A backlight illumination system for a head-up display device, a head-up display device, a motor vehicle and a method of generating uniform imaging light

Abstract

This invention discloses a backlight illumination system for a head-up display device. The backlight illumination system includes an LED array, a lens group, and an LCD screen, arranged from bottom to top. The LED array includes one or more LED beads. The lens group includes a spherical lens, a freeform lens, and a Fresnel lens, arranged from bottom to top. The lens group performs three-stage shaping on the light emitted from the LED array to gradually reduce the divergence angle of the light before it illuminates the Fresnel lens, performing final adjustment and homogenization of the light illumination area. The emitted light then illuminates the LCD screen. This invention also discloses a head-up display device, a motor vehicle, and a method for generating uniform imaging light.

Description

Technical Field

[0001] This invention belongs to the field of head-up display backlight technology, and relates to a backlight illumination system for a head-up display, a head-up display, a motor vehicle, and a method for generating uniform imaging light. Background Technology

[0002] Head-up display (HUD) systems can be categorized into three main types based on their optical-mechanical projection technologies: TFT-LCD, DLP, and LCoS. TFT-LCD technology is mature and cost-effective, making it widely used in wireless head-up displays (W-HUDs). DLP offers excellent performance and prevents sunlight backlighting, making it the preferred choice for AR-HUDs, but it suffers from higher costs and supply instability. LCoS, due to its less mature technology, lacks customization options. Therefore, LCD is currently the preferred mature solution for image sources and warrants further research. With the development of HUD technology, high-efficiency, high-brightness, high-uniformity, and low-cost backlighting is gaining increasing attention.

[0003] In HUD systems that utilize LCDs as the image source, the LCDs do not emit light actively or have insufficient brightness, requiring a backlight system to provide high brightness to illuminate them. This is especially true in strong ambient light conditions, where the brightness requirements for the backlight are even higher. Furthermore, for the overall display effect of the HUD, the uniformity of the backlight is also crucial. Currently, the basic principle of all backlight systems is: first, collimate the LED light source; then, shape, expand, and homogenize the collimated light. The principle utilized in Chinese invention patent CN111025642B, a HUD backlight system combining a collimating lens and a microarray Fresnel lens, follows the same approach. It performs collimation and beam expansion to homogenize the light, but the main problems are: 1. While a single LED can achieve uniform illumination and high energy efficiency, splicing multiple LEDs can result in severe seams, easily causing dark areas on the LCD surface; 2. If the lens array is spliced ​​in a hexagonal or rectangular pattern, bright stripes can easily appear, leading to bright areas; 3. For larger LCDs, in order to achieve better uniformity, the LEDs are arranged with closer spacing and a larger number, exacerbating heat dissipation difficulties; 4. Splicing can cause changes in the light angle, resulting in low energy efficiency; and other problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a backlighting system for a head-up display (HUD) device, which obtains a uniform LCD backlight by reshaping the light emitted from the LED array three times.

[0005] The backlight illumination system of the present invention includes: an LED array, a lens group, and an LCD screen, arranged from bottom to top;

[0006] The lens group includes a spherical lens, a freeform surface lens, and a Fresnel lens; the spherical lens, the freeform surface lens, and the Fresnel lens are arranged from bottom to top.

[0007] The LED array includes one or more LED beads to provide a light source for the backlight illumination system; the divergence angle of the light emitted by the LED beads is 30° to 180°; the number and spacing of the LED array are selected according to the size of the LCD screen to be illuminated, the brightness of the virtual image in the backlight illumination system, imaging uniformity, cost and other requirements for a more suitable arrangement.

[0008] When the LCD size to be illuminated is large, and / or when higher virtual image brightness is required, and / or when higher imaging uniformity is required, more and denser LED beads need to be set; however, the more LED beads there are, the higher the cost will be, so comprehensive consideration is required.

[0009] In setting up the LED array, it is necessary to consider ensuring that there is no interference between the spherical lenses and between the freeform lenses;

[0010] In one specific embodiment, the LED array comprises a single LED bead in one row and one column; or,

[0011] In one specific embodiment, the LED array includes multiple LED beads in a single row and multiple columns; or,

[0012] In one specific embodiment, the LED array includes multiple LED beads in multiple rows and single columns; or

[0013] In one specific embodiment, the LED array includes multiple LED beads in multiple rows and columns;

[0014] The spherical lens is disposed above the LED beads in the LED array, and its number corresponds to the number of LED beads, being one or more, with one spherical lens disposed on each LED bead; the diameter of the spherical lens is greater than or equal to the size of the LED bead, and the distance between the spherical lens and the LED bead is 2-10mm; the spherical lens includes a plane and a spherical surface, wherein the plane of the spherical lens is the light-incident surface, and the spherical surface of the spherical lens is the light-exit surface; the light emitted from the LED beads has its divergence angle reduced after passing through the spherical lens, and the divergence angle is reduced to 80°~100°;

[0015] The freeform lens is disposed above the spherical lens and includes a plane and a freeform surface. The plane of the freeform lens is the incident light surface, and the freeform surface is the exit light surface. The plane of the freeform lens is opposite to the spherical surface of the spherical lens. The distance between the freeform lens and the spherical lens is 0-10mm. After passing through the freeform lens, the divergence angle of the light will be further reduced, and the divergence angle of the collimated light will be 2°-5°.

[0016] When the plane of the freeform lens is in contact with the spherical surface of the spherical lens (i.e., the distance is 0), the freeform lens is smaller in size, and the area illuminated by a single LED is smaller. This is suitable for scenarios with a large number of LEDs, where a single LED does not need to illuminate a large area, and where high uniformity is required; or,

[0017] When the plane of the freeform lens does not contact the spherical surface of the spherical lens (i.e., the distance is not 0), the size of the freeform lens is relatively large, and the area illuminated by a single LED is large. It is suitable for scenarios where the number of LEDs is small, the cost requirement is high, and the goal is to reduce costs.

[0018] The freeform surface of the freeform lens is a polynomial aspherical or an even-order aspherical.

[0019] The freeform surface shape of a polynomial aspheric surface is expressed by the following formula:

[0020]

[0021] Where z represents the freeform surface elevation, c is the curvature, the reciprocal of the radius, k is the conic coefficient, and α1, α2, α3, α4, α5, α6, α7, α8, ..., α 16 , where is the aspherical coefficient, and r is the diameter of the freeform surface; or,

[0022] When the coefficient of the odd-power term in the formula for the freeform surface shape of a polynomial aspheric surface is 0, then it is the formula for the freeform surface shape of an even-power aspheric surface.

[0023] The Fresnel lens is positioned above the freeform lens and its size is sufficient to cover the entire LCD screen. It is used for beam expansion and shaping. The flat surface of the Fresnel lens without microstructures is the light-incident surface, and the other side is a convex Fresnel surface, which is the light-out surface of the Fresnel lens.

[0024] The distance between the Fresnel lens and the freeform surface lens is 2-40mm, and the distance between the Fresnel lens and the LCD screen is 60-120mm;

[0025] The Fresnel lens is positioned below the lowest point of the LCD screen; the overall backlight height affects the overall backlight volume, and a smaller volume reduces the size requirement for the HUD, with smaller being better; and / or,

[0026] The collimation of light rays affects the beam expansion and shaping of a Fresnel lens, thus influencing the size and uniformity of the illuminated area. Fresnel lenses require a high degree of collimation of the incident light; the more collimated, the better.

[0027] The LCD screen is positioned above the Fresnel lens but does not contact it. The reference angle of the LCD screen forms an angle of 15° or 20° with the horizontal plane and can vary within the range of 10° to 30°.

[0028] The present invention also provides a method for generating uniform imaging light rays, the method comprising the following steps: an LED array emits light rays with a divergence angle of 30° to 180°; the light rays pass through a spherical lens, where the divergence angle is reduced to 80° to 100° and continue to propagate forward; after passing through a freeform lens, the light rays are collimated, with a divergence angle of 2° to 5°, and continue to propagate forward; the light rays emitted from the freeform lens enter a Fresnel lens for homogenization, shaping, and beam expansion, so that the angle of the light rays matches the HUD imaging light rays, and finally uniformly illuminate the surface of the LCD screen;

[0029] In HUD imaging design, the light emitted from the LCD screen has a certain angle, within 80° along the long side and within 60° along the short side. When designing the backlight, the angle of the backlight light must cover this angle in both the long and short sides; ideally, the angles should be perfectly matched.

[0030] The present invention also provides a head-up display device, the head-up display device including the backlight illumination system described above.

[0031] The present invention also provides a motor vehicle comprising the aforementioned backlighting system and / or head-up display device.

[0032] The beneficial effects of this invention include:

[0033] This invention solves the problem of dark and bright areas caused by LED collimation and splicing, resulting in a more uniform lighting effect. In this invention, one LED corresponds to one spherical lens and one freeform lens. The light emitted by the LED undergoes three shaping processes, including spherical lens, freeform lens, and Fresnel lens, respectively. The light is fully fused, eliminating blind spots or overlapping areas. The lenses do not intersect, thus eliminating dark and bright areas when diffused onto the LCD surface. The uniformity can reach over 85%, while in existing technologies, the uniformity is only 55%–90%.

[0034] Since there is no need to splice the lenses, the spacing between the LED beads does not need to be very close, which is beneficial for heat dissipation.

[0035] Meanwhile, since there is no need to splice the lenses, the light angle will not be destroyed or there will be too much intersection, resulting in a high energy utilization rate of over 70%, while the energy utilization rate of existing technologies is only 50% to 70%.

[0036] The light shaping part of this invention has a simple structure. The entire structure (lens group) consists of only three parts and does not require a large number of microstructures on the surface of the beam expander, such as striped beam expander structures.

[0037] The Fresnel lens used in this invention is a conventional Fresnel lens, which has a mature manufacturing process, is easy to mass-produce, and is inexpensive. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the backlight illumination system of the present invention.

[0040] Figure 2 This is a front view of the backlight illumination system of the present invention.

[0041] Figure 3 This is a left view of the backlight illumination system of the present invention.

[0042] Figure 4 This is a schematic diagram of the path of the light rays emitted from the LED array after passing through the spherical lens and the freeform lens.

[0043] Figure 5 This is a top view of the Fresnel lens of the present invention.

[0044] Figure 6 This is a top view of an LED array according to a specific embodiment of the present invention.

[0045] Figure 7 This is a schematic diagram of the surface space brightness of the LCD in an embodiment of the present invention.

[0046] Figure 8 This is a schematic diagram of LCD surface illumination in an embodiment of the present invention.

[0047] Figure 9 This is a schematic diagram of the uniformity testing method in an embodiment of the present invention. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings. Except for the contents specifically mentioned below, the processes, conditions, and experimental methods for implementing the present invention are all common knowledge and general knowledge in the art, and the present invention does not have any particular limitations.

[0049] This invention provides a backlighting system for a HUD, which mainly consists of five components, from bottom to top: LED beads arranged in a specific order, a primary spherical lens, a secondary freeform lens, a Fresnel lens, and an LCD screen, as shown below. Figure 4 As shown, the light emitted by the LED beads, which has a large divergence angle, shines on the first-stage spherical lens. After the light undergoes initial shaping, the divergence angle is initially reduced. Then, the light with the reduced divergence angle shines on the second-stage freeform lens, which changes the divergence angle and homogenizes it. Finally, the light shines on the Fresnel lens, where the light-illuminated area is adjusted and homogenized. After exiting, the light shines on the LCD screen.

[0050] This invention provides a backlight illumination system for a head-up display system, such as... Figure 1-3 As shown, the backlighting system includes an LED array, a lens group, and an LCD screen, arranged from bottom to top.

[0051] The LED array includes one or more LED beads;

[0052] The lens group includes a spherical lens, a freeform lens, and a Fresnel lens; the spherical lens, the freeform lens, and the Fresnel lens are arranged from bottom to top; the lens group reshapes the light emitted by the LED array three times.

[0053] The LED beads are arranged in one row and one column, a single row and multiple columns, multiple rows and a single column, or multiple rows and multiple columns; the divergence angle of the light emitted by the LED beads is 30° to 180°; specifically, in one embodiment, the LED beads are arranged in five rows and three columns, such as... Figure 6 As shown.

[0054] The spherical lens is disposed above the LED bead, and the number of spherical lenses is equal to the number of LED beads, consisting of one or more; the diameter of the spherical lens is greater than or equal to the size of the LED bead.

[0055] The spherical lens comprises a plane and a sphere. The plane of the spherical lens is the incident light surface, and the sphere is the exit light surface. The divergence angle of the light rays passing through the spherical lens is 80° to 100°.

[0056] The freeform lens is disposed above the spherical lens and includes a plane and a freeform surface. The plane of the freeform lens is the incident light surface, and the freeform surface is the exit light surface. The plane of the freeform lens is opposite to the spherical surface of the spherical lens. The distance between the freeform lens and the spherical lens is 0-10mm. After passing through the freeform lens, the collimated light divergence angle is 2°-5°.

[0057] The freeform surface of the freeform lens is a polynomial aspherical or an even-order aspherical.

[0058] The freeform surface shape of a polynomial aspheric surface is expressed by the following formula:

[0059]

[0060] Where z represents the freeform surface elevation, c is the curvature, the reciprocal of the radius, k is the conic coefficient, and α1, α2, α3, α4, α5, α6, α7, α8, ..., α 16 , where is the aspherical coefficient, and r is the diameter of the freeform surface; or,

[0061] When the coefficient of the odd-power term in the formula for the freeform surface shape of a polynomial aspheric surface is 0, then it is the formula for the freeform surface shape of an even-power aspheric surface.

[0062] Compared to conventional polynomial aspheric freeform surface types, the effect is better when the coefficients of odd-degree terms in the formula are set to 0, i.e., when using even-degree aspheric freeform surface types.

[0063] like Figure 5 As shown, the Fresnel lens is positioned above the freeform lens, with the flat surface without microstructures serving as the light-incident surface and the convex Fresnel surface serving as the light-outceasing surface.

[0064] The distance between the Fresnel lens and the freeform lens is 2–40 mm, and the distance between the Fresnel lens and the LCD screen is 60–120 mm.

[0065] The LCD screen is positioned above the Fresnel lens, and the reference angle of the LCD screen forms an angle of 15° or 20° with the horizontal plane. The LCD screen can vary within a range of 10° to 30° with the horizontal plane.

[0066] Example 1

[0067] This embodiment provides a backlight illumination system for a head-up display device. The backlight illumination system is suitable for a 3.1-inch LCD. The LED array in the backlight illumination system contains 2*6 LED beads, with a distance of 15mm between each LED bead. The corresponding radius of the first-order spherical lens is 4mm, and the surface shape of the second-order freeform lens is an even-order aspherical surface. The surface shape formula is described by the following formula, where the coefficient of the odd-degree term in the polynomial aspherical freeform surface shape formula is 0:

[0068]

[0069] coefficient Mouth diameter 18.15805184 Conic coefficient .0.674899232 curvature 0.193175367 4th order -3.57E-05 6th order -3.78E-07 8th order -5.03E-09 10th level -3.40E-11 12th order .5.82E-14 14th level 2.25E-16 16th order 4.75E-18

[0070] The distance from the LCD screen to the Fresnel lens surface is 100mm;

[0071] The light emitted by the LED array is emitted with a divergence angle of 120°. After passing through a spherical lens, the divergence angle is reduced to 80°. After passing through a freeform lens, the divergence angle is reduced to 3° again before entering a Fresnel lens. After being adjusted and homogenized by the Fresnel lens, the light is emitted and illuminates the LCD screen.

[0072] Figure 7 The spatial brightness diagram in this embodiment shows that the main energy of the backlight (red area) is concentrated in the 70*42mm area, which is suitable for a 3.1-inch backlight (68.4*41.04mm). The energy is relatively concentrated, the utilization rate is high, and the uniformity is good.

[0073] Figure 8 The image shows the surface illuminance of the LCD in this embodiment. The slice image shows that the backlight uniformity is good, the interface is distinct, and the energy utilization rate is high. The main energy (red area) is concentrated in the 70*42mm area, which is suitable for 3.1-inch backlight (68.4*41.04mm) and the energy is relatively concentrated.

[0074] In this embodiment, the uniformity of the light-illuminated area is determined through the following steps, such as... Figure 9 As shown in the diagram, take nine dots on the LCD screen, with the diameter of the dots ranging from 0.2V to 0.2H (the minimum value between the two is recommended). Measure the brightness value of these nine dots, and convert the minimum brightness value to the maximum value to obtain the uniformity.

[0075] Example 2

[0076] This embodiment provides a backlight illumination system for a head-up display device. The backlight illumination system is suitable for a 4.1-inch LCD. The LED array in the backlight illumination system contains 3*6 LED beads, with a distance of 14.5mm between each LED bead. The corresponding radius of the first-order spherical lens is 4mm, and the surface shape of the second-order freeform lens is an even-order aspherical surface. The surface shape formula is described by the following formula, where the coefficient of the odd-degree term in the polynomial aspherical freeform surface shape formula is 0:

[0077]

[0078] Mouth diameter 7 Conic coefficient -0.2034344 curvature 0.28161155 4th order 0.01550345 6th order 0.00021122 8th order 6.51E-06 10th level 2.23E-07 12th order -4.34E-09 14th level -2.77E-10 16th order -3.59E-11

[0079] The distance from the LCD screen to the Fresnel lens surface is 110mm;

[0080] The light emitted by the LED array is emitted with a divergence angle of 110°. After passing through a spherical lens, the divergence angle is reduced to 90°. After passing through a freeform lens, the divergence angle is reduced to 5° again before entering a Fresnel lens. After being adjusted and homogenized by the Fresnel lens, the light is emitted and illuminates the LCD screen.

[0081] Example 3

[0082] This embodiment provides a backlight illumination system for a head-up display device. The backlight illumination system is suitable for a 4.1-inch LCD. The LED array in the backlight illumination system contains 4*6 LED beads, with a distance of 13mm between each LED bead. The corresponding radius of the first-order spherical lens is 3mm, and the surface shape of the second-order freeform lens is an even-order aspherical surface. The surface shape formula is described by the following formula, where the coefficient of the odd-degree term in the polynomial aspherical freeform surface shape formula is 0:

[0083]

[0084] Mouth diameter 8.30360087 Conic coefficient -0.0992792 curvature 0.25378646 4th order 0.00084672 6th order 3.94E-05 8th order -5.67E-06 10th level 2.35E-09 12th order -6.55E-09 14th level -9.65E-10 16th order 7.62E-11

[0085] The distance from the LCD screen to the Fresnel lens surface is 120mm;

[0086] The light emitted by the LED array is emitted with a divergence angle of 130°. After passing through a spherical lens, the divergence angle is reduced to 80°. After passing through a freeform lens, the divergence angle is reduced to 3° again before entering a Fresnel lens. After being adjusted and homogenized by the Fresnel lens, the light is emitted and illuminates the LCD screen.

[0087] Example 4

[0088] This embodiment provides a backlight illumination system for a head-up display device. The backlight illumination system is suitable for a 4.1-inch LCD. The LED array in the backlight illumination system contains 3*7 LED beads, with a distance of 10mm between each LED bead. The corresponding radius of the first-order spherical lens is 3mm, and the surface shape of the second-order freeform lens is an even-order aspherical surface. The surface shape formula is described by the following formula, where the coefficient of the odd-degree term in the polynomial aspherical freeform surface shape formula is 0:

[0089]

[0090] Mouth diameter 7 Conic coefficient -0.2039016 curvature 0.28117914 4th order 0.0154463 6th order 2.11E-04 8th order 5.89E-06 10th level 1.82E-07 12th order -6.42E-09 14th level -3.21E-10 16th order -5.65E-11

[0091] The distance from the LCD screen to the Fresnel lens surface is 100mm;

[0092] The light emitted by the LED array is emitted with a divergence angle of 105°. After passing through a spherical lens, the divergence angle is reduced to 85°. After passing through a freeform lens, the divergence angle is reduced to 4° again before entering a Fresnel lens. After being adjusted and homogenized by the Fresnel lens, the light is emitted and illuminates the LCD screen.

[0093] In the description of this invention, it should be noted that when terms indicating direction or position appear, the orientation or positional relationship indicated therein is based on the orientation or positional relationship shown in the accompanying drawings. This is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0094] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0095] This invention discloses many different embodiments or examples for implementing different structures of this application. To simplify the disclosure, specific examples of components and arrangements are described in the embodiments of this invention. Of course, these are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or reference letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0096] The scope of protection of this invention is not limited to the above embodiments. Any variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of this invention are included in this invention and are protected by the appended claims.

Claims

1. A backlight illumination system for a head-up display device, characterized in that, The backlighting system includes an LED array, a lens group, and an LCD screen, arranged from bottom to top. The LED array includes one or more LED beads; The lens group includes a spherical lens, a freeform lens, and a Fresnel lens; the spherical lens, the freeform lens, and the Fresnel lens are arranged from bottom to top; the lens group reshapes the light emitted by the LED array three times.

2. The backlighting system as described in claim 1, characterized in that, The LED beads are arranged in one row and one column, a single row and multiple columns, multiple rows and a single column, or multiple rows and multiple columns; the divergence angle of the light emitted by the LED beads is 30° to 180°.

3. The backlighting system as described in claim 1, characterized in that, The spherical lens is disposed above the LED bead, and the number of spherical lenses corresponds to the number of LED beads, being one or more; the diameter of the spherical lens is greater than or equal to the size of the LED bead; the distance between the spherical lens and the LED bead is 2-10mm; The spherical lens comprises a plane and a sphere. The plane of the spherical lens is the incident light surface, and the sphere is the exit light surface. The divergence angle of the light rays passing through the spherical lens is 80° to 100°.

4. The backlighting system as described in claim 1, characterized in that, The freeform lens is disposed above the spherical lens and includes a plane and a freeform surface. The plane of the freeform lens is the incident light surface, and the freeform surface is the exit light surface. The plane of the freeform lens is opposite to the spherical surface of the spherical lens. The distance between the freeform lens and the spherical lens is 0-10mm. After passing through the freeform lens, the collimated light divergence angle is 2°-5°.

5. The backlighting system as described in claim 4, characterized in that, The freeform surface of the freeform lens is a polynomial aspherical or an even-order aspherical. The freeform surface shape of a polynomial aspheric surface is expressed by the following formula: Where z represents the freeform surface elevation, c is the curvature (the reciprocal of the radius), k is the conic coefficient, and α1, α2, α3, α4, α5, α6, α7, α8, ..., α 16 Both are aspherical coefficients, where r is the diameter of the freeform surface; or, When the coefficient of the odd-power term in the formula for the freeform surface shape of a polynomial aspheric surface is 0, then it is the formula for the freeform surface shape of an even-power aspheric surface.

6. The backlighting system as described in claim 1, characterized in that, The Fresnel lens is positioned above the freeform lens, with the flat surface without microstructures serving as the light-incident surface and the convex Fresnel surface serving as the light-outceasing surface. The distance between the Fresnel lens and the freeform surface lens is 2-40mm, and the distance between the Fresnel lens and the LCD screen is 60-120mm; The Fresnel lens is positioned below the lowest point of the LED screen.

7. The backlighting system as described in claim 1, characterized in that, The LCD screen is positioned above the Fresnel lens, and the reference angle of the LCD screen forms an angle of 15° or 20° with the horizontal plane. The LCD screen can vary within a range of 10° to 30° with the horizontal plane.

8. A method for generating uniform imaging rays, characterized in that, The method utilizes the backlight illumination system as described in any one of claims 1-7, comprising the following steps: an LED array emits light rays with a divergence angle of 30° to 180°; the divergence angle of the light rays is reduced to 80° to 100° after passing through a spherical lens and continues to propagate forward; after passing through a freeform lens, the light rays are collimated, with a divergence angle of 2° to 5°, and propagate forward; the light rays emitted from the freeform lens enter a Fresnel lens for homogenization, shaping, and beam expansion, so that the angle of the light rays matches the HUD imaging light rays, and finally uniformly illuminates the surface of the LCD screen.

9. A head-up display device, characterized in that, The head-up display device includes a backlight illumination system as described in any one of claims 1-7.

10. A motor vehicle, characterized in that, The motor vehicle includes a backlighting system as described in any one of claims 1-7, and / or a head-up display as described in claim 9.

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