were stitched into a picture on a hemispherical surface, and the field diffraction angle was found to be three times as large as direct projection, approaching 270 deg theoretically. With the derived formula, the achromatic effect can be realized by optimizing incident angle parameters at different wavelengths, with an angular dispersion of <6.6  ×  10  −  5  deg  /  nm, which is sufficient for multicolor display. The system greatly reduces the complexity of optical design with multicolor display and shows potential for the miniaturization of curved-surface projection with the metasurface.

Design of an achromatic projection system on a curved surface for enlarging view using polarization control metasurface

In this paper, we review the background of physical reality, virtual reality, and some traditional mixed forms of them. Based on the current knowledge, we propose a new unified concept called symmetrical reality to describe the physical and virtual world in a unified perspective. Under the framework of symmetrical reality, the traditional virtual reality, augmented reality, inverse virtual reality, and inverse augmented reality can be interpreted using a unified presentation. We analyze the characteristics of symmetrical reality from two different observation locations (i.e., from the physical world and from the virtual world), where all other forms of physical and virtual reality can be treated as special cases of symmetrical reality.

Symmetrical Reality: Toward a Unified Framework for Physical and Virtual Reality

Retinal projection display (RPD) is a research hotspot in the field of near-eye display (NED), which has a long depth of field and is able to overcome the vergence-accommodation conflict (VAC) because of the principle of Maxwellian view. However, the existing problems of RPD, such as small field of view (FOV) and large volume heavy weight, restrict its application and development. In this paper, an RPD system based on micro-electro-mechanical system (MEMS) and conicoid curved semi-reflective mirror is proposed in order to realize a large FOV with compact structure and light weight. The MEMS used is a kind of biaxial scanning mirror, which works in coordination with RGB laser diodes for the sake of scanning a two-dimensional image in a specific direction with high illuminance and high resolution. The conicoid curved semi-reflective mirror is used to project the image onto the retina and form a large FOV with a suitable eye relief distance (ERF), meanwhile to keep the external object visible. The combination of MEMS, RGB laser diodes and conicoid curved semi-reflective mirror retains compact size factor suitable for wearable function. The performance of the proposed RPD is quantitatively analyzed. And the key performance is set forth in detail as follows. The FOV is 70° horizontal (H) × 40° vertical (V), ERF is 30mm. And the MTFs are discussed as well. The proposed RPD system realizes a large FOV, a long depth cue and high performance with compact size, which can be further applied in the next-generation optical see-through NED.

Retinal projection display system based on MEMS scanning projector and conicoid curved semi-reflective mirror

Single point active alignment method (SPAAM) has become the basic calibration method for optical-see-through head-mounted displays since its appearance. However, SPAAM is based on a simple static pinhole camera model that assumes a static relationship between the user's eye and the HMD. Such theoretic defects lead to a limitation in calibration accuracy. We model the eye as a dynamic pinhole camera to account for the displacement of the eye during the calibration process. We use region-induced data enhancement (RIDE) to reduce the system error in the acquisition process. The experimental results prove that the proposed dynamic model performs better than the traditional static model, and the RIDE method can help users obtain a more accurate calibration result based on the dynamic model, which improves the accuracy significantly compared to the standard SPAAM.

[POSTER] An Accurate Calibration Method for Optical See-Through Head-Mounted Displays Based on Actual Eye-Observation Model

Endoscopic images frequently have image quality problems due to the limitations of surgical instruments and the impact of surgical operations, such as uneven illumination, smogginess and color deviation For deep learning based on enhancement methods, independent training lacks sufficient defect images and generalization capability, and combined training with mixture of data cannot identify diverse specific tasks To address these issues, we propose a general method based on pre-trained generative adversarial network with a specified transfer learning strategy to obtain high-quality images Initially, we independently train a standard network based on a universal task, eg, uneven illumination, where a pre-trained model is extracted as a backbone with partially shared generator Then, we transfer the backbone to more potential image enhancement tasks Experiments on uneven illumination, smogginess, and color deviation indicate that the model successfully shares common features of high-quality images and responds specifically to different defects as well

Yongtian Wang

Papers

Design of an achromatic projection system on a curved surface for enlarging view using polarization control metasurface

Symmetrical Reality: Toward a Unified Framework for Physical and Virtual Reality

Retinal projection display system based on MEMS scanning projector and conicoid curved semi-reflective mirror

[POSTER] An Accurate Calibration Method for Optical See-Through Head-Mounted Displays Based on Actual Eye-Observation Model

A General Endoscopic Image Enhancement Method Based on Pre-trained Generative Adversarial Networks