Optical system and head-up display

Abstract

The invention relates to an optical system and a head-up display. The optical system comprises an image generating unit and an image adjusting unit, the image adjusting unit comprises a first reflecting mirror and a second reflecting mirror and is used for turning image light rays to the projection medium, and the projection medium is used for reflecting the image light rays transmitted by the image adjusting unit, so that a target virtual image which can be observed from the eye box is generated. Wherein image light emitted by the image generation unit sequentially passes through the first reflector and the second reflector to reach the projection medium, the first reflector is provided with a first reflecting surface, and the first reflecting surface is provided with a first reflecting region and a second reflecting region; the first reflecting surface has a horizontal curvature used for adjusting image light in the direction of a horizontal view field for forming the target virtual image, and the horizontal curvature of the first reflecting region is smaller than that of the second reflecting region. According to the optical system and the head-up display, the target virtual image can be displayed under different virtual image distances, and the display effect of the head-up display is enriched.

Description

Technical Field

[0001] The present disclosure relates to the technical field of head-up display, and in particular to an optical system and a head-up display. Background Art

[0002] Head Up Display, also known as Head-up Display System, or HUD for short. Its principle is to project important driving information such as speed and navigation onto a suitable position of the windshield or other projection media through a designed optical path to form a target virtual image for the driver to view, thus avoiding the potential safety hazards caused by the driver lowering his head to view the display information of the instrument or other driving assistance equipment, and increasing driving safety. For augmented reality head-up display (AR-HUD), relevant information can also be combined with environmental information such as roads, vehicles, and pedestrians, and integrated with ADAS (Advanced Driving Assistance System) related functions to further promote cockpit intelligence.

[0003] In the prior art, the virtual image plane generated by AR-HUD projection is basically perpendicular to the road surface, the distances from each image point of the target virtual image to the eye box are basically equal, and the display effect is relatively simple.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the present disclosure is to provide an optical system and a head-up display, which can display a target virtual image at different virtual image distances and enrich the display effect of the head-up display.

[0006] According to one aspect of the present disclosure, there is provided an optical system, comprising:

[0007] An image generating unit, used for generating image light;

[0008] An image adjustment unit, comprising a first reflector and a second reflector, wherein the image light emitted by the image generation unit is sequentially reflected by the first reflector and the second reflector to a projection medium, and the projection medium is used to reflect the image light transmitted by the image adjustment unit, thereby generating a target virtual image observable from an eye box;

[0009] Among them, the first reflector has a first reflective surface, the first reflective surface has a first reflective area and a second reflective area in the direction of the vertical field of view for forming a target virtual image, the first reflective surface has a horizontal curvature for adjusting the image light in the direction of the horizontal field of view for forming the target virtual image, and the horizontal curvature of the first reflective area is smaller than the horizontal curvature of the second reflective area.

[0010] In an exemplary embodiment of the present disclosure,

[0011] The first reflection surface further has a third reflection area, the third reflection area is located between the first reflection area and the second reflection area in the direction of the vertical field of view for forming the target virtual image, wherein the horizontal curvature of the first reflection area is smaller than the horizontal curvature of the third reflection area, and the horizontal curvature of the third reflection area is smaller than the horizontal curvature of the second reflection area;

[0012] The horizontal curvature smoothly transitions at the junction of the first reflection area and the third reflection area, and the horizontal curvature smoothly transitions at the junction of the third reflection area and the second reflection area, and the horizontal curvature monotonically increases from the end adjacent to the first reflection area to the end adjacent to the second reflection area in the third reflection area.

[0013] In an exemplary embodiment of the present disclosure,

[0014] The first reflection area, the third reflection area and the second reflection area are sequentially arranged from an end of the first reflection mirror close to the second reflection mirror to an end of the first reflection mirror far away from the second reflection mirror.

[0015] In an exemplary embodiment of the present disclosure,

[0016] A difference K1-K2 between a horizontal curvature K1 of an end of the second reflection area away from the first reflection area and a horizontal curvature K2 of an end of the first reflection area away from the second reflection area is not less than 5*10^(-4) and not greater than 25*10^(-4).

[0017] In an exemplary embodiment of the present disclosure,

[0018] The first reflection surface of the first reflection area is concave, and the first reflection surface of the second reflection area is convex.

[0019] In an exemplary embodiment of the present disclosure,

[0020] The second reflector is a free-form concave reflector, which is used to deflect image light in the direction of the vertical field of view and the horizontal field of view of the target virtual image. The second reflector is also used to change the size of the target virtual image in the vertical field of view direction and the size of the target virtual image in the horizontal field of view direction;

[0021] The first reflection surface is arranged axisymmetrically in a direction of a horizontal field of view for forming a target virtual image.

[0022] In an exemplary embodiment of the present disclosure,

[0023] The light emitting surface of the image generating unit is inclined in the direction of the vertical field of view for forming the target virtual image, so that the optical path of the image light emitted from the end of the light emitting surface close to the first reflector to the first reflector is smaller than the optical path of the image light emitted from the end of the light emitting surface far from the first reflector to the first reflector.

[0024] In an exemplary embodiment of the present disclosure, an angle between the light emitting surface and the image light emitted from the light emitting surface is less than or equal to 60°.

[0025] In an exemplary embodiment of the present disclosure, the image generation unit includes an illumination light source and a transmissive display screen, and an angle between an illumination light emitted by the illumination light source and the transmissive display screen is less than or equal to 60°.

[0026] In an exemplary embodiment of the present disclosure, the horizontal curvature of the first reflection surface increases monotonically and uniformly from an end of the first reflection area away from the second reflection area to an end of the second reflection area away from the first reflection area.

[0027] In an exemplary embodiment of the present disclosure, for any eye position in the eye box, the difference in horizontal curvature between the two opposite ends of the first reflective surface in the direction of the vertical field of view for forming a target virtual image is not less than 5.8*10^(-4) and not greater than 8.8*10^(-4).

[0028] According to another aspect of the present disclosure, a head-up display is provided, comprising any one of the above optical systems, and

[0029] Shell; wherein the image generating unit, the first reflector and the second reflector are all arranged in the shell.

[0030] In an exemplary embodiment of the present disclosure,

[0031] The first reflector is fixedly mounted on the housing, and the second reflector is rotatably mounted on the housing.

[0032] The optical system and head-up display disclosed in the present invention can display the target virtual image at different virtual image distances. For example, the image light reflected by the first reflection area is displayed as a near view, and the image light reflected by the second reflection area is displayed as a far view. This allows the head-up display to display richer information and meet the driver's needs for intuitive viewing of instrument information such as text and navigation information. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0034] In order to better understand the present disclosure, reference may be made to the embodiments shown in the following drawings. The components in the drawings are not necessarily to scale, and related elements may be omitted in order to emphasize and clearly illustrate the technical features of the present disclosure. In addition, related elements or components may have different arrangements as known in the art. In addition, in the drawings, the same reference numerals represent the same or similar components in each drawing. Among them:

[0035] Figure 1 A schematic diagram of an optical path of an exemplary embodiment of the optical system disclosed herein;

[0036] Figure 2 is a schematic diagram of an exemplary embodiment of a head-up display disclosed herein;

[0037] Figure 3 A sagittal height diagram of a first reflecting surface of an exemplary embodiment of the optical system disclosed herein;

[0038] Figure 4 A sagittal height diagram of a first reflecting surface of another exemplary embodiment of the optical system disclosed herein;

[0039] Figure 5 is a variation trend of the horizontal curvature in the first reflecting surface of an exemplary embodiment of the optical system disclosed herein;

[0040] Figure 6 A schematic diagram of an image generation unit of an exemplary embodiment of the optical system of the present disclosure.

[0041] The following are the descriptions of the reference numerals:

[0042] 1. Image generation unit; 11. Transmissive display screen; 12. Light-emitting lamp board; 13. Light homogenization module; 2. First reflector; 21. First reflective area; 22. Second reflective area; 23. Third reflective area; 3. Second reflector; 4. Projection medium; 5. Eye box; 6. Target virtual image; 7. Shell. DETAILED DESCRIPTION

[0043] The following will be combined with the accompanying drawings in the exemplary embodiments of the present disclosure to clearly and completely describe the technical solutions in the exemplary embodiments of the present disclosure. The exemplary embodiments described herein are only for illustrative purposes and are not intended to limit the scope of protection of the present disclosure. Therefore, it should be understood that various modifications and changes can be made to the exemplary embodiments without departing from the scope of protection of the present disclosure.

[0044] Unless otherwise specified or explained, the technical terms or scientific terms used in this disclosure shall have the usual meanings understood by people with ordinary skills in the field to which this disclosure belongs. The use of "first" and "second" in this disclosure is only used as a mark, not to limit the quantity, importance or order of its objects. "Include" or "comprising" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0045] Furthermore, in the description of the present disclosure, it should be understood that the directional words such as "up", "down", "inside", and "outside" described in the exemplary embodiments of the present disclosure are only used to indicate relative positional relationships. For convenience, the description is made according to the position and state of the head-up display when it is actually working, or according to the angles shown in the accompanying drawings, which should not be understood as a limitation on the exemplary embodiments of the present disclosure. It can be known to those skilled in the art that when the absolute position of the described object changes, the relative positional relationship may also change accordingly. For example, after the structure in the exemplary embodiment of the present disclosure is rotated or the direction and viewing angle of observation are changed, "up" may also become "down" or "left" or "right", and such changes will not cause obstacles to the understanding of those skilled in the art.

[0046] In addition, the "concave" or "convex" of an optical surface described in the present disclosure is relative to the direction of the light incident on the surface. For example, if an optical surface is "concave", the distance from a point on the incident light ray to the center of the surface on the optical axis is greater than the distance from the point to the periphery of the surface.

[0047] In order to facilitate the explanation of the scheme of the present disclosure, the present disclosure provides a possible application scenario in which a head-up display is applied to a car as an example. It should be understood by those skilled in the art that the head-up display of the exemplary embodiment of the present disclosure can also be applied to, for example, sanitation vehicles, fire trucks, military vehicles, and of course, can also be applied to the fields of ships, aviation, etc. For example, it can be applied to aircraft such as fighter jets, so that the driver can track and aim at objects with the help of the head-up display.

[0048] Below, some of the terms used in this application are explained. It should be noted that these explanations are for the convenience of understanding by those skilled in the art and do not constitute a limitation on the scope of protection claimed in this application.

[0049] 1) Field of View

[0050] The field of view angle is the three-dimensional angle between the outline of an object observed by the human eye and the line connecting the center of the pupil of the human eye. For a head-up display, the field of view angle refers to the three-dimensional angle between the edge of the target virtual image 6 formed by the reflection of the optical system of the head-up display and the projection medium 4 and the line connecting the center of the pupil of the human eye. The field of view angle includes the horizontal field of view angle HFOV (Horizontal Field of View) and the vertical field of view angle VFOV (Vertical Field of View). The horizontal field of view angle is also called the lateral field of view angle, which is the maximum visible range of the target virtual image 6 in the horizontal direction. The vertical field of view angle is also called the longitudinal field of view angle, which is the maximum visible range of the target virtual image 6 in the longitudinal direction.

[0051] The “direction of the horizontal field of view” mentioned in the present disclosure refers to the direction of the horizontal field of view angle, and the “direction of the vertical field of view” refers to the direction of the vertical field of view angle.

[0052] 2) Eyebox

[0053] The eye box 5 is the area where the eyes of the driver or observer are located. In the design of the head-up display, the range of the eye box 5 can be determined according to the height, posture, etc. of the driver. The eye box 5 defines an effective area of ​​an eye point. When the observer's eye point moves within this effective area, the observer can see the target virtual image 6 that meets the requirements. The area beyond the eye box 5 may present problems such as image distortion, color error, or even no display.

[0054] 3) Virtual Image Distance (VID)

[0055] The virtual image distance refers to the distance between the center of the eye box 5 and the target virtual image 6 generated by the head-up display. For example, in a possible implementation, the virtual image distance of any position on the target virtual image 6 is the absolute value of the difference between the image point at that position and the x-coordinate of the center of the eye box 5 in the vehicle body coordinate system, where the x-coordinate is the forward or backward direction of the vehicle.

[0056] The augmented reality head-up display can be combined with the advanced driver assistance system to superimpose virtual information such as navigation on the real road surface to achieve a combination of virtual and real. In order to reduce the visual fatigue caused by the driver switching between observing the closer target virtual image 6 and observing the farther real object, and to better fit the target virtual image 6 with the real scene, the virtual image distance of the augmented reality head-up display is usually 7.5m or more, and can even reach 10m to 15m.

[0057] However, in the related art, the virtual image plane generated by the AR-HUD projection is substantially perpendicular to the road surface, and the distances from each image point of the target virtual image 6 to the eye box 5 are substantially equal, resulting in a relatively simple display effect.

[0058] In view of the above problems, the present disclosure provides an optical system, referring to Figure 1 and Figure 2 As shown, it includes an image generating unit 1 and an image adjusting unit, the image generating unit 1 is used to generate image light; the image adjusting unit includes a first reflector 2 and a second reflector 3, the first reflector 2 and the second reflector 3 are used to deflect the image light emitted by the image generating unit 1 to the projection medium 4, and the projection medium 4 is used to reflect the image light propagated by the image adjusting unit, so as to generate a target virtual image 6 that can be observed from the eye box 5. Among them, the image light emitted by the image generating unit 1 is reflected to the projection medium 4 through the first reflector 2 and the second reflector 3 in sequence, the first reflector 2 has a first reflecting surface, the first reflecting surface has a first reflecting area 21 and a second reflecting area 22 in the direction of the vertical field of view for forming the target virtual image 6, the first reflecting surface has a horizontal curvature for adjusting the image light in the direction of the horizontal field of view for forming the target virtual image 6, and the horizontal curvature of the first reflecting area 21 is smaller than the horizontal curvature of the second reflecting area 22.

[0059] The first reflecting surface of the first reflecting mirror 2 includes at least two regions with different horizontal curvatures in the direction of the vertical field of view for forming the target virtual image 6, Figure 2 As shown, reflection surfaces with different horizontal curvatures have different magnification effects on the virtual image distance of the image light reflected by the area. Therefore, when the image light reflected by the first reflection area 21 and the second reflection area 22 enters the eye box 5 after being reflected by the projection medium 4, a target virtual image 6 with different virtual image distances will be generated. Specifically, the horizontal curvature of the first reflection area 21 is smaller than the horizontal curvature of the second reflection area 22, so the virtual image distance of the image light reflected by the first reflection area 21 is smaller than the virtual image distance of the image light reflected by the second reflection area 22. The optical system disclosed in the present invention can display the target virtual image 6 at different virtual image distances, for example, the image light reflected by the first reflection area 21 is displayed as a near view, and the image light reflected by the second reflection area 22 is displayed as a far view, so that the head-up display can display richer information to meet the driver's needs for intuitive viewing of instrument information such as text and navigation information.

[0060] Exemplarily, the projection medium 4 is used to reflect the image light transmitted by the image adjustment unit, thereby generating a target virtual image 6 that can be observed from the eye box 5. The projection medium 4 can be a windshield. Specifically, the image light emitted by the image generation unit 1 passes through the first reflector 2 and the second reflector 3 in sequence and is emitted to the inner surface of the windshield, and is reflected by the inner surface of the windshield to the range of the eye box 5. In other exemplary embodiments, the projection medium 4 can also be a film with a reflective function, which is attached or plated on the inner surface of the windshield. Alternatively, the projection medium 4 can also be other screens, such as a special imaging screen provided on the instrument panel of the car in the cab, etc., which is not particularly limited in the present disclosure.

[0061] The image generating unit 1 is used to generate image light and emit the image light to the first reflector 2. For example, the image generating unit 1 may include a display chip, and the display chip may be a display chip such as a liquid crystal display (LCD), a digital micromirror display (DMD), a liquid crystal on silicon (LCoS), or a laser beam scanning (LBS), etc., as long as the imaging light with uniform brightness that meets the imaging requirements can be emitted, and the present disclosure does not make any special limitation on this.

[0062] It should be noted that, in the present disclosure, the horizontal curvature of the first reflection area 21 is smaller than the horizontal curvature of the second reflection area 22, which may mean that the maximum value of the horizontal curvature of the first reflection area 21 is smaller than the minimum value of the horizontal curvature of the second reflection area 22, that is, the horizontal curvature of the first reflection surface at any point in the first reflection area 21 is smaller than the horizontal curvature of any point in the second reflection area 22, thereby avoiding crosstalk between the image light reflected by the first reflection area 21 and the second reflection area 22. For example, the horizontal curvature in the first reflection area 21 increases from an end away from the second reflection area 22 to an end close to the second reflection area 22, and the horizontal curvature in the second reflection area 22 increases from an end close to the first reflection area 21 to an end away from the first reflection area 21, and the horizontal curvature of the end of the first reflection area 21 close to the second reflection area 22 is smaller than the horizontal curvature of the end of the second reflection area 22 close to the first reflection area 21.

[0063] In particular, in some exemplary embodiments, the first reflection area 21 is adjacent to the second reflection area 22, and the boundary between the first reflection area 21 and the second reflection area 22 can be regarded as being located in the first reflection area 21, or can be regarded as being located in the second reflection area 22. Therefore, the horizontal curvature of the aforementioned first reflection area 21 is smaller than the horizontal curvature of the second reflection area 22, and does not include the horizontal curvature at the boundary between the first reflection area 21 and the second reflection area 22.

[0064] In an exemplary embodiment of the present disclosure, the first reflective surface further has a third reflective area 23, referring to Figure 2 As shown, the third reflection area 23 is located between the first reflection area 21 and the second reflection area 22 in the direction of the vertical field of view for forming the target virtual image 6. The horizontal curvature of the first reflection area 21 is smaller than that of the third reflection area 23, and the horizontal curvature of the third reflection area 23 is smaller than that of the second reflection area 22.

[0065] Specifically, the third reflection area 23 is located between the first reflection area 21 and the second reflection area 22, and the first reflection area 21 is adjacent to the third reflection area 23, and the third reflection area 23 is also adjacent to the second reflection area 22. For example, the first reflection area 21, the third reflection area 23 and the second reflection area 22 can be arranged in sequence from the end of the first reflector 2 close to the second reflector 3 to the end far from the second reflector 3. Figure 2 As shown, the first reflection area 21 is located at the top of the first reflector 2 and close to the bottom of the second reflector 3, and the second reflection area 22 is located at the bottom of the first reflector 2 and close to the image generation unit 1. The virtual image distance of the image light reflected by the second reflection area 22 is large, and after passing through the second reflector 3, it is projected at a position slightly above the projection medium 4; the virtual image distance of the image light reflected by the first reflection area 21 is small, and after passing through the second reflector 3, it is projected at a position slightly below the projection medium 4, so that the upside-down and enlarged target virtual image 6 can be observed within the eye box 5. In this exemplary embodiment, when the driver observes the target virtual image 6, the image with a smaller virtual image distance is located below the field of view, and the image with a larger virtual image distance is located above the field of view, which is consistent with the change law of the driver observing the road surface extending from the front of the vehicle to the distance. Moreover, since the virtual image distances of the image light reflected by the first reflection area 21, the third reflection area 23 and the second reflection area 22 are all different, the target virtual image 6 is not perpendicular to the road surface, but is inclined in a direction parallel to the road surface. By controlling the horizontal curvature of each area of ​​the first reflection surface, different inclination angles of the target virtual image 6 can be obtained, thereby achieving a better fit with the road surface.

[0066] In an exemplary embodiment of the present disclosure, the horizontal curvature smoothly transitions at the junction of the first reflection area 21 and the third reflection area 23, and the horizontal curvature smoothly transitions at the junction of the third reflection area 23 and the second reflection area 22, and the horizontal curvature monotonically increases from the end adjacent to the first reflection area 21 to the end adjacent to the second reflection area 22 in the third reflection area 23. Specifically, the horizontal curvature of the first reflection surface can change continuously throughout the entire first reflection surface without sudden changes, thereby avoiding defects such as image distortion or discontinuity formed in the eye box 5. The horizontal curvature monotonically increases in the third reflection area 23, and the direction of increase is consistent with the direction from the first reflection area 21 to the second reflection area 22. Therefore, the target virtual image 6 area corresponding to the image light reflected by the third reflection area 23 is also smoothly connected to the target virtual image 6 area corresponding to the image light reflected by the first reflection area 21 and the second reflection area 22, which is conducive to adjusting the shape of the target virtual image 6 in the vertical field of view. In other exemplary embodiments, the first reflection surface can be further divided into more areas with different horizontal curvatures in the direction of the vertical field of view for forming the target virtual image 6. For example, the first reflection area 21 and the second reflection area 22 are respectively the opposite ends of the first reflection surface, and a fourth reflection area or more reflection areas can be further included between the first reflection area 21 and the second reflection area 22, and the horizontal curvature has a smooth transition within each reflection area and at the junction.

[0067] The first reflective surface may be a free-form surface, and the horizontal curvature of the first reflective area 21 is smaller than the horizontal curvature of the second reflective area 22. Figure 3 and Figure 4 The sagittal height diagram of the first reflecting surface is shown. In the diagram, the lighter the color, the smaller the sagittal height, and the darker the color, the larger the sagittal height. For details, please refer to the scale on the right. The convex part is the positive value of the curvature, and the concave part is the negative value of the curvature. Figure 3 The first reflection area 21 may be an inner concave surface, the second reflection area 22 may be an outer convex surface, and the third reflection area 23 makes the first reflection area 21 and the second reflection area 22 transition smoothly. Figure 4 In another embodiment of the sagittal height diagram of the first reflection surface, the first reflection area 21 can be a convex surface with a small absolute value of curvature, the end of the first reflection area 21 away from the second reflection area 22 is approximately a plane, and the second reflection area 22 can be a convex surface. In other exemplary embodiments, the first reflection area 21 and the second reflection area 22 can both be convex surfaces.

[0068] In an exemplary embodiment of the present disclosure, the difference K1-K2 between the horizontal curvature K1 of the end of the second reflection area 22 away from the first reflection area 21 and the horizontal curvature K2 of the end of the first reflection area 21 away from the second reflection area 22 is not less than 5*10^(-4) and not more than 25*10^(-4). Figure 5 The variation trend of the horizontal curvature in the first reflecting surface is shown in FIG. Figure 5 The ordinate is the horizontal curvature, and the abscissa is from left to right from the first reflection area 21 to the second reflection area 22. For example, in the embodiment 1 shown by the dotted line, the horizontal curvature K2 of the end of the first reflection area 21 away from the second reflection area 22 is -9*10^(-4), and the horizontal curvature K1 of the end of the second reflection area 22 away from the first reflection area 21 is 1*10^(-4); for another example, in the embodiment 2 shown by the solid line, K2 is 1.2*10^(-3), and K1 is 2.2*10^(-3). Further, for example, the horizontal curvature of the first reflection area 21 increases from the end away from the second reflection area 22 to the end close to the second reflection area 22, and the horizontal curvature in the second reflection area 22 increases from the end close to the first reflection area 21 to the end away from the first reflection area 21, and the difference between K1 and K2 is the maximum value of the difference in horizontal curvature between the second reflection area 22 and the first reflection area 21.

[0069] Exemplarily, for every 1*10^(-4) increase in the horizontal curvature of two positions on the first reflecting surface, the difference in the virtual image distance of the image light reflected by the two positions increases by 0.8m to 1.2m. In an exemplary embodiment of the present disclosure, the eye box 5 has a certain width, and any eye position within the eye box 5 corresponds to a vertical field of view. K1-K2 is not less than 5*10^(-4) and not greater than 25*10^(-4), which can make the difference in the virtual image distance corresponding to the extreme eye positions in the two vertical field of view directions within the width of the eye box 5 be 4m to 30m. According to experiments, this range can satisfy the driver's intuitive reading of text-based driving information in the area with shorter virtual image distance without causing visual burden, while making the area with longer virtual image distance have a good fit with the real world.

[0070] In an exemplary embodiment of the present disclosure, the horizontal curvature of the first reflection surface increases monotonically and uniformly from the end of the first reflection area 21 away from the second reflection area 22 to the end of the second reflection area 22 away from the first reflection area 21. In this exemplary embodiment, in the first reflection surface, the difference in horizontal curvature between the two opposite ends of any area of ​​the same width is equal, and the optical path of the image light emitted from the image generating unit 1 in the direction of the vertical field of view changes monotonically. Therefore, within the width range of the eye box 5, the difference in projection distance between the near end and the far end of the vertical field of view corresponding to any eye position is equal. When the eye position moves within the width range of the eye box 5, the target virtual image 6 with the same virtual image distance can be observed at different eye positions, which can avoid dizziness and improve display quality.

[0071] Further, in an exemplary embodiment of the present disclosure, for any eye position in the eye box 5, the difference in horizontal curvature between the two opposite ends of the first reflective surface in the direction of the vertical field of view for forming the target virtual image 6 is not less than 5.8*10^(-4) and not greater than 8.8*10^(-4). In this exemplary embodiment, the difference in virtual image distance between the near end and the far end of the vertical field of view corresponding to any eye position can be controlled to be about 7m. For example, the virtual image distance of the near end of the vertical field of view corresponding to any eye position is 5m, and the virtual image distance of the far end of the vertical field of view corresponding to any eye position is 12m. Under this difference in projection distance, the near-end information can be taken into account to facilitate human eye observation and the target virtual image 6 can be nearly parallel to the ground as a whole, so that the target virtual image 6 has a reasonable spatial depth, and vehicles or pedestrians at different distances on the road can be marked more accurately.

[0072] In an exemplary embodiment of the present disclosure, the light emitting surface of the image generating unit 1 is tilted in the direction of the vertical field of view for forming the target virtual image 6, so that the optical path of the image light emitted from the end of the light emitting surface close to the first reflector 2 to the first reflector 2 is shorter than the optical path of the image light emitted from the end of the light emitting surface far from the first reflector 2 to the first reflector 2. Figure 1 As shown, the tilting of the light emitting surface of the image generating unit 1 can also change the difference in projection distance between the near end and the far end of the vertical field of view, thereby changing the difference in virtual image distance between the near end and the far end of the vertical field of view. The light paths between the light emitting surface and the first reflector 2 do not cross, so the image light emitted from the end of the light emitting surface close to the first reflector 2 is projected to the first reflective area 21 and has a shorter optical path; the image light emitted from the end of the light emitting surface far from the first reflector 2 is projected to the second reflective area 22 and has a longer optical path.

[0073] For example, in an exemplary embodiment of the present disclosure, the angle between the light emitting surface of the image generating unit 1 and the image light emitted from the light emitting surface is less than or equal to 60°, that is, the angle between the image light emitted from the light emitting surface and the normal line of the light emitting surface is not less than 30°. According to experiments, when the image adjustment unit and the projection medium 4 are unchanged, the difference in the virtual image distance of the image light reflected by the first reflection area 21 and the second reflection area 22 increases by 0.15m to 0.30m for every 1° increase in the angle between the image light emitted from the light emitting surface and the normal line of the light emitting surface. By adjusting the inclination angle of the light emitting surface of the image generating unit 1, in coordination with the difference in the horizontal curvature of the first reflection area 21 and the second reflection area 22 of the present disclosure, the virtual image distance of the target virtual image 6 and the depth of field of the target virtual image 6 can be accurately adjusted, so that the near-end virtual image distance and the far-end virtual image distance of the vertical field of view both meet the driver's comfortable viewing needs.

[0074] Specifically, in an exemplary embodiment of the present disclosure, referring to Figure 6As shown, the image generation unit 1 includes an illumination light source and a transmissive display screen 11, such as a TFT-LCD screen. The surface of the transmissive display screen 11 is the light emitting surface of the image generation unit 1. The illumination light source may be a light emitting lamp board 12. The light emitting mode of the light emitting lamp board 12 may be, for example, laser illumination. Alternatively, the light emitting lamp board 12 may include a plurality of arrays of LED lamp beads. The illumination light source also includes a light homogenizing module 13. The light homogenizing module 13 is disposed between the light emitting lamp board 12 and the transmissive display screen 11, and is used to collimate and homogenize the illumination light emitted by the array of LED lamp beads. Exemplarily, the illumination light emitted by the light emitting lamp board 12 is along the normal direction of the light emitting lamp board 12. The angle between the illumination light emitted by the illumination light source and the transmissive display screen 11 is the angle between the light emitting lamp board 12 and the transmissive display screen 11.

[0075] In other exemplary embodiments, for the image generating unit 1 of other projection methods, such as a digital light processing (DLP) projection scheme using a digital micromirror display chip, the image generating unit 1 can directly emit image light with a specific inclination angle.

[0076] The first reflector 2 is a non-rotationally symmetric free-form surface mirror. In an exemplary embodiment of the present disclosure, the first reflective surface may be a non-axisymmetric surface in the direction of the horizontal field of view of the target virtual image 6. Specifically, the first reflective surface has a vertical curvature for adjusting the image light in the direction of the vertical field of view of the target virtual image 6. The vertical curvature of the first reflective surface may be determined based on the designed virtual image distance in the horizontal field of view of the target virtual image 6. In another exemplary embodiment, the first reflective surface is arranged axisymmetrically in the direction of the horizontal field of view for forming the target virtual image 6. Figure 3 and Figure 4 The two opposite sides of the horizontal field of view for forming the target virtual image 6 on the first reflective surface are symmetrical about the central axis of the first reflective surface, so that the depth of field of the target virtual image 6 on the two opposite sides of the horizontal field of view is also symmetrical, which is beneficial to improving the driver's comfort and immersion when looking at the target virtual image 6 with both eyes, and is also beneficial to the detection and control of the horizontal curvature of the first reflective surface. Figure 3 and Figure 4 In an exemplary embodiment, the vertical curvature of the first reflecting surface is minimum at the horizontal central symmetry axis of the first reflecting surface, and the vertical curvature gradually increases from the symmetry axis to the opposite ends of the first reflecting surface in the horizontal direction.

[0077] The second reflector 3 is used to further deflect the image light reflected by the first reflector 2. In an exemplary embodiment of the present disclosure, the second reflector 3 is a free-form concave reflector, which is used to deflect the image light in the direction of the vertical field of view and the horizontal field of view of the target virtual image 6, and change the size of the target virtual image 6 in the vertical field of view and the size of the target virtual image 6 in the horizontal field of view. On the one hand, the second reflector 3 is used to deflect the light path so that the image light is reflected from the head-up display and projected onto the projection medium 4; on the other hand, the second reflector 3 is also used to reduce the divergence angle of the image light and adjust the size, shape, etc. of the target virtual image 6. Since the projection medium 4 is usually a windshield, the surface of the windshield is a complex free-form surface, and the image light will produce aberration and distortion after being reflected by the windshield. Therefore, in some exemplary embodiments, the second reflector 3 is also used to balance the image aberration caused by the projection medium 4. Specifically, the second reflector 3 can be corrected in advance according to the surface shape of the windshield to compensate for the aberration and distortion of the image light emitted by the second reflector 3 after being reflected by the windshield.

[0078] Due to the different heights and postures of the drivers and passengers, the observation range may be different, that is, the range of the eye box 5 is different. In order to enable different eye boxes 5 ranges to observe a relatively clear target virtual image 6, in some exemplary embodiments, the angle of the second reflector 3 is adjustable relative to the first reflector 2, the image generation unit 1, and the housing 7 of the head-up display. For example, the second reflector 3 can be rotatably connected to the housing 7 of the head-up display. Different eye boxes 5 correspond to different rotation positions of the second reflector 3. For example, as the second reflector 3 rotates, the image light is reflected at different areas on the surface of the second reflector 3 and projected onto different areas in the vertical direction of the projection medium 4, so that the head-up display has an upper eye box position, a middle eye box position, and a lower eye box position. In some exemplary embodiments, in order to avoid sunlight backflow and display chip burning caused by the reversibility of the optical path, the second reflector 3 can also be rotated to a dormant position when the head-up display is not working, so that the optical path between the first reflector 2 and the second reflector 3 is changed. Specifically, when the second reflector 3 is in the sleep position, after external sunlight enters the second reflector 3, it is reflected by the second reflector 3 to the surface with extinction function, and the sunlight is absorbed. The external sunlight cannot be reflected by the second reflector 3 to the first reflector 2, thereby preventing the sunlight from entering the image generation unit 1.

[0079] In an exemplary embodiment of the present disclosure, the second reflector 3 is adjustable in angle in the optical system, for example, connected to the housing 7 of the head-up display through a rotating shaft, and the first reflector 2 and the image generation unit 1 have fixed positions and angles. During the rotation of the second reflector 3, the image light emitted by the first reflector 2 is reflected at different areas of the second reflector 3, that is, at any eye box position, only a part of the area of ​​the second reflector 3 participates in the imaging. As for the first reflector 2, at any eye box position, the entire first reflection surface participates in the imaging. This exemplary embodiment can improve the utilization rate of the first reflector 2 while allowing the head-up display to have multiple eye box positions, so that under the same volume of the first reflector 2, the proximal area and the distal area of ​​the target virtual image 6 can have a larger virtual image distance difference; or reduce the volume of the first reflector 2 while achieving the same virtual image distance difference between the proximal area and the distal area.

[0080] According to another aspect of the present disclosure, a head-up display is also provided, and the head-up display includes a housing 7 and an optical system of any of the aforementioned exemplary embodiments and possible combinations thereof. The image generation unit 1, the first reflector 2, and the second reflector 3 are all accommodated in the housing 7. The working principle of the head-up display and the connection method between the first reflector 2 and the second reflector 3 and the housing 7 can refer to the description of the aforementioned exemplary embodiments, which will not be repeated here. The head-up display of the present disclosure can display the target virtual image 6 at different virtual image distances, so that more abundant information can be displayed to meet the driver's needs for intuitive viewing of instrument information such as text and navigation information.

[0081] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. The present disclosure is intended to cover any variations, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The description and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the appended claims.

[0082] It should be understood that the present disclosure is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from its scope. The scope of protection of the present disclosure is limited only by the appended claims.

Claims

1. An optical system, characterized in that: include: An image generating unit, used for generating image light; An image adjustment unit, comprising a first reflector and a second reflector, wherein the image light emitted by the image generation unit is sequentially reflected by the first reflector and the second reflector to a projection medium, and the projection medium is used to reflect the image light transmitted by the image adjustment unit, thereby generating a target virtual image observable from an eye box; Among them, the first reflector has a first reflective surface, the first reflective surface has a first reflective area and a second reflective area in the direction of the vertical field of view for forming the target virtual image, the first reflective surface has a horizontal curvature for adjusting the image light in the direction of the horizontal field of view for forming the target virtual image, and the horizontal curvature of the first reflective area is smaller than the horizontal curvature of the second reflective area.

2. The optical system according to claim 1, characterized in that The first reflection surface further has a third reflection area, and the third reflection area is located between the first reflection area and the second reflection area in the direction of the vertical field of view for forming the target virtual image, wherein the horizontal curvature of the first reflection area is smaller than the horizontal curvature of the third reflection area, and the horizontal curvature of the third reflection area is smaller than the horizontal curvature of the second reflection area; The horizontal curvature smoothly transitions at the junction of the first reflection area and the third reflection area, the horizontal curvature smoothly transitions at the junction of the third reflection area and the second reflection area, and the horizontal curvature monotonically increases in the third reflection area from an end adjacent to the first reflection area to an end adjacent to the second reflection area.

3. The optical system according to claim 2, characterized in that The first reflection area, the third reflection area and the second reflection area are sequentially arranged from an end of the first reflection mirror close to the second reflection mirror to an end of the first reflection mirror far away from the second reflection mirror.

4. The optical system according to claim 2, characterized in that A difference K1-K2 between the horizontal curvature K1 of the end of the second reflection area away from the first reflection area and the horizontal curvature K2 of the end of the first reflection area away from the second reflection area is not less than 5*10^(-4) and not greater than 25*10^(-4).

5. The optical system according to claim 1, characterized in that The first reflection surface of the first reflection area is concave, and the first reflection surface of the second reflection area is convex.

6. The optical system according to claim 1, characterized in that The second reflector is a free-form concave reflector, used for deflecting the image light in the direction of the vertical field of view and the horizontal field of view of the target virtual image, and the second reflector is also used for changing the size of the target virtual image in the direction of the vertical field of view and the size of the target virtual image in the direction of the horizontal field of view; The first reflection surface is arranged axisymmetrically in a direction of the horizontal field of view for forming the target virtual image.

7. The optical system according to claim 1, characterized in that The light emitting surface of the image generating unit is inclined in the direction of the vertical field of view for forming the target virtual image, so that the optical path of the image light emitted from the end of the light emitting surface close to the first reflector to the first reflector is smaller than the optical path of the image light emitted from the end of the light emitting surface far from the first reflector to the first reflector.

8. The optical system according to claim 7, characterized in that An included angle between the light emitting surface and the image light emitted from the light emitting surface is less than or equal to 60°.

9. The optical system according to claim 8, characterized in that The image generation unit includes an illumination light source and a transmissive display screen, and the included angle between the illumination light emitted by the illumination light source and the transmissive display screen is less than or equal to 60°.

10. The optical system according to any one of claims 1 to 9, characterized in that The horizontal curvature of the first reflection surface increases monotonically and uniformly from an end of the first reflection area away from the second reflection area to an end of the second reflection area away from the first reflection area.

11. The optical system according to claim 10, characterized in that For any eye position in the eye box, the difference in the horizontal curvature of the first reflecting surface at two opposite ends in the direction of the vertical field of view for forming the target virtual image is not less than 5.8*10^(-4) and not greater than 8.8*10^(-4).

12. A head-up display, characterized in that: An optical system comprising any one of claims 1 to 11, and case; Wherein, the image generation unit, the first reflector and the second reflector are all arranged in the shell.

13. The head-up display according to claim 12, characterized in that: The first reflector is fixedly mounted on the housing, and the second reflector is rotatably mounted on the housing.

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