A depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens

Abstract

The present invention discloses a depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens: the display method comprises: light emitted by an image source is collimated by a collimator, an in-coupling grating couples the collimated light into an optical waveguide plate; light propagates in the optical waveguide plate by total reflection, and after hitting an out-coupling grating, it is diffracted and coupled out of the optical waveguide plate as out-coupling light; the out-coupling light enters the human eye after passing through a zoom moiré lens; the ambient light enters the human eye after passing through a compensating moiré lens and a zoom moiré lens in sequence; wherein, by controlling the rotation of a component PBOE close to the human eye in the zoom moiré lens and a component PBOE far from the human eye in the compensating moiré lens, the focal lengths of the two moiré lenses are synchronously adjusted, so that the image propagated by the waveguide is imaged at a desired depth, while the real environment seen by the human eye is not affected. This method solves the problem that a traditional waveguide display system can only image a virtual image at infinity.

Description

Technical Field

[0001] The present invention relates to the technical field of near-eye waveguide display, and in particular to a depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens. Background Art

[0002] In recent years, augmented reality (AR) technology has developed rapidly and has huge application potential in various fields such as medicine, education, and military. By superimposing computer-generated virtual images onto real scenes, AR is expected to completely change the user's interactive experience and become the next generation of mainstream display device.

[0003] Recently, patterned liquid crystal optical elements are increasingly used in the AR field. Using photo-alignment technology, we can transfer any pattern recorded on the photo-alignment layer to the liquid crystal layer, thereby obtaining a liquid crystal planar element with the designed phase modulation function. By using nematic liquid crystal and cholesteric liquid crystal, transmissive and reflective elements can be prepared respectively. These optical elements are easy to prepare, thin and light, and are very suitable for application in AR systems. At the same time, due to the ordinary light refractive index n of the liquid crystal material, o and the extraordinary refractive index n e The difference is large, resulting in the angular response range and wavelength response range of the liquid crystal device being better than those of the traditional holographic device. In addition, the patterned liquid crystal element has a unique polarization response characteristic, which provides a new design dimension for the design of the optical system. For example, the Chinese patent with the publication number CN112147786A discloses an augmented reality display system, including a waveguide display system and a myopia adjustment optical element; the waveguide display system includes a display image source and a waveguide substrate, and a waveguide internal reflection surface and a waveguide reflection output surface arranged in the waveguide substrate; the myopia adjustment optical element has a first side surface and a second side surface opposite to each other, the first side surface is used to face the human eye, and the second side surface is completely attached to the outer surface of the waveguide substrate; the waveguide substrate allows the light beam from the display image source to propagate in the waveguide in the form of total reflection and be transmitted to the waveguide internal reflection surface, the waveguide internal reflection surface is used to reflect the light beam to the waveguide reflection output surface, and the waveguide reflection output surface is used to pass the light beam through the myopia adjustment optical element and reflect it to the human eye; the myopia adjustment optical element can be a liquid crystal lens. For example, a Chinese patent with publication number CN114089531A discloses a binocular waveguide display method based on a reflective polarization multiplexing liquid crystal lens. The method is based on a waveguide display device, including an optical waveguide plate, on the same side of which an in-coupling liquid crystal lens, a right-handed out-coupling grating and a left-handed out-coupling grating are provided, and the in-coupling liquid crystal lens is located between the right-handed out-coupling grating and the left-handed out-coupling grating.

[0004] As a widely recognized AR solution, waveguide display has certain potential and advantages in terms of volume, weight, field of view, and exit pupil size. However, in traditional waveguide display technology, collimated light is extracted to the user's eyes through an optical coupler in the output part. In this case, the virtual image is imaged at infinity, and the observer's eyes are forced to focus at infinity through accommodation reaction. When a real object is near the user, the displayed image becomes blurred due to the different accommodation depths of the real object and the virtual image. This problem may affect the user's augmented reality experience and cause visual fatigue due to the mismatch between accommodation and vergence distance, which is called vergence-accommodation conflict (VAC). How to solve this problem is currently a hot research topic in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens. The method and device can solve the problem that a traditional waveguide display system can only image a virtual image at infinity.

[0006] The present invention provides the following technical solutions:

[0007] A depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens, using a depth-adjustable waveguide display device, the depth-adjustable waveguide display device comprising an image source, a collimator, an optical waveguide plate provided with an in-coupling grating and an out-coupling grating on the same side, and liquid crystal moiré lenses respectively located on both sides of the out-coupling region of the optical waveguide plate, the liquid crystal moiré lenses comprising a compensation moiré lens and a zoom moiré lens;

[0008] The depth-adjustable waveguide display method comprises:

[0009] The light emitted by the image source is collimated by the collimator, and the in-coupling grating couples the collimated light into the optical waveguide plate;

[0010] Light propagates in the optical waveguide plate by total reflection, and after hitting the out-coupling grating, it is diffracted and coupled out of the optical waveguide plate as out-coupling light;

[0011] The coupled light passes through the zoom moiré lens and enters the human eye;

[0012] The ambient light enters the human eye after passing through the compensation moiré lens and the zoom moiré lens in sequence;

[0013] Among them, by controlling the rotation of the element PBOE in the zoom moiré lens close to the human eye and the element PBOE in the compensation moiré lens far from the human eye, the focal lengths of the two moiré lenses are synchronously adjusted, so that the image propagated by the waveguide is imaged at the desired depth, while the real environment seen by the human eye is not affected.

[0014] The image source can be various light engines such as OLED, MicroLED, DLP, LCOS, etc.

[0015] The collimator may be various lenses or lens systems, which are used to collimate the light emitted by the image source.

[0016] A circular polarizer is added after the image source to convert the light emitted by the image source into circularly polarized light of the corresponding chirality of the waveguide coupling grating, thereby improving the system efficiency.

[0017] The in-coupling grating and the out-coupling grating on the optical waveguide plate are both liquid crystal polarizer gratings PVG, and the in-coupling grating and the out-coupling grating have the same chirality and are symmetrically arranged on the waveguide plate. If the two gratings are made of cholesteric liquid crystals (taking right-handed liquid crystals as an example) with the same chirality, they can diffract circularly polarized light (right-handed circularly polarized light) of the corresponding hand direction.

[0018] The zoom moiré lens and the compensating moiré lens are both composed of two liquid crystal Pancharatnam-Berry phase optical elements PBOE, and the PBOE has the same phase distribution. That is, four identical PBOEs are grouped in pairs to form the zoom moiré lens and the compensating moiré lens, and the two moiré lenses are symmetrically arranged on both sides of the outcoupling area of ​​the waveguide plate, wherein the PBOE in the zoom moiré lens close to the human eye and the element PBOE in the compensating moiré lens far from the human eye are controlled by a rotation control device and can be synchronously rotated to the same angle.

[0019] The phase distribution of the PBOE satisfies the following condition: by rotating one of the PBOEs in the zoom moiré lens or the compensating moiré lens, the combined phase distribution of the two PBOEs in the zoom moiré lens or the compensating moiré lens for incident circularly polarized light is similar to that of a zoom lens.

[0020] The phase distribution of the PBOE only needs to satisfy the above conditions, for example, it can be:

[0021] The PBOE has a certain rotational circular polarization (such as right-handed circular polarization) (Typical phase distribution of moiré lens sub-element, other similar phase distributions can also be used) phase distribution / phase modulation, due to the characteristics of PBOE, for circular polarization of another direction (such as left-handed circular polarization) has Phase distribution / phase modulation; where (r, θ0) is the polar diameter and polar angle in the polar coordinate system, λ is the operating wavelength, F0 is the reference focal length, and round() is a round-up function.

[0022] When the waveguide coupled light (right-handed circularly polarized light) passes through two such PBOEs (forming a zoom moiré lens) in succession, the first PBOE produces a phase modulation of φ(r,θ0) and reverses the direction of circular polarization, and the second PBOE produces a phase modulation of -φ(r,θ0). Since the circular deflection direction of the PBOE diffracted light is reversed relative to the incident light, when two such PBOEs are combined, when the second PBOE rotates around the center by an angle θ relative to the first PBOE, the total phase modulation of the right-handed circularly polarized light incident on this combined element is This is equivalent to a focal length of A lens in which the adjustable range of θ is from -π to +π.

[0023] According to the rotation angle, the focal length of the zoom moiré lens changes continuously between [-∞, -F0] (only the negative focal length is considered, and the positive focal length lens forms the virtual image behind the human eye, which is meaningless), where F0 is the design reference value. The waveguide coupled light enters the human eye after passing through the zoom moiré lens, so the present invention can adjust the rotation angle of the moiré lens to allow the virtual image to be formed at the required depth.

[0024] The above phase distribution is just a common setting, and the PBOE may also have other phase distributions, such as Or other forms.

[0025] The PBOE in the zoom moiré lens close to the human eye and the PBOE in the compensation moiré lens far from the human eye are controlled by a rotation control device to rotate synchronously at the same angle.

[0026] During the synchronous rotation of the PBOE, for incident circularly polarized light of the same hand direction, the zoom moiré lens and the compensation moiré lens always have focal lengths of the same magnitude and opposite signs.

[0027] In the present invention, the compensation moiré lens is provided to compensate for the influence of the zoom moiré lens on the ambient light. In the process of the rotation control device manipulating the zoom moiré lens and the compensation moiré lens to rotate synchronously, for the incident circularly polarized light of the same rotation direction, the two lenses always have the same focal length and opposite sign. At the same time, since the optical waveguide plate is very thin, the lens group formed by the compensation moiré lens and the zoom moiré lens has no optical focal length when the distance between the two is ignored, and will not affect the ambient light (the ambient light can be regarded as the superposition of left-handed circularly polarized light and right-handed circularly polarized light). In addition, since the outcoupling grating is a liquid crystal polarizer grating (reflective element), it will not affect the transmitted ambient light and the ambient transmittance is relatively high. Based on the above analysis, the real environment seen by the human eye will not change in the present invention.

[0028] PVG is prepared by using cholesteric liquid crystal based on photo-alignment technology, while PBOE is prepared by using nematic liquid crystal based on photo-alignment technology. Specifically:

[0029] The method for preparing the liquid crystal polarizer grating on the waveguide plate comprises: preparing a light orientation layer by spin coating on the waveguide plate; performing in-coupling grating exposure and out-coupling grating exposure; spin coating a reactive liquid crystal solution containing a chiral agent and a photoinitiator; ultraviolet curing the liquid crystal layer; the spin coating and curing of the liquid crystal layer can be repeated multiple times to increase the thickness of the liquid crystal layer and improve the diffraction efficiency.

[0030] The preparation method of the PBOE comprises the following steps: preparing a photo-alignment layer by spin coating on a substrate; performing exposure to record a desired phase distribution; spin coating a reactive liquid crystal solution containing a photoinitiator; UV curing the liquid crystal layer; and repeating the spin coating and curing of the liquid crystal layer so that the thickness of the liquid crystal layer meets the half-wave condition to obtain the maximum element efficiency.

[0031] The depth-adjustable waveguide display method provided by the present invention utilizes a rotating zoom liquid crystal lens (Moiré lens) to continuously and widely adjust the focal position of the waveguide outcoupled light, so that the image propagated by the waveguide can be imaged at a desired depth, which solves the problems that the virtual image can only be imaged at infinity in traditional waveguide displays and the imaging blur and visual fatigue it brings to the observer. At the same time, in the present invention, focusing is performed by rotation, rather than by changing the axial distance of the components in the traditional zoom system, so the system is thinner and more compact. And by compensating for the use of the Moiré lens, the method provided by the present invention will not affect the user's observation of the real scene, which ensures a good AR display effect.

[0032] The method provided by the present invention utilizes the characteristics of liquid crystal PBOE that it produces opposite phase modulation for different circularly polarized lights and reverses the rotation direction of the incident light, uses two identical PBOEs to form a moiré lens, and uses a liquid crystal polarizer grating as a coupler in a waveguide, and utilizes its polarization selectivity to meet the circularly polarized light incident requirements of the moiré lens. PBOE and liquid crystal polarizer grating have similar and simple preparation processes, which makes the implementation of the method provided by the present invention more convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall system structure of a depth-adjustable waveguide display device provided by the present invention;

[0034] Figure 2 This is a schematic diagram of waveguide imaging when the moiré lens is focused to different focal lengths;

[0035] Figure 3 is a schematic diagram of the structure of a liquid crystal polarizer grating;

[0036] Figure 4is a schematic diagram of the structure of a liquid crystal Pancharatnam-Berry phase optical element;

[0037] Figure 5 It is the exposure light path of the liquid crystal polarizer grating;

[0038] Figure 6 It is the exposure optical path of the liquid crystal Pancharatnam-Berry phase optical element;

[0039] in, Figure 1 and 2 In-PVG and Out-PVG represent in-coupled liquid crystal polarizer grating and out-coupled liquid crystal polarizer grating, respectively; PBOE represents liquid crystal Pancharatnam-Berry phase optical element; and T-PBOE represents rotatable PBOE. Figure 3 Where LCP and RCP represent left-handed circular polarization and right-handed circular polarization respectively, Λ x ,Λ y ,Λ B represent the transverse period, longitudinal period and Bragg period of PVG respectively, and α represents the grating inclination angle; Figure 4 The d in represents the thickness of the liquid crystal layer of PBOE; Figure 5 In the figure, P is a linear polarizer, QWP is a quarter wave plate, BS is a beam splitter, M1 and M2 are reflectors, and S is an exposure sample substrate; Figure 6 Here, PBS is a polarization beam splitter and SLM is a spatial light modulator. DETAILED DESCRIPTION

[0040] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0041] like Figure 1As shown, it is a schematic diagram of the overall system structure of a depth-adjustable waveguide display device provided by the present invention, and the structure includes an image source 1, a collimator 2, an optical waveguide plate 3, an in-coupling PVG 4, an out-coupling PVG 5, a zoom moiré lens 6, a compensating moiré lens 7 and a rotation controller 8 (also referred to as a rotation control device). The image source 1 is placed on the focal plane of the collimator 2, so the collimator 2 converts the light emitted by the image source 1 into parallel light. The in-coupling PVG 4 and the out-coupling PVG 5 respond to circularly polarized light of the same rotation direction (assumed to be right-handed circularly polarized light in the embodiment), and are symmetrically arranged on the same side of the optical waveguide plate 3. A right-handed circular polarizer can be added after the image source 1 to improve the overall efficiency of the system. The right-handed circularly polarized light is diffracted by the in-coupling PVG 4. The propagation angle of the diffracted light is greater than the total internal reflection angle of the optical waveguide plate 3. Therefore, it is coupled into the optical waveguide plate 3 and propagates continuously by total reflection until it encounters the out-coupling PVG 5 and is diffracted again. The total reflection condition is broken and the light is coupled out of the optical waveguide plate 3. The light that is not diffracted by the out-coupling PVG 5 continues to propagate in the optical waveguide plate 3 until it encounters the out-coupling PVG 5 next time. This process is called the exit pupil expansion of the waveguide. The two moiré lenses (zoom moiré lens 6 and compensation moiré lens 7) in the system are both composed of two PBOEs, and each of them has a PBOE connected to the rotary controller 8. The coupled-out light enters the human eye after passing through the zoom moiré lens 6. The zoom moiré lens 6 can be continuously focused by the manipulation of the rotary controller 8, so the image propagated by the waveguide can be imaged at a certain depth position at infinity or near. The ambient light enters the human eye after passing through the compensating moiré lens 7 and the zoom moiré lens 6. The compensating moiré lens 7 and the zoom moiré lens 6 are symmetrically arranged on both sides of the optical waveguide plate 3 and are controlled by the rotation controller 8 to rotate synchronously at the same angle. They always have focal lengths of the same size and opposite signs for the ambient light, so the ambient light entering the human eye is not affected.

[0042] like Figure 2 The figure shows a schematic diagram of waveguide imaging when the moiré lens is focused to different focal lengths, which shows the imaging results at two focal lengths, corresponding to the angles of θ1 and θ2 controlled by the rotation controller 8 to rotate the T-PBOE. At this time, the zoom moiré lens 6 has focal lengths of -F1 and -F2 for right-handed circularly polarized light, and -F1<-F2<0. Therefore, after the waveguide outcoupled light passes through the zoom moiré lens 6, the virtual image when rotating by θ1 is imaged at a depth position farther from the human eye, while the virtual image when rotating by θ2 is imaged at a depth position closer to the human eye. This embodiment proves the feasibility of the depth-adjustable waveguide display method proposed in the present invention.

[0043] like Figure 3The figure shows the structure of the liquid crystal polarizer grating. PVG is a Bragg grating with a two-dimensional periodic structure. Due to the trend of the lowest volume free energy, the cholesteric liquid crystal in the PVG structure tends to form an inclined spiral structure. The lateral period Λx is determined by the orientation of the light orientation layer. The Bragg period Λ B Equal to half of the cholesteric phase liquid crystal pitch, the liquid crystal pitch (p) is determined by the helical twisting force constant (HTP) and doping concentration (c) of the chiral dopant in the reactive liquid crystal: p = (HTP·c) -1 , the grating inclination angle is α=±arcsin(Λ B / Λ x ), where the positive and negative signs depend on the handedness of the cholesteric liquid crystal. The Bragg condition of PVG for normal incident light is expressed as:

[0044] 2n eff Λ B cosα=λ B

[0045] where λ B is the Bragg wavelength in vacuum, n eff is the effective refractive index of the liquid crystal. Figure 4 The polarization selectivity of PVG is also demonstrated in that the PVG formed by right-handed cholesteric liquid crystal will only diffract right-handed circularly polarized light, while left-handed circularly polarized light will directly pass through the PVG.

[0046] like Figure 4 The figure shows the structure of the liquid crystal Pancharatnam-Berry phase optical element. PBOE is a transmissive phase modulation element based on the Pancharatnam-Berry phase (geometric phase). It is made of nematic phase liquid crystal. The molecular direction of the nematic phase liquid crystal remains consistent in the longitudinal direction (y direction). The liquid crystal molecules with the same (x, z) coordinates have the same orientation angle. Liquid crystal molecular arrangement in the xz plane Determined by the photo-alignment layer, the device with this arrangement of liquid crystal molecules will produce left-handed and right-handed circularly polarized light respectively. The phase modulation is realized by reversing the circular deflection direction of the incident light (left-handed light becomes right-handed light, and right-handed light becomes left-handed light). The diffraction efficiency of PBOE is related to the thickness of the element. The diffraction efficiency is the highest when △n·d=λ / 2, where △n=n e -n o represents the anisotropy of liquid crystal, n o is the ordinary refractive index, n e is the extraordinary light refractive index, d is the thickness of the liquid crystal layer, and λ is the applied wavelength. In the present invention, λ is set to be consistent with the Bragg wavelength of PVG, and the thickness of the PBOE liquid crystal layer to be prepared is calculated to obtain the maximum diffraction efficiency.

[0047] like Figure 5 As shown, the exposure light path of the liquid crystal polarizer grating, the two exposure beams are orthogonal circularly polarized light of equal light intensity, when the two beams are symmetrically incident on the exposure surface at an angle of 2θ, the interference light field is linearly polarized light with uniform light intensity distribution and linearly changing polarization direction along the x-axis period, and the period is Λ=λ e / 2sinθ, where λ e The exposure wavelength is λ. Placing the substrate with the photo-alignment layer on the exposure plane can record the periodic polarization direction. After spin coating the liquid crystal, the photo-alignment layer orients the liquid crystal, thereby generating the lateral period Λx in the PVG.

[0048] like Figure 6 As shown, the exposure optical path of the liquid crystal Pancharatnam-Berry phase optical element is used to expose the PBOE constituting the moiré lens. In the embodiment, the PBOE generates a right-handed circularly polarized light incident on the incident right-handed circularly polarized light. Phase modulation, so during the exposure process, the two interference lights also need to produce a phase difference distribution of φ(r,θ0) on the exposure plane. Figure 6 The exposure optical path shown in the figure first uses a PBS to split the laser beam. The two beams are expanded separately and then combined by a second PBS. One of the light beams passes through an SLM (spatial light modulator) before combining. The SLM modulates the phase distribution of this light beam, and then a 4f system is used to image the SLM onto the exposure plane. In this way, the phase difference of the interference light on the exposure plane is directly determined by the SLM. After combining, the interference light passes through a quarter-wave plate to convert the two interference light beams into left-handed circularly polarized light and right-handed circularly polarized light, respectively. Therefore, the phase difference distribution generated by the SLM is converted into the polarization direction distribution of linear polarized light after interference, and finally recorded by the optical orientation layer.

[0049] By loading the phase distribution of φ(r,θ0) on the SLM, the present invention can prepare the required PBOE, cascade two such PBOEs, and control the second PBOE to rotate by an angle of θ. The total phase modulation of the right-handed circularly polarized light incident on this combined element is This constitutes the zoom moiré lens (focal length ), the compensation moiré lens is also composed of two identical PBOEs. The first PBOE is controlled to rotate synchronously by an angle θ, and the phase modulation of the right-handed circularly polarized light incident on the compensation moiré lens is: Its focal length is the same as that of the zoom moiré lens, but has the opposite sign.

[0050] Figure 5 and Figure 6What is demonstrated is the interference exposure method. Non-interference exposure methods can also be used to prepare PVG and PBOE, such as the laser direct writing method. The exposure sample is placed on a two-dimensional translation stage, and the sample is exposed point by point by controlling the translation stage. When exposing each position, the required linear polarization direction is generated through polarization control, thereby generating the designed molecular arrangement pattern on the photo-orientation layer.

[0051] In the preparation process of PVG and PBOE, the present invention selects RM257 which has been widely used and has good optical properties as the reactive liquid crystal material. As for the chiral dopant, the present invention selects R5011 (HTP≈108 / μm) which has a large twisting force.

[0052] The specific preparation process of PVG and PBOE is as follows:

[0053] (1) Substrate cleaning;

[0054] (2) Preparation and spin coating of photo-alignment layer solution;

[0055] (3) drying the photo-alignment layer;

[0056] (4) Exposure;

[0057] (5) Preparation of liquid crystal mixture solution (a chiral dopant is added in the preparation of PVG, and a chiral dopant is not added in the preparation of PBOE);

[0058] (6) Spin coating liquid crystal;

[0059] (7) UV curing;

[0060] (8) Repeat steps 6 and 7 until a sufficient liquid crystal layer thickness is formed;

[0061] When preparing an optical waveguide plate with PVG, the optical waveguide plate is directly used as the preparation substrate. During exposure, the in-coupling PVG and the out-coupling PVG are exposed in sequence in different areas. The same exposure optical path is used for the two exposures. However, after the in-coupling exposure is completed, the substrate needs to be rotated 180° for out-coupling exposure to meet the symmetrical setting requirements of the two gratings.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A depth-adjustable waveguide display method based on a rotating zoom liquid crystal lens, characterized in that: A depth-adjustable waveguide display device is used, the depth-adjustable waveguide display device comprises an image source, a collimator, an optical waveguide plate provided with an in-coupling grating and an out-coupling grating on the same side, and liquid crystal moiré lenses respectively located on both sides of the out-coupling region of the optical waveguide plate, the liquid crystal moiré lenses comprising a compensation moiré lens and a zoom moiré lens; A circular polarizer is added after the image source; The in-coupling grating and the out-coupling grating on the optical waveguide plate are both liquid crystal polarizer gratings PVG, the in-coupling grating and the out-coupling grating have the same chirality and are symmetrically arranged on the waveguide plate; The zoom moiré lens and the compensation moiré lens are both composed of two liquid crystal Pancharatnam-Berry phase optical elements PBOE, the PBOE has the same phase distribution, and the two moiré lenses are symmetrically arranged on both sides of the outcoupling area of ​​the waveguide plate; The phase distribution of the PBOE satisfies the following conditions: by rotating one of the PBOEs in the zoom moiré lens or the compensating moiré lens, the combined phase distribution of the two PBOEs in the zoom moiré lens or the compensating moiré lens for incident circularly polarized light is similar to that of a zoom lens; The PBOE in the zoom moiré lens close to the human eye and the PBOE in the compensation moiré lens far from the human eye are controlled by a rotation control device to rotate synchronously at the same angle; During the synchronous rotation of the PBOE, for incident circularly polarized light of the same hand direction, the zoom moiré lens and the compensation moiré lens always have focal lengths of the same magnitude and opposite signs; The depth-adjustable waveguide display method comprises: The light emitted by the image source is collimated by the collimator, and the in-coupling grating couples the collimated light into the optical waveguide plate; Light propagates in the optical waveguide plate by total reflection, and after hitting the out-coupling grating, it is diffracted and coupled out of the optical waveguide plate as out-coupling light; The coupled light passes through the zoom moiré lens and enters the human eye; The ambient light enters the human eye after passing through the compensation moiré lens and the zoom moiré lens in sequence; Among them, by controlling the rotation of the element PBOE in the zoom moiré lens close to the human eye and the element PBOE in the compensation moiré lens far from the human eye, the focal lengths of the two moiré lenses are synchronously adjusted, so that the image propagated by the waveguide is imaged at the desired depth, while the real environment seen by the human eye is not affected.

2. The depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens according to claim 1, characterized in that: The image source is selected from OLED, MicroLED, DLP or LCOS.

3. The depth-adjustable waveguide display method based on a rotary zoom liquid crystal lens according to claim 1, characterized in that: The PBOE has a The phase distribution of circular polarization in the other direction has Phase distribution; where (r, θ0) is the polar diameter and polar angle in the polar coordinate system, λ is the working wavelength, F0 is the reference focal length, and round() is a rounding function.

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