WO2019169870A1 - 屏幕和投影系统 - Google Patents

屏幕和投影系统 Download PDF

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Publication number
WO2019169870A1
WO2019169870A1 PCT/CN2018/110333 CN2018110333W WO2019169870A1 WO 2019169870 A1 WO2019169870 A1 WO 2019169870A1 CN 2018110333 W CN2018110333 W CN 2018110333W WO 2019169870 A1 WO2019169870 A1 WO 2019169870A1
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WO
WIPO (PCT)
Prior art keywords
layer
screen
light absorbing
light
medium layer
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Application number
PCT/CN2018/110333
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English (en)
French (fr)
Inventor
王霖
李屹
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深圳光峰科技股份有限公司
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Priority to US16/979,264 priority Critical patent/US11300869B2/en
Publication of WO2019169870A1 publication Critical patent/WO2019169870A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0273—Diffusing elements; Afocal elements characterized by the use
    • G02B5/0284—Diffusing elements; Afocal elements characterized by the use used in reflection
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/003—Light absorbing elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • G02B5/0273—Diffusing elements; Afocal elements characterized by the use
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/12—Reflex reflectors
    • G02B5/122—Reflex reflectors cube corner, trihedral or triple reflector type
    • G02B5/124—Reflex reflectors cube corner, trihedral or triple reflector type plural reflecting elements forming part of a unitary plate or sheet
    • 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
    • G03B21/28—Reflectors in projection beam
    • 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
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • 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
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface
    • G03B21/602—Lenticular screens

Definitions

  • the invention relates to the field of screens.
  • the present invention relates to a projection screen and projection system capable of high contrast and high brightness uniformity.
  • the ultra-short-throw projector has a very low throw ratio, and its appearance means that the minimum arrangement pitch between the projector and the projection screen is greatly shortened, so that the screen is blocked due to human walking or object placement during projection. Will no longer exist.
  • the projection system with ultra-short-throw projector is small in size, easy to install, the whole system is low in price, and can easily achieve a screen larger than 100 inches in a small projection distance.
  • the projection screen is an important factor affecting the effect of the projected image.
  • image contrast and brightness uniformity are two important parameters for evaluating the quality of the screen.
  • the contrast of the projector can reach thousands to one, but in an environment where the living room is used in a living room, the ambient light has a strong influence on the contrast of the screen.
  • a typical projection screen can reflect both the projection light of the projector and the ambient light, which causes a serious drop in contrast and greatly affects the viewing experience.
  • the ultra short throw projector has a very low throw ratio, there is a large difference in the incident angle of the projected light at different positions of the projection screen.
  • the Fresnel reflection on the surface of the screen is positively correlated with the angle of incidence of the projected ray.
  • the larger the angle of incidence the higher the Fresnel reflection.
  • Most of the light that occurs on the surface of the screen with Fresnel reflections cannot enter the viewer's field of view. Therefore, due to such uneven Fresnel reflection on the surface of the screen, the difference in luminance between the central area and the edge area of the screen surface is as high as 20% or more.
  • the present invention is intended to provide a screen having high brightness uniformity and a projection system including such a screen.
  • a screen according to a first embodiment of the present invention is provided. It is capable of reflecting the projected light from the projector into the field of view of the viewer, characterized in that the screen comprises at least a surface diffusion layer, a transmission light absorbing layer and a projection reflection layered in order from the incident side of the projection light. a layer, the projection reflection layer selectively reflects the projection light, and the transmission light absorption layer comprises particles of light absorbing material, and the distribution of the light absorbing material particles in the transmission light absorption layer is according to the projection light
  • the distribution of the Fresnel loss of the surface of the screen is set such that the transmittance of the transmission light absorbing layer is higher in a region where the Fresnel loss is larger.
  • the transmissive light absorbing layer may include a light absorbing medium layer and a transparent medium layer, wherein the light absorbing medium layer includes particles of light absorbing material distributed at a uniform density, thicknesses in different regions of the light absorbing medium layer and corresponding regions
  • the screen surface is inversely proportional to the Fresnel reflectance of the projected light, and the total thickness of the light absorbing medium layer and the transparent medium layer is a fixed value, and the refractive indices of the light absorbing medium layer and the transparent medium layer
  • the absolute value of the difference is not more than 0.2.
  • the thickness of the light absorbing medium layer gradually decreases from the center of the screen toward both sides and/or in the vertical direction, and the thickness of the light absorbing medium layer gradually decreases from above the screen toward the upper side of the screen.
  • the thickness variation of the light absorbing medium layer in the horizontal direction conforms to a linear distribution or a curved distribution or the thickness variation of the light absorbing medium layer in the vertical direction conforms to a linear distribution or a curved distribution.
  • the light absorbing medium layer contains a light absorbing dye, and a maximum thickness difference between thicknesses of different regions of the light absorbing medium layer decreases as the ratio of the light absorbing dye increases.
  • the transparent medium layer is a transparent glue layer.
  • the projection reflective layer may include a total reflection layer and a light absorption layer stacked in this order from the incident side of the projection light.
  • the light absorbing layer is capable of absorbing light.
  • the total reflection layer includes a microstructure layer including a plurality of microlens units having a first plane on a lower side and a second plane on an upper side, the first plane and The second planes intersect, the plurality of microstructure units constituting a sawtooth structure, and the projected light rays are continuously reflected totally in the first plane and the second plane.
  • the microstructured layer has a rotationally symmetric structure and the central axis of rotation is perpendicular to the plane of the screen and below the screen.
  • the projected reflective layer can be a Fresnel reflective layer.
  • a second embodiment in accordance with the present invention provides a projection system that includes a projector and a screen as described above.
  • a transmission light absorbing layer is disposed between the total reflection layer of the screen and the surface diffusion layer. Having light absorbing material particles in the light absorbing layer, the distribution of the light absorbing material particles in the light absorbing layer is set according to a distribution of Fresnel loss of the projected light on a surface of the screen, so that The higher the transmittance of the light absorbing layer in the region where the Nyer loss is, the higher the transmittance of the projected light on the screen surface can be compensated for.
  • the screen is provided with a total reflection layer that enables the projected light to continuously produce two total reflections and is capable of transmitting at least a portion of the ambient light. Therefore, the screen and projection system according to the present invention can have high contrast and high brightness uniformity.
  • FIG. 1 shows an example of an incident angle and a Fresnel reflectance of projected light rays of an ultra short throw projector at different positions of the screen.
  • Figure 2 shows a calculated distribution of Fresnel reflectance at various locations on the screen.
  • FIG. 3 is a side view showing a schematic structure of a screen according to an embodiment of the present invention.
  • FIG. 4 is a schematic view showing a rotationally symmetric structure of a microstructure unit of a total reflection layer of a screen according to an embodiment of the present invention
  • 5 and 6 are a plan view and a side view, respectively, showing a schematic structure of a screen according to an embodiment of the present invention
  • 7 and 8 are respectively a schematic view and a side view showing a thickness distribution of a transmission light absorbing layer of a screen in a horizontal direction according to an embodiment of the present invention
  • FIG. 9 is a schematic view showing an optical principle of a microstructure unit of a total reflection layer of a screen according to an embodiment of the present invention.
  • FIG. 10 is a schematic view showing a relationship between an inclination angle of a microstructure unit of a screen and an optical path according to an embodiment of the present invention
  • FIG. 11 is a simulation example showing an optical angle of a microstructure unit of a screen according to an embodiment of the present invention.
  • FIG. 12 is a schematic view showing a relationship of material refractive indices of a total reflection layer and an inner layer of a screen according to an embodiment of the present invention
  • FIG. 13 shows a schematic structure of a screen according to another embodiment of the present invention.
  • screens used in the field of projection generally include a laminated structure of two layers of a surface diffusion layer and a projection reflection layer.
  • the surface diffusion layer is located on the incident side of the projected light.
  • the projected light passes through the surface diffusion layer and is incident on the projection reflection layer, and the projection reflection layer selectively reflects the incident light.
  • the projected light reflected by the projected reflective layer passes through the surface diffusion layer again and then exits the screen and enters the viewer's field of view.
  • the incident side of the projected light is also referred to as the outer side of the screen (ie, facing the viewer side)
  • the side of the light absorbing layer is referred to as the inner side of the screen (ie, facing away from the viewer side).
  • FIG. 1 shows the variation of the incident angle of incident light and the Fresnel reflection of the screen surface at different locations of the screen and their correlation.
  • the incident light rays as shown in a of FIG. 1 are respectively incident at nine different positions on the screen shown in b of FIG. 1, the incident angle of the incident light rays at different positions and the Fresnel at the position
  • the reflectance is as shown in c of Fig. 1. As can be seen from c of Figure 1, the smaller the angle of incidence, the lower the Fresnel reflectivity.
  • Fresnel reflection occurs when light is incident from the air to the surface of the medium at an angle.
  • the reflectances of the horizontally polarized light and the vertically polarized light are R // and R ⁇ :
  • ⁇ i and ⁇ t are the incident angle and the refraction angle of the incident ray 31, respectively.
  • the reflectance of the surface is the average of the horizontal reflectance and the vertical reflectance.
  • the angle of incidence of the projected light from the projector to the surface of the screen can be calculated.
  • the Fresnel reflectance f(x, y) at each point of the screen can be theoretically calculated, where (x, y) is the position coordinate of the screen surface.
  • the Fresnel reflection profile of the projected ray of the ultra-short-throw projector thus calculated on the screen is illustrated in FIG. 2, where H represents the horizontal coordinate of the screen and V represents the vertical coordinate of the screen.
  • the Fresnel reflection of the screen appears as a 3-dimensional distribution function.
  • the Fresnel reflection distribution is low in the middle and low on both sides, and is symmetrical with respect to the central axis P1P2 of the screen.
  • the Fresnel reflection distribution gradually increases from the bottom to the top.
  • the closer the screen is to the position of the projector the smaller the angle of incidence, the lower the Fresnel reflectivity and the lower the Fresnel loss. The lower the Fresnel loss, the brighter the screen.
  • the screen according to the present invention is further provided with a transmission light absorbing layer between the surface diffusion layer and the projection reflection layer.
  • the transmission light absorbing layer is made of a transparent organic polymer material and is doped with particles of light absorbing material such as carbon black, carbon nanoparticles or the like. According to the plane distribution of the Fresnel loss of the projected light on the screen surface, the doping distribution of the light absorbing material in the transmission light absorbing layer is correspondingly arranged, so that the larger the Fresnel loss of a certain area of the screen, the transmission light absorbing layer is The transmittance of the portion in the region is higher.
  • the transmittance distribution of the transmission absorbing layer on the screen plane is positively correlated with the Fresnel loss distribution of the screen surface.
  • a transmissive light absorbing layer By providing such a transmissive light absorbing layer, light incident at different positions on the plane of the screen is absorbed to a small extent in the process of transmitting through the light absorbing layer to achieve uneven Fresnel loss on the screen surface.
  • the compensation of the distribution so as to achieve a uniform brightness of the screen display image, improve the brightness uniformity of the screen.
  • FIG. 3 is a schematic structural view showing a screen according to an embodiment of the present invention.
  • the screen according to the present invention includes a light absorbing layer 11, a total reflection layer 12, a transmission light absorbing layer 13, and a surface diffusion layer 14, which are sequentially stacked.
  • the light absorbing layer 11 is a black light absorbing layer capable of sufficiently absorbing light incident thereon.
  • the total reflection layer 12 includes a transparent substrate layer 120, a microstructure layer 121, and an inner layer 122 which are laminated in this order from the incident side of the projected light.
  • the transparent substrate layer 120 can be formed, for example, of a transparent material such as PET, PC, or PMMA.
  • the microstructure layer 121 is disposed inside the transparent substrate layer 120 (ie, on the side opposite to the incident side of the projected light).
  • the inner layer 122 is formed on the side of the microstructure layer 121 that is in contact with the light absorbing layer 11, and is in contact with the light absorbing layer 11.
  • the material forming the inner layer 122 has a lower refractive index than the material forming the microstructure layer 121.
  • the microstructure layer 121 is provided with a plurality of microstructure units.
  • Each microstructure unit can be formed as a total reflection prism.
  • the microstructure unit shown in FIG. 3 has a triangular cross-sectional structure, and in addition, the microstructure unit may have a cross-sectional structure of other shapes such as a trapezoid.
  • Each microstructure unit includes two inclined intersecting planes 124 and 125, wherein the inclined plane 124 on the lower side corresponds to the first plane in the present invention, and the inclined plane 125 on the upper side corresponds to the second in the present invention. flat.
  • the tilt angles of the two inclined planes are specifically designed (described in detail later) such that at least a majority of the projected ray 31 incident from below the screen occurs twice in total at two inclined planes, eventually becoming reflected to view
  • the outgoing ray 33 in the field of view of the screen, and most of the ambient stray light 32 from the top of the screen is absorbed by the absorbing layer 11 through the total reflection layer 12 because the angle cannot satisfy the total reflection condition in the total reflection layer. absorb.
  • the two intersecting planes 124 and 125 of the microstructure unit can also be considered as the interface between the two different material layers of the microstructure layer 121 and the inner layer 122, wherein the microstructure layer 121 is the first material layer and the inner layer 122 It is a second material layer.
  • the plurality of microstructure elements of the microstructure layer 121 are periodically arranged to form a zigzag structure; the inner layer 122 thus also has a corresponding zigzag structure.
  • a plurality of microstructure units may also be arranged non-periodically as long as a zigzag structure can be formed in the section shown in FIG.
  • the microstructure layer 121 having a microstructure array can be formed by processing a roll coating resin and a UV curing process on the inner side of the transparent substrate layer 120.
  • the microstructure layer 121 is made of a resin material, and the resin is usually an epoxy resin adhesive, an acrylate adhesive, a polyester adhesive, a polyurethane adhesive, or a polyimide adhesive.
  • the transparent substrate layer 120 and the microstructure layer 121 are preferably formed from the same substrate.
  • PET is used as the material of the transparent substrate layer 120
  • a microstructure array of a prism is formed on the inner side of the PET substrate by a roll coating resin and a UV curing process as the microstructure layer 121.
  • the transparent substrate layer 120 and the microstructure layer 121 can also be made of different materials.
  • the inner layer 122 may be, for example, an air layer, a quartz layer, a glass layer, or the like.
  • a transmission light absorbing layer 13 is provided on the outer side of the total reflection layer 12.
  • the transmission light absorbing layer 13 is made of a transparent organic polymer material and is doped with particles of light absorbing material such as carbon black, carbon nanoparticles or the like.
  • the doping distribution of the light absorbing material in the transmission light absorbing layer 13 is controlled such that the larger the Fresnel loss of a certain area of the screen, the transmission light absorbing layer 13 is The transmittance of the portion in the region is higher. In other words, the transmittance distribution of the transmission light absorbing layer 13 on the screen plane is positively correlated with the Fresnel loss distribution of the screen surface.
  • the surface diffusion layer 14 is disposed at the outermost side of the screen.
  • the divergence angle of the outgoing light emitted by the total reflection of the total reflection layer is generally small, and the surface diffusion layer 14 can increase the divergence angle of the emitted light and increase the visible range of the projected picture.
  • only one layer of the surface diffusion layer 14 is provided on the outer side of the transmission light absorbing layer 13.
  • a multilayer surface diffusion layer can be formed by laminating a plurality of layers of commercially available optical scattering films.
  • the projected light 31 from the projector below the screen enters the transmitted light absorbing layer 13 through the surface diffusion layer 14.
  • the transmission light absorbing layer 13 the projection light rays 31 incident at different regions of the screen are absorbed to different extents and then incident on the total reflection layer 12.
  • the projected ray 31 is continuously totally reflected twice on the inclined planes 124 and 125 in the total reflection layer 12, passes through the transmission absorbing layer 13 and the surface diffusion layer 14, and finally exits into the field of view of the viewer, becoming the exit of the screen.
  • the ambient stray light 32 is mainly from the ceiling light in the room.
  • the overhead light is away from the axis of rotation of the rotationally symmetric structure of the microstructure unit of the screen and the angle of incidence of the ambient stray light 32 is much smaller than the angle of incidence of the projected light. Therefore, the ambient stray light 32 cannot satisfy the condition that total reflection occurs at both the interfaces 124 and 125, and most of them pass through the microstructure unit and are absorbed by the light absorbing layer 11.
  • the microstructure unit of the microstructure layer 121 has a rotationally symmetrical array arrangement on the screen plane.
  • the center of rotation (optical center) of the rotationally symmetric array arrangement is perpendicular to the plane of the screen and below the screen.
  • the projector 20 (see Fig. 5) is disposed on the central axis of rotation.
  • the microstructure layer 121 is a row of rotationally symmetric prisms formed on the surface of the transparent substrate layer 120.
  • a protective layer may be additionally provided on the outermost side of the screen according to the present invention to prevent scratching or chemical corrosion.
  • the protective layer may be a polyimide (PI) film, a polyester (PET) film, or a polynaphthyl ester.
  • PEN one or more of a film, a polyvinyl chloride (PVC) film, a polycarbonate (PC) film or a liquid crystal polymer (LCP) film, a glass plate, a PC board, a cloth, etc., such as a glass plate Naphthyl ester (PEN) film.
  • PVC polyvinyl chloride
  • PC polycarbonate
  • LCP liquid crystal polymer
  • PEN glass plate Naphthyl ester
  • other auxiliary function layers can also be set according to the design needs.
  • the screen according to the present invention enables the screen to have high luminance uniformity and high contrast by utilizing the in-plane non-uniform light absorption characteristics of the transmission light absorbing layer 13 and the angle selective reflection characteristics of the total reflection layer 12.
  • a simple implementation is to make the light absorbing medium layer having the uniform density of the light absorbing material particles in a direction perpendicular to the plane of the screen (ie, The thickness of the screen has a different thickness.
  • T is the transmittance of the light absorbing material
  • ⁇ is the absorption coefficient of the light absorbing material
  • L is the optical path of the light in the light absorbing material.
  • Fresnel losses in different areas of the screen surface can be fitted by theoretical calculations or actual tests. According to the Fresnel loss of different regions of the calculated or fitted screen surface, combined with the reflectivity of the screen itself, it is possible to calculate the light absorbing material required to compensate for the surface Fresnel loss of a certain area of the screen.
  • the transmission light absorbing layer 13 in FIGS. 5 and 6 includes a light absorbing medium layer 131 and a transparent dielectric layer 132.
  • the formula (1) in the horizontal direction of the screen, the closer to the center of the screen, the smaller the Fresnel loss. It can be calculated from the formula (3) that, as shown in Fig. 5, the thickness of the light absorbing medium layer 131 gradually decreases from the center to the both sides of the screen in the horizontal direction. Thus, in the horizontal direction, the light absorbing property of the light absorbing medium layer 131 gradually decreases from the center to both sides.
  • the Fresnel loss is smaller as it is closer to the lower side of the screen in the vertical direction of the screen. It can be calculated from the formula (3) that, as shown in Fig. 6, in the vertical direction, the thickness of the light absorbing medium layer 131 gradually decreases from the lower side of the screen to the upper side of the screen. Thus, in the vertical direction, the light absorbing property of the light absorbing medium layer 131 gradually decreases from the bottom to the top.
  • the screen according to an embodiment of the present invention has both thickness variation features in the horizontal and vertical directions as shown in FIGS. 5 and 6.
  • the thickness of the light absorbing medium layer 131 of the screen gradually decreases from the center to the both sides of the screen in the horizontal direction, the thickness gradually decreases from the lower side of the screen to the upper side of the screen.
  • the screen in accordance with the present invention may optionally have thickness variation features in the horizontal or vertical direction as shown in FIG. 5 or FIG. 6 in some embodiments. That is, the thickness of the light absorbing medium layer 131 of the screen gradually decreases from the center to the both sides of the screen in the horizontal direction, or the thickness of the light absorbing medium layer 131 of the screen gradually decreases from the lower side of the screen to the upper side of the screen.
  • the thickness of different regions of the light absorbing medium layer 131 can be selectively inversely proportional to the Fresnel reflectance (ie, Fresnel reflection loss) of the screen surface of the region to the projector light, thereby non-uniform to the screen surface.
  • the Fresnel loss is compensated.
  • the thickness variation of the light absorbing medium layer 131 may conform to a straight line distribution or a curve distribution. Further, it should be understood that although the thickness variation of the light absorbing medium layer 131 is shown as a curved distribution in the vertical direction of the screen in FIG. 6, it may be a straight line distribution.
  • the selected material may be a transparent organic polymer material such as PC or PET, and a light-absorbing dye (carbon black, carbon nanoparticles, etc.) is added therein to form a uniformly distributed light absorbing medium.
  • the absorption coefficient ⁇ of the membrane depends on the ratio of the light-absorbing dye per unit volume.
  • the ratio of the light absorbing dye is high, and the maximum thickness difference required for the light absorbing medium layer 131 is small; when the ratio of the light absorbing dye is low, the maximum required for the light absorbing medium layer 131 is required.
  • the difference in thickness is large.
  • the maximum thickness difference here refers to the maximum difference between the thicknesses of different regions of the light absorbing medium layer. In other words, the maximum thickness difference required for the light absorbing medium layer 131 decreases as the ratio of the light absorbing dye increases.
  • a previously prepared uniform thickness of the absorbent material can be heated to a softening temperature and imprinted with a mold having a high degree of distribution on the surface to obtain a film having a given thickness distribution.
  • a UV-glue coating embossing method can also be used to quickly obtain light absorbing materials having different thickness distributions.
  • the transmission light absorbing layer 13 In order to allow the transmission light absorbing layer 13 to absorb light to different extents according to the thickness distribution of the light absorbing medium layer 131 without changing the traveling direction of the light, it is also necessary to provide the transparent dielectric layer 132 on the thickness variation surface of the light absorbing medium layer 131 so as to transmit
  • the light absorbing layer 13 has a uniform thickness as a whole.
  • the transparent dielectric layer 132 and the light absorbing dielectric layer 131 should have substantially the same refractive index to reduce the refraction of the interlayer interface.
  • the absolute value of the refractive index difference between the transparent dielectric layer 132 and the light absorbing medium layer 131 should be no more than 0.2.
  • a transparent glue may be applied to the non-vertical surface of the light absorbing medium layer 131 by a UV curing UV glue process to form a transparent dielectric layer 132 that matches the shape of the light absorbing medium layer 131, and the total thickness of the transmission light absorbing layer 13 is made. Is a fixed value.
  • Figure 9 illustrates the optical principles of a total reflection microstructure unit of a screen in accordance with an embodiment of the present invention.
  • the optical path optimization of the projected light by the surface diffusion layer 14 is not considered in the discussion below.
  • the refractive index of the microstructure layer 121 is n 1 and the refractive index of the inner layer 122 is n 2 , and the first plane 124 and the second plane 125 of the microstructure unit are aligned with the screen plane (ie, the vertical direction).
  • the angles are ⁇ 1 and ⁇ 2 (in degrees, the same below).
  • the angle between the incident and reflected rays and the horizontal direction are ⁇ and ⁇ (in degrees, the same below).
  • ⁇ when the reflected light is emitted horizontally, ⁇ is obviously 0 degrees, and is set: when the reflected light is below the horizontal line (ie, biased to the ground), ⁇ is a negative value, when the reflected light is above the horizontal line (ie, biased toward the ceiling) ⁇ is a positive value.
  • the incident light from the projector In order to cause the incident light from the projector to be totally reflected twice on two inclined surfaces and then emitted toward the viewer's eyes, according to the geometrical optical principle and the optical total reflection condition, the following formulas (4) to (6) must be satisfied. ):
  • the angle between the first plane 124 and the second plane 125 of the microstructure unit of the screen according to the present invention must be obtuse.
  • FIG. 10 An ideal optical path condition is shown in a of Fig. 10, wherein the incident light ray Vin is incident on the microstructured layer 121 along the plane parallel to the screen plane through the total reflection of the intermediate ray Vmid of a slope of the microstructure unit. In the direction of travel, Vmid passes through the total reflection of the other slope of the microstructure unit and becomes the exiting light Vout that is horizontally emitted toward the viewer.
  • Equation (9) shows that ⁇ 1 ⁇ 45 degrees, that is, ⁇ 1 ⁇ ⁇ 2 .
  • the incident light ray Vin is totally reflected by the first slope of the microstructure unit to generate intermediate light Vmid, but the traveling direction of Vmid is not parallel to the plane of the screen, but is biased toward the side facing away from the viewer. (At this time, ⁇ is a negative value). Therefore, the second slope of the microstructure unit cannot be fully utilized.
  • the screen according to the present invention has a rotationally symmetrical structure and includes a plurality of microstructure units.
  • the angular design of each microstructure unit can be the same or different.
  • Figure 11 illustrates a simulated example of the optical angle of a microstructure unit of a screen in accordance with the present invention.
  • ⁇ 1 of the microstructure unit gradually decreases as it approaches the upper side of the screen, and ⁇ 1 ⁇ ⁇ 2 , thus satisfying the above formula (9).
  • the focus of the screen is no longer at infinity.
  • the value of ⁇ 1 of the microstructure unit of the screen is continuously decreased and the value of ⁇ 2 is continuously increased.
  • the microstructure layer 121 of the screen according to the present invention is generally made of a transparent resin material having a refractive index in the range of 1.3 to 1.7.
  • the microstructure layer 121 can also be made using other materials having similar refractive indices.
  • Figure 12 shows the effect of the different refractive indices n 2 of the inner layer 122 on the total reflection area of the incident ray of the microstructure unit.
  • the incident ray V can be expressed as (V x , V y , V z ), where the z-axis is perpendicular to the screen and the X, Y-axis is parallel to the screen.
  • the total reflection area of the incident ray depends on the range of values of V x and V y .
  • V z meets:
  • the components (V x , V y ) of the incident ray satisfying the total reflection condition can be obtained according to the above formulas (5) and (6).
  • the range of values varies with the refractive index n 2 of the inner layer 122.
  • n 2 increases, the area of incident light rays that satisfy the total reflection of both slopes of the microstructure unit is continuously reduced.
  • n 1 and n 2 satisfy:
  • the inner layer 122 is preferably an air layer in the case where the above conditions are satisfied.
  • the projected reflective layer is composed of a total reflection layer and a light absorbing layer.
  • a commonly used reflective layer such as a Fresnel reflective layer known in the art can also be used as the projection reflective layer.
  • Fig. 13 is a diagram showing the structure of a screen in this case. As can be seen from Fig. 13, the structure, function and characteristics of the surface diffusion layer and the transmission light absorbing layer of the screen in this example are the same as those described in the above embodiments except that the Fresnel reflection layer 15 is employed as the projection reflection layer. .

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Abstract

一种能够将来自投影机的投影光线反射至观看者的视场范围内的屏幕，至少包括从投影光线的入射侧依次层叠设置的表面扩散层（14）、透射吸光层（13）和投影反射层（12）。投影反射层（12）选择性地反射投影光线。透射吸光层（13）中包含吸光材料颗粒，吸光材料颗粒在透射吸光层（13）中的分布是根据投影光线在屏幕的表面的菲涅尔损耗的分布而设定的，以使在菲涅尔损耗越大的区域中透射吸光层（13）的透光率越高。还公开了包含这种屏幕的投影系统。这种屏幕和投影系统具有高对比度和高亮度均匀性。

Description

屏幕和投影系统 技术领域
本发明涉及屏幕领域。具体地，本发明涉及一种能够具有高对比度和高亮度均匀性的投影屏幕和投影系统。
背景技术
近年来，超短焦投影机越来越受到人们的关注。超短焦投影机具有很低的投射比，它的出现意味着大大缩短了投影机与投影屏幕之间的最小布置间距，使得投影过程中由于人的走动或物体的摆放而挡住画面的情况将不复存在。此外，采用超短焦投影机的投影系统尺寸小，便于安装，整套系统价格低，并且能够在较小的投影距离内轻松实现大于100寸的画面。
在这样的投影系统中，除了投影机之外，投影屏幕是影响投影图像效果的重要因素。在投影屏幕的投影显示中，图像对比度和亮度均匀性是评价屏幕画面质量的两个重要参数。通常，投影机的对比度可以达到数千比一，但是在客厅等实际家庭使用的环境中，环境光对屏幕画面的对比度会产生较强的影响。一般的投影屏幕既能反射投影机的投影光线也能反射环境光，使得对比度严重下降，极大地影响观看体验。此外，由于超短焦投影机具有很低的投射比，因此投影光线在投影屏幕的不同位置处的入射角度存在着较大的差异。屏幕表面的菲涅尔反射跟投影光线的入射角度正相关，入射角度越大，菲涅尔反射越高。在屏幕表面发生菲涅尔反射的光线大部分都无法进入到观众的视场中。因此，由于屏幕表面这种不均匀的菲涅尔反射导致了屏幕表面中心区域和边缘区域的亮度差高达20％以上。
为了提高屏幕的亮度均匀性，专利文献CN 104516182B中提出了在投影机的光学系统中加入吸收率渐变的偏振片阵列，从而形成中间暗、边缘亮的投影分布来补偿投影屏幕的亮度不均匀性的技术方案。此外，专利文献CN1723699A中提出了一种用两台投影机来补偿亮度不均匀性的方法。然而，以上两种方法都不涉及屏幕本身的改善，而是通过改变投影机的设计来补偿亮度均匀性。
因此，需要能够提高投影画面的亮度均匀性的屏幕。
发明内容
针对上述问题，本发明期望提供一种具有高亮度均匀性的屏幕和包含这样的屏幕的投影系统。
根据本发明的第一实施例提供了一种屏幕。其能够将来自投影机的投影光线反射至观看者的视场范围内，其特征在于，所述屏幕至少包括从所述投影光线的入射侧依次层叠设置的表面扩散层、透射吸光层和投影反射层，所述投影反射层选择性地反射所述投影光线，并且所述透射吸光层中包含吸光材料颗粒，所述吸光材料颗粒在所述透射吸光层中的分布是根据所述投影光线在所述屏幕的表面的菲涅尔损耗的分布而设定的，以使在菲涅尔损耗越大的区域中所述透射吸光层的透光率越高。
优选地，所述透射吸光层可以包括吸光介质层和透明介质层，所述吸光介质层中包含以均匀密度分布的吸光材料颗粒，所述吸光介质层的不同区域内的厚度与相应区域中的屏幕表面对所述投影光线的菲涅尔反射率成反比，并且所述吸光介质层和所述透明介质层的总厚度为固定值，且所述吸光介质层和所述透明介质层的折射率的差的绝对值不大于0.2。
优选地，在水平方向上，所述吸光介质层的厚度从屏幕中心向两侧逐渐减小和/或在垂直方向上，所述吸光介质层的厚度从屏幕下方向屏幕上方逐渐减小。
优选地，所述吸光介质层的在水平方向上的厚度变化符合直线分布或曲线分布或所述吸光介质层的在垂直方向上的厚度变化符合直线分布或曲线分布。
优选地，所述吸光介质层含有吸光染料，并且所述吸光介质层的不同区域的厚度之间的最大厚度差随着所述吸光染料的配比的增大而减小。
优选地，所述透明介质层是透明胶水层。
在一些实施例中，所述投影反射层可以包括从所述投影光线的入射侧依次层叠的全反射层和吸光层。所述吸光层能够吸收光。所述全反射层包括微结构层，所述微结构层包含多个微透镜单元，所述微结构单元具有位于下侧的第一平面和位于上侧的第二平面，所述第一平面和所述 第二平面相交，所述多个微结构单元构成锯齿结构，所述投影光线能够连续在所述第一平面和所述第二平面发生全反射。优选地，所述微结构层具有旋转对称结构，并且旋转中心轴线垂直于所述屏幕的平面且位于所述屏幕的下方。
可替代地，在一些实施例中，所述投影反射层可以是菲涅尔反射层。
根据本发明的第二实施例提供了一种投影系统，所述投影系统包括投影机和如上所述的屏幕。
在本发明中，屏幕的全反射层与表面扩散层之间设置有透射吸光层。透射吸光层中包含吸光材料颗粒，所述吸光材料颗粒在所述透射吸光层中的分布是根据所述投影光线在所述屏幕的表面的菲涅尔损耗的分布而设定的，使得在菲涅尔损耗越大的区域中所述透射吸光层的透光率就越高，由此能够对投影光线在屏幕表面的菲涅尔损耗进行补偿。另外，优选地，屏幕设置有能够使投影光线连续产生两次全反射并且能够透过至少部分环境光的全反射层。因此，根据本发明的屏幕和投影系统能够具有高对比度和高亮度均匀性。
应当理解，本发明的有益效果不限于上述效果，而可以是本文中说明的任何有益效果。
附图说明
图1示出了超短焦投影机的投影光线在屏幕的不同位置处的入射角和菲涅尔反射率的示例。
图2示出了计算出的屏幕各位置处的菲涅尔反射率的分布图。
图3是示出了根据本发明实施例的屏幕的示意性结构的侧视图；
图4是示出了根据本发明实施例的屏幕的全反射层的微结构单元的旋转对称结构的示意图；
图5和图6分别是示出了根据本发明实施例的屏幕的示意性结构的俯视图和侧视图；
图7和图8分别是示出了根据本发明实施例的屏幕的透射吸光层在水平方向上的厚度分布的示意图和侧视图；
图9是示出了根据本发明实施例的屏幕的全反射层的微结构单元的光学原理的示意图；
图10是示出了根据本发明实施例的屏幕的微结构单元的倾斜角度与光路之间的关系的示意图；
图11是示出了根据本发明实施例的屏幕的微结构单元的光学角度的模拟实例；
图12是示出了根据本发明实施例的屏幕的全反射层和内侧层的材料折射率的关系的示意图；
图13示出了根据本发明另一实施例的屏幕的示意性结构。
具体实施方式
下面，将参照附图详细说明根据本发明的各具体实施例。需要强调的是，附图中的所有尺寸仅是示意性的并且不一定是按照真实比例图示的，因而不具有限定性。例如，应当理解，图示出的投影屏幕的多层结构中各层的厚度、形状、大小等并不是按照实际的尺寸和比例示出的，仅是为了图示方便。
一、根据本发明的屏幕的概述
通常，用于投影领域的屏幕一般包括表面扩散层和投影反射层这两层的层叠结构。其中，表面扩散层位于投影光线的入射侧。投影光线经过表面扩散层后入射至投影反射层，投影反射层对入射的光线进行选择性地反射。经投影反射层反射后的投影光再次经过表面扩散层，然后从屏幕出射，进入观看者的视场内。在下文中，也将投影光线的入射侧称为屏幕的外侧(即，面向观众一侧)，将吸光层侧称为屏幕的内侧(即，背向观众一侧)。
然而，当光以一定角度从空气入射到介质表面的时候会发生菲涅尔反射。来自于投影仪，尤其是超短焦投影仪的投影光线在投影屏幕的不同位置处的入射角度存在着较大的差异。图1示出了在屏幕的不同位置处，入射光的入射角度和屏幕表面的菲涅尔反射的变化及其关联性。当如图1的a中所示的入射光线分别入射至图1的b中所示的屏幕上的9个不同位置处时，入射光线在不同位置处的入射角和该位置处的菲涅尔反射率如图1的c中所示。由图1的c可以看出，入射角越小，菲尼尔反射率越低。
具体地，当光以一定角度从空气入射到介质表面的时候会发生菲涅 尔反射，具体地，水平偏振光和垂直偏振光的反射率分别为R //和R ⊥：
Figure PCTCN2018110333-appb-000001
其中θi和θt分别为入射光线31的入射角和折射角。
对于一般没有固定偏振态的投影光线，表面的反射率为水平反射率和垂直反射率的平均值。根据投影机和屏幕的相对位置，可以计算出投影机的投影光线到屏幕表面的入射角。根据上述公式(1)，可以在理论上计算出屏幕每一点处的菲涅尔反射率f(x,y)，其中，(x,y)为屏幕表面的位置坐标。图2中图示了这样计算出的超短焦投影机的投影光线在屏幕上的菲涅尔反射分布图，其中，H表示屏幕的水平坐标，V表示屏幕的垂直坐标。由图2可以看出，屏幕的菲涅尔反射呈现为一个3维分布函数。在水平方向上，菲涅尔反射分布中间低两侧高，并且相对于屏幕的中轴线P1P2对称。在垂直方向上，菲涅尔反射分布从下往上逐渐增大。大体上，屏幕越靠近投影机的位置，入射角越小，菲涅尔反射率越低，菲涅尔损耗也就越低。菲涅尔损耗越低，则屏幕也就越亮。
因此，为了补偿表面菲涅尔损耗对屏幕亮度均匀性的影响，根据本发明的屏幕在表面扩散层与投影反射层之间还设置有透射吸光层。透射吸光层是由透明的有机高分子材料制成的，并且其中掺杂有吸光材料颗粒，例如炭黑、碳纳米颗粒等。根据投影光线在屏幕表面的菲涅尔损耗的平面分布，对吸光材料在透射吸光层内的掺杂分布进行相应的布置，使得屏幕的某区域的菲涅尔损耗越大，则透射吸光层在该区域内的部分的透光率就越高。换言之，透射吸光层在屏幕平面上的透光率分布与屏幕表面的菲涅尔损耗分布正相关。通过设置这样的透射吸光层，使得在屏幕平面的不同位置处入射的光线在透过透射吸光层的过程中被不同程度地吸收一小部分，以实现对屏幕表面的不均匀的菲涅尔损耗分布的补偿，从而实现亮度均匀的屏幕显示图像，提高屏幕的亮度均匀性。
一、屏幕的多层结构的具体实施例
图3是示出了根据本发明实施例的屏幕的结构示意图。如图3中所示，根据本发明的屏幕包括依次层叠设置的吸光层11、全反射层12、透射吸光层13和表面扩散层14。
图3示出的是根据本发明实施例的屏幕的层叠结构的截面示意图。吸光层11是能够充分吸收入射至其上的光的黑色吸光层。所图3所示，全反射层12包括从投影光线的入射侧依次层叠设置的透明基材层120、微结构层121和内侧层122。透明基材层120例如可以由PET、PC或PMMA等透明材料形成。微结构层121设置在透明基材层120的内侧(即，与投影光线入射侧相反的一侧)。内侧层122形成在微结构层121的与吸光层11接触的一侧，并且与吸光层11相接触。形成内侧层122的材料的折射率低于形成微结构层121的材料的折射率。
微结构层121设置有多个微结构单元。每个微结构单元可以被形成为全反射棱镜。图3中示出的微结构单元具有三角形的横截面结构，此外，微结构单元也可具有例如梯形等其它形状的横截面结构。每个微结构单元包含两个倾斜的相交平面124和125，其中，位于下侧的倾斜平面124对应于本发明中的第一平面，位于上侧的倾斜平面125对应于本发明中的第二平面。这两个倾斜平面的倾斜角度经过特定设计(稍后将详细说明)，使得从屏幕下方入射的至少大部分投影光线31在两个倾斜平面处连续发生两次全反射，最终成为被反射至观看者的视场范围内的出射光线33，而来自于屏幕上方的环境杂光32的绝大部分因角度无法满足全反射层中的全反射条件而透过所述全反射层12被吸光层11吸收。微结构单元的两个相交平面124和125也可以看做是微结构层121与内侧层122这两种不同的材料层之间的界面，其中微结构层121为第一材料层，内侧层122为第二材料层。在图3所述的横截面中，微结构层121的多个微结构单元周期性排列，形成锯齿状结构；内侧层122也因此具有对应的锯齿状结构。但是，应当理解的是，多个微结构单元也可以非周期性排列，只要在图3中所示的截面中能够形成锯齿状结构即可。
例如，可以通过在透明基材层120的内侧用对卷涂布树脂和UV固化工艺加工形成具有微结构阵列的微结构层121。所述微结构层121采用树脂材料，所述树脂通常为环氧树脂胶系、丙烯酸酯胶系、聚酯胶系、聚氨酯胶系或聚酰亚胺胶系等。优选地，透明基材层120和微结构层121优选由同一块基材形成。例如，使用PET作为透明基材层120的材料，在PET基材的内侧采用对卷涂布树脂和UV固化工艺加工形成棱镜的微结构阵列，作为微结构层121。当然，透明基材层120和微结构层121 也可以由不同的材料制成。内侧层122可以是例如空气层、石英层或玻璃层等。
如图3所示，在全反射层12的外侧设置了透射吸光层13。透射吸光层13是由透明的有机高分子材料制成的，并且其中掺杂有吸光材料颗粒，例如炭黑、碳纳米颗粒等。根据投影光线31在屏幕表面的菲涅尔损耗的平面分布，控制吸光材料在透射吸光层13内的掺杂分布，使得屏幕的某区域的菲涅尔损耗越大，则透射吸光层13在该区域内的部分的透光率就越高。换言之，透射吸光层13在屏幕平面上的透光率分布与屏幕表面的菲涅尔损耗分布正相关。通过设置这样的透射吸光层13，使得在屏幕平面的不同位置处入射的光线在透过透射吸光层的过程中被不同程度地吸收一小部分，以实现对屏幕表面的不均匀的菲涅尔损耗分布的补偿，从而实现亮度均匀的屏幕显示图像，提高屏幕的亮度均匀性。
表面扩散层14设置在屏幕的最外侧。经过全反射层的全反射后而出射的出射光线的发散角一般都很小，表面扩散层14能够增大出射光线的发散角，增加投影画面的可视范围。在图3所示的示例中，透射吸光层13的外侧仅设置有一层表面扩散层14。然而，也可以设置有多层表面扩散层。例如，可以通过层叠多层商业化光学散射薄膜形成多层表面扩散层。
如图3所示，来自屏幕下方的投影机的投影光线31透过表面扩散层14进入透射吸光层13。在透射吸光层13中，在屏幕的不同区域入射的投影光线31被不同程度地吸收，然后入射至全反射层12。投影光线31在全反射层12中在倾斜平面124和125上连续发生两次全反射，再经过透射吸光层13和表面扩散层14，最终出射至观看者的视场范围内，成为屏幕的出射光线33。环境杂光32主要来自于房间中的顶灯。在绝大部分情况下，顶灯远离屏幕的微结构单元的旋转对称结构的旋转轴线并且环境杂光32的入射角远小于投影光线的入射角度。因此，环境杂光32无法满足在界面124和125均发生全反射的条件，绝大部分透过了微结构单元而被吸光层11吸收。
在全反射层12中，如图4所示，微结构层121的微结构单元在屏幕平面上具有旋转对称的阵列排布结构。该旋转对称的阵列排布结构的旋转中心(光学中心)轴线垂直于屏幕平面且位于屏幕的下方。优选地， 投影机20(见图5)布置在该旋转中心轴线上。因此，在微结构层121的每一个微结构单元中，微结构层121是在透明基材层120的表面上形成的一排旋转对称的棱镜。
进一步的，在根据本发明的屏幕的最外侧还可以添加设置保护层以防止刮伤或者化学腐蚀，该保护层可以是聚酰亚胺(PI)膜、聚酯(PET)膜、聚萘酯(PEN)膜、聚氯乙烯(PVC)膜、聚碳酸酯(PC)膜或液晶聚合物(LCP)膜、玻璃板、PC板、布料等的一种或几种，比如玻璃板上的聚萘酯(PEN)膜。当然，还可以根据设计需要设置其它的辅助功能层。
如上所述，根据本发明的屏幕通过利用透射吸光层13的平面内非均匀吸光特性和全反射层12的角度选择性反射特性，使得屏幕能够具有高亮度均匀性和高对比度。
二、透射吸光层的具体示例
如上所述，为了对屏幕表面的不均匀的菲涅尔反射进行补偿，需要设置具有非均匀吸光特性的透射吸光层13。
优选地，为了得到在屏幕平面内吸光特性非均匀分布的透射吸光层13，一种简单的实现方式是使具有均匀密度的吸光材料颗粒的吸光介质层在与屏幕平面垂直的方向上(即，屏幕厚度方向上)具有不同的厚度。
当光从吸光材料中穿过的时候，会有一部分的光被吸收,透光率满足关系：
T＝e -αL     (2)
其中，T为吸光材料的透过率；α为吸光材料的吸收系数；L为光线在吸光材料中的光程。
屏幕表面的不同区域的菲涅尔损耗可以通过理论计算或者实际测试拟合出来。根据计算或拟合出的屏幕表面的不同区域的菲涅尔损耗，再结合屏幕本身的反射率，进而可以计算出为了补偿屏幕的某区域的表面菲涅尔损耗而需要的吸光材料在该区域内的厚度。假设P 1(0,0)处的吸收材料厚度为L 0，P(x,y)处的吸收材料厚度为L(x,y),可以由以下公式推出理想中完全均匀的的吸收材料厚度分布满足：
Figure PCTCN2018110333-appb-000002
图5和图6分别是示出了根据本发明实施例的屏幕的示意性结构的俯视图和侧视图。图5和图6中的透射吸光层13包括吸光介质层131和透明介质层132。根据公式(1)可知，在屏幕的水平方向上，越靠近屏幕中心，菲涅尔损耗越小。由公式(3)可以计算出，如图5所示，吸光介质层131的厚度在水平方向上从屏幕的中心向两侧逐渐减小。这样，在水平方向上，吸光介质层131的吸光性能从中心至两侧逐渐降低。此外，根据公式(1)可知，在屏幕的垂直方向上，越靠近屏幕下方，菲涅尔损耗越小。由公式(3)可以计算出，如图6所示，在垂直方向上，吸光介质层131的厚度从屏幕下方至屏幕上方逐渐减小。这样，在垂直方向上，吸光介质层131的吸光性能从下至上逐渐降低。优选地，根据本发明实施例的屏幕同时具有如图5和图6所示的水平方向和垂直方向上的厚度变化特征。即，屏幕的吸光介质层131的厚度在水平方向上从屏幕的中心向两侧逐渐减小的同时，厚度从屏幕下方至屏幕上方逐渐减小。但应当理解的是，根据本发明的屏幕在一些实施例中可以选择性地具有图5或图6所示的水平方向或垂直方向上的厚度变化特征。即，屏幕的吸光介质层131的厚度在水平方向上从屏幕的中心向两侧逐渐减小，或者屏幕的吸光介质层131的厚度从屏幕下方至屏幕上方逐渐减小。总之，吸光介质层131的不同区域的厚度可以选择性地与该区域的屏幕表面对于投影机光线的菲涅尔反射率(即，菲涅尔反射损耗)成反比，从而对屏幕表面的非均匀的菲涅尔损耗进行补偿。
图7和图8示出了在水平方向上具有不均匀厚度分布的吸光介质层131的形状示例。如图所示，吸光介质层131的厚度变化可以符合直线分布，也可以是曲线分布。此外，应当理解的是，虽然在图6中示出了吸光介质层131的厚度变化在屏幕的垂直方向上符合曲线分布，但也可以是直线分布。
实现吸光介质层131的不同厚度分布的膜材加工方式有很多种，比如模具热压成型和UV胶水非均匀涂布和光固化方式等。选用的材料可以是PC、PET等透明有机高分子材料，并在其中加入吸光染料(炭黑，碳纳米颗粒等)，形成均匀分布的光吸收介质。膜材的吸收系数α取决于单位体积内吸光染料的配比。因此，为了实现相同的菲涅尔损耗补偿性能，吸光染料的配比高，则吸光介质层131所需的最大厚度差就小；吸 光染料的配比低，则吸光介质层131所需的最大厚度差就大。这里的最大厚度差是指吸光介质层不同区域的厚度之间的最大差值。换言之，吸光介质层131所需的最大厚度差随着吸光染料的配比的增大而减小。对于热压的方式，可以将预先制备好的均匀厚度的吸收材料加热到软化温度，在用表面具有高度分布的模具压印，得到具有给定厚度分布的膜材。在透明基材上，采用UV胶水涂布压印的方法，也可以快速得到具有不同厚度分布的吸光材料。
为了让透射吸光层13在根据吸光介质层131的厚度分布而不同程度地吸收光的同时不改变光的前进方向，还需要在吸光介质层131的厚度变化表面设置透明介质层132，以使透射吸光层13整体上具有均一的厚度。透明介质层132与吸光介质层131应当具有大致相同的折射率，以减少层间界面的折射。优选地，透明介质层132与吸光介质层131的折射率差的绝对值应当不大于0.2。例如，可以利用紫外固化UV胶水工艺，在吸光介质层131的非垂直表面涂一层透明胶水，以形成与吸光介质层131的形状匹配的透明介质层132，并且使透射吸光层13的总厚度为固定值。
三、全反射微结构单元的光学原理及角度选择
图9图示了根据本发明实施例的屏幕的全反射微结构单元的光学原理。为了便于分析，在下述的讨论中不考虑表面扩散层14对投影光线的光路优化。
如图9所示，微结构层121的折射率为n 1和内侧层122的折射率为n 2，微结构单元的第一平面124和第二平面125与屏幕平面(即，垂直方向)的夹角分别为θ 1和θ 2(单位为度，下同)。入射光线和反射光线与水平方向的夹角分别为α和β(单位为度，下同)。其中，当反射光线水平出射时，β显然为0度，并且设定：当反射光线在水平线以下(即，偏向地面)时β为负值，当反射光线在水平线以上(即，偏向天花板)时β为正值。为了使来自投影机的入射光线在两个倾斜面上发生两次全反射后向着观看者的眼睛方向出射，根据几何光学原理和光学全反射条件，必须要满足如下的公式(4)～(6)：
Figure PCTCN2018110333-appb-000003
Figure PCTCN2018110333-appb-000004
Figure PCTCN2018110333-appb-000005
基于上述公式(4)～(6)并不能完全确定θ 1和θ 2的值，还留有一定的设计自由度。假设入射光线和出射光线之间的中间光线与屏幕平面(即，垂直方向)的夹角为γ，并且设定当中间光线偏向观众侧时γ为正值，当中间光线偏向远离观众侧时γ为负值。则根据几何光学原理和光学全反射条件可以计算出：
Figure PCTCN2018110333-appb-000006
Figure PCTCN2018110333-appb-000007
由公式(7)和(8)可知，只要确定了入射光线、出射光线和中间光线的光路(即，确定了α、β和γ)，就可以完全确定微结构的两个相交平面的倾斜角度θ 1和θ 2。
此外，由公式(7)和(8)还可知，即便在确定了入射光线、出射光线的光路的情况下，还可以根据不同的应用需求，通过调整中间光线的光路(即，调整γ的取值)在一定范围内对θ 1和θ 2的取值进行选择。例如，在超短焦投影的应用中，投影机位于屏幕的下方，所以α>0总是成立；且观众的眼睛位于投影机的上方，为了保证出射光线入射至观众眼睛，所以α+β>0也总是成立；在此情况下，由公式(4)可以得到：
θ 1+θ 2＜90          (9)
由公式(9)可知，在超短焦投影的应用中，根据本发明的屏幕的微结构单元的第一平面124和第二平面125之间的夹角必须为钝角。
图10的a中示出了一种理想的光路情况，其中，入射的投影光线Vin经过微结构单元的一个斜面的全反射后的中间光线Vmid在微结构层121中沿着与屏幕平面平行的方向行进，Vmid经过微结构单元的另一个斜面的全反射之后成为向着观看者方向水平出射的出射光线Vout。
在图10的a中所示的情况下，此时，γ＝0度，β＝0度，当θ 2＝45度， 出射光线沿着与屏幕垂直的出射即β＝0度，再依据上述公式(9)可知θ 1<45度，也即θ 1<θ 2。
但在实际应用中，也可能存在如图10的b和c示出了非理想的光路情况。在图10的b中，入射光线Vin经微结构单元的第一斜面的全反射后产生了中间光线Vmid，但Vmid的行进方向不平行于屏幕平面，而是偏向于观看者一侧(此时γ为正值)。因此，部分Vmid可能不被第二斜面反射而直接出射，无法充分利用微结构单元的第一斜面。在图10的c中，入射光线Vin经微结构单元的第一斜面的全反射后产生了中间光线Vmid，但Vmid的行进方向不平行于屏幕平面，而是偏向于背向观看者的一侧(此时γ为负值)。因此，无法充分利用微结构单元的第二斜面。
另外，如上所述，根据本发明的屏幕具有旋转对称结构，且包含多个微结构单元。因此，每个微结构单元的角度设计可以是相同的或不同的。例如，图11图示了根据本发明的屏幕的微结构单元的光学角度的模拟实例。图11的a所示的屏幕的焦点位于无穷远处，也即是说，在屏幕的所有微结构单元中，出射光线均水平地射向观看者的方向，所以β＝0度且θ 2＝45度一直成立。根据模拟结果可知，微结构单元的θ 1随着靠近屏幕的上方而逐渐减小，且θ 1<θ 2，因而满足上述公式(9)。在图11的b所示的屏幕中，屏幕的焦点不再位于无穷远处。在此情况下，沿着从屏幕的中心至屏幕边缘的方向，屏幕的微结构单元的θ 1的取值不断减小而θ 2的取值不断增大。
四、微结构层和内侧层的折射率选择
除了θ 1和θ 2的取值之外，由光学全反射公式可知，满足两次全反射的全反射微结构单元还受到微结构层121的折射率n 1和内侧层122的折射率n 2的影响。根据本发明的屏幕的微结构层121通常是由透明树脂材料制成的，其折射率在1.3～1.7的范围内。或者，微结构层121也可以使用具有类似折射率的其它材料制成。另外，还可以在制成微结构层121的材料中掺杂散射离子或吸收材料等。因而，为了满足全反射的条件，需要考虑内侧层122的折射率n 2的选择。图12显示了内侧层122的不同折射率n 2对于微结构单元的入射光线的全反射区域的影响。如图12的上侧的a所示，入射光线V可以表示成(V x,V y,V z)，其中z轴垂直于屏幕，而X,Y轴平行于屏幕。显然，入射光线的全反射区域取决于V x和V y的 取值范围。V z满足：
Figure PCTCN2018110333-appb-000008
假定出射光线朝向观看者的眼睛且微结构层121的折射率n 1为1.6，根据上述公式(5)和(6)可以获得满足全反射条件的入射光线的分量(V x,V y)的取值范围随内侧层122的折射率n 2的变化趋势。如图12的下侧的b所示，随着n 2的增大，满足在微结构单元的两个斜面均发生全反射的入射光线的区域不断减少。换言之，随着n 2的增大，从投影机发出的光线无法在微结构单元的两个斜面发生两次全反射的几率增大。因此，为了保证一定的屏幕反射效率，需要使n 1和n 2满足：
n 2<n 1-0.2        (11)
在满足上述条件的情况下，内侧层122优选是空气层。
应当理解的是，上述的示例性实施例不是限制性的，而仅是所有方面的示例。本领域技术人员在不背离本发明的精神和主旨的前提下，显然能够对上述实施例进行各种合理的修改和替换。例如，在上面的实施例中，为了获得具有高对比度的投影图像，投影反射层是由全反射层和吸光层构成的。然而，也可以采用本领域内已知的菲涅尔反射层等常用的反射层作为投影反射层。图13图示了在此情况下的屏幕结构示意图。由图13可知，除了采用菲涅尔反射层15作为投影反射层之外，此例中的屏幕的表面扩散层和透射吸光层的结构、功能和特性与上文中的实施例中所述的相同。
尽管在上面已经参照附图说明了根据本发明的屏幕及投影系统，但是本发明不限于此，且本领域技术人员应理解，在不偏离本发明随附权利要求书限定的实质或范围的情况下，可以做出各种改变、组合、次组合以及变型。

Claims (10)

  1. 一种屏幕，其能够将来自投影机的投影光线反射至观看者的视场范围内，其特征在于，所述屏幕至少包括从所述投影光线的入射侧依次层叠设置的表面扩散层、透射吸光层和投影反射层，
    所述投影反射层选择性地反射所述投影光线，并且
    所述透射吸光层中包含吸光材料颗粒，所述吸光材料颗粒在所述透射吸光层中的分布是根据所述投影光线在所述屏幕的表面的菲涅尔损耗的分布而设定的，以使在菲涅尔损耗越大的区域中所述透射吸光层的透光率越高。
  2. 根据权利要求1所述的屏幕，其特征在于，所述透射吸光层包括吸光介质层和透明介质层，
    所述吸光介质层中包含以均匀密度分布的吸光材料颗粒，所述吸光介质层的不同区域内的厚度与相应区域中的屏幕表面对所述投影光线的菲涅尔反射率成反比，并且
    所述吸光介质层和所述透明介质层的总厚度为固定值，且所述吸光介质层和所述透明介质层的折射率的差的绝对值不大于0.2。
  3. 根据权利要求2所述的屏幕，其特征在于，在水平方向上，所述吸光介质层的厚度从屏幕中心向两侧逐渐减小和/或在垂直方向上，所述吸光介质层的厚度从屏幕下方向屏幕上方逐渐减小。
  4. 根据权利要求2所述的屏幕，其特征在于，所述吸光介质层的在水平方向上的厚度变化符合直线分布或曲线分布或所述吸光介质层的在垂直方向上的厚度变化符合直线分布或曲线分布。
  5. 根据权利要求2所述的屏幕，其特征在于，所述吸光介质层含有吸光染料，并且所述吸光介质层的不同区域的厚度之间的最大厚度差随着所述吸光染料的配比的增大而减小。
  6. 根据权利要求2所述的屏幕，其特征在于，所述透明介质层是透明胶水层。
  7. 根据权利要求1至6中任一项所述的屏幕，其特征在于，所述投影反射层包括从所述投影光线的入射侧依次层叠的全反射层和吸光层，
    所述吸光层能够吸收光，
    所述全反射层包括微结构层，所述微结构层包含多个微透镜单元，所述微结构单元具有位于下侧的第一平面和位于上侧的第二平面，所述第一平面和所述第二平面相交，所述多个微结构单元构成锯齿结构，所述投影光线能够连续在所述第一平面和所述第二平面发生全反射。
  8. 根据权利要求7中所述的屏幕，其特征在于，所述微结构层具有旋转对称结构，并且旋转中心轴线垂直于所述屏幕的平面且位于所述屏幕的下方。
  9. 根据权利要求1至6中任一项所述的屏幕，其特征在于，所述投影反射层是菲涅尔反射层。
  10. 一种投影系统，所述投影系统包括投影机和如权利要求1至9中任一项所述的屏幕。
PCT/CN2018/110333 2018-03-09 2018-10-16 屏幕和投影系统 WO2019169870A1 (zh)

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CN110955106B (zh) * 2018-09-27 2021-11-12 深圳光峰科技股份有限公司 投影屏幕和投影系统
CN110967914B (zh) * 2018-09-30 2021-10-22 深圳光峰科技股份有限公司 一种投影幕及投影系统
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