Hitachi, Ltd.

Hitachi Video and Information System, Inc.

Shuichi Sakamoto

Masanori Ogino

Yoshiaki Iwahara

Koichi Shibata

Shoji Kuroda

Masaru Igawa

Takashi Itoh

Koichi Morita

Makoto Kamiya

Yukihiro Kobayashi

A video server for distributing a digitized video content includes a unit for determining whether or not a video content requested from a terminal is stored in the video server, a unit for issuing a transmission request to another server for transmitting the video thereto in accordance with the HTTP protocol when the video content requested from the terminal is not stored in the video server, and a unit for receiving the video content transmitted from the other video server in accordance with the HTTP protocol, and transmitting the video content to the terminal in accordance with IP multicast or HTTP protocol.

Video server for video distribution system

A video content transmitting system is provided in which a video content transmitting server among a plurality of servers is automatically determined as to which server can establish a network bandwidth of each of all routes for video content transmission to a proper address of a video content play terminal by using a network protocol usable by the terminal. Information of a network protocol and a network route bandwidth used between the server and terminal is stored at a protocol information manager and a bandwidth information manager. In response to a video content transmission request from a terminal, bandwidths necessary for the routes to the terminal are established and video contents are transmitted by using the network protocol usable by the terminal.

Video content transmitting system and method

In a network cache and a cache control method involving the transfer of a large volume of data as the time of reproduction of multimedia data including video data, a stabilized data transfer is made by eliminating the waste of cached data or a useless cache processing which may be caused by the interruption of a user's operation. When a data transfer request from a user terminal connected to a local network is made to a server existing on the internet, a user request processing program starts a cache program. The cache program performs a cache processing independently of the data delivery to the requesting user terminal by the user request processing program so that even if the user's request is interrupted, the storage of transferred data into a cache file is performed without ceasing. Also, a required bit rate for data made an object of transfer is analyzed for comparison with a network throughput between the server and the network cache. When the network throughput is larger, the caching of transferred data is not performed so that the discard of data having been cached is not caused. Thereby, it is possible to prevent the cache hit rate from being lowered.

Method for continuing data transfer to network cache from server without transferring said data to user terminal irrespective of user interruption of the data transferring request

A rear projection type display system with a transmissive screen. A transparent reinforcing plate is coupled to a lenticular sheet of the screen on the light output side by a connective member to broaden the horizontal diverging angle by 60 degrees or more to the right and left sides. The duty factor of a black stripe formed on the lenticular sheet is set to 60% or more so improve the contrast of an image. The diverging angle at each point of a vertically-diffusing lens for diverging light in the vertical direction is modulated in accordance with the height of each point to offer a proper visual angle range in the vertical direction.

Rear projection type display system

A multi-screen projector having unit module projectors stacked at two higher and lower stages, each unit module projector having a screen with a Fresnel sheet unit, a prism sheet unit, and a lenticular sheet unit. By the functions of the Fresnel sheet unit and the prism sheet unit, main output light from higher and lower screens is converged to substantially the same target point. Only one type of metal molds is required for the Fresnel sheet unit as well as the prism sheet unit, thereby reducing the manufacturing cost of the multi-screen projector.

Multi-screen projector

The object of the invention is to provide a large-screen projection-type display using a transmission-type screen, wherein the transmission-type screen is formed of two or more sheets 4, 7, is tilted toward the viewer's side with a small gap kept between the sheets, and is stable relative to the temperature and moisture change of the environment. The front sheet 4 provided on the viewer's side and the Fresnel sheet 7 provided on the projection source side are tilted forward by about 7.degree. toward the viewers. The springs 10 are extended through wires 9 to exert the tension on the front sheet 4 in the vertical direction. At the same time, the springs exert a pressure on the Fresnel sheet 7 in the vertical direction.

Growing community of inventors

Yokohama, Japan

Shuichi Sakamoto