AR equipment, display control method and computer storage medium

Abstract

The embodiment of the invention discloses AR equipment, a display control method and a computer storage medium. According to the AR equipment, 3D display of binocular parallax can be achieved only through one optical machine, and double optical machines or complex light splitting optical path design does not need to be adopted. The light machine regulates and controls the original images of the left eye and the right eye into left-hand circularly polarized light and right-hand circularly polarized light through the polarization assembly, and then the left-hand circularly polarized light and the right-hand circularly polarized light are projected to the polarization holographic grating through the The polarization holographic grating diffracts and couples polarized light with matched rotation into the light transmission medium by utilizing rotation selectivity of the spiral structure, polarized light with different rotation is transmitted to left and right eye imaging areas along independent paths in the light transmission medium, and finally a 3D image with parallax is formed. The single optical machine is matched with the polarization holographic grating, the number of optical machines is fundamentally reduced, the size, weight and power consumption of AR equipment are greatly reduced, meanwhile, the problems of optical path complexity and mass production caused by additional light splitting elements are solved, and on the premise that the 3D display effect is guaranteed, the equipment is light, thin and high in cost performance.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the field of AR devices, in particular to an AR device, a display control method and a computer storage medium. BACKGROUND

[0002] With the rapid development of science and technology, augmented reality (AR) technology gradually enters the public view, bringing a new experience to people's life and work. As the core carrier of AR technology, AR glasses can cleverly fuse virtual information with the real world, showing great application potential in education, medicine, industry, entertainment and many other fields. In addition to the pursuit of AR glasses goals such as thinness and superior display effect, 3D display is also a function that people value greatly. It not only enables users to experience more realistic and immersive virtual scenes, enhancing the fusion effect of virtual information and the real world, but also provides a more rich and vivid visual experience in professional fields such as 3D modeling, virtual assembly, 3D games, and daily entertainment, greatly expanding the application range and value of AR glasses.

[0003] 3D display technology mainly uses the principle of binocular disparity to enable the human brain to perceive 3D information of an object. Since the left and right eyes of a person have a certain pupil distance, the angle when looking at the same object will be slightly different, so the images obtained will be different. The brain can perceive the 3D information of the object after processing the binocular images with parallax. The existing 3D display scheme applied to AR glasses is a dual-optical machine scheme, in which two optical machines are responsible for displaying images on left and right waveguide sheets. Only a set of images with parallax needs to be projected onto the left and right waveguide sheets simultaneously or at different times, and the user can see the projected image with 3D effect.

[0004] The optical machine is the largest component in terms of volume, cost, power consumption and heat generation in AR glasses. The dual-optical machine scheme increases the cost of AR glasses products, increases the volume and weight of AR glasses, and the increase in power consumption also reduces the battery life of AR glasses. A large amount of heat also affects the wearing comfort. These all affect the user experience and are contrary to the pursuit of thinness and high cost performance. SUMMARY

[0005] Embodiments of the present application provide an AR device, a display control method and a computer storage medium, which fundamentally reduce the number of optical machines by using a single optical machine in combination with a polarization volume holographic grating, thereby greatly reducing the volume, weight and power consumption of the AR device.

[0006] The first aspect of the embodiments of the present application provides an AR device, which comprises an optical machine and a polarization volume holographic grating, and the optical machine comprises a display screen, a polarizing component and a projection lens. The polarization volume holographic grating is arranged at a coupling-in region of a light transmission medium of the AR device, and an internal structure of the polarization volume holographic grating is a helical structure with a specific handedness. The display screen is configured to output light signals corresponding to an original image, the polarizing component is configured to regulate the light signals into polarized light signals with different handednesses, and the polarized light signals are projected to the polarization volume holographic grating in the coupling-in region of the light transmission medium through the projection lens. The polarization volume holographic grating is configured to diffract the polarized light signals with the same handedness as the helical structure to the light transmission medium, so that the polarized light signals with different handednesses are projected to the left and right eyes of a person to display left and right eye parallax images of the original image.

[0007] The second aspect of the embodiments of the present application provides a display control method, which is applied to the AR device of the first aspect, the AR device including an optical machine and a polarization volume holographic grating, the optical machine including a display screen, a polarizing component, and a projection lens; the polarization volume holographic grating is arranged at a coupling-in region of a light transmission medium of the AR device, and an internal structure of the polarization volume holographic grating is a helical structure with a specific handedness. The method includes: controlling the display screen to output light signals corresponding to an original image, so that the polarizing component regulates the light signals into polarized light signals with different handednesses, and the polarized light signals are projected to the polarization volume holographic grating in the coupling-in region of the light transmission medium through the projection lens; based on the polarization volume holographic grating diffracting the polarized light signals with the same handedness as the helical structure to the light transmission medium, so that the polarized light signals with different handednesses are projected to the left and right eyes of a person to display left and right eye parallax images of the original image.

[0008] The third aspect of the embodiments of the present application provides a computer storage medium, and the computer storage medium stores instructions, which, when executed on an AR device, cause the AR device to perform the method of the second aspect.

[0009] From the above technical solutions, it can be seen that the embodiments of the present application have the following advantages: The AR device only needs one optical engine to realize binocular parallax 3D display, without using double optical engines or complex light splitting optical path design. The optical engine adjusts the left and right eye original images into left-handed and right-handed circularly polarized light through a polarizing component, and then projects them to a polarization volume holographic grating through a projection lens. The polarization volume holographic grating uses the handedness selectivity of its spiral structure to diffract and couple the polarized light with matching handedness into the light transmission medium. The polarized light with different handedness is transmitted along independent paths in the light transmission medium to the left and right eye imaging areas, and finally forms a 3D image with parallax. This single optical engine combined with the polarization volume holographic grating scheme fundamentally reduces the number of optical engines, greatly reduces the volume, weight and power consumption of the AR device, and avoids the complexity of the optical path and the production difficulty caused by additional light splitting elements. Under the premise of ensuring 3D display effect, the device is light and thin, and has high performance price ratio, which is more in line with the market demand for portability and practicality of AR devices. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 An exemplary structural schematic diagram of an AR device in embodiments of the present application; Figure 2 Schematic diagrams corresponding to various exemplary implementation manners of the pixels in the first pixel region and the pixels in the second pixel region alternately distributed on the display screen in embodiments of the present application; Figure 3 Exemplary schematic diagrams corresponding to the microstructures of two liquid crystal polarization volume holographic gratings with different handedness and different polarization responses in embodiments of the present application; Figure 4 An exemplary schematic diagram corresponding to the structure obtained based on a preparation method of the polarization volume holographic grating in embodiments of the present application; Figure 5 An exemplary structural schematic diagram of another AR device and the technical implementation thereof in embodiments of the present application; Figure 6 A flowchart of a display control method in embodiments of the present application. DETAILED DESCRIPTION

[0011] The AR device, display control method and computer storage medium provided in embodiments of the present application fundamentally reduce the number of optical engines based on a single optical engine combined with a polarization volume holographic grating, greatly reducing the volume, weight and power consumption of the AR device.

[0012] In some related solutions, AR glasses directly project two images with parallax by two optical machines, and the two images with parallax are coupled into two lenses to realize binocular parallax display. This double optical machine solution increases the cost of AR glasses, and also increases the volume and weight of AR glasses. The increase in power consumption also reduces the endurance time of AR glasses, and a large amount of heat also affects the wearing comfort. These all affect the user experience, which is contrary to the pursuit of lightness, thinness and high cost performance.

[0013] In other related solutions, two light splitting paths are added in one optical machine system, which are projected in two directions and coupled into two lenses to realize binocular parallax display. However, this solution does not essentially save space, but increases the complexity of the optical path. Compared with single direction projection, it increases the splitting prism, polarization device and wave plate, which increases the complexity of the optical machine. Compared with the above-mentioned double optical machine solution, there is no obvious improvement in space, weight, efficiency and other performances. On the contrary, due to the introduction of non-standard process, it is difficult to effectively mass-produce.

[0014] In view of the technical defects existing in the above related solutions, an AR device is provided in the embodiments of the present application. In an embodiment of the AR device, the AR device includes an optical machine and a polarization volume holographic grating. The optical machine includes a display screen, a polarizing component, and a projection lens. The AR device can be AR glasses or other AR devices, such as AR helmets, AR headsets, and other wearable AR devices. These devices superimpose virtual information onto the real environment to provide users with immersive augmented reality experiences. The application of the polarization volume holographic grating can optimize the optical display effect and improve the clarity and stereoscopic effect of the image, meeting the use requirements in different scenarios.

[0015] The polarization volume holographic grating is arranged at a coupling-in region of an optical transmission medium of the AR device, and the internal structure of the polarization volume holographic grating is a helical structure with a specific handedness. The helical structure of the polarization volume holographic grating refers to a periodic arrangement structure formed by self-assembly of chiral liquid crystal molecules under specific conditions. The handedness includes rotation characteristics such as left-handedness and right-handedness, and the specific handedness is determined by the inherent characteristics of the chiral liquid crystal molecules and the control parameters in the preparation process. When the period of the helical structure matches the wavelength of the incident light, the polarization volume holographic grating can selectively diffract the polarization light with specific handedness.

[0016] The light transmission medium refers to a medium capable of transmitting optical signals therein, for example, the waveguide lens of the AR device, which can stably propagate the optical signals inside and guide them to the coupling-out area through total reflection and the like; the light transmission medium can also be a folded light path system composed of free-form mirror groups, which is designed by the angles and curved surface parameters of multiple mirror groups to make the left-handed and right-handed circularly polarized light diffracted by the polarization volume holographic grating respectively reflect and transmit along the preset paths, and finally accurately project into the left and right eye imaging areas; the light transmission medium can also be a fiber bundle array, which couples the different handedness polarized light diffracted in the coupling-in area into corresponding fiber bundles, realizes directional transmission of the optical signals through the ordered arrangement of the fiber bundles, and then projects the images to the human eyes through the optical components of the fiber bundle output ends.

[0017] The coupling-in area of the light transmission medium refers to a specific area in the light transmission medium for receiving external input optical signals and coupling them into the medium for transmission, which needs to meet the physical conditions and structural design requirements of high-efficiency coupling of optical signals. In this embodiment, the coupling-in area of the light transmission medium is specifically the area provided with the polarization volume holographic grating, and its core function is to stably guide the polarized light signals projected by the light machine into the light transmission medium through the selective diffraction of the polarization volume holographic grating on the polarized light of specific handedness.

[0018] The display screen of the AR device is used to output the optical signals corresponding to the original images, and the polarizing component is used to regulate the optical signals output by the display screen into polarized light signals of multiple different handedness, and project the polarized light signals into the polarization volume holographic grating in the coupling-in area of the light transmission medium through the projection lens.

[0019] The polarizing component regulates the optical signals into polarized light signals of specific handedness, and the principle is to modulate the polarization state of the optical signals through internal polarization conversion structures or wave plates and other optical elements. Specifically, when the optical signals output by the display screen are in a non-polarized state, the polarizing component can first convert them into linearly polarized light through a linear polarizer, and then rotate the polarization direction of the linearly polarized light by 90 degrees or 45 degrees by using a wave plate, thereby forming circularly polarized light; if the optical signals output by the display screen are in a linearly polarized state, the polarizing component can directly adjust the polarization direction of the linearly polarized light by using a wave plate, so that the electric field vector of the linearly polarized light rotates at a fixed angular velocity in a plane perpendicular to the propagation direction, forming left-handed or right-handed circularly polarized light. This regulation process needs to ensure that the handedness of the polarized light signal matches the handedness of the spiral structure of the polarization volume holographic grating, so as to realize high-efficiency diffraction coupling.

[0020] Among them, the linear polarizer can absorb linearly polarized components in one direction through a high-molecular absorption type linear polarizer or a metal wire grating linear polarizer, and finally only allow linearly polarized light in a specific polarization direction to pass through.

[0021] The projection lens projects the regulated polarized light signal to the coupling-in area of the light transmission medium at a specific angle. The focal length, aperture and other optical parameters of the projection lens need to be designed in coordination with the diffraction efficiency of the polarization volume holographic grating, the refractive index of the light transmission medium and other parameters to ensure that the incident angle of the light signal at the coupling-in area meets the Bragg diffraction condition, thereby minimizing the energy loss of the light signal during the coupling process.

[0022] The polarization volume holographic grating is used to diffract the polarized light signal with a matching handedness to the handedness of the helical structure to the light transmission medium, so that the polarized light signals of multiple different handedness are projected to the left and right eyes of the human to display the left and right eye parallax images of the original image. When the polarized light signal with a specific handedness is incident to the polarization volume holographic grating, the helical structure inside the grating will resonate with the electric field vector of the polarized light, causing the polarized light signal that meets the handedness matching condition to undergo Bragg diffraction, changing its propagation direction and coupling into the inside of the light transmission medium; the polarized light signal with unmatched handedness will be directly transmitted or reflected and will not enter the light transmission medium.

[0023] The "holographic" refers to a technology that records all information (including amplitude, phase and polarization state, etc.) of light emitted by an object in the form of interference fringes on a photosensitive medium by using the interference and diffraction principles of light, and then reproduces a three-dimensional image of the object through irradiation with specific light. In the preparation process of the liquid crystal polarization volume holographic grating in this embodiment, the polarization holographic exposure step is based on this principle: by setting up an exposure light path containing two coherent polarized lights, the two lights are made to interfere on the surface of the light-controlled orientation layer film to form interference fringes with a spatial periodic distribution, which will guide the subsequent coated liquid crystal molecules to arrange in a specific pattern. This orientation method based on holographic technology can accurately control the arrangement period and direction of the liquid crystal molecules, so that the finally solidified grating has a selective diffraction response to specific polarization state light, i.e., only left-handed or right-handed circularly polarized light is diffracted, while the other handedness of circularly polarized light remains transparent. This is one of the technical foundations for realizing single-light machine binocular 3D display in this embodiment.

[0024] This selective diffraction mechanism can effectively separate left-handed and right-handed circularly polarized light, corresponding to the parallax images of the left and right eyes respectively, and thus realize 3D display effect. The light signal propagates to the coupling-out area inside the light transmission medium through total reflection, mirror reflection or optical fiber bundle conduction, etc. The optical structure of the coupling-out area (such as a polarization volume holographic grating or other diffraction elements symmetrical to the structure of the coupling-in area) will diffract the light signal again, so that it exits from the light transmission medium and is projected to the pupil position of the human eye, and finally forms a clear 3D image on the retina.

[0025] The formation of "parallax" in the parallax images of the left and right eyes can be achieved by the display screen of the optical engine outputting the left-eye original image and the right-eye original image with a preset pixel offset, respectively. Specifically, the left-eye original image and the right-eye original image are two sets of image data generated by rendering based on the same virtual scene model according to the perspective difference corresponding to the interpupillary distance: in the rendering process, the three-dimensional coordinate system of the virtual scene takes the left and right pupil centers as the observation origins, respectively, to calculate the projection coordinates of each object in the scene, so that the two sets of images have a pixel offset of 1-6 cm (corresponding to the average interpupillary distance range of adults) in the horizontal direction while keeping the vertical direction coordinates consistent. When the polarizing component regulates the left-eye original image into left-circular polarized light and the right-eye original image into right-circular polarized light, the two polarized light signals are projected onto the polarization volume holographic grating through the projection lens, and the grating diffracts the left-circular polarized light into the transmission path corresponding to the left eye and the right-circular polarized light into the transmission path corresponding to the right eye according to the rotational matching principle, so as to finally form two image points with parallax on the human retina. The brain perceives the three-dimensional sense of the virtual scene through the fusion of the two image points.

[0026] As Figure 1 An exemplary structure of an AR device is shown, the optical engine of the AR device includes components such as a projection lens, a polarizing component, and a micro display screen, and is also configured with a waveguide sheet and a polarization volume holographic grating. The polarization response in-coupling grating in the polarization volume holographic grating is arranged in the in-coupling area of the waveguide sheet, the left-eye polarization response out-coupling grating is arranged in the in-coupling area corresponding to the left eye of the human being, and the right-eye polarization response out-coupling grating is arranged in the in-coupling area corresponding to the right eye of the human being.

[0027] Based on the structure shown, when the micro display screen outputs the light signal corresponding to the left-eye original image and the light signal corresponding to the right-eye original image, the polarizing component first converts the light signal corresponding to the left-eye original image into left-circular polarized light and the light signal corresponding to the right-eye original image into right-circular polarized light; the projection lens synchronously projects the two circular polarized light signals onto the polarization volume holographic grating in the in-coupling area of the waveguide sheet. The left-circular response spiral structure inside the grating selectively diffracts the left-circular polarized light, so that it is coupled into the waveguide sheet and transmitted along a first preset path, and finally projected onto the left eye of the human being after being diffracted by the left-eye polarization response out-coupling grating. At the same time, the right-circular response spiral structure inside the grating selectively diffracts the right-circular polarized light, so that it is coupled into the waveguide sheet and transmitted along a second preset path, and finally projected onto the right eye of the human being after being diffracted by the right-eye polarization response out-coupling grating. Since the images received by the left and right eyes are generated by rendering based on different perspectives of the same virtual scene, there is a pixel offset in the horizontal direction (such as a perspective difference corresponding to an interpupillary distance of 3-5 cm), and the brain can perceive the three-dimensional sense of the virtual scene by fusing the two sets of images with parallax.

[0028] Therefore, in the embodiment, the AR device only needs one optical engine to realize binocular parallax 3D display, without using double optical engines or complex optical path design. The optical engine adjusts the left and right eye original images into left-handed and right-handed circularly polarized light through the polarizing component, and then projects them to the polarization volume holographic grating through the projection lens. The polarization volume holographic grating uses the handedness selectivity of its spiral structure to diffract and couple the polarized light with matching handedness into the light transmission medium, and the polarized light with different handedness is transmitted along independent paths in the light transmission medium to the left and right eye imaging areas, and finally forms a 3D image with parallax. This single optical engine combined with the polarization volume holographic grating scheme fundamentally reduces the number of optical engines, greatly reduces the volume, weight and power consumption of the AR device, and avoids the optical path complexity and production difficulties caused by additional optical elements. Under the premise of ensuring 3D display effect, the device is light and thin and has high cost performance, which is more in line with the portability and practicality requirements of the market for AR devices.

[0029] In an optional implementation of the above embodiment, the display screen is specifically configured to cyclically and alternately output light signals corresponding to the left eye original images for the left eye and light signals corresponding to the right eye original images for the right eye. Based on this, the polarizing component can adjust the light signals corresponding to the left eye original images into left-handed circularly polarized light under the control of the first signal while the display screen outputs the light signals corresponding to the left eye original images, and adjust the light signals corresponding to the right eye original images into right-handed circularly polarized light under the control of the second signal while the display screen outputs the light signals corresponding to the right eye original images.

[0030] For example, the micro display screen of the AR glasses can be controlled to display the left eye original image in the first frame, the right eye original image in the second frame, the left eye original image in the third frame, and the right eye original image in the fourth frame, and so on, to cyclically and alternately display the left eye original image and the right eye original image in this time sequence. At the same time that the micro display screen outputs the light signals corresponding to the left eye original images, the polarizing component converts the light signals passing through the polarizing component into left-handed circularly polarized light under the control of the first signal; at the same time that the micro display screen outputs the light signals corresponding to the left eye original images, the polarizing component converts the light signals passing through the polarizing component into right-handed circularly polarized light under the control of the second signal.

[0031] The control mode of the polarizing component can be electric control or thermal control, and the specific control logic and technical principles are described in detail below.

[0032] By the above-mentioned electric control or thermal control mode, the polarizing assembly can synchronously control the corresponding light signals to be left-handed or right-handed circularly polarized light matching the rotation of the polarization volume holographic grating when the display screen alternately outputs the left-eye and right-eye original images, ensuring that the two-way polarized light signals are diffracted by the grating to the left-eye and right-eye paths in the light transmission medium, and finally realizing stable 3D display under a single light engine. This alternating control mode not only simplifies the light engine structure, but also avoids the crosstalk problem of two-way light signals in the double light engine scheme, further improving the clarity and stereoscopic effect of 3D images, and providing users with a better immersive experience.

[0033] In some optional embodiments, the first signal and the second signal can include first and second electric control signals, i.e., different strategies of polarization state conversion of different light signals by the polarizing assembly are controlled by electric signals (such as voltage). Specifically, the first electric control signal is used to control the first preset angle between the optical axis direction of the wave plate and the linear polarization direction in the polarizing assembly, so that the left-eye original image corresponding light signal is converted into left-handed circularly polarized light based on the first preset angle. The second electric control signal is used to control the second preset angle between the optical axis direction of the wave plate and the linear polarization direction in the polarizing assembly, so that the right-eye original image corresponding light signal is converted into right-handed circularly polarized light based on the second preset angle.

[0034] The principle of electric control mode to change the polarization state of light signal is to change the angle between the optical axis direction of the wave plate and the linear polarization direction in the polarizing assembly by electric signal to realize the conversion of light signal polarization state, i.e., by applying voltage to the wave plate, the molecular arrangement direction of liquid crystal molecules or electro-optic crystals in the wave plate is changed, and then the relative angle between its optical axis and the polarization direction of incident light is adjusted. The wave plate can be a quarter wave plate, a half wave plate or other optical elements with electro-optic effect.

[0035] Taking a quarter wave plate as an example, when the optical axis of the wave plate and the polarization direction of the incident linearly polarized light are at an angle of 45 degrees, the linearly polarized light can be converted into circularly polarized light, and the positive and negative directions of the angle determine the rotation of the circularly polarized light: if the optical axis rotates 45 degrees (first preset angle) clockwise relative to the linear polarization direction, left-handed circularly polarized light is output; if it rotates 45 degrees (second preset angle) counterclockwise, right-handed circularly polarized light is output. The light signal output by the display screen can be linearly polarized light, or non-polarized light converted into linearly polarized light by a linear polarizer and then transmitted to the quarter wave plate.

[0036] For example, the first electric control signal can represent that no voltage is applied to the polarizing component, and then the light signal passing through the polarizing component can be converted into left circularly polarized light. This is because the wave plate is pre-set with the optical axis direction at an angle of 45 degrees with the linear polarization direction of the incident light through the molecular orientation process (such as rubbing orientation method or photo-orientation method) in the preparation stage. In the case of no voltage, the wave plate keeps the optical axis direction at an angle of 45 degrees with the linear polarization direction. At this time, the linearly polarized light passing through the wave plate will generate a phase difference of 1 / 4 wavelength between o light and e light (o light and e light are two kinds of polarized light generated when light passes through anisotropic crystal), and thus be combined into left circularly polarized light.

[0037] The second electric control signal can represent that a voltage is applied to the polarizing component, and then the light signal passing through the polarizing component is converted into right circularly polarized light. This is because the molecular arrangement direction of the liquid crystal molecules or electro-optic crystals in the wave plate is deflected under the voltage drive, resulting in that the angle between the optical axis of the wave plate and the linear polarization direction of the incident light becomes -45 degrees (or equivalent to 135 degrees). At this time, the direction of the phase difference of 1 / 4 wavelength generated between o light and e light is reversed, and finally combined into right circularly polarized light.

[0038] This electric control method can quickly respond to the signal instruction and complete the switching of the polarization state within microseconds, which is precisely synchronized with the image output frame rate (usually 60Hz-120Hz) of the display screen, so as to ensure that the polarized light signals of the left eye original image and the right eye original image can be alternately and stably projected to the polarization volume holographic grating, and the problems of image crosstalk or display delay are avoided.

[0039] The light signal output by the display screen can also be circularly polarized light. At this time, the wave plate can adopt a half wave plate. Under the electric control method, the angle between the optical axis of the half wave plate and the polarization direction of the incident circularly polarized light is adjusted to realize the inversion of the circularly polarized light rotation.

[0040] For example, the left eye original image light signal and the right eye original image light signal alternately output by the display screen are both left circularly polarized light. At the same time when the display screen outputs the left eye original image light signal, the first electric control signal is controlled, such as representing that no voltage is applied to the polarizing component. At this time, the angle between the optical axis of the half wave plate and the polarization direction of the incident light is 0 degrees, and the circularly polarized light rotation remains unchanged, which is still left circularly polarized light. When the display screen outputs the right eye original image light signal, the second electric control signal is applied to the preset voltage, so that the optical axis of the half wave plate rotates 90 degrees relative to the polarization direction of the incident light. At this time, the left circularly polarized light is inverted after passing through the wave plate, and is converted into right circularly polarized light. That is, the light signal corresponding to the right eye original image is converted into right circularly polarized light, so as to meet the selective diffraction requirement of the polarization volume holographic grating for different rotation polarized light.

[0041] Similarly, if the left-eye original image light signal and the right-eye original image light signal alternately output by the display screen are both right-handed circularly polarized light, when the display screen outputs the left-eye original image light signal, a preset voltage is applied through the first electric control signal to rotate the optical axis of the half-wave plate by 90 degrees relative to the polarization direction of the incident light, converting the right-handed circularly polarized light into left-handed circularly polarized light; when the display screen outputs the right-eye original image light signal, no voltage is applied through the second electric control signal, so that the handedness of the right-handed circularly polarized light remains unchanged, thereby realizing the handedness separation of the left-eye and right-eye polarized light signals.

[0042] This polarization state control method based on an electrically controlled wave plate has a response speed of microseconds, which completely matches the frame alternation frequency of the display screen, ensures that the switching of the left-eye and right-eye parallax images has no delay and no crosstalk, and provides users with a smooth 3D visual experience.

[0043] In addition, the first signal and the second signal can also be a first thermal control signal and a second thermal control signal, respectively, that is, the polarization state of different light signals is converted by the polarization component through a thermodynamic signal (such as temperature) control. The change of the polarization state of the light signal by the thermal control method utilizes the temperature dependence of the refractive index of the thermochromic material or the phase change material such as the thermo-optic crystal in the polarization component.

[0044] For example, the wave plate is pre-set with a 45-degree angle between the optical axis direction and the linear polarization direction of the incident light through a molecular orientation process in the preparation stage, and the wave plate in the polarization component is prepared by using a thermo-optic polymer material. The ordinary light refractive index (no) and the extraordinary light refractive index (ne) of the material will change at different rates with temperature. In the absence of an external temperature field (i.e., the first thermal control signal is the room temperature environment), the product of the thickness and the refractive index difference (ne-no) of the wave plate satisfies the 1 / 4 wavelength condition. When the linearly polarized light is incident on the optical axis of the wave plate at a 45-degree angle, the linearly polarized light will be decomposed into e light parallel to the optical axis and o light perpendicular to the optical axis, and the amplitudes of the two are equal. Due to the different refractive indices of the wave plate for e light and o light, the propagation speeds are different. When the 1 / 4 wavelength condition is met, the e light and the o light will produce a 1 / 4 wavelength optical path difference at the exit surface of the wave plate, corresponding to a phase difference of π / 2. At this time, the vibration directions of the two beams of light are perpendicular to each other, the amplitudes are equal, and the phase difference is π / 2. After synthesis, circularly polarized light is formed. The 45-degree angle between the optical axis and the linear polarization direction of the incident light is the key to ensuring that the amplitudes of the e light and the o light are equal.

[0045] When the second thermal control signal is applied (e.g., the temperature of the waveplate is raised to a preset threshold, such as 50°C, by a micro-heating sheet), the ne of the thermo-optic polymer will significantly decrease with the increase of temperature, while the no remains basically unchanged, resulting in a decrease of the refractive index difference (ne-no). The product of the waveplate thickness and the refractive index difference no longer satisfies the 1 / 4 wavelength condition. At this time, the phase modulation effect of the waveplate on the incident light changes, thereby affecting the polarization state of the optical signal. For example, when the temperature rise causes the refractive index difference to decrease to half of the original value, the phase delay of the waveplate decreases from π / 2 to π / 4. At this time, by precisely controlling the temperature to cause the refractive index difference to change in the opposite direction (e.g., using a material with a negative thermo-optic coefficient, the ne-no changes from positive to negative as the temperature rises), the equivalent direction of the optical axis of the waveplate is reversed, and the phase difference direction of the linearly polarized light after passing through the waveplate is also reversed. The condition for synthesizing left-handed circularly polarized light changes to the condition for synthesizing right-handed circularly polarized light.

[0046] Alternatively, when the second thermal control signal causes the temperature of the waveplate to rise, the ne of the thermo-optic polymer significantly decreases with the increase of temperature (or the no significantly increases with the increase of temperature, depending on the material properties), resulting in a reversal of the sign of the refractive index difference (ne-no) (e.g., from a positive difference to a negative difference). At this time, the linearly polarized light still enters the optical axis direction at a 45-degree angle and is decomposed into e light and o light with equal amplitude. However, due to the reversal of the sign of the refractive index difference, the direction of the difference in propagation speed of the e light and the o light in the waveplate changes, and the phase difference direction also reverses (e.g., from e light leading o light by 1 / 4 wavelength to o light leading e light by 1 / 4 wavelength). This reversal of the phase difference direction, combined with the condition of equal amplitude, causes the linearly polarized light that originally synthesized left-handed circularly polarized light to finally synthesize right-handed circularly polarized light.

[0047] In short, when the waveplate is in a temperature environment corresponding to the first thermal control signal (e.g., room temperature), the product of the refractive index difference (ne-no) and the waveplate thickness satisfies the 1 / 4 wavelength condition, and the angle between the optical axis and the polarization direction of the incident linearly polarized light is a preset angle (e.g., 45 degrees). At this time, the linearly polarized light is synthesized into left-handed circularly polarized light after passing through the waveplate. When the waveplate is in a temperature environment corresponding to the second thermal control signal (e.g., a specific high temperature threshold), the directional change of ne or no of the waveplate material caused by temperature change causes the value or sign of the refractive index difference to change, and the direction of the phase delay is reversed, finally causing the linearly polarized light to be synthesized into right-handed circularly polarized light after passing through the waveplate.

[0048] In the thermal control method, the temperature change mainly adjusts the direction of the phase delay by changing the refractive index difference (ne-no) of the waveplate material, rather than directly changing the angle between the optical axis and the polarization direction of the incident linearly polarized light. This angle is fixed at 45 degrees during the preparation stage through a molecular orientation process (e.g., rubbing orientation method) and is not directly affected by temperature changes.

[0049] The thermal control method has the advantages of simple structure and no electromagnetic interference, and is suitable for AR device scenes with high electromagnetic compatibility requirements.

[0050] Regardless of the electric control or thermal control method, the core is to control the phase delay characteristics of the wave plate in the polarizing component to achieve precise conversion of the polarization of the incident light, ensure that the left-handed and right-handed circularly polarized light can be accurately diffracted and separated by the polarization volume holographic grating, and finally realize binocular parallax 3D display under a single light machine. This signal control mechanism not only simplifies the optical structure of the AR device, but also adjusts the parameters (such as voltage amplitude or temperature threshold) of the control signal in real time through software algorithms to adapt to different wavelengths of incident light (such as different wavelengths of RGB three primary color light), further improving the color restoration degree and 3D display effect of the image.

[0051] Among them, the angle between the above optical axis direction and the linear polarization direction of the incident light can be 45 degrees, but also other preset angles that can ensure that the linearly polarized light is decomposed into e light and o light with equal amplitude after passing through the wave plate, such as 135 degrees. Taking 135 degrees as an example, when the angle between the wave plate optical axis and the linear polarization direction of the incident light is 135 degrees, the linearly polarized light will also be decomposed into e light and o light with equal amplitude. At this time, if the wave plate satisfies the 1 / 4 wavelength phase delay condition and the refractive index difference sign remains unchanged, the circularly polarized light synthesized after the linearly polarized light passes through the wave plate has opposite handedness to that when the angle is 45 degrees: assuming that the synthesized left-handed circularly polarized light when the angle is 45 degrees, then when the angle is 135 degrees, due to the opposite vibration component directions of o light and e light, the phase difference direction remains unchanged, and the finally synthesized will be right-handed circularly polarized light. This flexible design of angle makes the polarizing component able to be adjusted according to the actual process precision during preparation and debugging, without the need to strictly limit it to 45 degrees, further reducing the production difficulty and cost.

[0052] Based on the foregoing embodiments, in another alternative implementation, the pixel-level polarization state of the display screen output light signal can also be controlled. Specifically, the display screen can output light signals corresponding to the left-eye original image for the left eye and light signals corresponding to the right-eye original image for the right eye in the first pixel area and the second pixel area of the display screen, respectively. The pixels in the first pixel area and the pixels in the second pixel area are alternately distributed on the display screen. That is, the pixels in the first pixel area and the pixels in the second pixel area are arranged in a row-column alternating manner, for example, two adjacent pixels on the display screen belong to the first pixel area and the second pixel area respectively, forming a distribution pattern similar to a chessboard.

[0053] For example, Figure 2A plurality of exemplary implementations of the pixels of the first pixel region and the pixels of the second pixel region being alternately distributed on the display screen are shown, where the gray squares represent the pixels of the first pixel region, and the white squares represent the pixels of the second pixel region. As shown in the left side of the figure, the pixels of the first pixel region and the pixels of the second pixel region are alternately distributed in a chessboard pattern. In the middle of the figure, the pixels of the first pixel region and the pixels of the second pixel region are alternately distributed column by column. In the right side of the figure, the pixels of the first pixel region and the pixels of the second pixel region are alternately distributed row by row.

[0054] Based on this pixel-level alternately distributed design, the polarization assembly can adopt a partitioned fixed polarization regulation manner: the polarization sub-units corresponding to the first pixel region are pre-set to regulate the light signal corresponding to the left-eye original image into left-handed circularly polarized light, and the polarization sub-units corresponding to the second pixel region are pre-set to regulate the light signal corresponding to the right-eye original image into right-handed circularly polarized light.

[0055] Therefore, this pixel-level polarization regulation manner does not need to rely on high-speed electrically controlled or thermally controlled switching assemblies, and can realize the separation of left-eye and right-eye polarized light signals only by pre-customized partitioned layout of the polarization assembly, which not only simplifies the optical system structure of the AR device, but also reduces the power consumption and cost of the device, while ensuring the real-time performance and clarity of 3D display.

[0056] One optional way for the polarization assembly to realize the above-mentioned pixel-level regulation is that the polarization assembly includes a first wave plate and a second wave plate, and the light signal corresponding to the left-eye original image is converted into left-handed circularly polarized light based on the first pre-set angle between the optical axis direction of the first wave plate and the linear polarization direction of the incident light, and the light signal corresponding to the right-eye original image is converted into right-handed circularly polarized light based on the second pre-set angle between the optical axis direction of the second wave plate and the linear polarization direction of the incident light.

[0057] Among them, the polarization state of the light signal output by the display screen can be arbitrary, for example, if the light signal output by the display screen is in a non-polarization state, the light signal is converted into a linear polarization state by a linear polarizer and then output to the first wave plate and the second wave plate; if the light signal output by the display screen is in a linear polarization state, the light signal is directly output to the first wave plate and the second wave plate.

[0058] For example, the first wave plate and the second wave plate can be quarter wave plates, i.e., the polarized component is configured with a plurality of quarter wave plates, wherein the optical axis direction of part of the quarter wave plates is at a first preset angle (such as +45°) with the linear polarization direction, which can realize the conversion of linearly polarized light into left circularly polarized light. The principle is that the electric field vibration direction of linearly polarized light can be decomposed into two perpendicular components, when the vibration direction of linearly polarized light is at +45° with the optical axis of the quarter wave plate, the electric field components are decomposed into o light along the optical axis direction and e light perpendicular to the optical axis direction, and the two will produce a phase difference of 1 / 4 wavelength when propagating in the wave plate. If the incident linearly polarized light is horizontally polarized (assuming the optical axis is along the +45° direction), the phase difference of the decomposed o light and e light is π / 2, and the e light phase leads the o light. When the two components exit the wave plate, the vector endpoint of the combined electric field will rotate counterclockwise to form left circularly polarized light.

[0059] And another part of the quarter wave plate has an optical axis direction at a second preset angle (such as -45°) with the linear polarization direction, then the e light phase lags behind the o light by π / 2, and the vector endpoint of the combined electric field rotates clockwise, thereby obtaining right circularly polarized light.

[0060] This polarization state control based on the optical axis direction provides a simple implementation for pixel-level polarization distribution. Only the optical axis direction of the quarter wave plate in different regions of the polarized component needs to be designed differently, which can realize the accurate polarization rotation of the light signals corresponding to the left eye and right eye original images, and provides a stable polarization state basis for the directional separation of the polarization response grating.

[0061] In addition, if the light signals corresponding to the left eye original image and the right eye original image output by the display screen are both left circularly polarized light, the polarized component can be configured with a half wave plate, and the half wave plate covers the second pixel region. Since the half wave plate has the function of changing the rotation direction of circularly polarized light, it can convert the left circularly polarized light output by the second pixel region into right circularly polarized light. The principle is that when left circularly polarized light is incident on the half wave plate, the two orthogonal components (o light and e light) of the electric field will produce a phase difference of π, resulting in a reversal of the rotation direction of the combined electric field, thereby outputting right circularly polarized light. Conversely, if the incident is right circularly polarized light, i.e., the light signals corresponding to the left eye original image and the right eye original image are both right circularly polarized light, they will be converted into left circularly polarized light after passing through the half wave plate. The half wave plate can cover the first pixel region, which can convert the right circularly polarized light output by the first pixel region into left circularly polarized light.

[0062] Since the display screen outputs the light signals corresponding to the left-eye original image and the right-eye original image respectively at the pixel level, the half-wave plate can be designed in a pixelated partition layout, such as a half-wave plate unit is arranged only at a position corresponding to the second pixel area, while the first pixel area is kept without a wave plate or uses a transparent substrate to ensure that the left-handed circularly polarized light signal of the left-eye original image can be directly transmitted. Such a design not only ensures the accuracy of the polarization state conversion, but also avoids unnecessary optical element stacking that causes light loss. For example, in the pixel array of the display screen of the AR device, if the first pixel area and the second pixel area are alternately distributed row by row, and assuming that the second pixel area is even-numbered rows of pixels, the half-wave plate can be processed into a strip-shaped structure that is completely aligned with the even-numbered rows of pixels, and is fixed on the light-emitting side of the display screen through a precise bonding process, so that the left-handed circularly polarized light output by the even-numbered rows of pixels is completely converted into right-handed circularly polarized light by the half-wave plate, while the left-handed circularly polarized light output by the odd-numbered rows of pixels is directly transmitted to the subsequent polarization volume holographic grating.

[0063] Therefore, by combining the direct output of circularly polarized light by the display screen and the configuration of the half-wave plate by the polarizing component, it is possible to eliminate the need for an additional linear polarizer, and the structure is relatively simple. Moreover, by utilizing the native characteristics of the circularly polarized light micro-display screen, it is possible to reduce light loss and improve display brightness and efficiency.

[0064] The left-eye original image and the right-eye original image mentioned above can be generated according to the binocular parallax principle: for example, for a certain object in a virtual scene, the left-eye pattern simulates the viewing angle of the left eye observing the object, and the right-eye pattern simulates the viewing angle of the right eye, so as to ensure that the two images have a parallax offset of about 55-70 mm (corresponding to the average interpupillary distance of an adult) in the horizontal direction, and the details such as the near-far relationship and the occlusion relationship of the object also need to match the respective viewing angles, so that the brain can fuse the images received by the left and right eyes into a 3D stereoscopic effect with depth perception.

[0065] The quarter-wave plate and the half-wave plate mentioned above can be realized by liquid crystal material. For a wave plate that needs to be electrically controlled, the structure is: lower substrate, conductive layer (ITO), orientation layer (PI), liquid crystal molecules, orientation layer (PI), conductive layer (ITO), and upper substrate. Controlling the thickness of the liquid crystal layer and the orientation of the orientation layer can realize the characteristics of the half-wave plate or the quarter-wave plate.

[0066] For the wave plate without electric control, the structure is: lower substrate, orientation layer (PI), liquid crystal molecules, orientation layer (PI) and upper substrate. Controlling the thickness of the liquid crystal layer and the orientation mode of the orientation layer can realize the characteristics of half-wave plate or quarter-wave plate. However, at this time, the wave plate needs to be pixel-level partitioned to control the orientation characteristics of each pixel corresponding area in the wave plate, such as controlling the orientation characteristics of the corresponding pixel area in the wave plate to be +45°, and the orientation characteristics of the other pixel area to be -45°, so that the phase delay direction of the wave plate in different areas to the incident light is different, that is, the partition conversion of left-handed and right-handed circularly polarized light is realized, and the specific polarization response of the corresponding pixel area is realized.

[0067] The quarter-wave plate and half-wave plate can be realized by super surface. The dielectric nanocubes are prepared by semiconductor process, and the length, width, height and long axis direction of the nanocube are determined by design to obtain the desired polarization response. The semiconductor process can prepare wave plates with consistent full surface, or wave plates with pixel-level changes. The wave plate with consistent full surface is that the wave plate optical axis direction or phase delay characteristics corresponding to all pixel areas are exactly the same, which is suitable for scenes that need unified polarization control, such as the above-mentioned schemes of electrically or thermally controlled switching of left-handed and right-handed circularly polarized light. The wave plate with pixel-level changes can realize independent regulation of the polarization state of each pixel output by differentiating the design of nanocube parameters in different pixel areas in the semiconductor process (such as adjusting the long axis direction of the nanocube in a specific pixel area to +45° and the long axis direction of the nanocube in the adjacent pixel area to -45°), without additional partitioning and bonding process, which greatly improves the integration and accuracy of the polarization component.

[0068] For the wave plate super surface that needs electric control, a semiconductor material with phase change characteristics can be selected for processing. By electrically or thermally controlling the refractive index, size and other parameters, the conversion of polarization response can be realized.

[0069] Based on the foregoing embodiments, in some other optional embodiments, the internal structure of the polarization component is a polarization conversion structure, which is a structure for changing the polarization state of incident light, such as the combination structure of wave plate (such as half-wave plate or quarter-wave plate), polarizer, phase delay film and other elements. Among them, the polarizer can convert non-polarized light into linearly polarized light in a specific direction, providing a basic polarization state for subsequent phase modulation; the phase delay film introduces a specific phase difference to linearly polarized light in different vibration directions through the birefringence characteristics of the material, thereby realizing the conversion of polarization state.

[0070] Therefore, the polarizing assembly can convert the polarization state of the light signal output by the display screen into a circular polarization state of a specific handedness based on the polarization conversion structure inside it, obtaining left-handed circularly polarized light and right-handed circularly polarized light. For example, when the polarization conversion structure is a wave plate, the way it converts the polarization state of incident light and the implementation principle can refer to the foregoing description.

[0071] When the polarization conversion structure is a phase retardation film, it usually adopts a polymer thin film material with birefringence properties, and the molecular chains are arranged along a specific direction through a precise stretching or orientation process, thereby forming a fixed optical axis direction. When linearly polarized light is incident on the phase retardation film at a preset angle, it will also be decomposed into an e-light component along the optical axis and an o-light component perpendicular to the optical axis, and the product of the thickness of the film and the birefringence determines the phase difference between the two. For example, if the phase retardation film is designed to have a phase difference of π / 2 (i.e., 1 / 4 wavelength retardation), and the optical axis and the polarization direction of the incident light form an angle of 45 degrees, when the incident light is horizontally polarized, the phase difference between the e-light and the o-light will convert the linearly polarized light into circularly polarized light; if the sign of the birefringence is changed by adjusting the stretching degree of the film (such as using a two-way stretching process to reverse the orientation of the molecular chains), the direction of the phase difference can be reversed, thereby converting the linearly polarized light into circularly polarized light of opposite handedness. The advantage of this phase retardation film is that it is thin and flexible, can be attached to the curved display screen of the AR device, and has a lower preparation cost than traditional crystal wave plates, making it suitable for large-scale production.

[0072] The polarization volume holographic grating includes a left-handed response grating and a right-handed response grating. The left-handed response grating only produces a diffraction response to left-handed circularly polarized light, and the right-handed response grating only produces a diffraction response to right-handed circularly polarized light. When the left-handed circularly polarized light output by the polarizing assembly is incident on the polarization volume holographic grating, the left-handed response grating will diffract the left-handed circularly polarized light to the left eye field of view direction of the human eye according to the Bragg diffraction principle; and when the right-handed circularly polarized light is incident, the right-handed response grating will diffract it to the right eye field of view direction. Therefore, the left-handed response grating can be used to diffract the left-handed circularly polarized light along the vector direction of the left-handed response grating into the light transmission medium corresponding to the left eye of the human, and the right-handed response grating is used to diffract the right-handed circularly polarized light along the vector direction of the right-handed response grating into the light transmission medium corresponding to the right eye of the human.

[0073] For example, the polarization volume holographic grating can be a liquid crystal polarization volume holographic grating. The liquid crystal polarization volume holographic grating is a grating with polarization response. For a liquid crystal polarization volume holographic grating with one chirality, it only diffracts left-handed circularly polarized light and completely transmits right-handed circularly polarized light, while for a liquid crystal polarization volume holographic grating with another chirality, it only diffracts right-handed circularly polarized light and completely transmits left-handed circularly polarized light. By using the polarization response characteristics of the liquid crystal polarization volume holographic grating, two kinds of grating with different chirality responses can be arranged in the coupling-in region of the optical waveguide. In combination with the specific implementation of the optical engine, the corresponding image will be naturally propagated into the waveguide sheet corresponding to the eye according to the projection of the optical engine.

[0074] As shown in Figure 3 The microstructure of two liquid crystal polarization volume holographic gratings with different chirality and different polarization response is shown, wherein the upper graph corresponds to the polarization volume holographic grating with left-handed response, and the lower graph corresponds to the polarization volume holographic grating with right-handed response. In the figure, Λx, Λy, and Λb represent the period length of the grating structure from each viewing angle of the x-axis direction, the y-axis direction, and the shortest distance direction, respectively, wherein the shortest distance refers to the distance between two adjacent dashed lines in the figure, that is, the distance between adjacent lines where the liquid crystal molecules with the same direction are located, such as the solid dots in the figure, and the distance between the lines of the solid dots (the inclined dashed line in the figure) is Λb.

[0075] The basic unit of the liquid crystal polarization volume holographic grating can be a rod-shaped liquid crystal molecule. The dielectric constant of the long axis (optical axis) direction of the liquid crystal molecule is different from the dielectric constant perpendicular to the optical axis direction, so it has anisotropic optical properties, which can be described by a dielectric constant tensor. The liquid crystal polarization volume holographic grating is a stable structure produced by arranging such liquid crystal molecules in space according to a certain rule (such as periodicity).

[0076] As shown in Figure 3 Each position corresponds to a liquid crystal molecule, but the long axis direction of the liquid crystal molecule at different positions is different. As seen along the x-axis, it can be seen that the rotation angle of the long axis of the liquid crystal molecule at different x-axis positions is different, and when a fixed distance is passed, the liquid crystal molecule is rotated to the same angle, so from a certain viewing angle, part of the liquid crystal molecules appear as different length shuttle-shaped strips, and part of the liquid crystal molecules appear as solid points. Similarly, the same rule can be seen along the y-axis direction.

[0077] Therefore, it can be considered that the liquid crystal polarization volume holographic grating is a three-dimensional periodic structure, and the plane composed of liquid crystal molecules with the same rotation angle is Figure 3 The dashed line connecting line constitutes the "state" surface of the liquid crystal molecule, and the distance between the "state" surfaces is the grating period of the three-dimensional grating.

[0078] In practical applications, the liquid crystal molecules of the left-handed response grating are arranged in a helical shape along the grating period direction, and the helical direction is counterclockwise. When left-handed circularly polarized light is incident, the electric field vibration direction matches the helical structure of the liquid crystal molecules, and the periodic refractive index modulation inside the grating is excited, thereby producing diffraction. The electric field vibration direction of right-handed circularly polarized light does not match the helical structure, and cannot excite effective modulation, so most of the light is directly transmitted. The helical direction of the liquid crystal molecules of the right-handed response grating is clockwise, which matches the electric field vibration direction of the right-handed circularly polarized light, and only the right-handed circularly polarized light produces diffraction, and the left-handed circularly polarized light is transmitted. The difference in microstructure enables the two gratings to accurately distinguish circularly polarized light of different handedness, and realize directional diffraction separation of left and right eye images.

[0079] The preparation process of the polarization volume holographic grating is an exemplary embodiment as follows: 1. Clean the high-transmittance glass substrate; 2. Prepare a liquid crystal light-controlled orientation layer solution and prepare a light-controlled orientation layer film on the glass substrate; 3. Polarization holographic exposure: build an exposure light path, orient the orientation film, and the exposure energy needs to be greater than 5 J / cm3; 4. Prepare a liquid crystal polymer solution mixed with a chiral agent and an initiator on the liquid crystal light orientation layer film to prepare a liquid crystal polymer film; 5. Nitrogen ultraviolet environment curing to obtain a polarization volume holographic grating film.

[0080] Specifically, in step 1, the high-transmittance glass substrate can be ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water in sequence to completely remove oil stains, dust, and organic residues on the substrate surface; after cleaning, the substrate is dried in a nitrogen atmosphere to avoid water stains affecting the adhesion of subsequent film layers.

[0081] The liquid crystal light-controlled orientation layer solution in step 2 is usually prepared by using polyvinyl alcohol or polyimide as the solute and N-methyl pyrrolidone as the solvent, stirring uniformly, and then filtering through an organic filter membrane; when preparing the orientation layer film, a spin coating process is used, and the spin coating speed and time can be set accordingly according to actual conditions, and then the substrate can be placed on a hot plate for pre-baking, and then transferred to an oven for baking to form an orientation layer film with uniform thickness.

[0082] The polarization holographic exposure light path in step 3 can include a laser, a beam splitter, a mirror, a beam expander, and a polarizer, etc. The laser is divided into two beams of coherent light with orthogonal polarization directions, and is incident on the orientation layer surface at a symmetric angle (usually ±15°-±30°). The exposure energy can be controlled at 5-8 J / cm², and the exposure time is adjusted according to the laser power to ensure that a stable periodic orientation pattern is formed on the surface of the orientation layer.

[0083] The liquid crystal polymer solution of step 4 is mainly composed of a nematic liquid crystal, and 1-3% of chiral agent and 0.5-1% of photoinitiator can be added. After stirring and dissolving, the solution is filtered through a filter membrane. When preparing the liquid crystal polymer film on the alignment layer, a doctor blade coating process is adopted, and the coating thickness and speed can be set according to the actual situation to ensure that the film layer is free of bubbles and scratches.

[0084] The nitrogen and ultraviolet environment curing of step 5 can place the substrate coated with the liquid crystal polymer film in a sealed cavity with a certain nitrogen concentration, and irradiate it with an ultraviolet lamp of a certain wavelength. The curing energy and time can be set according to the actual situation. During the curing process, the substrate temperature should be maintained within an appropriate range to avoid temperature fluctuations that can cause the liquid crystal molecules to arrange in disorder. Finally, a polarization volume holographic grating film with a stable periodic structure is formed.

[0085] In some optional embodiments, the polarization volume holographic grating can be prepared by combining a left-handed response grating and a right-handed response grating through a glue layer to obtain the polarization volume holographic grating. For example Figure 4 The structure of the polarization volume holographic grating obtained based on one of its preparation methods is shown exemplarily. Two gratings can be prepared according to the above grating preparation steps, one being a left-handed response grating and the other being a right-handed response grating. Then, as shown in Figure 4 the left-handed response polarization volume holographic grating and the right-handed response polarization volume holographic grating are combined together through a glue layer, and the grating vector directions of the two gratings need to maintain a specific angle (such as 90° or other preset angles) to ensure that the diffraction paths of the left and right eye images do not interfere with each other and are directed to the left and right eye fields of the human eye, respectively. Among them, LP represents linearly polarized light (Linearly Polarized), RCP represents right circularly polarized light (Right -Circularly Polarized), and LCP represents left circularly polarized light (Left -Circularly Polarized).

[0086] For the diffraction characteristics of this structure, when left circularly polarized light is incident, the incident light will be diffracted and propagated along the direction of the left-handed response grating vector; when right circularly polarized light is incident, the incident light will be diffracted and propagated along the direction of the right-handed response grating vector. The grating vector direction refers to the normal direction between adjacent equal phase planes in the periodic structure of the grating, which is determined by the periodic arrangement rule of the grating. For the polarization volume holographic grating, the grating vector direction is directly related to the propagation direction of the diffracted light. For example, the grating vector direction of the left-handed response grating is determined by the periodicity of the helical arrangement of the liquid crystal molecules. When left circularly polarized light is incident, the diffracted light will propagate along this grating vector direction. Similarly, the grating vector direction of the right-handed response grating is determined by the periodicity of the clockwise helical arrangement of the liquid crystal molecules, and the diffraction direction of the right circularly polarized light is along this grating vector direction.

[0087] The advantage of this way is that the diffraction angles of the right-handed and left-handed response gratings can be independently adjusted, which does not need to be limited by the parameter coupling of a single grating structure, and allows optical engineers to accurately set the position of the coupling-out area (such as the upper edge or side edge of the optical waveguide) and the diffraction angle (such as an exit angle of 30° or 45°) according to the simulation results of the optical system of the AR device, to ensure that the imaging positions of the left and right eye images on the human eye retina are accurately matched, to avoid the problems of ghosting or field deviation, and to improve the immersion and visual comfort of AR display.

[0088] In some alternative embodiments, the preparation method of the polarization volume holographic grating can also be to prepare a grating, and in the above preparation steps, 4 and 5 are repeated, the left-handed response liquid crystal solution is first spin-coated and then solidified, and then the right-handed response liquid crystal solution is spin-coated and then solidified, so that a grating with two responses can be directly obtained.

[0089] Specifically, the preparation process is as follows: first, the basic preparation of steps 1 to 3 is completed: the high-transmittance glass substrate is cleaned, the liquid crystal photo-alignment layer solution is prepared and the alignment layer film is prepared on the substrate, and the stable periodic orientation pattern is formed on the surface of the alignment layer by polarization holographic exposure. Subsequently, the preparation of the multilayer liquid crystal polymer film is carried out: in the first step, the left-handed response liquid crystal polymer solution is prepared according to the formula of step 4, the solution is uniformly coated on the exposed alignment layer by using the doctor blade coating process, and the coating thickness and speed are controlled to ensure that the film layer is free of bubbles and scratches; then the solidification operation of step 5 is performed, the substrate coated with the left-handed response liquid crystal polymer film is placed in a sealed cavity with a certain nitrogen concentration, and irradiated with a UV lamp, and after setting the solidification energy and solidification time, solidification is carried out, and after solidification is completed, a single layer of left-handed response grating film is formed.

[0090] Without changing the substrate, the superposition preparation of the right-handed response grating film is directly carried out: the right-handed response liquid crystal polymer solution is prepared again, the same doctor blade coating process is used to coat the solution on the surface of the solidified left-handed response grating film, and then the nitrogen-UV solidification step is repeated, and after solidification is completed, a single layer of right-handed response grating film is formed.

[0091] Therefore, by using the process of "one orientation and two coating and solidification", a double-layer polarization volume holographic grating film integrating left-handed and right-handed response functions is directly obtained on the same glass substrate, the periodic structures of the two layers of gratings are matched through the unified regulation of the bottom alignment layer, the grating vector direction can be preset to a certain angle difference (such as 90°) by adjusting the doctor blade coating direction or the substrate angle during the two coating processes, no additional adhesive layer bonding step is needed, the preparation process is greatly simplified, and the overall transmittance and diffraction efficiency of the grating are improved.

[0092] The above-mentioned polarization volume holographic grating is configured in the coupling-in region of the optical waveguide to directionally diffract and separate different circularly polarized light output by the optical engine. In the coupling-out region of the optical waveguide, the coupling-in region of the optical waveguide has completed the spatial separation and directional transmission of the left-eye and right-eye image light through the polarization response characteristics. Therefore, in the preparation of the grating in the coupling-out region, the single eyeglass region does not need to have the response capability to the left-handed and right-handed circularly polarized light at the same time. For example, for the left-handed circularly polarized light transmitted by the left-eye waveguide, the coupling-out grating of the corresponding eyeglass only needs to be designed to have a diffraction response to the left-handed circularly polarized light; for the right-handed circularly polarized light transmitted by the right-eye waveguide, the coupling-out grating of the corresponding eyeglass only needs to be designed to have a diffraction response to the right-handed circularly polarized light.

[0093] The selection of the grating in the coupling-out region has many ways. The grating with polarization response can be selected, or the grating without polarization response can be selected. The diffraction grating can be selected, or the geometric array can be selected, etc.

[0094] Therefore, the configuration of the grating in the coupling-out region simplifies the design and preparation process of the coupling-out grating, and ensures the stable transmission of the left-eye and right-eye image light in the respective waveguide paths and the final coupling-out to the corresponding eye, avoids the interference of different circularly polarized light in the coupling-out stage, and guarantees the clarity and stability of 3D display.

[0095] For example, Figure 5 An exemplary structure and technical implementation of an AR device are shown. As shown in the figure, when the unpolarized incident light enters the optical engine, it can be converted into linearly polarized light by a linear polarizer (not shown in the figure). The linearly polarized light is then regulated by a polarizing assembly (not shown in the figure) into left-handed circularly polarized light LCP and right-handed circularly polarized light RCP. The LCP is diffracted to the left-eye waveguide path by the LCP response coupling-in element (i.e., the above-mentioned left-handed response grating), and the RCP is diffracted to the right-eye waveguide path by the RCP response coupling-in element (i.e., the above-mentioned right-handed response grating).

[0096] During the transmission in the optical waveguide, due to the total reflection effect of the waveguide, the LCP and the RCP propagate in the respective waveguide layer along the preset direction until reaching the coupling-out area. The grating of the coupling-out area is designed as an LCP response coupling-out element for the LCP of the left-eye waveguide, which diffracts the LCP to the left-eye field of view of the human eye along the grating vector direction; and is designed as an RCP response coupling-out element for the RCP of the right-eye waveguide, which diffracts the RCP to the right-eye field of view of the human eye. After the human eye receives the respective image light of the left and right eyes, the brain will automatically fuse the two images with parallax into a three-dimensional image, thereby realizing an immersive AR display effect. The coupling-in and coupling-out scheme based on the polarization volume holographic grating not only greatly reduces the volume and weight of the AR device, but also effectively avoids the crosstalk problem through the polarization selection characteristic, improves the display contrast and color restoration, and brings the user a clearer and more comfortable 3D visual experience.

[0097] Based on the foregoing structure of the AR device and its technical implementation, a display control method executed by the AR device is further described below. Please refer to Figure 6 The display control method in the embodiment of the application includes the following steps: 601, controlling the display screen to output a light signal corresponding to an original image, so that the polarizing component regulates the light signal into a plurality of polarized light signals with different handedness, and projects the polarized light signals into the polarization volume holographic grating in the coupling-in area of the light transmission medium through the projection lens; 602, diffracting the polarized light signal with the handedness matching the handedness of the spiral structure to the light transmission medium based on the polarization volume holographic grating, so that the plurality of polarized light signals with different handedness are projected to the left and right eyes of the human to display the left and right eye parallax images of the original image; The method of the embodiment can be applied to the AR device described above, which includes an optical machine and a polarization volume holographic grating. The optical machine includes a display screen, a polarizing component, and a projection lens. The polarization volume holographic grating is arranged in the coupling-in area of the light transmission medium of the AR device, and the internal structure of the polarization volume holographic grating is a spiral structure with a specific handedness.

[0098] The specific implementation and technical principles of each step of the method of the embodiment can be referred to the corresponding description above, which will not be described here.

[0099] In the embodiment, the AR device only needs one optical engine to realize binocular parallax 3D display, without using double optical engines or complex optical path design. The optical engine adjusts and controls the left and right eye original images into left-handed and right-handed circularly polarized light through the polarizing component, and then projects them to the polarization volume holographic grating through the projection lens. The polarization volume holographic grating uses the handedness selectivity of its spiral structure to diffract and couple the polarized light with matching handedness into the light transmission medium. The polarized light with different handedness is transmitted along the independent path in the light transmission medium to the left and right eye imaging areas, and finally forms a 3D image with parallax. This single optical engine combined with the polarization volume holographic grating scheme fundamentally reduces the number of optical engines, greatly reduces the volume, weight and power consumption of the AR device, and avoids the optical path complexity and mass production problems caused by additional optical elements. Under the premise of ensuring 3D display effect, the device is light and thin and has high performance price ratio, which is more in line with the portability and practicality requirements of the market for AR devices.

[0100] The embodiments of the application further provide a computer storage medium, wherein one embodiment includes: the computer storage medium stores instructions, and the instructions are executed on an AR device to enable the AR device to perform the operations of the AR device in the above-described embodiments. Figure 6 The embodiments of the application further provide a computer storage medium, wherein one embodiment includes: the computer storage medium stores instructions, and the instructions are executed on an AR device to enable the AR device to perform the operations of the AR device in the above-described embodiments.

[0101] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0102] In the several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections between the units can be indirect couplings or communication connections through some interfaces, devices or units, and can be electrical, mechanical or other forms.

[0103] The units described as separate components can or can not be physically separate, and the components displayed as units can or can not be physical units, i.e. can be located in one place, or can be distributed on a plurality of network units. According to actual needs, part or all of the units can be selected to achieve the purpose of the embodiment scheme.

[0104] In addition, each function unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software function unit.

[0105] When the integrated unit is realized in the form of a software function unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the present application, essentially or in the form of a contribution to the prior art, or all or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, read-only memory), a random access memory (RAM, random access memory), a magnetic disk or an optical disk, and various media that can store program codes.

Claims

1. An AR device, characterized by, The AR device comprises an optical engine and a polarization volume holographic grating, the optical engine comprises a display screen, a polarizing component and a projection lens; The polarization volume holographic grating is arranged in a coupling-in region of an optical transmission medium of the AR device, and an internal structure of the polarization volume holographic grating is a helical structure with a specific handedness; The display screen is configured to output light signals corresponding to original images, the polarizing component is configured to regulate the light signals into polarized light signals with different handednesses, and the polarized light signals are projected to the polarization volume holographic grating in the coupling-in region of the optical transmission medium through the projection lens; The polarization volume holographic grating is configured to diffract the polarized light signals with the same handedness as the helical structure to the optical transmission medium, so that the polarized light signals with different handednesses are projected to the left and right eyes of a person to display left and right eye parallax images of the original images.

2. The AR device of claim 1, wherein, The display screen is specifically configured to cyclically and alternately output light signals corresponding to left eye original images for a left eye of a person to watch and light signals corresponding to right eye original images for a right eye of a person to watch; The polarizing component is specifically configured to, while the display screen outputs the light signals corresponding to the left eye original images, regulate the light signals corresponding to the left eye original images into left circularly polarized light under the control of a first signal; and while the display screen outputs the light signals corresponding to the right eye original images, regulate the light signals corresponding to the right eye original images into right circularly polarized light under the control of a second signal.

3. The AR device of claim 2, wherein, The first signal and the second signal comprise first and second electric control signals; The first electric control signal is configured to control a first preset included angle between an optical axis direction of a wave plate in the polarizing component and a polarization direction of incident light, so that the light signals corresponding to the left eye original images are converted into left circularly polarized light based on the first preset included angle; The second electric control signal is configured to control a second preset included angle between an optical axis direction of a wave plate in the polarizing component and a polarization direction of incident light, so that the light signals corresponding to the right eye original images are converted into right circularly polarized light based on the second preset included angle.

4. The AR device of claim 1, wherein, The display screen is specifically configured to output light signals corresponding to left eye original images for a left eye of a person to watch in a first pixel region of the display screen, and output light signals corresponding to right eye original images for a right eye of a person to watch in a second pixel region of the display screen; and pixels in the first pixel region and pixels in the second pixel region are alternately distributed on the display screen. The polarizing component is specifically configured to regulate the light signals corresponding to the left eye original images into left circularly polarized light, and regulate the light signals corresponding to the right eye original images into right circularly polarized light.

5. The AR device of claim 4, wherein, The polarizing component comprises first and second wave plates; The polarizing component is specifically configured to convert the light signals corresponding to the left eye original images into left circularly polarized light based on a first preset included angle between an optical axis direction of the first wave plate and a linear polarization direction, and convert the light signals corresponding to the right eye original images into right circularly polarized light based on a second preset included angle between an optical axis direction of the second wave plate and a linear polarization direction. If the light signal output by the display screen is in a non-polarization state, the light signal is converted into a linear polarization state by a linear polarizer and then output to the first wave plate and the second wave plate; if the light signal output by the display screen is in a linear polarization state, the light signal is directly output to the first wave plate and the second wave plate.

6. The AR device of claim 4, wherein, The polarizing assembly comprises a half wave plate. If the light signal corresponding to each of the left-eye original image and the right-eye original image is left-handed circularly polarized light, the half wave plate is covered on the second pixel region to convert the left-handed circularly polarized light output by the second pixel region into right-handed circularly polarized light. If the light signal corresponding to each of the left-eye original image and the right-eye original image is right-handed circularly polarized light, the half wave plate is covered on the first pixel region to convert the right-handed circularly polarized light output by the first pixel region into left-handed circularly polarized light.

7. The AR device of claim 1, wherein, The internal structure of the polarizing assembly is a polarization conversion structure. The polarizing assembly is specifically used to convert the polarization state of the light signal output by the display screen into a circular polarization state with a specific handedness based on the polarization conversion structure in the internal structure, to obtain left-handed circularly polarized light and right-handed circularly polarized light. The polarization volume holographic grating comprises a left-handed response grating and a right-handed response grating. The left-handed response grating is used to diffract the left-handed circularly polarized light along a left-handed response grating vector direction into the light transmission medium corresponding to the left eye of a person, and the right-handed response grating is used to diffract the right-handed circularly polarized light along a right-handed response grating vector direction into the light transmission medium corresponding to the right eye of a person.

8. The AR device of claim 1, wherein, The polarization volume holographic grating is obtained by combining the left-handed response grating and the right-handed response grating through an adhesive layer. Alternatively, The polarization volume holographic grating is obtained by sequentially spin-coating a left-handed response liquid crystal solution and a right-handed response liquid crystal solution on a substrate which has been coated with a light-controlled orientation layer film and exposed and oriented on the orientation layer film, and then solidifying them respectively. The left-handed response grating is obtained by solidifying the left-handed response liquid crystal solution after spin-coating the left-handed response liquid crystal solution on the substrate, and the right-handed response grating is obtained by solidifying the right-handed response liquid crystal solution after spin-coating the right-handed response liquid crystal solution on the substrate.

9. A display control method characterized by comprising: The method is applied to the AR device of any one of claims 1 to 8, the AR device comprising an optical machine and a polarization volume holographic grating, the optical machine comprising a display screen, a polarizing assembly, and a projection lens; the polarization volume holographic grating is arranged in a coupling-in region of a light transmission medium of the AR device, and the internal structure of the polarization volume holographic grating is a helical structure with a specific handedness. The method comprises: controlling the display screen to output a light signal corresponding to an original image, so that the polarizing assembly regulates the light signal into a plurality of polarization light signals with different handedness, and the projection lens projects the polarization light signals into the polarization volume holographic grating in the coupling-in region of the light transmission medium; based on the polarization volume holographic grating, diffracting the polarization light signal with a handedness matching the handedness of the helical structure into the light transmission medium, so that the plurality of polarization light signals with different handedness are projected into the left and right eyes of a person to display left and right eye parallax images of the original image.

10. A computer storage medium, characterized in that The computer storage medium stores instructions which, when executed on the AR device, cause the AR device to perform the method of claim 9.

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