Holographic optical element preparation method and system and double-view-angle head-up display system

Abstract

The invention belongs to the technical field of optical processing, and relates to a holographic optical element preparation method and system and a double-view-angle head-up display system, and the method comprises the steps: determining a first direction vector in a three-dimensional space according to the design parameters of a reference light beam and a signal light beam relative to a holographic optical element; adjusting the angle of the holographic optical element to enable the holographic optical element to be in a vertical position in the three-dimensional coordinate system; calculating a second direction vector according to the first direction vector and the adjustment angle of the vertical position; adjusting the angle of the holographic optical element again according to the second direction vector to enable the reference light beam and the signal light beam to be in the same plane; and performing exposure interference on the holographic optical element by using the holographic optical element preparation system so as to enable the photosensitive material in the holographic optical element to form a standing wave pattern. The three-dimensional light path structure in the optical element preparation process is converted into the two-dimensional exposure interference through the light beam position conversion method, the preparation complexity is reduced, and the head-up display accuracy is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of optical processing technology, specifically relating to a method and system for preparing holographic optical elements and a dual-view head-up display system. Background Technology

[0002] In automotive head-up displays (HUDs), HOE (Holographic Optical Element) based solutions have significant development potential due to their simultaneous high diffraction efficiency and high transmittance.

[0003] Holograms are recorded through the interference of a reference beam and a signal beam (also known as an object beam). In reflective holographic optical elements, the reference beam and the signal beam are typically incident from the same side of the medium, but their propagation directions are opposite, thus forming a standing wave pattern within the medium and recording interference fringes. When the hologram is reconstructed, the signal beam can be reconstructed by illuminating it with the reference beam. Reflective holographic optical elements for automotive displays are typically designed to expose the reference beam vertically, while the signal beam has a certain angle of incidence relative to the normal of the holographic optical element. This allows an image to be formed on a windshield tilted at a predetermined angle, and the diffracted light to enter the eye horizontally along the line of sight.

[0004] The optical path for fabricating holographic optical elements presents a two-dimensional structure in space, namely, the HOE substrate is located in the XOZ plane, the reference light is perpendicularly irradiated onto the HOE substrate along the Y-axis, and the signal light is parallel to the XOY plane and irradiates the other side of the HOE substrate.

[0005] However, when holographic optical elements require multi-view or non-fixed diffraction angle designs, the exposure optical path of the holographic optical element must present a three-dimensional spatial structure. That is, the reference light and signal light cannot be exposed on a horizontal platform alone; spatial lifting or three-dimensional deflection of the beam must be achieved through optical equipment. This not only increases the experimental complexity but also places higher demands on the accuracy and stability of the equipment. Therefore, how to reduce the three-dimensional spatial complexity in the fabrication process of holographic optical elements while ensuring the accuracy of holographic optical element fabrication has become an urgent problem to be solved. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method, system and dual-view head-up display system for fabricating holographic optical elements, in order to solve the technical problem of reducing the three-dimensional spatial complexity in the fabrication process of holographic optical elements and ensuring the accuracy of holographic optical element fabrication.

[0007] This invention provides a method for fabricating holographic optical elements, applied to a holographic optical element fabrication system, comprising: Based on the design parameters of the reference beam and the signal beam relative to the holographic optical element, determine the first direction vector of the reference beam and the signal beam in three-dimensional space; Adjust the angle of the holographic optical element so that the holographic optical element is in a vertical position in the three-dimensional coordinate system; The second direction vector of the reference beam and the signal beam in three-dimensional space is calculated based on the first direction vector and the adjustment angle of the vertical position; The angle of the holographic optical element is adjusted again according to the second direction vector so that the reference beam and the signal beam are in the same plane; The holographic optical element fabrication system is used to expose and interfere the holographic optical element after the angle is adjusted, so that the photosensitive material in the holographic optical element forms a standing wave pattern.

[0008] In one embodiment of the present invention, adjusting the angle of the holographic optical element so that the holographic optical element is in a vertical position in the three-dimensional coordinate system includes: rotating the holographic optical element about the Y-axis so that the holographic optical element is perpendicular to the XOY plane of the three-dimensional coordinate system.

[0009] In one embodiment of the present invention, calculating the second direction vector of the reference beam and the signal beam in three-dimensional space based on the first direction vector and the adjustment angle of the vertical position includes: The rotation matrix corresponding to the vertical position of the holographic optical element is obtained based on the adjustment angle of the vertical position. The second direction vector of the reference beam and the signal beam in three-dimensional space is calculated based on the rotation matrix and the first direction vector.

[0010] In one embodiment of the present invention, the step of readjusting the angle of the holographic optical element according to the second direction vector so that the reference beam and the signal beam are in the same plane includes: rotating the holographic optical element around the Z-axis and X-axis respectively according to the second direction vector so that the reference beam and the signal beam are in the XOY plane of the three-dimensional coordinate system.

[0011] This invention provides a holographic optical element fabrication system for use in head-up display systems, comprising: A laser, used to generate a laser beam; A beam-tuning module is positioned along the propagation path of the laser beam to adjust the horizontal and sway of the laser beam to obtain collimated laser light. A beam splitting module is disposed on the propagation path of the collimated laser and is used to split the parallel laser beam of the collimated laser into a collimated reference beam and a collimated signal beam. A beam expander module is disposed on the propagation path of the collimated reference beam and the collimated signal beam, respectively, and is used to amplify the collimated reference beam and the collimated signal beam to obtain an initial reference beam and an initial signal beam. A reference light module is disposed on the propagation path of the initial reference beam and is used to reflect the initial reference beam to one side of the holographic optical element; A signal light module is disposed in the propagation path of the signal beam and is used to reflect the initial signal beam to the other side of the holographic optical element; The holographic optical element is prepared by exposing and interfering the holographic photosensitive material according to the holographic optical element preparation method to form a standing wave pattern.

[0012] In one embodiment of the present invention, the beam splitting module includes: The first half-wave plate is used to adjust the polarization state of the collimated laser so that the collimated laser can have different splitting ratios when passing through the polarization beam splitter. A polarization beam splitter is used to split the adjusted collimated laser beam to generate a collimated reference beam and a collimated signal beam. The second half-wave plate is disposed on the propagation path of the collimated signal beam to adjust the polarization state of the collimated signal beam so that the collimated reference beam and the collimated signal beam passing through the polarization beam splitter have the same polarization state.

[0013] In one embodiment of the present invention, the beam expanding module includes: A microscope objective is used to expand and amplify the collimated reference beam and the collimated signal beam. A pinhole filter is used to filter out stray light in the expanded collimated reference beam and the collimated signal beam. A collimating lens is used to collimate the expanded collimated reference beam and the collimated signal beam to form an initial reference beam and an initial signal beam.

[0014] In one embodiment of the present invention, the reference optical module includes: A reflector is used to reflect the aligned initial reference beam, wherein the propagation path of the reflected initial reference beam is perpendicular to one side of the holographic optical element. A lens is used to diverge the reflected initial reference beam to form a reference beam.

[0015] In one embodiment of the present invention, the signal optical module includes: A reflector is used to reflect the initial signal beam after alignment processing, wherein the reflected initial signal beam illuminates the other side of the holographic optical element at a preset angle; A lens is vertically positioned in the propagation path of the initial signal beam to converge the initial signal beam; A scattering film is used to scatter the initial signal beam to form a signal beam.

[0016] This invention provides a holographic optical element fabrication system for use in head-up display systems, comprising: An image source is used to emit the beam of light to be displayed to the holographic combiner; A holographic combiner includes a first holographic optical element and a second holographic optical element, wherein the first holographic optical element is used to diffract the light beam to be displayed into the eyes of the driver's seat user, and the second holographic optical element is used to diffract the light beam to be displayed into the eyes of the passenger's seat user; The first holographic optical element and the second holographic optical element are respectively fabricated using a holographic optical element fabrication system.

[0017] The beneficial effects of this invention are as follows: In the method for fabricating holographic optical elements, this invention transforms the holographic optical element into a vertical position by rotation in three-dimensional space, and then rotates the holographic optical element to transform the incident direction of the signal beam in the original three-dimensional space into the incident direction in a two-dimensional plane, thereby completing the exposure interference in the two-dimensional plane, so that the three-dimensional optical path structure is transformed into a two-dimensional optical path structure. While ensuring the accuracy of holographic optical element fabrication, the complexity of the fabrication process is reduced. The holographic optical element is exposed using the transformed two-dimensional exposure geometry, thereby obtaining holographic optical characteristics equivalent to the three-dimensional design. In the holographic optical element fabrication system, a converging beam is used as the signal beam, so that the field of vision of the driver is not limited by the size of the holographic optical element, thus ensuring the certainty and clarity of the field of vision. In a dual-view head-up display system, a single projector provides the image source. By utilizing the angle selectivity of the scattering holographic optical element, the beam of light to be displayed emitted from the image source is diffracted at different angles by the first and second holographic optical elements and directed to the eyes of the driver and passenger, respectively, so that both the driver and passenger can see the same image with identical color and content. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0019] Figure 1 This is a schematic diagram of the structure of a dual-view head-up display system provided in one embodiment of the present invention; Figure 2 This is a schematic diagram of a holographic optical element fabrication system provided in one embodiment of the present invention; Figure 3 This is a light distribution diagram of a conventional fabrication optical path provided in one embodiment of the present invention; Figure 4 This is a light distribution diagram of the optical path prepared after focusing processing according to one embodiment of the present invention; Figure 5 This is a flowchart illustrating a dual-view head-up display method provided in one embodiment of the present invention; Figure 6 This is a schematic diagram of a three-dimensional spatial coordinate system for adjusting the angle of a holographic optical element according to an embodiment of the present invention; Among them, 101 is the image source; 102 is the holographic combiner; 1021 is the first holographic optical element; 1022 is the second holographic optical element; 1031 is the driver's seat user; 1032 is the passenger seat user; 200 is the laser; 301 is the first reflecting mirror; 302 is the second reflecting mirror; 401 is the first half-wave plate; 402 is the polarization beam splitter; 403 is the second half-wave plate; 501 is the first microscope objective; 502 is the second microscope objective; 503 is the first pinhole filter; 504 is the second pinhole filter; 505 is the first collimating lens; 506 is the second collimating lens; 601 is the third reflecting mirror; 602 is the first lens; 701 is the fourth reflecting mirror; 702 is the scattering film; 703 is the second lens; 800 is the holographic optical element; 801 is the HOE substrate; 802 is the holographic photosensitive material; 901 is the reference beam; 902 is the signal beam. Detailed Implementation

[0020] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0022] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0023] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0024] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0025] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0026] Example 1 Please see Figure 1 As shown, a dual-view head-up display system includes: an image source 101 for emitting a beam of light to be displayed to a holographic combiner 102; the holographic combiner 102 includes a first holographic optical element 1021 and a second holographic optical element 1022, wherein the first holographic optical element 1021 is used to diffract the beam of light to be displayed into the eyes of a driver's seat user 1031, and the second holographic optical element 1022 is used to diffract the beam of light to be displayed into the eyes of a passenger seat user 1032; wherein the first holographic optical element 1021 and the second holographic optical element 1022 are respectively fabricated by a holographic optical element fabrication system.

[0027] Specifically, the first holographic optical element 1021 and the second holographic optical element 1022 are located at a first position and a second position on the windshield, respectively. For example, the first holographic optical element 1021 is located on the left half of the windshield, and the second holographic optical element 1022 is located on the right half of the windshield. The first holographic optical element 1021 on the left half and the second holographic optical element 1022 on the right half together constitute the windshield of the car.

[0028] Furthermore, from the first perspective of the driver's seat user 1031, the image source 101 is projected onto the holographic combiner 102, and the light beam to be displayed is diffracted into the eyes of the driver's seat user 1031 through the first holographic optical element 1021; from the second perspective of the passenger seat user 1032, the image source 101 is projected onto the holographic combiner 102, and the light beam to be displayed is diffracted into the eyes of the passenger seat user 1032 through the second holographic optical element 1022.

[0029] In this embodiment of the invention, the image source 101 can be provided by an LBS projector (Laser Beam Scanning Projector) or an LED projector (Light Emitting Diode Projector). The image source 101 illuminates the holographic combiner 102 in the normal direction of the holographic combiner 102 and is diffracted by the holographic optical elements on the holographic combiner 102 so as to be directed into the eyes of the driver's seat user 1031 and the passenger seat user 1032 respectively.

[0030] In this embodiment of the invention, the dual-view head-up display system uses a single projector to provide an image source 101. Utilizing the angle selectivity of the scattering holographic optical element, the beam of light to be displayed emitted by the image source 101 is diffracted at different angles into the eyes of the driver's seat user 1031 and the passenger's seat user 1032, respectively, by the first image and the second image generated by the first holographic optical element 1021 and the second holographic optical element 1022. This ensures that both the driver's seat user 1031 and the passenger's seat user 1032 can see the same image (same color, clarity, etc.).

[0031] Example 2 Please see Figure 2 As shown, a holographic optical element fabrication system is applied to a head-up display system, including: a laser 200, a beam modulation module, a beam splitting module, a beam expanding module, a reference light module, a signal light module, and holographic optical elements.

[0032] It should be noted that the holographic optical element fabrication system is built on an air-floating platform, and the entire optical path is on a horizontal plane, exhibiting a two-dimensional property. The holographic optical element is formed by interferometric exposure of the holographic photosensitive material 802 with a reference beam and a signal beam. The application of the holographic optical element in the dual-view head-up display process is the reproduction process of the holographic optical element's optical path. Specifically, the exposure of the holographic optical element uses a divergent light source and a converging light source as the reference beam and signal beam, respectively. The reference beam corresponds to the projection beam, and the diffracted beam generated by the holographic optical element enters the human eye horizontally.

[0033] In the optical path for fabricating holographic optical elements, the reference beam and signal beam are formed by a single laser beam through processes such as beam splitting, beam expansion, and filtering. For the reference beam and signal beam of a reflective holographic optical element, they are respectively irradiated on the front and rear sides of the holographic optical element. The angle between the reference beam, signal beam, and holographic optical element depends on the usage angle of the holographic optical element in the head-up display system and the design angle of the diffraction beam.

[0034] In this embodiment of the invention, the laser 200 is used to generate a laser beam; the beam-tuning module, disposed on the propagation path of the laser beam, includes a first reflector 301 and a second reflector 302, and is used to adjust the horizontal and sway of the laser beam to obtain collimated laser light, so that the laser beam passes through the first filter in a collimated manner.

[0035] In this embodiment of the invention, the beam splitting module is disposed on the propagation path of the collimated laser and is used to split the parallel laser beam of the collimated laser into a collimated reference beam and a collimated signal beam.

[0036] Furthermore, the beam splitting module includes: The first half-wave plate 401 is disposed on the propagation path of the collimated laser, before the polarization beam splitter 402, and is used to adjust the polarization state of the collimated laser so that the collimated laser has different splitting ratios when passing through the polarization beam splitter 402. Polarization beam splitter 402 is used to split the adjusted collimated laser beam to generate a collimated reference beam and a collimated signal beam. The second half-wave plate 403 is disposed on the propagation path of the collimated signal beam, after the polarization beam splitter 402, and is used to adjust the polarization state of the collimated signal beam so that the collimated reference beam and the collimated signal beam passing through the polarization beam splitter 402 have the same polarization state.

[0037] In this embodiment of the invention, the beam expanding module is respectively disposed on the propagation path of the collimated reference beam and the collimated signal beam, and is used to amplify the collimated reference beam and the collimated signal beam to obtain the reference beam and the signal beam; specifically, the beam expanding module expands and filters stray light from the low scattering angle laser beams of the collimated reference beam and the collimated signal beam to generate a large-size parallel beam.

[0038] Furthermore, the beam expander module includes: A first microscope objective 501 and a second microscope objective 502 are disposed on the propagation path of the collimated reference beam and are used to expand and amplify the collimated reference beam; the second microscope objective 502 is disposed on the propagation path of the collimated signal beam and is used to expand and amplify the collimated signal beam. A first pinhole filter 503 and a second pinhole filter 504 are used to filter out stray light in the collimated reference beam after the beam expansion, after the first microscope objective 501 is applied; and a second pinhole filter 504 is used to filter out stray light in the collimated signal beam after the beam expansion, after the second microscope objective 502 is applied, in order to filter out stray light outside the laser Gaussian beam and improve beam quality. The first collimating lens 505, located after the first pinhole filter 503, is used to collimate the expanded collimated reference beam to form a collimated parallel beam, i.e., the initial reference beam. The second collimating lens 506, located after the second pinhole filter 504, is used to collimate the expanded collimated signal beam to form a collimated parallel beam, i.e., the initial signal beam.

[0039] In this embodiment of the invention, a reference light module is disposed on the propagation path of the initial reference beam and is used to reflect the initial reference beam to one side of the holographic optical element.

[0040] Furthermore, the reference optical module includes: The third reflecting mirror 601 is disposed on the propagation path of the reference beam and is used to reflect the initial reference beam after alignment processing, wherein the propagation path of the reflected initial reference beam is perpendicular to one side of the holographic optical element. The first lens 602, located after the third reflecting mirror 601, is used to diverge the reflected initial reference beam and has a certain focal length for the holographic optical element to form a reference beam.

[0041] In this embodiment of the invention, a signal light module is disposed on the propagation path of the initial signal beam and is used to reflect the initial signal beam to the other side of the holographic optical element.

[0042] Furthermore, the signal optical module includes: The fourth reflector 701 is disposed on the propagation path of the initial signal beam and is used to reflect the aligned initial signal beam. The reflected initial signal beam illuminates the other side of the holographic optical element at a specific angle to the holographic optical element. The scattering film 702 is located on the same side where the initial signal beam illuminates the holographic optical element, and is used to scatter the initial signal beam to form a signal beam.

[0043] In this embodiment of the invention, the holographic optical element includes a HOE substrate 801 and a holographic photosensitive material 802; the holographic optical element exposes and interferes with the holographic photosensitive material 802 according to the holographic optical element preparation method to form a standing wave pattern.

[0044] Example 3 A holographic optical element fabrication system includes: a laser 200, a beam modulation module, a beam splitting module, a beam expanding module, a reference light module, a signal light module, and holographic optical elements.

[0045] The laser 200, beam modulation module, beam splitting module, beam expanding module, and reference light module are as described in Embodiment 2. The signal light module includes: The fourth reflector 701 is disposed on the propagation path of the initial signal beam and is used to reflect the aligned initial signal beam. The reflected initial signal beam illuminates the other side of the holographic optical element at a specific angle to the holographic optical element. The second lens 703, located after the fourth reflector 701, is vertically positioned on the propagation path of the initial signal beam to converge the initial signal beam and thus expand the field of vision of the driver. The scattering film 702 is located on the same side where the initial signal beam illuminates the holographic optical element, and is used to scatter the initial signal beam to form a signal beam.

[0046] Please see Figure 3 As shown, in the prior art, in a head-up display system, the driver's field of vision is limited. The diffusion angle mainly depends on the scattering film 702. The distance between the human eye and the holographic optical element However, it will be limited by the size of the holographic optical elements. Constraints, among which The tilt angle of the holographic optical element is shown in the following formula:

[0047] Please see Figure 4 As shown in this embodiment of the invention, when the second lens 703 is used to converge the initial signal beam and the converged light is used as the signal beam, the central beam of the holographic optical element converges to the position of the human eye. Furthermore, due to the diffusion characteristics of the scattering film 702, its scattering angle diverges angularly with the principal ray as the center. Therefore, in this case, the driver's field of vision... The magnitude of the divergence of the central ray will no longer be limited by the size of the holographic optical element. As shown in the following formula:

[0048] In the holographic optical element fabrication system, the signal beam is made into a converging beam, and the focal length of the lens is at the position observed by the human eye. This ensures that the driver's field of vision is not limited by the size of the holographic optical element, guaranteeing the certainty and clarity of the field of vision.

[0049] Example 4 This invention provides a method for fabricating holographic optical elements, applied to a holographic optical element fabrication system, comprising the following steps: S1. Determine the first direction vector of the reference beam and the signal beam in three-dimensional space based on the design parameters of the reference beam and the signal beam relative to the holographic optical element.

[0050] Please see Figure 5 As shown, this is a schematic diagram of the three-dimensional spatial structure of the reference beam 901 and the signal beam 902 relative to the holographic optical element 800 through two-dimensional coordinate transformation. For example, the reference beam 901 and the signal beam 902 in the figure only consider point light sources of the principal ray.

[0051] Wherein, the positive X-axis is the direction from the windshield to the driver, the positive Y-axis is the direction from the driver's seat to the passenger seat, the negative Y-axis is the direction from the passenger seat to the driver, the positive Z-axis is the direction from the bottom of the car to the top, and the negative Z-axis is the direction from the top of the car to the bottom.

[0052] For example, such as Figure 6 As shown in (a), the windshield (holographic optical element 800) tilt angle is set to 45° according to the design parameters of the reference beam 901 and the signal beam 902 relative to the holographic optical element 800. In three-dimensional space, the first direction vector corresponding to the reference beam 901 is located directly below the X-axis, with an angle of 45° between it and the X-axis. The normal of the holographic optical element 800 is located below the XOY plane, with an angle of 45° between it and the XOY plane.

[0053] Specifically, when the image source 101 is located in the center of the windshield, the windshield is tilted at 45°, the angle between the reference beam 901 and the X-axis is 45°, the angle between the signal beam 902 and the holographic optical element 800 is 30°, the normal of the holographic optical element 800 is collinear with the first direction vector corresponding to the reference beam 901, and the reference beam... ;Signal light The normal of the holographic optical element 800 .

[0054] S2. Adjust the angle of the holographic optical element so that the holographic optical element is in a vertical position in the three-dimensional coordinate system.

[0055] Specifically, the holographic optical element 800 is rotated around the Y-axis so that the holographic optical element 800 is perpendicular to the XOY plane of the three-dimensional coordinate system.

[0056] For example, such as Figure 6 As shown in (b), the angle of the holographic optical element 800 is adjusted so that the holographic optical element 800 is in a vertical position in the three-dimensional coordinate system. At this time, the holographic optical element 800 is parallel to the YOZ plane. In the holographic optical element 800 fabrication system, the reference beam 901 is perpendicularly irradiated to one side of the holographic optical element 800 along the X-axis direction. The signal beam 902 is at a specific direction and angle with the XOZ plane, YOZ plane and XOY plane, and irradiates the other side of the holographic optical element 800.

[0057] Specifically, when the image source 101 is located in the center of the windshield, the windshield is tilted at an angle of 45°, the angle between the reference beam 901 and the X-axis is 45°, and after the holographic optical element 800 rotates around the Y-axis, the holographic optical element 800 is perpendicular to the XOY plane of the three-dimensional coordinate system, and the first direction vector corresponding to the reference beam 901 is collinear with the X-axis.

[0058] In the prior art, after the holographic optical element 800 is adjusted to a vertical position, the incident direction of the optical path corresponding to the signal beam 902 in the holographic optical element 800 fabrication system simultaneously includes three components: the X-axis, the Y-axis, and the Z-axis. This constitutes a three-dimensional optical path structure, which makes the exposure system complex to build and requires high adjustment precision.

[0059] This invention utilizes coordinate system rotation transformation. Based on the three-dimensional spatial relationship between the incident and diffracted light required by the windshield, the holographic optical element 800 is transformed into a vertical position in three-dimensional space by rotation. Then, the holographic optical element 800 is rotated to transform the incident direction of the original three-dimensional signal beam 902 into the incident direction in a two-dimensional plane. This allows exposure interference to be completed in a two-dimensional plane, transforming the three-dimensional optical path structure into a two-dimensional optical path structure. This reduces the complexity of the fabrication process while ensuring the accuracy of the holographic optical element 800 fabrication.

[0060] S3. Calculate the second direction vector of the reference beam and the signal beam in three-dimensional space based on the first direction vector and the adjustment angle of the vertical position.

[0061] Specifically, calculating the second direction vector of the reference beam and the signal beam in three-dimensional space based on the first direction vector and the adjustment angle of the vertical position includes: The rotation matrix corresponding to the vertical position of the holographic optical element is obtained based on the adjustment angle of the vertical position. The second direction vector of the reference beam and the signal beam in three-dimensional space is calculated based on the rotation matrix and the first direction vector.

[0062] In this embodiment of the invention, the rotation matrix is ​​represented as:

[0063] in, To adjust the angle around the Y-axis, This is the rotation value around the Y-axis.

[0064] For example, such as Figure 6 As shown in (b), when the angle is adjusted to 45°, and the holographic optical element 800 is in a vertical position in the three-dimensional coordinate system, the corresponding normal vector is... The second direction vector corresponding to reference beam 901 The second direction vector corresponding to signal beam 902 After normalization, we get ; .

[0065] Furthermore, when the position of the signal beam 902 is uncertain, a general expression for the rotation angle of the holographic optical element 800 can be obtained based on geometric constraints.

[0066] S4. Adjust the angle of the holographic optical element again according to the second direction vector so that the reference beam and the signal beam are on the same plane.

[0067] Specifically, the holographic optical element 800 is rotated around the Z-axis and X-axis in combination according to the second direction vector, so that the reference beam 901 and the signal beam 902 are located in the XOY plane of the three-dimensional coordinate system.

[0068] For example, such as Figure 6 As shown in (c), via Figure 6 (b) After the adjustment, the second direction vector corresponding to the signal beam 902 is not on the XOY plane. In order to make the three-dimensional structure two-dimensional, the holographic optical element 800 needs to be rotated and adjusted again so that the reference beam 901 and the signal beam 902 are on the XOY plane of the three-dimensional coordinate system, so that the component of the second direction vector corresponding to the signal beam 902 on the Z axis is reduced to 0, that is, the horizontalization of the optical path is realized.

[0069] Specifically, since the first direction vector corresponding to the reference beam 901 is collinear with the X-axis when the holographic optical element 800 is perpendicular to the XOY plane of the three-dimensional coordinate system, the holographic optical element 800 can be directly rotated along the X-axis to adjust the signal beam 902; wherein, the rotation matrix when rotating around the X-axis is expressed as:

[0070] in, To adjust the angle around the X-axis, This is the rotation value around the X-axis.

[0071] For example, such as Figure 6 As shown in (c), the direction vector corresponding to the adjusted signal beam 902 around the X-axis Its weight , , After adjustment Finally, the goal was achieved. ; At this point, the signal beam 902 is only distributed within the XOY plane, thus realizing the two-dimensionalization of the three-dimensional optical path.

[0072] S5. Using the holographic optical element fabrication system, the holographic optical element after the angle is adjusted is exposed and interfered to form a standing wave pattern in the photosensitive material of the holographic optical element.

[0073] In this embodiment of the invention, the reference beam 901 and the signal beam 902 are projected onto both sides of the holographic optical element 800 after the angle is adjusted, according to the design parameters. The holographic optical element 800 after the composite rotation adjustment is installed at an angle in the holographic optical element fabrication system. The holographic optical element 800 has a holographic photosensitive material 802 (such as photoresist). According to the projection of the reference beam 901 and the signal beam 902, they are superimposed in the holographic photosensitive material 802 to form a stable interference field. The bright and dark fringes of the interference field (corresponding to the maximum / minimum of light intensity) cause the photoresist to undergo a photochemical reaction to achieve exposure. If the HOE substrate 801 has high reflectivity (such as silicon wafer or metal film), the superposition of the reference beam 901 and the signal beam 902 will form a standing wave, causing the light intensity to oscillate periodically along the depth direction. After exposure, the unreacted (or reacted) areas are dissolved by the developer, forming periodic microstructures (such as gratings or complex diffraction patterns) on the photoresist surface that correspond to the interference fringes, thus forming a standing wave pattern.

[0074] This invention performs holographic optical element 800 exposure based on the converted two-dimensional exposure geometry, thereby obtaining holographic optical characteristics equivalent to the original three-dimensional design.

[0075] In a practical application scenario of the present invention, the driver's seat and the passenger's seat are respectively used as the focusing areas of the signal beam 902, so as to perform exposure interference on the holographic optical element 800 corresponding to the driver's seat and the holographic optical element 800 corresponding to the passenger's seat, thereby realizing the fabrication of the left and right holographic optical elements 800 in the windshield.

[0076] Example 5 This invention provides a method for fabricating a holographic optical element. Since the positions of both the reference beam 901 and the signal beam 902 are uncertain, this invention utilizes a holographic optical element 800 that is tilted around the Z-axis. pitch angle around the X-axis The combined rotation causes the reference beam 901 and the signal beam 902 to fall on the same plane after rotation, thereby transforming the three-dimensional exposure structure into a two-dimensional exposure structure.

[0077] For example, the direction vector corresponding to reference beam 901 The direction vector corresponding to signal beam 902 The holographic optical element 800 first rotates ψ around the Z-axis, then rotates θ around the X-axis. Its composite rotation matrix is: , .

[0078] The direction vectors of the reference beam 901 and the signal beam 902 after composite rotation satisfy the following: ,

[0079] The core of two-dimensional planarization of the optical path lies in the fact that all components of the Z-axis are 0, that is: ,

[0080] After unfolding, we get:

[0081] The solution yields:

[0082] This composite rotation angle is applicable to any direction of the reference beam 901 and the signal beam 902, and only two rotations are needed to make the reference beam 901 and the signal beam 902 fall on the same horizontal plane (Z=0 plane).

[0083] In the holographic optical element fabrication system, the holographic optical element is tilted according to the calculated rotation angle, so that the original three-dimensional signal beam 902 interferes with the reference beam 901 in the same horizontal plane.

[0084] In summary, in the holographic optical element fabrication method of this invention, the holographic optical element is transformed into a vertical position in three-dimensional space by rotation, and then the holographic optical element is rotated again to transform the incident direction of the signal beam in the original three-dimensional space into the incident direction in a two-dimensional plane, thereby completing the exposure interference in the two-dimensional plane, transforming the three-dimensional optical path structure into a two-dimensional optical path structure. This reduces the complexity of the fabrication process while ensuring the accuracy of the holographic optical element fabrication. The holographic optical element is exposed using the transformed two-dimensional exposure geometry, thereby obtaining holographic optical characteristics equivalent to the three-dimensional design. In the holographic optical element fabrication system, a converging beam is used as the signal beam, so that the field of vision of the driver is not limited by the size of the holographic optical element, thus ensuring the certainty and clarity of the field of vision. In a dual-view head-up display system, a single projector provides the image source. By utilizing the angle selectivity of the scattering holographic optical element, the beam of light to be displayed emitted from the image source is diffracted at different angles by the first and second holographic optical elements and directed to the eyes of the driver and passenger, respectively, so that both the driver and passenger can see the same image with identical color and content.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for fabricating holographic optical elements, applied to a holographic optical element fabrication system, characterized in that, include: Based on the design parameters of the reference beam and the signal beam relative to the holographic optical element, determine the first direction vector of the reference beam and the signal beam in three-dimensional space; Adjust the angle of the holographic optical element so that the holographic optical element is in a vertical position in the three-dimensional coordinate system; The second direction vector of the reference beam and the signal beam in three-dimensional space is calculated based on the first direction vector and the adjustment angle of the vertical position; The angle of the holographic optical element is adjusted again according to the second direction vector so that the reference beam and the signal beam are in the same plane; The holographic optical element fabrication system is used to expose and interfere the holographic optical element after the angle is adjusted, so that the photosensitive material in the holographic optical element forms a standing wave pattern.

2. The method for fabricating a holographic optical element according to claim 1, characterized in that, Adjusting the angle of the holographic optical element to place it in a vertical position in the three-dimensional coordinate system includes rotating the holographic optical element around the Y-axis to make it perpendicular to the XOY plane of the three-dimensional coordinate system.

3. The method for fabricating a holographic optical element according to claim 1, characterized in that, The step of calculating the second direction vector of the reference beam and the signal beam in three-dimensional space based on the first direction vector and the adjustment angle of the vertical position includes: The rotation matrix corresponding to adjusting the holographic optical element to the vertical position is obtained based on the adjustment angle of the vertical position; The second direction vector of the reference beam and the signal beam in three-dimensional space is calculated based on the rotation matrix and the first direction vector.

4. The method for fabricating a holographic optical element according to claim 1, characterized in that, The step of readjusting the angle of the holographic optical element according to the second direction vector so that the reference beam and the signal beam are in the same plane includes: rotating the holographic optical element around the Z-axis and X-axis respectively according to the second direction vector so that the reference beam and the signal beam are in the XOY plane of the three-dimensional coordinate system.

5. A holographic optical element fabrication system, applied to a head-up display system, characterized in that, include: A laser, used to generate a laser beam; A beam-tuning module is positioned along the propagation path of the laser beam to adjust the horizontal and slant of the laser beam to obtain collimated laser light. A beam splitting module is disposed on the propagation path of the collimated laser and is used to split the parallel laser beam of the collimated laser into a collimated reference beam and a collimated signal beam. A beam expander module is disposed on the propagation path of the collimated reference beam and the collimated signal beam, respectively, and is used to amplify the collimated reference beam and the collimated signal beam to obtain an initial reference beam and an initial signal beam. A reference light module is disposed on the propagation path of the initial reference beam and is used to reflect the initial reference beam to one side of the holographic optical element; A signal light module is disposed in the propagation path of the signal beam and is used to reflect the initial signal beam to the other side of the holographic optical element; The holographic optical element is prepared by exposing and interfering the holographic photosensitive material according to the holographic optical element preparation method as described in claim 1 to form a standing wave pattern.

6. The holographic optical element fabrication system according to claim 5, characterized in that, The beam splitting module includes: The first half-wave plate is used to adjust the polarization state of the collimated laser so that the collimated laser can have different splitting ratios when passing through the polarization beam splitter. A polarization beam splitter is used to split the adjusted collimated laser beam to generate a collimated reference beam and a collimated signal beam. The second half-wave plate is disposed on the propagation path of the collimated signal beam to adjust the polarization state of the collimated signal beam so that the collimated reference beam and the collimated signal beam passing through the polarization beam splitter have the same polarization state.

7. The holographic optical element fabrication system according to claim 5, characterized in that, The beam expanding module includes: A microscope objective is used to expand and amplify the collimated reference beam and the collimated signal beam. A pinhole filter is used to filter out stray light in the expanded collimated reference beam and the collimated signal beam. A collimating lens is used to collimate the expanded collimated reference beam and the collimated signal beam to form an initial reference beam and an initial signal beam.

8. The holographic optical element fabrication system according to claim 5, characterized in that, The reference optical module includes: A reflector is used to reflect the aligned initial reference beam, wherein the propagation path of the reflected initial reference beam is perpendicular to one side of the holographic optical element. A lens is used to diverge the reflected initial reference beam to form a reference beam.

9. The holographic optical element fabrication system according to claim 5, characterized in that, The signal optical module includes: A reflector is used to reflect the initial signal beam after alignment processing, wherein the reflected initial signal beam illuminates the other side of the holographic optical element at a preset angle; A lens is vertically positioned in the propagation path of the initial signal beam to converge the initial signal beam; A scattering film is used to scatter the initial signal beam to form a signal beam.

10. A dual-view head-up display system, characterized in that, include: An image source is used to emit the beam of light to be displayed to the holographic combiner; A holographic combiner includes a first holographic optical element and a second holographic optical element, wherein the first holographic optical element is used to diffract the light beam to be displayed into the eyes of the driver's seat user, and the second holographic optical element is used to diffract the light beam to be displayed into the eyes of the passenger's seat user; The first holographic optical element and the second holographic optical element are respectively fabricated using the holographic optical element fabrication system as described in claim 5.

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