Near-to-eye display system and display method based on retina projection

Abstract

The invention discloses a near-to-eye display system and display method based on retina projection, and belongs to the technical field of display products. The near-to-eye display system comprises an image generation unit, a waveguide device, a second phase element and a secondary polarizer holographic element; the image generation unit is used for generating an imaging light beam with image information; the waveguide device is used for receiving the imaging light beam of the image generation unit and carrying out light path folding on the imaging light beam; the second phase element selectively converts the imaging light beam into first polarized light or second polarized light; the secondary polarization body holographic element is used for receiving the first polarized light or the second polarized light emitted by the second phase element; the second phase element selectively converts the first polarized light or the second polarized light to converge the first polarized light or the second polarized light to different viewpoints through the secondary polarizer holographic element. On the premise that the convergence adjustment conflict problem is solved, the eye movement range is increased, and the image crosstalk and dark space phenomena are avoided.

Description

Technical Field

[0001] The present application relates to the technical field of display products, and in particular to a near-eye display system and display method based on retinal projection. Background Art

[0002] Vergence-accommodation conflict (VAC) is a common problem in augmented reality (AR) and virtual reality (VR) technologies. It refers to the incoordination between vergence (the eyes turn inward or outward to focus on the target) and accommodation (the lens changes shape to focus on objects at different distances) when the human eye observes virtual objects. Under normal circumstances, when people observe an object, vergence and accommodation are carried out simultaneously, but in AR and VR devices, because the screen is flat and there is no actual depth information, this causes the eye's focus accommodation to not match the vergence, resulting in a conflict, causing visual discomfort and dizziness.

[0003] Retinal projection display is based on Maxwell's observation method. Since a thin beam of light enters the human eye, the human eye can see the image clearly within a large depth of field. When the human eye focuses and the binoculars converge to observe natural real objects at different distances, the virtual image can be displayed clearly independent of the lens's focus, thus solving the convergence-accommodation conflict.

[0004] However, in existing retinal projection technology, the convergence point of the thin light beam needs to match the pupil of the human eye, so the range of movement of the human eye is very small. At the same time, the existing pupil expansion solution will have multiple viewpoints at the same time, which may easily lead to image crosstalk or dark areas. Summary of the invention

[0005] In order to increase the eye movement range and avoid image crosstalk and dark area phenomena while solving the convergence-accommodation conflict problem, the present application provides a near-eye display system and display method based on retinal projection.

[0006] The present application provides a near-eye display system based on retinal projection, which adopts the following technical solutions: First aspect A near-eye display system based on retinal projection, comprising: An image generating unit, used for generating an imaging light beam carrying image information; A waveguide device, used for receiving an imaging light beam from the image generating unit and performing optical path folding on the imaging light beam; A second phase element is used to receive the imaging light beam after the optical path is folded, and selectively convert the imaging light beam into a first polarized light or a second polarized light, wherein the polarization states of the first polarized light and the second polarized light are orthogonal; a secondary polarization volume hologram element, used for receiving the first polarized light or the second polarized light emitted by the second phase element, the secondary polarization volume hologram element comprising a third polarization diffraction element and a fourth polarization diffraction element which are stacked, the third polarization diffraction element diffracts the first polarized light and transmits the second polarized light, the fourth polarization diffraction element diffracts the second polarized light and transmits the first polarized light; The second phase element selectively transforms the first polarized light or the second polarized light to converge the first polarized light or the second polarized light to different viewpoints through the secondary polarization volume hologram element.

[0007] By adopting the above technical solution, the present invention uses a polarization-selective polarization holographic element to diffract the image beam, so that the image beam converges and forms a viewpoint to enter the pupil of the human eye. The polarization state of the image beam is changed by using a second phase element, so that the image beam can be selectively diffracted or transmitted on different polarization holographic elements, thereby forming different eye points, thereby expanding the eye box of the system, and only one eye point is formed in each time period, and different eye points complement each other, thereby avoiding image crosstalk and dark area phenomena, and improving user experience.

[0008] Optionally, the image generating unit for generating an imaging light beam carrying image information includes: The image generation unit is used to selectively generate a first polarized light or a second polarized light with image information, and the first polarized light or the second polarized light is incident on the waveguide device; The near-eye display system further comprises: a primary polarization volume hologram element, used for receiving the first polarized light or the second polarized light generated by the image generation unit, wherein the primary polarization volume hologram element comprises a first polarization diffraction element and a second polarization diffraction element which are stacked, wherein the first polarization diffraction element diffracts the first polarized light and transmits the second polarized light, and the second polarization diffraction element diffracts the second polarized light and transmits the first polarized light; Wherein, the first polarized light or the second polarized light diffracted by the first-order polarization volume hologram element is incident into the waveguide device.

[0009] By adopting the above technical solution and adjusting the polarization state of the light beam in real time, dynamic viewpoint switching is achieved, which further expands the eye box range of the system and solves the problem of small eye movement range of traditional retinal projection technology.

[0010] Optionally, the image generating unit includes: A laser transmitter for emitting a line beam composed of red, green and blue modulations; A polarizing element, arranged on the light output path of the laser emitter, for converting the linear light beam emitted by the laser emitter into linear polarized light; an optical phase modulator, disposed on an outgoing light path of the polarization element, the optical phase modulator selectively converting the linearly polarized light into a first polarized light or a second polarized light; and The scanning galvanometer is arranged on the light output path of the optical phase modulator, and is used for scanning the first polarized light or the second polarized light to convert the first polarized light or the second polarized light into a divergent spherical light beam.

[0011] By adopting the above technical solution, the laser transmitter generates a thin light beam, which effectively solves the problem of convergence regulation conflict. The optical phase modulator and the first-order polarization holographic element are used together to further expand the eye movement range and solve the problem of small eye movement range in retinal projection technology.

[0012] Optionally, the optical phase modulator includes a first phase element and an electrically controlled half-wave plate arranged in sequence along the transmission direction of the optical path, the first phase element is used to convert linearly polarized light into a first polarized light, and the electrically controlled half-wave plate has an on / off state to convert the first polarized light into a second polarized light or not convert the first polarized light, or, The first phase element is used to convert linearly polarized light into second polarized light, and the electrically controlled half-wave plate has an on / off state to convert the second polarized light into the first polarized light or not convert the second polarized light.

[0013] By adopting the above technical solutions, this design not only improves the flexibility of the system, but also ensures that the imaging beam can be accurately switched under different polarization states, thereby achieving fast and accurate switching between different viewpoints, further expanding the field of view of the system and reducing image crosstalk and dark area phenomena.

[0014] Optionally, the near-eye display system also includes an eye tracking device, the second phase element has an on / off state to convert the imaging light beam into the first polarized light or the second polarized light, and the eye tracking device is connected to the second phase element and the electrically controlled half-wave plate signal.

[0015] Optionally, the eye tracking device can monitor the position of the pupil of the human eye in real time, and adjust the working state of the second phase element and the electrically controlled half-wave plate according to the pupil position, to ensure that the imaging beam can be converted into the required polarization state at the right time, so that the image beam converges to the correct eye point. This not only expands the effective eye box range of the system, but also avoids image crosstalk and dark area phenomena caused by the simultaneous existence of multiple viewpoints, thereby improving the user experience.

[0016] Optionally, the near-eye display system further includes an eye tracking device, the second phase element has an on / off state to convert the imaging light beam into the first polarized light or the second polarized light, and the eye tracking device is signal-connected to the second phase element.

[0017] By adopting the above technical solution, the function of dynamically adjusting the viewpoint position is realized, effectively expanding the field of view angle and eye box range of the system. The eye tracking device can monitor the position changes of the pupil of the eye in real time, and control the on and off state of the second phase element according to the changes in the pupil position, so that the imaging beam changes alternately under different polarization states, ensuring that the human eye can always receive a clear image. This design not only solves the problem of small eye box range in traditional retinal projection technology, but also avoids the image crosstalk and dark area phenomenon caused by the simultaneous existence of multiple viewpoints, significantly improving the user experience.

[0018] Optionally, the secondary polarization holographic element is coated on the surface of the waveguide device or embedded in the waveguide device.

[0019] By adopting the above technical solution, the secondary polarization holographic element is covered on the surface of the waveguide device or embedded in the waveguide device, which can effectively reduce the optical path loss and improve the light efficiency, while simplifying the structural design of the system and reducing the manufacturing cost. In addition, this integrated design can also improve the stability and reliability of the system and ensure normal operation in various environments.

[0020] Second aspect A near-eye display method based on retinal projection comprises the following steps: generating an imaging beam carrying image information; receiving the imaging light beam, and performing optical path folding on the imaging light beam; receiving an imaging light beam after the optical path is folded, and selectively converting the imaging light beam into a first polarized light or a second polarized light, wherein the polarization states of the first polarized light and the second polarized light are orthogonal; A secondary polarization volume hologram is provided, which includes a third polarization diffraction element and a fourth polarization diffraction element which are stacked, wherein the third polarization diffraction element diffracts the first polarized light and transmits the second polarized light, and the fourth polarization diffraction element diffracts the second polarized light and transmits the first polarized light, so as to converge the first polarized light or the second polarized light to different viewpoints.

[0021] By adopting the above technical solution, the eye box range of retinal projection technology can be effectively increased, solving the problem of small eye movement range of traditional retinal projection technology. At the same time, this method selectively converts the imaging beam into the first polarized light or the second polarized light, and uses the secondary polarized body holographic element to converge the beam to different viewpoints, ensuring that each viewpoint does not exist at the same time, avoiding image crosstalk and dark area phenomena, and improving user experience.

[0022] Optionally, the step of generating an imaging light beam carrying image information includes: selectively generating a first polarized light or a second polarized light carrying image information; Before the step of receiving the imaging light beam and performing optical path folding on the imaging light beam, the method further includes: A primary polarization volume hologram is provided, which is used to receive the first polarization light or the second polarization light carrying image information. The primary polarization volume hologram comprises a first polarization diffraction element and a second polarization diffraction element which are stacked. The first polarization diffraction element diffracts the first polarization light and transmits the second polarization light, and the second polarization diffraction element diffracts the second polarization light and transmits the first polarization light. The optical path of the diffracted first polarization light or the second polarization light is folded.

[0023] By adopting the above technical solution, it is possible to achieve the selective diffraction and transmission of the first polarized light and the second polarized light by the primary polarized volume holographic element during the retinal projection display process, and further optimize the optical path folding process. This not only ensures the effective transmission of the image light beam, but also improves the stability and reliability of the system. Specifically, through the combined use of the first polarization diffraction element and the second polarization diffraction element, precise control of light beams in different polarization states is achieved, effectively expanding the eye box range of the system, avoiding image crosstalk and dark area phenomena, and improving the user's visual experience.

[0024] Optionally, the following steps are also included: An eye tracking device is provided, and the position of the pupil of the eye is tracked in real time by the eye tracking device, and the imaging light beam is converted into the first polarized light or the second polarized light according to the position of the pupil of the eye.

[0025] By adopting the above technical solution, the eye tracking device can track the position of the eye pupil in real time, and dynamically adjust the polarization state of the imaging beam according to the pupil position, ensuring that the image beam always converges at the current position of the human eye, effectively expanding the viewing angle range of the system and improving the comfort of the user experience.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present invention uses a polarization-selective polarization holographic element to diffract the image beam, so that the image beam converges and forms a viewpoint to enter the pupil of the human eye. The polarization state of the image beam is changed by using a second phase element, so that the image beam can be selectively diffracted or transmitted on different polarization holographic elements, thereby forming different eye points, thereby expanding the eye box of the system, and only one eye point is formed in each time period, and different eye points complement each other, thereby avoiding image crosstalk and dark area phenomena, and improving user experience.

[0027] 2. By adjusting the polarization state of the light beam in real time, dynamic viewpoint switching is achieved, further expanding the eye box range of the system and solving the problem of small eye movement range of traditional retinal projection technology.

[0028] 3. The laser emitter generates a thin light beam, which effectively solves the problem of convergence adjustment conflict. The optical phase modulator and the first-order polarization holographic element are used together to further expand the eye movement range and solve the problem of small eye movement range in retinal projection technology.

[0029] 4. The eye tracking device can monitor the position of the human pupil in real time, and adjust the working state of the second phase element and the electrically controlled half-wave plate according to the pupil position, ensuring that the imaging beam can be converted into the required polarization state at the right time, so that the image beam converges to the correct eye point. This not only expands the effective eye box range of the system, but also avoids image crosstalk and dark area phenomena caused by the simultaneous existence of multiple viewpoints, improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of a near-eye display system based on retinal projection provided by a specific embodiment of the present application (the dotted line in the figure indicates the direction of the light path); Figure 2 It is a schematic diagram of a near-eye display system based on retinal projection provided by another specific embodiment of the present application (the dotted line in the figure indicates the direction of the light path).

[0031] Description of reference numerals: 10. Image generating unit; 11. Laser transmitter; 12. Polarization element; 13. Optical phase modulator; 131. First phase element; 132. Electric-controlled half-wave plate; 14. Scanning galvanometer; 20. Waveguide device; 30. First polarization volume hologram element; 31. First polarization diffraction element; 32. Second polarization diffraction element; 40. Second phase element; 50. Second polarization volume hologram element; 51. Third polarization diffraction element; 52. Fourth polarization diffraction element; 60. Eye tracking device; 70. First eye point; 71. Second eye point; 72. Third eye point; 73. Fourth eye point. DETAILED DESCRIPTION

[0032] The following is combined with Figure 1-2 This application is described in further detail.

[0033] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only possible technical implementations of the present invention, not all possible implementations. Those skilled in the art can completely combine the embodiments of the present invention to obtain other embodiments without creative work, and these embodiments are also within the scope of protection of the present invention.

[0034] The inventor of this application found that the mainstream augmented reality optical display solution will cause the human eye's convergence and accommodation conflict. Retinal projection display can solve the convergence and accommodation conflict, but its eye movement range is very small. To this end, this application mainly adopts the following near-eye display system based on retinal projection to achieve the effect of expanding the eye movement range. The following is a further detailed description of this application.

[0035] Example 1 The near-eye display system based on retinal projection provided in the embodiment of the present application is referred to as Figure 1 In one embodiment, the near-eye display system includes an image generating unit 10, a waveguide device 20, a coupling element (not shown in the figure), a second phase element 40 and a secondary polarization volume hologram element 50. The image generating unit 10 is used to generate an imaging beam with image information; the coupling element couples the imaging beam of the image generating unit 10 into the waveguide device 20, and the waveguide device 20 is used to receive the imaging beam of the image generating unit 10 and fold the optical path of the imaging beam; the second phase element 40 is used to receive the imaging beam after the optical path folding, and selectively convert the imaging beam into a first polarized light or a second polarized light, and the polarization states of the first polarized light and the second polarized light are orthogonal; the secondary polarization volume hologram element 50 is used to receive the first polarized light or the second polarized light emitted by the second phase element 40, and the secondary polarization volume hologram element 50 includes a third polarization diffraction element 51 and a fourth polarization diffraction element 52 which are stacked, the third polarization diffraction element 51 diffracts the first polarized light and transmits the second polarized light, and the fourth polarization diffraction element 52 diffracts the second polarized light and transmits the first polarized light. The first polarized light or the second polarized light is selectively transformed by the second phase element 40 so as to be converged to two different viewpoints by the secondary polarization volume hologram element 50, thereby achieving the effect of expanding the eye movement range.

[0036] Reference Figure 2In another preferred embodiment, the image generation unit 10 is used to selectively generate the first polarized light or the second polarized light with image information, the first polarized light or the second polarized light is incident into the waveguide device 20, the coupling element is a primary polarization volume hologram element 30, the primary polarization volume hologram element 30 is used to receive the first polarized light or the second polarized light generated by the image generation unit 10, the primary polarization volume hologram element 30 includes a first polarization diffraction element 31 and a second polarization diffraction element 32 which are stacked, the first polarization diffraction element 31 diffracts the first polarized light and transmits the second polarized light, the second polarization diffraction element 32 diffracts the second polarized light and transmits the first polarized light. The image generation unit 10 selectively generates the first polarized light or the second polarized light and the second phase element 40 selectively transforms the first polarized light or the second polarized light, so that the first polarized light or the second polarized light is converged to four different viewpoints through the secondary polarization volume hologram element 50, so as to further expand the effect of the eye movement range. In other embodiments, the eye movement range can also be further expanded by increasing the number of polarization volume hologram elements or other methods. In addition, the coupling element can also be a geometric element, a surface relief diffraction element, etc.

[0037] Reference Figure 2 Specifically, the image generation unit 10 includes a laser emitter 11, a polarization element 12, an optical phase modulator 13 and a scanning galvanometer 14. The laser emitter 11 is used to emit a linear light beam composed of red, green and blue modulation; the polarization element 12 is arranged on the light output path of the laser emitter 11, and is used to convert the linear light beam emitted by the laser emitter 11 into linear polarized light; the optical phase modulator 13 is arranged on the light output path of the polarization element 12, and the optical phase modulator 13 selectively converts the linear polarized light into the first polarized light or the second polarized light; the scanning galvanometer 14 is arranged on the light output path of the optical phase modulator 13, and the scanning galvanometer 14 is used to scan the first polarized light or the second polarized light to convert the first polarized light or the second polarized light into a divergent spherical light beam.

[0038] Among them, the line beam emitted by the laser emitter 11 is a thin beam, where the thin beam refers to different light rays emitted from the same object point (or virtual image point), which arrive at the pupil position of the human eye, and the beam cross section formed is less than 2mm, and the difference in the angle of the light rays is less than 5°. Since the light beam entering the human eye is a thin beam, the human eye can clearly see the image within a large depth of field. When the human eye focuses and the binoculars converge to observe natural real objects at different distances, the virtual image can be clearly displayed independently of the focusing of the lens, thereby solving the convergence and adjustment conflict.

[0039] Optionally, the polarizing element 12 may be a wire grid polarizer, a dichroic polarizer, a birefringent polarizer, or the like.

[0040] At the same time, the optical phase modulator 13 includes a first phase element 131 and an electrically controlled half-wave plate 132 which are sequentially arranged along the transmission direction of the optical path. The first phase element 131 may be a liquid crystal phase modulator, which is used to convert linearly polarized light into first polarized light, and the electrically controlled half-wave plate 132 has an on / off state to selectively convert the first polarized light into second polarized light or not convert the first polarized light. For example, in the off state, the electrically controlled half-wave plate 132 has no phase modulation function for the light beam, and at this time, the first polarized light is still the first polarized light after passing through the electrically controlled half-wave plate 132. In the on state, the electrically controlled half-wave plate 132 has a phase modulation function for the light beam, and the first polarized light is converted into the second polarized light after passing through the electrically controlled half-wave plate 132.

[0041] Preferably, the scanning galvanometer 14 is a two-dimensional scanning galvanometer, which can be controlled to rotate in two directions, which usually refer to the horizontal direction and the vertical direction. The light beam is reflected by the two-dimensional scanning galvanometer to form a divergent spherical light beam.

[0042] The divergent spherical light beam is incident on the primary polarization volume hologram element 30. In this embodiment, the primary polarization volume hologram element 30 is covered on the surface of the waveguide device 20 and is directly opposite to the coupling-in region of the waveguide device 20. The first polarized light or the second polarized light diffracted by the primary polarization volume hologram element 30 is coupled into the waveguide device 20 through the coupling-in region, and the waveguide device 20 folds the light path of the light beam. Optionally, the waveguide device 20 may be a grating waveguide, which is used to receive the imaging light beam generated by the image generation unit 10 and fold the light path of the imaging light beam.

[0043] In this embodiment, the second phase element 40 is embedded in the waveguide device 20. The second phase element 40 can be an electrically controlled phase element. The second phase element 40 is used to receive the imaging light beam after the optical path folding, and selectively convert the imaging light beam into the first polarized light or the second polarized light. The electrically controlled phase element can be a liquid crystal phase modulator, which changes the arrangement of liquid crystal molecules by applying voltage, thereby changing the polarization state of the light beam. In addition, the electrically controlled phase element can also be a magneto-optical modulator, which uses the change of the magnetic field to change the polarization state of the light beam.

[0044] Among them, the secondary polarization hologram element 50 is arranged in the out-coupling area of ​​the waveguide device 20, and the secondary polarization hologram element 50 is covered on the surface of the out-coupling area or embedded in the waveguide device 20. Specifically, the secondary polarization hologram element 50 can be embedded in the waveguide device 20 by a gluing process or a thin film embedding molding process, and the third polarization diffraction element 51 and the fourth polarization diffraction element 52 can also be fixed together by gluing or other methods to form a composite structure.

[0045] At the same time, the near-eye display system also includes an eye tracking device 60. The second phase element 40 has an on / off state to convert the imaging light beam into the first polarized light or the second polarized light. The eye tracking device 60 is signal-connected to the second phase element 40 and the electrically-controlled half-wave plate 132. The eye tracking device 60 can monitor the position of the pupil of the human eye in real time, and adjust the working states of the second phase element 40 and the electrically-controlled half-wave plate 132 according to the pupil position, to ensure that the imaging light beam can be converted into the desired polarization state at the correct time, so that the image light beam converges to the correct eye point.

[0046] The implementation principle of this embodiment is: this system has 4 states, namely state 1 / 2 / 3 / 4.

[0047] In state 1, the electrically controlled half-wave plate 132 is in the off state, the light beam emitted by the scanning galvanometer 14 is the first polarized light, and enters the first-order polarization volume hologram element 30, the first polarization diffraction element 31 diffracts the first polarized light, and its emitted light is still the first polarized light, and the second polarization diffraction element 32 has no effect on the first polarized light. The second phase element 40 is in the off state, and the polarization state of the first polarized light remains unchanged after being emitted by the second phase element 40, and is still the first polarized light. The third polarization diffraction element 51 diffracts the incident first polarized light into a converging spherical light beam of the first polarization, and its convergence point is the first eye point 70. The fourth polarization diffraction element 52 has no effect on the first polarized light. If the pupil of the human eye is at the first eye point 70, the observer will see the image.

[0048] In state 2, the electrically controlled half-wave plate 132 is in the on state, the light beam emitted by the scanning galvanometer 14 is the second polarized light, and is incident on the primary polarization volume hologram element 30, the first polarization diffraction element 31 has no effect on the second polarized light, the second polarization diffraction element 32 diffracts the second polarized light, and its output light is still the second polarized light. Since the diffraction directions of the output light of the first polarization diffraction element 31 and the second polarization diffraction element 32 for the incident light in the same direction are different, the directions of the light beams emitted from the polarization selective diffraction element in state 2 and state 1 are different. The second phase element 40 is in the on state, and the second polarized light is converted into the first polarized light after being emitted by the second phase element 40. The third polarization diffraction element 51 diffracts the incident first polarized light into a converging spherical light beam of the first polarization, and its convergence point is the second eye point 71. The fourth polarization diffraction element 52 has no effect on the first polarized light. If the pupil of the human eye is at the second eye point 71, the observer will see the image.

[0049] In state 3, the electrically controlled half-wave plate 132 is in the off state, the light beam emitted by the scanning galvanometer 14 is the first polarized light, and is incident on the primary polarization volume hologram element 30, the first polarization diffraction element 31 diffracts the first polarized light, and its emitted light is still the first polarized light, and the second polarization diffraction element 32 has no effect on the first polarized light. The second phase element 40 is in the on state, and the first polarized light is converted into the second polarized light after being emitted by the second phase element 40. The third polarization diffraction element 51 has no effect on the second polarized light, and the fourth polarization diffraction element 52 diffracts the incident second polarized light into a converging spherical light beam of the second polarization, and its convergence point is the third eye point 72. If the pupil of the human eye is at the third eye point 72, the observer will see the image.

[0050] In state 4, the electrically controlled half-wave plate 132 is in the on state, the light beam emitted by the scanning galvanometer 14 is the second polarized light, and is incident on the primary polarization volume hologram element 30, the first polarization diffraction element 31 has no effect on the second polarized light, the second polarization diffraction element 32 diffracts the second polarized light, and its emitted light is still the second polarized light. The second phase element 40 is in the off state, and the polarization state of the second polarized light remains unchanged after being emitted by the second phase element 40, and is still the second polarized light. The third polarization diffraction element 51 has no effect on the second polarized light, and the fourth polarization diffraction element 52 diffracts the incident second polarized light into a converging spherical light beam of the second polarization, and its convergence point is the fourth eye point 73. If the pupil of the human eye is at the fourth eye point 73, the observer will see the image.

[0051] In conjunction with the eye tracking device 60, the position of the pupil of the eye is tracked in real time, and the system is switched to one of the states 1 / 2 / 3 / 4 according to the position of the pupil of the eye, so that the human eye can receive the image. The system state can only be in one of the states 1 / 2 / 3 / 4, that is, there is an image at only one eye point among the first eye point 70, the second eye point 71, the third eye point 72 or the fourth eye point 73. This avoids two images entering the human eye at the same time, thereby causing image crosstalk. This method can not only expand the eye movement range, but also avoid image crosstalk and dark area phenomena, significantly improving the user experience.

[0052] Example 2 This embodiment also discloses a near-eye display method based on retinal projection, comprising the following steps: S10, generating an imaging beam with image information, including: S11, the image generating unit 10 can selectively generate the first polarized light or the second polarized light with image information. Specifically, the electrically controlled half-wave plate 132 can selectively generate the first polarized light or the second polarized light.

[0053] S12. Provide a primary polarization volume hologram 30, which is used to receive the first polarized light or the second polarized light carrying image information. The primary polarization volume hologram 30 includes a first polarization diffraction element 31 and a second polarization diffraction element 32 which are stacked. The first polarization diffraction element 31 diffracts the first polarized light and transmits the second polarized light, and the second polarization diffraction element 32 diffracts the second polarized light and transmits the first polarized light, and performs optical path folding on the diffracted first polarized light or the second polarized light.

[0054] S20, receiving the imaging light beam, and performing optical path folding on the imaging light beam.

[0055] Specifically, the imaging light beam may be received and transmitted via the waveguide device 20 .

[0056] S30, receiving the imaging light beam after the optical path folding, and selectively converting the imaging light beam into a first polarized light or a second polarized light, wherein the polarization states of the first polarized light and the second polarized light are orthogonal.

[0057] Specifically, the second phase element 40 is used to receive the imaging light beam after the optical path is folded, and the second phase element 40 may be an electrically controlled phase element.

[0058] S40. Provide a secondary polarization hologram 50, which includes a third polarization diffraction element 51 and a fourth polarization diffraction element 52 that are stacked, and the third polarization diffraction element 51 diffracts the first polarized light and transmits the second polarized light, and the fourth polarization diffraction element 52 diffracts the second polarized light and transmits the first polarized light, so as to converge the first polarized light or the second polarized light to different viewpoints.

[0059] S50, providing an eye tracking device 60, using the eye tracking device 60 to track the position of the eye pupil in real time, and converting the imaging light beam into the first polarized light or the second polarized light according to the position of the eye pupil.

[0060] Specifically, the state of the image generating unit 10 and the second phase element 40 is controlled by the eye tracking device 60 to select the first polarized light or the second polarized light for transmission and diffraction according to the position of the eye pupil, so that the first polarized light or the second polarized light can converge to different viewpoints, thereby avoiding two images entering the human eye at the same time and causing image crosstalk problems.

[0061] The present application enables the imaging light beam to be selectively diffracted or transmitted on different polarization diffraction elements, thereby forming different eye points in real time, thereby expanding the eye box of the system.

[0062] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A near-eye display system based on retinal projection, characterized in that: include: An image generating unit (10), used for generating an imaging light beam carrying image information; A waveguide device (20) for receiving an imaging light beam from the image generating unit (10) and performing optical path folding on the imaging light beam; A second phase element (40) is used to receive the imaging light beam after the optical path is folded, and selectively convert the imaging light beam into a first polarized light or a second polarized light, wherein the polarization states of the first polarized light and the second polarized light are orthogonal; a secondary polarization volume hologram element (50) for receiving the first polarized light or the second polarized light emitted by the second phase element (40), the secondary polarization volume hologram element (50) comprising a third polarization diffraction element (51) and a fourth polarization diffraction element (52) which are stacked, the third polarization diffraction element (51) diffracting the first polarized light and transmitting the second polarized light, and the fourth polarization diffraction element (52) diffracting the second polarized light and transmitting the first polarized light; The second phase element (40) selectively transforms the first polarized light or the second polarized light so as to converge the first polarized light or the second polarized light to different viewpoints through the secondary polarization volume hologram element (50).

2. The near-eye display system based on retinal projection according to claim 1, characterized in that: The image generating unit (10) for generating an imaging light beam carrying image information comprises: The image generation unit (10) is used to selectively generate a first polarized light or a second polarized light carrying image information, and the first polarized light or the second polarized light is incident on the waveguide device (20); The near-eye display system further comprises: A primary polarization volume hologram element (30) for receiving the first polarization light or the second polarization light generated by the image generation unit (10), the primary polarization volume hologram element (30) comprising a first polarization diffraction element (31) and a second polarization diffraction element (32) which are stacked, the first polarization diffraction element (31) diffracting the first polarization light and transmitting the second polarization light, the second polarization diffraction element (32) diffracting the second polarization light and transmitting the first polarization light; The first polarized light or the second polarized light diffracted by the primary polarization holographic element (30) is incident on the waveguide device (20).

3. The near-eye display system based on retinal projection according to claim 2, characterized in that: The image generation unit (10) comprises: A laser transmitter (11) for transmitting a linear beam composed of red, green and blue modulations; A polarizing element (12) is arranged on the light output path of the laser emitter (11) and is used to convert the linear light beam emitted by the laser emitter (11) into linear polarized light; an optical phase modulator (13), arranged on the light output path of the polarization element (12), wherein the optical phase modulator (13) selectively converts the linearly polarized light into the first polarized light or the second polarized light; and A scanning galvanometer (14) is arranged on the light output path of the optical phase modulator (13), and the scanning galvanometer (14) is used to scan the first polarized light or the second polarized light to convert the first polarized light or the second polarized light into a divergent spherical light beam.

4. The near-eye display system based on retinal projection according to claim 3, characterized in that: The optical phase modulator (13) comprises a first phase element (131) and an electrically controlled half-wave plate (132) arranged in sequence along the transmission direction of the optical path, the first phase element (131) being used to convert linearly polarized light into first polarized light, the electrically controlled half-wave plate (132) having an on / off state to convert the first polarized light into second polarized light or not to convert the first polarized light, or, The first phase element (131) is used to convert linearly polarized light into second polarized light, and the electrically controlled half-wave plate (132) has an on / off state to convert the second polarized light into the first polarized light or not to convert the second polarized light.

5. The near-eye display system based on retinal projection according to claim 4, characterized in that: The near-eye display system further comprises an eye tracking device (60), the second phase element (40) having an on / off state to convert the imaging light beam into the first polarized light or the second polarized light, and the eye tracking device (60) is signal-connected to the second phase element (40) and the electrically controlled half-wave plate (132).

6. The near-eye display system based on retinal projection according to claim 1, characterized in that: The near-eye display system further comprises an eye tracking device (60), the second phase element (40) having an on / off state to convert the imaging light beam into the first polarized light or the second polarized light, and the eye tracking device (60) is signal-connected to the second phase element (40).

7. The near-eye display system based on retinal projection according to claim 1, characterized in that: The secondary polarization holographic element (50) is coated on the surface of the waveguide device (20) or embedded in the waveguide device (20).

8. A near-eye display method based on retinal projection, characterized in that: The following steps are involved: generating an imaging beam carrying image information; receiving the imaging light beam, and performing optical path folding on the imaging light beam; receiving an imaging light beam after the optical path is folded, and selectively converting the imaging light beam into a first polarized light or a second polarized light, wherein the polarization states of the first polarized light and the second polarized light are orthogonal; A secondary polarization volume hologram element (50) is provided, wherein the secondary polarization volume hologram element (50) comprises a third polarization diffraction element (51) and a fourth polarization diffraction element (52) which are stacked, wherein the third polarization diffraction element (51) diffracts the first polarization light and transmits the second polarization light, and the fourth polarization diffraction element (52) diffracts the second polarization light and transmits the first polarization light, so as to converge the first polarization light or the second polarization light to different viewpoints.

9. The near-eye display method based on retinal projection according to claim 8, characterized in that: The step of generating an imaging light beam with image information comprises: selectively generating a first polarized light or a second polarized light carrying image information; Before the step of receiving the imaging light beam and performing optical path folding on the imaging light beam, the method further includes: A primary polarization volume hologram (30) is provided. The primary polarization volume hologram (30) is used to receive first polarized light or second polarized light carrying image information. The primary polarization volume hologram (30) comprises a first polarization diffraction element (31) and a second polarization diffraction element (32) which are stacked. The first polarization diffraction element (31) diffracts the first polarized light and transmits the second polarized light. The second polarization diffraction element (32) diffracts the second polarized light and transmits the first polarized light. The optical path of the diffracted first polarized light or the second polarized light is folded.

10. The near-eye display method based on retinal projection according to claim 8, characterized in that: The following steps are also included: An eye tracking device (60) is provided, and the position of the pupil of the eye is tracked in real time by using the eye tracking device (60), and an imaging light beam is converted into a first polarized light or a second polarized light according to the position of the pupil of the eye.

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