WO2021184925A1 - 投影*** - Google Patents

投影*** Download PDF

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Publication number
WO2021184925A1
WO2021184925A1 PCT/CN2020/142141 CN2020142141W WO2021184925A1 WO 2021184925 A1 WO2021184925 A1 WO 2021184925A1 CN 2020142141 W CN2020142141 W CN 2020142141W WO 2021184925 A1 WO2021184925 A1 WO 2021184925A1
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WO
WIPO (PCT)
Prior art keywords
refractive index
liquid crystal
projection system
light
index unit
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PCT/CN2020/142141
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English (en)
French (fr)
Inventor
陈晨
胡飞
余新
李屹
Original Assignee
深圳光峰科技股份有限公司
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Publication of WO2021184925A1 publication Critical patent/WO2021184925A1/zh

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/005—Projectors using an electronic spatial light modulator but not peculiar thereto
    • G03B21/006—Projectors using an electronic spatial light modulator but not peculiar thereto using LCD's
    • 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
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/2046—Positional adjustment of light sources
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/2053—Intensity control of illuminating light
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/2073—Polarisers in the lamp house

Definitions

  • This application relates to the field of projection technology, in particular to a projection system.
  • the current single-chip spatial light modulator projection display technology can achieve a contrast ratio of roughly several hundred to one to one or two thousand to one, which is far lower than the brightness resolution of the human eye. Therefore, the brightness of the projection display screen is not enough in bright places. The brightness of bright and dark places cannot be lowered, which makes people perceive the picture as poor, and a lot of details are lost.
  • the purpose of the high dynamic range (HDR) projection system is to increase the brightness range of the display, so that the bright and dark fields of the picture can display rich grayscale information, thereby greatly improving the effect of the picture and the audience's viewing experience.
  • the first method is the two-chip spatial light modulator technology.
  • the high contrast of the product of the two contrasts can be achieved, but the addition of the second piece of spatial light modulator greatly reduces the brightness of the projector. Its light efficiency can only reach 50% or even lower than that of ordinary projection systems. The lower light efficiency makes it difficult for the projection system to achieve higher peak brightness.
  • the second method is dynamic aperture technology.
  • the contrast of the DMD projection system is related to the aperture size of the projection lens.
  • a larger numerical aperture corresponds to a larger contrast.
  • the disadvantages of this method are: First, the response speed of the aperture control is slow, and it cannot change with every frame. Second, the use of mechanical mechanisms to adjust the diaphragm structure has reliability problems and also increases the cost of the system. Third, the use of a smaller aperture means lower brightness, so this solution will increase the contrast of the picture while also reducing the peak brightness of the picture, thereby affecting the viewing effect. Fourth, the method of reducing the aperture cannot obtain a large contrast. Therefore, the picture contrast using this method is far inferior to the projection system of the two-chip spatial light modulator.
  • the third method is the phase light steering (Light steering) technology.
  • the phase modulation liquid crystal device By adding a piece of phase modulation liquid crystal device in front of the spatial light modulator, and by controlling the phase retardation distribution of the phase modulation liquid crystal device, the light field distribution irradiated on the spatial light modulator is controlled to realize a high dynamic range projection system.
  • HDR projection equipment using phase light deflection technology can control the reduction of light efficiency to about 10%-20%.
  • the phase light deflection technology requires the coherence of the light source, so it can only be used in laser light sources. It is not ideal for fluorescent and LED light sources.
  • the reliability of the phase-modulated liquid crystal device is not high, and the cost is also high, which greatly increases the cost of using this technology.
  • phase-modulated liquid crystal cannot withstand high-power light sources.
  • phase-modulated liquid crystal can only modulate coherent light, the high coherence of the light source will produce speckle effects due to the fluctuation of the projection plane.
  • speckle can be solved by shaking the screen, additional vibration devices increase the cost and reliability of the system, and limit the application fields of pure laser projection.
  • the fourth method is similar to the local dimming technology adopted by LED-backlit LCDs.
  • the laser array is used as the light source of the projection device, and each laser is responsible for the illumination of an area.
  • the luminous intensity of the laser is dynamically controlled according to the peak brightness of each area of the screen to achieve high-contrast display. This method achieves high contrast while avoiding unnecessary loss of light energy, but its light source structure and modulation process are more complicated, and it is impossible to avoid the influence of different degrees of aging.
  • the purpose of this application is to provide a projection system to realize projection display with high dynamic range.
  • the embodiment of the application provides a projection system, including a light source, a spatial light modulator, and a beam deflector.
  • the light source is used to emit an illumination beam.
  • the beam deflector is arranged on the light path of the illumination beam.
  • the beam deflector includes arrays arranged in an array.
  • the refractive index of the variable refractive index material can be changed according to the intensity of the electric field applied to it, and the beam deflector is controlled to be applied to the variable refractive index material arranged in an array according to the image signal of the image to be projected
  • the electric field changes the refractive index of the variable refractive index material in at least a part of the area, and the illuminating light beam passing through the area is deflected, so that the illuminating light beam incident on the spatial light modulator forms a brighter area and a darker area.
  • variable refractive index unit is made of liquid crystal material.
  • variable refractive index unit includes liquid crystal cells, each liquid crystal cell has a first incident surface, a first exit surface, and a first connection surface, and the first incident surface is connected to the first exit surface and the first connection surface.
  • the first incident surface of the plurality of liquid crystal cells constitutes the light incident surface of the variable refractive index unit.
  • the liquid crystal cell has a wedge shape, and the included angle between the first connecting surface and the first incident surface is greater than 90°.
  • the angle between the first connecting surface and the normal of the first incident surface is equal to the dispersion angle of the illumination beam in the liquid crystal cell.
  • the included angle between the first connecting surface and the first incident surface is 120°-135°.
  • the liquid crystal cell is composed of nematic liquid crystals.
  • the direction of the optical axis of the liquid crystal molecules in the liquid crystal cell is perpendicular to the light incident surface.
  • the beam deflector further includes a fixed refractive index unit with a fixed refractive index, and the variable refractive index unit receives the illumination light beam emitted by the light source and emits it to the spatial light modulator from the fixed refractive index unit.
  • the fixed refractive index unit includes a plurality of crystal structures arranged side by side, the crystal structure has a second incident surface, a second exit surface, and a second connection surface, the second incident surface, the second exit surface, and the second connection Surface connection, each second incident surface corresponds to the first exit surface of a liquid crystal cell in the variable refractive index unit in a one-to-one correspondence.
  • the second connection surface of each crystal structure corresponds to a one-to-one correspondence with the first connection surface of a liquid crystal cell in the variable refractive index unit.
  • the second connection surface of each crystal structure is attached to the first connection surface of an adjacent liquid crystal cell.
  • the beam deflector further includes a first electrode and a second electrode, and the first electrode and the second electrode are used to apply an electric field to the variable refractive index unit.
  • the projection system further includes a control unit, which is electrically connected to the first electrode and the second electrode, so that the control unit controls the brightness of each area of the image to be projected to be applied to the arrays arranged in an array.
  • the electric field intensity of each area of the variable refractive index unit is electrically connected to the first electrode and the second electrode, so that the control unit controls the brightness of each area of the image to be projected to be applied to the arrays arranged in an array.
  • the light source includes a light-emitting device and a polarizer, and the polarizer is used to receive the light beam emitted by the light-emitting device and emit a ray-polarized illumination beam.
  • the projection system further includes a display lens, and the display lens is located on the optical path of the illumination beam emitted through the beam deflector.
  • the display lens includes an objective lens and an eyepiece arranged at intervals, and the illuminating light beam is sequentially transmitted through the objective lens and the eyepiece to the spatial light modulator.
  • a beam deflector with a variable refractive index unit is provided, and the electric field intensity of the electric field applied to the beam deflector is adjusted to realize the deflection of the illumination beam passing through the variable refractive index unit, and make The illumination beam incident on the spatial light modulator forms a brighter area and a darker area, thereby realizing the modulation of a light-turning high-dynamic projection system.
  • Fig. 1 is a schematic structural diagram of a projection system provided by an embodiment of the present application.
  • FIG. 2 is a schematic structural diagram of a liquid crystal shown in an embodiment of the present application.
  • FIG. 3 is a schematic diagram of a propagation path of a light beam in a liquid crystal shown in an embodiment of the present application;
  • Fig. 4 is a schematic structural diagram of a beam deflector provided by an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a partial split structure of a beam deflector provided by an embodiment of the present application.
  • Fig. 6 is a working principle diagram of a beam deflector provided by an embodiment of the present application.
  • Fig. 7 is a ⁇ - ⁇ variation curve of the beam deflector shown in an embodiment of the present application under a test environment
  • FIG. 8 is a schematic structural diagram of another projection system provided by an embodiment of the present application.
  • this embodiment provides a projection system 1, including a light source 20, a beam deflector 10, and a spatial light modulator 50.
  • the light source 20 is used to emit an illumination beam
  • the beam deflector 10 is located on the illumination beam emitted by the light source 20.
  • the spatial light modulator 50 is used to modulate the illumination beam emitted from the beam deflector 10 on the optical path.
  • the light source 20 may be a linearly polarized light source for generating a linearly polarized light beam, that is, the illuminating light beam is a linearly polarized light beam, for example, a laser beam may be directly generated by a laser as the illuminating light beam.
  • the light source 20 includes a light-emitting device 21 and a polarizer 22.
  • the polarizer 22 is used to receive the light beam emitted by the light-emitting device 21 and emit a linearly polarized light beam as an illuminating light beam.
  • the light-emitting device 21 may be a visible light-emitting device 21, such as an LED light source. It can be understood that when a laser is selected as the light source 20, the polarizer 22 may not be used.
  • the beam deflector 10 is located between the light path from the light source 20 to the spatial light modulator 50.
  • the beam deflector 10 has a variable refractive index unit 100, which has a refraction that changes according to the intensity of an electric field applied to it. That is, the refractive index of the variable refractive index unit 100 can be changed. And when the intensity of the electric field applied to the variable refractive index unit 100 changes, the refractive index of the variable refractive index unit 100 in at least a part of the area may be changed, or the refractive index of the variable refractive index unit 100 in the entire area may be changed. When the illuminating light beam passes through the variable refractive index unit 100 whose refractive index is changed, the illuminating light beam will be deflected.
  • a brighter area and a darker area can be formed. It can be understood that the brighter area and the darker area only represent relative brightness. The brightness of the brighter area is greater than the brightness of the darker area.
  • the variable refractive index unit 100 may be made of, for example, a liquid crystal material, and the liquid crystal material may be a nematic liquid crystal material or a ferroelectric liquid crystal material.
  • the variable refraction unit 100 may be formed into a roughly prismatic structure from a liquid crystal material, or may be formed in other shapes and structures.
  • Liquid crystals are classified into nematic liquid crystals, smectic liquid crystals, cholesteric liquid crystals, etc., and are widely used in displays, projection equipment, etc.
  • nematic liquid crystal driven by an external electric field, the director of the liquid crystal molecules (equivalent to the direction of the optical axis of the crystal) and the electric field form an angle ⁇ (referred to as the pointing angle), and the pointing angle ⁇ of the liquid crystal molecules depends on the magnitude of the applied electric field. Therefore, the refractive index of the liquid crystal material can be changed by applying an electric field, and a wedge-shaped liquid crystal cell can be fabricated accordingly, that is, the deflection angle of the optical path can be adjusted by an electric field.
  • the liquid crystal molecules tend to be aligned perpendicular to the direction of the electric field: when no electric field is applied, the directors of all liquid crystal molecules are parallel to the direction of the electric field; when an electric field is applied, the directors of the molecules move in the direction perpendicular to the direction of the electric field Deflection tends to be aligned along the direction of the electric field.
  • This type of liquid crystal is called Vertically Aligned Nematic (VAN: Vertically Aligned Nematic).
  • n o denotes the refractive index of the light
  • the iso-k-value surface of the k-space is a spherical surface.
  • the velocity direction of the light wave group (that is, the energy propagation direction, that is, the Poynting vector direction) is the same as the k propagation direction. This light corresponds to o light.
  • the iso-k-value surface of the k-space is an ellipsoidal surface.
  • the velocity direction of the light wave group (that is, the energy propagation direction, that is, the Poynting vector direction) is not the same as the k propagation direction, and this kind of light corresponds to e light.
  • ⁇ is also called dispersion angle.
  • the deflection of the light beam can be achieved by the liquid crystal, and by controlling the electric field intensity, the refractive index of the liquid crystal can be adjusted, thereby realizing the control of the deflection angle.
  • the variable refractive index unit 100 includes a plurality of liquid crystal cells 110 arranged side by side. Please refer to FIG. 4 and FIG. Triangular structure, where the longitudinal section refers to the section along the director direction of the liquid crystal cell.
  • Each liquid crystal cell 110 has a first incident surface 111, a first exit surface 113 and a first connection surface 112.
  • the first incident surface 111 is connected to the first exit surface 113 and the first connection surface 112.
  • one side of the first incident surface 111 is connected to one side of the first exit surface 113
  • the other side of the first exit surface 113 is connected to one side of the first connection surface 112, and the first connection surface
  • the other side of 112 is connected to the other side of the first incident surface 111.
  • the first incident surface 111, the first connection surface 112, and the first exit surface 113 form a liquid crystal cell that is approximately a triangular prism.
  • the included angle between the first connecting surface 112 and the first incident surface 111 may be greater than 90°. It can be understood that the included angle ⁇ between the first connecting surface 112 and the first incident surface 111 refers to the first connecting surface 112. An angle formed by intersecting the first incident surface 111 and opposite to the first exit surface 113. When light enters from the first incident surface 111, it travels through the liquid crystal cell 110 and exits from the first exit surface 113. The first exit surface 113 is also obliquely arranged with respect to the first incident surface 111, which is equivalent to forming a wedge-shaped structure.
  • the included angle ⁇ between the first connecting surface 112 and the first incident surface 111 is greater than 90°, which indicates that the first connecting surface 112 is arranged obliquely with respect to the first incident surface 111.
  • the advantage of this design is that the incident is incident from the first incident surface 111. During the propagation process of the light beam in the liquid crystal cell 110, the dispersed light escapes from the first connecting surface 112 into stray light.
  • ⁇ is the dispersion angle of the light beam in the liquid crystal cell 110, that is, the normal line between the first connecting surface 112 and the first incident surface 111
  • the included angle between the first exit surface 113 and the first incident surface 111 may be, for example, 30° to 60°. It can be understood that the included angle between the first exit surface 113 and the first incident surface 111 is Refers to the angle opposite to the first connecting surface 112.
  • the liquid crystal cell 110 has the following characteristics: in an electric field, when the magnitude of the electric field changes, the inclination angle of the optical axis of the liquid crystal molecules in the liquid crystal cell 110 changes, so that the direction of the emitted light can be changed.
  • Liquid crystals include thermotropic liquid crystals (thermotropic LC) and lyotropic liquid crystals (lyotropic LC), among which thermotropic liquid crystals include nematic, smectic, and cholesteric phases. It is understandable that, in this embodiment, the liquid crystal cell 110 may be any one of a nematic phase, a smectic phase, or a cholesteric phase, for example. In some embodiments, the liquid crystal cell 110 is composed of nematic liquid crystals. When no electric field is applied, the direction of the optical axis of the liquid crystal molecules in the liquid crystal cell 110 is perpendicular to the light incident surface.
  • the first incident surfaces 111 of the plurality of liquid crystal cells 110 constitute the light incident surface of the variable refractive index unit 100.
  • the first incident surfaces 111 of the plurality of liquid crystal cells 110 are located on the same plane and are successively connected end to end to form a continuous Plane.
  • the included angle ⁇ between the first connecting surface 112 and the first incident surface 111 may be, for example, 120° to 135°. Within this angle range, it is roughly consistent with the dispersion angle of the laser beam, which can more effectively prevent the dispersed light from escaping from the liquid crystal cell 110 to become stray light.
  • the beam deflector 10 may further include a fixed refractive index unit 200, wherein the fixed refractive index unit 200 has a fixed refractive index, that is, the refractive index of the fixed refractive index unit 200 is fixed.
  • the fixed refractive index unit 200 and the variable refractive index unit 100 are bonded together, and the illumination light beam emitted from the variable refractive index unit 100 enters the fixed refractive index unit 200 and is emitted from the fixed refractive index unit 200 to the spatial light modulator 50.
  • the fixed refractive index unit 200 and the variable refractive index unit 100 can be attached to each other, that is, when the illumination beam propagates from the variable refractive index unit 100 to the fixed refractive index unit 200, there is no other propagation medium.
  • the variable refractive index unit 100 enters the fixed refractive index unit 200 directly.
  • the variable refractive index unit 100 and the fixed refractive index unit 200 may also have a predetermined interval.
  • the fixed refractive index unit 200 includes a plurality of crystal structures 210 arranged side by side, and the plurality of crystal structures 210 may be arranged in a form that cooperates with a plurality of liquid crystal cells 110.
  • the plurality of crystal structures 210 may be combined with a plurality of liquid crystal cells 110.
  • the liquid crystal cells 110 are arranged alternately with each other.
  • the crystal structure 210 has a fixed refractive index, that is, under the action of an electric field, the refractive index of the crystal structure 210 remains basically unchanged or completely unchanged.
  • the material of the crystal structure 210 may be resin, such as epoxy resin, etc.
  • the crystal structure 210 may also be made of materials such as glass, quartz, polycarbonate, polypropylene, etc., for example.
  • the crystal structure 210 has a second incident surface 211, a second exit surface 213, and a second connecting surface 212.
  • the second incident surface 211 is connected to the second exit surface 213 and the second connecting surface 212, and the second exit surface 213 is connected to the second connecting surface 212.
  • the incident surface 211 is also connected correspondingly to form a roughly wedge-shaped structure. Specifically, one side of the second incident surface 211 is connected to one side of the second exit surface 213, the other side of the second incident surface 211 is connected to one side of the second connecting surface 212, and the second exit The other side of the surface 213 and one side of the second incident surface 211 are also connected correspondingly.
  • Each second incident surface 211 corresponds to the first exit surface 113 of a liquid crystal cell 110 in the variable refractive index unit 100 in a one-to-one correspondence. It can be understood that the second incident surface 211 is adhered to the first exit surface 113.
  • the bonding may be complete bonding, that is, the area of the first exit surface 113 and the area of the second incident surface 211 completely overlap.
  • the second connecting surface 212 may be parallel to the first connecting surface 112 of one liquid crystal cell 110 in the variable refractive index unit 100 or be attached to each other in a one-to-one correspondence.
  • the second connecting surface 212 When the second connecting surface 212 is in one-to-one correspondence with the first connecting surface 112 of one liquid crystal cell 110 in the variable refractive index unit 100, it may mean that the second connecting surface 212 is in one-to-one correspondence with the first connecting surface 112 of the liquid crystal cell 110 in the variable refractive index unit 100.
  • the first connecting surface 112 of one liquid crystal cell 110 in the variable refractive index unit 100 is completely attached. That is, the areas of the second connection surface 212 and the first connection surface 112 are completely equal, and at this time, the first connection surface 112 and the second connection surface 212 are also parallel to each other.
  • the second exit surfaces 213 of the plurality of crystal structures 210 constitute the light exit surface of the fixed refractive index unit 200.
  • the second exit surfaces 213 of the plurality of crystal structures 210 are located on the same plane and constitute a continuous light exit surface.
  • the light incident through the light incident surface of the variable refractive index unit 100 is emitted from the light exit surface of the fixed refractive index unit 200.
  • the light exit surface and the light entrance surface are parallel to each other, so as to more accurately control the exit angle of the exiting light.
  • the beam deflector 10 further includes a first electrode 300 and a second electrode 400, and the first electrode 300 and the second electrode 400 are used to apply an electric field to the variable refractive index unit 100.
  • the direction of the electric field can be parallel to the director direction of the liquid crystal or perpendicular to the director direction of the liquid crystal.
  • the first electrode 300 and the second electrode 400 may be distributed on the glass cover plate located on the light incident surface and the glass cover plate located on the light output surface.
  • the first electrode 300 and the second electrode 400 can be, for example, metal electrodes, calomel electrodes, etc., and can be applied to the light incident surface and the light exit surface, respectively, so that the direction of the formed electric field is parallel to the director direction of the liquid crystal when the liquid crystal is not deflected.
  • the projection system 10 further includes a control unit (not shown).
  • the control unit may be, for example, a central processing unit (CPU).
  • the control unit may be electrically connected to the first electrode 300, the second electrode 400, and the light source 20. , To control the intensity of the electric field applied to the variable refractive index unit 100.
  • the image signal to be projected is first received, and each frame of the image signal to be projected may include multiple partitions (for example, each partition may be connected to the first incident surface 111 of a variable refractive index unit 100). The area of the image is matched), the brightness and color of the image on these partitions can be different.
  • the control unit controls the light source 20 to generate the illumination beam of the corresponding color according to the signal, and guide it to the beam deflector 10.
  • the control unit can control the first electrode 300 and the second electrode 400 according to the brightness information of each subarea of the real-time image, and then control and adjust the variable refractive index units arranged in an array on the beam deflector 10
  • the intensity of the electric field on 100 realizes the adjustment of the brightness of the light on each variable refractive index unit 100, that is, relatively bright and dark areas are formed, and then the light beam is directed to the spatial light modulator 50 and then projected outwards. HDR display effect.
  • n o is the refractive index of ordinary light o light
  • n e is the refractive index of e light when the director of the liquid crystal molecules is perpendicular to the direction of the electric field, and the angle ⁇ depends on the size of the applied electric field, so the electric field can adjust the refraction of the liquid crystal material Rate.
  • the refractive index of the index matching material is selected the same as n and F n o
  • a constant deflection of the linearly polarized incident light does not occur.
  • V a certain voltage
  • the VAN liquid crystal molecules are deflected, and the angle between the director of the liquid crystal molecules and the direction of the electric field becomes ⁇ .
  • the incident light polarized in the plane becomes the e-light of the liquid crystal cell and is deflected at a certain angle ⁇ .
  • the refractive index of the liquid crystal cell 110 is n eff
  • the refractive index of the crystal structure 210 is n F , according to the law of refraction:
  • ⁇ ⁇ F
  • the light will be deflected to a certain extent in the birefringent crystal.
  • the light is deflected again, and the light enters the isotropic crystal after being deflected, and its wave vector direction is consistent with the energy propagation direction. Therefore, the direction of the emitted light can be uniquely determined by the law of refraction.
  • the angle between the refracted light and the normal direction of the refracting surface is ⁇ 2 , and the clockwise direction is taken as positive. It is defined that the angle ⁇ F between the first exit surface 113 and the vertical direction is positive in the clockwise direction, and the angle ⁇ between the vertical direction and the refracted light is positive in the clockwise direction, so the overall deflection angle of the light relative to the incident direction .
  • a light deflection of at least 2 degrees can be obtained by selecting an appropriate n F and the initial angle of the liquid crystal. The deflection of this angle can be converted into a movement of the light spot's spatial position using subsequent optical means.
  • the beam deflector 10 provided in this embodiment can provide a deflection angle for the light, and at the same time, since the first connecting surface 112 is arranged to be inclined with respect to the first incident surface 111, the dispersive light can be prevented from flowing from the first connecting surface. 112 escapes as stray light, that is, prevents the light beam from escaping from the side of the beam deflector 10.
  • the projection system 1 may further include a display lens 40.
  • the display lens 40 is arranged on the optical path of the illumination beam emitted from the beam deflector 10, and is located between the beam deflector 10 and the spatial light modulator.
  • the beam deflector 10 is arranged on the front focal plane of the display lens 40; the beam deflector 10 can be arranged on the front focal plane of the display lens 40 to form an f- ⁇ lens system.
  • the spatial light modulator 50 may be DMD, LCD, LCoS, or the like. The spatial light modulator 50 is used to receive the illuminating light beam transmitted by the display lens 40 and to modulate the illuminating light beam to emit it.
  • the display lens 40 may include an objective lens 41 and an eyepiece 42 arranged at intervals, and the deflected light beam is sequentially transmitted through the objective lens 41 and the eyepiece 42 to the spatial light modulator 50.
  • the focal length of the objective lens 41 is f 1
  • the focal length of the eyepiece 42 is f 2
  • the distance between the two lenses is d.
  • the beam deflector 10 is placed on the front focal plane of the display lens 40 and the spatial light modulator 50 is placed on the rear focal plane of the display lens 40.
  • the distance from the objective lens 41 to the beam deflector 10 Distance from eyepiece 42 to spatial light modulator 50
  • the selection of d needs to satisfy f FFL , f BFL > 0, that is, d ⁇ f 1 , f 2 .
  • the distance between the objective lens 41 and the beam deflector 10 may be smaller than the distance between the eyepiece 42 and the spatial light modulator 50, so that the size of the lens spot can be controlled, thereby reducing the size of subsequent optical elements.
  • the telecentricity of the system can be improved, so that the light irradiated on the spatial light modulator 50 is more uniform in space including the angular distribution, which is helpful for subsequent illumination on the light modulator.
  • the telecentricity is a physical quantity that measures the degree of parallelism between the chief rays and the optical axis. The better the telecentricity, the better the parallelism between the chief rays and the optical axis.
  • the working principle of the projection system 1 provided in this embodiment is: the light source 20 emits an illumination beam, and the illumination beam is incident on the variable refractive index unit 100. At this time, the intensity of the electric field applied to the variable refractive index unit 100 is controlled to make the illumination beam The variable refractive index unit 100 is deflected at a predetermined deflection angle, and the deflected illumination beam is emitted from the fixed refractive index unit 200 to the lens system 40, and the lens system 40 transmits the illumination beam and enters the spatial light modulator 50.
  • the electric field intensity of the electric field applied to the beam deflector 10 is adjusted to realize the deflection of the illumination beam passing through the variable refractive index unit 100 and make it enter the space
  • the illumination beam of the light modulator 50 forms a brighter area and a darker area, thereby realizing the modulation of the light-turning high-dynamic projection system.

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Abstract

一种投影***（1），包括光源（20）、空间光调制器（50）以及光束偏转器（10），光束偏转器（10）设置于照明光束的光路上，光束偏转器（10）包括呈阵列排布的可变折射率单元（100），光束偏转器（10）根据待投影图像的图像信号控制施加在呈阵列排布的可变折射率单元（100）上的电场，使得至少部分区域的可变折射率单元（100）的折射率改变，经过这部分区域的照明光束发生偏转，以使入射到空间光调制器（50）的照明光束形成较亮区域和较暗区域。通过设置具有可变折射率单元（100）的光束偏转器（10），通过对施加于光束偏转器（10）的电场的电场强度进行调控，实现经过可变折射率单元（100）的照明光束的偏转，并使入射到空间光调制器（50）的照明光束形成较亮区域和较暗区域，进而实现光转向型高动态投影***（1）的调制。

Description

投影*** 技术领域
本申请涉及投影技术领域，具体涉及一种投影***。
背景技术
目前单片空间光调制器的投影显示技术能达到的对比度大致为几百比一到一两千比一，远远低于人眼的亮度分辨力，因此投影显示的画面在明亮处的亮度不够亮，暗处的亮度降不下来，使人们感知到的画面层次较差，大量细节丢失。高动态范围(HDR)的投影***的目的就是提升显示的亮度范围，使得画面中的亮场和暗场部分都能显示丰富的灰阶信息，从而大大提高画面的效果和观众的观影体验。
目前，投影***实现HDR显示的方法主要有以下几种：
第一种方法是双片式空间光调制器技术。通过在DMD后加入另一片空间光调制器可以实现两者对比度乘积的高对比度，但由于第二片空间光调制器的加入，使得投影机的亮度大大降低。其光效只能达到普通投影***的50％甚至更低，较低的光效使得投影***在实现更高的峰值亮度方面变得困难。
第二种方法是动态光圈技术。DMD投影***的对比度和投影镜头的光圈大小相关。一般而言，越大的数值孔径对应越大的对比度。这种方法的缺点在于：第一，光圈控制的响应速度慢，无法跟随每一帧变化而变化。第二，采用机械机构调整光圈结构，存在可靠性的问题，也增加了***的成本。第三，采用更小的光 圈意味着更低的亮度，因而这种方案在增加画面对比度的同时也会导致画面峰值亮度的降低，从而影响观影的效果。第四，通过减小光圈的方法无法获得很大的对比度。因此采用这种方法的画面对比度远不能和双片式空间光调制器的投影***相比。
第三种方法是相位光偏转(Light steering)技术。通过在空间光调制器前加入一片相位调制液晶器件，通过控制相位调制液晶器件的相位延迟分布来控制照射到空间光调制器上的光场分布以实现高动态范围的投影***。采用相位光偏转技术的HDR投影设备相比传统投影设备，光效降低能够控制在10％-20％左右。但是相位光偏转技术要求光源的相干性，因而只能使用在激光光源上。对于荧光和LED光源效果并不理想。同时，相位调制的液晶器件可靠性还不高，成本也居高不下，从而大大增加了利用此技术的成本。并且，相位调制的液晶无法承受大功率的光源，此外，由于相位调制液晶只能调制相干光，光源的高相干性会由于投影平面的起伏产生散斑效应。虽然可以通过抖屏的方式解决散斑，但是额外的震动器件增加了***的成本和可靠性，限制了纯激光投影的应用领域。
第四种方法是类似LED背光LCD采用的local dimming技术。采用激光器阵列作为投影设备光源，每个激光器负责一个区域的照明，在投影显示时，根据画面各个区域的峰值亮度来动态控制激光器的发光强度，以实现高对比度显示。这种方法在实现了高对比度的同时避免了不必要的光能损失，但是它的光源结构和调制过程都比较复杂，且无法避免老化程度不同带来的影响。
可见，以上的各种方法均不能较好的实现高动态范围的投影。
发明内容
本申请的目的在于提供一种投影***，以实现高动态范围的投影显示。
本申请实施例提供了一种投影***，包括光源、空间光调制器以及光束偏转器，光源用于发射照明光束，光束偏转器设置于照明光束的光路上，光束偏转器包括呈阵列排布的可变折射率材料，可变折射率材料的折射率能根据对其施加的电场强度而发生变化，光束偏转器根据待投影图像的图像信号控制施加在呈阵列排布的可变折射率材料上的电场，使得至少部分区域的可变折射率材料的折射率改变，经过该区域的照明光束发生偏转，以使入射到空间光调制器的照明光束形成较亮区域和较暗区域。
在一些实施方式中，可变折射率单元由液晶材料制成。
在一些实施方式中，可变折射率单元包括液晶盒，每个液晶盒具有第一入射面、第一出射面以及第一连接面，第一入射面与第一出射面以及第一连接面连接，多个液晶盒的第一入射面构成可变折射率单元的入光面。
在一些实施方式中，液晶盒呈楔形，且第一连接面与第一入射面的夹角大于90°。
在一些实施方式中，第一连接面与第一入射面的法线之间的夹角等于照明光束在液晶盒中的色散角。
在一些实施方式中，第一连接面与第一入射面的夹角为120°-135°。
在一些实施方式中，液晶盒由向列液晶构成，未施加电场时，液晶盒中液晶分子的光轴方向与入光面垂直。
在一些实施方式中，光束偏转器还包括具有固定折射率的固定折射率单元，且可变折射率单元接收光源出射的照明光束，并由固定折射率单元出射至空间光调制器。
在一些实施方式中，固定折射率单元包括并排设置的多个晶体结构，晶体结构具有第二入射面、第二出射面以及第二连接面，第二入射面与第二出射面以及 第二连接面连接，每个第二入射面一一对应的与可变折射率单元中的一个液晶盒的第一出射面贴合。
在一些实施方式中，每个晶体结构的第二连接面一一对应的与可变折射率单元中的一个液晶盒的第一连接面平行。
在一些实施方式中，每个晶体结构的第二连接面与相邻的液晶盒的第一连接面贴合。
在一些实施方式中，光束偏转器还包括第一电极以及第二电极，第一电极以及第二电极用于对可变折射率单元施加电场。
在一些实施方式中，投影***还包括控制单元，控制单元与第一电极以及第二电极电性连接，以使控制单元根据待投影图像的各区域的亮度控制施加于呈阵列排布的各个可变折射率单元的各区域的电场强度。
在一些实施方式中，光源包括发光装置和起偏器，起偏器用于接收发光装置发出的光束，并出射线偏振的照明光束。
在一些实施方式中，投影***还包括显示透镜，显示透镜位于经光束偏转器出射的照明光束的光路上。
在一些实施方式中，显示透镜包括间隔设置的物镜和目镜，照明光束依次经物镜以及目镜透射至空间光调制器。
本申请提供的投影***，通过设置具有可变折射率单元的光束偏转器，通过对施加于光束偏转器的电场的电场强度进行调控，实现经过可变折射率单元的照明光束的偏转，并使入射到空间光调制器的照明光束形成较亮区域和较暗区域，进而实现光转向型高动态投影***的调制。
本申请的这些方面或其他方面在以下实施例的描述中会更加简明易懂。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的一种投影***的结构示意图；
图2是本申请实施例示出的一种液晶的结构示意图；
图3是本申请实施例示出的一种光束在液晶的传播路径示意图；
图4是本申请实施例提供的一种光束偏转器的结构示意图；
图5是本申请实施例提供的一种光束偏转器的局部拆分结构示意图；
图6是本申请实施例提供的光束偏转器的工作原理图；
图7是本申请实施例示出的光束偏转器在一种测试环境下的Δ-θ变化曲线；
图8是本申请实施例提供的又一种投影***的结构示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
参阅图1，本实施例提供一种投影***1，包括光源20、光束偏转器10以及空间光调制器50，其中，光源20用于发射照明光束，光束偏转器10位于光源20发出的照明光束的光路上，空间光调制器50用于调制从光束偏转器10出射的照明光束。
其中，请继续参阅图1，光源20可以是线偏振光源，用于产生线偏振光束，即照明光束为线偏振光束，例如可以直接由激光器产生激光光束作为照明光束。在一些实施方式中，光源20包括发光装置21和起偏器22，起偏器22用于接收发光装置21发出的光束，并出射形成线偏振光束作为照明光束。此时发光装置21可以是可见光发光装置21，例如LED光源。可以理解，当选用激光器作为光源20时，可以不需要使用起偏器22。
光束偏转器10位于从光源20至空间光调制器50的光路之间，光束偏转器10具有可变折射率单元100，可变折射率单元100具有根据对其施加的电场强度而发生变化的折射率，即可变折射率单元100的折射率可以改变。并且当施加于可变折射率单元100的电场强度发生改变时，可以使得至少部分区域的可变折射率单元100的折射率改变，或者全部区域的可变折射率单元100的折射率改变。当照明光束经过折射率改变的可变折射率单元100时，照明光束会发生偏转。
经光束偏转器10出射的发生偏转的照明光束在入射至空间光调制器50时，可以形成较亮区域和较暗区域，可以理解的是，较亮区域和较暗区域仅表示相对的亮度，较亮区域的亮度大于较暗区域的亮度。
可变折射率单元100例如可以由液晶材料制成，液晶材料可以是向列液晶材料或者铁电液晶材料等。可变折射单元100可以由液晶材料形成大致的棱形结构，或者形成其他形状结构。
液晶分为向列相液晶、近晶相液晶、胆甾相液晶等，广泛应用于显示器、投影设备等。以向列相液晶为例，在外部电场驱动下，液晶分子指向矢(相当于晶体光轴方向)与电场成夹角θ(简称指向角)，液晶分子的指向角θ取决于外加电场的大小，因此通过外加电场可以改变液晶材料的折射率，据此可以制作楔形液 晶盒，即可以通过外加电场调节光路的偏转角。如图1所示，液晶分子倾向于垂直于电场方向排列：当未加电场时，所有液晶分子的指向矢与电场方向平行；当外加电场时，分子的指向矢朝着垂直于电场方向的方向偏转，倾向于沿电场方向排列，这类液晶称为垂直排列向列液晶(VAN：Vertically Aligned Nematic)。
请一并参阅图2和图3，对于在均匀介质中传播的时谐平面波，其波动方程为k×(k×E)+μ∈ω 2E＝0。展开成向量形式为k(k·E)-(k·k)E+μ∈ω 2E＝0，其矩阵形式为
Figure PCTCN2020142141-appb-000001
写成
Figure PCTCN2020142141-appb-000002
其中
Figure PCTCN2020142141-appb-000003
μ＝μ rμ 0,∈＝∈ r∈ 0。
对于单轴双折射液晶材料，
Figure PCTCN2020142141-appb-000004
其中n o表示O光的折射率，n e表示光沿着单轴双折射晶体光轴所对应的折射率。若n e>n o，则称该单轴双折射晶体为正双折射晶体；若n e<n o，则称该单轴双折射晶体为负双折射晶体。由于存在非零电场解，可得det(M)＝0.从而推出
Figure PCTCN2020142141-appb-000005
可以看出，具有两种不同的平面波可以满足上述条件：第一种，
Figure PCTCN2020142141-appb-000006
Figure PCTCN2020142141-appb-000007
其k空间的等k值面为球面。光波群速度方向(即能量传播方向，亦即 Poynting矢量方向)与k传播方向相同。这种光对应o光。另外一种，
Figure PCTCN2020142141-appb-000008
Figure PCTCN2020142141-appb-000009
其k空间的等k值面为椭球面。一般情况下，光波群速度方向(即能量传播方向，亦即Poynting矢量方向)与k传播方向并不相同，这种光对应e光。
当一束光垂直入射液晶界面时，假设此液晶中液晶分子指向矢与界面法向夹角为θ，如图3所示。其中o光沿着入射光方向继续传播，而e光传播方向发生偏折，其偏折角α满足以下关系
Figure PCTCN2020142141-appb-000010
也可以表示成
Figure PCTCN2020142141-appb-000011
α也叫做色散角(dispersion angle)。
由此可知，当θ＝0或
Figure PCTCN2020142141-appb-000012
时，α＝0，即o光、e光均不发生偏折。
基于以上原理，可以通过液晶实现光束的偏转，并且通过控制电场强度，可以对液晶的折射率进行调节，进而实现对偏折角度的控制。
作为一种实施方式，可变折射率单元100包括并排设置的多个液晶盒110，请一并参阅图4和图5，其中，每个液晶盒110呈大致的楔形，其纵向截面呈大致的三角形结构，其中纵向截面是指沿液晶盒的指向矢方向的截面。每个液晶盒110具有第一入射面111、第一出射面113以及第一连接面112。第一入射面111与第一出射面113以及第一连接面112连接。具体的，第一入射面111的一侧边与第一出射面113的一侧边连接，第一出射面113的另一侧边与第一连接面112的一侧边连接，第一连接面112的另一侧边与第一入射面111的另一侧边连接。第一入射面111、第一连接面112与第一出射面113围成近似三棱柱的液晶盒。
在一些实施方式中，第一连接面112与第一入射面111的夹角可以大于90°， 可以理解，第一连接面112与第一入射面111的夹角β是指第一连接面112与第一入射面111相交形成的与第一出射面113相对的角。当光从第一入射面111入射后，经液晶盒110传播从第一出射面113出射。第一出射面113也是相对于第一入射面111倾斜设置的，相当于形成一楔形结构。
第一连接面112与第一入射面111的夹角β大于90°，表明第一连接面112是相对于第一入射面111倾斜设置的，这样设计的好处在于：从第一入射面111入射的光束在液晶盒110中的传播过程中，减小色散光从第一连接面112逸出成为杂散光。其中β例如可以设置为＝π/2+α，即α+90°，其中α为光束在液晶盒110内的色散角，也即是第一连接面112与第一入射面111的法线之间的夹角为α，其中第一入射面111的法线是指垂直于第一入射面111并朝第一出射面113方向延伸的射线。由于第一连接面112相对于第一入射面111倾斜，当光束从第一入射面111入射后再液晶盒110内发生偏转，同时偏转光发生色散现象，但由于夹角β＝π/2+α，色散光无法从第一连接面112逸出，而是会从第一出射面113出射，因此可以避免形成杂散光。
在一些实施方式中，第一出射面113与第一入射面111之间的夹角例如可以是30°至60°，可以理解第一出射面113与第一入射面111之间的夹角是指与第一连接面112相对的夹角。
液晶盒110具有以下特性：在电场中，当电场的大小发生改变时液晶盒110中的液晶分子的光轴的倾斜角度发生改变，从而可以改变出射光的方向。液晶包括热致液晶(thermotropic LC)和溶致液晶(lyotropic LC)，其中热致液晶又包括向列相、近晶相、胆甾相三种。可以理解的是，本实施例中，液晶盒110例如可以是向列相、近晶相或者是胆甾相的任意一种。在一些实施方式中，所述液晶盒110由向列相液晶构成，未施加电场时，所述液晶盒110中液晶分子的光 轴方向与所述入光面垂直。
多个液晶盒110的第一入射面111构成可变折射率单元100的入光面，在一些实施方式中，多个液晶盒110的第一入射面111位于同一平面且依次首尾相接形成连续的平面。
其中，在一些实施方式中，第一连接面112与所述第一入射面111的夹角β例如可以是120°至135°。在该角度范围内，与激光光束的色散角大致相符合，可以更为有效的防止色散光逸出液晶盒110成为杂散光。
在一些实施方式中，光束偏转器10还可以包括固定折射率单元200，其中固定折射率单元200具有固定的折射率，即固定折射率单元200的折射率是固定不变的。固定折射率单元200与可变折射率单元100相贴合，从可变折射率单元100出射的照明光束入射至固定折射率单元200，并从固定折射率单元200出射至空间光调制器50。在一些实施方式中，固定折射率单元200可以与可变折射率单元100相互贴合，即照明光束从可变折射率单元100向固定折射率单元200传播的过程中，不存在其他传播介质，直接由可变折射率单元100进入固定折射率单元200。当然，在其他的一些实施方式中，可变折射率单元100与固定折射率单元200之间也可以具有预定的间隔。
作为一种实施方式，固定折射率单元200包括并排设置的多个晶体结构210，多个晶体结构210可以设置成与多个液晶盒110相互配合的形式，例如多个晶体结构210可以与多个液晶盒110彼此交错设置。
晶体结构210具有固定的折射率，即晶体结构210在电场作用下，其折射率基本保持不变或完全不变。例如，晶体结构210的材料可以为树脂，例如环氧树脂等，在一些实施方式中，晶体结构210例如还可以采用玻璃、石英、聚碳酸酯、聚丙烯等材料制成。
晶体结构210具有第二入射面211、第二出射面213以及第二连接面212，第二入射面211与第二出射面213以及第二连接面212连接，且第二出射面213与第二入射面211也相应连接，形成大致的楔形结构。具体的，第二入射面211的一侧边与第二出射面213的一侧边连接，第二入射面211的另一侧边与第二连接面212的一侧边连接，且第二出射面213的另一侧边与第二入射面211的一侧边也相应连接。当光束第一出射面113出射后从第二入射面211入射并从第二出射面213出射。
每个第二入射面211一一对应的与可变折射率单元100中的一个液晶盒110的第一出射面113贴合，可以理解的是，第二入射面211与第一出射面113贴合可以是完全贴合，即第一出射面113的面积与第二入射面211的面积完全重合。且在一些实施方式中，第二连接面212可以一一对应的与所述可变折射率单元100中的一个液晶盒110的第一连接面112平行或者相互贴合。
当第二连接面212一一对应的与所述可变折射率单元100中的一个液晶盒110的第一连接面112相互贴合时，可以是指第二连接面212一一对应的与所述可变折射率单元100中的一个液晶盒110的第一连接面112完全贴合。即第二连接面212与第一连接面112的面积完全相等，此时第一连接面112和第二连接面212也是相互平行的。可以理解的是，对于一个晶体结构210而言，其第二连接面212与一个液晶盒110的第二连接面212贴合，其第二入射面211与相邻的另一个液晶盒110的第一出射面113贴合。即晶体结构210嵌在两个相邻的液晶盒110之间，对应的，一个液晶盒110嵌在两个相邻的晶体结构210之间。
多个晶体结构210的第二出射面213构成固定折射率单元200的出光面，在一些实施方式中，多个晶体结构210的第二出射面213位于同一平面，且构 成连续的出光面。经可变折射率单元100的入光面入射的光由固定折射率单元200的出光面射出。在一些实施方式中，出光面和入光面相互平行，以更为精确的控制出射光的出射角度。
在一些实施方式中，光束偏转器10还包括第一电极300以及第二电极400，所述第一电极300以及第二电极400用于对所述可变折射率单元100施加电场。其中电场的方向可以是平行于液晶的导向矢方向，也可以是垂直于液晶的导向矢方向。第一电极300和第二电极400可以分布设置于位于入光面的玻璃盖板以及位于出光面的玻璃盖板上。第一电极300和第二电极400例如可以是金属电极、甘汞电极等，并可以分别施加于入光面和出光面，使得形成的电场方向与液晶在未偏转时的指向矢方向平行。
在一些实施方式中，投影***10还包括控制单元(图未示)，控制单元例如可以是中央处理器(CPU)，控制单元可以与第一电极300、第二电极400以及光源20电性连接，以控制施加于可变折射率单元100的电场强度。在投影***10进行投影显示时，首先接收待投影图像信号，待投影图像信号的每一帧图像可以包括多个分区(每个分区例如可以与一个可变折射率单元100的第一入射面111的面积相匹配)，这些分区上的图像亮度、颜色可以不同的。当待投影图像信号输入至投影***10后，控制单元根据该信号，控制光源20产生对应颜色的照明光束，并引导至光束偏转器10。此时，控制单元可以根据实时的图像的各个分区的亮度信息，控制第一电极300以及第二电极400，进而控制调整施加于光束偏转器10上的呈阵列排布的各个可变折射率单元100上的电场强度，进而实现各个可变折射率单元100上的光线亮度的调整，即形成相对的较亮区域和较暗区域，然后将光束引导至空间光调制器50后向外投射，实现HDR的显示效果。
下面以采用向列相液晶作为液晶盒110为例，对本实施例提供的光束偏转 器10的工作原理进行详细说明。
参阅图6，在向列相液晶中，在外部电场驱动下，液晶分子指向矢与点成夹角θ＝θ(V)，此时会发生双折射现象。当非常光e光波法线与电场同向时，其折射率n 2可用下式表示：
Figure PCTCN2020142141-appb-000013
其中n o为寻常光o光的折射率，n e为e光在液晶分子指向矢垂直于电场方向时的折射率，而角θ取决于外加电场的大小，因此可以通过电场调节液晶材料的折射率。
具体地，假设选择的折射率匹配材料的折射率n F与n o相同，在未加电压时，以一定线偏振入射的入射光不会发生偏折。当单元的两段施加一定电压V后，VAN液晶分子发生偏转，液晶分子的指向矢与电场方向夹角变为θ。在平面内偏振的入射光成为该液晶单元的e光，会发生一定角度α的偏转。传播到第一出射面113时，由于n eff此时变得与n F不同，在界面处近一步发生折射。
液晶偏转后，液晶盒110的折射率为n eff，晶体结构210的折射率为n F，根据折射定律：
Figure PCTCN2020142141-appb-000014
其中入射光与折射面的法线方向角度为θ 1＝α F，原因在于以图4中偏振方向正入射的e光的波矢量也沿竖直方向。但由于色散角α的存在光线在双折射晶体内会发生一定的偏转。到了楔形界面处，光线再次发生偏转，光线发生偏折之后进入各向同性晶体，其波矢量方向与能量传播方向一致。因此出射光方向可由折射定律唯一确定。
折射光与折射面的法线方向角度为θ 2，且取顺时针方向为正。定义第一出射面113与竖直方向夹角α F沿着顺时针方向为正，竖直方向与折射光夹角Δ沿着顺 时针方向为正，因此光线相对于入射方向的整体偏折角度。
Δ＝θ 2-α F    (Eq.1)
其中
Figure PCTCN2020142141-appb-000015
将Eq.2-3带入Eq.1中可得
Figure PCTCN2020142141-appb-000016
可以看出，一方面，当α F＝0时，器件退化为平行液晶板，Δ＝0，说明常见的平行液晶板不具有偏转光线的功能。另外一方面，当n F≤n o时，
Figure PCTCN2020142141-appb-000017
Figure PCTCN2020142141-appb-000018
可得Δ≥0；当n F≥n e时，
Figure PCTCN2020142141-appb-000019
此时Δ≤0；当n o＜n F＜n e时，Δ可正可负。
作为一种示例，以典型VAN液晶TL216为例进行说明，TL216在25℃条件下，550nm波长处的折射率n o＝1.53，n e＝1.74。
从图7可以看出，选取合适的n F、液晶初始角度可以获得至少2度的光线偏转。这个角度的偏转可以使用后续的光学手段将其转变为光斑空间位置的移动。
本实施例中提供的光束偏转器10，在可以为光线提供偏转角度的同时，由于将第一连接面112设置成相对于第一入射面111倾斜的形式，可以防止色散光从第一连接面112逸出成为杂散光，即防止光束从光束偏转器10的侧面逸出。
请再次参阅图1，在一些实施方式中，投影***1还可以包括显示透镜40，显示透镜40设置于从光束偏转器10出射的照明光束的光路上，且位于光束偏转器10与空间光调制器50之间的光路上。其中，光束偏转器10设置于显示透镜40的前焦面；光束偏转器10可以设置在显示透镜40的前焦平面上，构成f-θ透镜***。空间光调制器50可以为DMD，LCD或者LCoS等。空间光调制器50用于接收来显示透镜40透过的照明光束并进行调制后出射。
在一些实施方式中，参阅图8，显示透镜40可以包括间隔设置的物镜41和目镜42，偏转光束依次经物镜41以及目镜42透射至空间光调制器50。
假设物镜41的焦距为f 1，目镜42的焦距为f 2，两个透镜之间的距离为d。使得光束偏转器10处在显示透镜40的前焦平面上，空间光调制器50处在显示透镜40的后焦平面上。在薄透镜近似下，物镜41到光束偏转器10的距离
Figure PCTCN2020142141-appb-000020
Figure PCTCN2020142141-appb-000021
目镜42到空间光调制器50的距离
Figure PCTCN2020142141-appb-000022
为保证清晰的成像，d的选择需要满足f FFL,f BFL>0，即d<f 1,f 2。在一些实施方式中，物镜41到光束偏转器10的距离可以小于目镜42到空间光调制器50的距离，这样可以控制达到透镜光斑的大小，从而减小后继光学元件的尺寸。
通过由间隔的物镜41和目镜42构成显示透镜40，可以提高***的远心度，使得照射在空间光调制器50的光空间上包括角度分布上更加均匀，有助于后续光调制器上照明光的设计。其中，远心度是是衡量主光线(chief rays)跟光轴(optical axis)平行程度的物理量，远心度越好，主光线与光轴的平行度越好。
本实施例中提供的投影***1的工作原理是：光源20发射照明光束，照明光束入射至可变折射率单元100，此时通过控制施加于可变折射率单元100的电场强度，使得照明光束在可变折射率单元100上按照预定的偏转角度进行偏转，偏转后的照明光束从固定折射率单元200出射至透镜***40，透镜***40透过照明光束后入射至空间光调制器50。
通过设置具有可变折射率单元100的光束偏转器10，通过对施加于光束偏转器10的电场的电场强度进行调控，实现经过可变折射率单元100的照明光束的偏转，并使入射到空间光调制器50的照明光束形成较亮区域和较暗区域，进而实现光转向型高动态投影***的调制。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域 的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (16)

  1. 一种投影***，其特征在于，包括：
    光源，用于出射照明光束；
    空间光调制器；以及
    光束偏转器，所述光束偏转器设置于照明光束的光路上，光束偏转器包括呈阵列排布的可变折射率单元，所述可变折射率单元的折射率能根据对其施加的电场强度而发生变化，所述光束偏转器根据待投影图像的图像信号控制施加在可变折射率单元上的电场，使得至少部分区域的可变折射率单元的折射率改变，经过该区域的照明光束发生偏转，以使入射到空间光调制器的照明光束形成较亮区域和较暗区域。
  2. 根据权利要求1所述的投影***，其特征在于，所述可变折射率单元由液晶材料制成。
  3. 根据权利要求2所述的投影***，其特征在于，所述可变折射率单元包括液晶盒，每个所述液晶盒具有第一入射面、第一出射面以及第一连接面，所述第一入射面与所述第一出射面以及所述第一连接面连接，所述多个液晶盒的所述第一入射面构成所述可变折射率单元的入光面。
  4. 根据权利要求3所述的投影***，其特征在于，所述液晶盒呈楔形，且所述第一连接面与所述第一入射面的夹角大于90°。
  5. 根据权利要求4所述的投影***，其特征在于，所述第一连接面与所述所述第一入射面的法线之间的夹角等于照明光束在所述液晶盒中的色散角。
  6. 根据权利要求4所述的投影***，其特征在于，第一连接面与所述第一入射面的夹角为120°-135°。
  7. 根据权利要求3所述的投影***，其特征在于，所述液晶盒由向列液晶构成，未施加电场时，所述液晶盒中液晶分子的光轴方向与所述入光面垂直。
  8. 根据权利要求3-7任一项所述的投影***，其特征在于，所述光束偏转器还包括具有固定折射率的固定折射率单元，所述可变折射率单元接收所述光源出射的照明光束，并由所述固定折射率单元出射至所述空间光调制器。
  9. 根据权利要求8所述的投影***，其特征在于，所述固定折射率单元包括并排设置的多个晶体结构，所述晶体结构具有第二入射面、第二出射面以及第二连接面，所述第二入射面与所述第二出射面以及所述第二连接面连接，每个所述第二入射面一一对应的与所述可变折射率单元中的一个液晶盒的第一出射面贴合。
  10. 根据权利要求9所述的投影***，其特征在于，每个所述晶体结构的第二连接面一一对应的与一个所述液晶盒的第一连接面平行。
  11. 根据权利要求9所述的投影***，其特征在于，每个所述晶体结构的第二连接面与相邻的所述液晶盒的第一连接面贴合。
  12. 根据权利要求1-7任一项所述的投影***，其特征在于，所述光束偏转器还包括第一电极以及第二电极，所述第一电极以及第二电极用于对所述可变折射率单元施加电场。
  13. 根据权利要求12所述的投影***，其特征在于，所述投影***还包括控制单元，所述控制单元与所述第一电极以及所述第二电极电性连接，以使控制单元根据待投影图像的各区域的亮度控制施加于呈阵列排布的可变折射率单元的各区域的电场强度。
  14. 根据权利要求1-7任一项所述的投影***，其特征在于，所述光源包括发光装置和起偏器，所述起偏器用于接收所述发光装置发出的光束，并出射线 偏振的所述照明光束。
  15. 根据权利要求1-7任一项所述的投影***，其特征在于，所述投影***还包括显示透镜，所述显示透镜位于经所述光束偏转器出射的照明光束的光路上。
  16. 根据权利要求15所述的投影***，其特征在于，所述显示透镜包括间隔设置的物镜和目镜，所述照明光束依次经所述物镜以及所述目镜透射至所述空间光调制器。
PCT/CN2020/142141 2020-03-19 2020-12-31 投影*** WO2021184925A1 (zh)

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JP2002372701A (ja) * 2001-06-13 2002-12-26 Ricoh Co Ltd 画像表示装置
JP2003262893A (ja) * 2002-03-11 2003-09-19 Ricoh Co Ltd 光路偏向装置及び画像表示装置
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