|Publication number||USRE39979 E1|
|Application number||US 11/311,888|
|Publication date||Jan 1, 2008|
|Filing date||Dec 20, 2005|
|Priority date||Jun 6, 2003|
|Also published as||US6885512, US20040246612|
|Publication number||11311888, 311888, US RE39979 E1, US RE39979E1, US-E1-RE39979, USRE39979 E1, USRE39979E1|
|Original Assignee||Minebea Co., Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (26), Classifications (11), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates to a color wheel suitable for use as a filter element of a time-share light dispersing device, and to a color wheel incorporated in a color wheel assembly making up a projection-type image display apparatus.
2. Description of the Related Art
Color composition in a projection-type image display apparatus has conventionally been accomplished commonly by a method, such as: a single-panel method, in which one light valve element adapted to control light amount per pixel thereby creating an image is used to disperse each pixel into red (R), green (G), and blue (B) lights; and a three-panel method, in which three light valve elements dedicated to R, G and B lights, respectively, are used to produce in parallel R, G and B images, and then the three images thus produced are composed. Recently, as a light valve element capable of fast switching, such as a ferroelectric liquid crystal display element or a digital micro mirror device, is increasingly coming into practical use, a time-sharing single-panel method is widely used. In the time-sharing single-panel method, R, G and B lights are caused to sequentially impinge on one light valve element, the light valve element is driven in synchronization with switching-over of the R, G and B lights thereby producing R, G and B images in a time series manner, and the images thus produced are projected onto a screen, or the like. Here, color composition of the images is accomplished by a viewer due to an afterimage effect occurring at a sense of vision. In the time-sharing single-panel method, reduction in both dimension and weight of the apparatus, which is a feature of a single-panel method, can be achieved by employing a relatively simple optical system, and therefore the time-sharing single-panel method is favorable for realizing inexpensive fabrication of a projection-type image display apparatus. In such an image display apparatus, a color wheel is preferably used as a filter element of a time-share light dispersing device to sequentially disperse light emitted from a white light source into R, G and B lights having respective wavelength bands in a time-sharing manner (refer to, for example, Japanese Patent Application Laid-Open No. H06-347639).
Adjacent filter sectors are required to abut each other precisely and tightly unless achromatic areas which do not constitute any filter sectors are intentionally disposed. This is because if the adjacent filter sectors do not abut each other precisely and tightly, a gap is generated between the adjacent filter sectors, and light passing the gap fails to definitely determine its color thus resulting in not fully contributing to forming an image. When filters are formed by an evaporation method or a sputtering method, a metal mask formed of a metallic thin plate and having openings corresponding to the filter sectors is preferably used for demarcating the filter sectors. The metal mask is first guided mechanically, for example, with a positioning pin, and then finally lined up by viewing, for example, through a microscope, the peripheries of filter sectors of one kind already formed and the openings of the metal mask.
However, the following problem is found in the positioning technique described above. It occasionally happens at the process of forming the filter sectors due to the thickness of the metal mask that as shown in
In order to overcome the problem, for example, Japanese Patent Application Laid-Open No. H11-222664 discloses a metal mask with openings, in which the sidewalls of the openings are inclined with respect to the metal mask surfaces such that the openings have an increased area at one of the surfaces facing an evaporation source so that particles from the evaporation source come into the openings with reduced restriction thereby better achieving uniform film formation within the openings.
The aforementioned Japanese Patent Application Laid-Open No. H06-347639 discloses that filter sectors are desired to abut each other unless achromatic areas which do not constitute any filter sectors are intentionally disposed, but does not teach how it can be achieved. Also, the aforementioned Japanese Patent Application Laid-Open No. H11-222664 indicates a method that is anticipated to be good to a certain degree for clearly demarcating a boundary between filter sectors provided that an optimum inclination angle of the sidewalls surely exists and can be obtained somehow which allows a film to be formed uniform in thickness all the way up to the peripheries of filter sectors. The optimum inclination angle of the sidewalls, however, must be obtained theoretically and experimentally based on various considerations, such as a film material method and conditions of film formation, a desired film thickness, a metal mask thickness, and the like, and therefore the method disclosed therein cannot be readily applied to fabrication of a color wheel.
The present invention has been made in light of the above problems, and it is an object of the present invention to provide a color wheel, in which light impinging on an area corresponding to a boundary between adjacent filter sectors can be efficiently utilized even if the adjacent filters are not precisely positioned with respect to each other, and which is incorporated in a color wheel assembly for use in an image display apparatus.
In order to achieve the object, according to a first aspect of the present invention, a color wheel comprises: a disk-like substrate made of a light-transmittable material; plural kinds of filter sectors formed on a surface of the substrate and functioning to selectively transmit lights having respective different wavelength bands; and a plurality of light deflecting means to change an optical path of light impinging on an area corresponding to a boundary between adjacent filter sectors so as to guide the light into one of the adjacent filter sectors. Consequently, light impinging on the area corresponding to the boundary between the adjacent filter sectors can be surely dispersed into a predetermined color, even if the boundary is not provided with a complete dielectric multi-layer film having a specified thickness, or even if the adjacent filter sectors are not precisely positioned with respect to each other.
In the first aspect of the present invention, the light deflecting means may be lens structures formed integrally with the substrate. Consequently, the light deflecting means can be formed precisely by using a usual method for fabricating an optical element.
In the first aspect of the present invention, substrate may consist of a lower refractive index portion and a higher refractive index portion, and the light deflecting means may be lens structures constituted by the higher refractive index portion. Consequently, the color wheel has flat surfaces, and therefore does not cause an increased noise wind level due to its high-speed rotation.
According to a second aspect of the present invention, the color wheel, together with a motor to rotate the color wheel, may comprise a color wheel assembly. Consequently, the color wheel assembly can utilize white light efficiently.
According to a third aspect of the present invention, the color wheel assembly composed of the color wheel may be employed in an image display apparatus. Consequently, the image display apparatus can provide a display image of a high visual quality due to the efficient utilization of white light.
The present invention will hereinafter be described with reference to the accompanying drawings.
A first embodiment of the present invention will be described with reference to
The lens structures 5a, 5b are formed integrally with the substrate 1 by using a glass or resin processing technique with a high accuracy, that is employed for fabricating an optical element, such as a lens or a diffraction grating, or fabricating a substrate of an optical information recording medium, such as a CD or a DVD. Specifically, the lens structures 5a, 5b can be preferably formed, in case of the substrate 1 made of a glass material, by, for example, hot press-molding, and in case of the substrate 1 made of a resin material, by die-forming (e.g., casting, injection-molding, and compression-molding). Depending on the required dimension or optical properties such as a refractive index, the lens structures 5a, 5b may alternatively be formed separately from the substrate 1 and attached to the substrate 1 by adhesion, or formed such that a grooved is formed on the substrate 1 along the ideal demarcation line W by, for example, etching, and then the groove portion is heated up to a temperature exceeding its fusing or softening point thereby forming light deflecting surfaces. The lens structures 5a, 5b in
A second embodiment of the present invention will be described with reference to
The substrate 11 may be formed such that a low refractive index material for the main portion 19 and a high refractive index material for the lens structures 15a, 15b are appropriately selected out of various optical glass or plastic materials taking design conditions into consideration, and are processed by, for example, insert-molding, which is used for fabricating a composite optical element and the like. For example, BK-type optical glass having a refractive index of about 1.5 may be selected as a low refractive index material, and LAK-type optical glass having a refractive index of about 1.7 may be selected as a high refractive index material. The lens structures 15a, 15b in
Now, a description will be made on a color wheel assembly incorporating a color wheel according to the present invention. Referring to
Further, a discussion will be made on an image display apparatus which includes a color wheel assembly incorporating a color wheel according to the present invention. Referring first to
Referring now to
It is evident that those skilled in the art may now make numerous modifications and variations without departing from the inventive concepts. For example, in the aforementioned image display apparatuses 70, and 80, respective light valve elements 73, and 86 and 87 are of reflection type, but may alternatively be of transmission type, such as liquid crystal light valves. Also, it is obvious that any optical systems or control systems can be optionally employed in the image display apparatuses 70, 80. Consequently, it is to be understood that the present invention is by no means limited to the specific embodiments described above but encompasses all changes and modifications which will become possible within the scope of the appended claims.
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|U.S. Classification||359/891, 362/293, 348/743, 356/418, 359/885|
|International Classification||G03B21/00, G02B5/20, G02B7/00, G02B26/00|
|Sep 24, 2008||FPAY||Fee payment|
Year of fee payment: 4
|Sep 26, 2012||FPAY||Fee payment|
Year of fee payment: 8