Backlight module

Abstract

A backlight module includes at least one sub-backlight unit, each sub-backlight unit comprising a cylindrical lens, a light source carrier, a plurality of light strips, a first sidewall, and a second sidewall. The cylindrical lens has an incident light surface and an emitting elongated convex curved surface relative to the incident light surface. The light source carrier has a semi-tubular concave curved surface, wherein the semi-tubular concave curved surface is a Pessava surface of the cylindrical lens. The plurality of light strips extend side-by-side along the long side of the semi-tubular concave curved surface. The first sidewall and the second sidewall are located on opposite long sides of the space enclosed by the cylindrical lens and the light source carrier, respectively.

Description

[Technical Field]

[0001] This invention relates to a backlight module, and more particularly to a backlight module suitable for stereoscopic displays. [Previous Technology]

[0002] Existing naked-eye 3D displays use a unidirectional backlight module paired with metalens. In the backlight module, the light source is positioned at the focal point of a cylindrical lens and projects light. The light is collimated by the cylindrical lens. These collimated rays are then deflected by the metalens in the voxel (also known as a stereo pixel or volumetric pixel) to various different viewing angles, producing a wide field of view (also known as the visible range, measured in angles) multi-view effect. However, existing 3D displays have limited angular resolution (optical resolution measured in angles), with a minimum deflection angle of about 3 degrees.

[0003] To improve the angular resolution of a stereoscopic display by reducing the deflection angle, there are currently two methods in the prior art. One is to reduce the deflection angle difference of the superlens; however, this method reduces the field of view. The other method is to increase the number of pixels in the voxel; however, this method often leads to a decrease in image resolution at a specific single viewing angle. [Summary of the Invention]

[0004] One objective of the present invention is to provide a backlight module that can improve both angular resolution and image resolution while retaining the field of view, so as to solve the problems encountered in the prior art.

[0005] Embodiments of the present invention provide a backlight module, including at least one sub-backlight unit. Each sub-backlight unit includes a cylindrical lens, a light source carrier, a plurality of light strips, a first sidewall, and a second sidewall. The cylindrical lens has an incident light surface and an emitting elongated convex curved surface relative to the incident light surface. The light source carrier has a semi-tubular concave curved surface, wherein the semi-tubular concave curved surface is a Pessava surface of the cylindrical lens. The plurality of light strips extend side-by-side along the long side of the semi-tubular concave curved surface. The first sidewall and the second sidewall are located on opposite long sides of the space enclosed by the cylindrical lens and the light source carrier, respectively.

[0006] Another embodiment of the present invention provides a backlight module including at least one sub-backlight unit, each sub-backlight unit including a cylindrical lens, a plurality of light strips, a first sidewall, and a second sidewall. The cylindrical lens has an incident light surface and an emitting light strip convex surface relative to the incident light surface. The plurality of light strips extend along the long side direction of the cylindrical lens and are arranged side by side on one side of the incident light surface of the cylindrical lens, wherein the connecting line of these light strips arranged on a virtual cross-section in the transverse long side direction forms a Pessava surface of the cylindrical lens. The first sidewall and the second sidewall are respectively located on the opposite long side sides of the space between the cylindrical lens and these light strips.

[0007] According to the backlight module of the present invention, the light source carrier has a semi-circular concave surface, on which a plurality of light strips are provided. The light emitted from these light strips enters a cylindrical lens through an incident surface and exits the cylindrical lens through an exiting convex surface. The half-width at half-maximum (FWHM) of the intensity of these light rays measured from the exiting convex surface is within ±2.29 degrees. In this way, the backlight module of the present invention can improve angular resolution and image resolution while retaining the field of view.

Implementation Method

[0015] Various embodiments will be described herein, and those skilled in the art should be able to easily understand the spirit and principles of the invention by referring to the description and accompanying drawings. However, although some specific embodiments will be specifically described herein, these embodiments are merely illustrative and are not to be considered limiting or exhaustive in any respect. Therefore, various changes and modifications to the invention will be obvious and easily achievable by those skilled in the art without departing from the spirit and principles of the invention.

[0016] In various embodiments of the present invention, "upper," "lower," "left," "right," "front," or "rear" are used herein to describe the relationship between one element and another, and are only used to illustrate the orientation presented in the figures, not to limit their actual positions. The orientation or orientation of the elements in the device in the figures is not limited by the rotation of the device.

[0017] FIG1 is a schematic diagram of a backlight module according to an embodiment of the present invention. Please refer to FIG1. The backlight module 10 includes at least one sub-backlight unit. In this embodiment, the number of these sub-backlight units is, for example, three (sub-backlight units 100A, 100B, and 100C as shown in Figure 1, but not limited to this). These adjacent sub-backlight units 100A, 100B, and 100C can emit collimated light to deflecting elements (not shown). The deflecting elements, in conjunction with metasurfaces, can deflect these collimated light to, for example, two hundred different viewing planes. Combined with eye-tracking technology to detect the user's eye position, the illumination of each light strip (shown in Figures 2 to 4) in each sub-backlight unit 100A, 100B, and 100C can be individually controlled. In this way, the stereoscopic display device using the backlight module 10 of the present invention can achieve the effect of eliminating the vergence-accommodation conflict (VAC, i.e., the dizziness caused by the inconsistency between the eye's focusing depth and the angle of eye rotation).

[0018] Figure 2 is a schematic diagram of the sub-backlight unit according to the embodiment of Figure 1, Figure 3 is an exploded view of the sub-backlight unit according to the embodiment of Figure 2, and Figure 4 is a cross-sectional view of the sub-backlight unit according to the embodiment of Figure 2 along line segment AA'. Please refer to Figures 2 to 4. The sub-backlight unit 100A has a structure that is substantially the same as that of the sub-backlight units 100B and 100C. Here, we will take the sub-backlight unit 100A as an example. The sub-backlight unit 100A of this embodiment includes a cylindrical lens 101, a light source carrier 103, a plurality of light strips 1032, a first sidewall 1021, and a second sidewall 1022 opposite to the first sidewall 1021. The cylindrical lens 101 has an incident light surface 1011 and an exiting elongated convex surface 1012 relative to the incident light surface 1011. In another preferred embodiment, the cylindrical lens 101 also has a first side surface 10131 connecting the incident light surface 1011 and the exiting elongated convex surface 1012 and a second side surface 10132 connecting the incident light surface 1011 and the exiting elongated convex surface 1012 and relative to the first side surface 10131. In this embodiment, the light-incident surface 1011 is, for example, a plane, and the light-emitting elongated convex surface 1012 is, for example, an aspherical surface. The long side direction of the sub-backlight module 100A is D1. The cross-sectional shape of the light-emitting elongated convex surface 1012 in the long side direction D1 of the transverse cylindrical lens 101 preferably conforms to the following formula (1): (1) where (x, z) represents the position on the light-emitting elongated convex surface 1012 with the vertex of the light-emitting elongated convex surface 1012 as the origin on the virtual plane where the above cross-section is located, c is the radius of curvature, and k is the conic constant. In this way, the cylindrical lens 101 can form collimated and highly uniform light rays from incident light from different angles and emit them. In some preferred embodiments, when the stereoscopic display device using the backlight module 10 has a field of view of, for example, 40 degrees, the k value is -1 and the radius of curvature (i.e., the c value) can be 0.115 mm; while when the stereoscopic display device using the backlight module 10 has a field of view of, for example, 50 degrees, the k value is -1 and the radius of curvature can be 0.135 mm. Furthermore, the lenticular lens 101 is, for example, first manufactured using a corresponding mold via computer numerical control (CNC), and then molded using a transparent, curable material.Materials that can be used to fabricate the lenticular lens 101 include, for example, polydimethylsiloxane (PDMS), thermosetting silicone rubber (HCR), epoxy resin, or photocurable polymers (such as photosensitive resin, transparent materials such as polypropylene, PP, etc.) manufactured by molding. In a preferred embodiment, the thickness of the lenticular lens 101 (i.e., the maximum distance between the light-incident surface 1011 and the light-emitting elongated convex surface 1012 in a direction perpendicular to the light-incident surface 1011) is, for example, 32 mm. The width of the lenticular lens 101 can be 130 mm, the length can be 325 mm, and the focal length is 190 mm. Additionally, the surface of the lenticular lens 101 can be selectively coated with a liquid having the same refractive index as the material of the lenticular lens 101 to increase the smoothness of the lenticular lens 101.

[0019] Please continue to refer to Figures 2 and 4. The light source carrier 103 is made of, for example, a 3D-printed photocurable resin material. The light source carrier 103 has a semi-circular concave surface 1031. In other embodiments, the light source carrier 103 also has a bottom surface 1033 relative to the semi-circular concave surface, a first connecting surface 10331 connecting the semi-circular concave surface 1031 and the bottom surface 1033, and a second connecting surface 10332 connecting the semi-circular concave surface 1031 and the bottom surface 1033 and relative to the first connecting surface 10331. In some embodiments, the length of the first connecting surface 10331 and the second connecting surface 10332 in the direction perpendicular to the bottom surface 1033, that is, the thickness of the light source carrier 103, is preferably 60 mm to moderately reduce the volume of the sub-backlight unit 100A. Furthermore, the semi-tubular concave surface 1031 is the Petzval surface of the cylindrical lens 101. A plurality of light strips 1032 extend and are arranged side-by-side along the long side direction of the semi-tubular concave surface 1031 (i.e., the long side direction D1 of the cylindrical lens 101), so that the light rays L1 emitted by the light strips are focused by the cylindrical lens 101 and emitted to form collimated light rays L2. Additionally, a space S is formed between the cylindrical lens 101 and the light source carrier. The first sidewall 1021 and the second sidewall 1022 are located on opposite long sides of this space S to form a sub-backlight unit 100A. In this embodiment, the thickness of the first sidewall 1021 and the second sidewall 1022 can be 0.5 mm to reduce the volume occupied by the sub-backlight unit 100A, but it is not limited to this. The first sidewall 1021 is preferably connected to the first side surface 10131 and the first connecting surface 10331, and the second sidewall 1022 is preferably connected to the second side surface 10132 and the second connecting surface 10332 to prevent light leakage. Furthermore, the first sidewall 1021 is preferably parallel to the second sidewall 1022 to reduce manufacturing difficulty. In another preferred embodiment, the first sidewall 1021 and the second sidewall 1022 may be made of a black light-absorbing material to absorb unwanted stray light and prevent light leakage from the backlight module 10.

[0020] Furthermore, as shown in Figure 1, the number of sub-backlight units is preferably three. For example, sub-backlight unit 100A is adjacent to sub-backlight unit 100B, and sub-backlight unit 100B is adjacent to sub-backlight unit 100C. Sub-backlight unit 100B has a first sidewall 1021B and a second sidewall 1022B opposite to the first sidewall 1021B. Sub-backlight unit 100C has a first sidewall 1021C and a second sidewall 1022C opposite to the first sidewall 1021C. The second sidewall 1022B of sub-backlight unit 100A is adjacent to and parallel to the first sidewall 1021B of sub-backlight unit 100B, and the second sidewall 1022B of sub-backlight unit 100B is adjacent to and parallel to the first sidewall 1021C of sub-backlight unit 100C. In this way, the stereoscopic display unit using these sub-backlight units 100A, 100B and 100C deflects the light emitted by these sub-backlight units through deflection elements and metasurfaces. In addition, by fine-tuning the position of the light strips in these sub-backlight units and adjusting the light emission sequence of the light strips according to the aforementioned eye-tracking technology, the stereoscopic display unit can achieve the effect of eliminating visual convergence-accommodation conflict.

[0021] Figure 5 is a cross-sectional structural schematic diagram of the light strip according to the embodiment of Figure 2. Please refer to Figures 2 to 5. In this embodiment, the light strip 1032 is disposed on the concave curved surface 1031 of the semi-tube. Each light strip 1032 includes, for example, a light strip body 10321, which is made of a rigid material such as metal. The light strip body 10321 further includes a light source setting groove 10322, a circuit board 10323, and a light source 10324. The light source 10324 is disposed on the circuit board 10323, and the circuit board 10323 together with the light source 10324 is disposed in the light source setting groove 10322. The light source 10324 is, for example, mirror-symmetrical about the central axis N of the light strip 1032. In one embodiment, the light source 10324 is preferably a light-emitting diode or a miniature light-emitting diode. The circuit board 10323 and the light source 10324 are electrically connected to an external controller (not shown) so that the user can control whether different light strips 1032 emit light, thereby indirectly controlling the stereoscopic display effect of the stereoscopic display device using these light strips 1032. Furthermore, in a preferred embodiment, a reflective layer 10325 may be selectively added to the light source recess 10322. The reflective layer 10325 is made, for example, by electroplating a metal material, and can further increase the light emission efficiency of the light strip 1032. In another preferred embodiment, the light strip 1032 also includes a diffusion element 10326, which covers the light source 10324 to uniformly diffuse the light emitted by the light source 10324.

[0022] Figure 6 is a schematic diagram simulating the directivity and uniformity of the sub-backlight unit when applied to a stereoscopic display device according to the embodiment of Figure 2, with light deflection angles of 0 degrees and 20 degrees. Please refer to Figures 4 to 6. In the sub-backlight unit 100A, these light strips 1032 are disposed on the semi-tubular concave curved surface 1031 of the light source carrier 103, and the extending direction of these light strips 1032 is parallel to the long side direction D1 of the cylindrical lens 101. However, in another preferred embodiment, the sub-backlight unit 100A may not have a light source carrier 103, and the connecting lines of these light strips 1032 arranged on a virtual cross-section that cuts through the long side direction D1 form the Pessava surface of the cylindrical lens 101, so that the light L1 emitted by these light strips 1032 is focused by the cylindrical lens 101 and emitted to form collimated light L2. In these embodiments, the light rays L1 emitted by these light strips 1032 are incident on the cylindrical lens 101 via the light-incident surface 1011 and exit the cylindrical lens 101 via the light-exiting elongated convex surface 1012 to form collimated light rays L2. The intensity of these collimated light rays L2 measured from the light-exiting elongated convex surface 1012 is preferably within ±2.29 degrees of the half-width at half-maximum (WHM) of the light-exit angle curve. Since this WHM range can achieve extremely high light directivity, when the stereoscopic display device uses the backlight module 10 of the present invention as a backlight source, the stereoscopic display device can avoid crosstalk between different light strips or different images, and can improve angular resolution and image resolution while preserving the field of view, thereby improving the imaging quality of the stereoscopic display device. As shown in Figure 6, when the sub-backlight unit 100A of this embodiment is applied to a stereoscopic display device, and the collimated light L2 passes through the deflection element and the metasurface and its light deflection angle is controlled to be 0 degrees and 20 degrees, the intensity of the collimated light L2 measured at the light-emitting elongated convex curved surface 1012 has a half-width and half-height of ±1.1 degrees and ±1.5 degrees, respectively. This shows that these collimated light rays L2 have high directivity and uniform light intensity, and will not cause crosstalk between images in the stereoscopic display device.

[0023] Figure 7 is a partial cross-sectional enlarged schematic diagram of the light source carrier of the sub-backlight unit according to the embodiment of Figure 4. Please refer to Figures 4, 5 and 7. In detail, in this embodiment, each light strip 1032 is not directly disposed on the incident light surface 1031, but is rotated by a specific angle relative to the incident light surface 1011 (or bottom surface 1033), and the distance between the centers of each light strip 1032 is not necessarily equal. For example, the light strip 1032a is disposed on the semi-tubular concave surface 1031 and the light source (not shown) in the light strip 1032a is located at point A on the semi-tubular concave surface 1031, wherein the normal of the semi-tubular concave surface 1031 at point A is N1, and the normal N1 has a rotation angle θ1 with the vertical line S1 that passes through point A and is perpendicular to the incident light surface 1011 (or bottom surface 1033). Light stripe 1032b is disposed on the concave surface 1031 of the semi-tube, with the light source (not shown) in light stripe 1032b located at point B on the concave surface 1031. The normal of the concave surface 1031 at point B is N2, and the normal N2 has a rotation angle θ2 with the perpendicular line S2 passing through point B and perpendicular to the incident surface 1011 (or bottom surface 1033). Light stripe 1032c is disposed on the concave surface 1031 of the semi-tube, with the light source (not shown) in light stripe 1032c located at point C on the concave surface 1031. The normal of the concave surface 1031 at point C is N3, and the normal N3 has a rotation angle θ3 with the perpendicular line S3 passing through point C and perpendicular to the incident surface 1011 (or bottom surface 1033). In this embodiment, the rotation angle θ1 is not necessarily equal to the rotation angle θ2, the rotation angle θ2 is not necessarily equal to the rotation angle θ3, and the rotation angle θ1 is not necessarily equal to the rotation angle θ3. In addition, the center distance D1 between light stripe 1032a and light stripe 1032b is not necessarily equal to the center distance D2 between light stripe 1032b and light stripe 1032c.

[0024] Please continue to refer to Figures 4, 5 and 7. In this embodiment, the rotation angle of each light strip 1032 (such as the light strips 1032a, 1032b, 1032c mentioned above) and the configuration position of each light strip 1032 on the concave curved surface 1031 of the semi-tube are obtained by reverse ray tracing technology and optimization of the light field pattern of each light strip 1032. For example, it is adjusted by the following relationship 1, but is not limited to it: (Equation 1) where θ is the rotation angle of the light strip 1032 and I(θ) is the light intensity of the light strip 1032 at the rotation angle θ. For example, when the field of view of the stereoscopic display device using the backlight module of the present invention is 40 degrees, the radius of curvature (i.e., c-value) of the light-emitting elongated convex surface 1012 of the cylindrical lens 101 is 0.115 mm, the number of light strips 1032 is 19, and the rotation angle of each light strip 1032 relative to the semi-tubular concave surface 1031 and the position of each light strip 1032 on the semi-tubular concave surface 1031 are shown in Table 1 below. Table 1 serial number exit angle Light bar coordinates (mm) Rotation angle 1 -19.80 (-6.105, -14.805) -35 2 -17.72 (-5.650, -15.510) -32 3 -15.61 (-5.125, -16.162) -28 4 -13.46 (-4.570, -16.885) -twenty four 5 -11.27 (-3.941, -17.541) -20 6 -9.05 (-3.216, -17.952) -16 7 -6.81 (-2.470, -18.426) -12 8 -4.55 (-1.680, -18.832) -8 9 -2.28 (-0.845, -18.947) -4 10 0 (-0.000, -19.039) 0 11 2.27 (0.845, -18.947) 4 12 4.54 (1.680, -18.832) 8 13 6.79 (2.470, -18.426) 12 14 9.01 (3.216, -17.952) 16 15 11.21 (3.924, -17.563) 20 16 13.37 (4.540, -16.870) twenty four 17 15.49 (5.110, -16.225) 28 18 17.56 (5.650, -15.532) 32 19 19.60 (6.056, -14.840) 35 The emission angle represents the angle between the central axis S of the light source 10324 of each light strip 1032 and the normal direction of the light incident surface 1011 of the cylindrical lens 101 (i.e., the direction perpendicular to the light incident surface 1011), which is a fixed value; the light strip coordinate is the position of each light strip 1032 on the semi-tubular concave surface 1031 relative to the center point O of the light incident surface 1011 of the cylindrical lens 101 (shown in Figure 4, as the origin of the coordinate system (0, 0)); the rotation angle is the angle between the normal of each light strip 1032 at the position of the semi-tubular concave surface 1031 (such as points A, B, C) and the vertical line passing through the light source 10324 (such as points A, B, C) and perpendicular to the light incident surface 1011 (or bottom surface 1033) (such as the rotation angles θ1, θ2, θ3 in Figure 7). Taking Figure 7 as an example, when the normal of the light strip 1032 at the setting position of the concave curved surface 1031 of the semi-tube (such as the normals N1, N2, and N3 in Figure 7) is located to the left of the vertical line (such as the vertical lines S1, S2, and S3 in Figure 7) of the light source 10324 relative to the light incident surface 1011 (or bottom surface 1033), the angle value is negative; conversely, when the normal of the light strip 1032 at the setting position of the concave curved surface 1031 of the semi-tube is located to the right of the vertical line of the light source 10324 relative to the light incident surface 1011 (or bottom surface 1033), the angle value is positive.

[0025] In summary, in the backlight module of the present invention, the light source carrier has a semi-circular concave surface, and multiple light strips are provided on the semi-circular concave surface. The light emitted from these light strips enters the cylindrical lens through the light-incident surface and exits the cylindrical lens through the light-exiting elongated convex surface. Furthermore, the half-width at half-maximum (FWHM) of the intensity of these light rays measured from the light-exiting elongated convex surface is within ±2.29 degrees. In this way, the backlight module of the present invention can improve angular resolution and image resolution while retaining the field of view.

[0026] The present invention has been described by the above-described related embodiments; however, the above embodiments are merely examples for implementing the present invention. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. On the contrary, modifications and equivalent settings that fall within the spirit and scope of the claims are included within the scope of the present invention. [Simplified Explanation of the Diagram]

[0008] Figure 1 is a schematic diagram of a backlight module according to an embodiment of the present invention.

[0009] FIG2 is a schematic diagram of the sub-backlight unit according to the embodiment of FIG1.

[0010] Figure 3 is an exploded view of the sub-backlight unit according to the embodiment of Figure 2.

[0011] Figure 4 is a cross-sectional view of the sub-backlight unit along line segment AA' according to the embodiment of Figure 2.

[0012] Figure 5 is a schematic cross-sectional view of the light stripe according to the embodiment of Figure 2.

[0013] Figure 6 is a schematic diagram simulating the directivity and uniformity of the sub-backlight unit in the embodiment of Figure 2 when it is applied to a stereoscopic display device with light deflection angles of 0 degrees and 20 degrees.

[0014] Figure 7 is a partial cross-sectional enlarged schematic diagram of the light source carrier of the sub-backlight unit according to the embodiment of Figure 4.

Claims

1. A backlight module, comprising: At least one sub-backlight unit, each sub-backlight unit comprising: a cylindrical lens having an incident light surface and an emitting elongated convex curved surface relative to the incident light surface; a light source carrier having a semi-concave curved surface, wherein the semi-concave curved surface is a Pessava surface of the cylindrical lens; a plurality of light strips extending side-by-side along the long side of the semi-concave curved surface; and a first sidewall and a second sidewall located on opposite long sides of the space between the cylindrical lens and the light source carrier; wherein each of the light strips has a central axis, the central axis being interposed with a vertical direction perpendicular to the incident light surface by an emission angle, at least a portion of the light strips having an emission angle greater than 0 degrees, the normal of each of the light strips at its position on the semi-concave curved surface being interposed with the vertical direction by a rotation angle, and at least a portion of the light strips having an emission angle less than the rotation angle.

2. The backlight module of claim 1, wherein the light emitted by each of the light strips enters the cylindrical lens through the light-incident surface and exits the cylindrical lens through the light-exiting elongated convex surface to form collimated light rays, and the half-width at half-maximum (WHM) of the spectral curve of the intensity of the collimated light rays versus the light-exit angle measured from the light-exiting elongated convex surface is within ±2.29 degrees.

3. The backlight module of claim 1, wherein the emission angle increases as the light strip moves away from the axis of symmetry of the semi-tube concave surface in a cross section tangential to the long side direction.

4. The backlight module of request item 1, wherein the light incident surface is a plane.

5. The backlight module of claim 1, wherein the cross-sectional shape of the light-emitting elongated convex surface in one of the directions transverse to its long side satisfies the following equation: where (x, z) represents the position on the light-emitting elongated convex surface with the vertex of the light-emitting elongated convex surface as the origin on the virtual plane containing the cross-sectional shape, c is the radius of curvature, and k is the conic constant.

6. The backlight module of claim 1, wherein the cylindrical lens further includes a first side surface connecting the light-incident surface and the light-emitting elongated convex surface, and a second side surface connecting the light-incident surface and the light-emitting elongated convex surface and opposite to the first side surface; the light source carrier further includes a bottom surface opposite to the semi-tube concave surface, a first connecting surface connecting the semi-tube concave surface and the bottom surface respectively, and a second connecting surface connecting the semi-tube concave surface and the bottom surface respectively and opposite to the first connecting surface; and the first sidewall connects the first side surface and the first connecting surface, and the second sidewall connects the second side surface and the second connecting surface.

7. The backlight module of claim 1, wherein each light strip includes a light strip body, the light strip body further includes a light source setting groove and a plurality of light sources, and the light sources are disposed in the light source setting groove.

8. The backlight module of claim 7, wherein each of the light sources is a light-emitting diode or a miniature light-emitting diode.

9. The backlight module of claim 7, wherein the light source setting recess further has a reflective layer to reflect light emitted from the light sources.

10. The backlight module of claim 7, wherein the light strip further includes a diffusion element that covers the light source.

11. The backlight module of claim 1, wherein the first sidewall and the second sidewall are made of black light-absorbing material.

12. The backlight module of claim 1, wherein the first sidewall is parallel to the second sidewall.

13. The backlight module of claim 1, wherein the number of the at least one sub-backlight unit is multiple, and the second sidewall of at least one sub-backlight unit is adjacent to and side-by-side with the first sidewall of another sub-backlight unit.

14. A backlight module, comprising: At least one sub-backlight unit, each sub-backlight unit comprising: a cylindrical lens having an incident light surface and an exiting elongated convex curved surface relative to the incident light surface; a plurality of light strips extending along one long side of the cylindrical lens and arranged side-by-side on one side of the incident light surface of the cylindrical lens, wherein the connecting line of the light strips arranged on a virtual cross-section tangent to the long side direction forms a Pessava surface of the cylindrical lens; and a first sidewall and a second sidewall, respectively located on opposite long sides of the space between the cylindrical lens and the light strips; wherein each of the light strips has a central axis, the central axis being interposed with a vertical direction perpendicular to the incident light surface by an exit angle, at least a portion of the light strips having an exit angle greater than 0 degrees, the normal of each light strip at the location of the semi-tube concave curved surface being interposed with the vertical direction by a rotation angle, and at least a portion of the light strips having an exit angle less than the rotation angle.

15. The backlight module of claim 14, wherein the light emitted by each of the light strips enters the cylindrical lens through the light-incident surface and exits the cylindrical lens through the light-exiting elongated convex surface to form collimated light rays, and the half-width at half-maximum (WHM) of the spectral curve of the intensity of the collimated light rays versus the light-exit angle measured from the light-exiting elongated convex surface is within ±2.29 degrees.

16. The backlight module of claim 14, wherein the emission angle increases as the light strip moves away from the axis of symmetry of the Petzvar surface in the virtual cross-section.

Images