The present invention relates to a rear projection screen, more particularly to large sized rear projection screen.
The existing rear projection screen of prior art includes a Fresnel lens for collecting the image incident light, and a cylindrical lens array for receiving the image light collected by the said Fresnel lens, an ambient light absorbing portion and a image light effluence portion formed at the image-light exit side. As to the small sized screen for rear projection TV set, the cylindrical lens array in the screen can be manufactured by the integrated mold due to the size of the mold is small. But for the larger sized rear projection screen, such as more than 150 inches, if the cylindrical lens array in the screen still is made by the integrated mold, then the cost for the mold will be very high, that is, it is infeasible in view of economic point. Therefore, a large sized rear projection screen is normally formed by assembling a plurality of small rear projection screen. For example, a patent No. JP 1998-260478 disclosed an assembled large sized rear projection screen, which includes a plurality of unit screen in the horizontal and longitudinal direction, the sidepiece of each unit screen are fixed with the shade at the back side by screws. The screws are positioned at the inner side of the sidepiece of each unit screen instead of at the seam between two adjacent unit screens, result that the adjacent unit screens can be joint tightly almost without black strip shade lights. But there are still lots of image shading black spots at the position where the screws are fixed at the sidepiece of each unit screen, and the size of the image shading black spots are much larger than the ones of the pixels which form images. Accordingly the integrity and continuity of images are damaged.
The object of the present invention is to provide a large sized rear projection screen, wherein there is not any shade for the images projected from rear, accordingly to provide with complete images without any defects.
The object of the present invention can be realized by the following large sized rear projection screen, which includes:
a Fresnel lens for collecting the image incident light, a cylindrical lens array for receiving the image light collected by the said Fresnel lens, and an ambient light absorbing portion and a image light effluence portion formed at the image-light exit side;
wherein the said cylindrical lens array comprises of a plurality of cylindrical lens elements, these cylindrical lens elements are separated from each other, that is independent, and in parallel, and arranged closely between adjacent cylindrical lens element, so that there are no luminous flux loss therebetween. A strengthening area, which is provided with a rigid reinforced member connecting with cylindrical lens elements on two sides thereof, is formed on the area being from their contact portion to the image-light exist-side surface between adjacent cylindrical lens elements. An ambient light absorbing portion is formed on the image-light exit side in the strengthening area.
With respect to the large sized rear projection screen with the above mentioned structure, as a strengthening area is formed in the cylindrical lens array which is made as outer side of the screen and reinforced members are formed within the strengthening area, so the impact strength, bending strength and rigidity of the full screen are improved, and the cylindrical lens will not deformed. In addition, since the said strengthening area is located in the area where no luminous flux loss is generated, and the strengthening area dose not shade any light projected from rear side, the images shown on the full screen possess the integrity and continuity without shadow or black spots caused by fixing screws of those prior art And the large sized rear projection screen of the present invention furthermore dose not have the wide striped shadows which possessed by the market available large sized screen assembled by multi-screen unit with sidepieces. As all strengthening area are located in the area where no luminous flux loss is generated and all strengthening area are provided with ambient light absorbing portion, so the ambient light absorbing portion of the complete screen according to this invention, i.e. the portion of the black grounding, is much higher than the ones of the conventional rear projection screen. Furthermore, due to the cylindrical lens array of the screen of present invention consist of a plurality of elements, i.e. breaking up the whole into parts, the process of manufacture is simple, the expensive huge mold for the conventional integrated rear projection screen is not required according to this invention.
In the said rear projection screen, each cylindrical lens elements can be formed by many integrated basic cylindrical lenses whose axial plane keep in parallel.
As to the large sized rear projection screen, since each cylindrical lens elements possesses many integrated basic cylindrical lenses, the number of the element decreases, the efficiency of assembling increases, the production cost of the screen can be reduced while the optical performance is not lost
In the said rear projection screen, each cylindrical lens elements may comprises single basic cylindrical lens.
As to the large sized rear projection screen of this invention, each cylindrical lens element is formed by many integrated basic cylindrical lenses, so that strengthening area can be formed between the single basic cylindrical lenses with rigid reinforced members provided therein, accordingly the rigidity of the whole screen is improved. In addition, the ambient light absorbing portions which are provided between basic cylindrical lenses are made of the same material, so the effect of light absorbing in the whole screen may remain consistent
In the rear projection screen of this invention, those cylindrical lens elements can be assembled with two kinds of cylindrical lens elements. The first kind of cylindrical lens elements are formed by many integrated basic cylindrical lenses whose axial plane keep in parallel, the second kind of cylindrical lens elements are formed by single basic cylindrical lenses.
In the rear projection screen of this invention, the first and second kind of cylindrical lens elements can be arranged in the manner that one or more first kind of cylindrical lens element(s) is/ are provided between two the second kind of cylindrical lens elements.
In the rear projection screen of this invention, the first and second kind of cylindrical lens elements can be arranged in the manner that one or more the second kind of cylindrical lens element(s) is/ are provided between two the first kind of cylindrical lens elements.
In the rear projection screen of this invention, the rigid reinforced members can be the shape of xe2x80x9cYxe2x80x9d or xe2x80x9cTxe2x80x9d, wherein the two front wings are positioned at the image-light exit side. The screen is provided with a outer frame which is connected with the two ends of the reinforced members.
In the rear projection screen of this invention, the cross section of the reinforced members can be of polygonal wherein one of angles protrudes toward the direction of image-light exiting.
As to the large sized rear projection screen of this invention, since the front portion of the reinforced members projects toward out side, the contact between the cylindrical lenses and environmental objects can be avoided to prevent the cylindrical lens from abrading and damaging.
In the rear projection screen of this invention, the reinforced members can be made from rigid materials. At the out side of the reinforced members, i.e. the image-light exit side, a black oxide layer or black overcoating layer is provided.
In the rear projection screen of this invention, the rigid material can be metal, carbon fiber or non-metal material with high rigidity, wherein the metal can be light metal, for example aluminum alloy.
If the reinforced members adopt aluminum alloy, the weight of the screen can be reduced with sufficient mechanical strength ensured.
The reinforced members and the corresponding cylindrical lenses of both sides can be jointed by engaging a tenon with a mortice.
As to the large sized rear projection screen of this invention, the contacting area between the reinforced members and the adjacent cylindrical lens elements can be enlarged to ensure the sufficient joint strength therebetween and to increase the surface area of the ambient light absorbing portion.
The reinforced members and the corresponding cylindrical lenses of both sides can be jointed by bond.
The ambient light absorbing portion in the strengthening area can be formed by black reinforced members themselves which absorb the ambient light.
As to the large sized rear projection screen of this invention, since the reinforced members themselves can be light absorbed black parts, then it may function the rigidity improving and ambient light absorbing to simplify the process of screen manufacturing. Furthermore, unlike the ambient light absorbing portion of those conventional screen with stuck black band or coated black layer, light absorbing effect of the ambient light absorbing portion of this invention will not be easily reduced by abrading or damaging.
The ambient light absorbing portion of the strengthening area can be made from light absorbing packing which stuff the area.
The Fresnel lens of this invention is made of two overlapped lenses with straight Fresnel stripes, and the direction of the straight Fresnel stripes of the two lenses keep at right angles each other.
The large sized rear projection screen of this invention facilitates the manufacturing of the Fresnel lens to reduce the relevant production cost.
The ambient light absorbing portions are also provided at the sides adjacent to cylindrical lens elements of both sides in the strengthening area.
As to the large sized rear projection screen of this invention, the ambient light absorbing portions are also provided at the other sides except the front side, i.e. the image-light exit side, so that the diffusion lights which are projected into the inner of the cylindrical lens through image light diffused transmission part of the cylindrical lens can be massively absorbed, accordingly the portion of the black grounding of the complete screen is increased substantially.
The large sized rear projection screen of this invention can be used on the large screen in TV studio, air port and train stations, the large sized active image advertising in main streets, the large sized image monitoring system of industrial control (such as power plant, steelworks and chemical plant), monitoring system of military commanding, analog campaign system, auditorium, meeting room, the large sized screen in multi-functional hall, teaching room, entertainment place, and cinema etc.
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