WO2002041074A1 - Ecran de projection holographique - Google Patents

Ecran de projection holographique Download PDF

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Publication number
WO2002041074A1
WO2002041074A1 PCT/DK2001/000769 DK0100769W WO0241074A1 WO 2002041074 A1 WO2002041074 A1 WO 2002041074A1 DK 0100769 W DK0100769 W DK 0100769W WO 0241074 A1 WO0241074 A1 WO 0241074A1
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WO
WIPO (PCT)
Prior art keywords
screen
particles
projection
image
less
Prior art date
Application number
PCT/DK2001/000769
Other languages
English (en)
Inventor
Erik Clausen
Original Assignee
Scan Vision Screen Aps
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Scan Vision Screen Aps filed Critical Scan Vision Screen Aps
Priority to AU2002223510A priority Critical patent/AU2002223510A1/en
Publication of WO2002041074A1 publication Critical patent/WO2002041074A1/fr

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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

Definitions

  • the present invention relates to a translucent, light diffusing screen for use as a transmission rear projection screen.
  • rear projection In general, the concept of rear projection is to arrange an image source behind a screen which projects light forwards along a projection axis towards the screen with a view to forming an image on the front of the screen that is visible to a viewer.
  • the projection screen was perfectly clear the light rays would pass through the screen unhindered and no image would be formed. In order to make the image visible to the viewer, it is necessary to incorporate a diffusion component that spreads the incoming light in order to thereby make the image visible for the viewer.
  • a first type of particles serves as a refractive agent, for which the refraction index deviates from the refraction index for the material in which the refractive agent is situated or dispensed, such that light entering and leaving the particles will be refracted and thereby made visible.
  • this type of particles is more or less translucent, allowing light to pass there through at least partially, thus being transparent or se itranspar- ent.
  • Typical materials used for this purpose include glass and quartz particles.
  • the particle size is preferably at least 1 ⁇ m.
  • This type of light diffusion material is often used for screens which are used in combination with a rear lens element for converting the diverging light beams from the image source to parallel beams before entering the light diffusing screen thereby minimizing decline in the luminance at the edge region of the projection screen.
  • the screen may be provided on the viewer-oriented surface thereof with a further lenticular lens system controlling the horizontal distribution of light, especially enhancing the luminance of an image throughout the viewing angle .
  • a different type of particles serves as a scattering agent, which means that diffusion of the incoming light primarily is produced by irregularly reflected light from the surfaces of the particles.
  • the irregular or disordered reflections are due to both the inherent material properties of the particles as well as to their surface structure.
  • Materials used for this purpose typically absorb most light which enters the particles and can thus be said to be substantially non-transparent or to posses only a very limited transparency.
  • Typical materials used for this purpose include calcium and magnesium carbonate as irregularly formed grains, i.e. having sand-corn like configuration.
  • refractive particles when added to a transparent matrix to a certain degree will have an opaquing effect.
  • the two types of particles are often used in combination to achieve the best possible transmission of light as well as providing an image which possesses a high degree of luminance, contrast as well as correctly balanced colours. Indeed, depending on the surface configuration of the transparent particles, also these will provide a certain, small degree of light scattering, however, to the skilled person, the two types of particles can be readily identified in accordance with their general properties.
  • the resulting screen will appear to be "white” or opaline to a greater or lesser extent in ambient lighting conditions, i.e. without illumination from an imaging system.
  • the whiteness is a function of light scattering of the ambient light entering the screen.
  • holographic projection screens Recently a different type of projection screen has been proposed and is generally known as "holographic" projection screens. It is to be noted that these screen when used as intended cannot be considered to provide a "true” holographic representation of an item, i.e. a "true” three-dimensional representation which will change as the viewer moves relative to the created image.
  • the image created on a "holographic" projection screen is a normal two-dimensional representation of an object, the term “holographic” being used merely to indicate that the projection screen is substantially fully transparent when an image is not projected thereon, and thereby “invisible” to a viewer.
  • a known screen of this type is the HoloProTM marketed by G+B Pronova GmbH, Bergish Gladback, Germany and appears to correspond to the screen disclosed in WO 99/64902. More specifically, the therein-disclosed screen comprises a substantially transparent screen on a surface of which are arranged "holographic-optical” elements, i.e. a system of lens elements. These elements posses a micro- structure which is substantially invisible in ambient light conditions, however, when an image is projected thereon under specified conditions (e.g. projecting angle) an image is created, however, it is only fully visible within a specified viewing angle.
  • a similar screen is manufactured by DNP and sold as the "ProScreen Holo Screen", however, all screen of this type have in common that they are very expensive.
  • the object of the present invention is to provide a projection screen suitable for use as a "holographic" screen, i.e. having a high degree of transparency when an image is not projected thereon, yet allowing a projected image to be formed thereon, which can be used under various conditions and which can be manufactured in a cost effective and efficient manner.
  • the present invention is based on the realisation that a holographic screen can be provided by adapting the principles embodied in the traditional projection screens, i.e. comprising light diffusing particles, and thus a de- parture from the hitherto used micro-lens based screens.
  • a "minimally" opaline screen can serve as a holographic screen, the degree of opacity allowing a rear-projected image to be created, the screen having a degree of transparency which under most conditions will allow the screen to be considered “invisible” by the user.
  • the "invisibility” is to a certain degree based on psychological effects, e.g. if an "interesting" object is placed behind the screen, the interested viewer will "over-look" a certain small degree of opacity.
  • the screen according to the invention is inherently insensitive to the projection angle as well as the viewing angle, this providing for easy of use as well as a high degree of visibility of the projected image, this in contrast to the lens based systems which will only function as intended within narrow angle intervals .
  • a projection screen comprises an amount of up to 5 g, preferably less than 3 g and most preferably less than 1 g, of light scattering particles per m 2 of screen projection surface distributed in the body thereof, however, depending on the type of particles, the amount may be as low as 0,1 g of light scattering particles per m 2 .
  • the particles are mainly in the form of substantially non-transparent particles having a grain size of less than 20 ⁇ , preferably less than 10 ⁇ m, however, depending on the type of particles, the size may be as small as 1 ⁇ m or less.
  • the screen body preferably has a thickness of 3-10 mm.
  • the actual distribution of the light diffusion particles will influence both the degree of opacity as well as the experienced quality of the created image. For example, if the particles are concen- trated in a relatively thin layer, as in a coating or a limited structure, a smaller amount of particles (per m 2 ) will provide a given opacity, however, as at the same time the image is created in a narrow plane, the individ- ual pixels of a pixel-based image (as from an LCD projector) will be more apparent to a viewer. In contrast, a larger amount of particles will be needed to provide a given opacity when distributed throughout the matrix of the screen, however, as at the same time the particles will have a de-pixelating effect by slightly "blurring" the created image.
  • all or a portion of the light scattering particles may be located in a coating or a foil-sheet laminated onto the screen body.
  • the coating or foil-sheet comprises an amount of up to 2 g, preferably less than 1 g, of light scattering particles per m 2 of screen projection surface, the screen body comprising less than 1 g of light scattering particles per m 2 .
  • opaline plastic materials such as white plastic used for carrying bags
  • will scatter light mainly for light from the short wavelength range of the spectrum, i.e. the blue-green range, however, more long waved light from the red range of the spectrum has a tendency to pass directly through the plastic material.
  • This phenomenon can be easily observed when a white plastic bag is held in front of a conventional incandescent light bulb whereby the glowing filament can be observed as a reddish spot which will blind if the light is strong.
  • the screen comprises up to 1 % (volume) of re- fractive particles with a particle size of more than 1 ⁇ m, preferably 2-10 ⁇ m.
  • the invention provides a method for establishing a "holographic" image, the method comprising the steps of arranging a projection screen in a substantially vertical position (i.e. +/- 20 degrees), arranging an image source having an optical projecting angle of 10- 45 degrees relative to the horizontal plane and such that an image is projected on the screen, the screen compris- ing light scattering particles allowing a picture to be created corresponding to the screen, yet having a low degree of opacity, preferably as disclosed above.
  • the screen comprises no optical lens elements on the surfaces thereof.
  • fig. 1 shows a schematic representation of a set-up for rear-projecting an image onto a screen
  • fig. 2 illustrates a Keystone compensated image as well as a non-compensated image
  • fig. 3 shows an example of a preferred use situation for a holographic screen in accordance with the invention
  • fig. 4 shows a first preferred embodiment of a holographic projection screen
  • fig. 5 shows a further preferred embodiment of holographic projection screen.
  • Fig. 1 shows a schematic representation of a projection screen in accordance with the invention in combination with a rear projection image source.
  • a rear projection screen 10 having co- planar rear and front surfaces 11, 12 defining a general plane is arranged in a vertical position.
  • an image source 20 e.g. LCD projector
  • the image source and the axis being arranged with a tilt angle of 20 degrees with respect to horizontal, the image source being pointed towards the rear surface of the screen thereby creating a picture image.
  • a trapezoidal picture 30 will be created as illustrated in fig. 2.
  • the projector may be provided with a so-called Keystone correction providing a compensated, right-angled picture 31.
  • Fig. 3 shows an example of a preferred use situation for a holographic screen in accordance with the invention.
  • a holographic projection screen 60 is arranged, which due to its minimal opacity will not be recognised as such by a viewer glancing at the items put on display in the window.
  • the high position of the image source makes it unlikely that a viewer will look directly into the filament of the image source, which allows that a screen can be used which contains substantially no light refracting particles for refracting the long waved red light.
  • the holographic screen may also be used for other purposes, for example for displaying information in a public room such as in an airport.
  • Fig. 4 shows a first embodiment of a screen 100 according to the invention.
  • the screen comprises a first planar surface 101 and an opposed co-planar second surface 102.
  • the body of the screen comprises a transparent matrix a- terial 110 in which particles 111 are distributed.
  • the particles are evenly distributed in the matrix, the two surfaces can be considered to be identical, i.e. it is immaterial which side is oriented towards the image source respectively the viewer.
  • the particles are irregularly formed grains of calcium carbonate (CaC0 3 ) having a size of less than 10 ⁇ m, preferably less than 5 ⁇ m serving primarily as light scattering agent.
  • the calcium carbonate particles may be partly or fully replaced by par- tides made from MgC0 3 , A1 2 0, Ti0 2 , BaS0 4 , ZnO, BaC0 3 or Al(OH) 3 or mixtures thereof, but preferably at least 50 % is CaC0 3 .
  • the body preferably has a thickness of 3-10 mm containing less than 5 g of particles per m 2 of projection surface.
  • a screen comprises 0,01-0,1 g of particles per m 2 of projection surface, the particles having a size of less than 1 ⁇ m, preferably less than 0,5 ⁇ m.
  • Fig. 5 shows a second embodiment of a screen 200 accord- ing to the invention.
  • the coated screen comprises a screen body 210 having a first planar surface 211 and an opposed co-planar second surface 212.
  • the body of the screen is made from a transparent (matrix) material which in the shown embodiment comprises substantially no dif- fusing particles.
  • a coating 213 comprising diffusing particles 221 in a transparent coating-matrix 220, which preferably may be of the same type as described with reference to fig. 4.
  • the coating preferably has a thickness of 50-200 ⁇ m containing less than 2 g, preferably less than 1 g, of particles per m 2 of projection surface.
  • a thin foil may be laminated onto a surface of the screen body.
  • a foil preferably has a thickness of 0,1 - 1,0 mm containing less than 2 g, preferably less than 1 g, of particles per m 2 of projection surface in a transparent matrix.
  • the composite screens may be used with either surface arranged towards the image source.
  • particles may be desirable to add particles also to the screen body, preferably in an amount corresponding to a total amount of less than 5 g of particles per m 2 of projection surface for the coated screen.
  • the matrix for the screen body may be formed from any suitable transparent polymer such as polystyrene (PS) , acrylics such as polymethyl methacrylate (PMMA) , PET-G or a polycarbonate (PC) as well as mixtures thereof.
  • PS polystyrene
  • PMMA polymethyl methacrylate
  • PC polycarbonate
  • a dye may be added to the matrix, for example green, blue or grey.
  • a light refracting agent e.g. for compensating for the unhindered transmission of red light
  • an amount of light refracting particles having a particle size in the range of 1-10 ⁇ m and preferably in a concentration of less than 1 % (volume) may be added, for example as quartz or glass particles, either in granular, spherical or globular form.
  • a fully transparent screen manufactured from PMMA was provided.
  • a liquid acrylic lacquer 1,5 g of a calcium carbonate (CaC0) paste was added, the paste being of the same type as in example 1.
  • the particle-containing solvent was distributed evenly over one of the screen surfaces and allowed to evaporate and harden, the resulting screen having a coating with an approximate thickness of 0,1 mm containing 0,9 g of particles per m 2 of projection surface.
  • the screen again had a light milky appearance allowing a substantially unnindered view to items placed behind the screen, yet creating a well- defined image with good colour saturation and contrast but again slightly more pixelating of the LCD projector generated image.
  • the third screen contained only around 40 % of the particles per m 2 of projection surface as compared to the first screen, due to the distribution in a thinner layer, the degree of opacity was not reduced correspondingl .
  • EXAMPLE 4 For a screen having a surface area of 1 m 2 and a thickness of 5 mm, 5 kg of liquid PMMA having a density close to 1 g per cm 2 was prepared. To the PMMA 0,025 g of titanium dioxide (Ti0 2 ) powder was added. According to the specification the powder contained particles having a grain size of less than 0,2 ⁇ m and with an average grain size of 0,19 ⁇ m. The particle-containing PMMA was poured into a closed mould and the PMMA was allowed to harden before the particles would start to settle, the resulting screen containing 0,025 g of particles per m 2 of projection surface.
  • Ti0 2 titanium dioxide
  • the screen had a light milky appearance allowing a substantially unhindered view to items placed behind the screen, yet creating a well-defined image with good colour saturation and contrast of the LCD projector generated image. It was noted that the created image was very well defined when seen from lateral angles.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Overhead Projectors And Projection Screens (AREA)
  • Optical Elements Other Than Lenses (AREA)

Abstract

L'invention concerne un écran translucide, à diffusion lumineuse, convenant comme écran « holographique » à projection par transparence. L'écran, qui est opalin à un degré minimal, sert d'écran holographique, le faible degré d'opacité permettant la création d'une image par transparence. Le degré de transparence de l'écran est tel que dans la plupart de conditions l'écran est considéré comme « invisible « par l'utilisateur. De manière plus spécifique, cet écran contient une quantité de particules de diffusion lumineuse inférieure à 5 g par m2 de surface de projection de l'écran.
PCT/DK2001/000769 2000-11-20 2001-11-20 Ecran de projection holographique WO2002041074A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002223510A AU2002223510A1 (en) 2000-11-20 2001-11-20 Holographic projection screen

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DKPA200001737 2000-11-20
DKPA200001737 2000-11-20
DKPA200100566 2001-04-05
DKPA200100566 2001-04-05

Publications (1)

Publication Number Publication Date
WO2002041074A1 true WO2002041074A1 (fr) 2002-05-23

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ID=26068915

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK2001/000769 WO2002041074A1 (fr) 2000-11-20 2001-11-20 Ecran de projection holographique

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AU (1) AU2002223510A1 (fr)
WO (1) WO2002041074A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004072722A2 (fr) * 2003-01-15 2004-08-26 Saint-Gobain Glass France ECRAN DE RETROPROJECTION et/ou de PROJECTION
CN100465819C (zh) * 2007-02-09 2009-03-04 上海大学 基于悬浮粒子幕的光电再现空间影像装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3751135A (en) * 1971-06-25 1973-08-07 E Clausen Rear projection screen
EP0464499A2 (fr) * 1990-06-22 1992-01-08 Sumitomo Chemical Company, Limited Matériau anisotropique diffusant la lumière, son procédé de production et lentille lenticulaire pour écran de projection de télévision
JPH04324848A (ja) * 1991-04-25 1992-11-13 Nec Home Electron Ltd 透過型スクリーンおよびその製造方法および光拡散剤
EP0561551A1 (fr) * 1992-03-20 1993-09-22 Rohm And Haas Company Ecrans de projection par transparence à deux couches
WO2000068712A1 (fr) * 1999-05-11 2000-11-16 Microsharp Corporation Limited Materiau d'ecran a contraste eleve

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3751135A (en) * 1971-06-25 1973-08-07 E Clausen Rear projection screen
EP0464499A2 (fr) * 1990-06-22 1992-01-08 Sumitomo Chemical Company, Limited Matériau anisotropique diffusant la lumière, son procédé de production et lentille lenticulaire pour écran de projection de télévision
JPH04324848A (ja) * 1991-04-25 1992-11-13 Nec Home Electron Ltd 透過型スクリーンおよびその製造方法および光拡散剤
EP0561551A1 (fr) * 1992-03-20 1993-09-22 Rohm And Haas Company Ecrans de projection par transparence à deux couches
WO2000068712A1 (fr) * 1999-05-11 2000-11-16 Microsharp Corporation Limited Materiau d'ecran a contraste eleve

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004072722A2 (fr) * 2003-01-15 2004-08-26 Saint-Gobain Glass France ECRAN DE RETROPROJECTION et/ou de PROJECTION
WO2004072722A3 (fr) * 2003-01-15 2005-03-24 Saint Gobain ECRAN DE RETROPROJECTION et/ou de PROJECTION
US7609443B2 (en) 2003-01-15 2009-10-27 Saint-Gobain Glass France Projection and/or rear projection screen
CN100465819C (zh) * 2007-02-09 2009-03-04 上海大学 基于悬浮粒子幕的光电再现空间影像装置

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Publication number Publication date
AU2002223510A1 (en) 2002-05-27

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