Large-field-angle AR-HUD display device based on TFT screen and vehicle

Abstract

The invention provides a large-field-angle AR-HUD display device based on a TFT screen and a vehicle. The display device comprises a TFT (Thin Film Transistor) display screen, a collimating lens group and a double-free-form-surface reflecting mirror, the collimating lens group is fixed on the TFT display screen and is arranged on a light emitting path of the TFT display screen; the double-free-form-surface reflecting mirror comprises a main free-form-surface reflecting mirror used for horizontal view angle expansion and an auxiliary free-form-surface reflecting mirror used for vertical view angle compensation. Light of a two-dimensional image generated by the TFT display screen and subjected to predistortion processing is reflected to a vehicle windshield at a fixed angle through the collimating lens group and the double-free-form-surface reflector in sequence, so that a corresponding virtual image meeting a set virtual image distance is formed on the vehicle windshield. According to the invention, the field angle is enlarged through the double-free-form-surface reflector, and the cost is reduced through predistortion processing.

Description

Technical Field

[0001] The present application relates to the field of intelligent driving display technology, and in particular to a TFT screen-based AR-HUD display device with a large field of view and a vehicle. Background Art

[0002] In the field of AR-HUD (Augmented Reality Head Up Display), DLP projection solutions, TFT single mirror solutions, or laser scanning (LBS) solutions are generally used. However, these mainstream solutions have the following drawbacks:

[0003] (1) DLP projection solution (digital micromirror device): The DLP projection solution uses a DMD chip to generate images through reflection from a micromirror array. However, due to the size limitations of the DMD chip, the optical system is complex and the cost is high.

[0004] (2) TFT single mirror solution: The TFT single mirror solution uses an LCD screen and a single free-form surface mirror. However, the single mirror cannot compensate for the vertical astigmatism caused by the windshield wedge angle (55° to 65°), the vertical field of view is insufficient, and it cannot display multi-layer AR information (such as lane lines and navigation arrows superimposed). It is also unable to correct the meridian / sagittal aberration at the same time, and the vertical optical path expansion is the first. In addition, because the screen size is fixed, increasing the vertical field of view requires a significant increase in the size of the optical components, resulting in volume expansion. At the same time, edge distortion is also relatively serious.

[0005] (3) Laser Scanning (LBS): This solution uses MEMS micromirrors and laser diodes for scanning and imaging. However, sunlight backflow can cause contrast to fall below test standards and fail to meet automotive reliability requirements. This also requires additional filters, increasing costs. Laser coherence can also cause grainy images. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a large field-of-view AR-HUD display device and vehicle based on a TFT screen, so as to solve the technical problems existing in at least one of the solutions in the above-mentioned prior art.

[0007] To achieve the above-mentioned objectives and other related objectives, the first aspect of the present application provides a large field-of-view AR-HUD display device based on a TFT screen, comprising: a TFT display screen and an optical relay structure; wherein the optical relay structure comprises: a collimating lens group and a double free-form surface reflector; the collimating lens group is fixed to the TFT display screen and is arranged on the light output path of the TFT display screen; the double free-form surface reflector comprises a main free-form surface reflector for horizontal viewing angle expansion and a secondary free-form surface reflector for vertical viewing angle compensation; the TFT display screen is used to generate a two-dimensional image after pre-distortion processing, and propagate the divergent light of the image to the collimating lens group; the collimating lens group is used to convert the divergent light of the image into parallel light; the main free-form surface reflector is used to reflect the parallel light to the secondary free-form surface reflector; the secondary free-form surface reflector is used to reflect the light from the main free-form surface reflector to a vehicle windshield at a fixed angle, so as to form a corresponding virtual image on the vehicle windshield that meets the set virtual image distance.

[0008] In some embodiments of the first aspect of the present application, the TFT display screen includes: a light source, a light guide plate, a quantum dot film, and a brightness enhancement film.

[0009] In some embodiments of the first aspect of the present application, the specific method of generating a two-dimensional image after pre-distortion processing includes: performing distortion correction processing and brightness compensation processing on the original two-dimensional image generated by the TFT display screen in sequence to obtain a two-dimensional image after pre-distortion processing.

[0010] In some embodiments of the first aspect of the present application, the distortion correction processing specifically includes: allowing the light of the original two-dimensional image to pass through the optical relay structure to form an original virtual image on the vehicle windshield; dividing the original two-dimensional image to obtain multiple image areas, and calculating the MTF values ​​of the multiple image areas based on the original virtual image; determining the image area to be corrected based on the MTF values ​​of the multiple image areas according to a set MTF threshold; using the constructed transformation matrix and interpolation algorithm to correct the image area to be corrected to obtain a corrected image area, and then obtaining a corrected two-dimensional image.

[0011] In some embodiments of the first aspect of the present application, the brightness compensation processing includes: adjusting the grayscale value of the corrected two-dimensional image according to a pre-constructed edge light decay curve to obtain a two-dimensional image after pre-distortion processing.

[0012] In some embodiments of the first aspect of the present application, the backlight power of the TFT display is adjusted in real time based on the ambient light data acquired in real time.

[0013] In some embodiments of the first aspect of the present application, the device has a base; the TFT screen is mounted off-axis on the base.

[0014] In some embodiments of the first aspect of the present application, the spacing between the primary curved reflector and the secondary curved reflector is a set reflector spacing.

[0015] To achieve the above-mentioned purpose and other related purposes, the second aspect of the present application provides a vehicle, comprising: the large-field-of-view AR-HUD display device based on a TFT screen as described above and a vehicle windshield.

[0016] In some embodiments of the second aspect of the present application, the vehicle windshield is a vehicle wedge-shaped windshield.

[0017] As described above, the TFT screen-based large field-of-view AR-HUD display device and vehicle of the present application have the following beneficial effects:

[0018] The present application expands the field of view angle by using double free-form surface reflectors and reduces the cost by pre-distortion processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shown is a schematic diagram of the optical path of a large-field-of-view AR-HUD display device based on a TFT screen in one embodiment of the present application.

[0020] Figure 2 Shown is a structural schematic diagram of a large field-of-view AR-HUD display device based on a TFT screen in one embodiment of the present application.

[0021] Figure 3 Shown is a structural schematic diagram of a large field-of-view AR-HUD display device based on a TFT screen in another embodiment of the present application. DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present application through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0023] In the embodiments of this application, terms such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art will understand that terms such as "first" and "second" do not limit the quantity or order of execution, and that terms such as "first" and "second" do not necessarily define differences.

[0024] It should be noted that in the embodiments of this application, words such as "exemplary" or "for example" represent examples, illustrations, or descriptions. Any embodiment or design described in this application as "exemplary" or "for example" should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0025] In the embodiments of the present application, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, ab, ac, bc or abc, where a, b, c can be single or multiple.

[0026] To facilitate understanding of the embodiments of the present application, they are first described in detail with reference to the accompanying drawings. Figures 1 to 3 The following is a schematic diagram showing the structure of a TFT-based AR-HUD display device with a large field of view according to an embodiment of the present invention. The TFT-based AR-HUD display device with a large field of view according to this embodiment includes:

[0027] TFT display screen 1 and optical relay structure;

[0028] The optical relay structure includes: a collimating lens group 2 and a double free-form surface reflector; the collimating lens group is fixed to the TFT display screen 1 and is arranged on the light output path of the TFT display screen; the double free-form surface reflector includes a main free-form surface reflector 3 for horizontal viewing angle expansion and a secondary free-form surface reflector 4 for vertical viewing angle compensation;

[0029] The TFT display screen 2 is used to generate a two-dimensional image after pre-distortion processing and transmit the divergent light of the image to the collimating lens group;

[0030] The collimating lens group 2 is used to convert the divergent light of the image into parallel light;

[0031] The main free-form surface reflector 3 is used to reflect parallel light to the secondary free-form surface reflector 4; the secondary free-form surface reflector 4 is used to reflect light from the main free-form surface reflector 3 to the vehicle windshield 5 at a fixed angle, so as to form a corresponding virtual image on the vehicle windshield 5 that meets the set virtual image distance.

[0032] It should be noted that Figure 1 The optical path in is only a schematic. It should be understood that the horizontal field of view (H-FOV) refers to the maximum angle range that the lens or device can capture in the horizontal direction, that is, the angle from the left edge to the right edge of the picture. The vertical field of view (V-FOV) refers to the maximum angle range that the lens can capture in the vertical direction, that is, the angle from the top edge to the bottom edge of the picture. Vertical field of view compensation (Vertical Field of View Compensation) generally refers to compensating for the insufficient vertical field of view (V-FOV), distortion or mismatch caused by device limitations, scene requirements or hardware characteristics through technical adjustments or algorithm optimization, so as to achieve a picture effect that is more in line with actual needs or human eye perception.

[0033] In one embodiment, the incident angle of the vehicle windshield is between 55° and 65°.

[0034] In one embodiment, the TFT display screen includes: a light source, a light guide plate, a quantum dot film, and a brightness enhancement film. It should be understood that the light guide plate (light guide plate) is a product that uses optical-grade acrylic / PC sheets, and prints light guide dots on the bottom surface using laser engraving, V-shaped cross grid engraving, UV screen printing technology, etc., to convert a line light source into a surface light source. The quantum dot film is a special optical film with a wide color gamut made of quantum dots, polymer resins, and optical-grade water and oxygen barrier films as the main raw materials, combined with high-precision coating technology. Brightness Enhancement Film (BEF), also known as prism film, is a new type of high-performance optical film that is mainly used in the backlight module of liquid crystal display (LCD) to improve the overall brightness of the liquid crystal display.

[0035] It should be noted that the quantum dot film (peak brightness 15000cd / m 2 ) and double free-form surface reflectors (asymmetric reflector coating, reflectivity ≥ 95%), achieving a contrast ratio ≥ 5:1 under 100,000 lux ambient light, overcoming the defect of sunlight backflow (contrast ratio < 3:1).

[0036] In order to better illustrate the TFT display screen, a specific embodiment is now provided:

[0037] Embodiment 1: A TFT display screen.

[0038] The light source is an LED array with a 3.5mm pitch and a color temperature of 6500K. The light guide is made of 1.2mm thick PMMA material and has a luminous efficiency of >85%. The quantum dot film uses a CdSe / ZnS core-shell structure, with three alternating layers stacked to achieve a 110% NTSC color gamut. The brightness enhancement film is a 3M BEFIII prism film with a gain factor of 1.8. The TFT display supports the HDR 10 standard and has a pixel response time of less than 5ms. The operating temperature range is ~40°C to 105°C.

[0039] In one embodiment, the collimating lens assembly is a Fresnel lens. The Fresnel lens is made of resin. The collimation angle tolerance is ±0.1°, and the spot uniformity is greater than 90°.

[0040] In one embodiment, the primary free-form surface reflector is an asymmetric surface. Its base material is aluminum alloy 6061, coated with a silicon dioxide protective film. The secondary free-form surface reflector is a composite surface, with a reflectivity greater than 95% (400-700 nm).

[0041] In one embodiment, Figure 3 As shown, when the virtual image distance VID is set to 7.5m, the distance between the main free-form surface reflector and the auxiliary free-form surface reflector (the distance between the center points of the free-form surface reflector and the auxiliary free-form surface reflector, Figure 3 The distance shown by the straight line d in FIG is d=85±0.1 mm. It should be understood that the virtual image distance VID is generally set to 7.5 m to meet the minimum safe projection distance requirement for AR navigation.

[0042] In one embodiment, a specific method for generating a pre-distorted two-dimensional image includes: sequentially performing distortion correction processing and brightness compensation processing on an original two-dimensional image generated by a TFT display screen to obtain a pre-distorted two-dimensional image.

[0043] In one embodiment, the distortion correction process specifically includes: allowing light from the original two-dimensional image to pass through the optical relay structure to form an original virtual image on the vehicle windshield; dividing the original two-dimensional image to obtain multiple image areas, and calculating the MTF values ​​of the multiple image areas based on the original virtual image; determining the image area to be corrected based on the MTF values ​​of the multiple image areas according to a set MTF threshold; and correcting the image area to be corrected using the constructed transformation matrix and interpolation algorithm to obtain a corrected image area, and then obtaining a corrected two-dimensional image.

[0044] Specifically, first, the TFT screen is made to display a calibration plate image (such as a checkerboard image or a dot array image). Then, the calibration plate image generated by the TFT screen is imaged using an optical relay system to obtain an actual virtual image of the calibration plate image, and at the same time, a theoretical virtual image of the calibration plate image is determined. Furthermore, a suitable distortion model is selected according to the distortion type (such as radial distortion or tangential distortion) of the actual imaging of the calibration plate image. It should be understood that the distortion model is generally a transformation matrix. The distortion model can refer to the distortion model in the prior art and will not be described in detail here. Furthermore, based on the actual virtual image and the theoretical virtual image of the calibration plate image, the transformation matrix parameters of the distortion model corresponding to the distortion caused by the optical relay system are calculated.

[0045] Furthermore, the original two-dimensional image displayed on the TFT screen is divided into multiple image regions. The original two-dimensional image is passed through the optical relay structure to form an original virtual image on the vehicle windshield. The MTF (Modulation Transfer Function) value of each image region is calculated according to the following formula 1:

[0046]

[0047] Among them, MTF i is the MTF value of the i-th image area, M i is the modulation degree of the i-th image region, M′ i is the modulation degree of the corresponding area of ​​the i-th image area on the original virtual image.

[0048] It should be understood that the MTF value can objectively represent the transmission capability of the optical relay structure for targets with different spatial frequencies.

[0049] The calculation method of modulation index is shown in Formula 2:

[0050]

[0051] Among them, M represents the modulation degree of the region, I max Indicates the maximum pixel value of the area, I min Represents the minimum pixel value of the area.

[0052] Furthermore, according to a pre-set MTF threshold (for example, the MTF threshold is 0.35 (@30lp / mm)), the image areas in each image area whose MTF values ​​are less than the MTF threshold are screened out, and the screened image areas are determined as areas to be corrected. The inverse matrix of the distortion model is used to calculate the ideal coordinates of each pixel in the corresponding area of ​​the area to be corrected in the original virtual image, and the corrected coordinates of each pixel of the target corrected virtual image corresponding to the area to be corrected are determined in advance according to requirements. A mapping relationship between the ideal coordinates and the corrected coordinates is established. Through an interpolation algorithm (it should be understood that an existing interpolation algorithm can be selected according to requirements, which will not be repeated here), the pixel coordinates of the ideal pixels in the area to be corrected are calculated, and according to the above mapping relationship, the final corrected image area is obtained. All corrected image areas and image areas that do not require correction constitute a corrected two-dimensional image.

[0053] In one embodiment, the brightness compensation process includes: adjusting the grayscale value of the corrected two-dimensional image according to a pre-constructed edge light attenuation curve to obtain a two-dimensional image after pre-distortion processing.

[0054] Specifically, different test points are set on the corrected two-dimensional image, and the actual brightness of each test point is measured based on the full white signal (grayscale signal 255). The attenuation ratio k of each test point is calculated as actual brightness L / center brightness L0. For the original grayscale G at any position, the adjusted grayscale G ′ Need to meet: Where γ is the gamma value of the screen, which can be obtained through gamma correction measurement and is usually taken as 2.2. Then G ′ =G×C. When k=1, C=1; when k<1, C>1, and the grayscale value should not exceed 255.

[0055] In one embodiment, the backlight power of the TFT display is adjusted in real time based on real-time ambient light data. Specifically, the ambient light data is collected by an ambient light sensor (ALS). Historical ambient light data and the corresponding set backlight power can be pre-fitted to obtain a corresponding linear mapping relationship. When the ambient light data changes, the corresponding backlight power is obtained based on this linear mapping relationship to adjust the TFT display.

[0056] In one embodiment, the dashed line distance is corrected based on vehicle speed data collected by GPS and within a set speed range. Specifically, within the set speed range, the device's virtual image satisfies the set virtual image distance. Outside the set speed range, the virtual image distance of the device's virtual image changes. The virtual image distance can be maintained at the set virtual image distance by increasing or decreasing the optical path length.

[0057] In one embodiment, the device includes a base; the TFT screen is installed on the base at a set angle (off-axis installation). Figure 2 As shown, the angle is the angle indicated by arrow A. The angle can be set between 10° and 15°. Off-axis mounting is used to increase the effective luminous flux.

[0058] In one embodiment, the base is made of Invar alloy (thermal expansion coefficient ≤ 1.2×10 -6 / ℃), ensuring stable performance in an environment of -40℃~85℃.

[0059] It should be noted that the existing vertical field of view (V-FOV) is only 3.5°. The present invention improves the vertical field of view (V-FOV) by 42.8% through dual free-form surface reflector design, quantum dot backlight optimization and software pre-distortion compensation algorithm, meeting the requirements of multi-information layer overlay of AR navigation (such as lane departure warning + speed limit sign displayed simultaneously). At the same time, the vertical curvature optimization of the secondary free-form surface reflector reduces the edge distortion rate from 7.8% to 2.5%. The present invention uses a standardized TFT screen instead of a DLP chipset, and through pre-distortion processing, reduces the reflector processing requirements, reduces costs, and increases the possibility of mass production. The present application can be implemented within a volume of 15L. The real-time adjustment of the backlight power makes the virtual image still clear and variable under midday sunlight, and the power consumption is reduced. And the correction of the virtual image distance makes the virtual image distance fluctuate less.

[0060] Similar to the above embodiment, the present invention also provides a vehicle, which includes the above-mentioned TFT screen-based large-field-of-view AR-HUD display device and a vehicle windshield.

[0061] It should be understood that the large field-of-view AR-HUD display device based on a TFT screen has been described in the above embodiments and will not be repeated here.

[0062] In one embodiment, the vehicle windshield is a vehicle wedge-shaped windshield.

[0063] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0064] In summary, the present application provides a large field-of-view AR-HUD display device and vehicle based on a TFT screen. The display device includes: a TFT display screen, a collimating lens group, and a double free-form surface reflector; the collimating lens group is fixed to the TFT display screen and is arranged on the light output path of the TFT display screen; the double free-form surface reflector includes a main free-form surface reflector for horizontal viewing angle expansion and a sub-free-form surface reflector for vertical viewing angle compensation; the light of the two-dimensional image generated by the TFT display screen after pre-distortion processing is reflected in turn by the collimating lens group and the double free-form surface reflector to the vehicle windshield at a fixed angle, so as to form a corresponding virtual image on the vehicle windshield that meets the set virtual image distance. The present application expands the field of view angle through the double free-form surface reflector, and reduces the cost through pre-distortion processing. Therefore, the present application effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0065] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical concepts disclosed in this application shall be covered by the claims of this application.

Claims

1. A large-viewing-angle AR-HUD display device based on a TFT screen, characterized in that: include: TFT display and optical relay structure; The optical relay structure includes: a collimating lens group and a double free-form surface reflector; the collimating lens group is fixed to the TFT display screen and arranged on the light output path of the TFT display screen; the double free-form surface reflector includes a main free-form surface reflector for horizontal viewing angle expansion and a secondary free-form surface reflector for vertical viewing angle compensation; The TFT display screen is used to generate a two-dimensional image after pre-distortion processing, and transmit the divergent light of the image to the collimating lens group; The collimating lens group is used to convert the divergent light of the image into parallel light; The main free-form surface reflector is used to reflect the parallel light to the secondary free-form surface reflector; the secondary free-form surface reflector is used to reflect the light from the main free-form surface reflector to the vehicle windshield at a fixed angle, so as to form a corresponding virtual image on the vehicle windshield that meets the set virtual image distance.

2. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 1, characterized in that: The TFT display screen includes: a light source, a light guide plate, a quantum dot film and a brightness enhancement film.

3. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 1, characterized in that: Specific methods for generating a two-dimensional image after pre-distortion processing include: The original two-dimensional image generated by the TFT display screen is subjected to distortion correction processing and brightness compensation processing in sequence to obtain a two-dimensional image after pre-distortion processing.

4. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 3, characterized in that: Distortion correction processing specifically includes: allowing light of the original two-dimensional image to pass through the optical relay structure to form an original virtual image on the vehicle windshield; Dividing the original two-dimensional image to obtain a plurality of image regions, and calculating MTF values ​​of the plurality of image regions based on the original virtual image; According to the set MTF threshold, based on the MTF values ​​of the multiple image areas, the image area to be corrected is determined; using the constructed transformation matrix and interpolation algorithm, the image area to be corrected is corrected to obtain a corrected image area, and then a corrected two-dimensional image is obtained.

5. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 4, characterized in that: The brightness compensation process includes: adjusting the grayscale value of the corrected two-dimensional image according to a pre-constructed edge light attenuation curve to obtain a two-dimensional image after pre-distortion processing.

6. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 1, characterized in that: Based on the ambient light data acquired in real time, the backlight power of the TFT display screen is adjusted in real time.

7. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 1, characterized in that: The device has a base; the TFT screen is mounted off-axis on the base.

8. The TFT screen-based large-viewing-angle AR-HUD display device according to claim 1, characterized in that: The distance between the primary curved reflector and the secondary curved reflector is a set reflector distance.

9. A vehicle, characterized in that: The vehicle comprises: a TFT screen-based large-field-of-view AR-HUD display device according to any one of claims 1 to 8 and a vehicle windshield.

10. The vehicle according to claim 9, characterized in that The vehicle windshield is a vehicle wedge-shaped windshield.

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