Holographic phase retrieval via Wirtinger flow: Cartesian form with auxiliary amplitude.

We propose a new gradient method for holography, where a phase-only hologram is parameterized by not only the phase but also amplitude. The key idea of our approach is the formulation of a phase-only hologram using an auxiliary amplitude. We optimize the parameters using the so-called Wirtinger flow algorithm in the Cartesian domain, which is a gradient method defined on the basis of the Wirtinger calculus. At the early stage of optimization, each element of the hologram exists inside a complex circle, and it can take a large gradient while diverging from the origin. This characteristic contributes to accelerating the gradient descent. Meanwhile, at the final stage of optimization, each element evolves along a complex circle, similar to previous state-of-the-art gradient methods. The experimental results demonstrate that our method outperforms previous methods, primarily due to the optimization of the amplitude.

Pixel-density enhanced integral three-dimensional display with two-dimensional image synthesis.

Integral three-dimensional (3D) displays can display naturally viewable 3D images. However, displaying 3D images with high pixel density is difficult because the maximum pixel number is restricted by the number of lenses of a lens array. Therefore, we propose a method for increasing the maximum pixel density of 3D images by optically synthesizing the displayed images of an integral 3D display and high-definition two-dimensional display using a half mirror. We evaluated the improvements in 3D image resolution characteristics through simulation analysis of the modulation transfer function. We developed a prototype display system that can display 3D images with a maximum resolution of 4K and demonstrated the effectiveness of the proposed method.

Roadmap on 3D integral imaging: sensing, processing, and display.

This Roadmap article on three-dimensional integral imaging provides an overview of some of the research activities in the field of integral imaging. The article discusses various aspects of the field including sensing of 3D scenes, processing of captured information, and 3D display and visualization of information. The paper consists of a series of 15 sections from the experts presenting various aspects of the field on sensing, processing, displays, augmented reality, microscopy, object recognition, and other applications. Each section represents the vision of its author to describe the progress, potential, vision, and challenging issues in this field.

From Focal Stack to Tensor Light-Field Display.

We propose a method of using a focal stack, i.e., a set of differently focused images, as the input for a novel light field display called a "tensor display." Although this display consists of only a few light attenuating layers located in front of a backlight, it can be viewed from many directions (angles) simultaneously without the resolution of each viewing direction being sacrificed. Conventionally, a transmittance pattern is calculated for each layer from a light field, namely, a set of dense multi-view images (typically dozens) that are to be observed from different directions. However, preparing such a massive amount of images is often cumbersome for real objects. We developed a method that does not require a complete light field as the input; instead, a focal stack composed of only a few differently focused images is directly transformed into layer patterns. Our method greatly reduces the cost of acquiring data while also maintaining the quality of the output light field. We validated the method with experiments using synthetic light field datasets and a focal stack acquired by an ordinary camera.

Effect of SI-591, a new class of cathepsin K inhibitor with peptidomimetic structure, on bone metabolism in vitro and in vivo.

SI-591[N-[1-[[[(1S)-3-[[(3S)-hexahydro-2-oxo-1H-azepin-3-yl]amino]-1-(1-methylethyl)-2,3-dioxopropyl]amino]carbonyl]cyclohexyl]-2-furancarboxamide] is an orally bioavailable compound that was synthesized as one of several unique peptidomimetic compounds without a basic group. This compound was found to have the ability to inhibit cathepsin K, a lysosomal cysteine protease. Cathepsin K is known to be expressed in osteoclasts and involved in bone loss processes. In this study, SI-591 was shown to inhibit the activity of various purified cathepsin molecules at nanomolar concentrations but had high selectivity for cathepsin K over other subtypes including B and L. SI-591 also decreased the level of CTX-I, a bone resorption marker, which was released from osteoclasts in vitro in a dose-dependent manner. The mobilization of calcium from the bones to the blood stream is known to increase in rats fed with a low calcium diet; SI-591 inhibited this increase in serum calcium level at an oral dose of 3mg/kg. Furthermore, SI-591 significantly decreased the level of CTX-I and DPD, bone resorption markers, at oral doses of 10mg/kg or less in ovariectomized rats, while it did not affect the level of BGP, a bone formation marker. In addition, SI-591 prevented bone mineral density loss in the lumber vertebrae and femurs in ovariectomized rats. These results suggest that SI-591 inhibits bone resorption without affecting osteoblast maturation. Therefore, SI-591, a novel cathepsin K inhibitor, could be a promising agent for the treatment of postmenopausal osteoporosis.