WO2008087575A1 - Réduction de granularité dans un système de projection - Google Patents

Réduction de granularité dans un système de projection Download PDF

Info

Publication number
WO2008087575A1
WO2008087575A1 PCT/IB2008/050108 IB2008050108W WO2008087575A1 WO 2008087575 A1 WO2008087575 A1 WO 2008087575A1 IB 2008050108 W IB2008050108 W IB 2008050108W WO 2008087575 A1 WO2008087575 A1 WO 2008087575A1
Authority
WO
WIPO (PCT)
Prior art keywords
projection system
scattering
liquid crystal
light
screen
Prior art date
Application number
PCT/IB2008/050108
Other languages
English (en)
Inventor
Rifat A. M. Hikmet
Johannes P. M. Ansems
Ties Van Bommel
Original Assignee
Koninklijke Philips Electronics N.V.
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 Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Priority to JP2009546033A priority Critical patent/JP2010517070A/ja
Publication of WO2008087575A1 publication Critical patent/WO2008087575A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/48—Laser speckle optics
    • 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
    • G03B21/005—Projectors using an electronic spatial light modulator but not peculiar thereto

Definitions

  • the present invention relates to a projection system comprising at least one coherent light source, a modulator for modulating light from said light source, and a lens for projecting modulated light from the modulator onto a screen.
  • the invention also relates to a method for reducing speckle in such a system.
  • laser light sources in projection systems is desirable, seeing the many advantages the laser source provides in comparison to conventional white light sources, which waste a considerable amount of the light energy.
  • the laser In favor of the laser is, for instance, the laser only generating light based on the wavelength of the laser source, its small etendue, and its high efficiency along with a long lifetime.
  • the sources expected to realize the desired laser projection systems are compact and high-power laser light sources.
  • high-power red laser diodes LDs
  • SHG green high-power second harmonic generation
  • In the blue region GaN semiconductor lasers and SHG lasers, using quasi-phase-matched (QPM) devices, have been developed.
  • speckle arises when coherent light scattered from a rough surface, such as a screen, is detected by a square-law detector with a finite aperture, such as an observer's eye.
  • speckle is defined as the random intensity variation that is caused by the random interference of the light.
  • An object with a rough surface, such as a screen when illuminated with coherent light from a laser, exhibits a speckled appearance. Since variations in the surface are greater than the wavelength, coherent light scattered by the individual elements of the surface interferes to form a stationary pattern. The speckle appears to scintillate or sparkle when there is any relative movement of the surface and the observer.
  • Suppression of described speckle can be obtained by diversification of light parameters, of which one parameter is the light scattering angle. Varying the scattering angle quickly and frequently over time will correspondingly cause the speckle pattern to change quickly and frequently over time. If the pattern is altered quickly enough, the eye of the observer will experience the speckle pattern smoothed out, and subsequently no speckle will be observed.
  • US 6 122 023 discloses a laser projection system where the display screen itself acts as a diffuser.
  • the screen is a liquid crystal projection display screen constructed in a highly scattering state. A voltage is applied to the liquid crystal molecules, causing them to vibrate slightly and thereby reduce any speckle typically observed.
  • a projection system comprising a fast switching liquid crystal (LC) element positioned in the optical path between said at least one coherent light source and said lens, and adapted to scatter light passing said LC element; and a driver for varying the scattering of said LC element, so as to introduce angular diversity and thereby suppress speckle in an image on said screen.
  • coherent light source is intended to include any light source providing light that is sufficiently coherent to cause speckle effects.
  • the light source is some kind of laser, e.g. a diode laser, but the invention is not limited to this implementation.
  • a diffuser in the form of a fast switching liquid crystal element scatters the light from the light source.
  • the scattering of the LC element By controlling the scattering of the LC element to be continuously changing whenever light is projected onto the screen, the coherency of the light is removed which reduces the speckle in the displayed image.
  • the diffuser of the present invention is positioned in the optical path between the light source and the projection lens, preferably at a focal point of the optics, such as in an intermediate image plane.
  • the positioning differs from the system disclosed in above- mentioned US 6 122 023, in which the diffuser is integrated with the display, i.e. the screen itself forms the diffuser.
  • the screen onto which the system projects images is relieved from forming the element in which suppression of speckle is performed. Excluding the screen from bringing on the reduction additionally lightens the restrictions on the screen onto which the images are projected. For instance, the screen does not need to comprise material with diffusing characteristics, neither does it need to be applied with voltage. Subsequently, this facilitates the complexity of the screen, or area, onto which the images are projected, thus resulting in cost reductions.
  • the liquid crystal element is preferably integrated with the main unit of the projector. This facilitates the handling of the projection system, as no separate part outside the projector is required to accomplish suppression of speckle. Additionally, positioning the diffuser between the laser and the lens of the projector implies that the lens is the element most immediate to the screen. Arranging the lens closest to the screen is favorable, as the diffuser will then not interfere with the lens focusing the light beam onto the screen.
  • the liquid crystal element can be arranged to scatter the light within a focusing area of collecting optics following said LC element.
  • this collecting optics is the projection lens of the system.
  • the beam profile FWHM i.e. full beam width at half maximum after passing through the diffuser, is less than 45°, and even more preferably less than 20°. Arranging the diffuser so as to scatter the light in the forward direction, within the boundaries of the collecting optics, ensures that light losses are minimal.
  • the scattering variation can be accomplished without introducing intensity variations, the variations will not be detected by an observer, and the rate of variation is not critical. As long as the scattering does not lead to observable intensity variation on the screen it can be very slowly changing.
  • the switching of the liquid crystal element is preferably faster than the reaction of the human eye, i.e. with a frequency greater than around 50 Hz.
  • any impact on the average intensity caused by the scattering is constant.
  • the average intensity of any fully open pixel (letting through maximum light) in each image frame is held constant. Otherwise, this also could be detected by the eye of an observer.
  • the projection system can comprise deflection optics for scanning the modulated light across the screen. Deflection optics are required to form a complete image if the modulator is only adapted to produce a portion of the image which is to be projected.
  • the liquid crystal element can be pixilated, i.e. the diffuser cells can be divided into different controllable switching areas so as to form a patterned morphology. Such controllable areas can be created by structured electrodes. Pixelating the diffuser presents an additional manner in which the diffuser can be arranged to introduce time varying scattering or diffraction. This is for instance relevant for a diffuser comprising a homogenous liquid crystal, such as a ferroelectric liquid crystal material when not comprised in a gel.
  • polarization of the light might be necessary.
  • Liquid Crystal cells require polarized light.
  • polarization preserving LC element is a nematic anisotropic gel with a homogenous orientation. Such a gel scatters only one of the polarizations effectively.
  • liquid crystal element can be a polarization altering diffuser.
  • a polarization altering diffuser will in addition to angular diversity induce polarization diversity, which may serve to even further reduce speckle.
  • Examples of a polarization altering LC element are polymer dispersed crystals (PDLC) or an anisotropic gel including one of nematic, ferroelectric or chiral liquid crystal material.
  • PDLC polymer dispersed crystals
  • anisotropic gel including one of nematic, ferroelectric or chiral liquid crystal material.
  • Figure 1 shows an overview of a laser projection system in accordance with an embodiment of the present invention.
  • Figure 2a shows an example of how a time varying voltage applied to a liquid crystal element in accordance with an embodiment of the present invention affects the scattering of light emitted by the laser over time.
  • Figure 2b shows an alternative of the time varying voltage showed in Figure 2a.
  • Figure 2c shows yet another alternative of the time varying voltage showed in Figure 2a.
  • Figure 1 shows in an exemplifying manner a laser projection system 1 in accordance with an embodiment of the present invention.
  • the system 1 in the illustrated example comprises a laser 2, from which light is emitted.
  • a laser 2 from which light is emitted.
  • the emitted light passes through illuminating optics 3 and is supplied to a modulator 4, which induces an effect for modulating the intensity of the light beam.
  • the modulator 4 can be a single pixel, a line array of pixels, or a two dimensional array of pixels, and it may induce phase change, diffraction, scattering, and refraction as well as deflection.
  • Contrast producing optics 5 can comprise polarisisers, diaphragms, and lenses, such as schlieren optics.
  • the beam next passes through a diffuser 6, i.e. a fast switching liquid crystal element.
  • the diffuser 6 can be placed at an intermediate focal plane in the optical path, and alternatively, elsewhere in the optical path, e.g. in the optics 3, preceding the modulator .
  • the beam passes through deflection optics 7, e.g. a scanner.
  • deflection optics 7 are used to build the entire image by scanning a beam across a screen 9.
  • the light is focused onto the screen 9 by a lens 8, which focuses the modulated light onto the screen 9.
  • the deflection optics 7 can be positioned before the lens 8.
  • the deflection optics 7 can be positioned after the lens 8.
  • Contol electronics 10 control the laser 2, the modulator 4, the deflector 7 as well as the time varying diffuser 6.
  • the screen 9 is designed for front projection and thus the observer 11 is situated on the same side of the screen 9 as the laser front projection system 1, but alternatively, the screen 9 can be designed for rear projection.
  • the screen can be any surface suitable for displaying the image formed by the modulated light. It can be reflective (front projection) or a transmissive (rear projection) screen, depending on the implementation.
  • the diffuser 6 can be a polarization altering diffuser, such as for instance, a polymer dispersed crystal (PDLC) or an isotropic gel diffuser 6 including one of nematic, ferroelectric or chiral liquid crystal material.
  • the diffuser 6 can be a polarization preserving diffuser, such as for instance a switchable nematic anisotropic gel with a homogeneous orientation.
  • the diffuser 6 is arranged to scatter the light within a focusing area of the lens 8. Accordingly, the diffuser 6 scatters the light in small angles, so as to restrict the light beam from spreading outside the focusing area of the collecting optics, thus contributing to the intended image to be projected with high brightness and minimal light losses.
  • the diffuser 6 can be made by polymerization of a mixture reactive molecules and liquid crystals and should it be preferred, the diffuser 6 can also be polymerized in a pattern wise manner to produce a patterned morphology within the cells.
  • a well-known procedure to produce PDLC is by mixing a reactive monomer with a conventional liquid crystal, to obtain an isotropic mixture. Upon polymerization, phase separation is induced leading to the formation of liquid crystal droplets in the polymer matrix. As an electric field is applied to the PDLC system after polymerization, the PDLC system shows scattering effects.
  • Anisotropic gels are obtained by producing a mixture of a monomer and a liquid crystal, which is in the liquid crystal state. Upon polymerization, the system remains macroscopically oriented. As opposed to PDLC, gels are transparent after polymerization. Following applying an electric field, gels become translucent and induce light scattering. Nematic gels with a negative dielectric anisotropy in homotropic orientation show polarization-altering (polarization independent) scattering in the same way chiral gels do. Gels with positive dielectric anisotropy in homogeneous orientation show polarization- preserving (linear polarization direction dependent) scattering. Maximum angular scattering induced by such a system can be adjusted by the layer thickness morphology and the birefringence of the liquid crystal.
  • a time varying voltage 12 is Applied to the diffuser 6 in the illustrated example is the same across the diffuser surface and which can be realized in different ways.
  • the pixilated switching area cells within the diffuser 6 can be induced by using pixilated electrodes, as well as pixilated ferroelectrics is an option.
  • the applied time varying voltage 12 can vary across the surface of the diffuser 6 opposed to being the same across the surface.
  • the time varying voltage 12 generates an electric field pattern.
  • the voltage 12 applied to the diffuser 6 gives rise to a time varying scattering 21a, 21b, 21c ( Figure 2a, 2b, 2c), i.e. angular diversity, of the passing beam.
  • the diffuser cells need to have switching characteristics, which enables switching of the different switching areas within the cells to induce variation in the deflection angle of the scattered light, leading to suppression of speckle.
  • the applied voltage 12 is not necessarily continuous, but can be a pulsed signal 22. Nor does it have to have the same frequency.
  • a pulse negative or positive
  • the effective voltage 22 across the cell and thus the scattering 21a, decreases.
  • Each pulse therefore provides an entire period of scattering variation, as indicated in Figure 2a.
  • the frequency of the varying scattering 21a will be twice that of the voltage 22.
  • the time varying voltage 12 applied to the diffuser 6 can be amplitude modulated. Applying an amplitude modulated voltage 12 makes the amplitude, and not the frequency, of the applied time varying voltage 12 affect the resulting time varying scattering pattern 21b.
  • a high frequency AC voltage 23 is applied, for which the amplitude varies as a function of time, causing the scattering pattern 21b to vary correspondingly.
  • the negative or positive voltage 23 applied to the diffuser 6 is never equal to zero, resulting in that decay of the effective voltage across the diffuser cell is prevented.
  • the frequency of the time varying voltage 12 is not critical.
  • the switching of the diffuser 6 is preferably faster than the reaction of the eye of the observer 11, i.e. a frequency greater than around 50 Hz is required.
  • any impact on the average intensity caused by the scattering 21a, 21b, 21c is preferably constant for each displayed image frame. Otherwise, this also could be detected by the eye of the observer 11.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Liquid Crystal (AREA)

Abstract

L'invention concerne un système de projection (1) comprenant au moins une source de lumière cohérente (2), un modulateur (4) pour moduler la lumière de la source lumineuse et une lentille (8) pour projeter la lumière modulée du modulateur sur un écran (9). Le système comporte en outre un élément (6) à cristaux liquides (LC) à commutation rapide, qui est placé dans le chemin optique entre la ou les sources de lumière cohérente et la lentille (8) et conçu pour diffuser la lumière traversant l'élément LC, ainsi qu'un pilote pour faire varier la diffusion de l'élément LC. La modulation de la diffusion de l'élément LC, visant à la rendre continuellement changeante lorsque la lumière est projetée sur l'affichage, permet de supprimer la cohérence de la lumière, ce qui réduit la granularité de l'image affichée.
PCT/IB2008/050108 2007-01-19 2008-01-14 Réduction de granularité dans un système de projection WO2008087575A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2009546033A JP2010517070A (ja) 2007-01-19 2008-01-14 投影システムにおけるスペックルの軽減

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP07100787.6 2007-01-19
EP07100787 2007-01-19

Publications (1)

Publication Number Publication Date
WO2008087575A1 true WO2008087575A1 (fr) 2008-07-24

Family

ID=39332096

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/IB2008/050108 WO2008087575A1 (fr) 2007-01-19 2008-01-14 Réduction de granularité dans un système de projection

Country Status (3)

Country Link
JP (1) JP2010517070A (fr)
TW (1) TW200846808A (fr)
WO (1) WO2008087575A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010067282A1 (fr) 2008-12-12 2010-06-17 Koninklijke Philips Electronics N. V. Appareil d'éclairage
JP2011215172A (ja) * 2010-03-31 2011-10-27 Hitachi Consumer Electronics Co Ltd レーザープロジェクタ
US8643822B2 (en) 2007-07-03 2014-02-04 Jds Uniphase Corporation Non-etched flat polarization-selective diffractive optical elements
RU2658572C1 (ru) * 2017-01-25 2018-06-21 Общество с ограниченной ответственностью "НаноРельеф Дисплей" Лазерный осветитель
US10209531B2 (en) 2016-01-28 2019-02-19 Japan Display Inc. Optical device and display device

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10451890B2 (en) * 2017-01-16 2019-10-22 Cymer, Llc Reducing speckle in an excimer light source

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19751190A1 (de) * 1997-11-19 1999-05-20 Bosch Gmbh Robert Laseranzeigevorrichtung
WO2000062114A1 (fr) * 1999-04-12 2000-10-19 Deutsche Telekom Ag Procede et dispositif permettant de reduire la formation de speckle sur un ecran de projection
WO2005098532A1 (fr) * 2004-04-09 2005-10-20 Matsushita Electric Industrial Co., Ltd. Affichage d’image laser
JP2005352020A (ja) * 2004-06-09 2005-12-22 Sony Corp 光拡散素子及びスクリーン
EP1734771A1 (fr) * 2005-06-14 2006-12-20 SONY DEUTSCHLAND GmbH Optique d'éclairage, unité d'éclairage, et dispositif de génération d'images

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19751190A1 (de) * 1997-11-19 1999-05-20 Bosch Gmbh Robert Laseranzeigevorrichtung
WO2000062114A1 (fr) * 1999-04-12 2000-10-19 Deutsche Telekom Ag Procede et dispositif permettant de reduire la formation de speckle sur un ecran de projection
WO2005098532A1 (fr) * 2004-04-09 2005-10-20 Matsushita Electric Industrial Co., Ltd. Affichage d’image laser
JP2005352020A (ja) * 2004-06-09 2005-12-22 Sony Corp 光拡散素子及びスクリーン
EP1734771A1 (fr) * 2005-06-14 2006-12-20 SONY DEUTSCHLAND GmbH Optique d'éclairage, unité d'éclairage, et dispositif de génération d'images

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8643822B2 (en) 2007-07-03 2014-02-04 Jds Uniphase Corporation Non-etched flat polarization-selective diffractive optical elements
WO2010067282A1 (fr) 2008-12-12 2010-06-17 Koninklijke Philips Electronics N. V. Appareil d'éclairage
JP2011215172A (ja) * 2010-03-31 2011-10-27 Hitachi Consumer Electronics Co Ltd レーザープロジェクタ
US9122145B2 (en) 2010-03-31 2015-09-01 Hitachi Maxwell, Ltd. Laser projector with reduced speckle
US10209531B2 (en) 2016-01-28 2019-02-19 Japan Display Inc. Optical device and display device
RU2658572C1 (ru) * 2017-01-25 2018-06-21 Общество с ограниченной ответственностью "НаноРельеф Дисплей" Лазерный осветитель

Also Published As

Publication number Publication date
JP2010517070A (ja) 2010-05-20
TW200846808A (en) 2008-12-01

Similar Documents

Publication Publication Date Title
US10571762B2 (en) High dynamic range displays using filterless LCD(s) for increasing contrast and resolution
US9772530B2 (en) High dynamic range displays using filterless LCD(s) for increasing contrast and resolution
KR100533611B1 (ko) 투영형 화상표시장치
KR101918539B1 (ko) 가상 이미지를 이동시키기 위한 이미징 장치
JP6259791B2 (ja) クロスｂｅｆコリメータおよび偏光保存拡散器を備えるデュアルパネルディスプレイ
US7742239B2 (en) Method to control point spread function of an image
JP4598676B2 (ja) ２次元走査型画像表示装置
JP4898121B2 (ja) 画像投影装置
US7784949B2 (en) Illuminator with switching and diffusing elements
US7042535B2 (en) Optical display system and optical shifter
JP5857599B2 (ja) スクリーンおよび画像表示システム
US20120140147A1 (en) Display panel, display system, portable terminal and electronic device
US20090141193A1 (en) Image display apparatus
JPH086023A (ja) 液晶表示装置および液晶投写型装置
WO2008087575A1 (fr) Réduction de granularité dans un système de projection
JP2003149730A (ja) 投射型表示装置
JP2013076956A (ja) 画像表示システムおよび制御装置
US20030058385A1 (en) Liquid crystal display device
Zhang et al. A resolution-enhanced digital micromirror device (DMD) projection system
JPH0594153A (ja) 液晶表示装置と液晶パネルの駆動方法および液晶投写型テレビ
JP4194381B2 (ja) 光偏向装置
JP2002303931A (ja) 照明装置およびこれを用いたプロジェクタ
JP4552412B2 (ja) プロジェクタシステムとその駆動方法
Kikuchi et al. Design and fabrication of a projection display using optically addressed polymer-dispersed liquid crystal light valves
JPH11202785A (ja) 反射型表示装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08702409

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 2008702409

Country of ref document: EP

ENP Entry into the national phase

Ref document number: 2009546033

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 08702409

Country of ref document: EP

Kind code of ref document: A1