Patent Application
20060061861
Rear-projection screens are utilized in various types of equipment, such as projection-based radar displays, televisions, flight simulators, avionic displays, traffic control lights, microfilm readers, video games, projection-based video monitors, and rear-projection film media displays for generating a user-viewable display. In such applications, an image source located behind the screen projects light forward along a projection axis toward the screen to form an image at the plane of the screen which is distributed to viewers on the front side of the screen.
Where multiple viewers are present, such viewers are typically positioned horizontally, and distribution of light through a large horizontal angle is desirable. This is particularly true in rear-projection televisions, where multiple viewers are generally present and seated throughout a relatively wide horizontal angle relative to the screen. Since the viewers are not generally spread in the vertical direction, the screen therefore restricts the angular distribution of the light in the vertical direction.
An ideal rear projection screen is also one that transmits as much of the projected light as possible, with typical transmissions exceeding eighty percent or even ninety percent. At the same time the screen should also absorb as much ambient light incident upon it from the front side, in order to increase the black level, and the contrast, of the screen. Absorbing most of the front light, while at the same time maximizing the transmittance of the light projected onto the screen from the rear side, is challenging to the screen designer, but is necessary in order for the screen to be labeled a high-performance screen.
A rear-projection screen is provided in accordance with one embodiment that includes a substrate including a first side and a second side, lenticular lenses or an array of microlenses disposed on the first side of the substrate, and an opaque layer disposed on the second side of the substrate. In a particular embodiment, the opaque layer includes a plurality of apertures therethrough. A surface relief diffuser can be provided in the substrate at the plurality of apertures to diffuse the projected image.
A bulk diffuser can be provided at the plurality of apertures to diffuse the projected image. A cover can be attached to the opaque layer, for example, with an adhesive. In a particular embodiment, the surface relief diffuser is formed by a laser ablation process, i.e., irradiation through and focused by the lenticulars ablates the opaque layer to form the plurality of apertures or grooves. At the same time, as part of the ablation process, the surface relief diffuser is formed in the surface of the substrate at the apertures. In one embodiment, the lenticular or microlenses including the microlens array are elliptical or circular in cross-section.
A method for forming a rear-projection screen is provided that includes forming lenticulars, or alternately a microlens array, on a first side of a substrate, forming an opaque layer on a second side of the substrate, and irradiating the lenticulars to form a plurality of apertures in the opaque layer and a surface relief diffuser in the substrate at the apertures. The method can also include providing a bulk diffuser in the plurality of apertures and attaching a cover to the opaque layer.
A rear-projection screen is provided that includes a substrate including a first side and a second side, lenticulars or a microlens array disposed on the first side of the substrate, and an opaque layer disposed on the second side of the substrate. An overlayer disposed on the opaque layer can include a plurality of apertures therethrough, and a bulk diffuser can be provided at the plurality of apertures.
A surface relief diffuser can be provided in the substrate at the plurality of apertures. A cover can be attached to the overlayer disposed on the opaque layer. The surface relief diffuser and the plurality of apertures are formed by a laser ablation process in one embodiment. The lenticulars or the lenslets including the microlens array can be elliptical or circular in cross-section.
The overlayer disposed on the opaque layer can include a light-absorbing material in and/or on the overlayer. In a particular embodiment, the light-absorbing material includes a color light-absorbing tint that can absorb blue light.
A method for forming a rear-projection screen is further provided that includes forming lenticulars or an array of microlenses on a first side of a substrate, forming an opaque layer on a second side of the substrate, forming an overlayer on the opaque layer, and irradiating the lenticulars to form a plurality of apertures in the opaque layer and the overlayer on the opaque layer. The step of irradiating the lenticulars can form a surface relief diffuser in the substrate at the plurality of apertures.
The method can further include providing a bulk diffuser in the plurality of apertures and attaching a cover to the overlayer. A light-absorbing material can be provided on and/or in the overlayer on the opaque layer. In a particular embodiment, the light-absorbing material includes a blue light-absorbing tint.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of various embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.
A description of various embodiments of the invention follows.
An opaque layer 16 is provided on the opposite or second side of the substrate 14. The opaque layer should be made as thin as possible, but not so thin that it becomes transmissive to light. In a particular embodiment, the opaque layer 16 has a thickness between about 10 to 30 micrometers. In a particular embodiment, opaque layer 16 is ablatable, that is, irradiation, such as a laser, can be directed through the lenses 12 to form apertures 18 in the opaque layer, as set forth in International Publications WO 00/67071, published on Nov. 9, 2000, WO 03/069407, published on Aug. 21, 2003, and WO 03/069408, published on Aug. 21, 2003, the entire teachings of each application being incorporated herein by reference. It has been discovered that by adjusting the intensity of the laser, a texture or surface relief diffuser (SRD) 20 is provided in the substrate 14 at the bottom of aperture 18. In a particular embodiment, the power of the laser is continuous and is in the range of about 20 to 2,000 watts. The SRD 20, which includes a shallow depth, diffuses light passing through the apertures 18. In one embodiment, the SRD 20 produces a light-diffusing optical element whose half-angles are about ±10 degrees, which is desirable for rear-projection television screens.
In further embodiments, the apertures 18 can be filled with a bulk diffuser 22 to further diffuse the light passing through the apertures. The bulk diffuser improves the grain and speckle characteristics while not sacrificing other screen performance parameters.
An adhesive layer 24 can be provided on the opaque layer 24 for attaching an outer layer or cover 26 thereto. The adhesive layer 24 can be substantially optically transparent. In a particular embodiment, the outer cover 26 has a thickness of about from about 2 mm to 3 mm and can include an acrylic material.
The screen 10 of
As illustrated in
A deep aperture can also be provided by using a thicker opaque layer 16. However, the deeper groove in the opaque layer 16 causes more light “louvering”, which acts to block light that passes through the aperture at angles substantially departed from perpendicular to the rear-projection screen 10. Since overlayer 30 is transparent it reduces the amount of louvering, but still allows for a deeper aperture 32 to be filled with bulk diffuser 22 to reduce grain and speckle. A cover 26 can be attached to the overlayer 30 by an adhesive 24, as illustrated in
An array of lenticular lenses, when irradiated by ablating laser radiation, produces an array of linear apertures as shown in
The screen 10 of
Second, the screen 10 of
A third advantage of the rear-projection screen 10 of the present application relates to color shift. As present rear-projection screens are viewed at increasingly off-axis, i.e., non-normal, viewing angles, the projected image becomes bluer in appearance. In a particular embodiment, overlayer 30 can include a light-absorbing material therein and/or a light-absorbing material thereon. The light-absorbing material can include a blue or color light-absorbing tint to eliminate or substantially reduce color shift. The light-absorbing material can be equal and opposite to the coloring caused by the bulk diffuser 22. As illustrated in
While this invention has been particularly shown and described with references to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
