A microdisplay device for a dual-focus HUD system

Abstract

The present invention relates to a micro-display device for a dual-focal-plane HUD system, which solves the problems of halved field of view, limited operating bandwidth, and low color saturation and brightness in existing dual-focal-plane HUD systems. The present invention includes an image display module and a polarization modulation element arranged above the image display module. The polarization modulation element is used to modulate the polarization of display pixels. The effective area of the subwavelength dielectric grating arrangement is equivalent to a 1 / 2 wave plate. The arrangement of the subwavelength dielectric gratings separates the display pixels in an interlaced manner, row by row or column by column, avoiding the problem of halved field of view caused by existing target surface spatial partitioning schemes. In addition, two adjacent subwavelength dielectric gratings convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other. The two spaced subwavelength dielectric gratings are exactly the same, so that the two images are adjusted to mutually orthogonal linear polarization states, and the two images are generated in an interlaced manner.

Description

Technical Field

[0001] The present invention relates to a dual-focal-plane HUD system, and in particular to a micro display device for the dual-focal-plane HUD system. Background Art

[0002] A head-up display (HUD) is an information display technology designed to project key information directly in front of the user's line of sight, thereby reducing the distraction caused by shifting gaze. Initially used in aviation, HUD technology has expanded into the automotive sector in recent years, particularly with the rapid advancement of display and optical technologies. HUD systems with dual-focus displays, in particular, superimpose key information such as navigation paths, speed data, and driver assistance prompts on the actual road environment. This system optimizes information presentation through a layered display of near and far views. The far-view display emphasizes navigation paths and road warnings, enhancing the driver's spatial awareness and ability to plan ahead. The near-view display focuses on key data such as vehicle speed and distance, allowing the driver to quickly access operational information. This dual-focus display mode effectively simplifies the information transmission process, reduces visual interference caused by frequent projection switching, and significantly improves driving safety and user experience.

[0003] As the core display device in dual-focal-plane HUD systems, the Picture Generation Unit (PGU) has become a key research area. Currently, the main approaches for implementing a projected PGU for dual-focal-plane HUD systems include target-plane partitioning, channel multiplexing, and diffraction waveguides.

[0004] The Chinese invention patent with application number CN202210332331.X proposes a target surface partitioned head-up display device. By dividing the PGU into a first and a second projection surface area, each area is loaded with 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.

[0005] The Chinese invention patent application number CN202410101979.5 proposes a HUD display device based on polarization dual channels. It uses an optical metalens that can independently manipulate left-handed and right-handed circularly polarized light and set different focal positions for them. By controlling the polarization state of the projection light source and loading near-view and long-view images, polarization is used as the information transmission channel to achieve the function of dual-focal plane projection imaging.

[0006] The Chinese invention patent application number CN202410657693.5 proposes an in-vehicle HUD device based on a diffraction two-dimensional waveguide. A prism is used as the coupling end of the waveguide to align with the corresponding area of the corresponding PGU. By designing a grating structure on the waveguide surface and utilizing the total reflection mechanism within the waveguide to transmit light, the optical path and pupil position are precisely controlled to achieve light splitting and imaging with different field of view angles and projection focus depths.

[0007] The above technology can realize the simultaneous display of two focal planes on a single PGU image plane, but it has the following shortcomings:

[0008] 1) The target surface partitioning scheme primarily divides the effective display area of a single PGU, which naturally halves the field of view at two imaging distances, affecting the system's ability to support large field of view displays. Furthermore, the target surface partitioning structure places high demands on the optical system's error accuracy, increasing the difficulty and complexity of assembly and adjustment.

[0009] 2) Channel multiplexing schemes can theoretically achieve full-field display, but their operating bandwidth is limited and they can usually only support narrowband operation. They are unable to meet the demand for efficient display within a wide spectral range, limiting the versatility and stability of the system. In addition, the subwavelength periodic structure of its components will produce a strong zero-order image in actual imaging, introducing unnecessary optical noise and reducing the imaging contrast of the projection information.

[0010] 3) Diffractive waveguides can leverage their diffraction properties to achieve wide fields of view and multi-image projection, but they are sensitive to incident angle, causing angular resolution to vary with field of view, thus affecting imaging accuracy at large fields of view. Furthermore, the wavelength dependence of the diffraction effect results in non-uniform light intensity distribution in the system under RGB broadband conditions, resulting in reduced color saturation and brightness uniformity. This non-uniformity can affect the legibility of key information in HUD systems, especially in high-contrast scenes. Summary of the Invention

[0011] The purpose of the present invention is to solve the technical problems of the existing dual-focal plane HUD system, such as halved field of view, limited working bandwidth, low color saturation and brightness, and to provide a micro display device for the dual-focal plane HUD system.

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

[0013] A micro-display device for a dual-focal-plane HUD system, which is special in that:

[0014] It includes an image display module and a polarization modulation element arranged above the image display module;

[0015] 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;

[0016] 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;

[0017] Phase delay of the subwavelength dielectric grating Satisfy the half-wave condition;

[0018] The azimuth angles of two adjacent sub-wavelength dielectric gratings differ by 45°. The two adjacent sub-wavelength dielectric gratings convert the incident light into linear polarization states in two directions, and the two directions are orthogonal to each other. The two separated sub-wavelength dielectric gratings are exactly the same.

[0019] The display pixel array includes a plurality of display pixels, and the plurality of display pixels are divided into N groups. Each group of display pixels corresponds to a sub-wavelength dielectric grating in a vertical direction, and the width of the sub-wavelength dielectric grating 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.

[0020] The electrodes are used to connect to external input signals.

[0021] Furthermore, the sub-wavelength dielectric grating includes a substrate and a plurality of wire gratings uniformly distributed on the substrate along a width direction of the substrate;

[0022] The half-wave condition is:

[0023] ;

[0024] 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.

[0025] Furthermore, the wire grid thickness 377.8nm, width 100nm, period 166nm;

[0026] The wire grid is made of silicon carbide, and the substrate is made of fused quartz.

[0027] Furthermore, the polarization modulation element is fixed on the upper surface of the first linear polarizer by optical bonding or material growth.

[0028] Furthermore, the polarization modulation element is fixed to the upper surface of the first linear polarizer by optical bonding, and the material used for optical bonding is a transparent adhesive material.

[0029] Furthermore, the transparent adhesive material is optical glue.

[0030] Furthermore, the backlight layer is a Lambertian light source.

[0031] Furthermore, the polarization degree of the first linear polarizer is greater than or equal to 99%, and the extinction ratio is greater than or equal to 1000:1;

[0032] The color filter layer selectively transmits light in the wavelength range corresponding to the three primary colors of red, green, and blue. The central wavelength of red light in the color filter layer is 610-640nm, and the peak transmittance is greater than 85%; the central wavelength of green light is 520-550nm, and the peak transmittance is greater than 85%; the central wavelength of blue light is 440-470nm, and the peak transmittance is greater than 85%; the half-width of the color filter layer is less than or equal to 50nm, and the transmission suppression ratio of adjacent channels is greater than 0.1%;

[0033] The electrode is made of transparent conductive material ITO, and its surface resistance is less than 100Ω / m 2 , the inter-electrode voltage is adjustable 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;

[0034] The liquid crystal layer has a response time of 1-10ms, a transmittance of 80%-90%, a thickness of 3-10μm, a viewing angle of 60°-170°, a driving voltage of 2-15V, and a color contrast ratio greater than 1000:1;

[0035] The polarization degree of the second linear polarizer is greater than or equal to 99%, and the extinction ratio is greater than or equal to 1000:1;

[0036] Furthermore, the glass substrate is made of SiO2 and has a thickness of 0.5 mm.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) The present invention provides a micro display device for a dual-focal plane HUD system, which includes an image display module and a polarization modulation element arranged above the image display module. The polarization modulation element includes N sub-wavelength dielectric gratings for polarization modulation of display pixels. The effective area of the sub-wavelength dielectric grating arrangement is equivalent to a 1 / 2 wave plate. The display pixels are separated in an interlaced manner row by row or column by column according to the arrangement of the sub-wavelength dielectric grating, thereby avoiding the problem of halving the field of view caused by the existing target surface partitioning scheme. In addition, by making the phase delay of the sub-wavelength dielectric grating The half-wave condition is met, and the azimuth angles of two adjacent subwavelength dielectric gratings differ by 45°, so that the two adjacent subwavelength dielectric gratings convert the incident light into linear polarization states in two directions, and the two directions are orthogonal to each other. The two spaced subwavelength dielectric gratings are exactly the same, so that the two images are polarization-modulated into mutually orthogonal linear polarization states, and the two images are generated in an interlaced manner, ensuring the independent display of dual-channel images and avoiding spatial crosstalk. The subwavelength dielectric gratings have uniform phase delay performance in the visible light range, can maintain imaging stability in a wide band, and avoid color deviation and imaging fluctuation caused by wavelength dependence. Compared with channel multiplexing and diffraction waveguide solutions, the present invention performs better in brightness, contrast and color uniformity, ensuring high-quality display of dual-channel images.

[0039] (2) The micro-display device for a dual-focal-plane HUD system provided by the present invention has a simple structure. It is not only compatible with existing display technologies, but can also be integrated into existing dual-focal-plane optical systems, simplifying system design and providing an efficient and concise solution for the dual-focal-plane HUD system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic structural diagram of an embodiment of a micro-display device for a dual-focal-plane HUD system according to the present invention;

[0041] Figure 2 A simplified diagram illustrating the functional principles of an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of the structure of a sub-wavelength dielectric grating in an embodiment of the present invention;

[0043] Figure 4 is a broadband phase delay curve diagram of an embodiment of the present invention;

[0044] Figure 5 is a broadband transmittance curve diagram of an embodiment of the present invention;

[0045] Figure 6 Schematic diagram of the azimuth angle of the sub-wavelength dielectric grating according to an embodiment of the present invention;

[0046] Figure 7 Schematic diagram of incident light passing through two adjacent sub-wavelength dielectric gratings in an embodiment of the present invention.

[0047] The following are the descriptions of the reference numerals:

[0048] 1-polarization modulation element, 11-subwavelength dielectric grating, 111-substrate, 112-wire grid; 2-first linear polarizer, 3-glass substrate, 4-color filter layer, 5-electrode, 6-liquid crystal layer, 7-display pixel array, 8-second linear polarizer, 9-backlight layer. DETAILED DESCRIPTION

[0049] The present invention will be further described below with reference to the accompanying drawings and exemplary embodiments.

[0050] Reference Figure 1-Figure 7 A micro display device for a dual-focal plane HUD system of the present invention includes an image display module and a polarization modulation element 1 arranged above the image display module.

[0051] In this embodiment, if Figure 1 As shown, the image display module includes, arranged from top to bottom, a first linear polarizer 2, a glass substrate 3, a color filter layer 4, an electrode 5, a liquid crystal layer 6, a display pixel array 7, a second linear polarizer 8, and a backlight layer 9;

[0052] The polarization modulation element 1 is provided on the upper surface of the first linear polarizer 2. The polarization modulation element 1 can be fixed to the upper surface of the first linear polarizer 2 by optical bonding or material growth. In this embodiment, the polarization modulation element 1 is fixed to the upper surface of the first linear polarizer 2 by optical bonding, and the material used for optical bonding is a transparent adhesive material. In this embodiment, the transparent adhesive material is optical glue.

[0053] The polarization modulation element 1 includes N subwavelength dielectric gratings 11, where N≥2. The N subwavelength dielectric gratings 11 are arranged along the length direction or width direction of the first linear polarizer 2. The working band of the subwavelength dielectric gratings 11 covers the visible light band.

[0054] Phase delay of subwavelength dielectric grating 11 Satisfy the half-wave condition:

[0055] ;

[0056] in, is the working wavelength, is the refractive index difference between the ordinary axis and the extraordinary axis of the subwavelength dielectric grating 11, is the thickness of the wire grating 112 of the sub-wavelength dielectric grating 11;

[0057] like Figure 3 FIG. 1 is a schematic diagram of the structure of the sub-wavelength dielectric grating 11, which includes a substrate 111 and a plurality of wire gratings 112 uniformly distributed on the substrate 111. In this embodiment, the thickness of the wire grating 112 is 377.8nm, width 100nm, period It is 166nm.

[0058] like Figure 6As shown, it is a schematic diagram of the azimuth angle θ. Because 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 grating 112 and the constant axis. In this embodiment, the azimuth angles of two adjacent sub-wavelength dielectric gratings 11 differ by 45°.

[0059] like Figure 7 As shown, two adjacent sub-wavelength dielectric gratings 11 convert the incident light into linear polarization states in two directions, respectively, and the two directions are orthogonal to each other. The two spaced sub-wavelength dielectric gratings 11 are completely identical.

[0060] The display pixel array 7 includes multiple display pixels, which are divided into N groups. Each group of display pixels is arranged vertically corresponding to a subwavelength dielectric grating 11. The width of the subwavelength dielectric grating 11 matches the width of the corresponding display pixel in the group. The multiple display pixels in each group are arranged along the length of the corresponding subwavelength dielectric grating 11. In this way, the width of the subwavelength dielectric grating 11 precisely matches the width of a single display pixel in the image display module, forming a highly registered structure.

[0061] The electrodes 5 are connected to external input signals. The external input signals change the molecules of the liquid crystal layer 6 by controlling the electrodes 5, thereby realizing the distribution of images in each display pixel.

[0062] This embodiment uses the Finite-Difference Time-Domain (FDTD) method, based on subwavelength grating theory, for modeling and simulation. Taking a vertically incident light beam as an example, the FDTD simulation measures the phase delay of a pair of incident light beams with orthogonal polarization states (TE and TM) after passing through the subwavelength dielectric grating 11. Apochromatic design is performed for five wavelengths within a wide wavelength band of 400 nm to 700 nm to achieve a specific, uniform phase delay across the entire visible spectrum. After sampling and selection, the materials for the wire grating 112 and substrate 111 of the subwavelength dielectric grating 11 were ultimately determined to be silicon carbide and fused silica, respectively.

[0063] The broadband phase delay curve of this embodiment is as follows: Figure 4 As shown in the figure, under the conditions of TE and TM polarization state incident light, the phase delay in the visible light range of 450nm-650nm is controlled near π, with an average value of 1.002π and a root mean square error of 3.42×10 -4 The results show that the subwavelength dielectric grating 11 exhibits good broadband phase delay characteristics in the visible light range, can effectively cover the red, green and blue light bands, and meet the design requirements of broadband polarization state modulation in this embodiment. The broadband transmittance curve is as follows Figure 5 As shown in Figure 2, the average transmittance under TE and TM polarization incident light conditions also reaches 80%.

[0064] The backlight layer 9 is a Lambertian light source, which can provide unpolarized light with uniform intensity. The second linear polarizer 8 is used to convert the unpolarized light emitted by the backlight layer 9 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 6 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 5 is used to control the orientation of the liquid crystal molecules in the liquid crystal layer 6 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 inter-electrode voltage has an adjustable range of 0-10V, a response time of less than 10ms, a parasitic capacitance of less than 0.5pF, and an edge light leakage suppression ratio greater than 30dB. The color filter layer 4 selectively transmits light within the wavelength range corresponding to the three primary colors of red, green, and blue. The central wavelength of red light in the color filter layer 4 is 610-640nm, with a peak transmittance greater than 85%; the central wavelength of green light is 520-550nm, with a peak transmittance greater than 85%; and the central wavelength of blue light is 440-470nm, with a peak transmittance greater than 85%. The half-width of the color filter layer 4 is less than or equal to 50nm, and the transmission suppression ratio of adjacent channels is greater than 0.1%. The glass substrate 3 is made of SiO2 and has a thickness of 0.5mm. The polarization degree of the first linear polarizer 2 is greater than or equal to 99%, and the extinction ratio is greater than or equal to 1000:1.

[0065] like Figure 2 The figure shows a simplified schematic diagram of the functional principle of this embodiment. The backlight layer 9 uses a Lambertian light source, providing uniformly intense unpolarized light. After passing through the second linear polarizer 8, it is converted into linearly polarized light. The light then passes through the display pixel array 7 and the liquid crystal layer 6. An external voltage is applied to the liquid crystal layer 6 via the electrode 5 to control the display state of each display pixel, thereby loading the image. The light then passes through the color filter layer 4, the glass substrate 3, and the first linear polarizer 2. At this point, the polarization state of the image is uniformly linearly polarized. According to the arrangement rule of the subwavelength dielectric gratings 11 in the polarization modulation element 1, two adjacent subwavelength dielectric gratings 11 modulate the polarization of the incident light into linear polarization states in two orthogonal directions. At this time, the effective area of the subwavelength dielectric grating 11 arrangement is equivalent to a half-wave plate, and two images will be generated in an interlaced manner, forming a complete display solution.

[0066] 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 micro display device for a dual-focal-plane HUD system, characterized by: It comprises an image display module and a polarization modulation element (1) arranged above the image display module; The image display module comprises, arranged in order from top to bottom, a first linear polarizer (2), a glass substrate (3), a color filter layer (4), an electrode (5), a liquid crystal layer (6), a display pixel array (7), a second linear polarizer (8), and a backlight layer (9); The polarization modulation element (1) is arranged on the upper surface of the first linear polarizer (2), and the polarization modulation element (1) includes N sub-wavelength dielectric gratings (11), and the N sub-wavelength dielectric gratings (11) are arranged along the length direction or the width direction of the first linear polarizer (2), and N is greater than or equal to 2; Phase delay of the subwavelength dielectric grating (11) Satisfy the half-wave condition; The azimuth angles of two adjacent sub-wavelength dielectric gratings (11) differ by 45 degrees, and the two adjacent sub-wavelength dielectric gratings (11) convert incident light into linear polarization states in two directions, and the two directions are orthogonal to each other, and the two spaced sub-wavelength dielectric gratings (11) are completely identical; The display pixel array (7) includes a plurality of display pixels, and the plurality of display pixels are divided into N groups, each group of display pixels is arranged corresponding to a sub-wavelength dielectric grating (11) in the vertical direction, and the width of the sub-wavelength dielectric grating (11) 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 (11); The electrode (5) is used to connect to an external input signal.

2. The micro-display device for a dual-focal-plane HUD system according to claim 1, wherein: The sub-wavelength dielectric grating (11) comprises a substrate (111) and a plurality of wire gratings (112) uniformly distributed on the substrate (111); The half-wave condition is: ； in, is the working wavelength, is the refractive index difference between the ordinary axis and the extraordinary axis of the subwavelength dielectric grating (11), is the thickness of the wire grating (112) of the sub-wavelength dielectric grating (11).

3. The micro-display device for a dual-focal-plane HUD system according to claim 2, wherein: The wire grid (112) has a thickness 377.8nm, width 100nm, period 166nm; The wire grid (112) is made of silicon carbide, and the substrate (111) is made of fused quartz.

4. The micro-display device for a dual-focal-plane HUD system according to claim 3, wherein: The polarization modulation element (1) is fixed on the upper surface of the first linear polarizer (2) by optical bonding or material growth.

5. The micro-display device for a dual-focal-plane HUD system according to claim 4, wherein: The polarization modulation element (1) is fixed on the upper surface of the first linear polarizer (2) by optical bonding, and the material used for optical bonding is a transparent adhesive material.

6. The micro-display device for a dual-focal-plane HUD system according to claim 5, wherein: The transparent adhesive material is optical glue.

7. The micro-display device for a dual-focal-plane HUD system according to claim 6, wherein: The backlight layer (9) is a Lambertian light source.

8. The micro-display device for a dual-focal-plane HUD system according to claim 1, wherein: The polarization degree of the first linear polarizer (2) is greater than or equal to 99%, and the extinction ratio is greater than or equal to 1000:1; The color filter layer (4) selectively transmits light in the wavelength range corresponding to the three primary colors of red, green and blue. The central wavelength of the red light of the color filter layer (4) is 610-640nm, and the peak transmittance is greater than 85%; the central wavelength of the green light is 520-550nm, and the peak transmittance is greater than 85%; the central wavelength of the blue light is 440-470nm, and the peak transmittance is greater than 85%; the half-height width of the color filter layer (4) is less than or equal to 50nm, and the transmission suppression ratio of adjacent channels is greater than 0.1%; The electrode (5) is made of transparent conductive material ITO, and its surface resistance is lower than 100Ω / m 2 , the inter-electrode voltage is adjustable 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 liquid crystal layer (6) has a response time of 1-10 ms, a light transmittance of 80%-90%, a thickness of 3-10 μm, a viewing angle of 60°-170°, a driving voltage of 2-15 V, and a color contrast ratio greater than 1000:1; The polarization degree of the second linear polarizer (8) is greater than or equal to 99%, and the extinction ratio is greater than or equal to 1000:

1.

9. The micro-display device for a dual-focal-plane HUD system according to claim 8, characterized in that: The glass substrate (3) is made of SiO2 and has a thickness of 0.5 mm.

Images