WO1991018315A1 - Light source for image projector - Google Patents

Light source for image projector Download PDF

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Publication number
WO1991018315A1
WO1991018315A1 PCT/FR1991/000351 FR9100351W WO9118315A1 WO 1991018315 A1 WO1991018315 A1 WO 1991018315A1 FR 9100351 W FR9100351 W FR 9100351W WO 9118315 A1 WO9118315 A1 WO 9118315A1
Authority
WO
WIPO (PCT)
Prior art keywords
enclosure
projector according
light
osn
outlet opening
Prior art date
Application number
PCT/FR1991/000351
Other languages
French (fr)
Inventor
Jean-Claude Lehureau
Bruno Mourey
Original Assignee
Thomson-Csf
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 Thomson-Csf filed Critical Thomson-Csf
Publication of WO1991018315A1 publication Critical patent/WO1991018315A1/en

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Classifications

    • 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
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • G02B27/0927—Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
    • G02B5/021—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
    • 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]
    • H04N9/3141—Constructional details thereof
    • H04N9/315—Modulator illumination systems
    • H04N9/3152—Modulator illumination systems for shaping the light beam
    • 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
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133605—Direct backlight including specially adapted reflectors

Definitions

  • the invention relates to an image projector, and more particularly a light source intended for use in particular in television projectors using a liquid crystal screen.
  • the radiation pattern of a light source is most often ill-suited to achieve homogeneous illumination of an object to be projected, without losing a considerable part of the light produced by the source.
  • the radiation diagram of a light source shows a non-homogeneous luminance in the near field, and a directional emission (far field) more homogeneous. It is generally the directional emission that is made to correspond to the object to be projected, using in particular dioptric systems or parabolic mirrors.
  • the use of a dioptric system or a parabolic mirror leads to a strong limitation of the efficiency of light collection. In the first case, this limitation is linked to the vignetting effect: for 30% loss of luminance at the edges, the efficiency is around 50%; and in the second case, only 50% of the flux can be easily collected due to practical limitations in the size of the mirror.
  • the object of the present invention is to remedy the drawbacks mentioned above. It relates to an image projector and particularly a light source of which the new arrangement makes it possible to obtain a uniform illumination of an object to be projected while improving the efficiency of light collection.
  • the invention can be implemented using practically all types of light and all means for producing it, and it finds a particularly advantageous application in television projectors using a liquid crystal screen.
  • an image projector comprising at least one light source, the source producing light intended to illuminate an object having a given shape, is characterized in that it also comprises an enclosure having diffusing internal walls and not very absorbent by which the light is diffused before leaving the enclosure by at least one exit opening, and in that the shape of the exit opening is substantially the same as the shape of the object.
  • the walls of the enclosure are diffusing and white, the multiple diffusions of light in this enclosure which constitutes an integrating enclosure, make it possible to obtain through the outlet opening a luminance of very great homogeneity.
  • the light source can be contained in the enclosure, and the luminance through the outlet opening will be all the more homogeneous the lower the angle at which the source is seen, and the efficiency of light collection will be all the better as the shape of the outlet opening is close to that of the object.
  • FIG. 1 schematically shows an image projector according to the invention, the projector being of a type in which the object to be projected is a liquid crystal screen
  • - Figure 2 shows schematically a version of the projector of the invention in which the object to be projected is practically in contact with an opening of an enclosure shown in Figure 1
  • - Figure 3 shows schematically a version of l invention in which a light source shown in Figure 1 is located outside the enclosure.
  • FIG. 1 shows by way of nonlimiting example an image projector 1 according to the invention, the object of which to be projected is a liquid crystal screen 2.
  • the liquid crystal screen conventionally defines an image, a television image for example which is projected onto a screen (not shown) using a projection lens 3.
  • the liquid crystal screen 2 modulates the light supplied by a light emitting device 5 comprising a light source 6.
  • the emitting device 5 further comprises an enclosure 7 whose internal walls 8 are diffusing and not very absorbent.
  • the light produced by the source 6 is introduced into the enclosure 7 by the fact that the source 6 is contained in the enclosure 7.
  • the enclosure 7 has an outlet opening 9, intended for the passage of light produced by the source 6, the shape of the outlet opening 9 being substantially the same as that of the object to be projected, i.e. the same as that of the liquid crystal screen 2.
  • the enclosure 7 has an ovoid shape, however this shape may be different; but preferably the interior walls 8 must extend without too many sudden changes in their direction, so as not to unnecessarily multiply the reflections in the enclosure 7 and limit the absorption of light before the latter emerges through the outlet opening 9.
  • the enclosure 7 is represented by a sectional view along its largest dimension D1, and it is centered on an optical axis 10.
  • the outlet opening 9 is also centered on the axis optics 10, as well as the projection objective 3, the liquid crystal screen 2, a condenser 11 (disposed between the screen 2 and the emitter 5) and a field lens 12 interposed between the condenser 11 and the liquid crystal display 2.
  • the outlet opening 9 has a shape similar to that of the liquid crystal screen 2 so as to adapt the luminance homogeneity to the object to be projected, and thus significantly increase the overall efficiency of the projector 1.
  • the outlet opening 9 has a height h parallel to the width 11 of the liquid crystal screen 2 and a length (perpendicular to the plane of Figure 1) such that the ratio of the latter length to this height h corresponds roughly in 16: 9 format.
  • the light source 6 is of a conventional type. It produces light that can be both coherent and non-coherent, as well as monochromatic or across the whole visible spectrum.
  • the light source 6 is mounted in the enclosure 7 and supplied by means in themselves conventional, not shown.
  • the source 6 is arranged in the enclosure so that it is seen at a low angle (from the condenser 11) and preferably outside the optical axis 10, so that most of the rays of light r are scattered in enclosure 7 before leaving it through opening 9, as illustrated in FIG. 1.
  • the enclosure 7 does not have perfectly white walls and being open onto a black space through the opening 9, an average luminance L of the enclosure 7 can be expressed as a function of the relative surfaces of the source Ss, of the enclosure Se and opening So:
  • the luminance through the opening 9 is characterized by very high homogeneity if the angle under which the source is seen is small. It is this property that is used to obtain uniform illumination of the object to be projected, namely the liquid crystal screen 2 in the example.
  • the efficiency of the enclosure is defined by the So / Se ratio. (l-Re) + So.
  • the absorption 1-Re of the surface of the enclosure can be as small as 1%, also the efficiency of the enclosure can be very high even if to obtain good luminance, the surface So of the opening 9 does not may be large in front of that of the source and if, to obtain good homogeneity of luminance, the area Se of the enclosure 7 must be large in front of that of the source 6.
  • the light which emerges through the opening 9 is captured at least in part by the condenser 11 and constitutes a beam 15.
  • the outlet opening 9 constitutes a light source which has excellent luminance homogeneity, which makes it possible to form the image of the opening 9 on the liquid crystal screen 2 by the condenser 11 which is located near the opening 9; and the field lens 12 forms the image of the condenser 11 on the pupil (not shown) of the projection objective 3.
  • the aperture 9 which is used, then that in the prior art, only a fraction of the light which forms the far field can be used.
  • the overall efficiency can be further improved by interposing an interference filter system returning all the rays that emerge from the enclosure beyond a certain incidence.
  • an interference filter 16 shown in dotted lines
  • a system of interference filters can be applied against the outlet opening 9, the plane of the interference filter being normal to the optical axis 10.
  • the effect of the interference filter 16 is to give the outlet opening 9 an emission diagram highly concentrated on the optical axis 10.
  • interference filters are in themselves well known. They are produced by superposition of thin layers of alternately weak and strong indices. The precise calculation of the thickness of the successive layers is part of the known art in optical processing, and this calculation takes into account the wavelength of the radiation.
  • a system of interference filters 16 can comprise, along the optical axis 10, successively several interference filters each acting for a given wavelength.
  • FIG. 2 illustrates an embodiment, authorized by the presence of a system 16 of interference filters, and which is advantageous in that it makes it possible to place the light source constituted by the opening 9 practically in direct contact, with the object to be projected, that is to say the liquid crystal screen 2; opening 9 thus being able to have practically the same dimensions as the liquid crystal screen 2.
  • the opening 9, the liquid crystal screen 2 and the projection lens 3 are aligned and centered on the projection axis
  • the source 6 is contained in the enclosure 7, and the outlet opening 9 of the latter has substantially the dimensions of the liquid crystal screen 2.
  • the outlet opening 9 is closed by the interference filter system 16; and between the latter and the liquid crystal screen 2, a field lens 17 is interposed which ensures the convergence of all the rays on the pupil of the projection objective 3, pupil whose plane 18 is symbolized in dotted lines on FIG. 2.
  • a field lens 17 is interposed which ensures the convergence of all the rays on the pupil of the projection objective 3, pupil whose plane 18 is symbolized in dotted lines on FIG. 2.
  • the diffusing enclosure or integrating enclosure such as enclosure 6 makes it possible to reshape the distribution of luminance: by making in the enclosure an outlet opening having the size and / or the shape of the object to be projected, and the enclosure constituting an integrating enclosure which contains the light producing source, the usual organization of the radiation directions is disrupted, "disorder is created” and the beams are selected suitable by recycling others.
  • FIGS. 1 and 2 can in certain cases pose implementation problems, linked in particular to the presence of a hot element in the enclosure 6.
  • FIG. 3 illustrates a new version of the invention in which, as in the previous versions, one "creates disorder” in order to select the suitable beams and recycle the others, but which differs from the previous versions in particular in that the source which produces the light is outside the enclosure.
  • the projector 20 successively comprises a source 6a producing light, a condenser 21, a first network RL1 of input lenses, a diffusing enclosure 7a, a second network RL2 of output lenses, a field lens 22, a liquid crystal screen 2 which constitute the object to be projected, and a projection objective 3; all these elements being arranged on an optical axis 10.
  • the light produced by the source 6a is captured by the condenser 21 which forms a beam 23 thereof having parallel rays.
  • the beam 23 passes through the first network RL1 comprising n input lenses LEl to LEn.
  • LE1 to LEn generates an image of the source 6a in the plane of an inlet wall 25 of the enclosure.
  • the wall 25 fulfills a diaphragm function: it comprises a number n of inlet ports Ol to On (of circular section for example) each corresponding to a lens LE1 to LEn, and each of these lenses forms the image of the source 6a in the corresponding input port Ol to On. It is important for the efficiency of the enclosure 7a that the sum of the surfaces of the inlet orifices Ol to On represents a small part of the surface of the diaphragm that constitutes the wall 25.
  • the second wall 26 of the enclosure 7a, opposite the first wall 25, has outlet openings OSl to OSn whose shape is the same as that of the object to be projected, that is to say similar to the shape the liquid crystal display; in 16/9 format for example.
  • the light introduced into the enclosure 7a undergoes for the most part multiple diffusions on the interior diffusing faces 25a, 26a of the walls 25, 26, and it emerges through the outlet openings OS1 and OSn, in the form of as many microbeams FI to Fn.
  • the area of an inlet opening is much smaller than that of an outlet opening , of the order of three times for example.
  • Each output opening OS1 to OSn forms a light source which exhibits good luminance homogeneity. Uniformity is all the better as the area occupied by all of the outlet openings OS1 to OSn is small compared to the area of the second wall 26. The portion of area occupied by these outlet openings results from a compromise between good efficiency (little light absorption by the enclosure 7a) and good homogeneity of the beams FI to Fn.
  • favorable proportions of the sum of the areas of the openings OS1 to OSn relative to the area of the second wall 26 are of the order of 10 to 30%.
  • Each microbeam FI to Fn then passes through a corresponding output lens LSI to LSn of the second network RL2.
  • the output lenses LSI to LS2 have the function of forming the image of the output opening OS1 to OSn to which they correspond, on the object to be projected or liquid crystal screen 2, by means of the field lens 22.
  • each output opening OS1 to OSn are added to illuminate each point of the liquid crystal screen, with an overall homogeneity which is comparable to that presented by an output opening.
  • the light modulated by the liquid crystal screen 2 constitutes a useful beam FU, which is then picked up by the projection lens 3 in a conventional manner in order to project the image on a screen (not shown). of the liquid crystal screen 2.
  • the efficiency can be further improved by closing the outlet openings OS1 to OSn by an interference filter or a system of interference filters 16.

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

Abstract

The invention relates to an image projector providing homogeneous lighting of an object to be projected while increasing the light collection efficiency. The projector (1) is comprised of a light source (6) producing a light intended to illuminate an object (2) having a given shape. According to the invention, the projector (1) is further comprised of a housing (7), wherein the light is subjected to multiple diffusions before emerging through an outlet window (9) to illuminate the object (2), and, additionally the shape of the outlet opening (9) is the same as that of the object to be projected. The invention is applicable particularly to television projectors using a liquid crystal screen.

Description

SOURCE LUMINEUSE DE PROJECTEUR D'IMAGES LIGHT SOURCE OF IMAGE PROJECTOR
L'invention concerne un projecteur d'images, et plus particulièrement une source lumineuse destinée à être utilisée notamment dans les projecteurs de télévision utilisant un écran à cristaux liquides . Le diagramme de rayonnement d'une source de lumière s'adapte mal, le plus souvent, à réaliser l'éclairement homogène d'un objet à projeter, sans perdre une part considérable de la lumière produite par la source.The invention relates to an image projector, and more particularly a light source intended for use in particular in television projectors using a liquid crystal screen. The radiation pattern of a light source is most often ill-suited to achieve homogeneous illumination of an object to be projected, without losing a considerable part of the light produced by the source.
Généralement, le diagramme de rayonnement d'une source de lumière montre une luminance non homogène en champ proche, et une émission directionnelle (champ lointain) plus homogène. C'est généralement l'émission directionnelle que l'on fait correspondre à l'objet à projeter, à l'aide notamment de systèmes dioptriques ou de miroirs paraboliques. L'utilisation d'un système dioptrique ou d'un miroir parabolique conduit à une forte limitation de l'efficacité de collection de la lumière. Dans le premier cas, cette limitation est liée à l'effet de vignetage : pour 30 % de perte de luminance sur les bords, l'efficacité est de l'ordre de 50 % ; et dans le second cas, on peut collecter facilement seulement 50 % du flux par suite de limitations pratiques dans la taille du miroir.Generally, the radiation diagram of a light source shows a non-homogeneous luminance in the near field, and a directional emission (far field) more homogeneous. It is generally the directional emission that is made to correspond to the object to be projected, using in particular dioptric systems or parabolic mirrors. The use of a dioptric system or a parabolic mirror leads to a strong limitation of the efficiency of light collection. In the first case, this limitation is linked to the vignetting effect: for 30% loss of luminance at the edges, the efficiency is around 50%; and in the second case, only 50% of the flux can be easily collected due to practical limitations in the size of the mirror.
A cette perte, il faut ajouter la perte engendrée par le facteur de forme de l'objet à projeter, forme qui, en télévision notamment est un rectangle et non un disque : ainsi par exemple, les nouveaux formats 16 x 9 entraînent sur un champ- à symétrie circulaire une perte supplémentaire égale à 70 % environ.To this loss, we must add the loss caused by the form factor of the object to be projected, a form which, in television in particular is a rectangle and not a disc: thus for example, the new 16 x 9 formats entail on a field - with circular symmetry an additional loss equal to approximately 70%.
La présente invention a pour but de remédier aux inconvénients ci-dessus mentionnés. Elle concerne un projecteur d'images et particulièrement une source lumineuse dont l'agencement nouveau permet d'obtenir un éclairement homogène d'un objet à projeter tout en améliorant l'efficacité de collection de la lumière.The object of the present invention is to remedy the drawbacks mentioned above. It relates to an image projector and particularly a light source of which the new arrangement makes it possible to obtain a uniform illumination of an object to be projected while improving the efficiency of light collection.
L'invention peut être mise en oeuvre à l'aide de pratiquement tous les types de lumière et de tous moyens pour la produire, et elle trouve une application particulièrement intéressante dans les projecteurs de télévision utilisant un écran à cristaux liquides.The invention can be implemented using practically all types of light and all means for producing it, and it finds a particularly advantageous application in television projectors using a liquid crystal screen.
Selon l'invention, un projecteur d'images comportant au moins une source de lumière, la source produisant une lumière destinée à éclairer un objet ayant une forme donnée, est caractérisé en ce qu'il comporte en outre une enceinte ayant des parois intérieures diffusantes et peu absorbantes par lesquelles la lumière est diffusée avant de sortir de l'enceinte par au moins une ouverture de sortie, et en ce que la forme de l'ouverture de sortie est sensiblement la même que la forme de l'objet.According to the invention, an image projector comprising at least one light source, the source producing light intended to illuminate an object having a given shape, is characterized in that it also comprises an enclosure having diffusing internal walls and not very absorbent by which the light is diffused before leaving the enclosure by at least one exit opening, and in that the shape of the exit opening is substantially the same as the shape of the object.
Dans ces conditions, si les parois de l'enceinte sont diffusantes et blanches, les multiples diffusions de la lumière dans cette enceinte qui constitue une enceinte intégratrice, permettent d'obtenir au travers de l'ouverture de sortie une luminance d'une très grande homogénéité. La source de lumière peut être contenue dans l'enceinte, et la luminance au travers de l'ouverture de sortie sera d'autant plus homogène que l'angle sous lequel on voit la source est faible, et l'efficacité de collection de lumière sera d'autant meilleure que la forme de l'ouverture de sortie sera proche de celle de l'objet.Under these conditions, if the walls of the enclosure are diffusing and white, the multiple diffusions of light in this enclosure which constitutes an integrating enclosure, make it possible to obtain through the outlet opening a luminance of very great homogeneity. The light source can be contained in the enclosure, and the luminance through the outlet opening will be all the more homogeneous the lower the angle at which the source is seen, and the efficiency of light collection will be all the better as the shape of the outlet opening is close to that of the object.
L'invention sera mieux comprise à l'aide de la description qui suit, faite à titre d'exemple non limitatif, en référence aux figures annexées parmi lesquelles :The invention will be better understood with the aid of the description which follows, given by way of nonlimiting example, with reference to the appended figures among which:
- la figure 1 montre de manière schématique un projecteur d'image conforme à l'invention, le projecteur étant d'un type dans lequel l'objet à projeter est un écran à cristaux liquides, - la figure 2 montre de manière schématique une version du projecteur de l'invention dans laquelle l'objet à projeter est pratiquement en contact avec une ouverture d'une enceinte montrée à la figure 1, - la figure 3 montre schématiquement une version de l'invention dans laquelle une source de lumière montrée à la figure 1 est située à l'extérieur de l'enceinte .FIG. 1 schematically shows an image projector according to the invention, the projector being of a type in which the object to be projected is a liquid crystal screen, - Figure 2 shows schematically a version of the projector of the invention in which the object to be projected is practically in contact with an opening of an enclosure shown in Figure 1, - Figure 3 shows schematically a version of l invention in which a light source shown in Figure 1 is located outside the enclosure.
La figure 1 montre à titre d'exemple non limitatif un projecteur d'images 1 suivant l'invention, dont l'objet à projeter est un écran à cristaux liquides 2. L'écran à cristaux liquides de façon classique définit une image, une image de télévision par exemple qui est projetée sur un écran (non représenté) à l'aide d'un objectif de projection 3. L'écran à cristaux liquides 2 module la lumière fournie par un dispositif émetteur 5 de lumière comportant une source de lumière 6.FIG. 1 shows by way of nonlimiting example an image projector 1 according to the invention, the object of which to be projected is a liquid crystal screen 2. The liquid crystal screen conventionally defines an image, a television image for example which is projected onto a screen (not shown) using a projection lens 3. The liquid crystal screen 2 modulates the light supplied by a light emitting device 5 comprising a light source 6.
Selon une caractéristique de l'invention, le dispositif émetteur 5 comprend en outre une enceinte 7 dont les parois intérieures 8 sont diffusantes et peu absorbantes .According to a characteristic of the invention, the emitting device 5 further comprises an enclosure 7 whose internal walls 8 are diffusing and not very absorbent.
Dans la version de l'invention montrée à la figure 1, la lumière produite par la source 6 est introduite dans l'enceinte 7 par le fait que la source 6 est contenue dans l'enceinte 7.In the version of the invention shown in FIG. 1, the light produced by the source 6 is introduced into the enclosure 7 by the fact that the source 6 is contained in the enclosure 7.
Selon une caractéristique importante de l'invention, l'enceinte 7 comporte une ouverture 9 de sortie, destinée au passage de la lumière produite par la source 6, la forme de l'ouverture de sortie 9 étant sensiblement la même que celle de l'objet à projeter, c'est-à-dire la même que celle de l'écran à cristaux liquides 2.According to an important characteristic of the invention, the enclosure 7 has an outlet opening 9, intended for the passage of light produced by the source 6, the shape of the outlet opening 9 being substantially the same as that of the object to be projected, i.e. the same as that of the liquid crystal screen 2.
Dans l'exemple non limitatif montré à la figure 1, l'enceinte 7 a une forme ovoïde, cependant cette forme peut être différente ; mais de préférence les parois intérieures 8 doivent s'étendre sans trop de modifications brutales de leur direction, afin de ne pas multiplier inutilement les réflexions dans l'enceinte 7 et limiter l'absorption de la lumière avant que cette dernière n 'émerge par l'ouverture de sortie 9. Dans l'exemple de la figure 1, l'enceinte 7 est représentée par une vue en coupe suivant sa plus grande dimension Dl, et elle est centrée sur un axe optique 10. L'ouverture 9 de sortie est également centrée sur l'axe optique 10, de même que l'objectif de projection 3, l'écran à cristaux liquides 2, un condenseur 11 (disposé entre l'écran 2 et l'émetteur 5) et une lentille de champ 12 interposée entre le condenseur 11 et l'écran à cristaux liquides 2.In the nonlimiting example shown in FIG. 1, the enclosure 7 has an ovoid shape, however this shape may be different; but preferably the interior walls 8 must extend without too many sudden changes in their direction, so as not to unnecessarily multiply the reflections in the enclosure 7 and limit the absorption of light before the latter emerges through the outlet opening 9. In the example of FIG. 1, the enclosure 7 is represented by a sectional view along its largest dimension D1, and it is centered on an optical axis 10. The outlet opening 9 is also centered on the axis optics 10, as well as the projection objective 3, the liquid crystal screen 2, a condenser 11 (disposed between the screen 2 and the emitter 5) and a field lens 12 interposed between the condenser 11 and the liquid crystal display 2.
Comme il a été précédemment mentionné, l'ouverture 9 de sortie a une forme semblable à celle de l'écran à cristaux liquides 2 de façon à adapter l'homogénéité en luminance à l'objet à projeter, et augmenter ainsi de manière significative l'efficacité globale du projecteur 1.As previously mentioned, the outlet opening 9 has a shape similar to that of the liquid crystal screen 2 so as to adapt the luminance homogeneity to the object to be projected, and thus significantly increase the overall efficiency of the projector 1.
Par exemple, en supposant que l'écran à cristaux liquides 2 soit un rectangle avec une longueur (non représentée) perpendiculaire au plan de la figure 1, et une largeur 11 telles que l'écran à cristaux liquides 2 est au format allongé 16/9, l'ouverture de sortie 9 comporte une hauteur h parallèle à la largeur 11 de l'écran à cristaux liquides 2 et une longueur (perpendiculairement au plan de la figure 1) telles que le rapport de cette dernière longueur à cette hauteur h correspond sensiblement au format 16/9.For example, supposing that the liquid crystal screen 2 is a rectangle with a length (not shown) perpendicular to the plane of FIG. 1, and a width 11 such that the liquid crystal screen 2 is in elongated format 16 / 9, the outlet opening 9 has a height h parallel to the width 11 of the liquid crystal screen 2 and a length (perpendicular to the plane of Figure 1) such that the ratio of the latter length to this height h corresponds roughly in 16: 9 format.
La source de lumière 6 est d'un type classique. Elle produit une lumière qui peut aussi bien être cohérente que non cohérente, ainsi que monochromatique ou dans tout le spectre du visible .The light source 6 is of a conventional type. It produces light that can be both coherent and non-coherent, as well as monochromatic or across the whole visible spectrum.
La source de lumière 6 est montée dans l'enceinte 7 et alimentée par des moyens en eux-mêmes classiques, non représentés . La source 6 est disposée dans l'enceinte de façon qu'elle soit vue sous un angle faible (depuis le condenseur 11) et de préférence en dehors de l'axe optique 10, de manière que la plupart des rayons de lumière r soient diffusés dans l'enceinte 7 avant d'en sortir par l'ouverture 9, comme illustré sur la figure 1. L'enceinte 7 n'ayant pas des parois parfaitement blanches et étant ouverte sur un espace noir par l'ouverture 9, on peut exprimer une luminance moyenne L de l'enceinte 7 en fonction des surfaces relatives de la source Ss, de l'enceinte Se et de l'ouverture So :The light source 6 is mounted in the enclosure 7 and supplied by means in themselves conventional, not shown. The source 6 is arranged in the enclosure so that it is seen at a low angle (from the condenser 11) and preferably outside the optical axis 10, so that most of the rays of light r are scattered in enclosure 7 before leaving it through opening 9, as illustrated in FIG. 1. The enclosure 7 does not have perfectly white walls and being open onto a black space through the opening 9, an average luminance L of the enclosure 7 can be expressed as a function of the relative surfaces of the source Ss, of the enclosure Se and opening So:
τ _ Ln. Ss . (l-Rs) τ _ Ln. Ss. (l-Rs)
Ss . (l-Rs) + Se . (l-Re) + So où Ln est la luminance du corps noir dont la température est celle de la source ; où 1-R correspond à l'absorption de chaque surface, Rs étant la réflectivité de la surface de la source, Re étant la réflectivité de la surface de l'enceinte .Ss. (l-Rs) + Se. (l-Re) + So where Ln is the luminance of the black body whose temperature is that of the source; where 1-R corresponds to the absorption of each surface, Rs being the reflectivity of the surface of the source, Re being the reflectivity of the surface of the enclosure.
La luminance au travers de l'ouverture 9 se caractérise par une très grande homogénéité si l'angle sous lequel on voit la source est faible . C'est cette propriété que l'on utilise pour obtenir un éclairement uniforme de l'objet à projeter, à savoir l'écran à cristaux liquides 2 dans l'exemple . L'efficacité de l'enceinte est définie par le rapport So/Se . (l-Re) + So. L'absorption 1-Re de la surface de l'enceinte peut être aussi petite que 1 % , aussi l'efficacité de l'enceinte peut être très élevée même si pour obtenir une bonne luminance, la surface So de l'ouverture 9 ne peut être grande devant celle de la source et si, pour obtenir une bonne homogénéité de luminance, la surface Se de l'enceinte 7 doit être grande devant celle de la source 6.The luminance through the opening 9 is characterized by very high homogeneity if the angle under which the source is seen is small. It is this property that is used to obtain uniform illumination of the object to be projected, namely the liquid crystal screen 2 in the example. The efficiency of the enclosure is defined by the So / Se ratio. (l-Re) + So. The absorption 1-Re of the surface of the enclosure can be as small as 1%, also the efficiency of the enclosure can be very high even if to obtain good luminance, the surface So of the opening 9 does not may be large in front of that of the source and if, to obtain good homogeneity of luminance, the area Se of the enclosure 7 must be large in front of that of the source 6.
Des essais ont montré que des résultats très intéressants était déjà obtenus avec une surface So de l'ouverture 9 égale seulement à trois fois la surface S s de la source .Tests have shown that very interesting results were already obtained with a surface So of the opening 9 equal to only three times the surface S s of the source.
La lumière qui émerge par l'ouverture 9 est captée au moins en partie par le condenseur 11 et constitue un faisceau 15.The light which emerges through the opening 9 is captured at least in part by the condenser 11 and constitutes a beam 15.
Dans cette configuration, l'ouverture 9 de sortie constitue une source de lumière qui présente une excellente homogénéité de luminance , ce qui permet de former l'image de l'ouverture 9 sur l'écran à cristaux liquides 2 par le condenseur 11 qui est situé à proximité de l'ouverture 9 ; et la lentille de champ 12 forme l'image du condenseur 11 sur la pupille (non représentée) de l'objectif de projection 3. Ainsi c'est la plus grande partie de la lumière délivrée par l'ouverture 9 qui est utilisée, alors que dans l'art antérieur, on ne peut utiliser qu'une fraction de la lumière qui forme le champ lointain.In this configuration, the outlet opening 9 constitutes a light source which has excellent luminance homogeneity, which makes it possible to form the image of the opening 9 on the liquid crystal screen 2 by the condenser 11 which is located near the opening 9; and the field lens 12 forms the image of the condenser 11 on the pupil (not shown) of the projection objective 3. Thus it is most of the light delivered by the aperture 9 which is used, then that in the prior art, only a fraction of the light which forms the far field can be used.
L'efficacité globale peut encore être améliorée en interposant un système de filtre interférentiel renvoyant tous les rayons qui émergent de l'enceinte au-delà d'une certaine incidence . Comme montré sur la figure 1, un filtre interférentiel 16 (représenté en traits pointillés) ou un système de filtres interférentiels peut être appliqué contre l'ouverture de sortie 9, le plan du filtre interférentiel étant normal à l'axe optique 10. Dans ces conditions, l'effet du filtre interférentiel 16 est de conférer à l'ouverture 9 de sortie un diagramme d'émission fortement concentré sur l'axe optique 10. De tels filtres interférentiels sont en eux-mêmes bien connus . Ils sont réalisés par superposition de couches minces d'indices alternativement faibles et forts . Le calcul précis de l'épaisseur des couches successives fait partie de l'art connu en matière de traitement optique, et ce calcul prend en compte la longueur d'onde du rayonnement. Cependant pour une lumière non monochromatique, un système de filtres interférentiels 16 peut comporter le long de l'axe optique 10, successivement plusieurs filtres interférentiels agissant chacun pour une longueur d'onde donnée. La figure 2 illustre une forme de réalisation, autorisée par la présence d'un système 16 de filtres interférentiels, et qui est intéressante en ce qu'elle permet de placer pratiquement en contact direct la source de lumière que constitue l'ouverture 9, avec l'objet à projeter c'est-à-dire l'écran à cristaux liquides 2 ; l'ouverture 9 pouvant ainsi comporter pratiquement les mêmes dimensions que l'écran à cristaux liquides 2.The overall efficiency can be further improved by interposing an interference filter system returning all the rays that emerge from the enclosure beyond a certain incidence. As shown in FIG. 1, an interference filter 16 (shown in dotted lines) or a system of interference filters can be applied against the outlet opening 9, the plane of the interference filter being normal to the optical axis 10. In these conditions, the effect of the interference filter 16 is to give the outlet opening 9 an emission diagram highly concentrated on the optical axis 10. Such interference filters are in themselves well known. They are produced by superposition of thin layers of alternately weak and strong indices. The precise calculation of the thickness of the successive layers is part of the known art in optical processing, and this calculation takes into account the wavelength of the radiation. However, for non-monochromatic light, a system of interference filters 16 can comprise, along the optical axis 10, successively several interference filters each acting for a given wavelength. FIG. 2 illustrates an embodiment, authorized by the presence of a system 16 of interference filters, and which is advantageous in that it makes it possible to place the light source constituted by the opening 9 practically in direct contact, with the object to be projected, that is to say the liquid crystal screen 2; opening 9 thus being able to have practically the same dimensions as the liquid crystal screen 2.
Dans l'exemple non limitatif montré à la figure 2, l'ouverture 9, l'écran à cristaux liquides 2 et l'objectif de projection 3 sont alignés et centrés sur l'axe de projectionIn the nonlimiting example shown in FIG. 2, the opening 9, the liquid crystal screen 2 and the projection lens 3 are aligned and centered on the projection axis
10 ; la source 6 est contenue dans l'enceinte 7, et l'ouverture de sortie 9 de cette dernière a sensiblement les dimensions de l'écran à cristaux liquides 2. L'ouverture de sortie 9 est obturée par le système de filtre interférentiel 16 ; et entre ce dernier et l'écran à cristaux liquides 2, est interposée une lentille de champ 17 qui assure la convergence de tous les rayons sur la pupille de l'objectif de projection 3, pupille dont le plan 18 est symbolisé en traits pointillés sur la figure 2. Dans les exemples montrés aux figures 1 et 2, l'enceinte diffusante ou enceinte intégratrice telle que l'enceinte 6 permet de remodeler la distribution de luminance : en pratiquant dans l'enceinte une ouverture de sortie ayant la taille et/ou la forme de l'objet à projeter, et l'enceinte constituant une enceinte intégratrice qui contient la source produisant la lumière, on dérègle l'organisation habituelle des directions de rayonnement, on "crée le désordre" et l'on sélectionne les faisceaux convenables en recyclant les autres .10; the source 6 is contained in the enclosure 7, and the outlet opening 9 of the latter has substantially the dimensions of the liquid crystal screen 2. The outlet opening 9 is closed by the interference filter system 16; and between the latter and the liquid crystal screen 2, a field lens 17 is interposed which ensures the convergence of all the rays on the pupil of the projection objective 3, pupil whose plane 18 is symbolized in dotted lines on FIG. 2. In the examples shown in FIGS. 1 and 2, the diffusing enclosure or integrating enclosure such as enclosure 6 makes it possible to reshape the distribution of luminance: by making in the enclosure an outlet opening having the size and / or the shape of the object to be projected, and the enclosure constituting an integrating enclosure which contains the light producing source, the usual organization of the radiation directions is disrupted, "disorder is created" and the beams are selected suitable by recycling others.
Il est à noter que les modes de réalisation montrés aux figures 1 et 2 peuvent poser dans certains cas des problèmes de réalisation, liés notamment à la présence d'un élément chaud dans l'enceinte 6.It should be noted that the embodiments shown in FIGS. 1 and 2 can in certain cases pose implementation problems, linked in particular to the presence of a hot element in the enclosure 6.
La figure 3 illustre une nouvelle version de l'invention dans laquelle, comme dans les versions précédentes, on "crée le désordre" afin de sélectionner les faisceaux convenables et recycler les autres, mais qui diffère des versions précédentes notamment en ce que la source qui produit la lumière est à l'extérieur de l'enceinte.FIG. 3 illustrates a new version of the invention in which, as in the previous versions, one "creates disorder" in order to select the suitable beams and recycle the others, but which differs from the previous versions in particular in that the source which produces the light is outside the enclosure.
Dans l'exemple non limitatif représenté à la figure 3, le projecteur 20 comporte, successivement une source 6a produisant de la lumière, un condenseur 21, un premier réseau RL1 de lentilles d'entrée, une enceinte diffusante 7a, un second réseau RL2 de lentilles de sortie, une lentille de champ 22, un écran à cristaux liquides 2 qui constituent l'objet à projeter, et un objectif de projection 3 ; tous ces éléments étant disposés sur un axe optique 10.In the nonlimiting example shown in FIG. 3, the projector 20 successively comprises a source 6a producing light, a condenser 21, a first network RL1 of input lenses, a diffusing enclosure 7a, a second network RL2 of output lenses, a field lens 22, a liquid crystal screen 2 which constitute the object to be projected, and a projection objective 3; all these elements being arranged on an optical axis 10.
La lumière produite par la source 6a est captée par le condenseur 21 qui en forme un faisceau 23 ayant des rayons parallèles . Le faisceau 23 traverse le premier réseau RL1 comportant n lentilles d'entrée LEl à LEn. Chaque lentilleThe light produced by the source 6a is captured by the condenser 21 which forms a beam 23 thereof having parallel rays. The beam 23 passes through the first network RL1 comprising n input lenses LEl to LEn. Each lens
LEl à LEn génère une image de la source 6a dans le plan d'une paroi d'entrée 25 de l'enceinte.LE1 to LEn generates an image of the source 6a in the plane of an inlet wall 25 of the enclosure.
La paroi 25 remplit une fonction de diaphragme : elle comporte un nombre n d'orifices d'entrée Ol à On (de section circulaire par exemple) correspondant chacun à une lentille LEl à LEn, et chacune de ces lentilles forme l'image de la source 6a dans l'orifice Ol à On d'entrée correspondant. Il est important pour l'efficacité de l'enceinte 7a que la somme des surfaces des orifices d'entrée Ol à On représente une partie faible de la surface du diaphragme que constitue la paroi 25.The wall 25 fulfills a diaphragm function: it comprises a number n of inlet ports Ol to On (of circular section for example) each corresponding to a lens LE1 to LEn, and each of these lenses forms the image of the source 6a in the corresponding input port Ol to On. It is important for the efficiency of the enclosure 7a that the sum of the surfaces of the inlet orifices Ol to On represents a small part of the surface of the diaphragm that constitutes the wall 25.
La seconde paroi 26 de l'enceinte 7a, opposée à la première paroi 25, comporte des ouvertures de sorties OSl à OSn dont la forme est la même que celle de l'objet à projeter c'est-à-dire semblable à la forme de l'écran à cristaux liquides ; au format 16/9 par exemple .The second wall 26 of the enclosure 7a, opposite the first wall 25, has outlet openings OSl to OSn whose shape is the same as that of the object to be projected, that is to say similar to the shape the liquid crystal display; in 16/9 format for example.
La lumière introduite dans l'enceinte 7a subit pour sa plus grande part de multiples diffusions sur les faces intérieures diffusantes 25a, 26a des parois 25, 26, et elle émerge par les ouvertures de sorties OSl et OSn, sous la forme d'autant de microfaisceaux FI à Fn.The light introduced into the enclosure 7a undergoes for the most part multiple diffusions on the interior diffusing faces 25a, 26a of the walls 25, 26, and it emerges through the outlet openings OS1 and OSn, in the form of as many microbeams FI to Fn.
Dans l'exemple non limitatif décrit, où les orifices d'entrée Ol à On et les ouvertures de sortie OSl à OSn sont en même nombre, la surface d'une ouverture d'entrée est largement inférieure à celle d'une ouverture de sortie, de l'ordre de trois fois par exemple. Chaque ouverture de sortie OSl à OSn forme une source lumineuse qui présente une bonne homogénéité de luminance . L'homogénéité est d'autant meilleure que la surface occupée par l'ensemble des ouvertures de sorties OSl à OSn est faible par rapport à la surface de la seconde paroi 26. La part de surface occupée par ces ouvertures de sorties résulte d'un compromis entre une bonne efficacité (peu d'absorption de lumière par l'enceinte 7a) et une bonne homogénéité des faisceaux FI à Fn . A titre d'exemple non limitatif, on peut indiquer que des proportions favorables de la somme des surfaces des ouvertures OSl à OSn par rapport à la surface de la seconde paroi 26 sont de l'ordre de 10 à 30 % .In the nonlimiting example described, where the inlet ports Ol to On and the outlet openings OSl to OSn are the same number, the area of an inlet opening is much smaller than that of an outlet opening , of the order of three times for example. Each output opening OS1 to OSn forms a light source which exhibits good luminance homogeneity. Uniformity is all the better as the area occupied by all of the outlet openings OS1 to OSn is small compared to the area of the second wall 26. The portion of area occupied by these outlet openings results from a compromise between good efficiency (little light absorption by the enclosure 7a) and good homogeneity of the beams FI to Fn. By way of nonlimiting example, it can be indicated that favorable proportions of the sum of the areas of the openings OS1 to OSn relative to the area of the second wall 26 are of the order of 10 to 30%.
Chaque microfaisceau FI à Fn passe ensuite par une lentille de sortie LSI à LSn correspondante du second réseau RL2. Comme illustré par le second micro faisceau F2 au niveau de la seconde lentille de sortie LS2, les lentilles de sorties LSI à LS2 ont pour fonction de former l'image de l'ouverture de sortie OSl à OSn à laquelle elles correspondent, sur l'objet à projeter ou écran à cristaux liquides 2, par l'intermédiaire de la lentille de champ 22.Each microbeam FI to Fn then passes through a corresponding output lens LSI to LSn of the second network RL2. As illustrated by the second micro-beam F2 at the level of the second output lens LS2, the output lenses LSI to LS2 have the function of forming the image of the output opening OS1 to OSn to which they correspond, on the object to be projected or liquid crystal screen 2, by means of the field lens 22.
Ainsi les luminances de chaque ouverture de sortie OSl à OSn s'ajoutent pour éclairer chaque point de l'écran à cristaux liquides, avec une homogénéité globale qui est comparable à celle que présente une ouverture de sortie . La lumière modulée par l'écran à cristaux liquides 2 constitue un faisceau utile FU, qui est ensuite capté par l'objectif de projection 3 de manière en elle-même classique , en vue de projeter sur un écran (non représenté) l'image de l'écran à cristaux liquides 2. H est à noter que, comme pour les exemples précédents, l'efficacité peut encore être améliorée en fermant les ouvertures de sortie OSl à OSn par une filtre interférentiel ou un système de filtres interférentiels 16. Thus the luminances of each output opening OS1 to OSn are added to illuminate each point of the liquid crystal screen, with an overall homogeneity which is comparable to that presented by an output opening. The light modulated by the liquid crystal screen 2 constitutes a useful beam FU, which is then picked up by the projection lens 3 in a conventional manner in order to project the image on a screen (not shown). of the liquid crystal screen 2. It should be noted that, as in the previous examples, the efficiency can be further improved by closing the outlet openings OS1 to OSn by an interference filter or a system of interference filters 16.

Claims

REVENDICATIONS
1 - Projecteur d'images comportant au moins une source de lumière (6, 6a) , la source produisant une lumière destinée à éclairer un objet (2) à projeter ayant une forme donnée, le projecteur comportant en outre une enceinte (7, 7a)1 - Image projector comprising at least one light source (6, 6a), the source producing light intended to illuminate an object (2) to be projected having a given shape, the projector further comprising an enclosure (7, 7a )
5 ayant des parois intérieures (8, 25a, 26a) diffusantes par lesquelles au moins une partie de ladite lumière est diffusée avant d'émerger de l'enceinte (7, 7a) par au moins une ouverture de sortie (9, OSl à OSn) , la forme de l'ouverture de sortie (9, OSl à OSn) étant sensiblement la même que la forme i ϋ de l'objet (2) , caractérisé en ce que l'ouverture de sortie (9) est obturée par un dispositif de filtres interférentiels (16) réfléchissant les rayons dont l'angle d'incidence est supérieur à une valeur prédéterminée. 5 having diffusing interior walls (8, 25a, 26a) through which at least part of said light is diffused before emerging from the enclosure (7, 7a) through at least one outlet opening (9, OSl to OSn ), the shape of the outlet opening (9, OSl to OSn) being substantially the same as the shape i ϋ of the object (2), characterized in that the outlet opening (9) is closed by a interference filter device (16) reflecting rays whose angle of incidence is greater than a predetermined value.
2 - Projecteur selon la revendication 1, caractérisé l-5 en ce que la source de lumière (6) est contenue dans l'enceinte2 - projector according to claim 1, characterized l- 5 in that the light source (6) is contained in the enclosure
(7) .(7).
3 - Projecteur selon la revendication 2, caractérisé en ce que la surface de l'ouverture (9) de sortie est largement supérieure à celle de la source de lumière (6) .3 - Projector according to claim 2, characterized in that the surface of the outlet opening (9) is much greater than that of the light source (6).
20 4 - Projecteur selon l'une des revendications 2 ou 3, caractérisé en ce qu'il comporte des moyens (11) pour former l'image de l'ouverture (9) de sortie sur l'objet (2) à projeter.20 4 - Projector according to one of claims 2 or 3, characterized in that it comprises means (11) for forming the image of the outlet opening (9) on the object (2) to be projected.
5 - Projecteur selon l'une des revendications précédentes, caractérisé en ce que l'ouverture de sortie (9)5 - Projector according to one of the preceding claims, characterized in that the outlet opening (9)
*" comporte sensiblement les mêmes dimensions que celles de l'objet * "has substantially the same dimensions as those of the object
(2) à projeter, ce dernier étant pratiquement "en contact" avec l'ouverture de sortie (9) .(2) to be projected, the latter being practically "in contact" with the outlet opening (9).
6 - Projecteur selon la revendication 1, caractérisé en ce que la source de lumière (6a) est à l'extérieur de6 - Projector according to claim 1, characterized in that the light source (6a) is outside of
30 l'enceinte (7a) et en ce que cette dernière comporte au moins un orifice d'entrée (01 à On) par lequel la lumière est introduite dans l'enceinte (7a) . 7 - Projecteur selon la revendication 6, caractérisé en ce que l'enceinte comporte plusieurs orifices d'entrée (01 à On) .30 the enclosure (7a) and in that the latter comprises at least one inlet orifice (01 to On) through which light is introduced into the enclosure (7a). 7 - Projector according to claim 6, characterized in that the enclosure has several inlet openings (01 to On).
8 - Projecteur selon l'une quelconque des revendications 6 ou 7, caractérisé en ce qu'il comporte des moyens (21, RLl) pour former l'image de la source (6a) sur chaque orifice d'entrée (01 à On) .8 - Projector according to any one of claims 6 or 7, characterized in that it comprises means (21, RLl) for forming the image of the source (6a) on each inlet orifice (01 to On) .
9 - Projecteur selon l'une quelconque des revendications 6, 7 ou 8, caractérisé en ce qu'il comporte plusieurs ouvertures de sorties (OSl à OSn) par lesquels la lumière émerge de l'enceinte sous la forme de micro faisceaux (FI à Fn) .9 - Projector according to any one of claims 6, 7 or 8, characterized in that it comprises several outlet openings (OSl to OSn) through which the light emerges from the enclosure in the form of micro-beams (FI to Fn).
10 - Projecteur selon la revendication 9, caractérisé en ce qu'il comporte un même nombre d'orifices d'entrées (01 à On) et d'ouvertures de sorties (OSl à OSn) .10 - Projector according to claim 9, characterized in that it comprises the same number of inlet openings (01 to On) and outlet openings (OSl to OSn).
11 - Projecteur selon l'une des revendications 9 ou 10, caractérisé en ce que la surface formée par l'ensemble des orifices d'entrées (01 à On) est inférieure à la surface formée par l'ensemble des ouvertures de sortie (OSl à OSn) . 12 - Projecteur selon l'une des revendications 9 ou 10 ou 11, caractérisé en ce que, pour chaque ouverture de sortie (OSl à OSn) , il comporte des moyens (RL2, 21) pour former l'image de l'ouverture de sortie (OSl à OSn) sur l'objet (2) à projeter . 13 - Projecteur selon l'une quelconque des revendications 9 ou 10 ou 11 ou 12, caractérisé en ce que les ouvertures de sortie (OSl à OSn) sont fermées par un dispositif de filtres interférentiels (16) .11 - Projector according to one of claims 9 or 10, characterized in that the surface formed by all of the inlet orifices (01 to On) is less than the surface formed by all of the outlet openings (OSl at OSn). 12 - Projector according to one of claims 9 or 10 or 11, characterized in that, for each outlet opening (OSl to OSn), it comprises means (RL2, 21) for forming the image of the opening of output (OSl to OSn) on the object (2) to be projected. 13 - Projector according to any one of claims 9 or 10 or 11 or 12, characterized in that the outlet openings (OSl to OSn) are closed by a device of interference filters (16).
14 - Projecteur selon l'une des revendications précédentes, caractérisé en ce que l'objet (2) à projeter est un écran à cristaux liquides. 14 - Projector according to one of the preceding claims, characterized in that the object (2) to be projected is a liquid crystal screen.
PCT/FR1991/000351 1990-05-22 1991-04-26 Light source for image projector WO1991018315A1 (en)

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FR9006387A FR2662514A1 (en) 1990-05-22 1990-05-22 LIGHT SOURCE OF IMAGE PROJECTOR.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0631170A2 (en) * 1993-06-24 1994-12-28 International Business Machines Corporation Back-lighting system for transmissive display
EP0631170A3 (en) * 1993-06-24 1995-03-01 Ibm Back-lighting system for transmissive display.
US5526146A (en) * 1993-06-24 1996-06-11 International Business Machines Corporation Back-lighting system for transmissive display
FR2718538A1 (en) * 1994-04-12 1995-10-13 Sextant Avionique Light box for optical valve.
EP0677970A1 (en) * 1994-04-12 1995-10-18 Sextant Avionique Light box for light valve
US5661608A (en) * 1994-04-12 1997-08-26 Sextant Avionique Light box for optical valve
US6024452A (en) * 1997-04-22 2000-02-15 3M Innovative Properties Company Prismatic light beam homogenizer for projection displays

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