Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS 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
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/54—Accessories
  • G03B21/56—Projection screens
  • G03B21/60—Projection screens characterised by the nature of the surface
  • G03B21/62—Translucent screens
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS 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
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
  • G03B21/54—Accessories
  • G03B21/56—Projection screens
  • G03B21/60—Projection screens characterised by the nature of the surface
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/17—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on variable-absorption elements not provided for in groups G02F1/015 - G02F1/169
  • G02F1/172—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on variable-absorption elements not provided for in groups G02F1/015 - G02F1/169 based on a suspension of orientable dipolar particles, e.g. suspended particles displays

Definitions

• the present invention relates to a projection screen and in particular, to a projection screen for displaying visual contents to viewers at the same side of a projector.
• a front projection screen as shown in Fig. 1, the viewer 10 is on the same side of the screen 12 as the projector 14.
• This system of projection has several limitations.
• the projection screen is usually opaque to allow maximum light to be reflected off it and back to the viewer.
• this opacity also prevents other light sources 16 behind the screen from diluting the visibility of the projected image.
• no projection is being cast on the screen, the viewer cannot see what is behind the screen without physically moving it, e.g. by rolling, collapsing, or folding the screen.
• the viewer 10 is on the opposite side of the screen 12 in relation to the projector 14.
• the projection screen is usually clear or translucent or made of a light diffusing surface. This creates one of the following experiences: firstly, the viewer can see the image projected if the screen is of the clear type but the image is diluted when there is a strong light source on either side of the screen. While no image is being projected, the viewer can see through the screen to the other side. Secondly, the viewer can see the image in most lighting conditions but is not able to see though the screen with any clarity if the screen is of the translucent type.
• the screen will not be able to display clear visible images in situations where there are strong light sources at either side of the screen.
• the screen will display a brighter image on the side opposite to the projector and the viewer, rather than displaying the image towards the viewer.
• Embodiments of the invention relate to a method and apparatus for creating a screen such that it can alternate between an opaque projection surface, a partially transparent projection surface for displaying visual contents projected thereon, and a transparent glass to allow viewers to see through the screen.
• a projection screen according to embodiments of the present invention can display an image which is front projected (projector and viewer are on the same side) even if there is a strong light source behind the screen.
• the projected image in both the opaque and the partially transparent modes are only visible from the projector's side of the screen.
• the projected image in both the opaque and the partially transparent modes is visible regardless of the lighting conditions on the non-viewer side of the screen.
• a projection screen has a front side facing a projector and an viewer, and a rear side opposite to the front site.
• the projection screen includes a display layer, a base layer and a privacy layer integrated together.
• the display layer is disposed at the front side of the screen, facing the viewer, for displaying visual contents projected from a projector.
• the base layer and the privacy layer are attached to the display layer at the rear side of the projection screen.
• An electrical field is coupled to the display layer to vary an opacity level of the display layer between a first state at which lights from the rear side are allowed to pass through the display layer to the front side, and a second state at which lights from the rear side are blocked from passing through the display layer to the front side.
• the privacy layer is to reflect more lights back to the rear side than the light passing through from the front side, hence to prevent the projected contents from being viewed from the rear side.
• the privacy layer maybe sandwiched between the base layer and the display layer.
• the base layer maybe sandwiched between the privacy layer and the display layer.
• Fig. 1 shows one type of conventional projection screen.
• Fig. 2 shows another type of conventional projection screen.
• Fig. 3 is a perspective view of a front-projection system using a projection screen according to one embodiment of the present invention.
• Figs. 4A and 4B are schematic cross sectional views of a projection screen used in a system of Fig. 3 according to alternative embodiments of the present invention..
• Figs. 5 A, 5B and 5C are schematic cross sectional views of private layers of the projection screen of Fig. 3 according to alternative embodiments of the present invention.
• Fig. 6 is a schematic view of a projection screen according to another embodiment of the present invention.
• Fig. 7 is a perspective view of the projection screen of Fig. 6 when used in a projection system.
• Fig. 8 is a schematic cross sectional view of a projection screen according to a further embodiment of the present invention.
• a projection screen 110 is used in a projection system 100 for displaying visual contents provided by projector 50 to viewer 60 at the same side of projection screen 110.
• Projection screen 110 has a front side 110F facing projector 50 and viewer 60, and a rear side 110R opposite to front side 1 lOF.
• projection screen 110A includes a display layer 120 positioned at front side 11 OF, and a privacy layer 130 and a base layer 140 disposed at rear side 110R.
• Display layer 120, privacy layer 130 and base layer 140 may be glued together using adhesives e.g. a UV (ultraviolet)-clear glue.
• Fig. 4A privacy layer 130 is sandwiched between display layer 120 and base layer 140.
• base layer 140 is sandwiched between display layer 120 and privacy layer 130, i.e. an inner surface of privacy layer 130 is attached to base layer 120.
• base layer 140 maybe made of clear tempered glass, acrylic, polycarbonate or any other solid material that allows 90% or greater visibility through it and provides strength and rigidity necessary to support the rest layers of the projection screen.
• Privacy layer 130 maybe of a film or glass or acrylic that allows one way vision, e.g. to reflect more lights back to the rear side than lights passing through from the front side, hence to prevent the projected contents from being viewed from the rear side.
• One way vision glass can be obtained by installing a high reflective window film.
• reflective window tint is generally made from two transparent polyester sheets 132, 134, which has been through a process that deposits a partial transmission-partial reflection layer 133 of very small particles of metal, usually, aluminum, silver or bronze. This creates a very thin metalized layer in between the polyester sheets 132 and 134, as shown in Fig. 5 A.
• a clear adhesive and thin polyester backing liner 131 may be attached to polyester sheet 132 for necessary support, as shown in Fig. 5B.
• a scratch-resistant coating 135 may be formed on the other polyester sheet 134, i.e. at an external surface of privacy layer 130, as shown in Fig. 5C.
• this reflective window film When this reflective window film is attached to base layer 140, it creates a one way mirror under the correct conditions, which allows lights from the rear side to pass through towards the front side, but to prevent visual contents from being viewed from the rear side.
• One form of the reflective window film is a reflective silver window film, the darkest usually referred to as "silver 20". This silver film gives a silver mirrored appearance. Other colors can be combined such as grey, gold and bronze.
• the reflectiveness of privacy layer 130 may be between 30-70%. Additionally, privacy layer 130 may provide up to 99% reduction of UV light transmission.
• display layer 120 maybe made of polymer- dispersed liquid crystals (PDLC) layer.
• PDLC polymer- dispersed liquid crystals
• a PDLC layer includes liquid crystal droplets that are dispersed in a solid polymer matrix. The resulting material is a sort of "Swiss cheese" polymer structure, with liquid crystal droplets filling in the holes. These tiny droplets (in a size of about a few microns across for practical applications) are responsible for the unique behavior of the display layer 120.
• Electrical field 150 can therefore vary an opacity level of the display layer 120 between a first state, i.e. a charged state at which, lights from the rear side 11 OR are allowed to pass through the display layer 120 to the front side 110F, and a second state, i.e. a dormant state at which, lights from the rear side 110R are blocked from passing through the display layer to the front side 110F.
• a first state i.e. a charged state at which, lights from the rear side 11 OR are allowed to pass through the display layer 120 to the front side 110F
• a second state i.e. a dormant state at which, lights from the rear side 110R are blocked from passing through the display layer to the front side 110F.
• SPD suspended particle display
• LCD Liquid crystal display
• a thin PDLC film (about 25 microns thick) is deposited between clear plastic substrates.
• the plastic substrates are coated with a very thin layer of a conducting material known as indium tin oxide ( ⁇ ).
• ⁇ indium tin oxide
• display layer 120 allows light to pass for clear visibility through the projection screen 110.
• the particles disperse and diffuse the light, creating a surface with more than 90% opacity suitable for displaying visual contents from a projector.
• a projection screen 210 includes a display layer, a privacy layer 230 and a base layer 240 structured in a manner similar to that illustrated in the previous embodiments.
• the difference lies in a situation where the display layer includes a plurality of segmented cells, e.g. 220 A, 220B, 220C and 220D.
• Each cell is coupled to an independently controllable electrical field 250A, 250B, 250C and 250D, respectively.
• Cells 220A, 220B, 220C and 220D form into a grid such that the opacity of each cell in the grid can be controlled independently from each other.
• FIG. 7 Shown in Fig. 7 is an application example of projection screen 210 used in a projection system 200 having individual projectors 50A, 50B, 50C and 50D.
• Each projector maybe configured to provide its own visual signals to a corresponding cell 220A, 220B, 220C and 220D.
• the region at one or more cells e.g. cell 220 A as shown in Fig. 7
• the electrical field 250A coupled to cell 220A will be set to the charged state, to control and switch cell 220A to a transparent mode.
• the rest of cells e.g.
• cell 220B, 220C and 220B may be at the dormant state, i.e. at opacity state to display visual contents from projectors 50B, 50C and 50D. As such, lights from external area i.e. the rear side of the projection screen, is blocked such that visual contents can be displayed in a clear manner on cells 220B, 220C and 220D.
• a projection screen 310 includes a base layer 340, a privacy layer 330 attached to base layer 340, and first and second display layers 320A, 320B attached to privacy layer 330.
• Each of the display layers 320A, 320B is coupled to an electrical field 350A, 350B which are independently controllable.
• the opacity level of each display layer 320A and 320B can therefore be controlled individually, hence varies levels of opacity of the projection screen 310 can be obtained by a combination of display layers 320A and 320B, e.g. at a full opacity state, a partial opacity state (translucent), or a transparent state.
• embodiments of the invention is suitable for use in a front- projection system to provide desired display effects.
• a projection screen displays visual contents which is front-projected even if there is a strong light source behind the screen.
• This feature enables an application of the present invention to form a projection screen on a window, i.e. in a meeting room, and provides viewers with the experience of viewing both the projected contents and the scenes outside the window under a controllable manner.
• the projected image in both the opaque and the partially transparent modes are only visible from the projector's side of the screen, hence privacy concern is addressed. Additionally, the projected image (in both the opaque and the partially transparent modes) is not visible regardless of the lighting conditions on the non-viewer side of the screen

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Overhead Projectors And Projection Screens (AREA)
• Projection Apparatus (AREA)
• Transforming Electric Information Into Light Information (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=54193751

Family Applications (1)

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Cited By (2)

Citations (5)

• 2012
  • 2012-05-08 SG SG2012033767A patent/SG195397A1/en unknown
• 2013
  • 2013-04-18 WO PCT/SG2013/000152 patent/WO2013169206A1/fr not_active Ceased
  • 2013-04-18 SG SG11201408631SA patent/SG11201408631SA/en unknown

Patent Citations (5)

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