阅读说明：本技术 偏振复用波导显示器件 (Polarization multiplexing waveguide display device ) 是由 张宇宁 崔静怡 翁一士 于 2019-11-13 设计创作，主要内容包括：本发明公开了一种偏振复用波导显示器件,由入耦合装置、出耦合装置以及波导组成,使用了彩色偏振体全息光栅作为波导的耦合装置,相较于传统的全息耦合光栅,该新型光栅利用液晶的自组装效应和各向异性有着高衍射效率,大衍射角度,可工作在较宽的波长与角度带宽,同时具有偏振选择性,结合所公开的双层波导结构,本发明应用于近眼显示应用,可实现大视场角、高透明度、高效率的彩色图像传输。(The invention discloses a polarization multiplexing waveguide display device, which consists of an in-coupling device, an out-coupling device and a waveguide, wherein a color polarizer holographic grating is used as the coupling device of the waveguide, compared with the traditional holographic coupling grating, the novel grating has high diffraction efficiency and large diffraction angle by utilizing the self-assembly effect and anisotropy of liquid crystal, can work at wider wavelength and angle bandwidth, simultaneously has polarization selectivity, and is combined with the disclosed double-layer waveguide structure.)

1. A polarization multiplexed waveguide display device, characterized by: the device consists of an in-coupling device, an out-coupling device and a waveguide (5); wherein the in-coupling device consists of a left-handed circularly polarized light in-coupling grating (6) and a right-handed circularly polarized light in-coupling grating (7); the out-coupling device consists of a left-handed circular polarized light out-coupling grating (8) and a right-handed circular polarized light out-coupling grating (9); the shape and size of the left-handed polarized light in-coupling grating (6), the right-handed circularly polarized light in-coupling grating (7), the left-handed circularly polarized light out-coupling grating (8) and the right-handed circularly polarized light out-coupling grating (9) are completely the same; the in-coupling device and the out-coupling device are positioned on the horizontal symmetrical position of the waveguide (5); the left-handed polarized light in-coupling grating (6) and the left-handed polarized light out-coupling grating (8) can diffract left-handed circularly polarized light, and right-handed circularly polarized light directly penetrates through the grating; the right-handed polarized light in-coupling grating (7) and the right-handed polarized light out-coupling grating (9) can diffract right-handed circularly polarized light, and left-handed circularly polarized light directly penetrates through the right-handed circularly polarized light.

2. A polarization multiplexed waveguide display device according to claim 1, wherein: two layers of wave plates are arranged between the left-handed circularly polarized light in-coupling grating (6) and the waveguide (5), namely an 1/4 wave plate for generating left-handed circularly polarized light and a 1/4 wave plate for generating right-handed circularly polarized light; and two layers of wave plates, namely an 1/4 wave plate (10) for generating left-handed circular polarized light and a 1/4 wave plate (11) for generating right-handed circular polarized light, are arranged between the left-handed circular polarized light outcoupling grating (8) and the waveguide (5).

Technical Field

The invention relates to a polarization multiplexing waveguide display device which is used for realizing high-efficiency image transmission and perspective capability in an AR wearable device and has polarization selectivity, so that the AR wearable device can realize a large field angle.

Background

In recent years, AR technology has received great attention due to its great potential application value in medical, education, games, navigation, and the like. By transmitting both the virtual image and the real image to the human eye, the AR device provides the observer with an immersive experience. One key hardware component of an AR device is an optical coupling device that couples and transmits virtual and real images to the human eye.

Some light coupling structures have been proposed that are made using reflective or diffractive holographic optical elements. Among them, optical diffraction gratings are the most common. When applied in a waveguide-coupled near-eye display system, the diffraction grating may couple an incident light beam from the microdisplay into the waveguide. The diffraction grating has a large diffraction angle and also has angle selectivity and wavelength selectivity, which ensures that the light beam can propagate in the waveguide with high efficiency when the total internal reflection condition is satisfied. Also in this method, a transmissive or reflective diffraction grating is used to direct light waves propagating by total internal reflection in the planar glass substrate. The planar lightwave coupling device which is relatively light and thin and has a large eye movement range can be manufactured by utilizing the holographic optical waveguide technology. In view of the diversity of optical diffraction elements, Holographic Volume Gratings (HVGs) have unique advantages and are therefore widely used as coupling devices in waveguides. Typical holographic gratings may be made by recording an interference pattern on a holographic recording material (e.g., photopolymer, dichromated gelatin, etc.). When a light beam satisfying the bragg condition is irradiated onto the HVG, single-order diffraction with high diffraction efficiency can occur, and the diffraction angle is large, which is an important characteristic of the HVG. Meanwhile, HVG has high transmittance for ambient light due to its narrow bandwidth and strict angular selectivity. However, the short angular and wavelength bandwidths limit the size of the field angle FOV and, when used in waveguide-coupled display systems, also limit the implementation of full-color transmission. The difference in birefringence can determine the angle and wavelength bandwidth of the bulk grating. The polarizer holographic grating (PVG) prepared by adopting the liquid crystal material has larger birefringence difference, thereby providing larger angular bandwidth than the traditional HVG and further realizing larger field angle.

Although the waveguide structure prepared by using PVG can provide a larger field angle by itself, the FOV can only reach about 30 ° due to the influence of the refractive index of the waveguide material, the refractive index of the grating material and the waveguide shape. For some applications, the field angle needs to be further expanded.

Disclosure of Invention

The technical problem to be solved is as follows: aiming at the defects of the prior art, the invention provides a polarization multiplexing waveguide display device, which is used for solving the problem that the FOV is limited by a waveguide and further expanding the FOV. It should be noted that the present invention is described by taking the example of expanding the horizontal FOV at a single wavelength, but the present invention can also be used to expand the horizontal FOV at multiple wavelengths, so that full-color transmission with a large field angle in a two-dimensional plane can be realized.

In order to achieve the purpose, the invention adopts the following technical scheme: a polarization multiplexing waveguide display device comprises an in-coupling device, an out-coupling device and a waveguide; wherein the in-coupling device consists of a left-handed circularly polarized light in-coupling grating and a right-handed circularly polarized light in-coupling grating; the out-coupling device consists of a left-handed circular polarized light out-coupling grating and a right-handed circular polarized light out-coupling grating; the shape and size of the left-handed polarized light in-coupling grating, the right-handed circularly polarized light in-coupling grating, the left-handed circularly polarized light out-coupling grating and the right-handed circularly polarized light out-coupling grating are completely the same; the in-coupling device and the out-coupling device are positioned on the horizontal symmetrical position of the waveguide; the left-handed polarized light in-coupling grating and the left-handed polarized light out-coupling grating can diffract left-handed polarized light, and right-handed polarized light directly penetrates through the grating; the right-handed polarized light in-coupling grating and the right-handed polarized light out-coupling grating can diffract right-handed circularly polarized light, and left-handed circularly polarized light directly penetrates through the right-handed circularly polarized light.

Preferably, two wave plates are arranged between the left-handed circularly polarized in-coupling grating and the waveguide, wherein the two wave plates are 1/4 wave plate for generating left-handed circularly polarized light and 1/4 wave plate for generating right-handed circularly polarized light; and two layers of wave plates are arranged between the left-handed circularly polarized light outcoupling grating and the waveguide, namely an 1/4 wave plate for generating left-handed circularly polarized light and a 1/4 wave plate for generating right-handed circularly polarized light.

It should be noted that the grating periods of the left-handed grating and the right-handed grating are obviously different because the left-handed polarized light and the right-handed polarized light are required to propagate in the waveguide in the same angular range, and the incident angles of the left-handed polarized light and the right-handed polarized light incident on the incoupling device are different. The specific grating period needs to be calculated according to the bragg formula. The Bragg formula is as in formula (1):

2n_effΛ_bsinξ＝λ (1)

therefore, the required grating period can be found by the following equation:

Λ_b＝λ/(2*n_eff*sinξ) (2)

n_effrepresents the equivalent refractive index of the birefringent material used for the grating; lambda_bRepresenting the horizontal period length of the grating in the x-direction, ξ representing the angle of the incident ray with the plane of periodic refractive index in the PVG structure at which the diffraction efficiency is at its maximum, and λ representing the bragg wavelength in vacuum.

Has the advantages that:

compared with the traditional holographic coupling grating, the novel grating has high diffraction efficiency and large diffraction angle by utilizing the self-assembly effect and anisotropy of liquid crystal, can work at wider wavelength and angle bandwidth, has polarization selectivity, is applied to near-eye display application and can realize color image transmission with large field angle, high transparency and high efficiency by combining the disclosed double-layer waveguide structure.

Drawings

FIG. 1 illustrates a polarization multiplexed waveguide display device;

FIG. 2 shows the structure of PVG;

figure 3 shows an incoupling device made of PVG;

figure 4 shows an outcoupling means made of PVG;

FIG. 5 shows an improved structure for avoiding crosstalk;

wherein: 1. a microdisplay; 2 right-handed circular deviation component; 3. a left-handed circular deviation member; 4. a lens; 5. a waveguide; 6. left-handed circularly polarized light enters the coupling grating; 7. right-handed circularly polarized light enters the coupling grating; 8. left-handed circularly polarized light out-coupling grating; 9. the right-handed circularly polarized light is output to the coupling grating; 10. 1/4 wave plate producing left-handed circular polarization; 11. producing an 1/4 waveplate with right-handed circular polarization.

Detailed Description

The present invention will be further described with reference to the accompanying drawings.