技术领域Technical Field
本发明涉及一种基于彩色偏振体光栅的全彩波导耦合近眼显示结构、制备方法及AR可穿戴设备。The present invention relates to a full-color waveguide-coupled near-eye display structure based on a color polarizer grating, a preparation method and an AR wearable device.
背景技术Background technique
基于具有耦合元件的平面波导而设计的近眼显示系统在过去的十几年有了很大的发展，被广泛应用到军事和商业领域。在AR设备上，上述的波导结构必须满足重量轻、体积小、高透明度以及出瞳广阔的特点。作为耦合波导近眼显示系统的基本组件之一，耦合元件能够决定视场角(FOV)、耦合效率、显色性等重要参数。Near-eye display systems designed based on planar waveguides with coupling elements have made great progress in the past decade and are widely used in military and commercial fields. On AR devices, the above waveguide structure must meet the characteristics of light weight, small size, high transparency and wide exit pupil. As one of the basic components of the coupled waveguide near-eye display system, the coupling element can determine important parameters such as field of view (FOV), coupling efficiency, and color rendering.
为了更进一步轻化波导结构，光学衍射元件(DOEs)已经被广泛研究并在波导近眼显示系统中被用作耦合元件。这种多衍射元件中，光学衍射光栅是最普遍的。当被应用在波导耦合式近眼显示系统中时，衍射光栅可以将来自微显示器的入射光束耦合到波导内。衍射光栅在具有大的衍射角的同时还具有角度选择性和波长选择性，这就保证了在满足全内反射条件时光束能够在波导中高效率地传播。In order to further lighten the waveguide structure, optical diffraction elements (DOEs) have been widely studied and used as coupling elements in waveguide near-eye display systems. Among such multi-diffraction elements, optical diffraction gratings are the most common. When used in a waveguide-coupled near-eye display system, the diffraction grating can couple the incident light beam from the microdisplay into the waveguide. The diffraction grating has angle selectivity and wavelength selectivity while having a large diffraction angle, which ensures that the light beam can propagate efficiently in the waveguide when the total internal reflection condition is met.
考虑到光衍射元件的多样性，全息体光栅(HVG)具有独特的优点，因此被广泛用作波导中的耦合装置。一般的全息体光栅可以通过在全息记录材料(如光致聚合物、重铬酸盐明胶等)记录干涉图样制成。当满足布拉格条件的光束照射到HVG上时，能够发生高衍射效率的单级衍射，并且衍射角度很大，这是HVG的重要特点。同时，由于其具有窄带宽和严格的角度选择性，HVG对环境光具有高透过性。但是，角度带宽和波长带宽很短会限制视场角FOV的大小并且当被用到波导耦合显示系统中时，也会限制全彩传输的实现。Considering the diversity of optical diffraction elements, holographic volume gratings (HVGs) have unique advantages and are therefore widely used as coupling devices in waveguides. General holographic volume gratings can be made by recording interference patterns on holographic recording materials (such as photopolymers, dichromated gelatin, etc.). When a light beam that meets the Bragg condition is irradiated onto the HVG, a single-order diffraction with high diffraction efficiency can occur, and the diffraction angle is large, which is an important feature of the HVG. At the same time, due to its narrow bandwidth and strict angular selectivity, the HVG has high transmittance to ambient light. However, the short angular bandwidth and wavelength bandwidth will limit the size of the field of view FOV and when used in a waveguide-coupled display system, it will also limit the realization of full-color transmission.
双折射率的差值能够决定体光栅的角度和波长带宽。传统的重铬酸盐明胶材料的双折射率材料能够达到0.15。但是其对环境的高度敏感性以及其复杂的制备过程导致如今大多数被用作记录介质的光致聚合物的双折射率差值仅有0.035。如此小的双折射率差值导致角度带宽和波长带宽均很窄，从而导致视场角很小。The difference in birefringence determines the angular and wavelength bandwidth of the volume grating. The birefringence of conventional dichromated gelatin materials can reach 0.15. However, due to its high sensitivity to the environment and its complex preparation process, most photopolymers used as recording media today have a birefringence difference of only 0.035. Such a small birefringence difference results in a narrow angular bandwidth and a narrow wavelength bandwidth, resulting in a small field of view.
发明内容Summary of the invention
针对现有技术的不足，本发明提出一种基于彩色偏振体光栅(CPVG)的全彩波导耦合近眼显示系统的制备方法，用于解决现有的方法中存在的衍射效率低、视场角小、不利于实现全彩传输等问题。并且光栅的偏折特性使得至少50％的非偏振环境光直接透过光栅而不发生衍射。In view of the shortcomings of the prior art, the present invention proposes a method for preparing a full-color waveguide-coupled near-eye display system based on a color polarizer grating (CPVG), which is used to solve the problems of low diffraction efficiency, small field of view, and difficulty in achieving full-color transmission in the prior art. In addition, the deflection characteristics of the grating allow at least 50% of the non-polarized ambient light to pass directly through the grating without diffraction.
技术方案：为解决上述问题，本发明采用以下技术方案：Technical solution: To solve the above problems, the present invention adopts the following technical solution:
一种基于彩色偏振体光栅的全彩波导耦合近眼显示结构，采用以彩色偏振体光栅作为耦合装置的双层波导结构来实现全彩近眼显示，其中一层被用来传播蓝、绿色光束的蓝、绿色波导结构中使用了蓝、绿色的偏振体光栅作为耦合装置从而实现在波导中传输蓝色和绿色光束；另一层被用来传播红色光束的红色波导结构中使用了红色偏振体光栅作为耦合装置从而实现在波导中传输红色光束。A full-color waveguide coupled near-eye display structure based on a color polarizer grating adopts a double-layer waveguide structure with a color polarizer grating as a coupling device to achieve full-color near-eye display, wherein one layer is used for transmitting blue and green light beams, and a blue and green polarizer grating is used as a coupling device in a blue and green waveguide structure, thereby transmitting the blue and green light beams in the waveguide; and the other layer is used for transmitting a red light beam, and a red polarizer grating is used as a coupling device in a red waveguide structure, thereby transmitting the red light beam in the waveguide.
蓝、绿色波导结构中的入耦合装置和出耦合装置均为蓝、绿色PVG，并且蓝、绿色波导结构中的入耦合装置和出耦合装置位于平面波导结构的镜面对称位置；相应地，红色波导结构中的入耦合装置和出耦合装置均为红色PVG，并且红色波导结构中第二入耦合装置和出耦合装置也位于平面波导结构的镜面对称位置。The in-coupling device and out-coupling device in the blue and green waveguide structures are both blue and green PVG, and the in-coupling device and out-coupling device in the blue and green waveguide structures are located at mirror-symmetrical positions of the planar waveguide structure; correspondingly, the in-coupling device and out-coupling device in the red waveguide structure are both red PVG, and the second in-coupling device and out-coupling device in the red waveguide structure are also located at mirror-symmetrical positions of the planar waveguide structure.
所述蓝、绿色波导结构包括蓝色波导层和绿色波导层两层。The blue and green waveguide structure comprises two layers: a blue waveguide layer and a green waveguide layer.
每两个波导层叠加在一起后在两个波导层之间存在着空气层。When every two waveguide layers are stacked together, there is an air layer between the two waveguide layers.
蓝色波导层的水平周期长度值和绿色波导层水平周期长度值相同，其满足布拉格衍射公式：The horizontal period length of the blue waveguide layer is the same as that of the green waveguide layer, which satisfies the Bragg diffraction formula:
式(3)中，neff代表光栅所用的双折射材料的等效折射率；Λx代表光栅在x方向上的的水平周期长度；代表波导层中具有周期性的折射率平面的倾斜角；λB代表真空中的布拉格波长。In formula (3), neff represents the equivalent refractive index of the birefringent material used for the grating; Λx represents the horizontal period length of the grating in the x direction; represents the tilt angle of the periodic refractive index plane in the waveguide layer; λB represents the Bragg wavelength in vacuum.
本发明还进一步公开了一种所述的基于彩色偏振体光栅的全彩波导耦合近眼显示结构的制备方法，包括以下几个步骤：The present invention further discloses a method for preparing the full-color waveguide-coupled near-eye display structure based on a color polarizer grating, comprising the following steps:
步骤一、将光取向材料溶于相应的溶剂后在干净的玻璃波导表面进行旋涂，加热一段时间后形成薄膜；Step 1: dissolving the photo-alignment material in a corresponding solvent and then spin coating it on a clean glass waveguide surface, and heating it for a period of time to form a thin film;
步骤二、两束偏振光在步骤一中形成的光取向材料薄膜上进行干涉曝光，并进一步形成光取向层；Step 2: performing interference exposure on the photo-alignment material film formed in step 1 with two polarized lights, and further forming a photo-alignment layer;
步骤三、将含有液晶聚合物和手性材料的溶液地在步骤二中形成的取向层上，再将玻璃放在旋涂机上以一定的旋转速度旋转一定时间后停止；Step 3, placing a solution containing a liquid crystal polymer and a chiral material on the alignment layer formed in step 2, and then placing the glass on a spin coater and rotating it at a certain speed for a certain period of time and then stopping;
步骤四、使用5J/cm2的紫外光在氮环境中进行紫外固化；Step 4: UV curing in a nitrogen environment using 5 J/cm2 of UV light;
步骤五、重复步骤三和步骤四直到薄膜厚度达到100nm到1μm以保证形成光栅，此外，对于蓝、绿色波导结构首先旋涂和固化绿色的PVG厚度达到100nm～1μm，之后在绿色PVG层上直接旋涂和固定蓝色的波导层。Step 5: Repeat steps 3 and 4 until the film thickness reaches 100nm to 1μm to ensure the formation of the grating. In addition, for the blue and green waveguide structures, first spin-coat and cure the green PVG to a thickness of 100nm to 1μm, and then spin-coat and fix the blue waveguide layer directly on the green PVG layer.
步骤二中的曝光环境需要满足温度为20℃～30℃之间、相对湿度保持在38以下。The exposure environment in step 2 needs to meet the temperature between 20°C and 30°C and the relative humidity is kept below 38.
步骤二中曝光所使用的激光器能量控制在6J/cm2～10J/cm2。The laser energy used for exposure in step 2 is controlled to be 6 J/cm2 -10 J/cm2 .
本发明还进一步的公开了一种AR可穿戴设备，采用所述基于彩色偏振体光栅的全彩波导耦合近眼显示结构。The present invention further discloses an AR wearable device, which adopts the full-color waveguide-coupled near-eye display structure based on the color polarizer grating.
有益效果：Beneficial effects:
第一、本发明中起到耦合作用的彩色体全息光栅能够将蓝绿波段和红色波段的光分别耦合到两个波导中来实现基于全彩耦合波导的显示系统。First, the color volume holographic grating that plays a coupling role in the present invention can couple the light in the blue-green band and the red band into two waveguides respectively to realize a display system based on a full-color coupled waveguide.
第二、本发明形成了布拉格光栅的结构并且所使用的液晶材料具有大的双折射率差值△n，因此根据耦合波理论可知本发明能够实现很高的光栅衍射效率。Second, the present invention forms a Bragg grating structure and the liquid crystal material used has a large birefringence difference Δn. Therefore, according to coupled wave theory, it can be known that the present invention can achieve a very high grating diffraction efficiency.
第三、本发明采用的液晶材料具有较大的双折射率差值，根据耦合波理论可知耦合光栅入射角带宽变大，利用这一点可以制备具有大视场角(可以达到35°)的AR可穿戴设备。Third, the liquid crystal material used in the present invention has a large birefringence difference. According to the coupled wave theory, the incident angle bandwidth of the coupled grating becomes larger. This can be used to prepare AR wearable devices with a large field of view (up to 35°).
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1为本发明中作为耦合装置的CPVG结构示意图；FIG1 is a schematic diagram of the structure of a CPVG used as a coupling device in the present invention;
其中，图1(a)展示了被用来衍射蓝色和绿色的蓝绿色体光栅结构，其中，Λbgx代表蓝色波导层和绿色波导层这两层的水平周期长度值；Λby和Λgy分别代表蓝色波导层和绿色波导层的垂直周期长度值；向量Kb和Kg分别代表蓝色波导层和绿色波导层中体光栅的布拉格矢量；和/>分别代表蓝色波导层和绿色波导层中具有周期性的折射率平面的倾斜角。FIG1(a) shows a blue-green volume grating structure used to diffract blue and green colors, wherein Λbgx represents the horizontal period length of the blue waveguide layer and the green waveguide layer; Λby and Λgy represent the vertical period length of the blue waveguide layer and the green waveguide layer, respectively; vectors Kb and Kg represent the Bragg vectors of the volume grating in the blue waveguide layer and the green waveguide layer, respectively; and/> represent the tilt angles of the periodic refractive index planes in the blue waveguide layer and the green waveguide layer, respectively.
图1(b)展示了能够使红光发生布拉格衍射的PVG结构，其中，Λrx代表红色波导层的水平周期长度值；Λry代表垂直周期长度值；向量Kr代表红色波导层中体光栅的布拉格矢量；代表红色波导层中具有周期性折射率平面的倾斜角；α代表液晶分子光轴与z轴之间的夹角。FIG1( b ) shows a PVG structure that enables Bragg diffraction of red light, where Λrx represents the horizontal period length of the red waveguide layer; Λry represents the vertical period length; and vector Kr represents the Bragg vector of the volume grating in the red waveguide layer. represents the tilt angle of the periodic refractive index plane in the red waveguide layer; α represents the angle between the optical axis of the liquid crystal molecule and the z-axis.
图2为本发明所阐述的双层波导结构的示意图；FIG2 is a schematic diagram of a double-layer waveguide structure according to the present invention;
其中，1、微显示器；2、观察者的视网膜；3、人眼晶状体；4、准直器；5、蓝绿色波导层和红色波导层之间的空气层；6、蓝绿色波导层；7、红色波导层；8、绿色波导层的入耦合装置；9、蓝绿色波导层的出耦合装置；10、红色波导层的入耦合装置；11、红色波导层的出耦合装置；Among them, 1. micro display; 2. retina of the observer; 3. human eye lens; 4.collimator ; 5. air layer between the cyan waveguide layer and the red waveguide layer; 6. cyan waveguide layer; 7. red waveguide layer; 8. in-coupling device of the green waveguide layer; 9. out-coupling device of the cyan waveguide layer; 10. in-coupling device of the red waveguide layer; 11. out-coupling device of the red waveguide layer;
图3为本发明所阐述的三层波导结构的示意图；FIG3 is a schematic diagram of a three-layer waveguide structure described in the present invention;
其中，20、蓝色波导层的入耦合装置；30、绿色波导层的入耦合装置；40、蓝色波导层的出耦合装置；50、绿色波导层的出耦合装置；60、蓝色波导层；70、绿色波导层；Among them, 20, the in-coupling device of the blue waveguide layer; 30, the in-coupling device of the green waveguide layer; 40, the out-coupling device of the blue waveguide layer; 50, the out-coupling device of the green waveguide layer; 60, the blue waveguide layer; 70, the green waveguide layer;
图4为本发明的衍射角随入射角变化而变化的曲线图；FIG4 is a graph showing the diffraction angle of the present invention as a function of the incident angle;
图5为本发明的流程图；FIG5 is a flow chart of the present invention;
图6为本发明所用到的曝光光路示意图；FIG6 is a schematic diagram of an exposure light path used in the present invention;
其中，100、线偏振激光器；200、半波片；300、偏振光分束器PBS；(400，900)、四分之一波片；(500，800)、扩束透镜；(600，700)、平面镜；1000、待曝光的样片；α代表两束偏振光之间的夹角。Among them, 100, linear polarization laser; 200, half-wave plate; 300, polarization beam splitter PBS; (400, 900), quarter-wave plate; (500, 800), beam expander lens; (600, 700), plane mirror; 1000, sample to be exposed; α represents the angle between two polarized light beams.
具体实施方式Detailed ways
下面结合附图对本发明作更进一步的说明。The present invention will be further described below in conjunction with the accompanying drawings.
本发明中所用到的作为耦合装置的CPVG的结构如图1所示。由图1可知体全息光栅PVG具有二维周期结构，其中，The structure of the CPVG used as a coupling device in the present invention is shown in FIG1. As can be seen from FIG1, the volume holographic grating PVG has a two-dimensional periodic structure, wherein:
在x-z平面(水平面)，液晶分子光轴与z轴之间的夹角α会沿x方向，既水平方向发生周期性变化，其周期长度记作Λx。In the xz plane (horizontal plane), the angle α between the optical axis of the liquid crystal molecule and the z axis will change periodically along the x direction, that is, the horizontal direction, and its period length is recorded as Λx .
在y-z平面上，液晶材料(或者更广泛地，双折射材料)在y方向，既垂直方向上呈现出周期螺旋结构，其周期记作Λy。On the yz plane, the liquid crystal material (or more generally, the birefringent material) exhibits a periodic spiral structure in the y direction, ie, the vertical direction, with the period being denoted as Λy .
这样的二维周期结构能够产生一系列倾斜的具有周期性的折射率平面，其倾斜角可由式(1)计算：Such a two-dimensional periodic structure can produce a series of tilted periodic refractive index planes with a tilt angle of It can be calculated by formula (1):
为了简化分析而不失一般性，假设反射式PVG的倾斜角满足并且α可由式(2)计算：In order to simplify the analysis without loss of generality, it is assumed that the tilt angle of the reflective PVG satisfies And α can be calculated by formula (2):
如果双折射率材料层足够厚，则布拉格衍射能够被建立。事实上，垂直入射光的衍射光具有高衍射效率，布拉格衍射由式(3)所表示：If the birefringent material layer is thick enough, Bragg diffraction can be established. In fact, the diffraction efficiency of the vertically incident light is high, and the Bragg diffraction is expressed by equation (3):
式(3)中λB代表真空中的布拉格波长，neff代表双折射介质的等效折射率，由式(4)计算：In formula (3), λB represents the Bragg wavelength in vacuum, neff represents the equivalent refractive index of the birefringent medium, and is calculated by formula (4):
图1中所展示的两种CPVG结构分别代表(a)被用来衍射蓝色和绿色的蓝、绿色体光栅(cyan PVG)。Cyan PVG可以被分为蓝色和绿色两层，这两层的水平周期长度相同，在图1(a)中被记作Λbgx，其值由上述式(3)计算：The two CPVG structures shown in Figure 1 represent (a) blue and green volume gratings (cyan PVG) used to diffract blue and green respectively. Cyan PVG can be divided into two layers, blue and green, with the same horizontal period length, which is denoted as Λbgx in Figure 1(a), and its value is calculated by the above formula (3):
式(3)中，neff代表光栅所用的双折射材料的等效折射率；Λx代表光栅在x方向上的的水平周期长度；代表波导层中具有周期性的折射率平面的倾斜角；λB代表真空中的布拉格波长。In formula (3), neff represents the equivalent refractive index of the birefringent material used for the grating; Λx represents the horizontal period length of the grating in the x direction; represents the tilt angle of the periodic refractive index plane in the waveguide layer; λB represents the Bragg wavelength in vacuum.
当波长值λB为457nm(蓝色)，为蓝色波导层中的折射率平面倾斜角时，Λx为蓝色波导层水平周期长度值；当波长值λB为532nm(绿色)，/>为绿色波导层中的折射率平面倾斜角时，Λx为绿色波导层水平周期长度值。由于在本发明所提的结构中蓝绿色波导层的水平周期长度数值相同，因此记为将其记Λbgx。When the wavelength value λB is 457nm (blue), is the inclination angle of the refractive index plane in the blue waveguide layer, Λx is the horizontal period length of the blue waveguide layer; when the wavelength value λB is 532nm (green), /> When is the inclination angle of the refractive index plane in the green waveguide layer, Λx is the horizontal period length of the green waveguide layer. Since the horizontal period lengths of the blue and green waveguide layers in the structure of the present invention are the same, they are recorded as Λbgx .
由于蓝绿两层具有相同的水平周期长度值，所以蓝、绿两层波导层满足相同的光栅色散方程(5)：Since the blue and green layers have the same horizontal period length, the blue and green waveguide layers satisfy the same grating dispersion equation (5):
式(5)中，θ0代表衍射角(光束在波导中的传播角)，nglass代表玻璃波导的折射率值，λ代表光束的波长，θi代表在空气中的入射角，m代表衍射级次(对于体光栅而言m＝1)，Λx代表光栅在x方向上的的水平周期长度。对于蓝、绿色波导层而言，Λx即为Λbgx。In formula (5), θ0 represents the diffraction angle (the propagation angle of the light beam in the waveguide), nglass represents the refractive index of the glass waveguide, λ represents the wavelength of the light beam, θi represents the incident angle in air, m represents the diffraction order (for volume gratings, m=1), and Λx represents the horizontal period length of the grating in the x direction. For the blue and green waveguide layers, Λx is Λbgx .
蓝、绿两层的不同之处在于y方向上的周期长度不同，即图1(a)中的Λby和Λgy不同，由式(1)和(3)可知，这决定了垂直入射时的布拉格中心波长的不同。The difference between the blue and green layers is that the period lengths in the y direction are different, that is, Λby and Λgy in Figure 1(a) are different. From equations (1) and (3), it can be seen that this determines the difference in the Bragg center wavelength at vertical incidence.
在制备过程中CPVG仅需要一次偏振干涉曝光即可在光取向材料上产生所需要的水平周期长度Λx，之后依次旋涂具有不同Λy的手性螺旋材料即可。During the preparation process, CPVG only needs one polarization interference exposure to produce the required horizontal period length Λx on the photo-aligned material, and then spin-coat chiral helical materials with different Λy in sequence.
图1(b)展示了能够使红光发生布拉格衍射的PVG结构，它具有和蓝、绿色CPVG不同的水平周期长度，即Λrx不等于Λbgx。Figure 1(b) shows a PVG structure that can cause Bragg diffraction of red light. It has a horizontal period length different from that of the blue and green CPVGs, that is, Λrx is not equal to Λbgx .
表1列出了一组示例参数。作为具体实施中的举例，表1列出了一组对应不同中心波长(457nm,532nm,630nm)的CPVG的相关参数。实际情况下的具体参数值需要按照所需设计改变。Table 1 lists a set of example parameters. As an example in a specific implementation, Table 1 lists a set of relevant parameters of CPVG corresponding to different central wavelengths (457nm, 532nm, 630nm). The specific parameter values in actual situations need to be changed according to the required design.
图2展示了本发明的整体结构，系统包含一个传播蓝、绿色的蓝绿色波导层6(Waveguide(B+G))和一个传播红色的红色波导层7(Waveguide(R))。FIG2 shows the overall structure of the present invention. The system includes a blue-green waveguide layer 6 (Waveguide (B+G)) for transmitting blue and green colors and a red waveguide layer 7 (Waveguide (R)) for transmitting red colors.
蓝绿色波导层6中的绿色波导层的入耦合装置8和蓝绿色波导层的出耦合装置9均为蓝绿色PVG，并且绿色波导层的入耦合装置8和蓝绿色波导层的出耦合装置9位于平面波导结构的镜面对称位置。相应地，红色波导层7中的红色波导层的入耦合装置10和红色波导层的出耦合装置11均为红色PVG，并且红色波导层的入耦合装置10和红色波导层的出耦合装置11也位于平面波导结构的镜面对称位置。The in-coupling device 8 of the green waveguide layer and the out-coupling device 9 of the blue-green waveguide layer in the blue-green waveguide layer 6 are both blue-green PVG, and the in-coupling device 8 of the green waveguide layer and the out-coupling device 9 of the blue-green waveguide layer are located at mirror-symmetrical positions of the planar waveguide structure. Correspondingly, the in-coupling device 10 of the red waveguide layer and the out-coupling device 11 of the red waveguide layer in the red waveguide layer 7 are both red PVG, and the in-coupling device 10 of the red waveguide layer and the out-coupling device 11 of the red waveguide layer are also located at mirror-symmetrical positions of the planar waveguide structure.
更清楚地，图2展示了来自微显示器1的中心波长段的光束在双层波导结构中的传播。经过准直器4准直后，由微显示器1发出的包含红绿蓝三种波段的白光将通过蓝绿色波导层的绿色波导层的入耦合装置8和红色波导层的入耦合装置10垂直射入波导中。More clearly, Fig. 2 shows the propagation of the light beam of the central wavelength band from the micro display 1 in the double-layer waveguide structure. After being collimated by the collimator 4, the white light emitted by the micro display 1 containing three wavelength bands of red, green and blue will be vertically injected into the waveguide through the in-coupling device 8 of the green waveguide layer of the blue-green waveguide layer and the in-coupling device 10 of the red waveguide layer.
然后，入耦合装置将会以大于全内反射角的不同角度将入射光衍射到波导中。这两个能够传播不同波段光束的波导具有不同的PVG。Then, the in-coupling device will diffract the incident light into the waveguide at different angles greater than the total internal reflection angle. The two waveguides capable of transmitting light beams of different wavelength bands have different PVGs.
位于顶端的蓝、绿色波导的CPVG对蓝色和绿色起作用，其衍射角可以利用式(5)得到。The CPVG of the blue and green waveguides located at the top contributes to blue and green, and their diffraction angles can be obtained using equation (5).
位于底端的红色波导的PVG仅对红色起作用，同样地，其衍射角也可以利用式(5)得到。The PVG of the red waveguide at the bottom only acts on red. Similarly, its diffraction angle can be obtained using equation (5).
当传播的光束到达作为出耦合的PVG时，出耦合PVG会以与入射波到达入耦合时的角度将光束衍射出波导。When the propagating light beam reaches the PVG acting as an outcoupler, the outcoupling PVG will diffract the light beam out of the waveguide at the same angle as the incident wave when it reached the incoupler.
经过人眼晶状体3的准直，观察者的视网膜2在合适的位置可以接受到一个彩色的像素图像。事实上，像素在无穷远处成像并被人眼所接收。After the collimation of the human eye lens 3, the observer's retina 2 can receive a colored pixel image at the appropriate position. In fact, the pixel is imaged at infinity and received by the human eye.
另外，由于入耦合和出耦合PVG在水平方向上的对称性，色散现象可以被抵消。也就是说，彩色鬼影图像可以在内部被消除，这对保证图像质量的全彩显示而言是一个重要的特点。而且，在不同波导内传播的光束的传播是不相关的，并且由于两个波导层之间存在着空气层5，因此在不同波导的光栅之间的串扰是可以忽略不计的。在另一方面，出瞳的连续性对于基于波导的显示系统而言也是一个关键问题，它会影响在不同位置观察图像时的颜色和亮度的统一性。我们已经在以前的工作中研究并记录了相关的事实。通过选择合适厚度的波导、传播步长和调整入瞳大小的方法，该问题可以被高效解决。In addition, due to the symmetry of the in-coupled and out-coupled PVGs in the horizontal direction, the dispersion phenomenon can be cancelled. In other words, the color ghost images can be eliminated internally, which is an important feature for full-color display with guaranteed image quality. Moreover, the propagation of the beams propagating in different waveguides is uncorrelated, and due to the presence of an air layer 5 between the two waveguide layers, the crosstalk between the gratings in different waveguides is negligible. On the other hand, the continuity of the exit pupil is also a key issue for waveguide-based display systems, which affects the uniformity of color and brightness when observing the image at different positions. We have studied and documented the relevant facts in previous work. This problem can be effectively solved by choosing the appropriate waveguide thickness, propagation step size and method to adjust the entrance pupil size.
采用厚度为1mm的高折射率玻璃作为波导，并且三种颜色(红、绿、蓝)的传播光束的中心波长分别为630nm、532nm、457nm。A high refractive index glass with a thickness of 1 mm is used as the waveguide, and the central wavelengths of the propagating light beams of three colors (red, green, and blue) are 630 nm, 532 nm, and 457 nm, respectively.
为了使光束能够沿着波导传播，最小的衍射角由公式(6)计算得到：In order to allow the light beam to propagate along the waveguide, the minimum diffraction angle is calculated by formula (6):
θmin＝arcsin(1/n), (6)θmin = arcsin(1/n), (6)
式(6)中n代表所用波导材料的折射率值。In formula (6), n represents the refractive index value of the waveguide material used.
最大衍射角度由公式(7)计算得到：The maximum diffraction angle is calculated by formula (7):
θmax＝arctan(W/2t), (7)θmax = arctan(W/2t), (7)
式(7)中W代表准直器空径(本发明中为10mm)，t代表波导的厚度(本发明中每层的波导厚度为1mm)。In formula (7), W represents the collimator diameter (10 mm in the present invention), and t represents the thickness of the waveguide (the thickness of each waveguide layer in the present invention is 1 mm).
图4展示了在不同波长条件下具有不同入射角的衍射角度分布曲线。FIG4 shows the diffraction angle distribution curves at different incident angles under different wavelength conditions.
由图4可知所能够实现的FOV大约为35.7°(-13.3°～22.4°)，这种大小的视场角满足了当前主流的基于波导的近眼显示系统的需求。As shown in FIG. 4 , the achievable FOV is approximately 35.7° (-13.3° to 22.4°). This field of view meets the requirements of the current mainstream waveguide-based near-eye display system.
图5为具体制备流程图：Figure 5 is a specific preparation flow chart:
步骤一、将光取向材料溶于相应的溶剂后在干净的玻璃波导(n＝1.85)表面进行旋涂。Step 1: Dissolve the photo-alignment material in a corresponding solvent and then spin-coat it on the surface of a clean glass waveguide (n=1.85).
作为示例可选择偶氮染料类如SD1、BY等作为光取向材料，DMF作为溶剂。旋涂机以一定转速旋转一段时间后停止，之后将波导在120℃的热台上加热30分钟形成薄膜。As an example, azo dyes such as SD1, BY, etc. can be selected as photo-alignment materials, and DMF can be used as solvent. The spin coater rotates at a certain speed for a period of time and then stops, and then the waveguide is heated on a hot stage at 120° C. for 30 minutes to form a thin film.
步骤二、两束偏振光在步骤一中形成的光取向材料薄膜上进行干涉曝光，并进一步形成光取向层，曝光装置如图6所示：Step 2: Two polarized light beams are subjected to interference exposure on the photo-alignment material film formed in step 1, and a photo-alignment layer is further formed. The exposure device is shown in FIG6 :
由线偏振激光器100发出的光束在经过半波片200后被偏振光分束器(PBS)300分成两束相互正交的偏振光束。两个四分之一波片(QWP)再将两束偏振光分别转变为右旋圆偏光和左旋圆偏光。The light beam emitted by the linear polarization laser 100 is split into two mutually orthogonal polarized light beams by the polarization beam splitter (PBS) 300 after passing through the half-wave plate 200. Two quarter-wave plates (QWP) then convert the two polarized light beams into right-handed circular polarization light and left-handed circular polarization light respectively.
半波片200被用来调整两路光的光强以保证两路光强相同。The half-wave plate 200 is used to adjust the light intensity of the two paths of light to ensure that the light intensity of the two paths is the same.
两路相干光在经过空间滤波和扩束透镜之后，分别被平面镜一定角度反射，最后这两束圆偏特性相反的圆偏光将会以α的夹角叠加并在样品1000的光取向层上形成干涉图样。After passing through spatial filtering and a beam expander lens, the two coherent lights are reflected at a certain angle by a plane mirror respectively. Finally, the two circularly polarized lights with opposite circular polarization characteristics will be superimposed at an angle of α and form an interference pattern on the optical orientation layer of sample 1000.
作为本发明的示例，对于蓝、绿色和红色的PVG，如果曝光角度分别被设置为76°和60°，这将会使其水平方向的的周期长度分别为371.5nm和457nm。As an example of the present invention, for blue, green and red PVG, if the exposure angles are set to 76° and 60° respectively, this will result in the horizontal period lengths being 371.5 nm and 457 nm respectively.
曝光环境必须满足一定温度和湿度的条件。此外曝光过程中所使用的激光器能量也必须满足一定条件。作为示例，本发明所使用的激光器能量在8J/cm2左右。The exposure environment must meet certain temperature and humidity conditions. In addition, the laser energy used in the exposure process must also meet certain conditions. As an example, the laser energy used in the present invention is about 8J/cm2 .
步骤三、本发明中采用液晶聚合物和手性材料来产生图1中y方向上的螺旋结构，并使用光引发剂和相应溶剂。作为示例可采用Irgacure651作为光引发剂，采用甲苯作为溶剂。Step 3: In the present invention, liquid crystal polymer and chiral material are used to generate the helical structure in the y direction in Figure 1, and a photoinitiator and a corresponding solvent are used. As an example, Irgacure 651 can be used as the photoinitiator, and toluene can be used as the solvent.
作为示例，本发明所用到的步骤三中所提的含有液晶聚合物和手性材料的溶液的质液比例大约在15％～20％的范围内。As an example, the mass-to-liquid ratio of the solution containing the liquid crystal polymer and the chiral material mentioned in step 3 of the present invention is approximately in the range of 15% to 20%.
旋涂机以一定的旋转速度旋转一定时间后停止，垂直周期长度Λy能够达到所需要的值。The spin coater rotates at a certain speed for a certain period of time and then stops, and the vertical period length Λy can reach the required value.
作为示例，可以选择如表1中所给出的红(中心波长为457nm)、绿(中心波长为532nm)、蓝(中心波长为630nm)三色波导层的水平周期长度值Λx和垂直周期长度值Λy进行制备。As an example, the horizontal period length valuesΔx and vertical period length values Δy of the three-color waveguide layers of red (central wavelength of 457 nm), green (central wavelength of 532 nm), and blue (central wavelength of 630 nm) as given in Table 1 can be selected for preparation.
表1Table 1
事实上，由于光取向层的锚定能和手性材料的螺旋扭曲能产生的二维周期结构，双折射材料分子能够形成螺旋结构。In fact, due to the two-dimensional periodic structure generated by the anchoring energy of the photo-alignment layer and the helical twisting energy of the chiral material, the birefringent material molecules can form a helical structure.
步骤四、使用紫外光在氮环境中进行紫外固化，紫外光的具体功率值需要根据所使用的材料种类等因素确定。作为示例，本发明中所使用的紫外光能量满足1J/cm2～10J/cm2的Step 4: Use ultraviolet light to perform ultraviolet curing in a nitrogen environment. The specific power value of the ultraviolet light needs to be determined according to factors such as the type of material used. As an example, the ultraviolet light energy used in the present invention meets the range of 1J/cm2 to 10J/cm2.
步骤五、重复步骤三四直到薄膜厚度大于一定值(作为示例，本发明中该值约为4.5μm)。此外对于蓝、绿色的PVG首先旋涂和固化绿色的PVG到所需要的厚度，之后在绿色PVG层上直接旋涂和固定蓝色的溶液。Step 5: Repeat steps 3 and 4 until the film thickness is greater than a certain value (for example, in the present invention, the value is about 4.5 μm). In addition, for blue and green PVG, first spin-coat and cure the green PVG to the required thickness, and then spin-coat and fix the blue solution directly on the green PVG layer.
经过以上五个步骤能够制得一个波导，之后重复以上五步再制备出另一种颜色的波导，讲两个波导就叠加在一起就制得了基于彩色偏振体光栅的全彩耦合波导。After the above five steps, a waveguide can be produced. Then the above five steps are repeated to prepare a waveguide of another color. The two waveguides are superimposed together to produce a full-color coupled waveguide based on a color polarizer grating.
作为示例，本发明这里所使用的玻璃基底的底面为25mm×75mm的长方形，厚度为0.05mm,双折射率值为0.18。在旋涂和光栅制备之后，利用透明紫外光固化剂将另一个相同的干净的玻璃粘合在所形成的光栅表面，最终制得的一层波导厚度为1mm。As an example, the bottom surface of the glass substrate used in the present invention is a rectangular shape of 25 mm×75 mm, with a thickness of 0.05 mm and a birefringence value of 0.18. After spin coating and grating preparation, another identical clean glass is bonded to the formed grating surface using a transparent UV curing agent, and the final waveguide thickness is 1 mm.
基于同样的工作原理，作为本发明还包含三层波导结构。Based on the same working principle, the present invention also includes a three-layer waveguide structure.
如图3所示，即将单层的蓝、绿色波导分为蓝色波导层60、绿色波导层70两层。每层波导的制作同样按照图5中所述的步骤进行。之后将中心波长为457nm的蓝色波导层60和中心波长为532nm的绿色红色波导层70以及中心波长为630nm的红色波导层7叠加在一起即组成了图3中所描述的三层波导结构。As shown in FIG3 , the single-layer blue and green waveguide is divided into two layers: a blue waveguide layer 60 and a green waveguide layer 70. The production of each waveguide layer is also carried out according to the steps described in FIG5 . Then, the blue waveguide layer 60 with a central wavelength of 457 nm, the green and red waveguide layer 70 with a central wavelength of 532 nm, and the red waveguide layer 7 with a central wavelength of 630 nm are stacked together to form the three-layer waveguide structure described in FIG3 .
和双层波导结构类似地，来自微显示器1的包含红绿蓝三种波段的白光光束在经过准直器4准直后，依次通过蓝色波导层的入耦合装置20、绿色波导层的入耦合装置30以及红色波导层的入耦合装置10后垂直射入波导中。然后，入耦合PVG将会以大于全内反射角的不同角度将入射光衍射到波导中。由于入耦合装置和出耦合装置关于于波导具有镜面对称性，因此当在不同波导层中传播的光束到达作为出耦合的PVG时，出耦合PVG会以与入射波到达入耦合时的角度将光束衍射出波导。Similar to the double-layer waveguide structure, the white light beam containing three wavelength bands of red, green and blue from the micro display 1 is collimated by the collimator 4, and then passes through the in-coupling device 20 of the blue waveguide layer, the in-coupling device 30 of the green waveguide layer, and the in-coupling device 10 of the red waveguide layer in sequence, and then vertically enters the waveguide. Then, the in-coupling PVG will diffract the incident light into the waveguide at different angles greater than the total internal reflection angle. Since the in-coupling device and the out-coupling device have mirror symmetry with respect to the waveguide, when the light beams propagating in different waveguide layers reach the PVG as the out-coupling, the out-coupling PVG will diffract the light beam out of the waveguide at the same angle as the incident wave when it reaches the in-coupling.
图3中40代表蓝色波导层的出耦合装置，50代表绿色波导层中的出耦合装置，11代表红色波导层中的出耦合装置，5代表不同波导层之间的空气层。In FIG. 3 , 40 represents the outcoupling device of the blue waveguide layer, 50 represents the outcoupling device of the green waveguide layer, 11 represents the outcoupling device of the red waveguide layer, and 5 represents the air layer between different waveguide layers.
光束从波导射出后经过人眼晶状体3的准直，观察者的视网膜2在合适的位置可以接受到一个彩色的像素图像。After being emitted from the waveguide, the light beam is collimated by the lens 3 of the human eye, and the observer's retina 2 can receive a colorful pixel image at the appropriate position.
事实上，像素在无穷远处成像并被人眼所接收。In fact, the pixels are imaged at infinity and received by the human eye.
以上所述仅是本发明的优选实施方式，应当指出：对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
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| PCT/CN2019/101983WO2020088055A1 (en) | 2018-10-31 | 2019-08-22 | Color polarizer grating-based full-color waveguide coupling near-eye display structure and preparation method therefor, and ar wearable device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109917547B (en)* | 2018-10-31 | 2024-06-18 | 东南大学 | Full-color waveguide coupling near-to-eye display structure based on color polarizer grating, preparation method and AR wearable device |
| JP7398470B2 (en)* | 2019-09-27 | 2023-12-14 | 富士フイルム株式会社 | Method for manufacturing optical elements |
| US11598919B2 (en)* | 2019-10-14 | 2023-03-07 | Meta Platforms Technologies, Llc | Artificial reality system having Bragg grating |
| CN110824613A (en)* | 2019-11-13 | 2020-02-21 | 东南大学 | Polarization multiplexing waveguide display device |
| CN110727116A (en)* | 2019-11-13 | 2020-01-24 | 东南大学 | A two-dimensional pupil dilation method based on polarized volume holographic grating |
| CN111352182B (en)* | 2020-04-29 | 2021-07-30 | 刘奡 | Exposure method of polarizer holographic grating |
| CN113341569B (en)* | 2021-06-09 | 2022-04-19 | 东南大学 | A polarization multiplexing diffractive waveguide large field angle imaging system and method |
| CN114236971B (en)* | 2021-11-30 | 2023-11-21 | 歌尔股份有限公司 | Exposure system and exposure method for polarization holographic grating |
| CN114236819B (en) | 2021-12-29 | 2022-09-27 | 东南大学 | Waveguide display two-dimensional pupil expanding method based on polarizer holographic grating |
| CN114578561B (en)* | 2022-01-27 | 2024-03-26 | 东南大学 | Large-view-field high-brightness holographic waveguide system based on multilayer body grating and preparation method thereof |
| CN114779397B (en)* | 2022-04-29 | 2024-04-26 | 北京枭龙科技有限公司 | Single-layer grating waveguide device for realizing color display and near-eye display device |
| CN115016128B (en)* | 2022-08-08 | 2022-12-02 | 南京平行视界技术有限公司 | Holographic waveguide HUD device based on polarizer |
| CN115097637B (en)* | 2022-08-26 | 2022-12-09 | 杭州光粒科技有限公司 | Head-up display |
| CN116893462B (en)* | 2023-09-08 | 2023-12-29 | 北京灵犀微光科技有限公司 | Preparation method of polarizer holographic grating and polarizer holographic grating |
| CN118465902B (en)* | 2024-06-28 | 2024-09-03 | 东南大学 | Method for preparing polarizer holographic grating realizing different diffraction efficiencies |
| CN120010043B (en)* | 2025-04-18 | 2025-07-25 | 东南大学 | A grating waveguide device and waveguide system based on PVG technology |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104656259A (en)* | 2015-02-05 | 2015-05-27 | 上海理湃光晶技术有限公司 | Conjugated narrow-band tri-phosphor staggered volume holographic grating waveguide near-to-eye optical display device |
| CN105487170A (en)* | 2016-01-19 | 2016-04-13 | 东南大学 | Holographic optical waveguide and holographic optical waveguide display device |
| WO2018096359A2 (en)* | 2016-11-28 | 2018-05-31 | Bae Systems Plc | Multiple waveguide structure for colour displays |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2196729A1 (en)* | 2008-12-12 | 2010-06-16 | BAE Systems PLC | Improvements in or relating to waveguides |
| US8989535B2 (en)* | 2012-06-04 | 2015-03-24 | Microsoft Technology Licensing, Llc | Multiple waveguide imaging structure |
| US9664905B2 (en)* | 2013-06-28 | 2017-05-30 | Microsoft Technology Licensing, Llc | Display efficiency optimization by color filtering |
| US9891436B2 (en)* | 2016-02-11 | 2018-02-13 | Microsoft Technology Licensing, Llc | Waveguide-based displays with anti-reflective and highly-reflective coating |
| CN105807348B (en)* | 2016-05-23 | 2018-07-06 | 东南大学 | A kind of reflection volume holographic grating waveguiding structure |
| US20170373459A1 (en)* | 2016-06-27 | 2017-12-28 | University Of Central Florida Research Foundation, Inc. | Volume polarization grating, methods of making, and applications |
| WO2019104046A1 (en)* | 2017-11-27 | 2019-05-31 | University Of Central Florida Research | Optical display system, method, and applications |
| CN109917547B (en)* | 2018-10-31 | 2024-06-18 | 东南大学 | Full-color waveguide coupling near-to-eye display structure based on color polarizer grating, preparation method and AR wearable device |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104656259A (en)* | 2015-02-05 | 2015-05-27 | 上海理湃光晶技术有限公司 | Conjugated narrow-band tri-phosphor staggered volume holographic grating waveguide near-to-eye optical display device |
| CN105487170A (en)* | 2016-01-19 | 2016-04-13 | 东南大学 | Holographic optical waveguide and holographic optical waveguide display device |
| WO2018096359A2 (en)* | 2016-11-28 | 2018-05-31 | Bae Systems Plc | Multiple waveguide structure for colour displays |
| Title |
|---|
| "A full-color eyewear display using planar waveguides with reflection volume holograms";MUKAWA H，AKUTSU K，et al;《Journal of the Society for Information Display》;20090317;第185-191页，图11-12* |
| "Polarization volume grating with high efficiency and large diffraction angle";YISHI WENG等;《OPTICS EXPRESS》;20160808;第24卷(第16期);第17752-17758页* |
| MUKAWA H，AKUTSU K，et al."A full-color eyewear display using planar waveguides with reflection volume holograms".《Journal of the Society for Information Display》.2009,* |
| Publication number | Publication date |
|---|---|
| CN109917547A (en) | 2019-06-21 |
| WO2020088055A1 (en) | 2020-05-07 |
| Publication | Publication Date | Title |
|---|---|---|
| CN109917547B (en) | Full-color waveguide coupling near-to-eye display structure based on color polarizer grating, preparation method and AR wearable device | |
| CN113341569B (en) | A polarization multiplexing diffractive waveguide large field angle imaging system and method | |
| Gu et al. | Holographic waveguide display with large field of view and high light efficiency based on polarized volume holographic grating | |
| Zhan et al. | Pancharatnam–Berry optical elements for head-up and near-eye displays | |
| US20240103440A1 (en) | Method for Holographic Mastering and Replication | |
| EP3123215B1 (en) | Bragg liquid crystal polarization gratings | |
| US10095045B2 (en) | Waveguide comprising a bragg polarization grating | |
| US10386558B2 (en) | Polarization conversion systems with geometric phase holograms | |
| US12092850B2 (en) | Patterned anisotropic films and optical elements therewith | |
| JPWO2019178614A5 (en) | ||
| CN110824613A (en) | Polarization multiplexing waveguide display device | |
| TWI839640B (en) | Optical systems including light-guide optical elements for two-dimensional expansion with retarder element | |
| CN120641797A (en) | Highly efficient reflective liquid crystal polarization holograms for multiple wavelengths | |
| Cho et al. | Bragg-Berry flat reflectors for transparent computer-generated holograms and waveguide holography with visible color playback capability | |
| Moran et al. | The directed self-assembly of reflective liquid crystalline polymer films to form polarization-independent diffractive optical elements | |
| Weng et al. | Liquid-crystal polarization volume gratings technology and its applications in diffractive optical waveguides systems for augmented reality | |
| CN116841077B (en) | A depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens | |
| CN114690287B (en) | Liquid crystal polarizing lens group, preparation method and multi-focal plane display system | |
| Weng et al. | 40.3: Polarization‐dependent Binocular Waveguide Display with Patterned Cholesteric Liquid Crystal Optics | |
| CN114902114A (en) | Light guide element and image display device | |
| US12443041B2 (en) | Optical elements for reducing visual artifacts in diffractive waveguide displays and systems incorporating the same | |
| US20230288706A1 (en) | Optical elements for reducing visual artifacts in diffractive waveguide displays and systems incorporating the same | |
| Zhang et al. | 56.1: Invited Paper: A Holographic Waveguide Display with Polarization Volume Gratings | |
| WO2024204164A1 (en) | Wavelength-selective retardation plate and optical element | |
| Li | Chromatic and Achromatic Polarization Control for Next-Generation Displays |
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