CN113970845A

CN113970845A - Multi-focal plane head-up display device

Info

Publication number: CN113970845A
Application number: CN202010716125.XA
Authority: CN
Inventors: 陈锡勋
Original assignee: E Lead Electronic Co Ltd
Current assignee: E Lead Electronic Co Ltd
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2022-01-25
Anticipated expiration: 2040-07-23
Also published as: CN113970845B

Abstract

The invention relates to a multi-focal plane head-up display device, which comprises a main body, a projector, a first reflecting element, a second reflecting element, a polarizing element and a third reflecting element. The polarization direction of the first image light of the first area of the projection picture projected by the projector is perpendicular to the polarization direction of the second image light of the second area of the projection picture. The first image light passes through the first reflecting element and the polarizing element to form a first virtual image. The second image light passes through the second reflecting element, the polarizing element and the third reflecting element to form a second virtual image. Therefore, two virtual images with different focal planes can be provided, the volume occupied by the head-up display equipment can be reduced, and the manufacturing cost is reduced.

Description

Multi-focal plane head-up display device

Technical Field

The present invention relates to a display, and more particularly, to a head-up display device capable of providing multiple focal planes.

Background

The demands of drivers on vehicles nowadays are also beginning to emphasize the requirements of vehicle interior and safety equipment in addition to the performance of the vehicle itself. The assistance of the scientific and technological products, such as a voice navigation system and a voice collision warning system in the vehicle, really improves the accident rate caused by long-time fatigue driving and inattentive attention of the driver. At the same time, however, since the dashboard that the driver must use is a non-voice device and is usually located below the driver's viewing direction, the driver often needs to move his or her line of sight down to the dashboard in order to see the information provided on the dashboard. In addition, the display device of the navigation system is also usually installed at the side of the dashboard, so when the driver wants to view the road information on the display device, the driver must also shift the time line to see the road information. In such a case, driving safety is easily affected.

In this regard, a head-up display has been developed that allows a user to view desired information without shifting his or her line of sight. The existing head-up display generally consists of two main components, namely a projector and a combiner. The projector is composed of a signal light source, a projection lens and other optical components. The signal Light source of the projector may be provided by a liquid crystal display or a cathode ray tube display, or may be provided by a plurality of Light emitting diodes or lasers in combination with micro-mirrors or Digital Light Processing (DLP) components. The projector will project the light from the signal light source onto the image-folding mirror (or special transparent screen) on the glass, so that the image-folding mirror can display the characters or images.

As shown in fig. 1, the head-up display for a vehicle uses one or more mirrors to adjust the light path, enlarge the image or correct the deformation of the light projected by the projector, and finally reflects the light to the eyes of the driver through the windshield, so that the driver can see the virtual image formed by the projected light in front of the windshield. This is the single focal plane head-up display. However, when such a head-up display for a vehicle is used to guide a driver to switch to a correct lane or to warn a vehicle ahead, the driver still needs to pay attention from the road to the image projected by the head-up display because the formed image of the guide symbol cannot be attached to the road visually seen by the driver.

Therefore, another vehicle head-up display capable of providing dual focus has been developed, as shown in fig. 2. The head-up display utilizes a plurality of reflectors to respectively carry out light path adjustment, image amplification or deformation correction and the like on light rays projected by two projectors, and finally the light rays are reflected to eyes of a driver by a windshield, so that the driver can see virtual images of two different focal planes positioned in front of the windshield, wherein the display distance of one focal plane is elongated and is attached to a road surface, and the problem that the focal point of the driver needs to be switched between a road and a navigation guide symbol is solved. However, using two projectors not only requires more mirrors to match them, but also increases the manufacturing cost and the space occupied.

As shown in fig. 3, another conventional dual-focal-plane head-up display for a vehicle using a single projector is disclosed, in which image light projected by the projector is split by a reflective polarizer, reflected by a concave reflector, and then emitted to a windshield, and reflected into a driver's eye to form virtual images of two different focal planes in front of the windshield, however, in the light path design, the reflective polarizer easily shields a light outlet, which causes a shortage of the light outlet; if a sufficiently large light outlet is designed, the size of the whole light machine needs to be increased.

Disclosure of Invention

The invention aims to provide a head-up display device capable of providing virtual images of multiple focal planes.

An embodiment of the invention provides a multi-focal-plane head-up display device, which includes a main body, a projector, a first reflective element, a second reflective element, a polarization element, and a third reflective element. The main part contains light-emitting window and accommodation space, and the light-emitting window is towards windshield. The projector, the first reflecting element, the second reflecting element, the polarizing element and the third reflecting element are positioned in the accommodating space. The projector is used for projecting light containing a projection picture, the projection picture comprises a first area and a second area, the light comprises first image light corresponding to the first area and second image light corresponding to the second area, and the polarization directions of the first image light and the second image light are perpendicular to each other. The polarizing element has a first side and a second side opposite to the first side, and the first reflecting element and the second reflecting element are disposed on the first side of the polarizing element. The polarizing element allows one of the first image light and the second image light to pass therethrough and allows the other of the first image light and the second image light to reflect. The third reflective element is located on the second side of the polarizing element. The first area of the projector, the first reflection element, the polarization element and the windshield are sequentially arranged on the first light path, and the first image light is incident to human eyes through the first light path to form a first virtual image. The second area of the projector, the second reflection element, the polarization element, the third reflection element and the windshield are sequentially arranged on the second light path, and the second image light is incident to human eyes through the second light path to form a second virtual image.

In other embodiments, the angle of the polarizing element to the third reflective element is greater than 0 degrees.

In other embodiments, the polarizing element is a polarizing beamsplitter or a polarizing splitting film.

In other embodiments, the first image light and the second image light projected by the projector are linearly polarized light, and the head-up display device further includes a phase retardation element disposed in the first region or the second region. One of the first image light and the second image light passes through the phase delay component to form delayed image light, and the polarization direction of the delayed image light is vertical to the polarization direction of the other one of the first image light and the second image light.

In another embodiment, the first image light and the second image light projected by the projector are linearly polarized light, the head-up display apparatus further includes a first phase retardation element and a second phase retardation element, the first phase retardation element is disposed in the first region, the second phase retardation element is disposed in the second region, the first image light and the second image light respectively pass through the respective phase retardation elements to form two delayed image lights, and a polarization direction of the delayed image light of the first image light and a polarization direction of the delayed image light of the second image light are perpendicular to each other.

In another embodiment, the first image light and the second image light projected by the projector have no specific polarization, the head-up display apparatus further includes a first linear polarizer and a second linear polarizer, the first linear polarizer is disposed in the first region, the second linear polarizer is disposed in the second region, and the first image light and the second image light form linear polarized lights with polarization directions perpendicular to each other after passing through the respective linear polarizers.

In other embodiments, at least one of the first reflective element, the second reflective element, the polarizing element, and the third reflective element is a curved mirror.

In other embodiments, the first phase delay element and the second phase delay element are half-wave plates.

In other embodiments, the first image light is reflected to the polarizer by the first reflecting element and then reflected to the windshield by the polarizer; and when the second image light is reflected to the polarizing element through the second reflecting element, the second image light passes through the polarizing element, is reflected to the polarizing element by the third reflecting element after traveling to the third reflecting element, then travels to the windshield after passing through the polarizing element again.

Therefore, the multi-focal plane head-up display device provided by the invention can project two image lights with different polarization directions from the first area and the second area of the projector, and a plurality of reflecting components and polarizing elements are configured to design the light path through which the image lights pass, so that the two image lights can form two virtual images with different focal planes, and the volume occupied by the head-up display device can be reduced.

Drawings

FIG. 1 is a schematic diagram of a prior art single focal plane heads-up display device;

FIG. 2 is a schematic diagram of a prior art dual-projector dual-focal-plane heads-up display device;

FIG. 3 is a schematic diagram of a prior art single projector dual focal plane heads up display device;

fig. 4A is a schematic diagram of a head-up display device according to an embodiment of the invention;

FIG. 4B is a partial schematic view of a head-up display apparatus according to an embodiment of the invention;

FIG. 5A is a schematic virtual image of two different focal planes of a head-up display device according to an embodiment of the invention;

FIG. 5B is a schematic virtual image of two different focal planes of a head-up display device according to an embodiment of the invention;

FIG. 6 is a schematic diagram of a head-up display device according to an embodiment of the invention;

FIG. 7 is a schematic diagram of a head-up display device according to an embodiment of the invention;

FIG. 8 is a schematic diagram of a head-up display device according to an embodiment of the invention;

FIG. 9 is a schematic diagram of a head-up display device according to an embodiment of the invention;

FIG. 10 is a schematic diagram of a head-up display device according to an embodiment of the invention;

FIG. 11 is a schematic diagram of a head-up display device according to an embodiment of the invention; and

FIG. 12 is a diagram of a head-up display device according to an embodiment of the invention, illustrating different locations of the visible spots in the eye box corresponding to different areas of the mirror assembly.

Description of the symbols in the drawings:

1: main body

11: shell

12 light outlet

13, a containing space

2: projector

21 first phase delay element

22 second phase delay element

First linear polarizer 23

24 second linear polarizer

3, 3' first reflecting element

4, 4' second reflecting element

5, 5' polarizing element

6, 6' third reflecting element

7 reflective film

Angle A

E, E1, E2, E3 visual point

ER eye box

G is windshield

G11 first side

G12 second side

L1 first image light

L2 second image light

R1 first region

R2 second region

V1 first virtual image

V2 second virtual image

Detailed Description

The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

As shown in fig. 4A to 5B, a multi-focal plane head-up display device according to an embodiment of the present invention is suitable for being disposed on a transportation device, such as an automobile, an airplane, or the like. Specifically, the heads-up display of the present invention may be, for example and without limitation, mounted on the first side G11 of the windshield G of the transportation device. The first side G11 faces the user, while the second side G12 of the windshield G is opposite the first side G11 and faces the exterior of the transport equipment.

The multi-focal plane head-up display apparatus may include a main body 1, and the main body 1 includes a case 11 and a light outlet 12. The main body 1 is provided on the first side G11 of the windshield G, and faces the light exit 12 toward the windshield G. The main body 1 is provided with an accommodating space 13 to accommodate at least part of the components of the head-up display apparatus. At least some components of the head-up display apparatus will be exemplarily described below.

The multi-focal plane heads-up display device may include a projector 2, a first reflective element 3, a second reflective element 4, a polarizing element 5, and a third reflective element 6. The projector 2, the first reflective element 3, the second reflective element 4, the polarizing element 5, and the third reflective element 6 are disposed in the accommodating space 13 of the main body 1.

The projector 2 includes a first region R1 and a second region R2. In detail, the projector 2 is configured to project a light beam including a projection image, the projection image includes a first region R1 and a second region R2, and the light beam includes a first image light L1 corresponding to the first region R1 and a second image light L2 corresponding to the second region R2. The polarization directions of the first image light L1 and the second image light L2 are different. In other words, the projector 2 can project light with images from a single light source, for example, the images can be divided into two partial images corresponding to the first region R1 and the second region R2, respectively, so that the light projected by the projector 2 can be divided into a first image light with one partial image in the first region R1 and a second image light with the other partial image in the second region R2.

The first reflective element 3 can be, for example, a mirror for reflecting light. Specifically, the first reflective element 3 may be a curved mirror, for example.

The second reflective element 4 can be, for example, a mirror, for reflecting light. Specifically, the second reflective element 4 may be a curved mirror, for example.

The polarizing element 5 has a first side 51 and a second side 52 opposite to the first side 51. The first reflective element 3 and the second reflective element 4 are both disposed on the first side 51 of the polarizer 5. The polarizer 5 may be, for example, a reflective polarizer, for reflecting light in a first polarization direction and transmitting light in a second polarization direction different from the first polarization direction. Thus, the first image light L1 corresponding to the first polarization direction from the first reflective element 3 and the second image light L2 corresponding to the second polarization direction from the second reflective element 4 can be separated. More specifically, the polarizing element 5 may be, for example, a polarizing beam splitter or a polarizing beam splitting film. The polarizing element 5 may be, for example, a curved mirror.

The third reflective element 6 is arranged at the second side 52 of the polarizing element 5. The third reflective element 6 can be, for example, a mirror for reflecting light. Specifically, the third reflective element 6 may be a curved mirror, for example.

In this embodiment or other embodiments, the first region R1 of the projector 2, the first reflecting element 3, the polarizing element 5, and the windshield G are sequentially disposed on a first optical path, and the first optical path further extends from the windshield G to the eyes of the user (i.e., the viewing point E). The first image light L1 passes through the first optical path and is directed to the visual point E to form a first virtual image V1. Specifically, in an example, the first region R1 of the projector 2 projects the first image light L1 toward the first reflective element 3, and the first image light L1 is reflected by the first reflective element 3 to the polarizing element 5, is reflected by the polarizing element 5 to the light outlet 12, is emitted toward the windshield G, and is emitted toward the visual point E. At this time, the user can see the first virtual image V1, such as the first virtual image V1 shown in fig. 5A as a road sign, brought by the first image light L1.

The second region R2, the second reflection element 4, the polarization element 5, the third reflection element 6, and the windshield G of the projector 2 are sequentially disposed on a second optical path, and the second optical path further extends from the windshield G to the eyes of the user (i.e., the viewing point E). The second image light L2 passes through the second optical path and is directed to the visual point E to form a second virtual image V2. Specifically, in an example, the second region R2 of the projector 2 projects the second image light L2 toward the second reflective element 4, and the second image light L2 is reflected by the second reflective element 4 to the polarizing element 5, passes through the polarizing element 5, is directed to the third reflective element 6, is reflected by the third reflective element 6 to the polarizing element 5, passes through the polarizing element 5 again, is directed to the light exit 12, travels to the windshield G, and is directed to the visual point E. At this time, the user can see the second virtual image, such as the second virtual image V2 shown in fig. 5A as a function prompt, brought by the second image light L2.

In addition, in the present embodiment, the two image lights projected by the projector 2 have different polarization directions. For example, two image lights projected by the projector 2 implemented by using the lcd as a light source are both linearly polarized lights, and the projector 2 is disposed with a first phase retardation element 21, such as a half-wave plate, in the first region R1. In this case, when the angle between the polarization angle of the first image light L1 and the optical axis of the half-wave plate is set to be about 45 degrees, the first image light L1 passes through the first phase retardation element 21 to form a delayed image light with a polarization angle of 90 degrees, and the polarization direction of the delayed image light is substantially perpendicular to the polarization direction of the second image light L2. Similarly, the second phase delay element 22 may instead be disposed within the second region R2 of the projector 2, such as the second phase delay element 22 shown in fig. 4A. In this case, when the angle between the polarization angle of the second image light L2 and the optical axis of the second phase retardation element 22 is set to be about 45 degrees, the second image light L2 passes through the second phase retardation element 22 to form a delayed image light with the polarization angle deflected by 90 degrees, and the polarization direction of the delayed image light is substantially perpendicular to the polarization direction of the first image light L1.

Alternatively, for example, two image lights projected by the projector 2 implemented by a liquid crystal display are both linearly polarized lights, and the projector 2 is provided with the first phase retardation element 21, such as a half-wave plate, in the first region R1, and also provided with the second phase retardation element 22, such as a half-wave plate, in the second region R2. The half-wave plate has an optical axis, and when the angle between the polarization angle of the light and the optical axis of the half-wave plate is θ, the angle between the polarization angle of the output light and the polarization angle of the input light will be 2 θ. Such as the

phase delay elements

21 and 22 shown in fig. 7-11. In this case, when the angle α between the polarization angle of the first image light L1 and the optical axis of the first phase retarder 21 is set to about 22.5 degrees, and the angle β between the polarization angle of the second image light L2 and the optical axis of the second phase retarder 22 is set to about-22.5 degrees, the polarization angle of the first image light L1 is rotated by 45 degrees, the polarization angle of the second image light L2 is rotated by-45 degrees, and thus the polarization direction angle between the first image light and the second image light is 90 degrees. In practice, the angle α and the angle β may be of the same or different values, as long as | 2 α | 2 β | 90 is met.

Alternatively, as shown in fig. 6, in the example where the two image lights projected by the projector 2 implemented by Digital Light Processing (DLP) are non-linearly polarized lights, the projector 2 is provided with the first linear polarizer 23 in the first region R1 and the second linear polarizer 24 in the second region R2, and when the polarization angles of the first linear polarizer 23 and the second linear polarizer 24 are different by about 90 degrees, the polarization direction of the first polarized image Light formed by the first image Light L1 passing through the first linear polarizer 23 is substantially perpendicular to the polarization direction of the second polarized image Light formed by the second image Light L2 passing through the second linear polarizer 24.

However, the present invention is not limited to the above examples of utilizing the retardation elements and the linear polarizers to obtain a specific polarization of the image light projected by the projector 2, and the design of the related polarization angles, the types, the numbers and the arrangement positions of the retardation elements and the linear polarizers can be designed and selected according to the practical application.

In this embodiment or other embodiments, in order to make the image light image emitted to the windshield G be folded toward the viewing point E, the head-up display device may further include a reflective film 7, and the reflective film 7 is attached to the first side G11 of the windshield G. The reflective film 7 can be made of a transparent material, such as a semitransparent reflective film, so as to improve the reflectivity of the image light and not affect the user's view of the scenery or road conditions on the second side G12 of the windshield G. When the two image lights are reflected to the visible point E through the windshield G, the user can see two virtual focal plane images located on the second side G12 of the windshield G.

In this or other embodiments, the angle a between the polarizing element 5 and the third reflective element 6 is greater than 0 degrees, as shown in fig. 4B. Thus, the utilization rate of the accommodating space 13 of the main body 1 can be improved, and the size of the main body 1 can be reduced. In addition, the light outlet 12 is not shielded, and the size of the light outlet 12 can be further increased, thereby increasing the light output of the head-up display device.

In this embodiment or other embodiments, the relative positions of the polarization element 5 and the third reflective element 6 can be designed according to actual requirements. For example, as shown in fig. 4A and 7, the third reflective element 6 or 6 ' may be located near the upper side of the polarizing element 5 or 5 ' (above the polarizing element 5 or 5 ' in the drawing). Or, for example, as shown in fig. 6, the third reflective element 6 ' may be located close to and below the polarizing element 5 ' (below the polarizing element 5 ' in the drawing). Or, for example, the third reflective element may be located near the left or right side or middle of the polarizing element, etc. Therefore, the relative position of the polarization element and the third reflection element of the present invention is designed to only enable the first optical path and the second optical path to be interlaced, and avoid the optical paths to be parallel as much as possible, so as to reduce the crosstalk interference (crosstalk) between the optical paths.

In this embodiment or other embodiments, the relative positions of the first virtual image V1 and the second virtual image V2 can be adjusted according to the design of the position and size of each component in the main body 1. For example, in fig. 5A, the first virtual image V1 and the second virtual image V2 have a relative positional relationship of up and down or front and back, and V1 is above V2, or V2 is above V1. Alternatively, as shown in fig. 5B, the first virtual image V1 and the second virtual image V2 have a relative positional relationship in the left-right direction, with V1 to the left of V2 and V2 to the left of V1.

In this embodiment or other embodiments, the tilt angles of the image planes (i.e. the angles between the image planes and the horizon) of the first virtual image V1 and the second virtual image V2 can be designed according to the requirements of practical applications. Therefore, the graphics or characters such as marked lines, instructions or warnings displayed by the images can be attached to the actual road surface or scenery as much as possible, and the stereoscopic vision feeling is further enhanced.

Although the above embodiments have been described by taking the first reflective element 3, the second reflective element 4, the polarizer 5 and the third reflective element 6 as curved mirrors, the invention is not limited thereto. In other embodiments, as shown in fig. 8, the first reflective element 3' may be a flat mirror. In other embodiments, as shown in fig. 8, 9 and 11, the second reflective element 4' may also be a plane mirror. In other embodiments, as shown in fig. 6 and 7, the polarization element 5' may be a plane mirror. In other embodiments, as shown in fig. 6 and 7, the third reflective element 6 may also be a plane mirror. Therefore, the shapes and types of the first reflective element, the second reflective element, the polarizing element and the third reflective element in the invention can be designed and matched according to practical application.

On the other hand, the height of the sight line of each user is different, and the head and the body are not fixed during driving, so the size of the eye box ER must cover the change, and when the position of the eyes changes, the light path changes, so different areas of the mirror surface can be used. As shown by visibility points E1, E2, and E3 of fig. 12. The size of the optical mirror affects the design range of the eye box ER. The head-up display device of the present invention has the advantage of space utilization, can use a mirror assembly with enough size, and has a larger light outlet 12, so that the scope of the eye box can be maximized, and even if the position of eyes changes, the image picture can be continuously and completely presented to the user.

In the present invention, the content of the virtual image can be designed according to the requirements of the actual application. The first virtual image V1 may be used, for example, but not limited to, to display navigation instructions, driving assistance, lane lines, or safety warnings. The second virtual image V2 may be used, for example, but not limited to, to display vehicle speed, speed limit, gear, fuel amount, road name, etc. Moreover, the present invention does not limit the content presented in the virtual image to be text or graphics.

In summary, the head-up display apparatus provided by the present invention can project two image lights with different polarization directions from the first area and the second area of the projector, and the optical path along which the image light travels is designed by configuring the plurality of reflective assemblies and the reflective polarizer, so that the two image lights can form two virtual images with different focal planes, and the volume occupied by the head-up display apparatus can be reduced, thereby reducing the manufacturing cost. In addition, on the last light path emitted to the windshield, the reflective polarizing element is used for splitting light, and the third reflective element and the reflective polarizing element are arranged at relative positions, so that the volume occupied by the head-up display device is smaller, the light outlet cannot be shielded, the size of the light outlet can be increased, and the visible area of the eye box is enlarged. In summary, the above embodiments are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A multi-focal-plane heads-up display device, comprising:

the main body comprises a light outlet and an accommodating space, and the light outlet faces to the windshield;

the projector is arranged in the accommodating space and used for projecting light rays containing a projection picture, the projection picture comprises a first area and a second area, the light rays comprise first image light corresponding to the first area and second image light corresponding to the second area, and the polarization directions of the first image light and the second image light are perpendicular to each other;

the first reflecting element is arranged in the accommodating space;

the second reflecting element is arranged in the accommodating space;

a polarization element disposed in the accommodating space and having a first side and a second side opposite to the first side, wherein the first reflection element and the second reflection element are disposed on the first side of the polarization element, and the polarization element can allow one of the first image light and the second image light to penetrate therethrough and allow the other of the first image light and the second image light to reflect; and

the third reflection element is arranged in the accommodating space and located on the second side of the polarization element, the first area of the projector, the first reflection element, the polarization element and the windshield are sequentially arranged on a first light path, the first image light passes through the first light path and enters the human eyes to form a first virtual image, the second area of the projector, the second reflection element, the polarization element, the third reflection element and the windshield are sequentially arranged on a second light path, and the second image light passes through the second light path and enters the human eyes to form a second virtual image.

2. The multi-focal-plane heads-up display device of claim 1, wherein the angle of the polarizing element to the third reflective element is greater than 0 degrees.

3. The multi-focal-plane heads-up display device of claim 1, wherein the polarizing element is a polarizing beam splitter or a polarizing beam splitting film.

4. The multi-focal-plane heads-up display device of claim 1, wherein the first image light and the second image light projected by the projector are linearly polarized light, the heads-up display device further comprising a first phase retardation element disposed in the first region, the first image light passing through the first phase retardation element to form a delayed image light, and a polarization direction of the delayed image light is perpendicular to a polarization direction of the second image light.

5. The multi-focal-plane heads-up display device of claim 1, wherein the first image light and the second image light projected by the projector are linearly polarized light, the heads-up display device further comprising a second phase retardation element disposed in the second region, the second image light passing through the second phase retardation element to form a delayed image light, and a polarization direction of the delayed image light is perpendicular to a polarization direction of the first image light.

6. The multi-focal-plane heads-up display device of claim 1, wherein the first image light and the second image light projected by the projector are linearly polarized light, the heads-up display device further comprising a first phase retardation element and a second phase retardation element, the first phase retardation element is disposed in the first region, the second phase retardation element is disposed in the second region, the first image light and the second image light respectively pass through the first phase retardation element and the second phase retardation element to form two delayed image lights, and a polarization direction of the delayed image light of the first image light and a polarization direction of the delayed image light of the second image light are perpendicular to each other.

7. The multi-focal-plane heads-up display device of claim 4, 5 or 6, wherein the first and second phase retardation elements are half-wave plates.

8. The multi-focal-plane head-up display device of claim 1, wherein the first image light and the second image light projected by the projector have no specific polarization, the head-up display device further comprising a first linear polarizer and a second linear polarizer, the first linear polarizer is disposed in the first region, the second linear polarizer is disposed in the second region, and the first image light and the second image light form linear polarized lights with polarization directions perpendicular to each other after passing through the first linear polarizer and the second linear polarizer, respectively.

9. The multi-focal-plane heads-up display device of claim 1, wherein at least one of the first reflective element, the second reflective element, the polarizing element, and the third reflective element is a curved mirror.

10. The multi-focal-plane heads-up display device of claim 1, wherein the first image light is reflected by the first reflecting element to the polarizing element and then reflected by the polarizing element to the windshield; and when the second image light is reflected to the polarizing element through the second reflecting element, the second image light passes through the polarizing element, is reflected to the polarizing element by the third reflecting element after traveling to the third reflecting element, then travels to the windshield after passing through the polarizing element again.