WO1998015855A1 - Convertisseur de lumiere blanche en lumiere presentant une polarisation plane - Google Patents

Convertisseur de lumiere blanche en lumiere presentant une polarisation plane Download PDF

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Publication number
WO1998015855A1
WO1998015855A1 PCT/US1997/018038 US9718038W WO9815855A1 WO 1998015855 A1 WO1998015855 A1 WO 1998015855A1 US 9718038 W US9718038 W US 9718038W WO 9815855 A1 WO9815855 A1 WO 9815855A1
Authority
WO
WIPO (PCT)
Prior art keywords
stack
polarization
fact
light
converter according
Prior art date
Application number
PCT/US1997/018038
Other languages
English (en)
Other versions
WO1998015855A9 (fr
Inventor
Brahim Dahmani
Alexander Galpern
Sergey Kuchinsky
Vitaly I. Sukhanov
Original Assignee
Corning Incorporated
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
Priority claimed from FR9612249A external-priority patent/FR2754355B1/fr
Priority claimed from RU96120353/28A external-priority patent/RU96120353A/ru
Application filed by Corning Incorporated filed Critical Corning Incorporated
Publication of WO1998015855A1 publication Critical patent/WO1998015855A1/fr
Publication of WO1998015855A9 publication Critical patent/WO1998015855A9/fr

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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
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining

Definitions

  • the present invention relates to a converter of natural white light into light with planar polarization, and more particularly to such a converter which includes a) a beam source of natural white light, b) a divider of said beam into a reflected beam and a transmitted beam, these two beams each consisting essentially of one of the two components (P, s) with planar polarization of the light beam coming from the source, the two planes of polarization being orthogonal with respect to one another, c) a rotator in order to turn the plane of polarization of one of the beams, coming from the divider, to the plane parallel to the plane of polarization of the other beam, and d) some means for combining the two emerging beams with the same polarization.
  • Such a converter is known from the article entitled "A polarization transforming optics for high luminance LCD projector" by Shikama et al . , pages 64-67 of the transactions of the Congress Eurodisplay 9.', Amsterdam, Holland (September 25-27, 1990) .
  • Such a converter is useful, in particular, for increasing the luminance of the images formed by video image projectors of the type which have a matrix of liquid crystal cells arranged between crossed polarizer and analyzer.
  • the projection beam which passes through this assembly is provided by a source of non- Polarized natural -light.
  • the aforementioned article proposes Converting all of the light coming from the source into light with planar polarization, parallel to the plane of polarization of the polarizer, in front of it.
  • the converter proposed in the article includes a beam - - divider which transmits the polarized component linearly, with the electrical field vector parallel to the plane of incidence (component p) , and which reflects the polarized component linearly, with the electrical field vector perpendicular to the plane of incidence (components), of the beam provided by the source.
  • a half-wave plate causes the plane of polarization of the reflected light (component s) to turn by ⁇ /2, this light is parallel to the plane of polarization of the beam p transmitted by the prism.
  • the latter is combined with the beam which emerges from the half-wave plate, in order to illuminate the polarizer, whose plane of polarization is oriented parallel to that of these two beams.
  • One thus increases the quantity of light transmitted by the input polarizer of", the matrix of liquid crystal cells.
  • the polarizing beam divider used in thv arrangement described above can be produced by the cutting of birefringent crystals or by deposition under vacuum of interferential dielectric layers on the hypotenuse sides, facing one another, of two rectangular prisms, which makes it an expensive optical element, which heavily burdens the price of a video image projector equipped with a light converter incorporating such a prism. Furthermore, by deposition of interferential layers, it is difficult to reach a high level of polarization (ratio of the intensities of the components p and s) .
  • the present invention aims to produce a converter of natural white light into light with planar polarization, which does not have these disadvantages and which can be used in a video image projector intended for the general public, a projector whose cost of production must consequently be as low as possible.
  • the beam divider which equips this converter consists of a stack of parallel plates of two distinct optical media and which alternate with refractive index nj. and n m respectively.
  • the thickness of each of the these plates being much greater than the lengths of coherence of the light coming from the source, the angle of incidence, ⁇ of the beam coming from the source on the second plate of the stack being such that:
  • ⁇ b being the Brewster angle of incidence on said second plate, made up of the optical medium with index n x .
  • the use of such a stack of plates allows one to produce the converter, according to the invention, for a relatively low cost, while giving a very good performance in terms of the level of polarization and conversion yield, particularly, as will be seen further on.
  • the transmitted beam which emerges from the rotator illuminates, according to the same incidence a planar reflector parallel to the plates of the stack of plates, in such a way that the beams reflected by the two stacks combine to form a single beam with planar polarization of the type s.
  • the angle of incidence, ⁇ of the beam on the second plate of the stack is such that ⁇ b ⁇ ⁇ ⁇ ⁇ 2 , in which ⁇ 2 is the angle of incidence of the beam coming from the source on the second plate, for which the intensity of the reflected fraction of the component s of the light is equal to the intensity of the transmitted fraction of the component p. It is thus possible to obtain a high level of reflection of the component s from the light of the source, on the stack of plates, while advantageously minimizing the number of these plates, as will appear subsequently.
  • FIG. 1 is a diagram of one embodiment of the converter according to the invention.
  • FIG. 2 is a graph and Figure 3 is a diagram which explain the functioning of the stack of plates incorporated in the converter of Figure 1
  • - Figure 4 is a diagram of another embodiment of the converter according to the invention.
  • the converter according to the invention has source 1 of natural white light, that is to say not polarized, which is collimated by lens 2 in order to illuminate an extensive surface area of stack 3 of plates which will be described in more detail in connection with Figures 2 and 3, and which constitutes a polarizing beam divider.
  • the stack of plates 3 reflect a part of the light received to mirror 4 and transmit the other part of this light, through polarization rotator 6, to another stack of plates 5, parallel to stack 3 and functioning in the same way.
  • this stack 5 reflects a part of the light to mirror 7 and transmits another part of it, preferably to an optical medium (not represented) which absorbs the transmitted light.
  • the light reflected by mirrors 4 and 7 illuminates matrix 8 of liquid crystal cells functioning as light valves. These cells are controlled individually so that each ensures the formation of an element (or pixel) of a visible image projected using an objective (not represented) on a screen (not represented) arranged to the right of matrix 8, from the point of view of Figure 1.
  • the converter of this invention illuminates matrix 8 with a beam of light with planar polarization, polarizing element 9 called analyzer being conventionally attached to matrix 8 on the side which is opposite to that illuminated by the light coming from source 1.
  • analyzer 9 whose axis of polarization is oriented at 90° with respect to the plane of polarization of the incident light, extinguishes or allows the light to pass through each of the liquid crystal cells of matrix 8, according to the state of electrical excitation of these cells, in such a way that an image is displayed on the projection screen.
  • the axis of polarization of the analyzer could be parallel to that of the light coming from the converter.
  • each cell is designed to allow the light to pass in the absence of excitation and to block che light in the presence of excitation.
  • stack 3 and, in the embodiment of Figure 1, stack 5 consist of plates with parallel surfaces 10!, 10 2 , 10 3 , etc... of an optical medium with refractive index n l7 two successive plates 10 ⁇ , 10 i+i being separated by a plate with parallel surfaces such as Hi, I 2 H3, etc... of a second optical medium with index rim, the thickness of each of these plates being much greater than the wavelength of the visible light used, which prevents any stray interferential effect.
  • plates 10 ⁇ can be made of glass
  • plates Hi are plates of air
  • the angle ⁇ mentioned in the present description is that of the index of the beam illuminating any one of plates IO2-IO4, beginning with the second 10 2 and not that of the incidence of the beam on the first plate 10 ⁇ as represented in the drawing in which, for the sake of clarity of the figures, all plates are considered to be immersed in the same medium.
  • R. ⁇ ⁇ + ⁇ 2N- ⁇ )r s in which N is the number of glass plates 10 (i from 1-N) , this coefficient R s tending towards 1 when N increases.
  • ⁇ ⁇ b so that only the light of component s is reflected by stack 3 to mirror .
  • the transmitted light is then essentially made up of component p and of a small part, not reflected by stack 3, of component s.
  • Polarization rotator- 6, consisting, for example, of a half-wave plate causes the plane of polarization of component p to turn by 90° and then take on type s.
  • the small fraction of component s transmitted by stack 3 takes on the type p.
  • Stack of plates 5, of the same type as stack 3, practically entirely reflects the light of type s which it receives to mirror 7.
  • Mirrors 4 and 7 then both send back light only of type s on matrix 8 of liquid crystal cells.
  • the small residue of light of type p which arrives at stack 5 is transmitted by this stack to an absorbent medium (not represented), for example. This quantity of absorbed light being small, one sees that the yield of the conversion carried out by the converter of this invention is high.
  • the graph of Figure 5 illustrates the variations of the overall reflection coefficient R s as a function of the number N of glass plates (in this case of a glass/air stack) and as a function of the refractive index of. the glass of the plates.
  • the invention makes it possible to produce a converter of natural light into light with planar polarization with a high conversion yield, for a price compatible with an application intended for the general public such as the projection of video images, which would not be the case of a converter equipped with a beam divider made by cutting birefringent crystals, which are very costly, or by deposition under vacuum of stacked interferential dielectric layers.
  • the latter technique is made expensive by the fact that the thickness of the layers formed must be completely adjusted to a low value on extensive surfaces, a restriction which does not burden the plates of the converter of this invention.
  • the converter of Figure 1 must then be modified as represented in Figure 4, in which references identical to the references used in
  • Figure 1 mark identical or similar elements.
  • stack 5 is replaced by a simple single mirror 5' and that polarizing filter 12 is installed in front of liquid crystal matrix 8, the plane of polarization of this filter being oriented at 90° with respect to that of filter 9 in order to absorb component p of the light which is reflected by stack 3 and possibly by mirror 5'.
  • the light yield of the converter remains high, nevertheless, because polarizing filter 12, which only has to -absorb a component p of low intensity, can be produced in such a way as not to considerably reduce the illumination of matrix 8.
  • mirror 5' can be arranged parallel 5 to stack 3.
  • the planes of stack 3 and of mirrors 4, 5, 5' and 7 will advantageously be perpendicular to the plane of Figures 1 and 4 in order not to disturb the polarization of the light beams which are combined coming out of the converter.
  • the graph of Figure 6 illustrates the influence of an angular divergence a of the light beam coming from source 1 which illuminates stack 3 in the vicinity of the Brewster incidence, for three wavelengths R, V, B chosen in the red, green and blue respectively.
  • This divergence can result from the fact that the light beam coming from source 1 (not a point source) cannot be parallel.
  • the graph represents the variations of the overall reflection coefficient R p of the component p which interferes [unconfirmed translation] with the reflection, essentially of component s, on stack 3.
  • Figure 7 represents the variations of R p in the visible domain ( ⁇ from 0.4-0.8 mm) for three values of ⁇ : ⁇ x , ⁇ 2 , ⁇ 3 respectively, which minimize R p to 0.4 mm, 0.5 mm and 0.8 mm, respectively.
  • the graph of Figure 8 represents the variations of the level of polarization of the beam leaving the converter according to the invention, as a function of a difference ⁇ p of the real angle of incidence of the beam illuminating stack 3 with respect to the theoretical
  • Brewster angle ⁇ b The theoretical variation is represented by a solid line, the variation taken from experimental measurements is represented by a broken line.
  • ⁇ b ⁇ 0.5°
  • the experimental measurements report a level of polarization higher than 800, with a theoretical level higher that 1,000, which is very satisfactory. Such a level is difficult, if not impossible, to reach with a beam divider with a stack of interferential layers.
  • polarization rotators can be use to constitute rotator 6 of the converter according to the invention, for example, a half-wave plate made of mica, a film of birefringent polymer such as a drawn polyvinyl alcohol film, a liquid crystal cell or else a plate made of an optically active material as described in the work entitled "Optical Waves in Crystal", authors: A. Yariv, P. Yeh, New York, Wiley International Publication, 1984.
  • a plate made of a birefringent porous glass such as one of those described in the work entitled “Phase separation in glass” prepared by O.V. Mazurin and E.A. Porai-Koshits, published in 1984 by North-Holland (Amsterdam-Oxford-New York-Tokyo) .
  • Rotator 6 could also consist of a 90° image rotator such as that described -in
  • the polarizing beam divider can take on forms other than that of a stack of glass plates separated by air; it can also be enclosed between two glass prisms in order to facilitate its operations and the adjustment of its orientation.
  • the stack could also have only one plate, made of glass, for example, a glass with a high refractive index.
  • a pair of prisms made of glass with a high refractive index they hypotenuse faces being arranged facing one another, while remaining separated by a thin plate of air.
  • the invention is not limited to a converter in which one brings about the turning of the plane of polarization of component p of the light, transmitted by stack 3. It would still be in the scope of the invention to bring about the turning of the plane of polarization of the component s reflected by stack 3, in order to re-align the planes of polarization of the two beams formed by this stack. It would also be in the scope of the invention to eliminate mirrors 4 and 7.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Polarising Elements (AREA)

Abstract

L'invention concerne un convertisseur de lumière blanche en lumière à polarisation plane. Ce convertisseur comprend un séparateur (3) de la lumière blanche en deux faisceaux de polarisation mutuellement orthogonaux. Chaque faisceau comprend essentiellement une lumière polarisée plane de polarisation-p ou de polarisation-s. Ce convertisseur comporte également un rotateur (6) pour assurer la rotation du plan de polarisation de l'un des deux faisceaux, et des moyens (4, 5, 7) pour combiner les deux faisceaux sortant avec la même polarisation. Selon l'invention, le séparateur (3) se compose d'une pile de plaques parallèles alternées de deux supports optiques différents avec des indices de réfraction différents. L'angle d'incidence du faisceau provenant de la source de lumière blanche naturelle (1) est supérieur ou égal à l'angle de Brewster, déterminé par les indices de réfraction des deux supports optiques. L'invention peut être appliquée dans l'industrie comme source de lumière polarisée dans des projecteurs d'images vidéo.
PCT/US1997/018038 1996-10-08 1997-10-03 Convertisseur de lumiere blanche en lumiere presentant une polarisation plane WO1998015855A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR9612249A FR2754355B1 (fr) 1996-10-08 1996-10-08 Convertisseur de lumiere blanche naturelle en lumiere a polarisation plane
FR96/12249 1996-10-08
RU96120353 1996-10-08
RU96120353/28A RU96120353A (ru) 1996-10-08 Преобразователь естественного белого света в плоскополяризованный свет

Publications (2)

Publication Number Publication Date
WO1998015855A1 true WO1998015855A1 (fr) 1998-04-16
WO1998015855A9 WO1998015855A9 (fr) 1998-07-02

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998031143A2 (fr) * 1997-01-10 1998-07-16 Koninklijke Philips Electronics N.V. Systeme eclairant pour un dispositif projecteur d'image
WO2003075554A1 (fr) * 2002-02-14 2003-09-12 Remtons Limited Analyseur a balayage
CN105814464A (zh) * 2013-12-05 2016-07-27 业纳光学系统有限公司 偏振系统
CN105842923A (zh) * 2016-06-02 2016-08-10 京东方科技集团股份有限公司 一种背光模组及显示装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3458248A (en) * 1966-10-03 1969-07-29 James F Eversole Light polarizing structure and process therefor utilizing cylindrical-shaped cavities within an isotropic sheet
US3912920A (en) * 1974-02-06 1975-10-14 Josuke Kubota Polarized light illumination device
US5124841A (en) * 1989-10-13 1992-06-23 Mitsubishi Rayon Co., Ltd. Polarization forming optical device and polarization beam splitter
US5359455A (en) * 1989-12-26 1994-10-25 Mitsubishi Rayon Co., Ltd. Polarization forming optical device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3458248A (en) * 1966-10-03 1969-07-29 James F Eversole Light polarizing structure and process therefor utilizing cylindrical-shaped cavities within an isotropic sheet
US3912920A (en) * 1974-02-06 1975-10-14 Josuke Kubota Polarized light illumination device
US5124841A (en) * 1989-10-13 1992-06-23 Mitsubishi Rayon Co., Ltd. Polarization forming optical device and polarization beam splitter
US5359455A (en) * 1989-12-26 1994-10-25 Mitsubishi Rayon Co., Ltd. Polarization forming optical device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998031143A2 (fr) * 1997-01-10 1998-07-16 Koninklijke Philips Electronics N.V. Systeme eclairant pour un dispositif projecteur d'image
WO1998031143A3 (fr) * 1997-01-10 1998-10-01 Koninkl Philips Electronics Nv Systeme eclairant pour un dispositif projecteur d'image
WO2003075554A1 (fr) * 2002-02-14 2003-09-12 Remtons Limited Analyseur a balayage
CN105814464A (zh) * 2013-12-05 2016-07-27 业纳光学系统有限公司 偏振系统
CN105814464B (zh) * 2013-12-05 2019-01-15 业纳光学系统有限公司 偏振系统
CN105842923A (zh) * 2016-06-02 2016-08-10 京东方科技集团股份有限公司 一种背光模组及显示装置

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