Large field of view, compact dual-focal plane HUD system and imaging method

Abstract

The present invention relates to a large-field-of-view, compact dual-focal-plane HUD system and imaging method, addressing the problems of existing dual-focal-plane HUD systems, such as bulky structure, low imaging quality, and limited field of view. The present invention comprises an image generation module, an optical path module, a windshield, and an eye box. The image generation module generates two mutually orthogonal linear polarization state images, and distributes the far and near focal plane images on the same target surface in a staggered manner of rows or columns of pixels, thereby avoiding halving the field of view due to target surface partitioning and maintaining a large field of view. The optical path module adopts a folding design, making the structure compact and saving space. Images in different polarization states propagate along their respective optical paths and are formed on corresponding focal planes, thereby improving light energy utilization and imaging quality.

Description

Technical Field

[0001] The present invention relates to a HUD system, and in particular to a large-field-of-view, compact dual-focal-plane HUD system and an imaging method. Background Art

[0002] In recent years, with the accelerated development of intelligent vehicles, intelligent driving technology has become a core area of ​​competition and a key focus for companies. As a key component in intelligent driving assistance systems, head-up displays (HUDs) have rapidly developed and become widely used, owing to their unique advantage of projecting important driving information directly into the driver's field of view. Among these, HUD systems capable of dual-focal-plane projection have become a key technical solution for improving information display efficiency and layered presentation. These systems display different levels of information at different focal planes: the near-focal plane displays basic vehicle status, such as fuel consumption and mileage, as well as information about the vehicle's surroundings, ensuring real-time understanding of near-field dynamics. The far-focal plane displays navigation, warnings, interactions, and external information fusion, helping drivers understand long-range road conditions and global dynamics. Multi-depth projection imaging reduces the driver's need to switch their gaze frequently, significantly improving driving safety and convenience. Against the backdrop of rapidly growing demand for intelligent driving, the development of dual-focal-plane HUD systems has become a key technical direction for enhancing the driving experience and safety.

[0003] At present, the technical solutions for realizing dual-focal plane HUD mainly include dual display module type, waveguide branch type and target surface partition type.

[0004] The Chinese invention patent application number 202210423594.1 proposes a head-up display system based on a dual-display module. The system consists of two independent image display modules, which are used to load display images of the far focal plane and the near focal plane respectively. Each display module is equipped with an independent projection light path. The corresponding image is modulated and amplified through its own optical system, and accurately projected to the corresponding focal plane, realizing dual-focal plane projection imaging of far and near scenes.

[0005] Chinese invention patent application number 202211652859.1 proposes a dual-focal-plane head-up display system based on a waveguide splitter. This system uses a diffraction waveguide as a beam splitter. By designing a grating structure on the waveguide surface and utilizing total internal reflection to guide and split light within the waveguide, the system effectively splits the output light from a single optical engine into two beams. These two beams are then amplified and phase-modulated by an optical lens assembly, projected onto two different focal planes, one near and one far, to achieve a dual-focal-plane virtual image display.

[0006] The Chinese invention patent application number 202210305256.8 proposes a head-up display system based on target surface partitioning. The system divides the picture generation unit (PGU) into a first and a second projection surface area. Each area loads image information of different projection depths. Combined with the design of the subsequent optical system, the projection surfaces of different areas are modulated and focused separately. This solution can achieve dual-focus and multi-depth simultaneous imaging on a single target surface.

[0007] The above technologies can all realize HUD systems with multiple display planes, but they also have the following shortcomings:

[0008] 1) The dual-display module solution requires integrating two independent HUD display and projection units and combining them into a single system through optical design. This complex structure not only increases the size and weight of the device, making the overall system larger, but also places higher requirements on the arrangement and calibration of optical components.

[0009] 2) The waveguide splitting scheme uses diffraction properties to achieve multi-image deflection projection, but it is sensitive to the angle of incidence, resulting in angular resolution that varies with the field of view, affecting the imaging quality over a large field of view. In addition, the wavelength dependence of the diffraction effect makes dispersion difficult to control, which can easily lead to reduced color saturation and uneven brightness distribution under broadband white light. At the same time, there is high energy loss during waveguide transmission, which reduces the optical efficiency of the system and affects the final display brightness and imaging quality.

[0010] 3) The target surface partitioning approach divides the effective display area of ​​a single PGU, resulting in inherently limited fields of view for both near and far focal plane imaging, reducing the system's adaptability to large field-of-view displays. Furthermore, this approach places high demands on the precision control of the optical system, increasing the complexity of the assembly process and the difficulty of system integration. Summary of the Invention

[0011] The purpose of the present invention is to solve the technical problems of existing dual-focal-plane HUD systems, such as bulky structure, low imaging quality and limited field of view, and to provide a large-field-of-view, compact dual-focal-plane HUD system and imaging method.

[0012] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0013] A large field of view, compact dual-focal plane HUD system, which is special in that it includes an image generation module, an optical path module, a windshield, and an eye box;

[0014] The optical path module includes a beam splitting element, a first reflecting element, a second reflecting element and a third reflecting element;

[0015] The image generation module is used to connect to an external input signal and generate two mutually orthogonal linear polarization state images according to the external input signal, namely a first linear polarization state image and a second linear polarization state image, both of which propagate along the output light path of the image generation module;

[0016] The beam splitting element is arranged on the outgoing light path of the image generating module, and the first linear polarization state image and the second linear polarization state image propagate along the first outgoing light path and the second outgoing light path respectively after passing through the beam splitting element;

[0017] The first reflecting element is arranged on the first outgoing light path of the beam splitting element, the second reflecting element is arranged on the reflected light path of the first reflecting element, and the third reflecting element is located on the reflected light path of the second reflecting element;

[0018] The third reflecting element is also located on the second outgoing light path of the beam splitting element;

[0019] The windshield is arranged on the reflected light path of the third reflecting element, and the eye box is arranged on the reflected light path of the windshield.

[0020] Furthermore, the image generation module includes an image display module and a polarization modulation element arranged above the image display module;

[0021] The image display module includes a first linear polarizer, a glass substrate, a color filter layer, electrodes, a liquid crystal layer, a display pixel array, a second linear polarizer, and a backlight layer, which are arranged in sequence from top to bottom;

[0022] The polarization modulation element is arranged on the upper surface of the first linear polarizer, and the polarization modulation element includes N sub-wavelength dielectric gratings, and the N sub-wavelength dielectric gratings are arranged along the length direction or the width direction of the first linear polarizer, and N is greater than or equal to 2; the sub-wavelength dielectric grating includes a substrate and a plurality of linear gratings uniformly distributed on the substrate;

[0023] Phase delay of the subwavelength dielectric grating Satisfy the half-wave condition:

[0024] ;

[0025] in, is the working wavelength, is the refractive index difference between the ordinary axis and extraordinary axis of the subwavelength dielectric grating, is the line grating thickness of the subwavelength dielectric grating;

[0026] The azimuth angles of two adjacent subwavelength dielectric gratings differ by 45°. The two adjacent subwavelength dielectric gratings convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, forming a first linear polarization state image and a second linear polarization state image. The two separated subwavelength dielectric gratings are exactly the same.

[0027] The display pixel array includes a plurality of display pixels, the plurality of display pixels being divided into N groups, each group of display pixels being arranged vertically corresponding to a subwavelength dielectric grating, the width of the subwavelength dielectric grating matching the width of the display pixels in the corresponding group, and the plurality of display pixels in each group being arranged along the length direction of the corresponding subwavelength dielectric grating; the electrodes being used to connect to an external input signal;

[0028] The incident surface of the first reflective element is an even aspheric surface with a curvature radius of -500 mm, an aperture of 50 mm × 30 mm, and a material of Mirror;

[0029] The incident surface of the second reflective element is a spherical surface with a curvature radius of -1200 mm, an aperture of 80 mm × 40 mm, and a material of Mirror;

[0030] The incident surface of the third reflective element is an even aspheric surface with a curvature radius of 800 mm, an aperture of 60 mm × 50 mm, and is made of mirror;

[0031] The incident surface of the windshield is an inclined plane with an infinite curvature radius, an aperture of 200 mm × 100 mm, and is made of BK7;

[0032] The incident surface of the eye box is a standard surface with an infinite radius of curvature and an aperture of 100 mm × 50 mm;

[0033] The optical path distance between the first reflecting element and the second reflecting element is 200 mm, the optical path distance between the second reflecting element and the third reflecting element is 300 mm, the optical path distance between the third reflecting element and the windshield is 150 mm, and the optical path distance between the windshield and the eye box is 50 mm.

[0034] At the same time, an imaging method is also provided, which uses the above-mentioned large field of view, compact dual focal plane HUD system, and its special feature is that it includes the following steps:

[0035] S1, an image generation module generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image;

[0036] S2, the first linear polarization state image and the second linear polarization state image enter the beam splitting element and propagate along the first outgoing light path and the second outgoing light path respectively;

[0037] S3, the first outgoing light path passes through the first reflecting element, the second reflecting element, the third reflecting element and the windshield in sequence and then enters the eye box, where the first linear polarization state image is sensed to form a near-focus plane image;

[0038] The second outgoing light path is reflected by the third reflecting element and the windshield in sequence and then enters the eye box, where the second linear polarization state image is sensed to form a far-focus plane image.

[0039] The present invention also provides a large field of view, compact dual-focal plane HUD system, which is special in that it includes an image generation module, an optical path module, a windshield, and an eye box;

[0040] The optical path module includes a beam splitting element, a first reflecting element, a second reflecting element and a third reflecting element;

[0041] The image generation module is used to connect to an external input signal and generate two mutually orthogonal linear polarization state images according to the external input signal, namely a first linear polarization state image and a second linear polarization state image, both of which propagate along the output light path of the image generation module;

[0042] The beam splitting element is arranged on the outgoing light path of the image generating module, and the first linear polarization state image and the second linear polarization state image propagate along the first outgoing light path and the second outgoing light path respectively after passing through the beam splitting element;

[0043] The first reflective element includes a spliced ​​reflector A and a reflector B;

[0044] The second reflective element includes a C reflector and a D reflector that are spliced ​​together;

[0045] The third reflective element includes an E reflector and an F reflector that are spliced ​​together;

[0046] The B reflector is arranged on the first outgoing light path of the beam splitter element, the D reflector is located on the reflected light path of the B reflector, and the F reflector is located on the reflected light path of the D reflector;

[0047] The A reflector is arranged on the second outgoing light path of the beam splitter element, the C reflector is arranged on the reflected light path of the A reflector, and the E reflector is located on the reflected light path of the C reflector;

[0048] The windshield is arranged on the reflection light path of the E reflector and the F reflector;

[0049] The eye box is arranged on the reflected light path of the windshield.

[0050] Furthermore, the image generation module includes an image display module and a polarization modulation element arranged above the image display module;

[0051] The image display module includes a first linear polarizer, a glass substrate, a color filter layer, electrodes, a liquid crystal layer, a display pixel array, a second linear polarizer, and a backlight layer, which are arranged in sequence from top to bottom;

[0052] The polarization modulation element is arranged on the upper surface of the first linear polarizer, and the polarization modulation element includes N sub-wavelength dielectric gratings, and the N sub-wavelength dielectric gratings are arranged along the length direction or the width direction of the first linear polarizer, and N is greater than or equal to 2; the sub-wavelength dielectric grating includes a substrate and a plurality of linear gratings uniformly distributed on the substrate;

[0053] Phase delay of the subwavelength dielectric grating Satisfy the half-wave condition:

[0054] ;

[0055] in, is the working wavelength, is the refractive index difference between the ordinary axis and extraordinary axis of the subwavelength dielectric grating, is the line grating thickness of the subwavelength dielectric grating;

[0056] The azimuth angles of two adjacent subwavelength dielectric gratings differ by 45°. The two adjacent subwavelength dielectric gratings convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, forming a first linear polarization state image and a second linear polarization state image. The two separated subwavelength dielectric gratings are exactly the same.

[0057] The display pixel array includes a plurality of display pixels, the plurality of display pixels being divided into N groups, each group of display pixels being arranged vertically corresponding to a subwavelength dielectric grating, the width of the subwavelength dielectric grating matching the width of the display pixels in the corresponding group, and the plurality of display pixels in each group being arranged along the length direction of the corresponding subwavelength dielectric grating; the electrodes being used to connect to an external input signal;

[0058] The incident surface of the A reflector is a hyperboloid with a curvature radius of -600 mm and an aperture of 70 mm × 50 mm, and is made of Mirror;

[0059] The incident surface of the B reflector is an even aspheric surface with a curvature radius of -450 mm, an aperture of 60 mm × 40 mm, and is made of Mirror;

[0060] The incident surface of the C reflector is an even aspheric surface with a curvature radius of -1000 mm, an aperture of 100 mm × 60 mm, and is made of Mirror;

[0061] The incident surface of the D reflector is a parabola with an infinite curvature radius, an aperture of 90 mm × 50 mm, and is made of Mirror;

[0062] The incident surface of the E-reflector is a parabola with an infinite curvature radius, an aperture of 80 mm × 60 mm, and is made of Mirror;

[0063] The incident surface of the F reflector is a hyperboloid with a curvature radius of 600 mm and an aperture of 70 mm × 60 mm, and is made of Mirror;

[0064] The windshield incident surface is an inclined spherical surface with a curvature radius of 5000mm, an aperture of 220mm×120mm, and is made of BK7;

[0065] The incident surface of the eye box is a standard surface with an infinite radius of curvature and an aperture of 150 mm × 80 mm;

[0066] The optical path distance between the B reflector and the D reflector is 180 mm, the optical path distance between the D reflector and the F reflector is 280 mm, and the optical path distance between the F reflector and the windshield is 200 mm;

[0067] The optical path distance between the A reflector and the C reflector is 250 mm, the optical path distance between the C reflector and the E reflector is 400 mm, and the optical path distance between the E reflector and the windshield is 180 mm;

[0068] The optical path distance between the windshield and the eye box is 60 mm.

[0069] At the same time, the present invention also provides an imaging method, which uses the above-mentioned large field of view, compact dual-focal plane HUD system, and its special feature is that it includes the following steps:

[0070] S1, an image generation module generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image;

[0071] S2, the first linear polarization state image and the second linear polarization state image enter the beam splitting element and propagate along the first outgoing light path and the second outgoing light path respectively;

[0072] S3, the first outgoing light path is reflected by the B reflector, the D reflector, the F reflector, and the windshield in sequence and then enters the eye box, where the first linear polarization state image is sensed to form a near-focus plane image;

[0073] The second outgoing light path is reflected by the A reflector, the C reflector, the E reflector and the windshield in sequence and then enters the eye box, where the second linear polarization state image is sensed to form a far focal plane image.

[0074] At the same time, the present invention also provides a large field of view, compact dual-focal plane HUD system, which is special in that it includes an image generation module, an optical path module, a windshield and an eye box;

[0075] The optical path module includes a first reflecting element, a second reflecting element and a third reflecting element;

[0076] The image generation module is used to connect to an external input signal and generate two mutually orthogonal linear polarization state images according to the external input signal, namely a first linear polarization state image and a second linear polarization state image, both of which propagate along the output light path of the image generation module;

[0077] The third reflective element includes a front reflector and a rear reflector that are stacked;

[0078] The first reflective element is arranged on the outgoing light path of the image generation module;

[0079] The second reflecting element is arranged on the reflected light path of the first reflecting element;

[0080] The third reflecting element is arranged on the reflecting light path of the second reflecting element, the front reflecting mirror reflects the first linear polarization state image and transmits the second linear polarization state image, and the reflected first linear polarization state image propagates along the reflecting light path of the front reflecting mirror, and the rear reflecting mirror reflects the second linear polarization state image transmitted by the front reflecting mirror, and the reflected second linear polarization state image propagates along the reflecting light path of the rear reflecting mirror;

[0081] The windshield is arranged on the reflected light path of the front reflector and the rear reflector, and the eye box is arranged on the reflected light path of the windshield.

[0082] Furthermore, the image generation module includes an image display module and a polarization modulation element arranged above the image display module;

[0083] The image display module includes a first linear polarizer, a glass substrate, a color filter layer, electrodes, a liquid crystal layer, a display pixel array, a second linear polarizer, and a backlight layer, which are arranged in sequence from top to bottom;

[0084] The polarization modulation element is arranged on the upper surface of the first linear polarizer, and the polarization modulation element includes N sub-wavelength dielectric gratings, and the N sub-wavelength dielectric gratings are arranged along the length direction or the width direction of the first linear polarizer, and N is greater than or equal to 2; the sub-wavelength dielectric grating includes a substrate and a plurality of linear gratings uniformly distributed on the substrate;

[0085] Phase delay of the subwavelength dielectric grating Satisfy the half-wave condition:

[0086] ;

[0087] in, is the working wavelength, is the refractive index difference between the ordinary axis and extraordinary axis of the subwavelength dielectric grating, is the line grating thickness of the subwavelength dielectric grating;

[0088] The azimuth angles of two adjacent subwavelength dielectric gratings differ by 45°. The two adjacent subwavelength dielectric gratings convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, forming a first linear polarization state image and a second linear polarization state image. The two separated subwavelength dielectric gratings are exactly the same.

[0089] The display pixel array includes a plurality of display pixels, the plurality of display pixels being divided into N groups, each group of display pixels being arranged vertically corresponding to a subwavelength dielectric grating, the width of the subwavelength dielectric grating matching the width of the display pixels in the corresponding group, and the plurality of display pixels in each group being arranged along the length direction of the corresponding subwavelength dielectric grating; the electrodes being used to connect to an external input signal;

[0090] The incident surface of the first reflective element is an ellipsoidal surface with a curvature radius of -300 mm, an aperture of 50 mm × 30 mm, and a material of Mirror;

[0091] The incident surface of the second reflective element is a high-order aspheric surface with a curvature radius of -900 mm, an aperture of 80 mm × 45 mm, and a material of Mirror;

[0092] The incident surface of the front reflector is an even aspheric surface with a curvature radius of 400 mm, an aperture of 70 mm × 50 mm, and is made of Mirror;

[0093] The incident surface of the rear reflector is an ellipsoidal surface with a curvature radius of 480 mm and an aperture of 65 mm × 55 mm, and is made of Mirror;

[0094] The incident surface of the windshield is a spherical surface with a curvature radius of 2500 mm and an aperture of 200 mm × 100 mm, and is made of quartz glass;

[0095] The incident surface of the eye box is a standard surface with an infinite curvature radius and an aperture of 120 mm×60 mm.

[0096] The optical path distance between the first reflective element and the second reflective element is 150 mm, the optical path distance between the second reflective element and the front reflector is 260 mm, and the optical path distance between the front reflector and the windshield is 140 mm;

[0097] The optical path distance between the second reflective element and the rear reflector is 265 mm, and the optical path distance between the rear reflector and the windshield is 145 mm;

[0098] The optical path distance between the windshield and the eye box is 40 mm.

[0099] At the same time, the present invention also provides an imaging method, which uses the above-mentioned large field of view, compact dual-focal plane HUD system, and its special feature is that it includes the following steps:

[0100] S1, an image generation module generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image;

[0101] S2, the first linear polarization state image and the second linear polarization state image propagate along the outgoing light path of the image generation module, are reflected by the first reflecting element and the second reflecting element in sequence, and then enter the third reflecting element;

[0102] S3, the first linear polarization state image is reflected by the reflection light path of the front reflector to the windshield, and then enters the eye box after being reflected by the windshield, and the first linear polarization state image forms a near-focus plane image at the eye box;

[0103] The second linear polarization state image is transmitted through the front reflector and enters the rear reflector, then is reflected to the windshield through the reflection light path of the rear reflector, and finally is reflected through the windshield into the eye box, where the second linear polarization state image forms a far focal plane image.

[0104] Compared with the prior art, the present invention has the following beneficial effects:

[0105] (1) The present invention provides a large field of view, compact dual-focal plane HUD system that generates two mutually orthogonal linear polarization state images through an image generation module, and distributes the far and near focal plane images in a staggered manner of rows or columns of pixels on the same target surface, thereby avoiding the halving of the field of view caused by target surface partitioning and maintaining a large field of view; the optical path module adopts a folding design, which makes the structure compact and saves space; images of different polarization states propagate along their respective optical paths and are formed on the corresponding focal planes, thereby improving light energy utilization and imaging quality.

[0106] (2) The present invention provides a large-field-of-view, compact dual-focal-plane HUD system that achieves dual-focal-plane projection through a single display device, effectively reducing the system's energy consumption. By converting the single polarization state of the existing display into two orthogonal polarization states through a polarization modulation element, it achieves highly energy-efficient dual-channel optical conversion and image projection. Furthermore, the system's compact structure and optical design make it compatible with existing automotive intelligent driving technology solutions, meeting the requirements for system size, space utilization, and projection performance in automotive application scenarios.

[0107] (3) The optical design of a large-field-of-view, compact dual-focal-plane HUD system provided by the present invention adopts a polarization-selective separation mechanism. By encoding polarization-orthogonal image display, combined with polarization-specific optical elements and optimized optical design, images of different polarization states propagate along independent optical paths and form images at corresponding focal planes, thereby achieving precise projection of near and far focal plane information. This design utilizes polarization specificity to simplify the multi-optical path structure of the dual-focal-plane projection system, reduce complex optical beam splitting components, and improve the compactness and integration of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Figure 1 This is a light path diagram of Example 1 of the large field of view, compact dual-focal plane HUD system of the present invention;

[0109] Figure 2 This is a light path diagram of Example 2 of the large field of view, compact dual-focal plane HUD system of the present invention;

[0110] Figure 3 This is a light path diagram of Example 3 of the large field of view, compact dual-focal plane HUD system of the present invention;

[0111] Figure 4 Schematic diagram of the image generation module in the large field of view, compact dual-focal plane HUD system of the present invention;

[0112] Figure 5 Schematic diagram of the structure of the sub-wavelength dielectric grating in the large field of view, compact dual-focal plane HUD system of the present invention;

[0113] Figure 6 Schematic diagram of the azimuth angle of the sub-wavelength dielectric grating in the large field of view, compact dual-focal plane HUD system of the present invention.

[0114] The following are the descriptions of the reference numerals:

[0115] 1-image generation module, 11-polarization modulation element, 111-subwavelength dielectric grating, 1111-substrate, 1112-wire grid; 12-first linear polarizer, 13-glass substrate, 14-color filter layer, 15-electrode, 16-liquid crystal layer, 17-display pixel array, 18-second linear polarizer, 19-backlight layer;

[0116] 2-beam splitting element, 3-first reflecting element, 31-A reflecting mirror, 32-B reflecting mirror; 4-second reflecting element, 41-C reflecting mirror, 42-D reflecting mirror; 5-third reflecting element, 51-E reflecting mirror, 52-F reflecting mirror, 53-front reflecting mirror, 54-rear reflecting mirror; 6-windshield, 7-eye box, 8-near focal plane image, 9-far focal plane image. DETAILED DESCRIPTION

[0117] The present invention will be further described below with reference to the accompanying drawings and exemplary embodiments.

[0118] Example 1:

[0119] Reference Figure 1 A large-field-of-view, compact dual-focal-plane HUD system of the present invention includes an image generation module 1, an optical path module, a windshield 6, and an eye box 7.

[0120] The image generation module 1 is connected to the external input signal and generates two mutually orthogonal linear polarization state images according to the external input signal, namely the first linear polarization state image and the second linear polarization state image. The structure of the image generation module 1 is as follows Figure 4 As shown, it includes an image display module and a polarization modulation element 11 arranged above the image display module.

[0121] The image display module includes, arranged from top to bottom, a first linear polarizer 12, a glass substrate 13, a color filter layer 14, an electrode 15, a liquid crystal layer 16, a display pixel array 17, a second linear polarizer 18, and a backlight layer 19;

[0122] The polarization modulation element 11 is arranged on the upper surface of the first linear polarizer 12. The polarization modulation element 11 includes N sub-wavelength dielectric gratings 111. The N sub-wavelength dielectric gratings 111 are arranged along the length direction or width direction of the first linear polarizer 12, where N is greater than or equal to 2. The sub-wavelength dielectric grating 111 includes a substrate 1111 and a plurality of wire gratings 1112 uniformly distributed on the substrate 1111. The structure of the sub-wavelength dielectric grating 1111 is as follows: Figure 5 As shown, the thickness of wire grid 1112 377.8nm, width 100nm, period It is 166nm.

[0123] And the phase delay of the sub-wavelength dielectric grating 111 Satisfy the half-wave condition:

[0124] ;

[0125] in, is the working wavelength, is the refractive index difference between the ordinary axis and the extraordinary axis of the subwavelength dielectric grating 111, is the thickness of the wire grating 1112 of the sub-wavelength dielectric grating 111;

[0126] The azimuth angles of two adjacent sub-wavelength dielectric gratings 111 differ by 45°. Figure 6 This is a schematic diagram of the azimuth angle θ. Since the grating itself is a strip, different linear polarization modulation angles can be achieved with different directions. The constant axis is Figure 6 The horizontal direction in the extraordinary axis is Figure 6 In the vertical direction, the azimuth angle θ is the angle between the wire grid 1112 and the constant axis.

[0127] Two adjacent sub-wavelength dielectric gratings 111 convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, forming a first linear polarization state image and a second linear polarization state image. The two spaced sub-wavelength dielectric gratings 111 are identical, and the operating band of the sub-wavelength dielectric gratings 111 covers the visible light band range;

[0128] The display pixel array 17 includes a plurality of display pixels, which are divided into N groups. Each group of display pixels is arranged vertically corresponding to a sub-wavelength dielectric grating 111, and the width of the sub-wavelength dielectric grating 111 matches the width of the display pixels in the corresponding group. The plurality of display pixels in each group are arranged along the length direction of the corresponding sub-wavelength dielectric grating 111.

[0129] The electrodes 15 are connected to external input signals. The external input signals change the molecules of the liquid crystal layer 16 by controlling the electrodes 15 , thereby realizing the distribution of images in each display pixel.

[0130] The backlight layer 19 is a Lambertian light source, which can provide unpolarized light with uniform intensity. The second linear polarizer 18 is used to convert the unpolarized light emitted by the backlight layer 19 into linearly polarized light, with a polarization degree greater than or equal to 99% and an extinction ratio greater than or equal to 1000:1. The response time of the liquid crystal layer 16 is 1-10ms, the transmittance is 80%-90%, the thickness is 3-10μm, the viewing angle is 60°-170°, the driving voltage is 2-15V, and the color contrast is greater than 1000:1. The electrode 15 is used to control the orientation of the liquid crystal molecules in the liquid crystal layer 16 to adjust the polarization state of the transmitted light and realize grayscale and image display. Therefore, a transparent conductive material ITO is used, and its surface resistance is less than 100Ω / m. 2 The voltage between electrodes can be adjusted in the range of 0-10V, the response time is less than 10ms, the parasitic capacitance is less than 0.5pF, and the edge light leakage suppression ratio is higher than 30dB. The color filter layer 14 selectively transmits light in the wavelength range corresponding to the three primary colors of red, green, and blue. The center wavelength of red light in the color filter layer 14 is 610-640nm, and the peak transmittance is greater than 85%; the center wavelength of green light is 520-550nm, and the peak transmittance is greater than 85%; the center wavelength of blue light is 440-470nm, and the peak transmittance is greater than 85%; the half-width of the color filter layer 14 is less than or equal to 50nm, and the transmission suppression ratio of adjacent channels is greater than 0.1%. The glass substrate 13 is made of SiO2 and has a thickness of 0.5mm. The polarization degree of the first linear polarizer 12 is greater than or equal to 99%, and the extinction ratio is greater than or equal to 1000:1.

[0131] The backlight layer 19 uses a Lambertian light source, providing uniformly intense unpolarized light. This light is converted into linearly polarized light after passing through the second linear polarizer 18. The light then passes through the display pixel array 17 and the liquid crystal layer 16. An external voltage is applied to the liquid crystal layer 16 via the electrode 15, controlling the display state of each display pixel and loading the image. The light then passes through the color filter layer 14, the glass substrate 13, and the first linear polarizer 12. At this point, the polarization state of the image is uniformly linearly polarized. Based on the arrangement of the subwavelength dielectric gratings 111 in the polarization modulation element 11, two adjacent subwavelength dielectric gratings 111 modulate the polarization of the incident light into linear polarization states in two orthogonal directions. The effective area of ​​the subwavelength dielectric grating 111 arrangement is equivalent to a half-wave plate, generating two interlaced images to form a complete display solution.

[0132] The optical path module adopts a folded optical path design to ensure compactness, and includes a beam splitting element 2 , a first reflecting element 3 , a second reflecting element 4 and a third reflecting element 5 .

[0133] The beam splitting element 2 is arranged on the outgoing light path of the image generating module 1 , and the first linear polarization state image and the second linear polarization state image propagate along the first outgoing light path and the second outgoing light path respectively after passing through the beam splitting element 2 .

[0134] The first reflecting element 3 is arranged on the first outgoing light path of the beam splitting element 2 , the second reflecting element 4 is arranged on the reflected light path of the first reflecting element 3 , and the third reflecting element 5 is located on the reflected light path of the second reflecting element 4 .

[0135] The third reflecting element 5 is arranged on the second outgoing light path of the beam splitting element 2 , the windshield 6 is arranged on the reflected light path of the third reflecting element 5 , and the eye box 7 is located on the reflected light path of the windshield 6 .

[0136] Among them, the incident surface of the first reflective element 3 is an even-order aspheric surface with a curvature radius of -500mm, an aperture of 50mm×30mm, and a material of Mirror; the incident surface of the second reflective element 4 is a spherical surface with a curvature radius of -1200mm, an aperture of 80mm×40mm, and a material of Mirror; the incident surface of the third reflective element 5 is an even-order aspheric surface with a curvature radius of 800mm, an aperture of 60mm×50mm, and a material of Mirror; the incident surface of the windshield 6 is an inclined plane with an infinite curvature radius, an aperture of 200mm×100mm, and a material of BK7; the incident surface of the eye box 7 is a standard surface with an infinite curvature radius and an aperture of 100mm×50mm.

[0137] The optical path distance between the beam splitting element 2 and the first reflecting element 3 is 100 mm, the optical path distance between the first reflecting element 3 and the second reflecting element 4 is 200 mm, the optical path distance between the third reflecting element 5 and the second reflecting element 4 is 300 mm, the optical path distance between the third reflecting element 5 and the windshield 6 is 150 mm, and the optical path distance between the windshield 6 and the eye box 7 is 50 mm.

[0138] The parameters of each component are shown in Table 1:

[0139] Table 1

[0140]

[0141] The optical path distance corresponding to each row of elements is the optical path distance between it and the next element, defined as Figure 1 The optical path distance propagating to the left is positive, and the optical path distance propagating to the right is negative, so the interval between the first reflecting element 3 and the second reflecting element 4 is -200 mm, and the interval between the second reflecting element 4 and the third reflecting element 5 is 300 mm.

[0142] At the same time, this embodiment also provides an imaging method, using the above-mentioned large field of view, compact dual-focal plane HUD system, including the following steps:

[0143] S1, the image generation module 1 generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image;

[0144] S2, the first linear polarization state image and the second linear polarization state image enter the beam splitting element 2 and propagate along its first outgoing light path and second outgoing light path respectively;

[0145] S3, the first outgoing light path is reflected by the first reflecting element 3, the second reflecting element 4, the third reflecting element 5 and the windshield 6 in sequence and then enters the eye box 7, where the first linear polarization state image is sensed to form a near-focus plane image 8;

[0146] The second outgoing light path is reflected by the third reflective element 5 and the windshield 6 in sequence and then enters the eye box 7 , where the second linear polarization state image is sensed to form a far-focus plane image 9 .

[0147] This embodiment adopts the principle of optical path splitting, and the first linear polarization state image and the second linear polarization state image are guided to different optical paths respectively through the beam splitting element 2, so that they do not share the same path. By controlling the order and number of the two images passing through the reflective elements, combined with the folded optical path structure, differential adjustment of the two optical paths is achieved, and then control of different optical focal lengths is achieved, ensuring that the near-focus plane image 8 and the far-focus plane image 9 are respectively imaged on their corresponding focal planes, ultimately achieving dual-focal plane projection imaging.

[0148] Example 2

[0149] Reference Figure 2 A large-field-of-view, compact dual-focal-plane HUD system of the present invention includes an image generation module 1, an optical path module, a windshield 6, and an eye box 7.

[0150] The structure and function of the image generation module 1 are the same as those in the first embodiment, and will not be repeated here.

[0151] The optical path module includes a beam splitting element 2, a first reflecting element 3, a second reflecting element 4 and a third reflecting element 5. The beam splitting element 2 is arranged on the outgoing optical path of the image generating module 1. The first linear polarization state image and the second linear polarization state image propagate along the first outgoing optical path and the second outgoing optical path respectively after passing through the beam splitting element 2.

[0152] In this embodiment, the first reflecting element 3, the second reflecting element 4 and the third reflecting element 5 are all composed of two different reflecting mirrors spliced ​​together, wherein the first reflecting element 3 includes a spliced ​​A reflecting mirror 31 and a spliced ​​B reflecting mirror 32; the second reflecting element 4 includes a spliced ​​C reflecting mirror 41 and a spliced ​​D reflecting mirror 42; and the third reflecting element 5 includes a spliced ​​E reflecting mirror 51 and an F reflecting mirror 52.

[0153] The B reflector 32 is arranged on the first outgoing light path of the beam splitting element 2, the D reflector 42 is located on the reflected light path of the B reflector 32, and the F reflector 52 is located on the reflected light path of the D reflector 42;

[0154] The A reflector 31 is arranged on the second outgoing light path of the beam splitting element 2, the C reflector 41 is arranged on the reflected light path of the A reflector 31, and the E reflector 51 is located on the reflected light path of the C reflector 41;

[0155] The windshield 6 is disposed on the reflected light path of the E reflector 51 and the F reflector 52 , and the eye box 7 is disposed on the reflected light path of the windshield 6 .

[0156] The incident surface of the A reflector 31 is a hyperboloid with a curvature radius of -600 mm, an aperture of 70 mm × 50 mm, and is made of mirror. The incident surface of the B reflector 32 is an even-order aspheric surface with a curvature radius of -450 mm, an aperture of 60 mm × 40 mm, and is made of mirror. The incident surface of the C reflector 41 is an even-order aspheric surface with a curvature radius of -1000 mm, an aperture of 100 mm × 60 mm, and is made of mirror. The incident surface of the D reflector 42 is a parabola with an infinite curvature radius and an aperture of 90 mm × The incident surface of the E reflector 51 is a parabola with an infinite curvature radius and an aperture of 80mm×60mm, and the material is Mirror; the incident surface of the F reflector 52 is a hyperboloid with a curvature radius of 600mm and an aperture of 70mm×60mm, and the material is Mirror; the incident surface of the windshield 6 is an inclined spherical surface with a curvature radius of 5000mm and an aperture of 220mm×120mm, and the material is BK7; the incident surface of the eye box 7 is a standard surface with an infinite curvature radius and an aperture of 150mm×80mm.

[0157] The optical path distance between the B reflector 32 and the D reflector 42 is 180 mm, the optical path distance between the D reflector 42 and the F reflector 52 is 280 mm, and the optical path distance between the F reflector 52 and the windshield 6 is 200 mm;

[0158] The parameters of each component are shown in Table 2:

[0159] Table 2

[0160]

[0161] The optical path distance between the A reflector 31 and the C reflector 41 is 250 mm, the optical path distance between the C reflector 41 and the E reflector 51 is 400 mm, and the optical path distance between the E reflector 51 and the windshield 6 is 180 mm;

[0162] The optical path distance between the windshield 6 and the eye box 7 is 60 mm.

[0163] The parameters of each component are shown in Table 3:

[0164] Table 3

[0165]

[0166] The positive and negative characters of the optical path distances in Table 2 and Table 3 are the same as those in Example 1, and are defined as Figure 2 The distance of the light path propagating to the left is positive, and the distance of the light path propagating to the right is negative.

[0167] At the same time, this embodiment also provides an imaging method, using the above-mentioned large field of view, compact dual-focal plane HUD system, including the following steps:

[0168] S1, the image generation module 1 generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image;

[0169] S2, the first linear polarization state image and the second linear polarization state image enter the beam splitting element 2 and propagate along its first outgoing light path and second outgoing light path respectively;

[0170] S3, the first outgoing light path is reflected by the B reflector 32, the D reflector 42, the F reflector 52 and the windshield 6 in sequence and enters the eye box 7, where the first linear polarization state image is sensed to form a near-focus plane image 8;

[0171] The second outgoing light path is reflected by the A reflector 31 , the C reflector 41 , the E reflector 51 and the windshield 6 in sequence and then enters the eye box 7 , where the second linear polarization state image is sensed to form a far focal plane image 9 .

[0172] This embodiment utilizes a component partitioning approach, directing the first and second linear polarization state images along separate optical paths via beam splitting element 2. Without changing the order or number of optical paths, the use of two different reflectors within each reflective element achieves optical power differences between the two images as they pass through each reflector in their respective optical paths. By adjusting the reflector characteristics within each optical path, different optical powers are controlled for the two images, resulting in the formation of a near-focus plane image 8 and a far-focus plane image 9 on different focal planes.

[0173] Example 3

[0174] Reference Figure 3 A large-field-of-view, compact dual-focal-plane HUD system of the present invention includes an image generation module 1, an optical path module, a windshield 6, and an eye box 7.

[0175] The structure and function of the image generation module 1 are the same as those in the first embodiment, and will not be repeated here.

[0176] The optical path module is different from the above two embodiments and only includes a first reflecting element 3 , a second reflecting element 4 and a third reflecting element 5 .

[0177] The first reflecting element 3 is arranged on the outgoing light path of the image generating module 1, the second reflecting element 4 is arranged on the reflected light path of the first reflecting element 3, and the third reflecting element 5 is arranged on the reflected light path of the second reflecting element 4. In this embodiment, the third reflecting element 5 includes a front reflecting mirror 53 and a rear reflecting mirror 54 which are stacked. The front reflecting mirror 53 reflects the first linear polarization state image and transmits the second linear polarization state image. The reflected first linear polarization state image propagates along the reflected light path of the front reflecting mirror 53. The rear reflecting mirror 54 reflects the second linear polarization state image transmitted through the front reflecting mirror 53. The reflected second linear polarization state image propagates along the reflected light path of the rear reflecting mirror 54. The windshield 6 is arranged on the reflected light paths of the front reflecting mirror 53 and the rear reflecting mirror 54. The eye box 7 is arranged on the reflected light path of the windshield 6.

[0178] Among them, the incident surface of the first reflecting element 3 is an ellipsoidal surface with a curvature radius of -300mm, an aperture of 50mm×30mm, and a material of Mirror; the incident surface of the second reflecting element 4 is a high-order aspheric surface with a curvature radius of -900mm, an aperture of 85mm×45mm, and a material of Mirror; the incident surface of the front reflecting mirror 53 is an even-order aspheric surface with a curvature radius of 400mm, an aperture of 70mm×50mm, and a material of Mirror; the incident surface of the rear reflecting mirror 54 is an ellipsoidal surface with a curvature radius of 480mm, an aperture of 65mm×55mm, and a material of Mirror; the incident surface of the windshield 6 is a spherical surface with a curvature radius of 2500mm, an aperture of 200mm×100mm, and a material of quartz glass; the incident surface of the eye box 7 is a standard surface with an infinite curvature radius and an aperture of 120mm×60mm.

[0179] The optical path distance between the first reflective element 3 and the second reflective element 4 is 150 mm, the optical path distance between the second reflective element 4 and the front reflector 53 is 260 mm, and the optical path distance between the front reflector 53 and the windshield 6 is 140 mm;

[0180] The optical path distance between the second reflective element 4 and the rear reflector 54 is 265 mm, the optical path distance between the rear reflector 54 and the windshield 6 is 145 mm; and the optical path distance between the windshield 6 and the eye box 7 is 40 mm.

[0181] The parameters of each component are shown in Table 4:

[0182] Table 4

[0183]

[0184] The parameters of each component are shown in Table 5:

[0185] Table 5

[0186]

[0187] The positive and negative values ​​in the optical path distances in Table 4 and Table 5 are the same as those in Example 1, and are defined as Figure 3 The distance of the light path propagating to the left is positive, and the distance of the light path propagating to the right is negative.

[0188] At the same time, this embodiment also provides an imaging method, using the above-mentioned large field of view, compact dual-focal plane HUD system, including the following steps:

[0189] S1, the image generation module 1 generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image;

[0190] S2, the first linear polarization state image and the second linear polarization state image propagate along the outgoing light path of the image generation module 1, are reflected by the first reflecting element 3 and the second reflecting element 4 in sequence, and then enter the third reflecting element 5;

[0191] S3, the first linear polarization state image is reflected by the reflection light path of the front reflector 53 to the windshield 6, and then enters the eye box 7 after being reflected by the windshield 6, and the first linear polarization state image forms a near-focus plane image 8 at the eye box 7;

[0192] The second linear polarization state image is transmitted through the front reflector 53 and enters the rear reflector 54 , and then is reflected to the windshield 6 through the reflection light path of the rear reflector 54 , and finally is reflected through the windshield 6 and enters the eye box 7 , where the second linear polarization state image forms a far focal plane image 9 .

[0193] This embodiment employs optical path multiplexing, employing polarization multiplexing design for the components within the optical path module, resulting in components with different optical powers for light of different polarization states. Without introducing the beam splitter 2, the single-image projection system is modified. Through optical path design and precise adjustment of the reflective elements, the front reflector 53 and the rear reflector 54 are used to independently control the optical powers of the two polarization states of light. This successfully reduces the space occupied by the system, thereby enabling the formation of a near-focal plane image 8 and a far-focal plane image 9 on different focal planes, achieving the technical effect of dual-focal plane imaging.

[0194] The embodiments described above are merely descriptions of specific implementation methods of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A large field of view, compact dual-focal plane HUD system, characterized by: It includes an image generation module (1), an optical path module, a windshield (6), and an eye box (7); The optical path module comprises a beam splitting element (2), a first reflecting element (3), a second reflecting element (4) and a third reflecting element (5); The image generation module (1) is used to connect to an external input signal and generate two mutually orthogonal linear polarization state images according to the external input signal, namely a first linear polarization state image and a second linear polarization state image, both of which propagate along the output light path of the image generation module (1); The beam splitting element (2) is arranged on the outgoing light path of the image generating module (1); the first linear polarization state image and the second linear polarization state image respectively propagate along the first outgoing light path and the second outgoing light path after passing through the beam splitting element (2); The first reflecting element (3) is arranged on a first outgoing light path of the beam splitting element (2), the second reflecting element (4) is arranged on a reflected light path of the first reflecting element (3), and the third reflecting element (5) is located on a reflected light path of the second reflecting element (4); The third reflecting element (5) is simultaneously located on the second outgoing light path of the beam splitting element (2); The windshield (6) is arranged on the reflected light path of the third reflecting element (5), and the eye box (7) is arranged on the reflected light path of the windshield (6); The image generation module (1) comprises an image display module and a polarization modulation element (11) arranged above the image display module; the image display module comprises a first linear polarizer (12); The polarization modulation element (11) is arranged on the upper surface of the first linear polarizer (12), and the polarization modulation element (11) includes N sub-wavelength dielectric gratings (111), and the N sub-wavelength dielectric gratings (111) are arranged along the length direction or the width direction of the first linear polarizer (12), and N is greater than or equal to 2; The azimuth angles of two adjacent sub-wavelength dielectric gratings (111) differ by 45 degrees. The two adjacent sub-wavelength dielectric gratings (111) convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, thereby forming a first linear polarization state image and a second linear polarization state image.

2. The large field of view, compact dual-focal plane HUD system according to claim 1, characterized in that: The image display module comprises a first linear polarizer (12), a glass substrate (13), a color filter layer (14), an electrode (15), a liquid crystal layer (16), a display pixel array (17), a second linear polarizer (18), and a backlight layer (19) which are arranged in sequence from top to bottom; The sub-wavelength dielectric grating (111) comprises a substrate (1111) and a plurality of wire gratings (1112) uniformly distributed on the substrate (1111); Phase delay of the sub-wavelength dielectric grating (111) Satisfy the half-wave condition: Wherein, λ is the operating wavelength, Δn is the difference in refractive index between the ordinary axis and the extraordinary axis of the sub-wavelength dielectric grating (111), and h is the thickness of the wire grating (1112) of the sub-wavelength dielectric grating (111); The two sub-wavelength dielectric gratings (111) are exactly the same; The display pixel array (17) includes a plurality of display pixels, the plurality of display pixels are divided into N groups, each group of display pixels is arranged corresponding to a sub-wavelength dielectric grating (111) in the vertical direction, and the width of the sub-wavelength dielectric grating (111) matches the width of the display pixels corresponding to the group, and the plurality of display pixels in each group are arranged along the length direction of the corresponding sub-wavelength dielectric grating (111); the electrode (15) is used to connect to an external input signal; The incident surface of the first reflective element (3) is an even aspheric surface with a curvature radius of -500 mm and an aperture of 50 mm × 30 mm, and is made of mirror; The incident surface of the second reflective element (4) is a spherical surface with a curvature radius of -1200 mm and an aperture of 80 mm × 40 mm, and is made of mirror; The incident surface of the third reflective element (5) is an even aspheric surface with a curvature radius of 800 mm and an aperture of 60 mm×50 mm, and is made of mirror; The incident surface of the windshield (6) is an inclined plane with an infinite curvature radius, an aperture of 200 mm × 100 mm, and is made of BK7; The incident surface of the eye box (7) is a standard surface with an infinite radius of curvature and an aperture of 100 mm × 50 mm; The optical path distance between the first reflecting element (3) and the second reflecting element (4) is 200 mm, the optical path distance between the second reflecting element (4) and the third reflecting element (5) is 300 mm, the optical path distance between the third reflecting element (5) and the windshield (6) is 150 mm, and the optical path distance between the windshield (6) and the eye box (7) is 50 mm.

3. An imaging method, using a large field of view, compact dual-focal plane HUD system according to any one of claims 1-2, characterized in that: The following steps are involved: S1, an image generation module (1) generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image; S2, the first linear polarization state image and the second linear polarization state image enter the beam splitting element (2) and propagate along the first outgoing light path and the second outgoing light path respectively; S3, the first outgoing light path passes through the first reflecting element (3), the second reflecting element (4), the third reflecting element (5) and the windshield (6) in sequence and then enters the eye box (7), where the first linear polarization state image is sensed to form a near-focus plane image (8); The second outgoing light path is reflected by the third reflecting element (5) and the windshield (6) in sequence and then enters the eye box (7). The second linear polarization state image is sensed at the eye box (7) to form a far-focus plane image (9).

4. A large field of view, compact dual-focal plane HUD system, characterized by: It includes an image generation module (1), an optical path module, a windshield (6), and an eye box (7); The optical path module comprises a beam splitting element (2), a first reflecting element (3), a second reflecting element (4) and a third reflecting element (5); The image generation module (1) is used to connect to an external input signal and generate two mutually orthogonal linear polarization state images according to the external input signal, namely a first linear polarization state image and a second linear polarization state image, both of which propagate along the output light path of the image generation module (1); The beam splitting element (2) is arranged on the outgoing light path of the image generating module (1); the first linear polarization state image and the second linear polarization state image respectively propagate along the first outgoing light path and the second outgoing light path after passing through the beam splitting element (2); The first reflecting element (3) comprises an A reflecting mirror (31) and a B reflecting mirror (32) which are spliced ​​together; The second reflecting element (4) comprises a C reflecting mirror (41) and a D reflecting mirror (42) which are spliced ​​together; The third reflecting element (5) comprises an E reflecting mirror (51) and an F reflecting mirror (52) which are spliced ​​together; The B reflector (32) is arranged on the first outgoing light path of the beam splitting element (2), the D reflector (42) is located on the reflected light path of the B reflector (32), and the F reflector (52) is located on the reflected light path of the D reflector (42); The A reflector (31) is arranged on the second outgoing light path of the beam splitting element (2), the C reflector (41) is arranged on the reflected light path of the A reflector (31), and the E reflector (51) is located on the reflected light path of the C reflector (41); The windshield (6) is arranged on the reflection light path of the E reflector (51) and the F reflector (52); The eye box (7) is arranged on the reflected light path of the windshield (6); The image generation module (1) comprises an image display module and a polarization modulation element (11) arranged above the image display module; the image display module comprises a first linear polarizer (12); The polarization modulation element (11) is arranged on the upper surface of the first linear polarizer (12), and the polarization modulation element (11) includes N sub-wavelength dielectric gratings (111), and the N sub-wavelength dielectric gratings (111) are arranged along the length direction or the width direction of the first linear polarizer (12), and N is greater than or equal to 2; The azimuth angles of two adjacent sub-wavelength dielectric gratings (111) differ by 45 degrees. The two adjacent sub-wavelength dielectric gratings (111) convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, thereby forming a first linear polarization state image and a second linear polarization state image.

5. The large field of view, compact dual-focal plane HUD system according to claim 4, characterized in that: The image display module comprises a first linear polarizer (12), a glass substrate (13), a color filter layer (14), an electrode (15), a liquid crystal layer (16), a display pixel array (17), a second linear polarizer (18), and a backlight layer (19) which are arranged in sequence from top to bottom; The sub-wavelength dielectric grating (111) comprises a substrate (1111) and a plurality of wire gratings (1112) uniformly distributed on the substrate (1111); Phase delay of the sub-wavelength dielectric grating (111) Satisfy the half-wave condition: Wherein, λ is the operating wavelength, Δn is the difference in refractive index between the ordinary axis and the extraordinary axis of the sub-wavelength dielectric grating (111), and h is the thickness of the wire grating (1112) of the sub-wavelength dielectric grating (111); The two sub-wavelength dielectric gratings (111) are exactly the same; The display pixel array (17) includes a plurality of display pixels, the plurality of display pixels are divided into N groups, each group of display pixels is arranged corresponding to a sub-wavelength dielectric grating (111) in the vertical direction, and the width of the sub-wavelength dielectric grating (111) matches the width of the display pixels corresponding to the group, and the plurality of display pixels in each group are arranged along the length direction of the corresponding sub-wavelength dielectric grating (111); the electrode (15) is used to connect to an external input signal; The incident surface of the A reflector (31) is a hyperboloid, with a curvature radius of -600 mm, an aperture of 70 mm × 50 mm, and is made of Mirror; The incident surface of the B reflector (32) is an even aspheric surface with a curvature radius of -450 mm and an aperture of 60 mm×40 mm, and is made of Mirror; The incident surface of the C reflector (41) is an even aspheric surface with a curvature radius of -1000 mm and an aperture of 100 mm×60 mm, and is made of Mirror; The incident surface of the D reflector (42) is a parabola, the curvature radius is infinite, the aperture is 90mm×50mm, and the material is Mirror; The incident surface of the E reflector (51) is a parabola with an infinite curvature radius and an aperture of 80 mm × 60 mm, and is made of Mirror; The incident surface of the F reflector (52) is a hyperboloid, with a curvature radius of 600 mm, an aperture of 70 mm×60 mm, and is made of Mirror; The incident surface of the windshield (6) is an inclined spherical surface with a curvature radius of 5000 mm, an aperture of 220 mm × 120 mm, and a material of BK7; The incident surface of the eye box (7) is a standard surface with an infinite curvature radius and an aperture of 150 mm × 80 mm; The optical path distance between the B reflector (32) and the D reflector (42) is 180 mm, the optical path distance between the D reflector (42) and the F reflector (52) is 280 mm, and the optical path distance between the F reflector (52) and the windshield (6) is 200 mm; The optical path distance between the A reflector (31) and the C reflector (41) is 250 mm, the optical path distance between the C reflector (41) and the E reflector (51) is 400 mm, and the optical path distance between the E reflector (51) and the windshield (6) is 180 mm; The optical path distance between the windshield (6) and the eye box (7) is 60 mm.

6. An imaging method, using a large field of view, compact dual-focal plane HUD system according to any one of claims 4-5, characterized in that: The following steps are involved: S1, an image generation module (1) generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image; S2, the first linear polarization state image and the second linear polarization state image enter the beam splitting element (2) and propagate along the first outgoing light path and the second outgoing light path respectively; S3, the first outgoing light path is reflected by the B reflector (32), the D reflector (42), the F reflector (52) and the windshield (6) in sequence and then enters the eye box (7), where the first linear polarization state image is sensed to form a near-focus plane image (8); The second outgoing light path is reflected by the A reflector (31), the C reflector (41), the E reflector (51) and the windshield (6) in sequence and then enters the eye box (7). A second linear polarization state image is sensed at the eye box (7) to form a far-focus plane image (9).

7. A large field of view, compact dual-focal plane HUD system, characterized by: It includes an image generation module (1), an optical path module, a windshield (6), and an eye box (7); The optical path module comprises a first reflecting element (3), a second reflecting element (4) and a third reflecting element (5); The image generation module (1) is used to connect to an external input signal and generate two mutually orthogonal linear polarization state images according to the external input signal, namely a first linear polarization state image and a second linear polarization state image, both of which propagate along the output light path of the image generation module (1); The third reflecting element (5) comprises a front reflecting mirror (53) and a rear reflecting mirror (54) which are stacked; The first reflecting element (3) is arranged on the outgoing light path of the image generating module (1); The second reflecting element (4) is arranged on the reflecting light path of the first reflecting element (3); The third reflecting element (5) is arranged on the reflection light path of the second reflecting element (4); the front reflecting mirror (53) reflects the first linear polarization state image and transmits the second linear polarization state image, and the reflected first linear polarization state image propagates along the reflection light path of the front reflecting mirror (53); the rear reflecting mirror (54) reflects the second linear polarization state image transmitted by the front reflecting mirror (53), and the reflected second linear polarization state image propagates along the reflection light path of the rear reflecting mirror (54); The windshield (6) is arranged on the reflected light path of the front reflector (53) and the rear reflector (54), and the eye box (7) is arranged on the reflected light path of the windshield (6); The image generation module (1) comprises an image display module and a polarization modulation element (11) arranged above the image display module; the image display module comprises a first linear polarizer (12); The polarization modulation element (11) is arranged on the upper surface of the first linear polarizer (12), and the polarization modulation element (11) includes N sub-wavelength dielectric gratings (111), and the N sub-wavelength dielectric gratings (111) are arranged along the length direction or the width direction of the first linear polarizer (12), and N is greater than or equal to 2; The azimuth angles of two adjacent sub-wavelength dielectric gratings (111) differ by 45 degrees. The two adjacent sub-wavelength dielectric gratings (111) convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, thereby forming a first linear polarization state image and a second linear polarization state image.

8. The large field of view, compact dual-focal plane HUD system according to claim 7, characterized in that: The image display module comprises a first linear polarizer (12), a glass substrate (13), a color filter layer (14), an electrode (15), a liquid crystal layer (16), a display pixel array (17), a second linear polarizer (18), and a backlight layer (19) which are arranged in sequence from top to bottom; The sub-wavelength dielectric grating (111) comprises a substrate (1111) and a plurality of wire gratings (1112) uniformly distributed on the substrate (1111); Phase delay of the sub-wavelength dielectric grating (111) Satisfy the half-wave condition: Wherein, λ is the operating wavelength, Δn is the difference in refractive index between the ordinary axis and the extraordinary axis of the sub-wavelength dielectric grating (111), and h is the thickness of the wire grating (1112) of the sub-wavelength dielectric grating (111); The two sub-wavelength dielectric gratings (111) are exactly the same; The display pixel array (17) includes a plurality of display pixels, the plurality of display pixels are divided into N groups, each group of display pixels is arranged corresponding to a sub-wavelength dielectric grating (111) in the vertical direction, and the width of the sub-wavelength dielectric grating (111) matches the width of the display pixels corresponding to the group, and the plurality of display pixels in each group are arranged along the length direction of the corresponding sub-wavelength dielectric grating (111); the electrode (15) is used to connect to an external input signal; The incident surface of the first reflective element (3) is an ellipsoidal surface with a curvature radius of -300 mm and an aperture of 50 mm × 30 mm, and is made of mirror; The incident surface of the second reflective element (4) is a high-order aspheric surface with a curvature radius of -900 mm and an aperture of 80 mm × 45 mm, and is made of mirror; The incident surface of the front reflector (53) is an even aspheric surface with a curvature radius of 400 mm and an aperture of 70 mm×50 mm, and is made of Mirror; The incident surface of the rear reflector (54) is an ellipsoidal surface with a curvature radius of 480 mm and an aperture of 65 mm×55 mm, and is made of Mirror; The incident surface of the windshield (6) is a spherical surface with a curvature radius of 2500 mm and an aperture of 200 mm×100 mm, and is made of quartz glass; The incident surface of the eye box (7) is a standard surface with an infinite curvature radius and an aperture of 120 mm × 60 mm; The optical path distance between the first reflecting element (3) and the second reflecting element (4) is 150 mm, the optical path distance between the second reflecting element (4) and the front reflecting mirror (53) is 260 mm, and the optical path distance between the front reflecting mirror (53) and the windshield (6) is 140 mm; The optical path distance between the second reflective element (4) and the rear reflector (54) is 265 mm, and the optical path distance between the rear reflector (54) and the windshield (6) is 145 mm; The optical path distance between the windshield (6) and the eye box (7) is 40 mm.

9. An imaging method, using a large field of view, compact dual-focal plane HUD system according to any one of claims 7-8, characterized in that: The following steps are involved: S1, an image generation module (1) generates two mutually orthogonal linear polarization state images according to an external input signal, namely a first linear polarization state image and a second linear polarization state image; S2, the first linear polarization state image and the second linear polarization state image propagate along the outgoing light path of the image generation module (1), are reflected by the first reflecting element (3) and the second reflecting element (4) in sequence, and then enter the third reflecting element (5); S3, the first linear polarization state image is reflected by the front reflector (53) to the windshield (6), and then enters the eye box (7) after being reflected by the windshield (6), and the first linear polarization state image forms a near-focus plane image (8) at the eye box (7); The second linear polarization state image is transmitted through the front reflector (53) and enters the rear reflector (54), is then reflected by the rear reflector (54) to the windshield (6), and finally is reflected by the windshield (6) to enter the eye box (7), where the second linear polarization state image forms a far-focus plane image (9) at the eye box (7).

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