Classifications

• • 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
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/133526—Lenses, e.g. microlenses or Fresnel lenses
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
  • H04N5/7416—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal
  • H04N5/7441—Projection arrangements for image reproduction, e.g. using eidophor involving the use of a spatial light modulator, e.g. a light valve, controlled by a video signal the modulator being an array of liquid crystal cells

Definitions

• the field of the invention is that of display devices and in particular that of large flat TV screens, consisting of an active matrix liquid crystal matrix addressing (LCD).
• LCD liquid crystal matrix addressing
• the present invention provides a display device and in particular a flat television screen, comprising a large matrix with a small pixel size in front of the pitch of the image white dots.
• the subject of the invention is a display device comprising a lighting source emitting an Ip radiation, and a spatial light modulator illuminated by the Ip radiation, said modulator consisting of a matrix of NxM elementary pixels (Xj ) of dimensions dfsjxdf / j, the pixels Xj; and Xj + -
• j being separated by a step p j sj, the pixels Xj j and Xjj + being separated by a step p ⁇
• the device comprises means for collimating the radiation Ip in each pixel and in that the step p ⁇ is at least an order of magnitude greater than the dimension df
• the pitch p ⁇ is greater by at least an order of magnitude than the dimension d
• the subject of the invention is also a color display device comprising a display device comprising a light source simultaneously emitting several radiations in ranges of chromatic components (R, G, B) and a spatial light modulator comprising an NxM matrix elementary dots (Dj), each dot comprising at least one elementary sub-pixel per range of chromatic component (XRI; Xvij; X ⁇ i) ⁇ e dimensions d ⁇ xd ⁇ , the sub-pixels XRJ j (Xvjj; X ⁇ jj) being separated from the sub-pixels XR (J + 1) J (Xv (i + 1), j ' ⁇ x B (i + 1), j) by a step pN, the pixels XRJJ (Xvij; X ⁇ j) being separated from the pixels XRJJ + ( Xvij + 1; X ⁇ i, j + 1)
• a P as PM.
• the pitch p ⁇ is at least an order of magnitude greater
• the invention proposes using light sources, more compact than conventional light sources using in particular parabolic reflectors and standard collimators.
• the subject of the invention is also a display device comprising a lighting source which comprises a light source and a light wave guide coupled to said light source, the light wave guide comprising a diffracting element, located along the guide for collimating emerging light rays from the source, in a direction substantially perpendicular to the surface of the waveguide, said surface of the waveguide being substantially parallel to the plane of the spatial light modulator .
• the display device comprises a spatial light modulator in a plane (yox), a light source and means for collimating said source so as to create a collimated beam in a plane (zox ), a first mirror M-
• the anamorphic function can be performed by an index network or a relief network, or even by a set of separating blades.
• the spatial modulator can include filters R, G, B located on the sub-pixels XRJJ, Xvij, X ⁇ ij-
• the spatial modulator comprises a lighting source comprising spatio-chromatic means.
• the spatial modulator does not include filters and, advantageously, the lighting source can comprise a component which can be a diffractive mirror, capable of angularly dispersing the R, G, B components of incident radiation in the case of spatial modulator comprising elementary sub-pixels XRJJ, X JJ, X ⁇ ij. or else another set of dielectric mirrors arranged in a fan shape so as to angularly separate the components R, G, B.
• the subject of the invention is also a method of producing a display device according to the invention, comprising the manufacture of a spatial light modulator constituted by a matrix of N x M elementary pixels on a substrate using several steps masking using masks adapted to define the N x M elementary pixels, the control electrodes and the switching circuits of the spatial modulator, this method being characterized in that: - it comprises the implementation of a network Rj of lenses on the rear face of the substrate intended for producing the spatial modulator;
• FIG. 2 illustrates a second configuration of active matrix used in a display device according to the invention
• FIG. 3 illustrates an example of a display device according to the invention comprising an incident beam of collimated light, two lens arrays and a diffuser;
• - Figure 4 illustrates a first example of a light source which can in particular be used to light an active matrix of the type shown in Figure 1
• - Figure 5 illustrates a second example of a light source, which can in particular be used to light an active matrix of the type shown in Figure 2;
• FIG. 6 illustrates a third example of a light source that can illuminate an active matrix of the type shown in Figure 2;
• - Figure 7 illustrates a first example of mirror M-
• FIG. 8 illustrates a second example of an anamorphic mirror M'i
• FIG. 9 illustrates a third configuration of active matrix used in a three-color display device according to the invention.
• FIG. 10a and 10b illustrate other active matrix configurations used in a three-color display device
• FIG. 11 illustrates a three-color display device
• FIG. 12 illustrates a variant of the three-color display device according to the invention, using another possible configuration for the components M-
• the display device comprises a spatial light modulator of the active matrix liquid crystal type.
• the invention resides in the fact of using pixels of small dimensions compared to the total surface of all the elementary image points.
• FIG. 1 illustrates a first possible configuration of an active matrix comprising a matrix addressing obtained by an array of electrodes Ej, E; capable of electrically controlling NxM elementary pixels, Xj; of liquid crystal type electrooptical material via transistors not shown. It may advantageously be thin film transistors produced in Si amorphous or Si polyc ⁇ staliin technology. In this configuration, the entire surface of elementary pixels remains small compared to the size of the matrix. Indeed, the dimension djsg is at least an order of magnitude less than the step p ⁇ , the dimension d ⁇ possibly being of the order of magnitude of the step p ⁇ .
• Figure 2 illustrates an active matrix similar to that of Figure
• a light source, collimation means and means for focusing the light in the different pixels Xj are used.
• FIG. 3 illustrates a display device according to the invention, comprising an R- network
• may include N cylindrical lenses.
• the network R- j can comprise NxM spherical lenses, the pitch of the network being of the order of the parameter p j s j (or p ⁇ , PM being close to pj ).
• the display device can conventionally comprise a second network R2 of lenses, identical to the network R- ⁇ and generating a beam whose intensity has been modulated by each liquid crystal pixel Xj as a function of the signals electrical applied to the electrodes Ej and Ej.
• This collimated beam towards an observer can be scattered by a diffuser D, so as to adapt the radiation diagram of the display device.
• the device of the invention comprises means for collimating an incident beam to illuminate the network R ⁇ of lenses, upstream of the liquid crystal matrix.
• a fairly conventional solution consists in coupling the light source 11 to a light guide 13 using a collimator 12.
• the rays of the source propagating by total reflection inside the guide.
• the two faces of the guide not being parallel, the angle ⁇ which they form is calculated so as to gradually reduce the light rays which propagate towards the normal to the guide, so as to extract them from the latter to provide consistent lighting.
• a set of prisms of index np makes it possible to reflect in the direction perpendicular to the guide of index ng the rays extracted from the latter, which emerge in an oblique direction (the angles at the base of these premiums being very close to 45 e and np>ng> 1) (see figure 4).
• the light extracted from the guide is collimated in a zox plane. It can therefore be focused in the z direction using a cylindrical lens matrix (cylinder axis // y).
• the diffracting element located along the guide may advantageously be a holographic element constituted by a layer of material comprising an index network, organized in strata. The strata are oriented at about 45 ° relative to the axis of the light waveguide.
• FIG. 5 illustrates such a compact collimated source.
• the light source 21 is coupled to a light guide, by a collimator 22.
• the diffracting element 24 is placed at the heart of the guide 23 and diffracts from the emerging rays in a direction perpendicular to the plane of the guide, represented by the plane zoy, if the guide is a plan guide in the yox plan.
• This collimated lighting source is arranged parallel to the active matrix and to the plane array R-j of cylindrical lenses.
• the diffracting element can advantageously be a holographic element obtained by interference of two coherent beams in the plane of a photosensitive layer.
• the holographic element can be produced by developing an index network having strata of indices oriented in a z'oy plane making an angle of 45 ° with the zoy plane.
• the photosensitive layer can typically be dichromate gelatin or photopolymer.
• the waveguide coupled to the light source can advantageously have a dihedral structure so as to bring emerging rays into the hologram capture cone corresponding to all of the angles of incidence for which the hologram is diffracting in the z'oy plane.
• This type of lighting source configuration makes it possible to effectively collimate the light flux in the plane zoy on the elementary pixels Xj after focusing by the network R-j, the small dimension df along the axis x represented in FIG. 4.
• the display device can include another lighting source delivering a light flux collimated in the zoy plane, and also collimated in the zox plane.
• FIG. 6 illustrates this light source comprising a light source 31, a collimation lens 32, an anamorphic mirror M-j and a second mirror M2.
• the collimated luminous flux coming from the source 31, is reflected by the mirror M-
• the mirror M- ⁇ has a particular structure of the relief network or index type with strata oriented at 45 ° from the axis ox.
• FIG. 7 shows diagrammatically an example of an M-] mirror which can also be of the holographic type with a grating function with high diffraction efficiency, recorded for example in a photopolymer material.
• a second M2 mirror collimates the light flux spread over the entire surface of the active matrix.
• This mirror has a structure similar to that of the mirror M-
• the anamorphic mirror M mentioned above can be replaced by an optical component M'1 consisting of N separating plates at 45 °.
• the reflection-transmission coefficient RjTj of these plates can be adjusted so that the light intensity is distributed uniformly over the array of microlenses, therefore over the electrooptical pixels after focusing.
• the position of this element is not critical given the distance between pixels which can typically be of the order of 300 ⁇ m to 1 ⁇ m.
• Two components of this type M 'and M'2 are used for producing compact collimated lighting from a short arc lamp.
• the means of producing these components are of molding-pressing techniques (see FIG. 8).
• the lighting sources described above are particularly advantageous in the case of a color display screen and allow lighting practically perpendicular to the plane of the screen.
• the active matrix has a dot consisting of sub pixels XjRj, Xjvj and XjRj as illustrated in FIG. 9. It should be noted that the invention is compatible with a distribution of the pixels such as that proposed in FIGS. 10a and 10b.
• the active matrix is then made up of pixels of square shape (50 ⁇ 50 ⁇ m typically), or of rectangular shape (50 ⁇ m ⁇ 300 ⁇ m) with a spatial period in the horizontal direction of the order of 300 ⁇ m. In the vertical direction, the spatial period of these elementary pixels is 1 mm.
• a “white” pixel then consists of three equidistant RGB elementary pixels whose pitch is 300 ⁇ m. Color image case with color filters
• the device of the invention can associate with the various aforementioned lighting systems, a spatial modulator which includes RGB filters located on the sub-pixels XV, B, R.
• a spatial modulator which includes RGB filters located on the sub-pixels XV, B, R.
• RGB filters located on the sub-pixels XV, B, R.
• the realization of an efficient lighting system requires the implementation of a matrix of cylindrical or spherical lenses according to the geometry of the pixels to focus the lighting in the transparent zone of the pixels.
• the pitch of this lens matrix will either be equal to the period of the white pixels when the sub-pixels are grouped according to an organization of the grouped sub-pixel type, or equal to the period of the sub-pixels when the latter are equally distributed in the white sub-pixel.
• the microlens array and the means of chromatic dispersions by diffractive grating and / or by three-color separator of the dielectric mirror type are adapted to the generation of the RGB spectral components focused selectively in the pixels of the LCD screen.
• the microlens array is used to selectively focus the collimated light from the compact lighting system in the electrooptical pixels.
• a first type of three-color separator can consist of a set of dielectric mirrors arranged in a fan so as to angularly separate the RGB components. This separator is placed at the output of the light source and upstream of a collimation assembly of the Mi and / or M2 components type mentioned above.
• the component Mi or M2 has a chromatic separation function.
• a light source 20 comprising the red, green and blue spectral components
• the collimated and then spread out light flux is diffracted on the mirror M2 which can have a diffracting structure such that it also performs the function of chromatic separation as illustrated in FIG. 11.
• the beams of red, green, blue light can illuminate the network R-
• the second array of lenses with focal length f / 2 generates the image of a “white” pixel in a symmetrical plane of the liquid crystal screen by compared to the second microlens array. In this plane, the diffuser D or a Fresnel type screen is placed which directs the light towards the observer.
• the beams thus generated are focused respectively on the elementary sub pixels XRJ J, X ⁇ ⁇ j and X ⁇ j j.
• Such a configuration is particularly compact insofar as the network of lenses R ⁇ is in contact with the diffractive component M'2.
• can be combined in a com posing a single diffractive effect performing both the focusing function and the dispersion function.
• This type of component has been described by the applicant in a previous patent application (publication no. 2,711,878).
• an extremely compact structure typically a thickness of the order of 50 mm
• large dimensions typically greater than 800 x 600 mm 2 .
• the invention also proposes an original and direct method for producing the active matrix by using masking steps directly through the lens array R-
• the elementary pixels of the active matrix had a surface, equivalent to the pupil of the lenses of the array Ri, it was therefore not possible with prints close to the thickness of the substrate of the active matrix, d '' imaging large areas from the lenses used. According to the invention this becomes possible due to the areas of elementary pixels clearly smaller than those of the pupils of the lenses.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Nonlinear Science (AREA)
• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Mathematical Physics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Liquid Crystal (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

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• 1996
  • 1996-11-05 FR FR9613454A patent/FR2755530B1/fr not_active Expired - Fee Related
• 1997
  • 1997-11-05 JP JP10521104A patent/JP2000503423A/ja active Pending
  • 1997-11-05 US US09/091,845 patent/US6069728A/en not_active Expired - Lifetime
  • 1997-11-05 EP EP97913252A patent/EP0880724A1/de not_active Withdrawn
  • 1997-11-05 WO PCT/FR1997/001980 patent/WO1998020390A1/fr not_active Application Discontinuation

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