Kazuhisa Yanaka

Integral photography using hexagonal fly's eye lens and fractional view

We have developed a new integral photography (IP) system that incorporates a hexagonal flys eye lens sheet to create a fractional view. In a fractional view, the ratio between the lens and pixel pitches of the IP image is intentionally chosen to be a non-integer so that the directions of all the rays emitted from each pixel on the LCD panel located behind the sheet become quasi-random. Creating a fractional view simultaneously increases the effective number of individual views and the resolution of each view. Furthermore, initial production costs can be decreased because the fractional view can be created using inexpensive off-the-shelf lens sheets together with a variety of common flat panel displays that have different pixel pitches. The difference in pitch is compensated for using computer software. The problem is that fractional views were originally only used with lenticular-lens based displays that have a horizontal parallax; therefore, some extension is necessary if fractional views are to be used with displays that have a full parallax. Furthermore, a typical flat panel display, such as an LCD, consists of RGB subpixels that are in positions that are slightly shifted relative to each other. We have developed a way of extending existing fractional views in order to cope with the full parallax obtained by a flys eye lens sheet and the pixel shift. We demonstrated that good binocular vision can be obtained when using two hexagonal flys eye lens sheets that were made without any relation to an LCD.

Integral photography suitable for small-lot production using mutually perpendicular lenticular sheets and fractional view

We developed an integral photography (IP) system that is suitable for small-lot production and is, in principle, applicable to animation. IP is an ideal 3D display method because users can see stereoscopic 3D images from arbitrary directions. However, IP is less popular than lenticular display using only the horizontal parallax, probably because the initial cost of designing and producing a flys eye lens is very high. We used two technologies to solve this problem. First, we used two mutually perpendicular lenticular sheets instead of a flys eye lens sheet. A lenticular sheet is much less expensive than a flys eye lens because it is easier to produce. Second, we used the fractional view method, in which the ratio of lens pitch to pixel pitch is not limited to simple integer ratios, which means that no custom-made lenticular lens is necessary. However, the original fractional view method is applicable only to horizontal parallax. We made it applicable to both horizontal and vertical parallaxes by using two mutually perpendicular lenticular sheets. In addition, we developed a simple technique for generating dedicated synthesized images for IP.

2x3D: real time shader for simultaneous 2D/3D hybrid theater

In recent years, stereoscopic displays paired with glasses that make 3D movies possible are a popular research topic and continue to become widespread. These stereoscopic displays can create the appearance of three-dimensional images by simply wearing a pair of special glasses; however, when seen with the naked eye, the images for the left and right eyes can be seen overlapping.

Optimization of Size of Pixel Blocks for Orthogonal Transform in Optical Watermarking Technique

We previously proposed a novel technology with which the images of real objects with no copyright protection could contain invisible digital watermarking, using spatially modulated illumination. In this “optical watermarking” technology, we used orthogonal transforms, such as a discrete cosine transform (DCT) or a Walsh-Hadamard transform (WHT), to produce watermarked images, where 1-b binary information was embedded into each pixel block. In this paper, we propose an optimal condition for a technique of robust optical watermarking that varies the size of pixel blocks by using a trade-off in the efficiency of embedded watermarking. We conducted experiments where 4 × 4, 8 × 8, and 16 × 16 pixels were used in one block. A detection accuracy of 100% was obtained by using a block with 16 × 16 pixels when embedded watermarking was extremely weak, although the accuracy did not necessarily reach 100% by using blocks with 4 × 4 or 8 × 8 pixels under the same embedding conditions. We also examined the effectiveness of using a Haar discrete wavelet transform (Haar DWT) as an orthogonal transform under the same experimental condition, and the results showed that the accuracy of detection was slightly inferior to DCT and WHT under very weak embedding conditions. The results from experiments revealed the effectiveness of our new proposal.

ScritterHDR: multiplex-hidden imaging on high dynamic range projection

We propose a system that enables the display of multiplex-hidden images for selected users with highly accessible polarizing filters. This system requires no electronic devices for users. It is designed with high dynamic range (HDR) projection technology and realizes the display of multiplexed content with HDR. Recently, research into HDR projection technology has made a lot of progress. Such HDR technology can realize digital cinemas with high quality and clear visibility of digital content even in daylight. Thus, we expect the system to extend the expression of digital content and to be applicable to future cinemas, digital signage and virtual environments.

Tolerance Evaluation for Defocused Images to Optical Watermarking Technique

In this paper, we describe a new aspect to evaluating the robustness of the optical watermarking technique, which is a unique technology that can add watermarked information to object image data taken with digital cameras without any specific extra hardware architecture. However, since this technology uses light with embedded watermarked information, which is irradiated onto object images, the condition of taking a picture with digital cameras may affect the accuracy with which embedded watermarked data can be detected. Images taken with digital cameras are usually defocused, which occurs under non-optimal conditions. We evaluated the defocusing in images against the accuracy with which optical watermarking could be detected. Defocusing in images can be expressed with convolution with a line-spread function (LSF). We used the value of full-width at half-maximum (FWHM) of a Gaussian function as the degree to which images were defocused, which could approximate LSF. We carried out experiments where the accuracies of detection were evaluated as we varied the degree to which images were defocused. The results from the experiments revealed that optical watermarking technology was extremely robust against defocusing in images.

Moving integral photography using a common digital photo frame and fly's eye lens

A digital photo frame (DPF) has evolved from a tool for displaying favorite photographs to a device that displays videos. The next advancement is the introduction of the stereoscopic display. Although a DPF with a stereoscopic display has already been released on the market, it only enables horizontal parallax. In this paper, we describe a different type of 3D display system based on a DPF and a flys eye lens, both of which are commercially available. Our system enables not only horizontal but also vertical parallax because integral photography (IP) is used. IP was thought to be a technology of the future because a very high resolution LCD and a dedicated flys eye lens were believed to be necessary. However, the extended fractional view (EFV) method[1] proposed by one of the authors enabled freely combining a wide range of LCDs and the relatively inexpensive flys eye lenses available on the market to produce IP. It greatly contributed to the initial cost reduction. This new system uses the EFV method. The main problem is how to supply good content. Therefore, we also developed a method of producing the animation of IP by using CG technology.

P-9: Extended Fractional View Integral Imaging Using Slanted Fly's Eye Lens

A new 3D display system based on integral imaging technology was developed by combining two methods. One is the extended fractional view method in which various LCDs and flys eye lenses can be used together, and the other is the slanted lens array method that can reduce the moire pattern.

Optical watermarking technique robust to geometrical distortion in image

This paper presents an optical watermarking technique that is robust against geometrical distortion in images by using spatially modulated illumination. It can protect “analog” objects like pictures painted by artists from having photographs taken of them illegally in museums. Illegally captured images in practical situations may contain various distortions, and embedded watermarks may be incorrectly detected. Geometrical distortion caused by the shooting angle that the objects are captured at is a particularly major problem. We carried out experiments to evaluate the robustness of watermarking images that were geometrically distorted, in which distortions were intentionally created by moving the position of the projector and the digital camera from right in front of the object. The accuracy of the extracted watermarking data was almost 100%, even if the shooting angle was inclined by about 20 degrees between the projector and digital camera, in both cases when a Discrete Cosine Transform (DCT) and a Walsh-Hadamard Transform (WHT) were used as the methods of embedding watermarks. We introduced rectangular mesh fitting and a technique of “bi-linear interpolation” based on the four nearest points to correct the distortions.

Real-time rendering for integral photography that uses extended fractional view

A real-time method for rendering integral photography (IP) that uses the extended fractional view technique is described. To make an IP image by using CG technology, hundreds of still pictures from different camera positions need to be taken, and the images have to be synthesized by using other software. This is because CG applications do not have a special rendering mode that is required for the extended fractional view approach when the directions of the rays are not uniform. Hence, considerable processing time is needed to synthesize one IP image using the method, which is not suitable for real-time applications such as games. Therefore, new high-speed rendering software was written using C++. It runs on a typical Windows PC. Its main function is to trace the path of each ray, which is emitted from each subpixel of a liquid crystal display (LCD) and refracted by a flys eye lens. A subpixel is used instead of a pixel because a pixel on a color LCD is made up of three subpixels, one each for red, green and blue, and their positions are different. If there is an object on either side of the extension line of the ray, the coordinates of the intersection are calculated, and visibility is determined by z-buffering. If the intersection is visible, the color is acquired and pasted on the subpixels of the LCD. I confirmed that a simple 3D moving object, which consists of several polygons, could be rendered at more than two frames per second, and a full-parallax moving image could be obtained by using IP.