Optical: systems and elements – Projection screen – Unitary sheet comprising plural refracting areas
Reexamination Certificate
2002-05-13
2004-11-23
Mahoney, Christopher (Department: 2851)
Optical: systems and elements
Projection screen
Unitary sheet comprising plural refracting areas
C359S460000, C359S628000
Reexamination Certificate
active
06822792
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet or film for use for a projection screen, a projection screen, and a projection display device, and a light diffusion sheet or film and a projection screen using the light diffusion sheet or film, each of which is suitable for being viewed by having obliquely projected thereon an image from an image light source having a cell structure such as an LCD (Liquid Crystal Display Device), or a DMD (Digital Micro-mirror Device).
2. Description of the Related Art
A rear-surface projection type projection display device using three CRTs of red, green, and blue as the image light source and using a transmission type projection screen as the projection screen is conventionally known. In general, the projection screen is constructed using a Fresnel lens sheet and a lenticular lens sheet, and it is the projection screen that is for the purpose of obtaining a diffusion surface having directionality by causing an image to be focused thereon through the use of an image light from a projector. And, as illustrated in
FIG. 10
, the projection screen
80
has a Fresnel lens sheet
81
having formed on the light emission or outgoing side a circular type Fresnel lens
81
b
and a lenticular lens sheet
82
that is disposed on the viewer side of that Fresnel lens
81
and has formed on the light incidence side a horizontal diffusion lenticular lens and has formed on the light emission side a black stripe.
And, the Fresnel lens has formed in the acrylic material at prescribed pitches grooves each of that has a prescribed angle and thereby has a function to condense onto the front surface the light rays that have been diffused from the image light in the form of radial rays.
Also, the lenticular lens is the one for obtaining principally a diffused light having directionality in the horizontal direction and has its cylindrical lenses regularly formed in one flat plane in the longitudinal direction lenses to thereby have a function to spread the light distribution property in the horizontal direction.
The projection screen that is used therein, ordinarily, is also only suitable for the projection in the parallel direction in regard to the projection method as well. Generally, for the projection of an image light with respect to the projection screen, the method is adopted that maximizes the focal distance by the use of a reflection mirror. However, in recent years, it has been being observed that the use purpose of the projection screen is increasing in number to a wide variety of use purposes for having people view an image that uses the projection screen. Following this, in regard to the projection method as well, there has been an increasing demand for a projection display device, etc. wherein an image is viewed by projecting the image directly onto the projection screen by projecting from an image light source having a cell structure such as an LCD, a DMD, etc.
If with the conventional system an image is obliquely projected onto the projection screen from the image light source as described above, the difference in size and shape, or the like, between the upper and the lower of the letter of the projected image on the projection screen occurs. This raised the basic problem that the image is very difficult for the viewer to see. For that reason, there had been made at a lot of quarters attempts to provide a projection screen and system enabling viewing by obliquely projecting the image onto the projection screen without lowering the quality level of the image, as one type of projection display device. Under these circumstances, the inventor of this application disclosed in the specification of his Japanese Patent Application Laid-Open No. 2000-180967 a projection screen and a projection display device that is a projection system which in a rear-surface projection type display upwardly or downwardly projects the image from an image light source toward the projection screen while maintaining the quality of the image at a level equal to that which is attained when projecting the image from the image light source in parallel directions with one another and in which a total-reflection prism is provided on the light incidence surface side of the projection screen.
However, since the above-described projection screen necessitates two sheets of lens systems,it is necessary to provide two production lines for manufacturing those respective lenses and, in addition, the operations for handling could not help becoming complicated. Also, since using a circular Fresnel lens or a circular-arc-like prism, there is the problem that continuous production is difficult.
SUMMARY OF THE INVENTION
Whereupon, a first object of the present invention is to provide a sheet or film for use for a projection screen, the projection screen, and a projection display device, and a production method for the sheet or film for use for the projection screen and the projection screen, each of which enables making the handling simple and also enables the performance of continuous production by a single production line.
On the other hand, regarding the projection display device, etc., for the purpose of enhancing the level of the viewer's visual recognition, the one wherein the light diffusion or film is used for the screen is known. As the light diffusion sheet or film, there are, for example, the one wherein concavities/convexities processing is performed on the surface of a light transmission film, the one wherein light diffusion fine particles are contained in the interior of a resin film, a lenticular lens sheet wherein circular-columnar lenses are parallel-disposed in one flat plane, etc. Also, the using of those sheets in combination two or three in number has also been performed. Each of those projection display devices is the one that aims to enhance the visual recognition by, utilizing the difference between the respective indexes of refraction of the film, the atmospheric air, the fine particles, etc., refracting the image light at the boundaries thereof in many directions, diffusing the image light into a wide range of area, and thereby causing it toward the viewer side.
However, that results in that by the sheet surface having formed thereon the light diffusion fine particles or the concavities and convexities the image light has been randomly reflected to cause the occurrence of many stray lights, followed by deterioration in the surface brightness, contrast, etc. of the display. Also, the light diffusion sheet or film that has the diffusion properties as a result of the concavities/convexities processing of the surface, because that diffusion property and transparency property have angle dependency, had the problem that the visual recognition varies depending upon the angle at which the viewer watches the screen. On the other hand, the light diffusion property of the light diffusion sheet or film leads also to increasing the scatter reflection of the external light, with the result that the contrast remarkably decreases, raising the problem that the image becomes likely to be out of focus. On that account, the present invention has a second object to provide a light diffusion sheet or film wherein the surface brightness does not decrease, nor does the contrast deteriorate; the angle dependency is less; and the scatter reflection of the external light is less, and a projection screen using that light diffusion sheet or film.
Further, in the above-described construction, there is the problem that the external light that had entered from the light outgoing surface side has been reflected by the incidence surface of the sheet, followed by the deterioration in the contrast. In addition, when attempting to cause the procurement of the properties with use only of the above-described random diffusion and the diffusion in the one-side surface lens, the upper limit of the gain is only to an extent of 3 and it is impossible to obtain a gain greater that that. On that account, the present invention has a third object to provide a light di
Dai Nippon Printing Co. Ltd.
Keefer Timothy J
Mahoney Christopher
Seyfarth Shaw LLP
LandOfFree
Sheet for use for projection screen, light diffusion sheet... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sheet for use for projection screen, light diffusion sheet..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sheet for use for projection screen, light diffusion sheet... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3344539