Vehicle-mounted HUD system using folded light path
By employing a folded optical path design in the HUD system, combining a polarizer and a quarter-wave plate to adjust the polarization state of the light, the problem of excessively large size of the HUD system is solved, enabling installation and efficient imaging in a limited space.
Patent Information
- Application Number
- CN202423115761.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-17
- Publication Date
- 2025-11-04
- Estimated Expiration
- 2034-12-17
AI Technical Summary
Existing HUD systems are bulky and cannot be installed in vehicles with limited space. Furthermore, traditional optical path designs result in low space utilization and limited applicability.
The design employs a folded optical path, combining a polarizer and a quarter-wave plate to adjust the polarization state of light in the optical path. This allows the polarizer to be placed inside the optical path, reducing the space requirements for optical components.
This system achieves a reduction in size while maintaining image quality, improving space utilization, and making it suitable for more vehicle models.
Smart Images
Figure CN223513401U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of vehicle HUD technology, and in particular to a vehicle HUD system using a folded optical path. Background Technology
[0002] In recent years, private cars have gradually become an essential asset for every family, resulting in a huge market. To enhance their competitiveness and gain a larger market share, automakers are focusing on intelligent driving, using technology to simplify user operations and improve the user experience. Head-up display (HUD) systems, as a crucial component of intelligent driving systems, project vehicle status, map navigation, and other information onto the driver's eyes through the windshield. Drivers can obtain the necessary information without looking down at the instrument panel or displays while driving, significantly reducing safety hazards.
[0003] To display more information and better integrate the HUD image with the environment, a large projection screen and a sufficiently long projection distance are typically required. These factors increase the size of the curved lenses and image source used in the HUD, resulting in a larger overall size. The area in front of the driver usually contains unavoidable structures such as the steering column system and braking system, and the interior space of the vehicle is limited. If the HUD is too large, it cannot be installed inside the car. This restricts the application of HUDs; therefore, HUD systems still need further improvement to reduce their overall size and enhance their applicability.
[0004] The off-axis three-reflector optical path commonly used in current HUD systems needs to avoid interference between the optical lenses and other structural components and the optical path system, which could obstruct the image. This requires sufficient space clearance between the components, resulting in low space utilization and a relatively large overall size of the HUD. This makes it unsuitable for vehicles with limited available space, limiting its applicability. Utility Model Content
[0005] The main objective of this invention is to propose an in-vehicle HUD system that uses a folded optical path, aiming to reduce the overall size while ensuring the imaging quality of the HUD.
[0006] To achieve the above objectives, this utility model proposes an in-vehicle HUD system using a folded optical path, comprising: an image source, a polarizer, a reflector, a first quarter-wave plate, a second quarter-wave plate, and a windshield;
[0007] The polarizing mirror is located between the image source and the windshield, the first quarter-wave plate is disposed in front of the image source, and the second quarter-wave plate is disposed in front of the polarizing mirror;
[0008] The S-polarized or P-polarized light emitted from the image source passes through the first quarter-wave plate and the second quarter-wave plate, and after being delayed by one-quarter of a phase twice, its polarization state becomes P-polarized or S-polarized light, which is reflected at the polarizing mirror. After passing through the second quarter-wave plate, the P-polarized or S-polarized light is converted into circularly polarized light, which is reflected at the reflecting mirror, with the polarization state unchanged and the phase reversed. After passing through the second quarter-wave plate again, it is converted into S-polarized or P-polarized light, and then passes through the polarizing mirror, is reflected by the windshield and enters the human eye, forming a virtual image that can be observed by the human eye.
[0009] A further technical solution of this utility model is that the image source is any one of a TFT system, a DLP system, or an LCOS system.
[0010] A further technical solution of this utility model is that when the image source emits S-polarized light, the polarizing mirror is a polarizing mirror that reflects P-polarized light and transmits S-polarized light; when the image source emits P-polarized light, the polarizing mirror is a polarizing mirror that reflects S-polarized light and transmits P-polarized light.
[0011] A further technical solution of this utility model is that the polarizing mirror and the second quarter-wave plate are partially or completely disposed inside the optical path.
[0012] A further technical solution of this utility model is that the reflector is one of a spherical mirror, an aspherical mirror, or a freeform surface reflector.
[0013] A further technical solution of this utility model is that a polarizing reflective film is provided in front of the windshield.
[0014] The beneficial effects of this invention's vehicle-mounted HUD system using a folded optical path are:
[0015] The optical system of this invention employs a folded optical path design. One of the mirrors in a traditional off-axis three-reflection system is replaced with a polarizer. This mirror can reflect and transmit light with different polarization states. A quarter-wave plate is then added to the optical path system, causing the light to continuously adjust its polarization state during propagation. This allows the light to be reflected or transmitted appropriately as needed when reaching the polarizer multiple times, ensuring the normal operation of the optical path system without introducing stray light. Through the combination of the quarter-wave plate and the polarizer, the polarizer, which would normally need to be placed outside the optical path for adjustment, can be placed inside, reducing the overall size of the optical path through folding. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of a preferred embodiment of the vehicle-mounted HUD system using a folded optical path according to this utility model.
[0018] Explanation of icon numbers:
[0019] Image source 1; polarizer 2; mirror 3; first quarter-wave plate 4; second quarter-wave plate 5; windshield 6.
[0020] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0022] To ensure that the overall size is reduced while maintaining HUD imaging quality, this invention proposes an in-vehicle HUD system using a folded optical path.
[0023] Please refer to Figure 1 A preferred embodiment of the vehicle-mounted HUD system using a folded optical path includes an image source 1, a polarizer 2, a reflector 3, a first quarter-wave plate 4, a second quarter-wave plate 5, and a windshield 6.
[0024] The polarizer 2 is located between the image source 1 and the windshield 6. The first quarter-wave plate 4 is located in front of the image source 1, and the second quarter-wave plate 5 is located in front of the polarizer 2.
[0025] The S-polarized light or P-polarized light emitted from image source 1 passes through the first quarter-wave plate 4 and the second quarter-wave plate 5, and after being delayed by one-quarter of a phase twice, the polarization state becomes P-polarized light or S-polarized light, which is reflected at polarizing mirror 2. After passing through the second quarter-wave plate 5, the P-polarized light or S-polarized light is converted into circularly polarized light, which is reflected at reflecting mirror 3, with the polarization state unchanged and the phase reversed. After passing through the second quarter-wave plate 5 again, it is converted into S-polarized light or P-polarized light, and then passes through polarizing mirror 2, is reflected by windshield 6 and enters the human eye, forming a virtual image that can be observed by the human eye.
[0026] In this embodiment, image source 1 can be any one of a TFT system, a DLP system, or an LCOS system. The light emitted by image source 1 is typically S-polarized light, but P-polarized light image source 1 can also be used depending on actual needs.
[0027] In this embodiment, when the image source 1 emits S-polarized light, the polarizer 2 is a polarizer 2 that reflects P-polarized light and transmits S-polarized light; when the image source 1 emits P-polarized light, the polarizer 2 is a polarizer 2 that reflects S-polarized light and transmits P-polarized light.
[0028] In this embodiment, the first quarter-wave plate 4 and the second quarter-wave plate 5 need to ensure the same phase delay for light rays with a wide range of incident angles. The first quarter-wave plate 4 and the second quarter-wave plate 5 are respectively disposed in front of the image source 1 and the polarizer 2, and need to cover the usage range of the image source 1 and the polarizer 2.
[0029] In this embodiment, the polarizer 2 and the second quarter-wave plate 5 are partially or completely disposed inside the optical path.
[0030] In this embodiment, the reflector 3 is one of a spherical mirror, an aspherical mirror, or a freeform surface reflector 3.
[0031] It should be noted that, in order to ensure other performance and adapt to environmental configuration adjustments of the optical path, a third lens may be added in this embodiment.
[0032] The following combination Figure 1 The structure and working principle of the vehicle-mounted HUD system using a folded optical path according to this utility model are further described in detail.
[0033] like Figure 1 As shown, the folded optical path HUD optical engine system provided in this embodiment includes an image source 1, a polarizer 2, a reflector 3, a first quarter-wave plate 4, a second quarter-wave plate 5, and a windshield 6.
[0034] Image source 1 can be any type of image display system, such as TFT, LCOS, or DLP. These systems contain polarizers, and the light they emit is linearly polarized. The incident and exit angles of light from a HUD system at the windshield are typically greater than 60°. At this angle, the windshield exhibits a significant difference in reflectivity for S-polarized and P-polarized light, with S-polarized light showing greater reflectivity and higher energy efficiency. Therefore, the light emitted by image source 1 is typically S-polarized, and this embodiment will be explained accordingly. It should be noted that since a polarizing reflective film can be added to the windshield to increase the reflectivity of the corresponding linearly polarized light, the type of linearly polarized light emitted by the image source is not limited.
[0035] When the S-polarized light emitted from image source 1 passes through the first quarter-wave plate 4, its polarization state changes. Ideally, the light is incident perpendicularly to the first quarter-wave plate 4, and the angle between the principal axis of the first quarter-wave plate 4 and the S-polarized light is 45°, causing a quarter-wavelength phase delay in the light, converting it from S-polarized light to circularly polarized light (left-handed or right-handed circularly polarized light). If the light is not incident perpendicularly to the first quarter-wave plate 4, the phase delay value will deviate to a certain extent, causing the S-polarized light to convert to elliptically polarized light. Therefore, the first quarter-wave plate 4 should have good performance to ensure that the incident light produces the same phase delay within a certain incident angle range.
[0036] The circularly polarized light continues to propagate, passing through the second quarter-wave plate 5, where its phase is delayed a second time by a quarter wavelength. These two phase delays together delay the light's phase by half a wavelength, transforming the light from S-polarized light initially emitted from image source 1 into P-polarized light.
[0037] Polarizer 2 is a polarizing lens that transmits S-polarized light and reflects P-polarized light. P-polarized light is reflected after reaching polarizer 2. If the performance of the first quarter-wave plate 4 and the second quarter-wave plate 5 is mediocre, and the consistency of the phase delay produced by the incident light within a certain range of incident angles cannot be guaranteed, the P-polarized light at this point will not be purely P-polarized light, but will also contain a very small amount of S-polarized light component. This may become stray light after passing through polarizer 2, affecting the final imaging effect. Furthermore, the larger the incident angle, the greater the phase delay deviation, which will also lead to a certain loss of light during final imaging, resulting in reduced image brightness and uneven brightness.
[0038] The P-linearly polarized light, after being reflected by polarizer 2, passes through the second quarter-wave plate 5 for the second time. The phase of the light is delayed by a quarter wavelength, and it is converted into circularly polarized light (left-handed or right-handed circularly polarized light).
[0039] When circularly polarized light is reflected by mirror 3, its polarization state remains unchanged, but the phase of the light rays is reversed. If the incident light is left-handed circularly polarized, the outgoing light will be right-handed circularly polarized. If the incident light is right-handed circularly polarized, the outgoing light will be left-handed circularly polarized.
[0040] The new circularly polarized light reflected by mirror 3 passes through the second quarter-wave plate 5 for the third time, and the phase of the light is delayed by a quarter wavelength, and the light is converted into S-polarized light.
[0041] At this time, the S-polarized light can pass normally through the first polarizer 2, which transmits the S-polarized light and reflects the P-polarized light, and then be reflected by the windshield 6 into the human eye, forming a virtual image that can be observed by the human eye.
[0042] Traditional HUDs typically use an off-axis three-reflection system, consisting of a first mirror, a second mirror, and a windshield. The first and second mirrors are usually opaque; to avoid interference between the mirrors and the light path and to prevent light obstruction, they need to be positioned outside the light path. Reducing the size of the HUD system also requires minimizing the spacing between the components to achieve even a small reduction in size.
[0043] Since the optical path is reversible, once the positions of the human eye and windshield 6 are determined, and the required viewing angle is set, the optical path from the human eye to the reflector 3 is essentially fixed, with limited adjustment range. Therefore, this invention adjusts the reflector to a polarizing mirror 2, increasing its light-transmitting property, allowing a lens that originally needed to be placed outside the light path to be placed within it, achieving a significant reduction in volume through optical path folding. Simultaneously, a quarter-wave plate is introduced into the optical path, repeatedly changing the polarization state of the light, making the polarization state better match the requirements of the optical path, achieving full reflection and full transmission when the light reaches the polarizing mirror 2 for the first and second times, respectively. Furthermore, no new stray light is introduced, and the brightness and uniformity of the HUD system image are not reduced. Simply adjusting the first reflector to a common beam splitter that can both transmit and reflect would inevitably lead to new stray light and a significant decrease in brightness.
[0044] The beneficial effects of this invention's vehicle-mounted HUD system using a folded optical path are:
[0045] The optical system of this invention employs a folded optical path design. One of the mirrors in a traditional off-axis three-reflection system is replaced with a polarizer. This mirror can reflect and transmit light with different polarization states. A quarter-wave plate is then added to the optical path system, causing the light to continuously adjust its polarization state during propagation. This allows the light to be reflected or transmitted appropriately as needed when reaching the polarizer multiple times, ensuring the normal operation of the optical path system without introducing stray light. Through the combination of the quarter-wave plate and the polarizer, the polarizer, which would normally need to be placed outside the optical path for adjustment, can be placed inside, reducing the overall size of the optical path through folding.
[0046] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the concept of the present utility model and using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present utility model.
Claims
1. A vehicle-mounted HUD system using a folded optical path, characterized in that, include: Image source, polarizer, reflector, first quarter-wave plate, second quarter-wave plate and windshield; The polarizing mirror is located between the image source and the windshield, the first quarter-wave plate is disposed in front of the image source, and the second quarter-wave plate is disposed in front of the polarizing mirror; The S-polarized light or P-polarized light emitted from the image source passes through the first quarter-wave plate and the second quarter-wave plate, and after being delayed by one-quarter phase twice, the polarization state becomes P-polarized light or S-polarized light, which is reflected at the polarizing mirror. After passing through the second quarter-wave plate, the P-polarized light or S-polarized light is converted into circularly polarized light, reflected at the mirror, with the polarization state unchanged and the phase reversed; after passing through the second quarter-wave plate again, it is converted into S-polarized light or P-polarized light, and then passes through the polarizing mirror, is reflected by the windshield and enters the human eye, forming a virtual image that can be observed by the human eye.
2. The vehicle-mounted HUD system using a folded optical path according to claim 1, characterized in that, The image source can be any one of a TFT system, a DLP system, or an LCOS system.
3. The vehicle-mounted HUD system using a folded optical path according to claim 1, characterized in that, When the image source emits S-polarized light, the polarizing mirror is a polarizing mirror that reflects P-polarized light and transmits S-polarized light; when the image source emits P-polarized light, the polarizing mirror is a polarizing mirror that reflects S-polarized light and transmits P-polarized light.
4. The vehicle-mounted HUD system using a folded optical path according to claim 1, characterized in that, The polarizer and the second quarter-wave plate are partially or completely disposed inside the optical path.
5. The vehicle-mounted HUD system using a folded optical path according to claim 1, characterized in that, The reflector is one of a spherical mirror, an aspherical mirror, or a freeform surface reflector.
6. The vehicle-mounted HUD system using a folded optical path according to claim 1, characterized in that, A polarizing reflective film is provided in front of the windshield.