CN115268068A - Naked-eye stereoscopic head-up display device using two directional backlight 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

Naked-eye stereoscopic head-up display device using two directional backlight displays

Technical Field

The present invention relates to a head-up display, and more particularly, to a head-up display device using two directional backlight displays.

Background

In the conventional head-up display technology, a Digital Light Processing (DLP) projection display of a reflective display or a thin film transistor liquid crystal display (TFT-LCD) of a backlight display can be used, but the DLP projection display has a complex structure, high cost and large volume, and if the DLP projection display is required to reach the same resolution specification as the liquid crystal display, the cost is more expensive, so the liquid crystal display is a better choice for considering small volume, low cost, high contrast and high resolution.

A common naked-eye 3D technology using a liquid crystal screen can be divided into a Lenticular lens (lenticulars) and a Parallax barrier (paralax barrier). As shown in fig. 1A, the lenticular lens changes the moving direction of the image light by the focusing and light refraction of the closely arranged lenticular lenses, so as to achieve the effect of left and right eye image light splitting. As shown in fig. 1B, the parallax barrier uses the longitudinal grating straight stripes between the transparent slits and the opaque barrier to limit the moving path of the image light, so as to achieve the effect of splitting the left and right eye images.

Both lenticular and parallax barrier systems require that the image information be divided into vertical stripes at equal distances and then the left-eye image and the right-eye image are interlaced in a line-by-line manner, thereby resulting in a half-reduced horizontal resolution. Moreover, the alignment precision between pixels on the liquid crystal panel is extremely high, so that the problem of poor left-right eye separation is easily caused. Furthermore, the parallax barrier technology has a disadvantage of halving the brightness. These all affect the visual quality.

Therefore, the naked-eye 3D head-up display using two liquid crystal screens can avoid the defects of halving resolution ratio, high alignment precision requirement and halving brightness. In the conventional dual-screen lcd head-up display technology, as shown in fig. 2A, one lcd panel P0 for projecting image light is divided into two regions, and the two regions project two image lights respectively, or as shown in fig. 2B, two lcd panels P1 and P2 are used to project two image lights respectively. These two image lights are incident to both eyes of the viewer via their optical paths to form virtual images V1 and V2 at two different focal planes in front of the windshield, as shown in fig. 3.

As shown in fig. 4, in order to present a naked-eye stereoscopic image, the head-up display uses two liquid crystal screens P1 and P2, which respectively project parallax image light of left and right eyes, and matches the light splitting and magnification adjustment of two independent concave mirrors A1 and A2, so that two parallax virtual images V1 and V2 in front of the windshield are imaged at the same or similar distance and respectively projected to the left and right eyes of the viewer, and the stereoscopic image is synthesized in the mind of the viewer, thereby achieving the naked-eye 3D effect. However, in the optical design of the stereoscopic image, the wide viewing angle of the liquid crystal screens P1 and P2 causes the eye box to be too large, and the isolation between the two approximately parallel light paths is not good, which causes the problems of light leakage and crosstalk (Cross Talk), and seriously affects the viewing quality.

Disclosure of Invention

Therefore, the main objective of the present invention is to provide a naked-eye stereoscopic head-up display device using two directional backlight displays, wherein a single eye box only covers a single eye by using the directional backlight displays, and the problem of light leakage and crosstalk caused by poor optical path isolation is solved by using a staggered optical path design.

According to an embodiment of the present invention, a head-up display device for naked eye stereoscopic display using two directional backlight displays comprises: a first directional backlight display for providing a first image light with directivity; a second directional backlight display for providing a second image light with directivity, the first image light and the second image light being 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 arranged between the first reflecting element and the third reflecting element. The first directional backlight type display, the first reflecting element, the light splitting element, the windshield and one of the eyes of an observer form a first light path. The first image light projected by the first directional backlight type display is incident to 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 is incident to the other eye through the second light path to form another parallax virtual image. The two parallax virtual images together form a stereoscopic image in the mind of the viewer (visually).

In some embodiments of the present invention, the first optical path and the second optical path are not parallel and 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 non-parallel and non-intersecting between the light splitting element and the first reflective element and the second reflective element.

In some embodiments of the present invention, 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.

In some embodiments of the present invention, the first and second optical paths are non-parallel and non-intersecting between the first and second directional backlit displays and the first and second reflective elements.

In some embodiments of the invention, the optical paths of the first and second optical paths before reaching the windshield are at least partially non-overlapping and are non-parallel to each other and may or may not intersect.

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 with polarization directions 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 traveling to the light-splitting element are unpolarized image light.

In some embodiments of the present invention, 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, a magnification of the windshield is GA, and the naked-view stereoscopic heads-up display device meets the following conditions:

[(D1+S1)×A1+R1]×GA＝[(D2+S2)×A2+R2]×GA

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

In some embodiments of the invention, the first directional backlight display projects the first image light to the first reflecting element, the first reflecting element reflects the first image light to the light splitting element, the light splitting element reflects the first image light to the windshield, and the windshield reflects the first image light to one of the two eyes to form the parallax virtual image; and the second directional backlight type display projects the second image light to the second reflection element, the second reflection element reflects the second image light to the light splitting element, the second image light penetrates through the light splitting element and then reaches the third reflection element, the second image light penetrates through the light splitting element again after being reflected by the third reflection element and then reaches the windshield, and the windshield reflects the second image light to the other eye to form the other virtual image.

Therefore, the naked-eye three-dimensional head-up display device utilizing the two directional backlight displays provided by the invention can improve the isolation between the light paths by matching with the staggered light path design, thereby avoiding light leakage and crosstalk.

Drawings

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

FIG. 1A is a schematic diagram of a conventional lenticular LCD naked 3D display;

FIG. 1B is a schematic diagram of a conventional parallax barrier type LCD screen naked-eye 3D display;

FIG. 2A is a schematic diagram of a conventional dual-panel LCD head-up display;

FIG. 2B is a schematic diagram of another conventional dual-panel LCD head-up display;

FIG. 3 is a schematic diagram of a conventional dual-panel LCD head-up display showing two virtual images in front of a windshield;

FIG. 4 is a schematic diagram of a conventional dual-LCD naked-eye stereoscopic head-up display;

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

FIG. 6 is a schematic diagram of a display using a side-entry light source directional backlight;

FIG. 7 is a schematic diagram of a display architecture employing a point array light source directional backlight;

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

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

FIG. 9A is a schematic diagram of image light incident to the right eye through the light path of the non-directional backlight display;

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

FIG. 10 is a schematic diagram of a portion of the second image light reflected by the reflective polarizer as a light splitting element to cause light leakage or crosstalk;

FIG. 11 is a schematic diagram of a first optical path and a second optical path forming a single interleaved optical path design in accordance with an embodiment of the present invention;

FIG. 12 is a schematic diagram of a first optical path and a second optical path forming a double interleaved optical path design in accordance with an embodiment of the present invention;

FIG. 13 is a schematic diagram of alternate light paths using a half mirror as a light splitting element according to an embodiment of the present invention;

fig. 14 is a schematic view of two parallax virtual images spaced apart from a windshield at equal distances according to an embodiment of the present invention;

fig. 15 is a schematic diagram of two virtual parallax 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 with positive parallax formed by two virtual parallax images according to an embodiment of the present invention;

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

FIG. 18 is a schematic diagram of a first optical path and a second optical path being non-parallel to but intersecting one another, according to an embodiment of the invention; and

FIG. 19 is a schematic diagram of the first and second optical paths being non-parallel and non-intersecting to each other according to an embodiment of the invention.

Wherein:

a first directional backlit display;

12: a second directional backlit display;

13,14, non-directional backlight type display;

21: a first reflective element;

22 a second reflective element;

31, a light splitting element;

32: a third reflective element;

4, a windshield;

5, a semi-penetrating reflecting film;

a1, A2 is a concave mirror;

BL1 is a side light-in type light source;

BL2 is a point array light source;

CL is a convex lens array;

e1, E2, eye box;

eye, EYES of the viewer;

GP is a light guide plate;

IM1, IM1' the first image light;

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

l1 is a first light path;

l2 is a second light path;

l3 is an optical path;

LE left eye;

p0, P1, P2 is a liquid crystal screen;

PA1, PA2 liquid crystal panel;

RE is the right eye;

RF, resetting to the membrane;

SV is stereoscopic vision image;

v1, V2 is a virtual image;

v3, V4, V4' are virtual parallax images.

Detailed Description

Referring to fig. 5, an embodiment of a naked-eye stereoscopic head-up display device using two directional backlight displays according to the present invention includes a first directional backlight display 11, a second directional backlight display 12, a first reflective device 21, a second reflective device 22, a light splitting device 31, and a third reflective device 32. The arrangement positions of these elements can be, for example, as shown in fig. 5, and the light splitting element 31 is located between the first directional backlight type display 11 and the second directional backlight type display 12 and the third reflective element 32.

The first directional backlight display 11 is used for providing a first image light IM1 with directivity. The second directional backlight display 12 is used for providing a second image light IM2 with directivity. The first image light IM1 and the second image light IM2 are parallax image lights to be incident to both eyes of an observer, respectively. 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 may be Twisted Nematic (TN) liquid crystal, vertical Alignment (VA) liquid crystal, in-Plane Switching (IPS) liquid crystal, or any liquid crystal panel requiring an external light source, instead of being self-luminous. As shown in fig. 6, the backlight sources used in the first directional backlight display 11 and the second directional backlight display 12 may be a side Light source BL1 used in the prior art, which is matched with a Light Guide Plate (Light Guide Plate) GP having a wedge-shaped structure, and a Redirecting Film (Redirecting Film) RF having a prism-shaped structure, so that Light rays pass through the liquid crystal panel PA1 in a straight line, thereby presenting high-directivity narrow-viewing-angle image Light. Alternatively, as shown in fig. 7, the backlight source may be another dot-matrix light source BL2 used in the prior art, which is matched with a Convex Lens Array (concave Lens Array) CL to make the light go straight through the liquid crystal panel PA2, thereby presenting the image light with high directivity and narrow viewing angle.

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

In the present embodiment, the light splitting element 31 and the third reflective element 32 are both curved surfaces, but the present invention is not limited to this implementation; in other embodiments, the light splitting element 31 and the third reflective element 32 may be both planar; alternatively, one of the light splitting element 31 and the third reflecting element 32 is a flat surface, and the other of the light splitting element 31 and the third reflecting element 32 is a curved surface.

In the present embodiment, the light splitting element 31 is a reflective polarizer. In this case, 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.

One of the first directional backlight type display 11, the first reflecting member 21, the light splitting member 31, the windshield 4, and the eye of the viewer forms 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, the light splitting element 31 reflects the first image light IM1 to the windshield 4, and the windshield 4 reflects the first image light IM1 to one of the EYES eye (for example, but not limited to, the left eye) of the viewer to form a parallax virtual image.

The second directional backlight display 12, the second reflecting element 22, the light splitting element 31, the third reflecting element 32, the windshield 4, and the other of the EYES eye of the viewer form a second light 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 light splitting element 31, the second image light IM2 passes through the light splitting element 31 and then reaches the third reflective element 32, the second image light IM2 is reflected by the third reflective element 32 and then passes through the light splitting element 31 again and reaches the windshield 4, and the windshield 4 reflects the second image light IM2 to another eye (for example, but not limited to, the right eye) of the two EYES eye of the viewer, so as 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 are not parallel to each other and may intersect or may not be parallel to each other and do not intersect.

In this way, the two image lights provided by the two directional backlight displays allow the left and right EYES of the EYES eye of the viewer to respectively see two parallax virtual images V3 and V4 (i.e., the left eye parallax virtual image and the right eye parallax virtual image), and visually (i.e., in the brain of the viewer) synthesize a stereoscopic image SV. Visually, the stereoscopic image SV appears as an image appearing in front of the windshield 4 (i.e., the EYES eye and the stereoscopic image SV of the viewer are located on opposite sides of the windshield 4, respectively).

As shown in fig. 6 and 7 as an example of the directional backlight display of the present invention, as shown in fig. 8A and 8B, the Full Width at Half Maximum (FWHM) of the light-emitting field of the backlight of each directional backlight display is about ± 5 ° ± 10 °, so that the viewing angle of the display screen is narrowed, and the eye box (e.g. the eye box E1) after each pixel of the display screen passes through the projection, reflection and amplification of the light path (e.g. the second light path L2) only covers one eye (e.g. the right eye RE) and does not cover the other eye (e.g. the left eye LE). Moreover, the width of the eye box at the distance of the EYES eye of the viewer projected by the image displayed by each directional backlight type display can be approximately the distance between the pupils of the two EYES, namely, about 6.5-7.0 cm.

Compared to the directional backlight display of the present invention, if the directional backlight display of fig. 8A is replaced by the non-directional backlight display 13 and 14 shown in fig. 9A, the FWHM of the light field of the backlight source is about ± 30 ° to ± 60 °, so the viewing angle of the display screen is wider, but the eye box E2 of each pixel of the display screen after projection, reflection and amplification through the light path L3 is too large, as shown in fig. 9B, not only one eye (e.g. the right eye RE) but also the other eye (e.g. the left eye LE) is covered. Therefore, the left eye and the right eye both see the same parallax virtual image, which causes the crosstalk defect and affects the effect of the stereoscopic vision 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, and the second image light IM2 is reflected by the third reflecting element 32 after first passing through the light splitting element 31, so that the second image light IM2 passes through the light splitting element 31 for the second time and is projected to the windshield 4. However, the transmittance of the light splitting element 31 for the second image light IM2 is not 100%, and although most of the second image light IM2 will penetrate through the light splitting element 31, a small portion of the second image light IM2 is reflected by the light splitting element 31 to the windshield 4, resulting in incomplete light splitting. 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 of the light splitting element 31 are close, a small portion of the second image light IM2 (i.e., the image light IM2 ') reflected by the light splitting element 31 enters any eye of the EYES eye of the viewer after being reflected by the windshield 4, and a further parallax virtual image V4' is formed, so that there is a light leakage problem that one eye sees two identical parallax virtual images V4 (target virtual images) and V4', or a cross talk problem that the other eye sees two different parallax virtual images V3 (target virtual images) and V4'.

In order to solve the above-mentioned problems of light leakage and crosstalk, in this embodiment or other embodiments, as shown in fig. 5 and 11, the first optical path L1 and the second optical path L2 are not parallel but intersect (as shown in fig. 18) or are not parallel but intersect (as shown in fig. 19) between the light splitting element 31 and the first reflecting element 21 and the second reflecting element 22, so as to form a single-crossed optical path design. Thereby, the difference of the incident angles of the two optical paths on the light splitting element 31 can be increased to improve the isolation between the optical paths. Even if there is a small portion of the image light IM2' reflected by the light splitting element 31 in the second image light IM2 of the second optical path L2, the incident angle of the deviated optical path on the light splitting element 31 is greatly different from the incident angle of the first optical path L1 on the light splitting element 31, and the image light will not enter any eye of the EYES eye of the viewer, thereby avoiding the problems of light leakage and crosstalk. Moreover, the light path can be designed into a light path with double isolation by matching the light path with a directional backlight type display.

In order to increase the isolation between the light paths, in another embodiment, the first light path L1 and the second light path L2 may further be non-parallel but intersecting or non-parallel and non-intersecting 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, as shown in fig. 12. Therefore, the difference of the incident angles of the two light paths on the corresponding reflecting elements is increased, the isolation between the light paths is enhanced, the double-staggered light path design is realized, and the light path design with triple isolation is realized by using the directional backlight type display.

In addition to the reflective polarizer, the light splitting element 31 may be a half mirror (e.g., half-reflective and half-transmissive), and as shown in fig. 13, the image light of each directional backlight display does not need to be light with mutually perpendicular polarization directions, and may be unpolarized image light, for example, and can achieve a good light 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 is further reflected to one of the EYES eye of the viewer, and the first image light IM1' partially transmitted through the light splitting element 31 does not enter either eye of the EYES eye of the viewer due to the optical path angle difference. The second image light IM2 on the second light path L2 partially passes through the light splitting element 31 to reach the third reflecting element 32 for the first time, and the second image light IM2' partially reflected by the light splitting element 31 does not enter any eye of the EYES eye of the viewer due to the difference of the light path angles; part of the second image light IM2 which penetrates through the light splitting element 31 for the first time continues to move forward to the designed light path direction, after being reflected by the third reflecting element 32, part of the second image light IM2 which penetrates through the light splitting element 31 for the second time reaches the windshield 4 and then is projected to the other eye of the EYES eye of the viewer, and the rest of the second image light IM2 ″ which is reflected by the light splitting element 31 for the second time cannot enter any eye of the EYES eye of the viewer due to the light path angle difference; the parallax images of the left eye and the right eye are respectively projected on the left eye and the right eye of an observer, and stereoscopic vision images are synthesized in the brain and sea, so that the naked-eye 3D effect is achieved.

In the embodiments of the present invention, the naked-eye stereoscopic head-up display device may further meet the following conditions:

[(D1+S1)×A1+R1]×GA＝[(D2+S2)×A2+R2]×GA

as shown in fig. 14, a distance between the first directional backlight display 11 and the first reflective element 21 is D1, a distance between the second directional backlight display 12 and the second reflective element 22 is D2, a distance between the first reflective element 21 and the light splitting element 31 is S1, a distance between the second reflective element 22 and the third reflective element 32 is S2, a distance between the light splitting element 31 and the windshield 4 is R1, a distance between the third reflective element 32 and the windshield 4 is R2, an amplification factor of the light splitting element 31 is A1, an amplification factor of the third reflective element 32 is A2, and an amplification factor of the windshield 4 is GA. In this way, the distances between the two parallax virtual images V3 and V4 of the left and right eyes to the windshield 4 are equal, and a stereoscopic image is formed in the mind of the viewer.

In each embodiment of the present invention, the relative positions of the left-eye Parallax virtual image and the right-eye Parallax virtual image are affected by the staggered offset degree of the first optical path L1 and the second optical path L2 in the EYES eye projected to the viewer, so that the first optical path L1 and the second optical path L2 can be adjusted and designed according to the functional requirements, so that the two Parallax virtual images V3 and V4 of the left and right EYES are overlapped together, and the stereoscopic vision image SV in the brain of the viewer is at the position of the virtual image and has the same distance as the virtual image, and at this time, has Zero Parallax (Zero Parallax), as shown in fig. 15. Alternatively, the two Parallax virtual images V3 and V4 of the left and right eyes may be partially superimposed, the left eye virtual image is offset to the left, the right eye virtual image is offset to the right, and the stereoscopic image SV in the brain of the viewer is behind the virtual image position and is further away than the virtual image distance, which is Positive Parallax (Positive Parallax), as shown in fig. 16. Alternatively, the two Parallax virtual images V3 and V4 for the left and right eyes may be partially superimposed, the left-eye virtual image may be offset to the right, the right-eye virtual image may be offset to the left, and the stereoscopic video SV in the mind of the viewer may be closer to the front of the virtual image position than the virtual image, which is a Negative Parallax (Negative Parallax), as shown in fig. 17.

In the embodiments of the present invention, the naked-eye stereoscopic head-up display device further includes a transflective film 5 disposed on the windshield 4, as shown in fig. 5. The transflective film is used for reflecting the first image light IM1 and the second image light IM2 to the left EYE and the right EYE of the viewer, respectively. Therefore, the reflectivity of the projection of the picture can be improved.

Although the present invention has been described with reference to the above embodiments, the embodiments are not intended to limit the present invention. All changes, modifications and combinations that come within the spirit and scope of the invention are desired to be protected by the following claims. For the protection defined by the present invention, reference should be made to the appended claims.

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