CN115268068A - Stereoscopic head-up display device using two directional backlit displays - Google Patents

Abstract

The invention discloses a naked-eye three-dimensional head-up display device, which comprises a directional backlight display, a first reflecting element, a second reflecting element, a third reflecting element and a light splitting element. The directional backlight display provides two image lights having directivity, and the two image lights are parallax image lights to be respectively incident to both eyes of an observer. One of the directional backlight type display, the first reflecting element and one of the light splitting element, the windshield and the two eyes form a first light path. The other directional backlight type display, the second reflecting element, the light splitting element and the other one of the third reflecting element, the windshield and the two eyes form a second light path. The two image lights are respectively incident to two eyes through the first and second light paths to form a stereoscopic image.

Description

Stereoscopic head-up display device utilizing two directional backlight displays

technical field

The invention relates to a head-up display, in particular to a naked-view stereoscopic head-up display device utilizing two directional backlight displays.

Background technique

In the existing head-up display technology, digital light processing (DigitalLight Processing, DLP) projection display of reflective display or TFT-LCD of backlight display can be used, but the structure of DLP projection display is complicated, The cost is high and the size is large. If it is to achieve the same resolution as the LCD screen, the price is even more expensive. Therefore, the LCD screen is a better choice for taking into account small size, low cost, high contrast and high resolution.

Common naked-view 3D technologies using LCD screens can be divided into using lenticular lenses and using parallax barriers. As shown in FIG. 1A , the lenticular lens method utilizes the focusing and light refraction of closely arranged lenticular lenses to change the traveling direction of the image light, achieving the effect of splitting the left and right eye images. As shown in FIG. 1B , the parallax barrier uses vertical grating linear stripes alternated by light-transmitting slits and opaque barriers to limit the traveling route of image light, achieving the effect of light separation of left and right eye images.

Both the lenticular lens type and the parallax barrier type need to divide the image information into equidistant vertical strips, and then interleave the left-eye image and right-eye image in an interleaving manner, which causes the disadvantage of halving the horizontal resolution. Furthermore, the alignment accuracy between the pixels on the LCD panel is extremely high, so the problem of poor separation between the left and right eyes is prone to occur. Moreover, the parallax barrier technology has the disadvantage of halving the brightness. These all affect the visual quality.

Therefore, a naked-view 3D head-up display using two LCD screens can avoid the aforementioned disadvantages of halving the resolution, requiring high alignment accuracy, and halving the brightness. In the existing dual-screen liquid crystal screen head-up display technology, as shown in Figure 2A, a liquid crystal screen P0 for projecting image light is divided into two areas, and these two areas project two image lights respectively, or as shown in Figure 2A As shown in 2B, two liquid crystal screens P1 and P2 are used to project two image lights respectively. These two image lights are incident to the eyes of the viewer through their optical paths, and form virtual images V1 and V2 located in front of the windshield with two different focal planes, as shown in FIG. 3 .

As shown in Figure 4, in order to present naked-view stereoscopic images, the head-up display uses two liquid crystal screens P1 and P2 to respectively project parallax image light for the left eye and right eye, with two independent concave mirrors A1 and A2 for light splitting and Adjust the magnification so that the two parallax virtual images V1 and V2 in front of the windshield are imaged at the same or similar distance, projected on the viewer's left eye and right eye respectively, and synthesize stereoscopic images in the viewer's mind to achieve naked View the effect of 3D. However, the optical design of this stereoscopic vision image will cause the eye box to be too large due to the wide viewing angles of the LCD screens P1 and P2, and the isolation between the two approximately parallel light paths is not good, resulting in light leakage and crosstalk (Cross Talk) problems that seriously affect the visual quality of viewing.

Contents of the invention

For this reason, the main purpose of the present invention is to provide a naked-view stereoscopic head-up display device utilizing two directional backlight displays. With the use of directional backlight displays, a single eye box can only cover a single eye, and the interlaced The unique optical path design solves the problems of light leakage and crosstalk caused by poor optical path isolation.

According to an embodiment of the present invention, a naked-view stereoscopic head-up display device utilizing two directional backlight displays includes: a first directional backlight display for providing a directional first image light ; A second directional backlight display, used to provide a directional second image light, the first image light and the second image light are the parallax image light of one eye and the other eye respectively; a first reflective element ; a second reflective element; a third reflective element; and a light splitting element disposed between the first reflective element and the second reflective element and the third reflective element. A first optical path is formed by the first directional backlight display, the first reflective element, the light splitting element, a windshield and one of the eyes of a viewer. The first image light projected by the first directional backlight display enters one of the two eyes through the first light path to form a parallax virtual image. The second directional backlight display, the second reflective element, the light splitting element, the third reflective element, the windshield and the other eye of the eyes form a second light path. The second image light projected by the second directional backlight display enters the other eye through the second light path to form another parallax virtual image. The two parallax virtual images jointly form a stereoscopic image in the viewer's mind (visually).

In some embodiments of the present invention, the first light path and the second light path are not parallel but intersect between the light splitting element and the first reflective element and the second reflective element.

In some embodiments of the present invention, the first light path and the second light path are not parallel and do not intersect between the light splitting element and the first reflective element and the second reflective element.

In some embodiments of the present invention, the first optical path and the second optical path are between the first directional backlit display and the second directional backlit display and the first reflective element and the second reflective element are not parallel and will intersect.

In some embodiments of the present invention, the first optical path and the second optical path are between the first directional backlit display and the second directional backlit display and the first reflective element and the second reflective element Not parallel and not intersecting.

In some embodiments of the present invention, the light paths of the first light path and the second light path before reaching the windshield are at least partially non-overlapping, and are non-parallel and intersecting or non-parallel and non-intersecting.

In some embodiments of the present invention, the light splitting element is a reflective polarizer, and the first image light and the second image light passing through the light splitting element are image lights whose polarization directions are perpendicular to each other.

In some embodiments of the present invention, the light splitting element is a half mirror, and the first image light and the second image light passing through the light splitting element are non-polarized image light.

In some embodiments of the present invention, the distance between the first directional backlight display and the first reflective element is D1, the distance between the second directional backlight display and the second reflective element is D2, and the first The distance from the reflective element to the light-splitting element is S1, the distance from the second reflective element to the third reflective element is S2, the distance from the light-splitting element to the windshield is R1, and the distance from the third reflective element to the windshield is The distance is R2, the magnification of the light-splitting element is A1, the magnification of the third reflective element is A2, the magnification of the windshield is GA, and the naked-view stereoscopic head-up display device meets the following conditions:

[(D1+S1)×A1+R1]×GA=[(D2+S2)×A2+R2]×GA

In some embodiments of the present invention, each of the first directional backlight display and the second directional backlight display includes a liquid crystal panel and a directional backlight.

In some embodiments of the present invention, the first directional backlight display projects the first image light to the first reflective element, and the first reflective element reflects the first image light to the light splitting element, and the light splitting element reflecting the first image light to the windshield, and the windshield reflects the first image light to the one of the eyes to form the parallax virtual image; and the second directional backlight display projects the The second image light reaches the second reflective element, the second reflective element reflects the second image light to the light splitting element, and the second image light passes through the light splitting element to the third reflective element, the second image light The light is reflected by the third reflective element and then passes through the light splitting element to the windshield, and the windshield reflects the second image light to the other eye to form another parallax virtual image.

Therefore, the naked-view stereoscopic head-up display device provided by the present invention using two directional backlight displays, combined with the staggered optical path design, can improve the isolation between the optical paths, thereby avoiding light leakage and crosstalk.

Description of drawings

Other aspects of the invention and its advantages will be discovered after studying the detailed description in conjunction with the following drawings:

FIG. 1A is a schematic diagram of the architecture of an existing lenticular-type liquid crystal screen naked-view 3D display;

FIG. 1B is a schematic diagram of the architecture of an existing parallax-barrier liquid crystal screen naked-view 3D display;

FIG. 2A is a schematic structural diagram of an existing dual-screen liquid crystal screen head-up display;

FIG. 2B is a structural schematic diagram of another existing dual-screen liquid crystal screen head-up display;

Fig. 3 is a schematic diagram showing two virtual images in front of the windshield on the existing dual-screen liquid crystal screen head-up display;

Fig. 4 is a schematic diagram of the structure of the existing dual liquid crystal screen naked-view stereoscopic head-up display;

5 is a schematic diagram of a naked-view stereoscopic head-up display device using two directional backlight displays according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of the structure of a display using a side-illuminated light source with a directional backlight;

FIG. 7 is a schematic diagram of the structure of a display adopting a point array light source with a directional backlight;

FIG. 8A is a schematic diagram of the image light of the directional backlight display in FIG. 5 entering the right eye through its optical path;

FIG. 8B is a schematic diagram of the right eye box where the image light in FIG. 8A is projected to the right eye;

9A is a schematic diagram of the image light of the non-directional backlight display entering the right eye through its optical path;

FIG. 9B is a schematic diagram of the right eye box where the image light in FIG. 9A is projected to the right eye;

10 is a schematic diagram of light leakage or crosstalk caused by a part of the second image light being reflected by a reflective polarizer as a light splitting element;

11 is a schematic diagram of a single interleaved optical path design formed by the first optical path and the second optical path according to an embodiment of the present invention;

Fig. 12 is a schematic diagram of a double interlaced optical path design formed by the first optical path and the second optical path according to an embodiment of the present invention;

Fig. 13 is a schematic diagram of an interlaced optical path using a half mirror as a light splitting element according to an embodiment of the present invention;

Fig. 14 is a schematic diagram showing equal distances from two parallax virtual images to the windshield according to an embodiment of the present invention;

15 is a schematic diagram of two parallax virtual images forming a stereoscopic image with zero parallax according to an embodiment of the present invention;

FIG. 16 is a schematic diagram of a stereoscopic image composed of two parallax virtual images according to an embodiment of the present invention;

17 is a schematic diagram of a stereoscopic image with negative parallax formed by two virtual parallax images according to an embodiment of the present invention;

18 is a schematic diagram of a first optical path and a second optical path that are not parallel to each other but intersect according to an embodiment of the present invention; and

Fig. 19 is a schematic diagram of a first optical path and a second optical path that are not parallel to each other and do not intersect each other according to an embodiment of the present invention.

in:

11: The first directional backlight display;

12: Second directional backlight display;

13,14: non-directional backlight display;

21: the first reflective element;

22: the second reflective element;

31: light splitting element;

32: the third reflective element;

4: Windshield;

5: Semi-penetrating reflective film;

A1, A2: concave mirror;

BL1: side light source;

BL2: point array light source;

CL: convex lens array;

E1, E2: eye box;

EYES: The eyes of the viewer;

GP: light guide plate;

IM1, IM1': the first image light;

IM2, IM2', IM2": the second image light;

L1: the first optical path;

L2: the second optical path;

L3: light path;

LE: left eye;

P0, P1, P2: LCD screen;

PA1, PA2: LCD panel;

RE: right eye;

RF: reset redirection membrane;

SV: Stereo vision image;

V1, V2: virtual image;

V3, V4, V4': parallax virtual image.

Detailed ways

Please refer to Fig. 5, a naked-view stereoscopic head-up display device utilizing two directional backlight displays according to an embodiment of the present invention, which includes a first directional backlight display 11, a second directional A non-reactive backlight display 12 , a first reflective element 21 , a second reflective element 22 , a light splitting element 31 and a third reflective element 32 . The positions of these elements can be arranged, for example, as shown in FIG. 5 , the light splitting element 31 is located between the first directional backlight display 11 and the second directional backlight display 12 and the third reflective element 32 .

The first directional backlight display 11 is used for providing a directional first image light IM1. The second directional backlight display 12 is used for providing a directional second image light IM2. The first image light IM1 and the second image light IM2 are parallax image lights to be respectively incident on the eyes of a viewer. The first directional backlight display 11 and the second directional backlight display 12 may, for example but not limited to, each include a liquid crystal panel and a directional backlight. For example, the liquid crystal panels used in the first directional backlight display 11 and the second directional backlight display 12 can be twisted nematic liquid crystal (Twisted Nematic, TN), vertical alignment liquid crystal (Vertical Alignment, VA ), in-plane switching liquid crystal (In-Plane Switching, IPS) or any liquid crystal panel that requires an external light source instead of a self-illuminating liquid crystal panel. The backlight used by the first directional backlight display 11 and the second directional backlight display 12, as shown in FIG. The light guide plate (Light Guide Plate) GP, together with the redirecting film (Redirecting Film) RF with a prismatic structure, allows the light to go straight through the liquid crystal panel PA1, presenting image light with high directivity and narrow viewing angle. Or, as shown in FIG. 7, the backlight source can be a point-array light source BL2 used in another prior art, which is combined with a convex lens array (Convex Lens Array) CL to allow the light to go straight through the liquid crystal panel PA2, presenting high directivity. Narrow viewing angle image light.

In this embodiment, both the first reflective element 21 and the second reflective element 22 are planes, but the present invention is not limited to this embodiment; in other embodiments, the first reflective element 21 and the second reflective element 22 are also planar Both may be curved surfaces; or, one of the first reflective element 21 and the second reflective element 22 is a plane, and the other of the first reflective element 21 and the second reflective element 22 is a curved surface.

In this embodiment, both the light splitting element 31 and the third reflective element 32 are curved surfaces, but the present invention is not limited to this embodiment; in other embodiments, the light splitting element 31 and the third reflective element 32 can also be both flat surfaces or, one of the light splitting element 31 and the third reflective element 32 is a plane, and the other one of the light splitting element 31 and the third reflective element 32 is a curved surface.

In this embodiment, the light splitting element 31 is a reflective polarizer. Under this premise, the first image light IM1 and the second image light IM2 passing through the light splitting element 31 are image lights whose polarization directions are perpendicular to each other.

The first directional backlight display 11 , the first reflective element 21 , the light splitting element 31 , the windshield 4 and one of the viewer's eyes EYES form a first light path L1 . In detail, the first directional backlight display 11 projects the first image light IM1 to the first reflective element 21, the first reflective element 21 reflects the first image light IM1 to the light splitting element 31, and the light splitting element 31 transforms the first image light IM1 The IM1 is reflected to the windshield 4, and the windshield 4 reflects the first image light IM1 to one of the viewer's eyes EYES (such as but not limited to the left eye) to form a parallax virtual image.

The second directional backlight display 12 , the second reflective element 22 , the light splitting element 31 , the third reflective element 32 , the windshield 4 and the other eye of the viewer's eyes EYES form a second optical path L2 . In detail, the second directional backlight display IM2 projects the second image light IM2 to the second reflective element 22, the second reflective element 22 reflects the second image light IM2 to the spectroscopic element 31, and the second image light IM2 passes through the spectroscopic element 31. After the element 31 reaches the third reflective element 32, the second image light IM2 is reflected by the third reflective element 32 and then penetrates the light splitting element 31 to the windshield 4, and the windshield 4 reflects the second image light IM2 to the viewer The other eye (such as but not limited to the right eye) of the binocular EYES to form another parallax virtual image.

The optical paths of the first optical path L1 and the second optical path L2 before reaching the windshield 4 are at least partially non-overlapping, as shown in FIG. 14 , and they are not parallel and intersect each other or are not parallel and intersect.

In this way, the two image lights provided by the two directional backlight displays can allow the left eye and right eye of the viewer's binocular EYES to see the two parallax virtual images V3 and V4 respectively (that is, the parallax virtual image of the left eye and the virtual image of the right eye). parallax virtual image), visually (that is, in the viewer's mind) to synthesize a stereoscopic image SV. Visually, the stereoscopic image SV is like an image appearing in front of the windshield 4 (that is, the viewer's binocular EYES and the stereoscopic image SV are respectively located on opposite sides of the windshield 4 ).

Taking the example shown in Figure 6 and Figure 7 as the directional backlight display of the present invention, as shown in Figure 8A and 8B, the full width at half maximum ( Full Width at Half Maximum (FWHM) is about ±5°～±10°, which narrows the viewing angle of the display screen, allowing each pixel of the display screen to pass through the projection, reflection and amplification of the optical path (such as the second optical path L2) Subsequent eye boxes (such as eye box E1) will only cover one eye (such as the right eye RE), but will not cover the other eye (such as the left eye LE). Moreover, the width of the eye box at which the image displayed by each directional backlight display is projected at the distance of the viewer's EYES can be approximately the distance between the pupils of the two eyes, that is, about 6.5-7.0 cm.

Compared with the use of the directional backlight display in the present invention, if the directional backlight display of FIG. 8A is replaced by the commonly used non-directional backlight displays 13 and 14 shown in FIG. 9A, the output light field of the backlight source The FWHM is about ±30°～±60°, so the viewing angle of the display screen is wider, but it also causes the eye box E2 after each pixel of the display screen is projected, reflected and enlarged by the optical path L3 to be too large, as shown in Figure 9B As shown, not only one eye (eg, right eye RE) is projected, but the other eye (eg, left eye LE) is also covered. Therefore, both the left eye and the right eye will see the same parallax virtual image, which causes the disadvantage of crosstalk and affects the effect of the stereoscopic image.

In addition, in this embodiment or other embodiments, the light splitting element 31 is a reflective polarizer. As shown in FIG. 10 , the first image light IM1 and the second image light IM2 are two polarized image lights with polarization directions perpendicular to each other. The first image light IM1 is reflected by the light splitting element 31 and projected to the windshield 4 , while the second image light IM1 The second image light IM2 passes through the light-splitting element 31 for the first time and is reflected by the third reflective element 32 , so that the second image light IM2 passes through the light-splitting element 31 for the second time, and then projects to the windshield 4 . However, the transmittance of the light splitting element 31 for the second image light IM2 is not 100%. Although most of the second image light IM2 will pass through the light splitting element 31, a small part of the second image light IM2 is still transmitted by the light splitting element 31. Reflected to the windshield 4, resulting in incomplete light separation. If the first optical path L1 of the first image light IM1 and the second optical path L2 of the second image light IM2 are approximately parallel optical paths, and the incident angles at the light splitting element 31 are similar, a small part of the second image light reflected by the light splitting element 31 IM2 (i.e. image light IM2') enters either eye of the viewer's binocular EYES after being reflected by the windshield 4, forming another parallax virtual image V4', so one of them will see two identical parallax virtual images V4( Target virtual image), light leakage problem of V4', or the crosstalk problem between two different parallax virtual images V3 (target virtual image) and V4' seen by the other eye.

In order to solve the above-mentioned light leakage and crosstalk problems, in this embodiment or other embodiments, as shown in FIG. 5 and FIG. The elements 22 are non-parallel but intersecting (as shown in FIG. 18 ), or non-parallel and non-intersecting (as shown in FIG. 19 ), forming a single interlaced optical path design. Thereby, the difference of the incident angles of the two light paths at the light splitting element 31 can be increased, so as to improve the isolation between the light paths. Even if the second image light IM2 of the second optical path L2 has a small part of the image light IM2' reflected on the light-splitting element 31, the incident angle of the optical path at the light-splitting element 31 is different from the incident angle of the first light path L1 at the light-splitting element 31. There is a large difference in angle, and it will not enter either eye of the viewer's eyes, so as to avoid the problems of light leakage and crosstalk. Moreover, such an optical path can be combined with a directional backlight display to become an optical path design with double isolation.

In order to increase the isolation between the light paths, in another embodiment, the first light path L1 and the second light path L2 can be further connected between the first directional backlight display 11 and the second directional backlight display 12 and the first reflective element 21 and the second reflective element 22 may also be non-parallel but intersect, or non-parallel and non-intersect, as shown in FIG. 12 . In this way, the incident angle difference between the two light paths on the corresponding reflective elements is increased, and the isolation between the light paths is strengthened, resulting in a double interlaced light path design, coupled with the use of a directional backlight display, it becomes a triple isolation light path design.

In addition to the reflective polarizer, the light splitting element 31 can also be a half-reflecting mirror (such as half-reflecting and half-transmitting), as shown in FIG. The light, for example, can be non-polarized image light, which can also achieve a good splitting effect. The first image light IM1 on the first optical path L1 is partially reflected by the light splitting element 31 to the windshield 4, and then reflected to one of the viewer's eyes EYES, and the first image light IM1' that partially penetrates the light splitting element 31 is due to The difference in the angle of the light path will not enter either eye of the viewer's eyes EYES. Part of the second image light IM2 on the second optical path L2 first passes through the light splitting element 31 to reach the third reflective element 32, and the second image light IM2' partially reflected by the light splitting element 31 will not enter the viewer due to the difference in the angle of the light path. Any eye of the binocular EYES; part of the second image light IM2 that penetrates the light splitting element 31 for the first time continues to advance in the direction of the designed light path, and after being reflected by the third reflective element 32, part of the second image light IM2 penetrates the light splitting element 31 and reaches the stop The windshield 4 is projected to the other eye of the viewer's eyes EYES again, and the second image light IM2 "partially reflected by the light splitting element 31 will not enter any eye of the viewer's eyes EYES due to the difference in light path angle; the left eye, The parallax image of the right eye is projected on the viewer's left eye and right eye respectively, and a stereoscopic image is synthesized in the mind to achieve the naked-view 3D effect.

In each embodiment of the present invention, the naked-view stereo head-up display device may better meet the following conditions:

[(D1+S1)×A1+R1]×GA=[(D2+S2)×A2+R2]×GA

As shown in Figure 14, wherein, the distance from the first directional backlight display 11 to the first reflective element 21 is D1, the distance from the second directional backlit display 12 to the second reflective element 22 is D2, and the first reflective element 21 to the light splitting element 31 is S1, the distance from the second reflective element 22 to the third reflective element 32 is S2, the distance from the light splitting element 31 to the windshield 4 is R1, the third reflective element 32 to the windshield 4 The distance is R2, the magnification of the light splitting element 31 is A1, the magnification of the third reflective element 32 is A2, and the magnification of the windshield 4 is GA. In this way, the above-mentioned two virtual parallax images V3 and V4 for the left and right eyes are at the same distance from the windshield 4 , thereby forming a stereoscopic image in the viewer's mind.

In each embodiment of the present invention, the staggered offset degree of the first optical path L1 and the second optical path L2 projected to the viewer's binocular EYES will affect the relative position of the left eye parallax virtual image and the right eye parallax virtual image, so it can be adjusted according to the function Need to adjust the design of the first light path L1 and the second light path L2, so that the two parallax virtual images V3 and V4 of the left and right eyes are superimposed together, and the stereoscopic vision image SV in the mind of the viewer will be at the position of the virtual image, and the distance from the virtual image is the same. At this time, it is Zero Parallax, as shown in FIG. 15 . Alternatively, the two parallax virtual images V3 and V4 of the left and right eyes can be partially superimposed, the virtual image of the left eye is offset to the left, and the virtual image of the right eye is offset to the right, so that the stereoscopic vision image SV in the mind of the viewer will be behind the position of the virtual image. It is farther than the virtual image distance, which is positive parallax (Positive Parallax), as shown in Figure 16. Alternatively, the two parallax virtual images V3 and V4 of the left and right eyes can be partially overlapped, the virtual image of the left eye is offset to the right, and the virtual image of the right eye is offset to the left. The virtual image distance is even closer, and at this time it is negative parallax (Negative Parallax), as shown in Figure 17.

In various embodiments of the present invention, the autostereoscopic head-up display device further includes a half-transmitting reflective film 5 disposed on the windshield 4 , as shown in FIG. 5 . The transflective film is used to reflect the first image light IM1 and the second image light IM2 to the left eye and the right eye of the viewer's eyes EYE respectively. Thereby, the reflectivity of screen projection can be improved.

Although the present invention is disclosed above with the aforementioned embodiments, these embodiments are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, all changes, modifications and combinations of implementations are within the scope of patent protection of the present invention. For the scope of protection defined by the present invention, please refer to the appended scope of patent application.

Claims (10)

1. A naked-eye stereoscopic heads-up display device using two directional backlight displays, comprising:

a first directional backlight display for providing a first image light with directivity;

a second directional backlight display for providing a second image light having directivity, the first image light and the second image light being parallax image light to be incident to both eyes of an observer, respectively;

a first reflective element;

a second reflective element;

a third reflective element; and

a light splitting element disposed between the first reflective element and the second reflective element and the third reflective element,

wherein the first directional backlight display, the first reflection element, the beam splitting element, a windshield and one of the two eyes form a first light path, and the first image light projected by the first directional backlight display is incident to the one of the two eyes through the first light path to form a parallax virtual image;

the second directional backlight type display, the second reflecting element, the light splitting element, the third reflecting element, the windshield and the other of the two eyes form a second light path, the second image light projected by the second directional backlight type display enters the other of the two eyes through the second light path to form another parallax virtual image, and the two parallax virtual images form a stereoscopic vision image on the vision of the viewer; and

the first optical path and the second optical path are not parallel between the light splitting element and the first reflective element and the second reflective element.

2. The head-up display apparatus according to claim 1, wherein the first and second light paths intersect between the beam splitting element and the first and second reflective elements.

3. The device of claim 1, wherein the first and second optical paths do not intersect between the beam splitting element and the first and second reflective elements.

4. The device of claim 1, wherein the first and second optical paths are non-parallel and intersect between the first and second directional backlit displays and the first and second reflective elements.

5. The device of claim 1, wherein the first and second light paths are non-parallel and non-intersecting between the first and second directional backlit displays and the first and second reflective elements.

6. The device of claim 1, wherein the first and second light paths are at least partially non-overlapping and non-parallel before reaching the windshield.

7. The device of any of claims 1-6, wherein the beam splitter is a reflective polarizer, and the first image light and the second image light traveling to the beam splitter are image lights with polarization directions perpendicular to each other.

8. The device as claimed in any one of claims 1 to 6, wherein the beam splitter is a half mirror, and the first image light and the second image light passing through the beam splitter are unpolarized image lights.

9. The device according to any one of claims 1 to 6, wherein a distance between the first directional backlight display and the first reflective element is D1, a distance between the second directional backlight display and the second reflective element is D2, a distance between the first reflective element and the beam splitter element is S1, a distance between the second reflective element and the third reflective element is S2, a distance between the beam splitter element and the windshield is R1, a distance between the third reflective element and the windshield is R2, a magnification of the beam splitter element is A1, a magnification of the third reflective element is A2, and a magnification of the windshield is GA, the device meets the following conditions:

[(D1+S1)×A1+R1]×GA＝[(D2+S2)×A2+R2]×GA。

10. the device as claimed in claim 1, wherein the first directional backlight display and the second directional backlight display each comprise a liquid crystal panel and a directional backlight.

Images