Patent Publication Number: US-2021191116-A1

Title: Head-up display and vehicle

Description:
RELATED APPLICATIONS 
     The present application claims the benefit of Chinese Patent Application No. 201810511714.7, filed on May 24, 2018, the entire disclosures of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to the field of image display, and in particular, to a head-up display and a vehicle. 
     BACKGROUND 
     In order to increase comfort and safety in modern vehicles, more and more vehicles are equipped with head-up displays (HUD). The head-up display usually uses a reflective imaging system to image the driving information displayed on a small display screen (usually with a size of 1.8 inches or 3.1 inches) as a virtual image suspending above the bonnet. The vehicle head-up display technology can enable the driver to observe the driving assistance information acquired by the vehicle system without interrupting the driver&#39;s observation of the road conditions, thereby effectively improving the operating efficiency of the traffic system and ensuring driving safety. 
     SUMMARY 
     In a first aspect, a head-up display is provided. The head-up display includes: an image generating device and an optical module. The optical module includes at least a first optical component, a second optical component, and a third optical component. The first optical component is on a light emitting side of the image generating device. The image generating device emits a first projection light to the first optical component, and the first projection light is linearly polarized light. The second optical component receives the first projection light reflected or transmitted by the first optical component and changes a polarization direction of the first projection light to obtain a second projection light, and reflects the second projection light back to the first optical component. The third optical component receives the second projection light reflected or transmitted by the first optical component and changes a polarization direction of the second projection light to obtain a third projection light, and reflects the third projection light back to the first optical component. 
     In one or more embodiments of the present disclosure, the first optical component includes a polarization beam splitting element, and the polarization beam splitting element selectively transmits or reflects two linearly polarized light whose polarization directions are perpendicular to each other in a plurality of optical paths. 
     In one or more embodiments of the present disclosure, the first projection light is P-polarized light, the second projection light is S-polarized light, and the third projection light is P-polarized light. The first optical component transmits the first projection light to the second optical component, reflects the second projection light to the third optical component, and transmits the third projection light. 
     In one or more embodiments of the present disclosure, the first projection light is S-polarized light, the second projection light is P-polarized light, and the third projection light is S-polarized light. The first optical component reflects the first projection light to the second optical component, transmits the second projection light to the third optical element, and reflects the third projection light. 
     In one or more embodiments of the present disclosure, the second optical component includes a first polarization conversion element and a first reflective element; and the third optical component includes a second polarization conversion element and a second reflective element. 
     In one or more embodiments of the present disclosure, at least one of the first reflective element and the second reflective element is a concave mirror. 
     In one or more embodiments of the present disclosure, one of the first reflective element and the second reflective element is a flat mirror. 
     In one or more embodiments of the present disclosure, the image generating device includes a first display element and a half-wave plate. The first display element emits linearly polarized light. The half-wave plate changes a polarization direction of the linearly polarized light emitted from the first display element to obtain the first projection light. 
     In one or more embodiments of the present disclosure, the image generating device includes a second display element and a polarizer. The second display element emits non-linearly polarized light. The polarizer converts the non-linearly polarized light emitted from the second display element into linearly polarized light to obtain the first projection light. 
     In one or more embodiments of the present disclosure, the first polarization conversion element and the second polarization conversion element are ¼ wave plates, respectively. 
     In one or more embodiments of the present disclosure, the optical module further includes a fourth optical component. The fourth optical component receives and reflects the third projection light. 
     In one or more embodiments of the present disclosure, the fourth optical component includes a windshield of a vehicle. 
     In a second aspect, a vehicle is disclosed. The vehicle includes the head-up display provided by the embodiments of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly illustrate the technical solutions in embodiments of the disclosure or in the prior art, the appended drawings needed to be used in the description of the embodiments or the prior art will be introduced briefly in the following. Obviously, the drawings in the following description are only some embodiments of the disclosure, and for those of ordinary skills in the art, other drawings may be obtained according to these drawings under the premise of not paying out creative work. 
         FIG. 1  shows an exemplary structural block diagram of a head-up display according to an embodiment of the present disclosure; 
         FIG. 2  shows an exemplary structure diagram of a head-up display according to an embodiment of the present disclosure; 
         FIG. 3  shows an exemplary structure diagram of a head-up display according to another embodiment of the present disclosure; 
         FIG. 4  shows a schematic structure diagram of an image generating device according to an embodiment of the present disclosure; and 
         FIG. 5  shows a schematic structure diagram of an image generating device according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     In the following, the technical solutions in embodiments of the disclosure will be described clearly and completely in connection with the drawings in the embodiments of the disclosure. Obviously, the described embodiments are only part of the embodiments of the disclosure, and not all of the embodiments. Based on the embodiments in the disclosure, all other embodiments obtained by those of ordinary skills in the art under the premise of not paying out creative work pertain to the protection scope of the disclosure. 
     In the description of the present disclosure, it should be noted that the terms “first”, “second”, and “third” are used for descriptive purposes only, and cannot be understood to indicate or imply relative importance. 
     It should be noted that, in the case of no conflict, the embodiments in the present disclosure and the features in the embodiments can be combined with each other. The disclosure will be described in detail below with reference to the drawings and in connection with the embodiments. 
     Vehicle head-up displays are developed towards augmented reality display with large viewing angles and long projection distances, which places higher requirements on the performance of optical systems. However, off-axis optical systems based on reflection imaging principle are constrained by basic principle of geometrical optics. As the viewing angle increases, the size of the mirror surface increases, and the volume also increases accordingly; in addition, the aberration of the off-axis systems will also increase, and the design will be further complicated, making it difficult to reduce the volume of the off-axis optical systems. In view of the above defects or deficiencies in the prior art, it is desired to provide a head-up display with high integration and small volume. 
       FIG. 1  shows an exemplary structural block diagram of a head-up display according to an embodiment of the present disclosure. As shown in  FIG. 1 , the head-up display includes an image generating device  11  and an optical module  10 . The optical module  10  includes a first optical component  13 , a second optical component  14 , a third optical component  16 , and a fourth optical component  12 . The first optical component  13  is on a light emitting side of the image generating device  11 . The image generating device  11  emits a first projection light A to the first optical component  13 , and the first projection light A is linearly polarized light. The second optical component  14  receives the first projection light A reflected or transmitted by the first optical component  13  and changes a polarization direction of the first projection light A to obtain a second projection light B, and reflects the second projection light B back to the first optical component  13 . The third optical component  16  receives the second projection light B reflected or transmitted by the first optical component  13  and changes a polarization direction of the second projection light B to obtain a third projection light C, and reflects the third projection light C back to the first optical component  13 . 
     In the embodiment of the present disclosure, the first optical component  13  reflects or transmits the first projection light A, the second projection light B, and the third projection light C. 
     Optionally, the optical module  10  may further include the fourth optical component  12 . The fourth optical component  12  receives and reflects the third projection light C. As shown in  FIG. 1 , the fourth optical component  12  receives and reflects the third projection light C, so that an observer can observe a virtual image. By using the mutual cooperation of the first optical component  13 , the second optical component  14 , and the third optical component  16 , the first projection light A emitted by the image generating device  11  is transmitted and reflected by the first optical component  13  many times and then incident to the fourth optical component  12 , so that an observer can observe a virtual image. 
     The above structure improves the integration degree of the head-up display and reduces the volume. According to the technical solution provided by the embodiment of the present disclosure, multiple propagations of the light beam is realized by the image generating device combined with the optical module, which solves the problem of large space occupied by the light path in the traditional head-up display and achieves the effect of reducing the volume. 
     In some embodiments, as shown in  FIG. 2 , the first optical component  13  may include a polarization beam splitting element  103 , and the polarization beam splitting element  103  selectively transmits or reflects two linearly polarized light whose polarization directions are perpendicular to each other in a plurality of optical paths. In practical applications, the polarization beam splitting element  103  may be a polarization beam splitter. The polarization beam splitter may be formed by, for example, bonding two right-angle prisms. An inclined surface of one of the right-angle prisms is coated with a polarization beam splitting dielectric film, and the inclined surface forms an included angle with a first polarization conversion element  104  or a second polarization conversion element  106 . Optionally, the included angle is 45 degrees. 
       FIG. 2  shows an exemplary structure diagram of a head-up display according to an embodiment of the present disclosure. The first projection light A 1  is P-polarized light, the second projection light B 1  is S-polarized light, and the third projection light C 1  is P-polarized light. The first optical component including the polarization beam splitter  103  transmits the first projection light A 1  to the second optical component including the first polarization conversion element  104  and a first reflective element  105 . The first optical component further reflects the second projection light B 1  to the third optical component including the second polarization conversion element  106  and a second reflective element  107 , and transmits the third projection light C 1  to the fourth optical component including a reflective element  102 . 
       FIG. 3  shows an exemplary structure diagram of a head-up display according to another embodiment of the present disclosure. The first projection light A 2  is S-polarized light, the second projection light B 2  is P-polarized light, and the third projection light C 2  is S-polarized light. The first optical component  13  reflects the first projection light A 2  to the second optical component including a first polarization conversion element  104  and a first reflective element  105 . The first optical component further transmits the second projection light B 2  to the third optical element including a second polarization conversion element  106  and a second reflective element  107 , and reflects the third projection light C 2  to the fourth optical component including a reflective element  102 . 
     In some embodiments, at least one of the first reflective element  105  and the second reflective element  107  is a concave mirror. In order to be able to adjust the focal power and obtain a relatively small system aberration, the first reflective element  105  or the second reflective element  107  may be a concave mirror. Of course, both the first reflective element  105  and the second reflective element  107  can be concave mirrors. Specifically, the concave mirror may adopt an aspherical surface or a spherical surface to meet the needs of imaging within a preset viewing angle. In addition, when the asymmetry of the reflective element  102  is obvious, the concave mirror may adopt a non-rotationally symmetric free curved surface to ensure the imaging quality. 
     In some embodiments, one of the first reflective element  105  and the second reflective element  107  is a flat mirror. When one reflective element is a concave mirror, the other reflective element may be a flat mirror. 
       FIG. 4  shows a schematic structure diagram of an image generating device according to an embodiment of the present disclosure. As shown in  FIG. 4 , in some embodiments, the image generating device  101  includes a first display element  1011  and a half-wave plate  1012 . The first display element  1011  emits linearly polarized light. The half-wave plate  1012  changes a polarization direction of the linearly polarized light emitted from the first display element  1011  to obtain the first projection light. For example, when the first display element is a liquid crystal display device such as LCD or LCOS (Liquid Crystal on Silicon) that emits linearly polarized light, a display device that emits light with the same polarization direction as P-polarized light or S-polarized light may be used. If the polarization direction of the emitted polarized light is not the same as the P-polarized direction or the S-polarized direction, a half-wave plate, for example, can be added to the light emitting surface of the first display element  1011 , the angle between the fast axis of the half-wave plate and the polarization direction can be adjusted, and the required P-polarized light or S-polarized light can thus be obtained. 
       FIG. 5  shows a schematic structure diagram of an image generating device according to another embodiment of the present disclosure. In some embodiments, as shown in  FIG. 5 , the image generating device may include a second display element  1013  and a polarizer  1014 . The second display element  1013  emits non-linearly polarized light. The polarizer  1014  converts the non-linearly polarized light emitted from the second display element  1013  into the required linearly polarized light to obtain the first projection light. 
     In some embodiments, the first polarization conversion element  104  and the second polarization conversion element  106  are ¼ wave plates, respectively. 
     The ¼ wave plate can convert incident linearly polarized light into circularly polarized light, or convert incident circularly polarized light into linearly polarized light. The optical path of the head-up display using a ¼ wave plate as the polarization conversion element in  FIG. 2  is specifically as follows. The P-polarized light emitted from the image generating device  101  is transmitted through the polarization beam splitting layer  103  and is incident on the first polarization conversion element  104 . The P-polarized light transmitted through the first polarization conversion element  104  is converted into left-handed (or right-handed) circularly polarized light, and becomes right-handed (or left-handed) circularly polarized light after being reflected by the first reflective element  105 . After being transmitted through the first polarization conversion element  104  again, it is converted into S-polarized light. Then the light is incident on the polarization beam splitting layer  103  for the second time. 
     The S-polarized light reflected by the polarization beam splitting layer  103  is incident on the second polarization conversion element  106 , is transmitted through the second polarization conversion element  106 , and is converted into left-handed (or right-handed) circularly polarized light. It becomes right-handed (or left-handed) circularly polarized light after being reflected by the second reflective element  107 . The circularly polarized light is transmitted through the second polarization conversion element  106  again and converted into P-polarized light, then incident on the polarization beam splitting layer  103  for a third time, and then incident on the reflective element  102  after being transmitted through the polarization beam splitting layer  103 . During the whole process, the light reaches the surfaces of the PBS (polarizing beam splitter) 3 times, and the multiple reflections inside the PBS can effectively increase the spatial density of the beam and reduce the system volume. It can be seen that in the present disclosure, the polarization beam splitting layer selectively transmits or reflects linearly polarized light beams in a plurality of optical paths, and does not function to split a light beam into two linearly polarized light beams with propagation directions perpendicular to each other. 
     Similarly, the optical path of the head-up display using a ¼ wave plate as the polarization conversion element in  FIG. 3  is specifically as follows. The S-polarized light emitted from the image generating device  101  is reflected by the polarization beam splitting layer  103  and incident on the first polarization conversion element  104 . The S-polarized light is transmitted through the first polarization conversion element  104  and converted into left-handed (or right-handed) circularly polarized light. After being reflected by the first reflective element  105 , it becomes right-handed (or left-handed) circularly polarized light. Then the circularly polarized light is transmitted through the first polarization conversion element  104  and converted into P-polarized light again, and is incident on the polarization beam splitting layer  103  for the second time. 
     The P-polarized light transmitted through the polarization beam splitting layer  103  is incident on the second polarization conversion element  106 , and is converted into left-handed (or right-handed) circularly polarized light after being transmitted through the second polarization conversion element  106 , and becomes right-handed (or left-handed) circularly polarized light after being reflected by the second reflective element  107 . Then the circularly polarized light is transmitted through the second polarization conversion element  106  and converted into S-polarized light, incident on the polarization beam splitting layer  103  for the third time, and then incident on the reflective element  102  after being reflected by the polarization beam splitting layer  103 . 
     Optionally, the reflective element  102  is a windshield of a vehicle. In this embodiment, the observer can observe an individual clear projection in front of the vehicle. The angle at which the P-polarized light is incident on the windshield is related to the reflectivity. When the reflectivity is low, the reflectivity can be increased by coating the windshield with a reflective film. 
     The present disclosure also provides a vehicle including the head-up display provided in any one of the above-mentioned embodiments. 
     The flowcharts and block diagrams in the drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions noted in the blocks may also occur in a different order than those marked in the drawings. For example, two successively connected blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and/or flowcharts, and combinations of blocks in the block diagrams and/or flowcharts, can be implemented by a dedicated hardware-based system that performs the specified function or operation, or it can be implemented with a combination of dedicated hardware and computer instructions. 
     The above embodiments are only used for explanations rather than limitations to the present disclosure, the ordinary skilled person in the related technical field, in the case of not departing from the spirit and scope of the present disclosure, may also make various modifications and variations, therefore, all the equivalent solutions also belong to the scope of the present disclosure, the patent protection scope of the present disclosure should be defined by the claims.