WO2021208941A1 - 基于二维特征的反射式几何全息膜及其制备方法和应用 - Google Patents

基于二维特征的反射式几何全息膜及其制备方法和应用 Download PDF

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Publication number
WO2021208941A1
WO2021208941A1 PCT/CN2021/087143 CN2021087143W WO2021208941A1 WO 2021208941 A1 WO2021208941 A1 WO 2021208941A1 CN 2021087143 W CN2021087143 W CN 2021087143W WO 2021208941 A1 WO2021208941 A1 WO 2021208941A1
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Prior art keywords
film
reflective
elementary
columnar
dimensional features
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PCT/CN2021/087143
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English (en)
French (fr)
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王广军
余为伟
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荆门市探梦科技有限公司
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Priority claimed from CN202010303256.5A external-priority patent/CN111338016B/zh
Priority claimed from CN202020572746.0U external-priority patent/CN211577471U/zh
Application filed by 荆门市探梦科技有限公司 filed Critical 荆门市探梦科技有限公司
Publication of WO2021208941A1 publication Critical patent/WO2021208941A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/32—Holograms used as optical elements

Definitions

  • the invention relates to the field of 3D display, in particular to a reflective geometric holographic film based on two-dimensional features, and a preparation method and application thereof.
  • the 3D display technology that can display three-dimensional images in space will be the most important display technology in future life.
  • the mainstream 3D display is still a pseudo 3D display technology based on stereoscopic image pairing based on binocular parallax.
  • This kind of display method itself has many drawbacks, and at the same time it can cause problems such as user's visual fatigue, and it is impossible to become the mainstream display technology in the future.
  • the display method that can form a real three-dimensional picture in the air and can display the three-dimensional picture in the most realistic way is the trend of future display technology development.
  • the solution based on retroreflection and the beam splitter can realize the floating display of the picture.
  • this kind of technology usually requires the use of a micro-structured screen containing a series of very fine three-dimensional features.
  • the prior art contains a series of triangular pyramid light reflection screens. Because the microstructures of these three-dimensional features are very fine, it is very difficult for processing to arrange countless three-dimensional feature microstructures evenly and densely on one screen, and the processing accuracy is very high. It is difficult to guarantee, processing efficiency and yield are difficult to guarantee.
  • the publication number CN108269511A is an aerial floating display system.
  • the application discloses a two-dimensional planar air imaging scheme, and discloses a retroreflective right-angled triangular prism array, which includes a series of right-angled triangular prism light reflecting screens, This right-angled triangular prism can only realize the retroreflective imaging function in the plane.
  • the retroreflective function cannot be realized, and other optical modules are needed to modulate the light to realize the retroreflective imaging.
  • the above-mentioned right-angled triangular prism arrays are usually processed with hard optical materials, and problems such as breakage and residual stress are prone to occur during the processing of hard materials, resulting in low product yield and unable to meet the needs of folding, winding and storage. .
  • a reflective geometric holographic film based on two-dimensional features and a preparation method and application thereof are provided.
  • the product contains a A series of reflective geometric holographic films with cylindrical elementary prisms with a right-angled triangle cross section to realize light retro-reflective imaging, so that light irradiated on the reflective geometric holographic film at any angle can be retro-reflected and imaged without other optical modules for modulation. 3D imaging can be performed directly.
  • the present invention proposes a reflective geometric holographic film based on two-dimensional features, including a primitive film and a plurality of columnar primitive prisms arrayed on the surface of the primitive film and having a right triangle in cross section. Retroreflect the light in contrast to it;
  • the surface where the hypotenuse of the cross-section of the columnar elementary prism is located is attached to the surface of the elementary film, and a plurality of transparent layers and reflective layers arranged alternately are arranged inside the elementary film and along the length direction of the columnar elementary prism;
  • a reflective film is provided on the slope where the right-angled side of the cross section of the columnar element prism is located for specular reflection of light;
  • the cross-section of the columnar element prism is the right angle included in the right triangle, and the error range of the angle formed by the transparent layer and the reflective layer and the length direction of the columnar element prism is within ⁇ 5°.
  • the length of the hypotenuse of the right triangle of the cross section of the columnar element prism is a, a ⁇ 2 mm.
  • cross section of the columnar element prism is an isosceles right triangle.
  • end face of the columnar elementary prism and/or the end face of the elementary film parallel to the transparent layer is also provided with a reflective film.
  • the reflective geometric holographic film based on two-dimensional features is a flexible film.
  • the horizontal clamping and sagging length of the two-dimensional feature-based reflective geometric holographic film is Lcm, and the number of foldable times is n, which satisfies:
  • the horizontal clamping and sagging length of the two-dimensional feature-based reflective geometric holographic film is Lcm, and the number of foldable times is n, which satisfies: n*L ⁇ 28.
  • the bottom surface of the elementary film and the reflective film are respectively provided with protective films, wherein the protective film provided on the bottom surface of the elementary film is a transparent protective film.
  • the present invention also provides a method for preparing the above-mentioned two-dimensional feature-based reflective geometric holographic film, which includes the following steps:
  • a reflective film is plated on the end face of the columnar elementary prism and the slope where the right-angle side of the cross section is located, and a reflective geometric holographic film based on two-dimensional features can be obtained.
  • step 2) is replaced by the following method: first cut the transparent film into a number of columnar elementary prisms corresponding to the elementary film, and then bond the columnar elementary prisms to the substrate in a direction perpendicular to the transparent layer and the reflective layer.
  • the error range of the bonding direction is within ⁇ 5°.
  • the method further includes: adhering a transparent protective film on the bottom surface of the elementary film.
  • the method further includes: adhering a protective film on the zigzag undulating surface provided with the reflective film.
  • the present invention also provides the application of the two-dimensional feature-based reflective geometric holographic film prepared by the above-mentioned two-dimensional feature-based reflective geometric holographic film preparation method in a reflective geometric holographic display system.
  • Figure 1 is a schematic diagram of the reflected light path of light on a mutually perpendicular surface, that is, a right-angle reflecting wall.
  • Fig. 2 is a schematic structural diagram of the reflective geometric holographic film based on two-dimensional features of the present invention after a part of the reflective film 3 is hidden.
  • Figure 3 is a front view of Figure 2
  • Figure 4 is a diagram showing the retroreflected light path of a single columnar elementary prism 2 and elementary film 1 to any light that is not parallel to its cross section.
  • Figure 5 is a system schematic diagram of a reflective geometric holographic display system
  • horizontal does not mean that the component is required to be absolutely horizontal or overhanging, but may be slightly inclined.
  • horizontal only means that its direction is more horizontal than “vertical”, and it does not mean that the structure must be completely horizontal, but can be slightly inclined.
  • the present invention proposes a reflective geometric holographic film based on two-dimensional features, including a primitive film 1 and a number of arrays arranged on the surface of the primitive film 1, the cross section is Right-angled triangular columnar elementary prism 2, used to contrast the light of any angle on it for retroreflecting;
  • the surface where the hypotenuse of the cross section of the columnar elementary prism 2 is located is attached to the surface of the elementary film 1.
  • a number of transparent layers arranged alternately are arranged inside the elementary film 1 and along the length of the columnar elementary prism 2. 11 and reflective layer 12;
  • the bottom surface of the elementary film 1 is the light incident surface, the reflective layer 12 and the oblique surface 21 where the right-angle side of the cross section of the cylindrical element prism 2 is located is the reflecting surface, and the oblique surface 21 where the right-angle side of the cross-section of the cylindrical element prism 2 is located is used for Specular reflection of light.
  • the end surface of the elementary film 1 parallel to the transparent layer 11 and the end surface of the columnar elementary prism 2 can also be reflective surfaces, and a reflective film 3 that can reflect light can also be provided on it. It should be noted that, if during the processing When the end surface of the end surface of the elementary film 1 parallel to the transparent layer 11 is the reflective layer 12, it is not necessary to plate the reflective film 3 on the end surface of the reflective layer 12, because the reflective layer 12 itself has the function of specular reflection of light. Function.
  • microstructure unit has the function of retroreflecting light in space, so if it is densely arranged on a plane Many of these microstructures can retroreflect a large area of incident light.
  • any light that is not parallel to the cross-section of the cylindrical elementary prism 2 from the incident surface hits the reflective layer 12 or the reflective film 3 on the end surface of the cylindrical elementary prism 2, after a single reflection to the adjacent one.
  • the light is reflected to another inclined surface 21, and then through the three reflections of the reflective film 3 coated on the inclined surface 21, the light can be shifted After d, it is reflected back parallel to the direction of the incident light, and the retro-reflected light can be 3D imaged;
  • the allowable error range of the above mentioned angles is within ⁇ 5°, including the right angle of the right triangle of the cross section of the columnar elementary prism 2 and the angle formed by the transparent layer 11 and the reflective layer 12 with the length direction of the columnar elementary prism 2
  • the machining process may not be able to produce a completely ideal geometric shape, and there will be certain errors in the angle, and the vertex cannot be an ideal geometric point.
  • the manufacturing error is relatively small, there will be a slight deviation between the direction of the reflected light and the ideal situation of retroreflection. These deviations cannot be distinguished by the human eye, and the aberrations caused by these errors are also very small, so very good imaging effects can also be achieved.
  • the right angle error of the cross section of the columnar element prism 2 is within ⁇ 5°, the user experience is relatively satisfactory. When it exceeds this range, the user begins to feel that the imaging effect is unacceptable.
  • the same geometric vertex is allowed to be a relatively small rounded corner (for example, the radius is less than 0.1mm), then a better imaging function can also be achieved.
  • the smaller the error the higher the user evaluation, so the error should be minimized during production.
  • the cylindrical elementary prism 2 and the two-dimensional feature-based reflective geometric holographic film of the present invention composed of a series of cylindrical elementary prisms 2 has the function of retroreflecting against any light on it, and can irradiate it.
  • the light on the upper part is offset by a distance d and then retroreflected back, where d ⁇ 2mm, and d is the distance from the intersection of the outgoing light and the bottom surface of the reflective geometric holographic film to the incident light;
  • the hypotenuse length of the right-angled triangle cross-section of the columnar element prism 3 is a, a ⁇ 2mm;
  • the reflective geometric holographic film based on two-dimensional features of the present invention preferably adopts a flexible film made of flexible materials.
  • the screen produced in this way can not only meet the requirements of folding and winding storage, but also based on the characteristics of flexibility. Among them, it is not prone to breakage and residual stress.
  • the flexible material included in the reflective geometric holographic film based on two-dimensional features of the present invention is preferably PMMA film, lPMMA film, PS film, PC film, PE film, styrene acrylonitrile Film, MS film, PET film, PETG film, ABS film, PP film, PA film, SAN film, MS film, MBS film, PES film, CR-39 film, TPX film, HEMA film, F4 film, F3 film, EFP Film, PVF film, PVDF film, EP film, PF film, UP film, cellulose acetate film, nitrocellulose film, EVA film, PE film, PVC film, new amorphous thermoplastic polyester film, amorphous cycloolefin film And any one of modified bisphenol A epoxy resin film.
  • the horizontal clamping and sag length is Lcm
  • the number of folds is n
  • n is the number of folds that can be folded in half.
  • a square sample with an area of 100 cm 2 is taken, and the sample is folded along the center line of the square (or within 1 cm of the center line) into a rectangular shape, and then folded in half with two flat plates
  • the elementary membrane is sandwiched, and a force of not less than 10N is applied, and the pressure is maintained for 5s or more, and then opened (at this time, a half-fold test is completed), and check whether the sample has local micro-cracks or breaks into two pieces along the crease If not, repeat the above test until it has a local microcrack or break into two sections, stop the test, the total number of folds in the test process is recorded as n;
  • L is the length of the horizontal clamp.
  • Test method Take a narrow strip with a width of 5cm ⁇ 0.5cm and a length of about 25cm, and one end of the strip is tightly attached to the horizontal reference table to ensure that the length of the strip extending out of the table is 20cm ⁇ 1cm , And then let it stand until the narrow strip is stable, and measure the vertical height difference between the end of the narrow strip protruding from the desktop and the horizontal reference desktop as the horizontal sag length L;
  • the above test itself is an accelerated test method, which can quickly determine the reliability of the sample during long-term use.
  • the flexible film When the flexible film is applied, it needs to withstand multiple operations such as winding, storing and opening, and it is calculated according to the design service life of 5 years , The entire life cycle requires about 10,000 storage and unfolding actions.
  • the present invention adopts the above-mentioned half-fold test and horizontal clamping sag length test;
  • n*L 9
  • n*L 9
  • the structure will not be damaged when wound up, so the winding screen is also suitable.
  • the prepared elementary film can be wound into a cylindrical shape with a diameter of less than 5 cm, the elementary film will be relatively soft as a whole, and the fracture loss during processing will be small.
  • the elementary membrane can be wound into a cylindrical shape with a diameter of less than 5cm without breaking.
  • n and L can be limited to: n*L ⁇ 28. In this way, it can be applied to most application scenarios and can guarantee a higher product yield. .
  • the flexibility of the holographic film depends greatly on its raw materials, and the flexibility of the holographic film can be adjusted in a wide range by controlling the thickness of the raw material.
  • the test process is still troublesome in actual operation. If the design requirements are not particularly strict, the following very fast way can be used to determine. Generally, it is easier to guarantee the superiority of the flexible material processing process, so the screen application scenario is given priority. Through actual application testing, it is found that for the reel storage screen, when L is greater than twice the innermost radius of the reel, the reel can be realized well.
  • the storage screen form can be designed with L greater than 3 times or even 5 times the innermost radius of the reel in order to leave enough design margin.
  • protective films are respectively provided on the bottom and end surfaces of the element film 1 and the reflective film 3 provided on the inclined surface 21.
  • the bottom surface of the element film 1 is the light incident surface, so the element
  • the protective film provided on the bottom surface of the film 1 is a transparent protective film, and the end surface and the inclined surface 21 are used as a reflective surface, and the protective film provided thereon is not necessarily transparent, which is not limited here.
  • the material of the above-mentioned protective film is preferably a flexible material, such as PMMA film, lPMMA film, PS film, PC film, PE film, styrene acrylonitrile film, MS film, PET film, PETG film, ABS film, PP film, PA film, SAN film, MS film, MBS film, PES film, CR-39 film, TPX film, HEMA film, F4 film, F3 film, EFP film, PVF film, PVDF film, EP film, PF film, UP film, cellulose acetate Any one of film, nitrocellulose film, EVA film, PE film, PVC film, new amorphous thermoplastic polyester film, amorphous cyclic olefin film and modified bisphenol A epoxy resin film;
  • a flexible material such as PMMA film, lPMMA film, PS film, PC film, PE film, styrene acrylonitrile film, MS film, PET film, PETG film, ABS film, PP film, PA film,
  • It can also be rigid, such as plastic film, glass, etc.
  • the present invention also provides a method for preparing the above-mentioned two-dimensional feature-based reflective geometric holographic film, which includes the following steps:
  • a reflective film 3 is plated on the end surface of the columnar element prism 2 and the inclined surface 21 where the right-angle side of the cross section is located, and a reflective geometric holographic film based on two-dimensional features can be obtained.
  • the elementary film 1 used in step 1) may not use a flexible elementary film, and a flexible holographic elementary film and its preparation method according to the publication number CN110794504A can be used with materials that meet the requirements.
  • the preparation method in application can be applied to the present invention when the elementary membrane is prepared.
  • a two-step preparation method can also be used, such as directly arranging one on the surface of the elementary film arranged alternately between the transparent layer and the reflective layer in a direction orthogonal to the interlayer interface in the elementary film.
  • the series of cross-sections are right-angled triangular cylindrical prisms.
  • the surface of the right-angled triangle with the hypotenuse of the cross-section is connected to the primitive film 1, and the surface with the right-angled side is provided with a reflective film 3, which can also realize the function of a reflective holographic film.
  • the transparent film is adhered to the surface of the elementary film 1, and then the transparent film is cut in the direction perpendicular to the transparent layer 11 and the reflective layer 12, and the cross-section of the scrap is 1 mm high isosceles right-angled triangular prism.
  • After cutting Obtain a number of column-shaped elementary prisms 2 with a cross-section of 1mm high isosceles right-angled triangles arrayed on the surface of elementary film 1 and have undulating and jagged films; That is, a reflective geometric holographic film based on two-dimensional characteristics is prepared, and finally a protective film is plated on the reflective film 3 to protect the internal microstructure of the holographic film.
  • a transparent protective film can be plated on the bottom surface of the primitive film before cutting.
  • the holographic film prepared in Example 1 includes a series of isosceles right-angled triangular cylindrical elementary prisms 2 with a cross section of 2 mm hypotenuse. Based on the principle of light path in Figure 1, light enters from the incident surface and then passes through the right-angle reflecting wall. After retroreflecting, the existing offset d will not be greater than the length of the hypotenuse of the cross section 2 mm, that is, d ⁇ 2 mm.
  • a rectangular flexible element film 1 with a thickness of 0.5 mm and a transparent layer 11 and a reflective layer 12 arranged alternately, and a transparent film with a thickness of 1 mm corresponding to the rectangular element film 1, wherein the material of the transparent layer 11 is PC film, the reflective layer 12 is made of aluminum foil reflective film, and the transparent film is PC film;
  • the transparent film is adhered to the surface of the elementary film 1, and then the transparent film is cut in the direction perpendicular to the transparent layer 11 and the reflective layer 12, and the cross section of the scrap is 0.5 mm high isosceles right-angled triangular prism.
  • a reflective film 3 is plated on the end surface of the film and the inclined surface 21, That is, a reflective geometric holographic film based on two-dimensional characteristics is prepared, and finally a protective film is plated on the reflective film 3 to protect the internal microstructure of the holographic film.
  • a transparent protective film can be plated on the bottom surface of the primitive film before cutting.
  • the holographic film prepared in Example 2 includes a series of isosceles right-angled triangular cylindrical elementary prisms 2 with a cross section of 1 mm hypotenuse. Based on the principle of light path in Figure 1, light enters from the incident surface and then passes through the right-angle reflecting wall. When the reflection is retro-reflected, the offset d will not be greater than 1 mm of the hypotenuse of the cross section, that is, d ⁇ 1 mm.
  • the transparent film is adhered to the surface of the elementary film 1, and then the transparent film is cut in the direction perpendicular to the transparent layer 11 and the reflective layer 12, and the cross-section of the scrap is 0.2mm high isosceles right-angled triangular prism.
  • a reflective film 3 is plated on the end surface of the film and the inclined surface 21, That is, a reflective geometric holographic film based on two-dimensional features is prepared, and finally a protective film is plated on the reflective film 3 to protect the internal microstructure of the holographic film.
  • a transparent protective film can be plated on the bottom surface of the primitive film before cutting.
  • the holographic film prepared in Example 3 includes a series of isosceles right-angled triangular cylindrical elementary prisms 2 with a cross section of 0.4 mm hypotenuse. Based on the principle of light path in Figure 1, light enters from the incident surface and then passes through the right-angle reflecting wall. After retroreflecting, the offset d will not be greater than 0.4mm of the hypotenuse of the cross section, that is, d ⁇ 0.4mm.
  • the transparent film is adhered to the surface of the elementary film 1, and then the transparent film is cut in the direction perpendicular to the transparent layer 11 and the reflective layer 12, and the cross-section of the scrap is 0.1mm high isosceles right-angled triangular prism.
  • After cutting Obtain a number of column-shaped elementary prisms 2 with a cross-section of 0.1mm high isosceles right-angled triangles arrayed on the surface of elementary film 1 and have undulating and zigzag-shaped films; That is, a reflective geometric holographic film based on two-dimensional characteristics is prepared, and finally a protective film is plated on the reflective film 3 to protect the internal microstructure of the holographic film.
  • a transparent protective film can be plated on the bottom surface of the primitive film before cutting.
  • the holographic film prepared in Example 4 includes a series of isosceles right-angled triangular cylindrical primitive prisms 2 with a cross section of 0.2 mm hypotenuse. Based on the principle of light path in Figure 1, light enters from the incident surface and then passes through the right-angle reflecting wall. After retroreflecting, the offset d will not be greater than the length of the hypotenuse of the cross section 0.2 mm, that is, d ⁇ 0.2 mm.
  • the above embodiment can also be achieved by first cutting to obtain the intermediate product columnar element prisms 2, and then bonding these columnar element prisms 2 perpendicular to the transparent layer 11 and the reflective layer 12 on the surface of the element film 1.
  • the actual bonding is When, the error range of the bonding direction is within ⁇ 5°.
  • the thickness of the transparent layer 11 of the primitive film 1 is preferably ⁇ 1mm, while d ⁇ 1mm;
  • the thickness of the transparent layer 11 of the elementary film 1 is preferably ⁇ 0.5mm, and d ⁇ 0.5mm;
  • the thickness of the transparent layer 11 is preferably ⁇ 0.3mm, and d ⁇ 0.3mm;
  • the reflective geometric holographic film product based on the two-dimensional feature of the present invention has modulated light, can realize retroreflective imaging, and can realize the retroreflective imaging function without using additional lens elements.
  • the present invention also provides the application of the reflective geometric holographic film based on the two-dimensional feature prepared by the above-mentioned preparation method in a reflective geometric holographic display system, specifically:
  • the reflective geometric holographic display system includes an image source 100, a reflective geometric holographic screen 101, an auxiliary imaging screen 102, a supporting structure 103 and a controller 104;
  • the image source 100 is used to provide a projection screen, and can be an LCD display screen, an LED display screen, a projector, a holographic projector, and other elements capable of generating images, preferably a projector or a holographic projector;
  • the reflective geometric holographic screen 101 is used to retroreflect the light irradiated on it, and the reflective geometric holographic film based on the two-dimensional feature prepared by the present invention is adopted;
  • the auxiliary imaging screen 102 is used for light splitting, and is preferably a screen made of a semi-transparent and semi-reflective material;
  • the supporting structure 103 is matched with the image source 100, the reflective geometric holographic screen 101 and the auxiliary imaging screen 102 respectively, and provides physical structural support for the three;
  • the controller 104 is electrically connected to the image source 100 for controlling the image source 100 to adjust the depth of field and display content of the projected picture;
  • the support structure 103 is a structure that can move or deform, electrically connect the support structure 103 and the controller 104, and the support structure 103 makes a corresponding response based on the control information of the controller 104.
  • the reflective geometric holographic screen 101 and the auxiliary imaging screen 102 respond to actions to realize the relative movement and/or overall movement of the image source 100, the reflective geometric holographic screen 101 and the auxiliary imaging screen 102, so that the visual window of the system always covers the user's eyes, so that the user can watch normally in different directions
  • the support structure 103 is a general prior art, and those skilled in the art can design it according to the actual application space conditions. For example, it can be easily designed by using some hinge structures and structures similar to umbrella shafts.
  • the deformed structure is not specifically limited here;
  • the holographic display system of the present invention further includes an interactive motion capturing unit 105 electrically connected to the controller 104, and the interactive motion capturing unit 105 is used to identify the user's interactive motion and send the user's interactive motion information to the controller 104
  • the controller 104 adjusts the content of the display screen according to the user interaction action information acquired by the received interactive action capture unit 105 to realize the interaction between the user and the screen. Specifically, it can use a camera combined with machine vision technology to recognize the user's gestures to acquire the user.
  • the controller 104 can also control the received interactive actions
  • the user interaction action information acquired by the capture unit 105 is used to adjust the content of the display screen in real time to realize the interaction between the user and the screen, such as controlling the screen to pan according to the pan gesture signal, or controlling the zooming, zooming in, and zooming of the screen according to the corresponding other interactive actions. Push far, touch and other operations;
  • the setting of the interactive motion capture unit 105 has positive significance for application scenarios similar to wearable applications where the user's spatial position relative to the display system is fixed;
  • an eye tracking unit 106 electrically connected to the controller 104 needs to be provided.
  • the positioning information is sent to the controller 104, and the controller 104 controls the support structure 103 to make corresponding action responses according to the received eye positioning information obtained by the eye tracking unit 106 to adjust the image source 100 and the reflective geometric holographic screen
  • the relative position and/or overall spatial position of 101 and/or auxiliary imaging screen 102 keep the user's eyes always in the visible space of the system, so that the user's eyes can always receive projection information even when in motion, and view the picture normally.
  • the interactive motion capture unit 105 and the eye tracking unit 106 can be integrated in the same device, such as using a machine vision camera device.
  • the image source 100 projects a picture, the light is irradiated on the auxiliary imaging screen 102, part of the light directly passes through the auxiliary imaging screen 102, this part of the light will not participate in imaging, and the other part of the light is reflected by the auxiliary imaging screen 102 to the reflective geometric holographic screen 101, and this part of the light is optically transformed by the reflective geometric holographic screen 101, offset by a small distance d, and reflected back in the original direction and transmitted through the auxiliary imaging screen 102, forming an off-screen image that can be observed in space.

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Abstract

一种基于二维特征的反射式几何全息膜及其制备方法和应用，其中，反射式几何全息膜包括基元膜(1)和若干阵列设置在基元膜(1)表面上的、横截面为直角三角形的柱状基元棱镜(2)，柱状基元棱镜(2)横截面的斜边所在的面均与基元膜(1)表面贴合，基元膜(1)内部、沿柱状基元棱镜(2)的长度方向设有若干相间排列的透明层(11)和反射层(12)；柱状基元棱镜(2)横截面的直角边所在的斜面上设置有一层反射膜(3)，柱状基元棱镜(2)横截面包含的直角以及透明层(11)和反射层(12)与柱状基元棱镜(2)的长度方向所成角度的误差范围在±5°以内。通过简单的、基于二维特征的切削和加工，容易实现大规模，再加上基元膜(1)优选地是柔性基元膜，产品优率高，而且柔性特性使得基于二维特征的反射式几何全息膜可以满足折叠、卷绕收纳等需求。

Description

基于二维特征的反射式几何全息膜及其制备方法和应用
本申请要求于2020年04月17日提交中国专利局、申请号为202020572746.0、发明名称为“基于二维特征的反射式几何全息膜”以及于同日提交中国专利局、申请号为202010303256.5、发明名称为“基于二维特征的反射式几何全息膜及其制备方法和应用”的两件中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及3D显示领域，尤其是涉及一种基于二维特征的反射式几何全息膜及其制备方法和应用。
背景技术
能够在空间显示出立体画面的3D显示技术，会是未来生活中最重要的一种显示技术。目前主流的3D显示还是基于双目视差的立体图像对式的伪3D显示技术。这种显示方式本身有很多弊端，同时还会造成用户的视觉疲劳等问题，不可能成为未来的主流显示技术。
能够在空中形成真正的立体画面的显示方式，能够以最真实的方式展示立体画面，是未来显示技术发展的趋势。目前已经有一些技术可以实现在空中悬浮显示画面，例如基于逆反射加上分光镜的方案可以实现画面的悬空显示，但是这类技术通常需要用到含有一系列非常精细三维特征的微结构屏。例如现有技术中含有一系列三角锥的光反射屏，由于这些三维特征的微结构非常精细，在一张屏上均匀密集的布置无数三维特征微结构对于加工而言、难度非常大，加工精度很难保证，加工效率和良品率都难以保证。
公布号为CN108269511A的一种空中悬浮显示系统，该申请公开了一种二维平面空气成像的方案，公开了一种逆反射的直角三角形棱镜阵列，其包括一系列直角三角形棱镜的光反射屏，这种直角三角形棱镜只能实现平面内的逆反射成像功能，光线跟截面不平行时，就无法实现逆反射功能， 需要另外借助其他光学模组来对光线进行调制进而实现逆反射成像。
此外，上述直角三角形棱镜阵列通常会采用硬质的光学材料来加工，而硬质材料加工过程中容易出现破碎以及产生残余应力等问题，造成产品良品率低，无法满足折叠、卷绕收纳等需求。
发明内容
针对上述现有技术的不足，提供一种基于二维特征的反射式几何全息膜及其制备方法和应用，通过对粘接有透明膜的基元膜进行简单的切削和加工，制得包含一系列横截面为直角三角形的柱状基元棱镜的反射式几何全息膜，来实现光线逆反射成像，使得任意角度照射在反射式几何全息膜的光线能逆反射成像，无需其他光学模组进行调制即可直接进行3D成像。
为解决上述技术问题，本发明提出一种基于二维特征的反射式几何全息膜，包括基元膜和若干阵列设置在基元膜表面上的、横截面为直角三角形的柱状基元棱镜，用于对照在其上的光线进行逆反射；
所述柱状基元棱镜横截面的斜边所在的面均与基元膜表面贴合，所述基元膜内部、沿柱状基元棱镜的长度方向设有若干相间排列的透明层和反射层；
所述柱状基元棱镜横截面的直角边所在的斜面上设置有一层反射膜，用于对光线进行镜面反射；
所述柱状基元棱镜横截面为直角三角形内包含的直角以及透明层和反射层与柱状基元棱镜的长度方向所成角度的误差范围在±5°以内。
进一步地，所述柱状基元棱镜横截面的直角三角形的斜边长度为a，a≤2㎜。
进一步地，所述柱状基元棱镜的横截面为等腰直角三角形。
进一步地，所述柱状基元棱镜的端面和/或基元膜与透明层平行的端面也设置有一层反射膜。
进一步地，所述基于二维特征的反射式几何全息膜为柔性膜。
进一步地，所述基于二维特征的反射式几何全息膜的水平夹持下垂长度为L㎝，可对折次数为n，满足：
L≥5或者n*L>9。
进一步地，所述基于二维特征的反射式几何全息膜的水平夹持下垂长度为L㎝，可对折次数为n，满足：n*L≥28。
进一步地，所述基元膜的底面和反射膜上分别设有保护膜，其中所述基元膜的底面上设有的保护膜为透明保护膜。
本发明还提供上述的基于二维特征的反射式几何全息膜的制备方法，包括以下步骤：
1)准备一张透明层与反射层相间排列的基元膜以及一张与基元膜对应透明膜；
2)将透明膜粘接于基元膜的表面，沿垂直于透明层与反射层的方向上对透明膜进行切削，形成一层是基元膜、另一层是阵列的横截面为直角三角形的柱状基元棱镜排列形成的起伏锯齿状表面的膜，切削方向的误差范围在±5°以内；
3)在柱状基元棱镜的端面以及横截面的直角边所在的斜面上镀一层反射膜，即可获得基于二维特征的反射式几何全息膜。
进一步地，步骤2)用以下方法替代：先将透明膜切削成若干个与基元膜对应的柱状基元棱镜，再将柱状基元棱镜沿垂直于透明层与反射层的方向粘接在基元膜的表面，粘接方向的误差范围在±5°以内。
进一步地，在步骤2)之前或者之后还包括：在基元膜的底面上粘接一层透明保护膜。
进一步地，在步骤3)之后还包括：在设置有反射膜的锯齿状起伏表面粘接一层保护膜。
本发明还提供上述的基于二维特征的反射式几何全息膜的制备方法制备的基于二维特征的反射式几何全息膜于反射式几何全息显示系统的应用。
与现有技术相比，本发明的优点在于：
1、基于二维特征容易实现大规模、高精度反射式全息膜的制备，生产速度快、产品优率高、工艺成本低、成像质量优异；
2、无需借助额外透镜元件即可实现逆反射成像功能；
3、可实现柔性屏幕制备，应用形态灵活。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明中记载的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为光线在相互垂直的表面即直角反射壁的反射光路示意图，
图2为隐藏了部分的反射膜3后，本发明所述的基于二维特征的反射式几何全息膜的结构示意图，
图3为图2的正视图，
图4为单个柱状基元棱镜2与基元膜1对与其横截面不平行的任意光线的逆反射光路图，
图5为反射式几何全息显示系统的系统示意图，
附图标记如下：
基元膜1，透明层11，反射层12，柱状基元棱镜2，斜面21，反射膜3，图像源100，反射式几何全息屏101，辅助成像屏102，支持结构103，控制器104，交互动作捕捉单元105，人眼跟踪单元106。
具体实施方式
为了使本领域技术人员更好地理解本发明的技术方案，下面结合附图对本发明进行详细描述，本部分的描述仅是示范性和解释性，不应对本发明的保护范围有任何的限制作用。
应注意到：相似的标号和字母在下面的附图中表示类似项，因此，一旦某一项在一个附图中被定义，则在随后的附图中不需要对其进行进一步定义和解释。
需要说明的是，术语“中心”、“上”、“下”、“左”、“右”、“竖直”、“水平”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，或者是该发明产品使用时惯常摆放的方位或位置关系，仅是为了便 于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。此外，术语“第一”、“第二”、“第三”等仅用于区分描述，而不能理解为指示或暗示相对重要性。
此外，术语“水平”、“竖直”、“悬垂”等术语并不表示要求部件绝对水平或悬垂，而是可以稍微倾斜。如“水平”仅仅是指其方向相对“竖直”而言更加水平，并不是表示该结构一定要完全水平，而是可以稍微倾斜。
在本发明的描述中，还需要说明的是，除非另有明确的规定和限定，术语“设置”、“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以具体情况理解上述术语在本发明中的具体含义。
首先，参考图1，一条光线照射在形成直角的两个反射壁上时，经过两次反射后，出射光线会沿着平行于入射光线的方向传播。当直角反射壁足够小时，出射光线和入射光线之间的距离也会非常小，小到人眼无法分辨，视觉上就像光线原路返回一样。当然，二维平面内直角反射壁只能使平面内的光线进行逆反射，如果能够在空间中形成一个直角三棱锥结构的反射壁，就可以对空间中的光线进行逆反射。
参照图2至图4，基于上述的光路原理，本发明提出一种基于二维特征的反射式几何全息膜，包括基元膜1和若干阵列设置在基元膜1表面上的、横截面为直角三角形的柱状基元棱镜2，用于对照在其上的任意角度的光线进行逆反射；
如图2，柱状基元棱镜2横截面的斜边所在的面均与基元膜1表面贴合，基元膜1内部、沿柱状基元棱镜2的长度方向设有若干相间排列的透明层11和反射层12；
基元膜1的底面为光线入射面，反射层12以及柱状基元棱镜2横截面的直角边所在的斜面21为反射面，柱状基元棱镜2横截面的直角边所在的斜面21，用于对光线进行镜面反射。
基元膜1与透明层11平行的端面和柱状基元棱镜2的端面也可以是反 射面，其上也可以设置一层能够反射光线的反射膜3，需要说明的是，如果在加工过程中，基元膜1与透明层11平行的端面的端面为反射层12时，是没有必要在该反射层12的端面上镀反射膜3的，因为反射层12本身就具有对光线进行镜面反射的功能。
单个横截面为直角三角形的柱状基元棱镜2与基元膜1的组合具有多个直角反射壁，因此这种微结构单元具有对空间的光线进行逆反射的功能，所以如果一个平面上密集布置很多这种微结构，就可以对大面积的入射光进行逆反射。
如图4所示，任意与柱状基元棱镜2的横截面不平行的光线从入射面射到反射层12或者柱状基元棱镜2端面的反射膜3上时，经过一次反射至相邻的一个斜面21上，经过该斜面21镀的反射膜3的二次反射，将光线反射到另一个斜面21上，再经过该斜面21上镀的反射膜3的三次反射，即可实现将光线偏移d后平行于入射光的方向反射回去，这些逆反射回去的光线可以进行3D成像；
上述涉及到的角度的所允许的误差范围在±5°以内，包括柱状基元棱镜2横截面的直角三角形的直角以及透明层11和反射层12与柱状基元棱镜2的长度方向所成角度，虽然以上原理是基于理想几何形状来实现的，但是实际情况下，加工过程可能无法制造出完全理想的几何形状，角度也会存在一定的误差，顶点也不可能是一个理想的几何点而是一个半径非常小的圆角。当生产制造误差比较小时，反射光的方向跟逆反射理想的情况发生微小偏差，这些偏差人眼无法分辨，由这些误差带来的像差也非常小，因此同样可以实现非常好的成像效果。
比如柱状基元棱镜2横截面的直角误差在±5°之内时，用户体验相对比较满意，当超出这个范围后，用户开始觉得成像效果无法接受。同样几何顶点允许是一个比较小的圆角(比如半径小于0.1mm)，那么同样可以实现比较好的成像功能。当然误差越小用户评价越高，所以生产时要尽量降低误差。
当然误差越小用户评价越高，所以生产时要尽量降低误差。类似的加工误差对于切削方向和粘接方向同样适用。
具体应用时，客厅应用的角度误差在±2.5°以内时，用户体验相对比 较满意；
桌面应用的角度误差在±1°以内时，用户体验相对比较满意；
移动终端应用的角度误差在±0.5°以内时，用户体验相对比较满意。
而对于平行于柱状基元棱镜2横截面的入射光，按照图1的光路原理经过两斜面21的两次反射即可实现光想逆反射3D成像。
因此该柱状基元棱镜2以及由一系列柱状基元棱镜2构成的本发明的基于二维特征的反射式几何全息膜具有对照在其上的任意光线进行逆反射的功能，可以把照射到其上的光线偏移距离d后逆反射回去，其中d≤2㎜，d为出射光线与反射式几何全息膜底面的交点到入射光线的距离；
优选的是，如图3，上述柱状基元棱镜3的直角三角形横截面的斜边长度为a，a≤2㎜；
考虑到柔性膜有相对更加灵活的应用形态，适用范围会更加广泛，同时柔性材料的加工过程不会因为磕碰、跌落、震动等原因损坏。因此，本发明的基于二维特征的反射式几何全息膜优选采用柔性材料制成的柔性膜，这样做出来的屏不仅可以满足折叠、卷绕收纳需求，而且基于柔性的特性，在生产加工过程中，不易容易出现破碎以及产生残余应力等问题，本发明的基于二维特征的反射式几何全息膜包括的柔性材料优选PMMA膜、lPMMA膜、PS膜、PC膜、PE膜、苯乙烯丙烯腈膜、MS膜、PET膜、PETG膜、ABS膜、PP膜、PA膜、SAN膜、MS膜、MBS膜、PES膜、CR-39膜、TPX膜、HEMA膜、F4膜、F3膜、EFP膜、PVF膜、PVDF膜、EP膜、PF膜、UP膜、醋酸纤维素膜、硝酸纤维素膜、EVA膜、PE膜、PVC膜、新型非晶型热塑性聚酯膜、无定形环烯烃膜和改性双酚A环氧树脂膜中的任意一种。
为了进一步保证可靠性，同时需要满足：其水平夹持下垂长度为L㎝，可对折次数为n，满足：L≥5或者n*L>9。
其中n为可对折次数，测试时取面积为100㎝ 2的正方形小样，将小样沿着正方形中间线位置(或者中线位置附近1㎝范围内)对折成长方形，然后用两块平板将对折后的基元膜夹在中间，施加不小于10N的力，加压维持时间大于或者等于5s，然后打开(此时完成一次对折测试)，检查小样是否产生局部微裂纹或者沿折痕断开成两截，如果没有，重复上述测试 直到其产生局部微裂纹或者断开为两截，停止测试，测试过程总共折叠次数记为n；
其中L为水平夹持下垂长度，测试方法：取宽度5㎝±0.5㎝，长度约25㎝的窄条，一端紧贴在水平基准桌面上，保证窄条伸出桌面长度为20㎝±1㎝，然后静置待窄条稳定后测量窄条伸出桌面一端的端点与水平基准桌面的垂直高度差记为水平下垂长度L；
上述的测试本身是一种加速测试手段，可以快速判断样品在长期使用过程中的可靠性，柔性薄膜在应用时，需要承受多次的卷绕收纳和打开等操作，按照设计5年使用寿命计算，整个生命周期需要收纳、展开动作大约10000次，为了加速评估使用可靠性，本发明采用上述对折测试和水平夹持下垂长度测试；
当n*L>9时，n越大表明基元膜的极限弯折曲率半径越小，抗折断能力越强，同时L越大说明基元膜的柔性越好，越不容易因为卷绕破坏膜的结构，实验发现n*L＝9时基本等效10000次开合测试，满足最小设计寿命需求，过小的话，容易在产品的使用周期内出现质量问题，降低客户体验；
在实际应用时，也可以使用一些无法完成无安全对折，但是卷绕起来却不会破坏结构，所以也适用卷绕屏。对于这类材料，只要满足了制备的基元膜可以卷绕成直径小于5㎝的圆筒状，基元膜整体也会比较柔顺，加工过程破裂损失也较小。通常L≥5㎝时，基元膜可以卷绕成直径小于5㎝的圆筒状而不发生断裂。
下表是验证时的一些数据：
Figure PCTCN2021087143-appb-000001
进一步地，结合上表中内容，在具体实践中可以将n和L的关系限定为：n*L≥28，如此，即可以适用于大多数的应用场景，并能够保证较高的产品良率。
补充说明的是，全息膜的柔性特征极大程度取决于其原材料，通过控制原材料的厚度可以大范围的调节全息膜的柔性特征。这些可以通过简单实验获取相应数据，这里不做赘述。
虽然上述加速测试方法可以给出一个比较合适的设计指导，但是实际操作起来测试过程还是比较麻烦，对于设计要求不是特别严格的情况下，还可以通过如下非常快速的方式进行判定。通常，对于柔性材料加工过程的优率比较容易保证，所以优先考虑屏幕应用场景，通过实际应用测试发现对于卷轴收纳屏幕，当L大于两倍的卷轴最内层半径时即可很好的实现卷轴收纳屏形态，当然为了留出足够的设计余量也可以取L大于3倍甚至5倍卷轴最内层半径进行设计。
为了对内部的微结构进行保护，在基元膜1的底面和端面以及斜面21上设置有的反射膜3上分别设有保护膜，其中基元膜1的底面为光线入射面，因此基元膜1的底面上设有的保护膜为透明保护膜，而端面以及斜面21作为反射面，其上设有的保护膜不一定是透明的，这里不作限定。
上述的保护膜的材质优选柔性材质，如PMMA膜、lPMMA膜、PS膜、PC膜、PE膜、苯乙烯丙烯腈膜、MS膜、PET膜、PETG膜、ABS膜、PP膜、PA膜、SAN膜、MS膜、MBS膜、PES膜、CR-39膜、TPX膜、HEMA膜、F4膜、F3膜、EFP膜、PVF膜、PVDF膜、EP膜、PF膜、UP膜、醋酸纤维素膜、硝酸纤维素膜、EVA膜、PE膜、PVC膜、新型非晶型热塑性聚酯膜、无定形环烯烃膜和改性双酚A环氧树脂膜中的任意一种；
也可以是刚性的，如塑料膜、玻璃等。
本发明还提供上述基于二维特征的反射式几何全息膜的制备方法，包括以下步骤：
1)准备一张透明层11与反射层12相间排列的基元膜1以及一张与基元膜1对应透明膜，优选公开号CN110794504A的一种柔性全息基元膜及其制备方法和应用中的柔性全息基元膜；
2)将透明膜粘接于基元膜1的表面，沿垂直于透明层11与反射层12的方向上对透明膜进行切削，形成一层是基元膜1、另一层是阵列的横截面为直角三角形的柱状基元棱镜2排列形成的起伏锯齿状表面的膜；
3)在柱状基元棱镜2的端面以及横截面的直角边所在的斜面21上镀一层反射膜3，即可获得基于二维特征的反射式几何全息膜。
需要说明的是，根据实际需求，步骤1)中采用的基元膜1也可以不使用柔性基元膜，用符合需求的材料按照公开号CN110794504A的一种柔性全息基元膜及其制备方法和应用中的制备方法制备出基元膜即可应用于本发明。
除了使用上述了制备方法外，还可以通过两步制备方法，比如直接在由透明层和反射层相间排列的基元膜表面上正交于基元膜内的层间界面的方向上排布一系列横截面为直角三角形的柱状棱镜，横截面直角三角形斜边所在的面与基元膜1相接，直角边所在的面设有反射膜3，同样可以实现反射式全息膜的功能。具体为：先准备一张透明层11与反射层12相间排列的基元膜1以及一张与基元膜1对应透明膜(或者是已切削好的若干与基元膜1对应的柱状基元棱镜2)，然后将透明膜切削成若干个与基元膜1对应的柱状基元棱镜2，再将柱状基元棱镜2沿垂直于(实际加工过程允许存在一定误差，优选±5°的误差范围)透明层11与反射层12的方向阵列粘接在基元膜1的表面，再进行上述方法中的镀膜工艺。
下面结合实施例对本发明作进一步说明，需要说明的，以下实施例是对本发明的具体说明，不是对本发明的限制：
实施例1
准备一张厚度为1㎜、透明层11与反射层12相间排列的矩形柔性基元膜1和一张厚度为1mm的、与矩形基元膜1对应的透明膜，其中透明层11的材质为PC膜，反射层12材质为铝箔反射膜，透明膜采用PC膜；
将透明膜粘接于基元膜1表面，然后沿垂直于透明层11与反射层12的方向上对透明膜进行切削，切削出废料的截面为高1㎜的等腰直角三角形棱柱，切削后得到若干横截面为高1㎜等腰直角三角形的柱状基元棱镜2阵列于基元膜1表面、具有起伏锯齿状的膜；然后在上述膜的端面以及斜面21上镀一层反射膜3，即制得基于二维特征的反射式几何全息膜，最 后在反射膜3上再镀一层保护膜来保护全息膜的内部微结构。为了增加膜的强度，可以在切削之前，在基元膜的底面上镀一层透明保护膜。
实施例1制得的全息膜包括一系列的横截面为斜边2㎜的等腰直角三角形的柱状基元棱镜2，基于图1的光路原理，光线从入射面射进来，然后经过直角反射壁逆反射回去，存在的偏移量d不会大于横截面的斜边长2㎜，即d≤2㎜。
实施例2
准备一张厚度为0.5㎜、透明层11与反射层12相间排列的矩形柔性基元膜1和一张厚度为1mm的、与矩形基元膜1对应的透明膜，其中透明层11的材质为PC膜，反射层12材质为铝箔反射膜，透明膜采用PC膜；
将透明膜粘接于基元膜1表面，然后沿垂直于透明层11与反射层12的方向上对透明膜进行切削，切削出废料的截面为高0.5㎜的等腰直角三角形棱柱，切削后得到若干横截面为高0.5㎜等腰直角三角形的柱状基元棱镜2阵列于基元膜1表面、具有起伏锯齿状的膜；然后在上述膜的端面以及斜面21上镀一层反射膜3，即制得基于二维特征的反射式几何全息膜，最后在反射膜3上再镀一层保护膜来保护全息膜的内部微结构。为了增加膜的强度，可以在切削之前，在基元膜的底面上镀一层透明保护膜。
实施例2制得的全息膜包括一系列的横截面为斜边1㎜的等腰直角三角形的柱状基元棱镜2，基于图1的光路原理，光线从入射面射进来，然后经过直角反射壁反射逆反射回去，存在的偏移量d不会大于横截面的斜边长1㎜，即d≤1㎜。
实施例3
准备一张厚度为0.2㎜、透明层11与反射层12相间排列的矩形柔性基元膜1和一张厚度为1mm的、与矩形基元膜1对应的透明膜，其中透明层11的材质为PC膜，反射层12材质为铝箔反射膜，透明膜采用PC膜；
将透明膜粘接于基元膜1表面，然后沿垂直于透明层11与反射层12的方向上对透明膜进行切削，切削出废料的截面为高0.2㎜的等腰直角三角形棱柱，切削后得到若干横截面为高0.2㎜等腰直角三角形的柱状基元棱镜2阵列于基元膜1表面、具有起伏锯齿状的膜；然后在上述膜的端面以及斜面21上镀一层反射膜3，即制得基于二维特征的反射式几何全息膜， 最后在反射膜3上再镀一层保护膜来保护全息膜的内部微结构。为了增加膜的强度，可以在切削之前，在基元膜的底面上镀一层透明保护膜。
实施例3制得的全息膜包括一系列的横截面为斜边0.4㎜的等腰直角三角形的柱状基元棱镜2，基于图1的光路原理，光线从入射面射进来，然后经过直角反射壁逆反射回去，存在的偏移量d不会大于横截面的斜边长0.4㎜，即d≤0.4㎜。
实施例4
准备一张厚度为0.1㎜、透明层11与反射层12相间排列的矩形柔性基元膜1和一张厚度为1mm的、与矩形基元膜1对应的透明膜，其中透明层11的材质为PC膜，反射层12材质为铝箔反射膜，透明膜采用PC膜；
将透明膜粘接于基元膜1表面，然后沿垂直于透明层11与反射层12的方向上对透明膜进行切削，切削出废料的截面为高0.1㎜的等腰直角三角形棱柱，切削后得到若干横截面为高0.1㎜等腰直角三角形的柱状基元棱镜2阵列于基元膜1表面、具有起伏锯齿状的膜；然后在上述膜的端面以及斜面21上镀一层反射膜3，即制得基于二维特征的反射式几何全息膜，最后在反射膜3上再镀一层保护膜来保护全息膜的内部微结构。为了增加膜的强度，可以在切削之前，在基元膜的底面上镀一层透明保护膜。
实施例4制得的全息膜包括一系列的横截面为斜边0.2㎜的等腰直角三角形的柱状基元棱镜2，基于图1的光路原理，光线从入射面射进来，然后经过直角反射壁逆反射回去，存在的偏移量d不会大于横截面的斜边长0.2㎜，即d≤0.2㎜。
上述实施例也可以采用先切削得到中间产品柱状基元棱镜2，然后将这些柱状基元棱镜2垂直于透明层11和反射层12阵列粘接在基元膜1的表面来实现，实际粘接时，粘接方向的误差范围在±5°以内。
具体应用时，通常显示设备距离人眼越近需要的分辨率也就越高，比如对于类似桌面显示优选基元膜1的透明层11厚度≤1mm，同时d≤1㎜；
对于显示要求更高的设备优选基元膜1的透明层11厚度≤0.5mm，同时d≤0.5㎜；
对于显示细节要求更高的设备优选透明层11厚度≤0.3mm，同时d ≤0.3㎜；
通过粘接于基元膜1表面的透明膜进行切削或者是先切削得到横截面为直角三角形的柱状基元棱镜2，再垂直于透明层11和反射层12的方向阵列粘接于基元膜1表面，均是基于二维特征的切削加工，操作简单，容易实现大规模、高精度生产，生产速度快，工艺成本低，再加上基元膜优选地是柔性基元膜，在切削加工过程中不会出现硬质材料加工过程中经常出现的破碎以及产生残余应力等问题，产品优率高，而且柔性的特性使得本发明的产品可以满足折叠、卷绕收纳等需求；
基于直角反射壁的光路原理，本发明的基于二维特征的反射式几何全息膜产品自身具有调制光线，能够实现逆反射成像，无需借助额外透镜元件即可实现逆反射成像功能。
本发明还提供了上述制备方法制备的基于二维特征的反射式几何全息膜于反射式几何全息显示系统的应用，具体为：
如图5，反射式几何全息显示系统包括图像源100、反射式几何全息屏101、辅助成像屏102、支持结构103和控制器104；
图像源100用于提供投影画面，可以采LCD显示屏、LED显示屏、投影仪、全息投影仪等能够生成图像的元件，优选投影仪或者全息投影仪；
反射式几何全息屏101用于把照射到其上的光线进行逆反射，采用本发明制备的基于二维特征的反射式几何全息膜；
辅助成像屏102用于分光，优选半透半反材质制成的屏幕；
支持结构103分别与图像源100、反射式几何全息屏101和辅助成像屏102相匹配，为三者提供物理结构支撑；
控制器104与图像源100电连接，用于控制图像源100来调节投影画面的景深和显示内容；
为了增加显示系统的灵活性，我们还可以将支持结构103设置为可以运动或者变形的结构，将支持结构103和控制器104电连接，支持结构103根据并控制器104的控制信息，做出相应响应动作，实现图像源100、反射式几何全息屏101和辅助成像屏102的相对运动和/或整体运动，使得系统的可视视窗始终覆盖用户的眼睛，使得用户在不同的方位都可以正常观看画面，需要说明的是支持结构103为一般现有技术，本领域的技术人员 可以根据实际应用的空间条件自行设计，比如：使用一些铰链结构和类似于伞轴的结构可以非常容易的设计出可以变形的结构，这里不做具体限定；
作为优选方案，本发明所述的全息显示系统还包括与控制器104电连接的交互动作捕捉单元105，交互动作捕捉单元105用于识别用户的交互动作并将用户交互动作信息发送给控制器104，控制器104根据接收到的交互动作捕捉单元105获取的用户交互动作信息调整显示画面内容，实现用户与画面的交互动作，具体可以是采用摄像头结合机器视觉技术来识别用户的手势动作来获取用户的交互信息，从而控制画面显示内容或者控制支持结构103运动来调整图像源100、反射式几何全息屏101和/或辅助成像屏102的空间位置和姿态，控制器104还可以根据接收的交互动作捕捉单元105获取的用户交互动作信息来实时调整显示画面内容，实现用户与画面的交互动作，比如根据平移手势信号，控制画面进行平移，或者根据对应的其他交互动作控制画面的放大、拉近、推远、触碰等操作；
交互动作捕捉单元105的设置对于类似于穿戴式应用这种用户相对显示系统的空间位置固定不变的应用情景具有积极的意义；
另外，对于用户相对显示系统的空间位置实时变动的应用情景，还需要设置一个与控制器104电连接的人眼跟踪单元106，人眼跟踪单元106用于跟踪人眼的位置并将人眼的定位信息发送给控制器104，控制器104根据接收到的人眼跟踪单元106获取的人眼定位信息，来控制支持结构103做出相应的动作响应，来调整图像源100、反射式几何全息屏101和/或辅助成像屏102的相对位置和/或整体空间位置，使用户眼睛始终处于系统的可视空间内，这样用户即使在运动状态下眼睛也可以始终接收到投影信息，正常观看画面。
实际应用中，交互动作捕捉单元105和人眼跟踪单元106可以集成在同一个设备内完成，比如使用一个机器视觉摄像设备等。
图像源100投影出画面，光线照射在辅助成像屏102上，部分光线直接透过辅助成像屏102，这部分光线不会参与成像，另一部分光线经过辅助成像屏102的反射到反射式几何全息屏101上，而这部分光线再经过反射式几何全息屏101的光学转化，偏移微小距离d后原方向反射回去并透过辅助成像屏102，在空间内形成可以被观察到的离屏画面。
以上内容是结合具体的优选实施方式对本发明所作的进一步详细说明，不能认定本发明的具体实施只局限于这些说明。对于本发明所属技术领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干简单推演或替换，都应当视为属于本发明的保护范围。

Claims (13)

  1. 基于二维特征的反射式几何全息膜，其特征在于：包括基元膜(1)和若干阵列设置在基元膜(1)表面上的、横截面为直角三角形的柱状基元棱镜(2)；
    所述柱状基元棱镜(2)横截面的斜边所在的面均与基元膜(1)表面贴合，所述基元膜(1)内部、沿柱状基元棱镜(2)的长度方向设有若干相间排列的透明层(11)和反射层(12)；
    所述柱状基元棱镜(2)横截面的直角边所在的斜面(21)上设置有一层反射膜(3)，用于对光线进行镜面反射；
    所述柱状基元棱镜(2)横截面包含的直角以及透明层(11)和反射层(12)与柱状基元棱镜(2)的长度方向所成角度的误差范围在±5°以内。
  2. 根据权利要求1所述的基于二维特征的反射式几何全息膜，其特征在于：所述柱状基元棱镜(2)横截面的直角三角形的斜边长度为a，a≤2㎜。
  3. 根据权利要求1所述的基于二维特征的反射式几何全息膜，其特征在于：所述柱状基元棱镜(2)的横截面为等腰直角三角形。
  4. 根据权利要求1所述的基于二维特征的反射式几何全息膜，其特征在于：所述柱状基元棱镜(2)的端面和/或基元膜(1)与透明层(11)平行的端面也设置有一层反射膜(3)。
  5. 根据权利要求1所述的基于二维特征的反射式几何全息膜，其特征在于：所述基于二维特征的反射式几何全息膜为柔性膜。
  6. 根据权利要求5所述的基于二维特征的反射式几何全息膜，其特征在于：所述基于二维特征的反射式几何全息膜的水平夹持下垂长度为L㎝，可对折次数为n，满足：
    L≥5或者n*L>9。
  7. 根据权利要求6所述的基于二维特征的反射式几何全息膜，其特征在于：所述基于二维特征的反射式几何全息膜的水平夹持下垂长度为L㎝，可对折次数为n，满足：n*L≥28。
  8. 根据权利要求1所述的基于二维特征的反射式几何全息膜，其特征 在于：所述基元膜(1)的底面和反射膜(3)上分别设有保护膜，其中所述基元膜(1)的底面上设有的保护膜为透明保护膜。
  9. 根据权利要求1～8任意一项所述的基于二维特征的反射式几何全息膜的制备方法，其特征在于，包括以下步骤：
    1)准备一张透明层(11)与反射层(12)相间排列的基元膜(1)以及一张与基元膜(1)对应透明膜；
    2)将透明膜粘接于基元膜(1)的表面，沿垂直于透明层(11)与反射层(12)的方向上对透明膜进行切削，形成一层是基元膜(1)、另一层是阵列的横截面为直角三角形的柱状基元棱镜(2)排列形成的起伏锯齿状表面的膜，切削方向的误差范围在±5°以内；
    3)在柱状基元棱镜(2)的端面以及横截面的直角边所在的斜面(21)上镀一层反射膜(3)，即可获得基于二维特征的反射式几何全息膜。
  10. 根据权利要求9所述的基于二维特征的反射式几何全息膜的制备方法，其特征在于，步骤2)用以下方法替代：先将透明膜切削成若干个与基元膜(1)对应的柱状基元棱镜(2)，再将柱状基元棱镜(2)沿垂直于透明层(11)与反射层(12)的方向粘接在基元膜(1)的表面，粘接方向的误差范围在±5°以内。
  11. 根据权利要求9所述的基于二维特征的反射式几何全息膜的制备方法，其特征在于：在步骤2)之前或者之后还包括：在基元膜(1)的底面上粘接一层透明保护膜。
  12. 根据权利要求9所述的基于二维特征的反射式几何全息膜的制备方法，其特征在于：在步骤3)之后还包括：在设置有反射膜(3)的锯齿状起伏表面粘接一层保护膜。
  13. 根据权利要求9或10所述的基于二维特征的反射式几何全息膜的制备方法制备的基于二维特征的反射式几何全息膜于反射式几何全息显示系统的应用。
PCT/CN2021/087143 2020-04-17 2021-04-14 基于二维特征的反射式几何全息膜及其制备方法和应用 WO2021208941A1 (zh)

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