Rear screen projection with curved screen

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Publication number
GB2496534A
Authority
GB
Grant status
Application
Patent type
Prior art keywords
screen
reflector
projector
rear screen
screen projection
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB201300577A
Other versions
GB201300577D0 (en )
GB2496534B (en )
Inventor
Peter Mcatominey Stromberg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
STROMBERG INDUSTRIES APS
STROMBERG IND APS
Original Assignee
Stromberg Ind Aps
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Filing date
Publication date

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B7Details common to cameras
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/14Details
    • G03B21/28Reflectors in projection beam
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B7Details common to cameras
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/54Accessories
    • G03B21/56Projection screens
    • G03B21/60Projection screens characterised by the nature of the surface
    • G03B21/606Projection screens characterised by the nature of the surface for relief projection
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B7Details common to cameras
    • G03B21/00Projectors or projection-type viewers; Accessories therefor
    • G03B21/54Accessories
    • G03B21/56Projection screens
    • G03B21/60Projection screens characterised by the nature of the surface
    • G03B21/62Translucent screens
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N9/00Details of colour television systems
    • H04N9/12Picture reproducers
    • H04N9/31Projection devices for colour picture display e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3141Constructional details thereof

Abstract

A rear screen projection apparatus comprises a screen (3), the screen being translucent and extending in a first direction (x) and a second direction (y) perpendicular to the first direction (x) and curved by a constant radius of curvature in a third direction (z) perpendicular to the first and second directions (x, y); a reflector (2), the reflector extending in the first direction (x) and the second direction (y) and being curved by a constant radius of curvature in the third direction (z); and a position (1) for an optical focal point of a projector_ The curvatures of the screen (3) and the reflector (2) may be concentric. The rear screen projection apparatus may have a projector (6) with its optical focal point at the position (1). The reflector (2) may be made of plastic. The position (1) may be in the radial direction of the concentric reflector (2) and screen (3), half way between the reflector (2) and the screen (3).

Description

REAR SCREEN PROJECTION APPARATUS AND METHOD

Technical field

The present disclosure relates to a rear screen projection apparatus and method.

More particularly, the present disclosure relates to an arrangement, system and method for projecting images on a curved translucent screen.

Background

Some screen projection systems use different techniques to produce an immersive video screen that surrounds the viewer. Image signal warping is sometimes used for front projection on curved surfaces. This technique uses software to manipulate the image being projected in order for it to appear to be a regular shape when hitting the curved surface of a curved screen, Image signal warping may sometimes be used for rear projection. In a similar way to front projection it is possible to project onto the rear of a curved screen and rely on warping software to eradicate the distortion in the image caused when the light from the projector hits the curved surface of the screen. Some prior art use segmented flat panel screens arranged at specific angles to form a primitive arc. These can be rear projected with conventional consumer projectors with no warping required. However, the result is far from being geometrically correct from the observers point of view. Other prior art achieves rear projection with Fresnel lenses or other custom made lenses.

Fresnel lenses were used to reduce the distance required for projection in rear projected TV's.

The present invention is directed to overcoming one or more of the problems as set forth above. The prior known rear projection systems are either expensive, utilizing custom optics, or compromise geometric accuracy. Systems may include expensive lens systems. In addition manipulation, digitally or mechanically, of the projected beam may be necessary to provide an image. The problems with systems and methods projecting images on curved screens relate to projecting the image correctly onto the curved screen. This normally results in cumbersome arrangements for resolving issues regarding image quality/resolution, optical focus, and signal strength as well as mirror and/or lens fabrication costs. Additionally, it is desirable to avoid the cumbersome arrangements from a technical and/or economical point of view.

Summary

It is an object of the present invention to provide a rear screen projection apparatus and method. This object can be achieved by the features as defined in the independent claims. Further enhancements are characterised in the dependent claims.

In one embodiment, a rear screen projection apparatus, comprises a screen (3), the screen being translucent and extending in a first direction (x] and a second direction (y) perpendicular to the first direction (x] and being curved by a constant radius of curvature in a third direction (z) perpendicular to the first and second directions [x, a reflector (2), the reflector extending in the first direction (x) and the second direction (y) perpendicular to the first direction (x) and being curved by a constant radius of curvature in the third direction (z) perpendicular to the first and second directions (x, y); and a position (1) for an optical focal point of a projector The curvatures of the screen (3) and the reflector (2) may be concentric.

In one embodiment, the position (1] is, viewed in the radial direction of the concentric reflector (2] and screen (3], half way between the reflector (2] and the screen (3).

In one embodiment, the reflector is made out of a plastic material, rendering the apparatus inexpensive. In one embodiment, the reflector is made out of metal, preferably polished stainless steel, rendering the apparatus inexpensive.

In one embodiment, the rear screen projection apparatus further comprises a projector (6) having its optical focal point at the position (1).

According to an embodiment, the projector (6] is a short throw projector (6) with a minimum throw of 1,5 meters or shorter and a throw ratio oft or less, preferably an ultra short throw projector (6] with a minimum throw of 1 meter or shorter and a throw ratio of 0,5 or less. In one embodiment, the throw of the projector (6) is between 0,4 meter to 1,5 meter, preferably 0,5 meter to 0.7 meter.

In one embodiment, the rear screen projection apparatus further comprises a projector (6), for flat screens, having its optical focal point at the position (1).

In one embodiment, the reflector (2) is positioned in the middle in the first direction (x) with respect to the screen (3) and in any suitable position in the second direction (y).

In one embodiment) the position (1) for an optical focal point of a projector is above or below a beam of the projector.

In one embodiment, the screen (3) is a translucent touch screen.

In one embodiment, the position (1) is for an arrangement of mirrors for a projector beam.

One embodiment is a method for rear screen projecting an image on a screen. The screen being translucent and extending in a first direction (x) and a second direction (y) perpendicular to the first direction (x) and being curved by a constant radius of curvature in a third direction (z) perpendicular to the first and second directions (x, y). A reflector (2) is used, the reflector extending in the first direction (x) and the second direction (y) perpendicular to the first direction (x) and being curved by a constant radius of curvature in the third direction (z) perpendicular to the first and second directions (x, y). A position (1) is provided for an optical focal point of a projector. The method may comprise the steps of: projecting a projector beam (B) with an optical focal point at the position (1) onto the reflector (2) and reflecting the projector beam (B) onto the screen (3).

In one embodiment, the method may comprise placing the position (1) of the optical focal point of the projector beam (B), viewed in the radial direction of the concentric reflector (2) and screen (3), halfway between the reflector (2) and the screen (3).

In one embodiment, a short throw projector [6) may be used with a minimum throw of 1,5 meters or shorter and a throw ratio of 1 or less, preferably an ultra short throw projector (6) with a minimum throw of 1 meter or shorter and a throw ratio of 0,5 or less.

In one embodiment, the visible distortions in a projected image on the curved screen (3) may be minimized when using a projector for projecting the image on a flat screen. In one embodiment, the curvatures of the screen (3) and the reflector (2) maybe concentric.

In one embodiment:, the screen (3) maybe replaced by larger screens (16,17) being geometrically similar in form and positioned within the image beam (B] at such a distance as to achieve a comparable larger scaled image.

In one embodiment [17) an addition reflector (18) may be added in order to "fold" the beam (B]. The secondary reflector (18) being of a malleable material such as plastic, may be adjusted in order to provide keystone manipulation, as well as alterations in aspect ratio, and other calibration techniques.

Such embodiments, or a combination thereof, may resolve the problems with systems and methods projecting images on curved screens relate to projecting the image correctly onto the curved screen. Such embodiments may provide a rear screen projection apparatus that is easily fabricated, accurate and economic. Such embodiment may avoid cumbersome arrangements for resolving issues regarding image quality, optical focus, and mirror and/or lens fabrication costs. Additionally, such embodiment may avoid the cumbersome arrangements from a technical and/or economical point of view. The use of short throw projectors for flat screens and the use of an inexpensive material as a reflector render the apparatus easy to fabricate, accurate, and economic.

Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following description and claims. Various embodiments of the present application obtain only a subset of the advantages set forth. No one advantage is critical to the embodiments. Any claimed embodiment may be technically combined with any preceding claimed embodiment(s).

Drawings The accompanying drawings illustrate presently preferred exemplary embodiments of the disclosure and serve to give, by way of example, an understanding of the claimed invention.

FIG. 1 shows a perspective view of a rear screen projection apparatus according to an exemplary embodiment; FIG. 2 is a diagrammatic illustration of a rear screen projection apparatus according to an exemplary embodiment;

S

FIG. 3 shows a rear screen projection apparatus according to an exemplary embodiment; FIG. 4 illustrates usable projection area of a conventional projection compared with that of an exemplary embodiment of the present disclosure; FIG. S shows a rear screen projection apparatus according to an exemplary embodiment; and FIG. 6 shows a rear screen projection apparatus according to an exemplary embodiment.

FIG. 7 shows a rear screen projection apparatus according to an exemplary embodiment.

FIG. B shows a rear screen projection apparatus according to an exemplary embodiment.

Description

According to an embodiment a rear screen projection apparatus and method is shown in FIGs. 1-3. A perspective view of a set up comprises a projector (6), or a position (1) for a projector (6), a reflector (2), and a screen (3). The optical focal point of the projector may be provided at a position (1) between the reflector (2) and the screen (3).

The screen (3] may be a translucent screen. The screen (3] may be curved.

Preferably the concave side of the curved screen (3) faces the viewer and the convex side of the curved screen receives the projection. The screen (3] extends in a first direction (x) and a second direction (y] perpendicular to the first direction (x]. In one embodiment the first direction (x] may be in the horizontal plane and the second direction (y) may be in the vertical plane. The screen is curved by a constant radius of curvature in a third direction (z) perpendicular to the first and second directions (x, y]. In one embodiment the screen (3)is in the shape of a cylinder or a part of a cylinder. In one embodiment, the screen (3) may comprise several screens (3] arranged to one large screen (3), as disclosed below. In one embodiment the screen (3] may extend over an angel (a] as illustrated in FIG. 2. The angel (a] may preferably be 60 degrees, but could be between 15 and 90 degrees. The screen (3] may be made of a translucent plastic or glass material. Preferably the reflector (2] may be made of plastic or glass.

The reflector (2) extends in the first direction (x] and the second direction (y) perpendicular to the first direction [x]. The reflector (2) is curved by a constant radius of curvature in the third direction [z) perpendicular to the first and second directions (x, y). In some embodiments the reflector (2) is not hyperbolic or parabolic. In one embodiment, the reflector [2] is in the shape of a cylinder or a part of a cylinder. In one embodiment the reflector [2] may be shaped as a regular arc, concentric to that of the screen (3] on which the image will be displayed. The reflector [2] may be a mirror. Preferably the reflector (2] may be made of glass or a reflective material. When the reflector (2] is made out of plastic, the rear screen apparatus becomes a very economic apparatus, but also technically accurate. In one embodiment, the reflector (2) is made out of metal, preferably polished stainless steel, rendering the apparatus inexpensive.

In one embodiment the screen (3) and the reflector [2) are concentric. The curvatures of the screen (3] and the reflector (2] are concentric. The screen [3] and the reflector (2) share the same centre for their respective curvature. The concave side of the reflector [2) faces the convex side of the screen (3).

In one embodiment the reflector (2) maybe centrally placed in the first direction [x] in relation to the screen (3]. The reflector (2) may be along any position along the second direction (y) for projecting the image.

A position (1] for an optical focal point of a projector is provided. This position (1] allows to position the optical focal point of a projection beam in the right position for projecting the image. The position [1) may be a support or an arrangement for a projector such that the focal point of the projector can be positioned in the correct place of the rear screen projection apparatus or method. In one embodiment the position is the focal point of the projector used. In one embodiment, when a rear screen projection apparatus is provided without a projector, the position may be a support such that when the apparatus is set up a projector may be positioned in the right place of the apparatus. In this way the rear screen projection apparatus is not limited to a specific projector and the projector can be positioned within the apparatus such that the focal point of the projector used is in the position (1).

The position (1] may be, viewed in the radial direction of the concentric reflector (2] and screen [3], half way between the reflector [2] and the screen (3). This is best illustrated in FIG. 2, where the reflector (2) and the screen (3) are concentric; share the same the same centre for their respective curvature. The position (1) is along a curved dotted line [5). The curved dotted line [5) is halfway between the radius of the screen [3] and the reflector [2]. Half the way has been indicated by a length (I] in FIG. 2. The length (I] equals dividing by two the subtraction of the radius of the curved reflector (2) minus the radius of the curved screen (3). In one embodiment, the position [1] on the curved dotted line [5] is exactly hall way between the reflector (2) and the screen (3). This allows for a very sharp and focused image with minimal visible distortion.

It is the conditions described above with concentric curvatures of the screen (3) and the reflector (2] that allows for minimal visible distortion. There may be some distortion due to the reflector [2) being curved at a constant radius of curvature, but this is minimal and can in most practical display situations be neglected.

The embodiments shown in FIGs. 1-3 show that when the image projected from the projector (1] hits the curved reflector (2), the image is warped. For example, the image becomes progressively more and more distorted towards the top (4] of the image. When the warped image hits the surface of the curved screen (3), this effect is reversed in such a way that lines that are straight and parallel in the source image, in both the first direction (x] and the second direction (y), are approximately parallel in the resulting image on the screen. This allows for a minimal visible distortion.

According to an embodiment, the focal point of the projector [6) is on the curved dotted line [5], halfway between the arc of the screen [3) and reflector (2).

According to one embodiment, the projected image becomes narrower than the source image, thus narrower in the lower part of the final image than in the upper part of the final image. This depends on the distances and on the angle (a) of the projector beam. This scaling can be rectified by scaling the source image in the opposite direction. Such scaling may be done within the projector or by the signal source.

Turning to FIG. 3, an embodiment is illustrated with a projector (6] projecting a beam from the position [1) haff way between the reflector (2) and screen (3). The illustrated curvature of the reflector [2) and the screen (3) in FIG. 3 makes the reflector (2) and the screen (3) appear thicker in FIG. 3. In one embodiment, the projector (6) may be positioned below the projected beam of the projector (6). In this way the position (1) of the projector [6) does not interfere with the image. In one embodiment the projector (6) may be positioned above the projected beam of the projector (6). In one embodiment, for a short throw projector [1), the image is projected upwards on the curved reflector (2), and backwards towards the curved screen (3), avoiding the actual projector (1) and its housing. In this way a shadow is not casted on the screen [3).

In one preferred embodiment the position [1) of the projector [6) and the reflector (2) maybe positioned at any position to project an image, as long as the position (1) is half the way between the reflector (2) and the screen [3).

FIG. 4 shows a conventional front projection onto a curved screen [a) and an optically corrected rear projection, according to an embodiment of this disclosure, onto a curved screen (b). The difference in usable projection area, the hatched area, between the two screens (a) and [b) may easily be taken from the FIG. 4.

Embodiments of the present disclosure clearly contribute to the usable projection area and the viewing experience.

The described embodiments having the described arrangement of the concentric reflector (2) and screen (3) can be combined and applied to many different configurations and/or embodiments of this disclosure. For example, a plurality of rear screen projection apparatuses may be combined. In such combinations a preferred embodiment may be that the position (1) for the projector may be half way between the reflector [2) and the screen [3).

According to an embodiment illustrated by FIG. 5, a plurallty of rear screen projection apparatuses may be combined. In this embodiment two rear screen projection apparatuses are positioned next to each other in the first direction (x).

For example, a first projector (6) may project a projection beam onto a first reflector (7) and a second projector (8) may project a projection beam onto a second reflector (9). The first and second reflectors (7, 9) then reflects respective beam onto a screen (10]. The screen (10) maybe a continuous curved screen. The screen (10] may be a contiguous curved screen, comprising a plurality of screens (3). The screen (10) may for example be twice the angle (a). In one embodiment muhiple projectors and reflectors can be used to create an image on a continuous screen. By adding extra projectors and reflectors a projected area may be created that covers up to 360 degrees. In one embodiment this may create a curved screen (10) extending in the horizontal direction.

According to an embodiment illustrated by FIG. 6, a plurality of rear screen projection apparatuses may be combined. In this embodiment two rear screen projection apparatuses are positioned next to each other in the second direction (y].

For example, a first projector (11) may project a projection beam onto a first reflector (12) and a second projector (13) may project a projection beam onto a second reflector (14). The first and second reflectors (12, 14) then reflects respective beam onto a screen (15). The screen (15) may be a continuous curved screen. The screen (15) may be a contiguous curved screen, comprising a plurality of screens (3). In one embodiment multiple projectors and reflectors can be used to create an image on a continuous screen. In one embodiment this may create a curved screen (15) extending in the vertical direction. While the upper constellation of projector (11) and reflector (12) has been illustrated as inverted with respect to the lower constellation of projector (13) and reflector (14), the two constellations need not to be inverted. For example, the projector (11) may be below the dotted middle line of the screen (15).

In one embodiment, the arrangements disclosed in the embodiments illustrated by FIGs. 5 and 6 may be combined to create a curved screen extending in bot the first and second directions (x, y). In this way a screen may partly or completely be around a viewer. In this way continuous curved screens between 60 and 360 degrees can be created using multiples of the disclosed rear screen projection apparatus. In one embodiment, the height of a rear screen projection apparatus can be doubled through a multiple of constellations.

FIG 7 and FIG S show some examples of extrapolations of the configuration shown in FIG 1-3. Alternative sizes of translucent screen (16, 17) may be employed because the light within the beam (B] radiates in a straight line. These alternative screens (16, 17] maybe geometrically similar to the screen (3], that is to say scaled replicas positioned at an appropriate distance as to mimic the behaviour of the screen (3]. By this apparatus or method, projections on screens of many diflerent sizes may be created utilising an identical reflector [2].

As shown in FIG 8, in order to further reduce the physical distance required between the primary reflector (6) and the translucent screen (3), a secondary flat reflector (18) may be employed. The secondary reflector (18] may be of a similar material to the primary reflector (6], that is to say reflective plastic or silvered glass.

The second reflector may be manipulated as to provide keystone adjustment, altered aspect ratio, and other refinements of the original warped image.

In one embodiment, the projector used may be a short throw projector. A short throw projector may keep the dimension of the rear screen projection apparatus in the third direction (z) to a minimum. In one embodiment, an ultra short throw projector may be used. In one embodiment, the projector (6] may be a short throw projector (6] with a minimum throw of 1,5 meters and/or a throw ration of 1 or less. The throw could be shorter than 1,5 meters. In one embodiment, the projector (6) may be an ultra short throw projector (6) with a minimum throw of 1 meter and/or a throw ratio of 0.5 or less. The throw could be less than 1. In these embodiments the apparatus becomes very compact and inexpensive, because a short throw projector as normally used for flat screens can be used.

In one embodiment, the distance travelled by the light emitted from the projector is approximately equal to the distance travelled when illuminating a fiat surface, for which projector lenses may be specifically developed. This alleviates the focusing issues normally experienced when a projector lens designed for use on a flat screen is used in a curved screen installation. This allows the present embodiments to use a standard, mass produced and inexpensive projector, which in turn keeps the costs and technical arrangements for a rear screen projection embodiment according to the invention down. By the same account, the output strength of the image from corner to corner is comparable with a flat image produced using the same equipment In one embodiment, the reflector (2] used requires little or no special optical precision. Acceptable results can be obtained using readily available reflective plastic materials, for example as used in the sign industry. In one embodiment, other materials may be used, including more conventional glass with silver coating) and with the same manufacturing advantages of form and tolerance.

In one embodiment) the reflector may be a mirror shaped as a curved rectangle.

Such a reflector may be manufactured by applying a highly reflective material to, for example, a wooden, metal, or plastic substrate produced with conventional tooling.

In one embodiment) the comparatively large size of the reflector (2] results in larger tolerances in the manufacturing process when compared to smaller optical mirrors that require minute tolerances in order to achieve accurate results. According to embodiments, the practical effect is that the reflector, and thus the whole rear screen projection apparatus) can be produced extremely economically, and by non-specialist individuals, and with standard machinery. Embodiments avoid the use of special lenses) such as) Fresnel lenses.

In embodiments) the use of a reflector (2] curved by a constant radius of curvature in the third direction (z) perpendicular to the first and second directions (x, y) results in minimising visible distortion. This achieves an efficient, inexpensive) focused, and relatively distortion free rear screen projection apparatus. The embodiments of the present invention provide a result that is more than accurate enough to satisfy human perception, even when viewing something as regular as a grid. To be able to see distortions by the human eye would be very difficult) if not impossible. Embodiments of the present disclosure therefore strike a desirable balance of technical effort and cost to an image quality of the rear screen projection apparatus.

In embodiments described, a projector designed for projecting images on a flat, not a curved screen, may be used. This has the advantage of using inexpensive) readily available, mass produced projectors. It has also the advantage of being able to use a wide range of different projectors and select the most suitable for the specific environmental conditions for the place of the rear screen projection apparatus.

According to an embodiment, a method is disclosed for projecting an image onto a curved screen. The screen may be translucent and extending in a first direction (x] and a second direction (y] perpendicular to the first direction (x] and being curved by a constant radius of curvature in a third direction (z] perpendicular to the first and second directions (x, y). The method comprises using a reflector (2), the reflector extending in the first direction (x) and the second direction (y) perpendicular to the first direction (x) and being curved by a constant radius of curvature in the third direction (z) perpendicular to the first and second directions (x, y]; providing a position (1] for an optical focal point of a projector; and wherein the curvatures of the screen (3) and the reflector (2] are concentric. The method may comprise the steps of projecting a projector beam (B) with an optical focal point at the position (1] onto the reflector (2), and reflecting the projector beam (B] onto the screen (3).

In one embodiment, the method further comprises placing the position (1) of the optical focal point of the projector beam (B], viewed in the radial direction of the concentric reflector (2) and screen (3), half way between the reflector (2) and the screen (3).

In one embodiment a short throw projector (6) with a throw of 1,5 meters or shorter may be used. In one embodiment an ultra short throw projector (6) with a throw of 1 meter or shorter maybe used.

The invention is used to create rear projected curved displays of virtually any radius or height using an array of projectors and reflectors and a translucent screen.

Embodiments of the present disclosure offer many advantages. For example, no shadows are cast by individuals or objects positioned near the screen, i.e. within the projection frustum of the projector This means the individuals can go right up to the screen without interfering with the projected image. This also makes the configuration highly suitable for touch screen applications requiring users to interact directly on the surface of the projected image. For example, the hardware of the projection apparatus is not readily accessible to the audience providing a more secure installation for public areas.

The system and method discussed above projects images on a curved screen with minimal distortion. The invention) therefore) is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein.

While the invention has been described and is defined by reference to particular preferred embodiments of the invention, such references do not imply a limitation on the invention) and no such limitation is to be inferred. The invention is capable of considerable modification, akeration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts. Any one of the disclosed embodiments may be technically combined with any other embodiment disdosed.

The described preferred embodiments of the invention are exemplary on'y, and are not exhaustive of the scope of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.

Claims (1)

  1. <claim-text>CLAIMS1. A rear screen projection apparatus) comprising a screen (3), the screen being translucent and extending in a first direction (x) and a second direction (y) perpendicular to the first direction (x) and curved by a constant radius of curvature in a third direction [z) perpendicular to the first and second directions (x, y); a reflector (2), the reflector extending in the first direction (x) and the second direction (y) and being curved by a constant radius of curvature in the third direction (z); and a position (1) for an optical focal point ofa projector.</claim-text> <claim-text>2. The rear screen projection apparatus according to claim 1, further comprising a projector [6) having its optical focal point at the position (1).</claim-text> <claim-text>3. The rear screen projection apparatus according to claim 1 or 2, wherein the curvatures of the screen (3) and the reflector (2) are concentric.</claim-text> <claim-text>4. The rear screen projection apparatus according to any one of the preceding claims, wherein the reflector (2) is made of plastic or metal.</claim-text> <claim-text>5. The rear screen projection apparatus according to any one of the preceding claims, wherein the position (1) is, viewed in the radial direction of the concentric reflector (2) and screen (3), halfway between the reflector (2) and the screen (3).</claim-text> <claim-text>6. The rear screen projection apparatus according to any one of the preceding claims, wherein the projector (6) is a short throw projector (6) with a minimum throw of 1,5 meters and a throw ratio of 1 or less) preferably an ultra short throw projector (6) with a minimum throw oft meter and a throw ratio of 0,5 or less.</claim-text> <claim-text>7. The rear screen projection apparatus according to any one of the preceding claims, further comprising a projector (6) designed for projecting images on a flat screens, and the projector [6) having its optical focal point at the position [1].</claim-text> <claim-text>8. The rear screen projection apparatus according to any one of the preceding claims, wherein the reflector (2) is positioned in the middle in the first direction (x) with respect to the screen (3) and in any suitable position in the second direction [y).</claim-text> <claim-text>9. The rear screen projection apparatus according to any one of the preceding claims, wherein the position (1) for an optical focal point of a projector is above or below a beam of the projector.</claim-text> <claim-text>10. The rear screen projection apparatus according to any one of the preceding claims, wherein the screen (3) is a translucent touch screen.</claim-text> <claim-text>11. The rear screen projection apparatus according to any one of the preceding cdaims, wherein the position is for an arrangement of mirrors for a projector beam.</claim-text> <claim-text>12. A method for rear screen projecting an image on a screen, the screen being translucent and extending in a first direction (x] and a second direction (y] perpendicular to the first direction (x] and curved by a constant radius of curvature in a third direction (z) perpendicular to the first and second directions (x, y); using a reflector [2), the reflector extending in the first direction [x) and the second direction [y) and being curved by a constant radius of curvature in the third direction (z); and providing a position (1) for an optical focal point of a projector; the method comprising the steps of: projecting a projector beam [B) with an optical foca' point at the position (1) onto the reflector [2), and reflecting the projector beam [B) onto the screen (3).</claim-text> <claim-text>13. The method according to daim 12, further comprising placing the position (1) of the optical focal point of the projector beam (B), viewed in the radial direction of the concentric reflector (2) and screen (3), half way between the reflector (2) and the screen (3).</claim-text> <claim-text>14. The method according to claim 12 or 13, further comprising using a short throw projector (6) with a minimum throw of 1,5 meters and a throw ratio of 1 or less, preferably an tñtra short throw projector (6) with a minimum throw of 1 meter and a throw ratio of 0,5 or tess.</claim-text> <claim-text>15. The method according to any one of the claims 12 to 14, further comprising minimizing the visible distortions in a projected image on the curved screen (3) using a projector designed for projecting the image on a flat screen.</claim-text> <claim-text>16. The method according to any one of the claims 12 to 15, further comprising arranging the curvatures of the screen (3) and the reflector (2) to be concentric.</claim-text> <claim-text>17. An apparatus as described herein with reference to the description and/or drawings.</claim-text> <claim-text>18. A method as described herein with reference to the description and/or drawings.</claim-text>

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
JPS55144226A (en) * 1979-04-27 1980-11-11 Matsushita Electronics Corp Image projector
US4234891A (en) * 1979-07-30 1980-11-18 The Singer Company Optical illumination and distortion compensator
US20100002321A1 (en) * 2008-07-01 2010-01-07 Toshihide Seki Rear-projection-type display apparatus

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2837968A1 (en) * 2013-08-14 2015-02-18 Barco N.V. Projector and display system comprising same
CN104597696A (en) * 2015-02-09 2015-05-06 联想(北京)有限公司 Information processing method and electronic equipment

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GB201300577D0 (en) 2013-02-27 grant
GB2496534B (en) 2013-10-09 grant

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