WO2019024367A1 - 投影屏幕和投影系统 - Google Patents

投影屏幕和投影系统 Download PDF

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Publication number
WO2019024367A1
WO2019024367A1 PCT/CN2017/114726 CN2017114726W WO2019024367A1 WO 2019024367 A1 WO2019024367 A1 WO 2019024367A1 CN 2017114726 W CN2017114726 W CN 2017114726W WO 2019024367 A1 WO2019024367 A1 WO 2019024367A1
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Prior art keywords
layer
projection screen
light
microstructure
projection
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PCT/CN2017/114726
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English (en)
French (fr)
Inventor
王霖
胡飞
李屹
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深圳市光峰光电技术有限公司
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Publication of WO2019024367A1 publication Critical patent/WO2019024367A1/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
    • G03B21/54—Accessories
    • G03B21/56—Projection screens
    • G03B21/60—Projection screens characterised by the nature of the surface

Definitions

  • the present invention relates to projection screens and projection systems.
  • the present invention relates to a projection screen capable of reducing Fresnel loss of a screen surface and a projection system using the same.
  • projection display systems are small in size and easy to install, making it easy to display images larger than 100 inches, and the overall system price is relatively low.
  • the traditional projector is called a telephoto projector.
  • This projector usually needs an distance of more than 3 meters to project an 80-inch screen on the screen.
  • the transmitted light is incident on the screen at a small angle of incidence, so it is also Become a direct projector.
  • Due to the limited indoor space, telephoto projectors are often difficult to transmit large projection images indoors, so short-focus or even ultra-short-focus projectors have emerged.
  • ultra-short-throw projectors on the market can transmit images of more than 80 inches at a distance of less than 1 meter.
  • the angle of incidence of projected light from an ultra-short-throw projector on the projection screen tends to be large, typically in the range of 40 to 75 degrees.
  • Figure 1 a shows a schematic view of the angle of incidence of the projected light from the ultra-short-throw projector on the projection screen
  • b shows 9 test points on the projection screen
  • c shows the projected light in a at b
  • the Fresnel reflectance of incident light on the surface of the screen can be as high as 25%.
  • projection display systems are often installed in the living room.
  • the living room usually has good natural lighting conditions and a bright illumination source, so there is a lot of ambient stray light.
  • a typical projector screen can reflect both the light of the projector and the light of ambient light. In such an environment, light reflected through the projection screen due to ambient light The contrast of the line formed by the line is much lower than the contrast of the projector itself.
  • current projection screens that are resistant to ambient light are implemented using an array microstructure plus a light reflecting layer or a light absorbing layer.
  • the pitch is generally in the range of 25 to 250 micrometers, and the process of selectively coating the optical functional layer on the surface of the microstructure is very complicated, the yield is low, and the optical efficiency is not high.
  • a projection screen is disclosed that is capable of reflecting projected light from a projector into a field of view of a viewer
  • the projection screen includes a surface microstructure layer, a light diffusion layer, and a light reflection layer, which are sequentially disposed from an incident side of the projection light, wherein
  • the light reflecting layer is configured to reflect the incident projected light into a range of the field of view of the viewer, the light diffusing layer for increasing a divergence angle of the emitted light, and
  • the surface microstructure layer includes a plurality of surface microstructure units, the plurality of surface microstructure units being periodically arranged in a line symmetrical manner with respect to a vertical center line of the projection screen in a plane of the projection screen, each The surface microstructure unit includes intersecting first bevels and second bevels.
  • a projection system is disclosed in accordance with another embodiment of the present invention, the system comprising a projection screen as described above and the projector. Wherein, the projector is preferably an ultra short throw projector located below the projection screen.
  • the projection screen and the projection system according to the present invention are capable of reducing the incident angle of the projection light of a large angle incident on the screen since the surface microstructure layer is provided and the surface microstructure layer has a periodically arranged surface microstructure. , which reduces the Fresnel reflectivity of the screen surface, thereby reducing the Fresnel loss and improving the optical efficiency.
  • the projection screen and projection system according to the present invention can also have the following advantages:
  • the microstructure uses the principle of total reflection to reflect the projected light, and the light absorbing layer for absorbing ambient stray light is integrally disposed on the back surface of the microstructure, and does not need to be coated with a metal reflective film or a light absorbing layer in the microstructure. Reduced costs and increased yield.
  • Figure 1 shows the relationship between the angle of incidence of the projected ray on the screen and the Fresnel reflectivity in the prior art.
  • FIG. 2 is a schematic diagram showing a projection screen and its surface microstructure layer in accordance with the present invention.
  • FIG. 3 is a schematic structural view showing a projection system according to an embodiment of the present invention.
  • FIG. 4 is a schematic diagram showing a rotationally symmetric structure of a reflective layer of a projection screen in accordance with an embodiment of the present invention.
  • FIG. 5 is a schematic cross-sectional view showing a microstructure unit of a reflective layer of a projection screen according to an embodiment of the present invention.
  • FIG. 6 is a schematic diagram showing the optical principle of a microstructure unit of a reflective layer of a projection screen in accordance with an embodiment of the present invention.
  • FIG. 7 is a schematic diagram showing selection of an optical tilt of a microstructure of a projection screen in accordance with an embodiment of the present invention.
  • FIG. 8 is a schematic diagram showing a pitch comparison of a microstructure unit and a surface microstructure unit of a projection screen according to an embodiment of the present invention.
  • FIG. 9 is a schematic diagram showing an arrangement example of surface microstructure units of a surface microstructure layer of a projection screen according to an embodiment of the present invention.
  • FIG. 10 is a schematic diagram showing another arrangement example of a surface microstructure unit of a surface microstructure layer of a projection screen according to an embodiment of the present invention.
  • FIG. 11 is a schematic diagram showing another arrangement example of a surface microstructure unit of a surface microstructure layer of a projection screen according to an embodiment of the present invention.
  • Fig. 12 is a view showing a comparison of incident angles when projection light is incident on the surface microstructure layer as shown in Figs. 9 to 11 and the screen of the prior art.
  • Fig. 13 is a view showing a comparison of incident angles when a projected light is incident on a surface microstructure layer having a fixed inclination angle and a surface microstructure layer having a varying inclination angle.
  • FIG. 14 is a schematic diagram showing another arrangement example of a surface microstructure unit of a surface microstructure layer of a projection screen according to an embodiment of the present invention.
  • Figure 15 is a graph showing the angle of incidence of projected light rays incident on different surface microstructure layers.
  • 16 is a schematic view showing a relationship between a surface microstructure unit and a microstructure unit of a projection screen according to an embodiment of the present invention.
  • FIG. 2 shows a schematic view of a projection screen in accordance with the present invention.
  • the projection screen is formed by a surface microstructure layer 30, a diffusion layer 40, and a reflective layer 50.
  • the diffusion layer 40 and the reflective layer 50 may adopt any known suitable scheme.
  • the surface microstructure layer 30 is a surface microstructure layer provided with periodically arranged surface microstructure units. The specific structure of the surface microstructure layer 30 will be described in detail below. Projected light incident at a large angle is incident on the surface microstructure layer 30, and the periodically arranged surface microstructure unit can reduce the Fresnel reflectivity of the incident projection light on the screen surface, allowing more light to pass through the surface microstructure layer 30.
  • the diffusion layer 40 is incident on the reflective layer 50. The projected light is reflected by the reflective layer 50 and exits toward the viewer's field of view.
  • the diffusion layer 40 is capable of increasing the divergence angle of the outgoing light. Therefore, such a projection screen is particularly suitable for use with an ultra short throw projector.
  • the reflective layer 50 of the projection screen according to the present invention may employ a reflective layer for projection screens in the prior art.
  • preferred embodiments of the present invention are also expected to further improve the ambient light resistance of the screen. Accordingly, such a preferred embodiment of the projection screen according to the present invention will be described hereinafter.
  • the projection system includes a projection screen 10 and a projector 20.
  • the projection screen 10 includes a surface microstructure layer 14 (corresponding to the surface microstructure layer 30 above), a light diffusion layer 13 (corresponding to the diffusion layer 40 above), which are sequentially stacked from the incident side of the projection light of the projector, The total reflection layer 12 (corresponding to the reflection layer 50 above).
  • the projection screen 10 according to a preferred embodiment of the present invention further includes a light absorbing layer 11 on the side of the total reflection layer 12 opposite to the incident side of the projected light.
  • the projected light from the projector 20 is incident on the total reflection layer 12 through the surface microstructure layer 14 and the light diffusion layer 13.
  • the incident side of the projected light of the projection screen 10 is also referred to as the outer side of the screen (ie, facing the viewer side), and the side of the light absorbing layer is referred to as the back side of the screen (ie, facing away from the viewer side).
  • the total reflection layer 12 is formed with an array of microstructured cells. Each microstructure unit contains two intersecting inclined planes. The tilt angles of the two inclined planes are precisely designed such that the projected light incident from below the screen 10 is continuously reflected twice in two oblique planes, and finally reflected into the viewer's field of view, and from the screen.
  • the ambient stray light above 10 cannot satisfy the condition that total reflection occurs on both inclined surfaces, and is absorbed by the light absorbing layer 11 through the total reflection layer 12.
  • the microstructure elements of the total reflection layer 12 have a rotationally symmetric 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 center point of the projection lens of the projector 20 is arranged on the central axis of rotation.
  • a light absorbing layer 11 is disposed inside the total reflection layer 12, and the light absorbing layer 11 is capable of absorbing a light beam incident thereon.
  • the light absorbing layer 11 is a black light absorbing layer.
  • a light diffusion layer 13 and a surface microstructure layer 14 are sequentially disposed outside the total reflection layer 12.
  • the light diffusing layer 13 serves to diffuse the collimated light beam reflected from the total reflection layer 12 to give the projection screen 10 a larger viewing angle.
  • the surface microstructure layer 14 is located on the surface (ie, the outer surface) on the incident side of the projection light of the light diffusion layer 13, and includes a plurality of inclined surfaces (described in detail later) which are arranged periodically, and can reduce the phenanthrene of the incident light at a large angle. Niel lost.
  • the light diffusion layer 13 and the surface microstructure layer 14 may be formed in one body. Further, a protective layer may be additionally provided on the outer side of the surface microstructure layer 14 to prevent scratching or chemical corrosion. Of course, other auxiliary function layers can also be set according to the design needs.
  • FIG. 5 shows a schematic diagram of a main cross-sectional structure of a microstructure unit of a total reflection layer 12 of a projection screen according to an embodiment of the present invention.
  • the total reflection layer 12 includes a transparent substrate 120, Microstructure layer 121 and inner layer 122.
  • the transparent substrate 120 is located on the side of the total reflection layer 12 closest to the light diffusion layer and is in contact with the light diffusion layer, wherein the transparent substrate 120 includes a transparent material such as PET, PC or PMMA.
  • the microstructure layer 121 is disposed on the opposite side of the side of the transparent substrate 120 that is in contact with the light diffusion layer.
  • 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 120 and the microstructured layer 121 are integrally formed by a UV coating device or a thermoforming device.
  • the inner layer 122 is formed on the side of the microstructure layer 121 near the light absorbing layer, 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 surface of the microstructure layer 121 adjacent to the inner layer 122 is provided with a plurality of microstructure units.
  • the microstructure layer 121 is formed as a total reflection prism and has two inclined intersection surfaces 124 and 125.
  • the microstructure layer 121 is a row of rotationally symmetric prisms formed on the surface of the transparent substrate 120, and the intersection surfaces 124 and 125 are the microstructure layer 121 and the inner layer 122
  • the interface between the two different material layers ie, the first material layer and the second material layer.
  • such prisms are processed by using a roll coating resin and a UV curing or heat curing process.
  • Fig. 5 for the sake of clarity of illustration, only two microstructure units are shown.
  • the incident ray 123 from the projector at the bottom of the screen undergoes two total reflections at two oblique planes 124 and 125, ultimately reflecting into the viewer's field of view.
  • the ambient stray light 127 is mainly from the ceiling light in the room. In most cases, 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 127 is much smaller than the angle of incidence of the projected light. Therefore, the ambient stray light 127 cannot satisfy the condition that two total reflections occur continuously in the plane 124 and the plane 125, and most of them pass through the total reflection layer 12 and are absorbed by the light absorbing layer 11. Since the light absorbing layer 11 is integrally disposed inside the total reflection layer 12, the manufacturing process is simple and does not cause loss of projection light.
  • the projection screen 10 utilizes the angle selective reflection characteristic of the total reflection layer 12 so that the screen can automatically distinguish between the projected light and the ambient light.
  • the surface microstructure layer 14 has a plurality of inclined surfaces arranged periodically to reduce the incident angle of the incident light, thereby reducing the Fresnel loss of the incident light on the screen surface.
  • the light absorbing layer 11 for absorbing ambient stray light is integrally provided inside the total reflection layer 12. Therefore, the projection screen 10 according to the embodiment of the present invention has a strong ability to resist ambient light and a Fresnel loss of a lower screen surface, improves the contrast of the screen image, improves optical efficiency, and simplifies The processing technology improves the yield.
  • Figure 6 illustrates the optical principles of a microstructured unit of a projection screen in accordance with an embodiment of the present invention.
  • the refractive index of the microstructure layer 121 is n 1 and the refractive index of the inner layer 122 is n 2
  • the angle between the two inclined planes 124 and 125 of the microstructure unit and the plane of the screen ie, the vertical direction
  • ⁇ 1 and ⁇ 2 the unit is degree, 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 20 In order to cause the incident light from the projector 20 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 formula (1) to (s) must be satisfied. 3):
  • the optical path of the intermediate light can be adjusted according to different application requirements (ie, the ⁇ is adjusted).
  • the value is selected within a certain range for the values of ⁇ 1 and ⁇ 2 .
  • the projector is located below the screen, so ⁇ >0 is always true; and the viewer's eyes are above the projector so ⁇ + ⁇ >0 is always true; in this case , can be obtained by formula (1):
  • the angle between the two inclined faces of the microstructure unit of the projection screen according to the present invention must be an obtuse angle.
  • the projected ray 123 from the ultra-short-throw projector follows the plane of the screen after two consecutive total reflections of the two inclined planes 124 and 125 of the microstructure unit.
  • the vertical direction horizontal direction
  • ⁇ 0 degrees.
  • the projection screen 10 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 7 illustrates a simulated example of the optical angle of a microstructure unit of a projection 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 (6).
  • the focus of the projection screen is no longer at infinity.
  • the value of ⁇ 1 of the microstructure unit of the total reflection layer 12 is continuously decreased and the value of ⁇ 2 is continuously increased.
  • the microstructure layer 121 of the projection 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.
  • 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 (2) and (3).
  • the range of values varies with the refractive index n 2 of the inner layer 122.
  • n 2 increases, the area of incident light that satisfies two consecutive total reflections in the two inclined planes of the microstructure unit of the total reflection layer 12 is continuously reduced.
  • n 2 increases, the probability that light emitted from the ultra-short-throw projector cannot continuously re-reflect twice in two inclined planes of the microstructure unit of the total reflection layer 12 increases. Therefore, in order to ensure a certain screen reflection efficiency, it is necessary to make n 1 and n 2 satisfy:
  • the inner layer 122 may be an air layer if the above conditions are satisfied. In this case, the tips of the two inclined faces of the microstructured layer 121 are directly bonded to the light absorbing layer 11.
  • the projected light incident side surface of the projection screen 10 is provided with the surface microstructure layer 14.
  • the surface microstructure layer 14 has a plurality of surface microstructure units arranged in series. Each surface microstructure unit includes a first bevel and a second bevel, wherein the first bevel is a bevel facing the ultra short throw projector and the second bevel is a bevel facing away from the ultra short throw projector.
  • the function of reducing the angle of incidence of the projected light on the projection screen relies primarily on the first bevel facing the projector, while the inclined surface facing away from the projector has no optical effect.
  • the inclination angle ⁇ of the first slope is smaller than the inclination angle of the second slope.
  • successive plurality of surface microstructure units of the surface microstructure layer 14 are arranged to be continuously arranged symmetrically with respect to the vertical centerline of the screen.
  • Periodically arranging a plurality of surface microstructure units of the surface microstructure layer 14 The arrangement of the plurality of microstructure units arranged periodically with the total reflection layer 12 described above is not necessarily the same, and as shown in FIG. 8, the arrangement pitch of the surface microstructure unit and the microstructure unit may be the same or different.
  • the relationship between the incident angle and ⁇ , the inclination angle ⁇ is:
  • FIGS. 9-11 An example of the arrangement of the surface microstructure units of the surface microstructure layer 14 is illustrated in FIGS. 9-11.
  • the surface microstructure unit of the surface microstructure layer 14 extends in the vertical direction, and the plurality of surface microstructure units are continuously arranged symmetrically with respect to the vertical center line of the screen in the horizontal direction, wherein FIG. 9 a shows a plan view of the surface microstructure layer 14, and b of Fig. 9 shows a perspective view and an enlarged schematic view of the first slope and the second slope.
  • FIG. 9 a shows a plan view of the surface microstructure layer 14
  • b of Fig. 9 shows a perspective view and an enlarged schematic view of the first slope and the second slope.
  • the surface microstructure unit of the surface microstructure layer 14 extends in an oblique direction, and the plurality of surface microstructure units are continuously arranged symmetrically with respect to a vertical center line of the screen in a direction perpendicular to the extending direction.
  • a of FIG. 10 shows a plan view of the surface microstructure layer 14, and b of FIG. 10 shows a perspective view and an enlarged schematic view of the first slope and the second slope.
  • the surface microstructure unit of the surface microstructure layer 14 extends in the horizontal direction, and the plurality of surface microstructure units are continuously arranged symmetrically with respect to the vertical center line of the screen in the vertical direction, wherein A of 11 shows a plan view of the surface microstructure layer 14, and b of Fig. 11 shows a perspective view and an enlarged schematic view of the first slope and the second slope.
  • the surface microstructure elements of the surface microstructure layer 14 shown in Figures 9 through 11 all employ a linear arrangement that is easy to design and process.
  • a comparison of the incident angles of projected light from the same projector on the screen surface employing the three surface microstructure layers 14 described above and the conventional screen surface without the inclined plane is shown in FIG.
  • the position of the test point is the same as that shown in FIG. 1, and the inclination angles of the first slopes of the above three surface microstructure layers 14 are each set to 10 degrees.
  • the surface microstructure layer 14 using the above three structures can reduce the incident angle of the projected light compared to the conventional flat screen.
  • the ultra-short-throw projector since the ultra-short-throw projector is usually located at the lower middle position of the projection screen, the incident angles from the same projector are actually different at different angles of incidence of the screen. It is easy to know that the incident angle of the projected light above the screen is smaller than the incident angle at the bottom of the screen; the incident angle of the projected light at the edge of the screen is smaller than that on the screen. The central angle of incidence. Therefore, with the above three linear arrangement methods, although the incident angle of the projected light can be reduced as a whole, the brightness of the screen surface may be uneven due to the difference in Fresnel reflectance at different positions on the screen surface. In order to make the brightness of the screen surface more uniform, the following more preferable arrangement can be employed.
  • the tilt angle ⁇ of the first slope in each surface microstructure unit may follow from below the screen. Gradually increase to the top of the screen. That is, the inclination angle ⁇ of the first slope in the surface microstructure unit located above the screen is larger than the inclination angle ⁇ of the first slope in the surface microstructure unit located below the screen.
  • the inclination angle ⁇ of the first slope in each surface microstructure unit may gradually increase from the center of the screen to both sides of the screen. Big.
  • Fig. 13 is a view showing a comparison of incident angles of projection rays when the inclination angle ⁇ of the first slope of each surface microstructure layer is fixed at 0 degrees, 10 degrees, 20 degrees, and ⁇ is changed as described above.
  • the surface microstructure unit of the surface microstructure layer 14 may also adopt a rotationally symmetric structure similar to that of the aforementioned total reflection layer.
  • the incident angle of the projection ray is not for the same surface microstructure unit. changing.
  • FIG. 15 illustrates the effect of the horizontal surface microstructure unit shown in FIG. 11 and the rotationally symmetric surface microstructure unit shown in FIG. 14 on the incident angle in the case where the first slope is set to 20 degrees. Comparison (number of test points is shown in Figure 1). As can be seen from Fig.
  • the rotationally symmetrical surface microstructure unit The effect is significantly better than the horizontal surface microstructure unit.
  • the inclination angle ⁇ of the first slope in each of the rotationally symmetric surface microstructure units may be gradually increased as the distance from the axis of symmetry increases.
  • the projected light from the ultra-short-throw projector is incident on the total reflection layer 12 through the surface microstructure layer 14, is reflected by the total reflection layer 12, and is then transmitted through the surface microstructure layer 14. Therefore, the aforementioned inclination angle ⁇ of the first slope of the surface microstructure unit obviously affects the setting of the inclination angles of the two inclined planes in the microstructure unit. As shown in FIG. 16, it is assumed that the inclination angle ⁇ of the first inclined surface of the surface microstructure unit with respect to the plane of the screen is constant, and the angle between the incident projection ray and the projected projection ray and the horizontal direction are ⁇ and ⁇ , respectively, outside the screen.
  • the medium generally, air
  • the angle between the surface normal of the first slope of the surface microstructure unit and the horizontal direction is also ⁇ .
  • the angles ⁇ and ⁇ and ⁇ , ⁇ of the incident ray and the reflected ray as described above in the above-described microstructure layer 121 having the refractive index n 1 as described above can be calculated.
  • the relationship between ⁇ and ⁇ satisfies the following formula:
  • the range of the inclination angle ⁇ should be in the range of 0 ⁇ ⁇ ⁇ 50.
  • first bevel and the second bevel of the surface microstructure unit may be surface roughened by sand blasting, chemical etching or other processes, thereby enabling the surface microstructure layer 14 to reduce the Fresnel loss of the screen surface. It also has the function of expanding the field of view of the screen.
  • the surface microstructure layer 14 detailed in this section is applicable not only to the above-described projection screen 10 according to the preferred embodiment of the present invention provided with the total reflection layer 12, but as described above, Suitable for projection screens using reflective layers of the prior art.
  • the primary object of the present invention is to reduce the Fresnel reflectivity of the projection light incident at a large incident angle on the surface of the projection screen, thereby improving the optical efficiency of the screen.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Overhead Projectors And Projection Screens (AREA)
  • Projection Apparatus (AREA)
  • Optical Elements Other Than Lenses (AREA)

Abstract

一种投影屏幕（10）和使用屏幕的投影系统，投影屏幕（10）包括从投影光线的入射侧依次布置的表面微结构层（14）、光扩散层（13）和光反射层（12），其中，光反射层（12）用于将入射的投影光线反射至观看者的视场范围内，光扩散层（13）用于增大出射的光线的发散角，并且表面微结构层（14）包括多个表面微结构单元，多个表面微结构单元在投影屏幕（10）的平面内相对于投影屏幕（10）的垂直中线以线对称的方式周期性排布，各表面微结构单元包括相交的第一斜面和第二斜面，微结构单元的角度选择特性反射来自投影机（20）的至少部分光线，同时却基本不朝观看者的观看区域反射环境杂光，因此具有很强的抗环境光特性，提高了图像的对比度。

Description

投影屏幕和投影系统 技术领域
本发明涉及投影屏幕和投影系统。具体地，本发明涉及能够降低屏幕表面的菲涅尔损耗的投影屏幕和使用该屏幕的投影系统。
背景技术
近年来，随着投影机亮度的不断提高，投影显示系统在大尺寸家庭影院应用中的优势开始体现出来。相比于LCD电视和OLED电视，投影显示系统的尺寸小，便于安装，可以轻松实现大于100寸的显示画面，并且整套系统价格相对较低。
传统的投影机被称为长焦投影机，这种投影机在屏幕上投射出80寸的画面通常需要3米以上的距离，透射光线以较很小的入射角入射在屏幕上，因此也被成为直投投影机。由于室内空间有限，长焦投影机往往难以在室内透射出大的投影画面，于是短焦甚至超短焦投影机应运而生。目前市面上的超短焦投影机能够在1米以内的距离透射出80寸以上的画面。
对于配合超短焦投影机使用的投影屏幕而言，来自超短焦投影机的投影光线在投影屏幕上的入射角度往往较大，通常在40～75度的范围内。图1的a示出了来自超短焦投影机的投影光线在投影屏幕上的入射角度的示意图，b示出了投影屏幕上的9个测试点，c示出了a中的投影光线在b中的9个测试点上的入射角度和菲涅尔反射的关系。在大入射角度的情况下，入射光线在屏幕表面上的菲涅尔反射率可能高达25％。发生菲涅尔反射的这部分投影光线无法进入到观众的视场范围内，而是被屏幕反射到了天花板的方向。从而造成了光的菲涅尔损耗。目前，市面上的配合超短焦投影机使用的投影屏幕的上述菲涅尔损耗可以高达25％。
此外，在家庭应用环境中，投影显示系统往往被安装在客厅中。客厅通常具有良好的自然采光条件以及明亮的照明光源，因而存在大量的环境杂光。一般的投影机屏幕既能反射投影机的光线也能反射环境光的光线。在这样的环境中，由于受到环境光的影响，经投影屏幕反射的光 线形成的画面的对比度远远低于投影机自身的对比度。为了提高在存在环境光的情况下的屏幕对比度，目前抗环境光的投影屏幕都采用阵列微结构加光反射层或者光吸收层的方法来实现。但由于微结构的尺寸非常的小，间距一般在25到250微米的范围内，在微结构表面选择性的涂敷光学功能层的工艺非常复杂，成品率低，而且光学效率不高。
发明内容
针对上述问题，本发明的一个方面期望提供一种能够降低屏幕表面的菲涅尔损耗的投影屏幕和投影系统。
此外，本发明的另一个方面还期望提供一种能够在降低屏幕表面的菲涅尔损耗的同时能够抗环境光的投影屏幕和投影系统。
根据本发明的实施例，公开了一种投影屏幕，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，
所述投影屏幕包括从所述投影光线的入射侧依次布置的表面微结构层、光扩散层和光反射层，其中，
所述光反射层用于将入射的所述投影光线反射至观看者的所述视场范围内，所述光扩散层用于增大出射的光线的发散角，并且
所述表面微结构层包括多个表面微结构单元，多个所述表面微结构单元在所述投影屏幕的平面内相对于所述投影屏幕的垂直中线以线对称的方式周期性排布，各所述表面微结构单元包括相交的第一斜面和第二斜面。根据本发明的另一实施例公开了一种投影系统，所述系统包括如上所述的投影屏幕以及所述投影机。其中，所述投影机优选是位于所述投影屏幕下方的超短焦投影机。
如上所述，根据本发明的投影屏幕和投影系统由于设置有表面微结构层并且表面微结构层具有周期性排布的表面微结构，能够减小大角度入射的投影光线在屏幕上的入射角度，降低了屏幕表面的菲涅尔反射率，从而降低了菲涅尔损耗，提高了光学效率。
此外，更加优选地，根据本发明的投影屏幕和投影系统还能够具有如下优点：
(1)利用反射层的微结构单元的角度选择特性反射来自投影机的至少部分光线，同时却基本不朝观看者的观看区域反射环境杂光，因此具 有很强的抗环境光特性，提高了图像的对比度。
(2)微结构利用全反射原理对投影光线进行反射，用于吸收环境杂光的光吸收层整体地设置在微结构的背面，不需要在微结构中涂镀金属反射膜或光吸收层，降低了成本，提高了成品率。
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示出了现有技术中的投影光线在屏幕上的入射角度与菲涅尔反射率之间的关系。
图2是示出了根据本发明的投影屏幕及其表面微结构层的示意图。
图3是示出了根据本发明实施例的投影系统的结构示意图。
图4是示出了根据本发明实施例的的投影屏幕的反射层的旋转对称结构的示意图。
图5是示出了根据本发明实施例的投影屏幕的反射层的微结构单元的截面结构示意图。
图6是示出了根据本发明实施例的投影屏幕的反射层的微结构单元的光学原理的示意图。
图7是示出了根据本发明实施例的投影屏幕的微结构的光学倾角的选择示意图。
图8是示出了根据本发明实施例的投影屏幕的微结构单元与表面微结构单元的节距对比的示意图。
图9是示出了根据本发明实施例的投影屏幕的表面微结构层的表面微结构单元的排布示例的示意图。
图10是示出了根据本发明实施例的投影屏幕的表面微结构层的表面微结构单元的另一排布示例的示意图。
图11是示出了根据本发明实施例的投影屏幕的表面微结构层的表面微结构单元的又一排布示例的示意图。
图12示出了投影光线入射在如图9至图11所示的表面微结构层以及现有技术的屏幕上时入射角度的对比图。
图13示出了投影光线入射在固定倾斜角的表面微结构层和变化倾斜角的表面微结构层时入射角度的对比图。
图14是示出了根据本发明实施例的投影屏幕的表面微结构层的表面微结构单元的又一排布示例的示意图。
图15是示出了投影光线入射在不同的表面微结构层时入射角度的对比图。
图16是示出了根据本发明实施例的投影屏幕的表面微结构单元与微结构单元之间的关系的示意图。
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，图示出的屏幕的多层结构中各层的厚度、厚度比例以及角度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、投影屏幕和投影系统概述
图2示出了根据本发明的投影屏幕的示意图。该投影屏幕由表面微结构层30、扩散层40和反射层50形成。其中，扩散层40和反射层50可以采用任何已知的适合方案。表面微结构层30是设置有周期性排布的表面微结构单元的表面微结构层。表面微结构层30的具体结构将在下文中详细说明。大角度入射的投影光线入射至表面微结构层30，周期性布置的表面微结构单元能够降低入射的投影光线在屏幕表面的菲涅尔反射率，使更多的光线透过表面微结构层30和扩散层40入射至反射层50。投影光线经过反射层50的反射后向着观看者的视场方向出射。扩散层40能够增大出射光线的发散角。因此，这样的投影屏幕尤其适用与超短焦投影机配合使用。
此外，虽然根据本发明的投影屏幕的反射层50可以采用现有技术中的用于投影屏幕的反射层。但除了降低屏幕表面的菲涅尔反射率之外，本发明的优选实施例还期望能够进一步地提高屏幕的抗环境光能力。因此，在下文中将对根据本发明的投影屏幕的这样的优选实施例进行说明。
图3是示出了根据本发明的优选实施例的投影系统的结构示意图。 如图3中所示，投影系统包括投影屏幕10和投影机20。投影屏幕10包括从投影机的投影光线的入射侧依次层叠布置的表面微结构层14(与上文中的表面微结构层30对应)、光扩散层13(与上文中的扩散层40对应)、全反射层12(与上文中的反射层50对应)。此外，根据本发明优选实施例的投影屏幕10还包括位于全反射层12的与投影光线的入射侧相反一侧的光吸收层11。来自投影机20的投影光线透过表面微结构层14、光扩散层13入射至全反射层12。在下文中，也将投影屏幕10的投影光线的入射侧称为屏幕的外侧(即，面向观众一侧)，将光吸收层侧称为屏幕的背侧(即，背向观众一侧)。全反射层12形成有微结构单元阵列。每个微结构单元包含两个相交的倾斜平面。这两个倾斜平面的倾斜角度经过精确的设计，使得从屏幕10下方入射的投影光线在两个倾斜平面连续发生两次全反射，最终被反射至观看者的视场范围内，而来自于屏幕10上方的环境杂光无法满足在两个倾斜面上均发生全反射的条件，透过全反射层12而被光吸收层11吸收。
如图4所示，全反射层12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的投影镜头的中心点布置在该旋转中心轴线上。
在全反射层12的内侧布置有光吸收层11，光吸收层11能够吸收入射在其上的光束。例如，光吸收层11是黑色的光吸收层。在全反射层12的外侧依次设置有光扩散层13和表面微结构层14。光扩散层13用于扩散从全反射层12反射出的准直光束，以使投影屏幕10具有更大的可视角度。表面微结构层14位于光扩散层13的投影光线入射侧的表面(即，外表面)，包括周期性排布的多个倾斜表面(下文中将详细说明)，能够降低大角度入射光线的菲涅尔损失。光扩散层13和表面微结构层14可以被形成为一体。此外，在表面微结构层14的外侧还可以添加设置保护层以防止刮伤或者化学腐蚀。当然，还可以根据设计需要设置其它的辅助功能层。
图5示出了根据本发明实施例的投影屏幕的全反射层12的微结构单元的主截面结构示意图。为了清楚图示，图5中省略了全反射层12和光吸收层11之外的其它层。所图5所示，全反射层12包括透明基材120、 微结构层121和内侧层122。透明基材120位于全反射层12的最靠近光扩散层侧并且与光扩散层接触，其中所述透明基材120包括PET、PC或PMMA等透明材料。微结构层121设置在透明基材120的与光扩散层接触的一侧的相对侧。其中，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。透明基材120和微结构层121通过UV涂布设备或者热成型设备形成一体。内侧层122形成在微结构层121的靠近光吸收层侧，并且与光吸收层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。所述微结构层121与内侧层122相邻的表面设置有多个微结构单元。在全反射层12的每一个微结构单元中，微结构层121被形成为全反射棱镜并且具有两个倾斜的相交表面124和125。换言之，在全反射层12的每一个微结构单元中，微结构层121是在透明基材120的表面上形成的一排旋转对称的棱镜，相交表面124和125是微结构层121与内侧层122这两种不同的材料层(即，第一材料层和第二材料层)之间的界面。例如，这样的棱镜是通过采用对卷涂布树脂和UV固化或热固化工艺加工而成的。图5中为了图示清楚，仅示出了两个微结构单元。来自屏幕下方的投影机的入射光线123在两个倾斜平面124和125处连续发生两次全反射，最终反射到观看者的视场范围内。环境杂光127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127的入射角远小于投影光线的入射角度。因此，环境杂光127无法满足在平面124和平面125连续发生两次全反射的条件，绝大部分透过了全反射层12而被光吸收层11吸收。由于光吸收层11整体地设置在全反射层12的内侧，所以制造工艺简单，且不会导致投影光线损失。
如上所述，根据本发明实施例的投影屏幕10利用了全反射层12的角度选择性反射特性，使得屏幕能够自动区分投影光线与环境光线。表面微结构层14具有周期性排布的多个倾斜表面，能够减小入射光线的入射角，从而降低入射光线在屏幕表面的菲涅尔损耗。此外，用于吸收环境杂光的光吸收层11整体地设置在全反射层12的内侧。因此，根据本发明实施例的投影屏幕10具有较强的抗环境光的能力以及较低的屏幕表面的菲涅尔损耗，提高了屏幕图像的对比度，提高了光学效率，简化了 加工工艺，提高了成品率。
二、微结构单元的光学原理及角度选择
图6图示了根据本发明实施例的投影屏幕的微结构单元的光学原理。如图6所示，微结构层121的折射率为n1和内侧层122的折射率为n2，微结构单元的两个倾斜平面124和125与屏幕平面(即，垂直方向)的夹角分别为θ1和θ2(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20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(1)～(3)：
Figure PCTCN2017114726-appb-000001
Figure PCTCN2017114726-appb-000002
Figure PCTCN2017114726-appb-000003
基于上述公式(1)～(3)并不能完全确定θ1和θ2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 PCTCN2017114726-appb-000004
Figure PCTCN2017114726-appb-000005
由公式(4)和(5)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θ1和θ2。
此外，由公式(4)和(5)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θ1和θ2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所以α+β>0也总是成立；在此情况下，由公式(1)可以得到：
θ1+θ2＜90   (6)
由公式(6)可知，在超短焦投影的应用中，根据本发明的投影屏幕的微结构单元的两个倾斜面之间的夹角必须为钝角。
另外，由上述分析可知，存在这样一种优选的情况：来自超短焦投影机的投影光线123在经过微结构单元的两个倾斜平面124和125的连续两次全反射后沿着与屏幕平面垂直的方向(水平方向)出射，即，β＝0度。此时，根据光学原理，两次全反射之间在微结构层121中行进的中间光线沿着平行于屏幕平面的方向(垂直方向)行进，即γ＝0度且θ2＝45度，θ1<45度，即θ1<θ2。
另外，如上所述，根据本发明的投影屏幕10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7图示了根据本发明的投影屏幕的微结构单元的光学角度的模拟实例。图7的a所示的投影屏幕的焦点位于无穷远处，也即是说，在全反射层12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θ2＝45度一直成立。根据模拟结果可知，微结构单元的θ1随着靠近屏幕的上方而逐渐减小，且θ1<θ2，因而满足上述公式(6)。在图7的b所示的示例中，投影屏幕的焦点不再位于无穷远处。在此情况下，沿着从屏幕下方到屏幕上方的方向，全反射层12的微结构单元的θ1的取值不断减小而θ2的取值不断增大。
三、微结构单元的折射率选择
除了θ1和θ2的取值之外，由光学全反射公式可知，满足两次全反射的微结构单元还受到微结构层121的折射率n1和内侧层122的折射率n2的影响。根据本发明的投影屏幕的微结构层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n2的选择。例如，入射光线V可以表示成(Vx,Vy,Vz)，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Vx和Vy的取值范围。Vz满足：
Figure PCTCN2017114726-appb-000006
假定出射光线朝向观看者的眼睛且微结构层121的折射率n1为1.6，根据上述公式(2)和(3)可以获得满足全反射条件的入射光线的分量(Vx,Vy)的取值范围随内侧层122的折射率n2的变化趋势。随着n2的增大，满足在全反射层12的微结构单元的两个倾斜平面连续发生两次全反射的入射光线的区域不断减少。换言之，随着n2的增大，从超短焦投影机发出的光线无法在全反射层12的微结构单元的两个倾斜平面连续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n1和n2满足：
n2<n1-0.2   (8)
应当理解，在满足上述条件的情况下，内侧层122可以是空气层。在此情况下，微结构层121的两个斜面的尖端直接粘接至光吸收层11。
四、表面微结构层的详细说明
如上所述，为了减小来自超短焦投影机的投影光线在投影屏幕上的入射角度，投影屏幕10的投影光线入射侧表面设置有表面微结构层14。表面微结构层14具有多个连续布置的表面微结构单元。各表面微结构单元包括第一斜面和第二斜面，其中，第一斜面是面向超短焦投影机的斜面，而第二斜面是背向超短焦投影机的斜面。减少投影光线在投影屏幕上的入射角的功能主要依靠面向投影机的第一斜面，而背向投影机的倾斜面没有光学作用。因此，通过设置和调整第一斜面相对于屏幕平面的倾斜角δ，能够减小投影光线在投影屏幕上的实际入射角度，从而投影屏幕的降低菲涅尔损耗。通常，第一斜面的倾斜角小于第二斜面的倾斜角是优选的。
由于超短焦投影机一般位于投影屏幕的下方正中间位置，所以表面微结构层14的连续多个表面微结构单元被设置为相对于屏幕的垂直中线线对称地连续排布。表面微结构层14的周期性排布多个表面微结构单元 和上述的全反射层12的周期性排布的多个微结构单元的排布方式不一定相同，并且如图8所示，表面微结构单元和微结构单元的布置节距可以相同或不同。此外，由图8和图16可知，入射角度和ε，倾斜角度δ的关系为：
入射角度＝ε－δ；
因此，倾斜角δ越大，投影光线在投影屏幕上的实际入射角就越小。
图9至图11中图示了表面微结构层14的表面微结构单元的排布方式的示例。如图9所示，表面微结构层14的表面微结构单元沿着垂直方向延伸，并且多个表面微结构单元在水平方向上相对于屏幕的垂直中线线对称地连续排布，其中，图9的a示出了表面微结构层14的平面图，图9的b示出了立体示意图以及第一斜面和第二斜面的放大示意图。如图10中所示，表面微结构层14的表面微结构单元沿着倾斜方向延伸，并且多个表面微结构单元在与延伸方向垂直的方向上相对于屏幕的垂直中线线对称地连续排布，其中，图10的a示出了表面微结构层14的平面图，图10的b示出了立体示意图以及第一斜面和第二斜面的放大示意图。如图11中所示，表面微结构层14的表面微结构单元沿着水平方向延伸，并且多个表面微结构单元在垂直方向上相对于屏幕的垂直中线线对称地连续排布，其中，图11的a示出了表面微结构层14的平面图，图11的b示出了立体示意图以及第一斜面和第二斜面的放大示意图。
图9至图11中所示的表面微结构层14的表面微结构单元均采用了容易设计和加工的线性排布方式。图12中示出了来自相同投影机的投影光线在采用上述三种表面微结构层14的屏幕表面以及传统的不含有倾斜平面的屏幕表面的入射角度的对比。测试点的位置与图1中所示的位置相同，并且上述三种表面微结构层14的第一斜面的倾斜角度均设置为10度。由图12可知，采用上述三种结构的表面微结构层14相比于传统的平面屏幕，均能够减小投影光线的入射角度。
此外，有图12也可以看出，由于超短焦投影机通常位于投影屏幕的下方正中间位置，所以来自于同一投影机的投影光线实际上在屏幕的不同位置的入射角度是有区别的。容易得知：投影光线在屏幕上方的入射角小于在屏幕下方的入射角；投影光线在屏幕边缘的入射角小于在屏幕 中央的入射角。因此，采用上述三种线性排布方式，虽然可以整体上减小投影光线的入射角，但由于屏幕表面的不同位置处的菲涅尔反射率不同，所以屏幕表面的亮度可能会不均匀。为了使屏幕表面的亮度更加均匀，可以采用以下更加优选的排布方式。
例如，当表面微结构层14的表面微结构单元采用如图10和图11所示的倾斜或水平微结构单元时，各表面微结构单元中第一斜面的倾斜角δ可以随着从屏幕下方至屏幕上方而逐渐增大。即，位于屏幕上方的表面微结构单元中的第一斜面的倾斜角δ大于位于屏幕下方的表面微结构单元中的第一斜面的倾斜角δ。当表面微结构层14的表面微结构单元采用如图8所示的垂直微结构单元时，各表面微结构单元中第一斜面的倾斜角δ可以随着从屏幕中心向屏幕两侧而逐渐增大。即，位于屏幕外侧的表面微结构单元中的第一斜面的倾斜角δ大于位于屏幕内侧的表面微结构单元中的第一斜面的倾斜角δ。图13示出了各表面微结构层的第一斜面的倾斜角δ固定为0度、10度、20度时以及δ如上所述地变化时投影光线的入射角度的对比。
此外，更加优选地，如图14所示，表面微结构层14的表面微结构单元也可以采用与前述全反射层的微结构单元类似的旋转对称结构。当表面微结构层14的表面微结构单元采用相对于经过投影机的中心并垂直于屏幕表面的对称轴线旋转对称的结构，所以对于同一个表面微结构单元而言，投影光线的入射角度是不变的。图15中图示了在第一斜面均设定为20度的情况下，如图11中所示的水平表面微结构单元与图14中所示的旋转对称表面微结构单元对入射角度影响的对比(测试点的编号如图1中所示)。由图15可以看出，在位于屏幕的水平对称中心的点1、2和3处，两者减小投影光线的入射角度相同，但是随着测试点靠近屏幕外侧，旋转对称表面微结构单元的效果明显好于水平表面微结构单元。为了获得更好的效果，也可以使旋转对称的各表面微结构单元中第一斜面的倾斜角δ随着距离对称轴线的距离的增大而逐渐增大。
此外，来自超短焦投影机的投影光线透过表面微结构层14入射至全反射层12，经和全反射层12的反射后，再透过表面微结构层14出射。因此，表面微结构单元的第一斜面的上述倾斜角度δ显然会影响微结构单元中的两个倾斜平面的倾斜角度的设定。如图16所示，假定表面微结 构单元的第一斜面相对于屏幕平面的倾斜角度δ不变，入射的投影光线和出射的投影光线与水平方向的夹角分别为ε和η，屏幕外部的介质(一般情况下，空气)折射率为n0。在此情况下，容易推导出表面微结构单元的第一斜面的表面法线与水平方向的夹角也为δ。此外，根据光学原理和表面折射公式可以计算出在折射率为n1的上述微结构层121中的如前文中所述的入射光线和反射光线与水平方向的夹角α和β与δ、ε和η之间的关系满足如下公式：
Figure PCTCN2017114726-appb-000007
Figure PCTCN2017114726-appb-000008
根据上述公式(9)和(10)可知，为了不对全反射层12的倾斜平面的设置产生不利影响，倾斜角δ的取值范围应当在0＜δ＜50的范围内。
此外，可以对表面微结构单元的第一斜面和第二斜面通过喷砂、化学腐蚀或其它的工艺进行表面粗糙化，从而使表面微结构层14能够在降低屏幕表面的菲涅尔损耗的同时，兼具扩大屏幕的视场范围的功能。
需要说明的是，在本文此部分中详细说明的表面微结构层14不仅适用于上述的设置有全反射层12的根据本发明优选实施例的投影屏幕10，而是如前文所述地，可以适用于使用现有技术中的反射层的投影屏幕。换言之，本发明的最主要的发明目的在于减小大入射角入射的投影光线在投影屏幕表面的菲涅尔反射率，从而提高屏幕的光学效率。
尽管在上面已经参照附图说明了根据本发明的发光设备，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 (18)

  1. 一种投影屏幕，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，
    所述投影屏幕包括从所述投影光线的入射侧依次布置的表面微结构层、光扩散层和光反射层，其中，
    所述光反射层用于将入射的所述投影光线反射至观看者的所述视场范围内，所述光扩散层用于增大出射的光线的发散角，并且
    所述表面微结构层包括多个表面微结构单元，多个所述表面微结构单元在所述投影屏幕的平面内相对于所述投影屏幕的垂直中线以线对称的方式周期性排布，各所述表面微结构单元包括相交的第一斜面和第二斜面。
  2. 根据权利要求1所述的投影屏幕，其特征在于，所述第一斜面相对于与所述投影屏幕平行的平面的倾斜角小于或等于所述第二斜面相对于与所述投影屏幕平行的平面的倾斜角。
  3. 根据权利要求1所述的投影屏幕，其特征在于，所述第一斜面相对于与所述投影屏幕平行的平面的倾斜角δ的范围为0＜δ＜50。
  4. 根据权利要求1至3中任一项所述的投影屏幕，其特征在于，所述第一斜面和所述第二斜面沿着水平方向延伸，并且各所述表面微结构单元沿着垂直方向周期性排布。
  5. 根据权利要求4所述的投影屏幕，其特征在于，位于屏幕上方的所述表面微结构单元的所述第一斜面的所述倾斜角大于位于屏幕下方的所述表面微结构单元的所述第一斜面的所述倾斜角。
  6. 根据权利要求1至3中任一项所述的投影屏幕，其特征在于，所述第一斜面和所述第二斜面沿着垂直方向延伸，并且各所述表面微结构 单元沿着水平方向周期性排布。
  7. 根据权利要求6所述的投影屏幕，其特征在于，位于屏幕外侧的所述表面微结构单元的所述第一斜面的所述倾斜角大于位于屏幕内侧的所述表面微结构单元的所述第一斜面的所述倾斜角。
  8. 根据权利要求1至3中任一项所述的投影屏幕，其特征在于，各所述表面微结构单元是以旋转对称的方式布置的，并且各所述表面微结构单元的旋转中心轴线垂直于所述投影屏幕的平面且经过所述投影机的镜头的中心点。
  9. 根据权利要求8所述的投影屏幕，其特征在于，各所述表面微结构单元中的所述第一斜面的所述倾斜角随着到所述旋转中心轴线的距离增大而逐渐增大。
  10. 根据权利要求1至3中任一项所述的投影屏幕，其特征在于，所述第一斜面和所述第二斜面经过表面粗糙化处理。
  11. 根据权利要求1至3中任一项所述的投影屏幕，其特征在于，所述反射层至少包括位于所述光扩散层侧的微结构层和位于所述光吸收层侧的内侧层，所述微结构层的折射率大于所述内侧层的折射率，所述微结构层上设置多个微结构单元，多个所述微结构单元在所述反射层的平面内连续延伸并且旋转对称，各所述微结构单元，，其中每个微结构单元包括的两个相交平面被设置为使得所述投影光线连续在所述两个相交平面处发生全反射。
  12. 根据权利要求11所述的投影屏幕，其特征在于，各所述微结构单元的所述微结构层设置成旋转对称的全反射棱镜，所述两个相交平面与平行于所述投影屏幕的平面的夹角分别为θ1和θ2，且θ1和θ2满足关系：θ1+θ2＜90。
  13. 根据权利要求12所述的投影屏幕，其特征在于，在多个所述微结构单元中，所述θ1具有不同的角度且所述θ2均等于45度。
  14. 根据权利要求12所述的投影屏幕，其特征在于，在多个所述微结构单元中，所述θ1具有不同的角度，并且所述θ2也具有不同的角度。
  15. 根据权利要求11所述的投影屏幕，其特征在于，所述第一材料层的折射率n1和所述内侧层的折射率n2满足关系：n2<n1-0.2。
  16. 根据权利要求11所述的投影屏幕，其特征在于，所述投影屏幕还包括位于所述光反射层的背侧的光吸收层。
  17. 一种投影系统，所述系统包括如权利要求1至16中任一项所述的投影屏幕以及所述投影机。
  18. 如权利要求17所述的投影系统，其特征在于，所述投影机是位于所述投影屏幕下方的超短焦投影机。
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