CN108646466A - Backlight module, LCD display and virtual reality show the helmet - Google Patents

Abstract

The invention relates to the technical field of display screens and virtual reality, in particular to a backlight module, an LCD display screen and a virtual reality display helmet. The backlight module includes a light source module, a first extension panel, a second extension panel and a directional diffusion module. The first expansion panel has a diffractive microstructure or holographic structure on the plane close to the second expansion panel, and the first expansion panel is coated with a total reflection film layer or After the collimated or near-collimated illumination beam provided by the light source module is transmitted and expanded in the vertical direction and the horizontal direction through the first expansion panel and the second expansion panel respectively, the directional diffusion module The direction controls the exit beam angle of the output light, thereby greatly improving the light energy utilization rate of the backlight module, reducing energy consumption and reducing the generation of stray light. The LCD display screen and the virtual reality display helmet include the above-mentioned backlight module.

Description

Backlight module, LCD display and virtual reality display helmet

technical field

The invention relates to the technical field of display screens and virtual reality, in particular to a backlight module, an LCD display screen and a virtual reality display helmet.

Background technique

The virtual content display of the virtual reality display helmet is mainly composed of a display screen and an optical magnifying glass group. Usually, the display screen is an LCD display screen. The display effect of the LCD display has a wide viewing angle characteristic, which can generally reach 160-170 degrees. When a display screen with a wide viewing angle is used in a virtual reality display helmet, usually only light beams within a viewing angle of 30-50 degrees can be received by the user. As shown in FIG. 1 , only light beams in areas A and B of points P1 and P2 on the LCD display screen can be received by human eyes. The light beams in the remaining angle of view form stray light due to scattering, refraction and reflection in the space formed by the display screen and the optical magnifying glass group, which affects the user's reception of virtual reality content. Moreover, the inefficiency of energy utilization of the display screen with a wide viewing angle will lead to an increase in power consumption.

Contents of the invention

In view of this, the object of the present invention is to provide a backlight module, an LCD display screen and a virtual reality display helmet with a small viewing angle, so as to solve the above problems.

To achieve the above object, the present invention provides the following technical solutions:

A preferred embodiment of the present invention provides a backlight module, including a light source module, a first expansion panel, a second expansion panel, and a directional diffusion module;

The light source module is located on the incident light path of the first expansion panel, the second expansion panel is located on the outgoing light path of the first expansion panel, and the directional diffusion module is located on the outgoing light path of the second expansion panel. on the light path;

The plane S131 on the side of the first extension panel close to the second extension panel has a diffractive microstructure or holographic structure that plays a role of transmission diffraction, and the first extension panel has a The plane S132 is coated with a total reflection film or Wherein, β1 is the angle between the collimated or near-collimated beam emitted by the light source module and the plane S131, ns is the refractive index of the material of the first expansion panel, and the plane S131 is parallel to the plane S132;

The second expansion panel has a diffractive microstructure or holographic structure on the plane S151 on the side close to the directional diffusion module, and the second expansion panel is on the plane S152 on the side away from the directional diffusion module. Coated with total reflection coating or Wherein, β2 is the angle between the collimated or near-collimated light beam emitted by the first expansion panel group and the plane S151, ns' is the refractive index of the material of the second expansion panel, and the plane S151 is parallel to the plane S152 ;

The collimated or near-collimated illumination beam provided by the light source module is transmitted and expanded in the vertical direction and the horizontal direction by the first expansion panel and the second expansion panel, respectively, to form a collimated wide beam or a near-collimated illumination beam. Wide beam, the directional diffusion module controls the output beam angle of the output light in the vertical direction and the horizontal direction according to the preset.

Optionally, the plane S131 of the first expansion panel is divided into multiple areas in the Y direction, the transmitted energy of each area of the plane S131 tends to be the same, and the sum of the transmitted energy of all areas of the plane S131 The sum of the total light energy emitted by the light source module and the reflectance and transmittance of each region of the plane S131 is 1.

Optionally, the first expansion panel is used to expand the incident beam in the Y direction, and the second expansion panel is used to expand the incident beam in the X direction, then W=2*H*COSβ1;

Among them, W is the beam aperture of the light source module along the direction perpendicular to the beam incident direction; H is the distance between the upper and lower planes of the first expansion panel along the X direction; β1 is the parallel or nearly parallel output of the light source module Angle between the light beam and the plane S131 of the first expansion panel.

Optionally, the first expansion panel controls the exit beam angle of the output light in the vertical direction to be between 0° and 30°, and the second expansion panel controls the exit beam angle of the output light in the horizontal direction to be 0° to 30°. between 30°.

Optionally, the first expansion panel controls the outgoing beam angle of the output light in the vertical direction to be between 0° and 20°, and the second expansion panel controls the outgoing beam angle of the output light in the horizontal direction to be between 0° and 20°. between 40°.

Optionally, the directional diffusion module is a bidirectional directional diffusion film, or an orthogonally placed bicylindrical lens array, or an orthogonally placed unidirectional directional diffusion film.

Optionally, the directional diffusion module is attached to the second expansion panel.

Another preferred embodiment of the present invention provides an LCD display screen, including a liquid crystal panel and the above-mentioned backlight module.

Optionally, the liquid crystal panel, the directional diffusion module and the second expansion panel are attached to each other.

Another preferred embodiment of the present invention provides a virtual reality display helmet, including the above-mentioned LCD display screen.

The backlight module provided by the preferred embodiment of the present invention integrates and designs the light source module, the first extension panel, the second extension panel, and the directional diffusion module, and uses the first extension panel and the second extension panel to control the light source module. The output beam expands the beam aperture in both vertical and horizontal directions, so the light source module does not need to output a collimated wide beam or a near-collimated wide beam, which makes the optical system structure of the light source module simpler. At the same time, the directional diffusion mode is adopted The output beam angle of the group control output light is small, thereby greatly improving the light energy utilization rate of the backlight module, reducing energy consumption and reducing the generation of stray light.

The LCD display screen and the virtual reality display helmet provided by the preferred embodiment of the present invention include the above-mentioned backlight module, thus having similar beneficial effects.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following will briefly introduce the drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, they can also make From these drawings other related drawings are obtained.

FIG. 1 is a schematic diagram of a wide viewing angle display of a display screen of an existing virtual reality display helmet.

FIG. 2 is a schematic structural diagram of a backlight module provided by a preferred embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a light source module provided by a preferred embodiment of the present invention.

Fig. 4 is a schematic structural diagram of another light source module provided by a preferred embodiment of the present invention.

FIG. 5 is a schematic diagram of light transmission and expansion by the first expansion panel shown in FIG. 2 .

FIG. 6 is a schematic diagram of light transmission and expansion by the second expansion panel shown in FIG. 2 .

FIG. 7 is a numbered diagram of the plane S131 of the first extension panel in the Y direction.

Figure 8 shows that the angle β3 between the incident surface S323 of the second expansion panel and its plane S321 is not schematic diagram.

FIG. 9 is a schematic diagram of a non-light area between output beams when the first expansion panel does not satisfy the condition.

FIG. 10 is a schematic diagram of overlapping areas between output beams when the first expansion panel does not satisfy the condition.

FIG. 11 is a schematic structural diagram of an LCD display screen provided by a preferred embodiment of the present invention.

Icons: 10-backlight module; 11-light source module; 13-first expansion panel; 15-second expansion panel; 17-directional diffusion module; 111-illumination light source; 113-beam shaping beam combiner; Red LED light source; 1112-green LED light source; 1113-blue LED light source; 1131-collimator beam expander shaping component; 1133-beam combination unit; 11311-first collimator beam expander shaper unit; Beam shaping unit; 11313-the third collimating and expanding beam shaping unit; 114-light emitting unit; 115-light collimator; 116-light beam combiner; 117-coupling optical fiber; Device; 1-LCD display screen; 19-LCD panel.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.

It should be noted that like numerals and letters denote similar items in the following figures, therefore, once an item is defined in one figure, it does not require further definition and explanation in subsequent figures. In the description of the present invention, the terms "first", "second", "third", "fourth" and so on are only used for distinguishing descriptions, and should not be interpreted as merely or implying relative importance.

Please refer to FIG. 2 , which is a schematic diagram of a backlight module 10 provided by a preferred embodiment of the present invention. As shown in FIG. 2 , the backlight module 10 includes: a light source module 11 , a first expansion panel 13 , a second expansion panel 15 and a directional diffusion module 17 .

The light source module 11 is located on the incident light path of the first expansion panel 13 and provides collimated or near-collimated illumination beams for the first expansion panel 13 . The light source module 11 may mainly consist of an LED (Light Emitting Diode) light source or an LD (Laser Diode) light source and a collimating lens group, or may mainly consist of a fiber optic light source and a collimating lens group.

For example, as shown in FIG. 3 , when the light source module 11 is mainly composed of an LED (Light Emitting Diode) light source and a collimating lens group, the light source module 11 may include an illumination light source 111 and a beam shaping beam combiner 113 . The illumination light source 111 may be a laser light source, an LED light source, or the like. Optionally, in this embodiment, the illumination light source 111 is an LED light source, and the LED light source may include a red LED light source 1111 , a green LED light source 1112 and a blue LED light source 1113 . In another embodiment, the color of each LED in the LED light source can be set according to actual needs to meet the needs of the actual situation, and no limitation is made here. The beam shaping beam combiner 113 is arranged on the optical path of the illumination light source 111 , and is used for collimating, expanding, shaping and beam combining the beam emitted by the illumination light source 111 . Optionally, in this embodiment, the beam shaping beam combiner 113 includes a collimating beam expanding shaping component 1131 and a beam combining unit 1133 . The collimation beam expansion shaping component 1131 includes a first collimation beam expansion shaping unit 11311 , a second collimation beam expansion shaping unit 11312 and a third collimation beam expansion shaping unit 11313 . Wherein, the first collimating beam expanding and shaping unit 11311 is used for performing collimating beam expanding and shaping processing on the light beam emitted by the red LED light source 1111 . The second collimating beam expanding and shaping unit 11312 is configured to perform collimating, beam expanding and shaping processing on the light beam emitted by the green LED light source 1112 . The third collimating beam expansion and shaping unit 11313 is configured to perform collimation, beam expansion and shaping on the light beam emitted by the blue LED light source 1113 . Normally, the collimation accuracy of the first collimating beam expanding and shaping unit 11311 , the second collimating beam expanding and shaping unit 11312 and the third collimating beam expanding and shaping unit 11313 may be required to be several milliradians. The beam combining unit 1133 is used to combine the beams processed by the first collimating beam expanding and shaping unit 11311, the second collimating beam expanding and shaping unit 11312 and the third collimating beam expanding and shaping unit 11313 into a single beam . Optionally, the beam combining unit 1133 is an x-cube type light combining prism.

For example, as shown in Figure 4, when the light source module 11 is mainly composed of a fiber optic light source and a collimating lens group, the light source module 11 may include a light emitting unit 114, a light collimator 115, a light beam combiner 116, and a coupling fiber 117 And collimating lens group 118. The light emitting unit 114 may adopt a laser light source, an LED light source, or the like. Optionally, in this embodiment, the light emitting unit 114 is an LD laser light source, such as a laser generating device. The laser emitting device may include a fast red laser emitting unit, a green laser emitting unit and a blue laser emitting unit. In other embodiments, the color of each laser emitting unit in the laser generating device can be set according to actual needs to meet the needs of actual conditions, and no limitation is made here. The optical collimator 115 can be an optical collimator lens in the known technology, which is used to reduce the divergence angle of the light beam emitted by the laser generating device. The light beam combiner 116 can be a light combining prism in the known technology, which will not be described in detail here. Coupling fiber 117 may be a multimode fiber or a single mode fiber. The input end of the coupling fiber 117 can be a fused ball lens, which is used to increase the aperture of the laser beam that the coupling fiber 117 can couple, so that the combined beam after passing through the optical beam combiner 116 is easily coupled into the coupling fiber 117 . The output end of the coupling fiber 117 can be processed into a tapered shape, which is used to reduce the beam waist radius of the outgoing beam at the output end and increase the numerical aperture of the outgoing beam, so that the coupling optical fiber 117 outputs a light beam with a small spot and a large exit angle. The collimating lens group 118 is used to collimate the light beam output by the coupling fiber 117 with a small spot and a large exit angle, so as to obtain a collimated light beam or a near-collimated light beam with better directivity. Usually, after passing through the collimator lens group 118, a collimated beam or a near-collimated beam with an outgoing angle in the range of 0°-0.5° can be obtained. In a specific implementation, the beam waist of the beam output by the coupling fiber 117 is set at or near the focal plane of the collimator lens group 118, so as to obtain a collimated beam or a near-collimated beam. When the light emitting unit 114 is a laser light source, the light source module 11 may further include a speckle elimination device 119 . The speckle elimination device 119 interferes with the coherence characteristics of the laser beam by changing the instantaneous phase of the laser beam, thereby weakening the speckle effect of the laser beam and making the energy distribution of the beam provided by the light source module 11 more uniform. The speckle elimination device 119 may be a liquid crystal phase modulator or a vibrating phase plate in the known technology, which is not limited here.

The first expansion panel 13 is used to expand the light beam transmitted from the light source module 11 in the Y direction. The second expansion panel 15 is used to expand the beam transmitted from the first expansion panel 13 in the X direction. Finally, the light source module 11 is jointly expanded by the first expansion panel 13 and the second expansion panel 15 into a collimated or near-collimated wide beam.

The first expansion panel 13 and the second expansion panel 15 are respectively flat plates made of materials with a certain refractive index. As shown in FIG. 5 , the first expansion panel 13 has a diffractive microstructure on a plane S131 near the second expansion panel 15 , and the diffractive microstructure has a transmission and diffraction effect on the incident light beam. The plane S132 of the first extension panel 13 on the side away from the second extension panel 15 can be coated with a total reflection film layer, or β1 can be set to meet the conditions: β1 is the angle between the collimated or near-collimated light beam emitted by the light source module 11 and the plane S131 , that is, the incident angle; ns is the refractive index of the material of the first expansion panel 13 . The plane S131 is parallel to the plane S132. Similarly, as shown in FIG. 6 , the second expansion panel 15 has a diffractive microstructure on the plane S151 near the directional diffusion module 17 , and the diffractive microstructure has a transmission and diffraction effect on the incident beam. The plane S152 of the second extension panel 15 on the side away from the directional diffusion module 17 can be coated with a total reflection film layer, or β2 can be set to meet the conditions: β2 is the angle between the collimated or near-collimated light beams emitted by the first expansion panel 13 and the plane S151 , that is, the incident angle; where ns' is the refractive index of the material of the second expansion panel 15 . The plane S151 is parallel to the plane S152.

Since the second extension panel 15 is similar or identical to the first extension panel 13, to save space, only the first extension panel 13 will be used as an example below for illustration. Similar conclusions.

As shown in FIG. 7 , the plane S131 of the first extension panel 13 has different transmission diffraction efficiencies and zero-order reflection diffraction efficiencies in the Y direction. The first area close to the side of the light source module 11 is recorded as part1, and each area is sequentially recorded as part2, part3, ..., parti, ... along the negative Y direction, and the reflection diffraction efficiency of the parti-th area is is Ri, the transmission diffraction efficiency Dti, and the absorption loss is not considered here, it can be deduced that the transmission energy of the parti region is Ei=R1*R2*...*Ri-1*Dti*E, where E is from the light source module 11 For the total light energy emitted, in order to obtain higher uniformity and higher energy utilization efficiency of the light beam emitted by the first expansion panel 13, the reflection diffraction efficiency and transmission diffraction efficiency of multiple regions need to meet the following conditions:

Ei-Ej→0, i≠j, i=1:n, j=1:n (1)

Dti+Ri=1, i=1:n (3)

Wherein, n indicates that the plane S131 of the first extension panel 13 has a total of n areas in the Y direction.

That is, the transmitted energy of each partition of the plane S131 of the first extension panel 13 tends to be the same, and the sum of the transmitted energy of the plane S131 of the first extension panel 13 tends to the total light energy emitted by the light source module 11 , and the sum of reflectance and transmittance of each partition of plane S131 is 1.

Please refer to FIG. 6 again, when the angle between the incident surface S153 of the second extension panel 15 and its plane S151 is , and when the beam emitted from the first expansion panel 13 is perpendicular to the expansion panel S131, the exit plane S131 of the first expansion panel 13 is parallel to the incident plane S153 of the second expansion panel 15, and there may be a gap or The two fit together.

As shown in FIG. 8, when the angle β3 between the incident surface S323 of the second extension panel 15 and its plane S321 is not , but when the beam emitted from the first expansion panel 13 is perpendicular to the plane S131, there is an angle β4 between the exit plane S131 of the first expansion panel 13 and the incident plane S153 of the second expansion panel 15, ns′ is the refractive index of the material of the second extension panel 15 .

Please refer to FIG. 5 again, when W=2*H*COS(β1), the output beam after expansion by the first expansion panel 13 has high light uniformity and no beam jump occurs. Wherein, W is the beam aperture of the light source module 11 along the direction perpendicular to the incident direction of the beam; H is the distance between the upper and lower planes of the first expansion panel 13 along the X direction; β1 is the parallel output of the light source module 11 Or the included angle between the nearly parallel light beam and the plane S131 of the first expansion panel 13 .

As shown in Figure 9, when W<2*H*COS(β1), the parallel or near-parallel light beam output by the first expansion panel 13 has continuous light energy jumps, the area shown by B1 is the beam exit area, and the area shown by B2 The area shown is a dark area.

As shown in Figure 10, when W>2*H*COS(β1), the parallel or near-parallel light beam output by the first expansion panel 13 has a continuous light energy overlapping area, the area shown by B3 is the beam exit area, and the area shown by B4 The area shown is the beam overlap area. An increase in light energy occurs in this overlap region, which ultimately affects the uniformity of the output beam.

In addition to the diffractive microstructure, the above may also be a holographic structure. That is, the plane S131 of the first expansion panel 13 on the side close to the second expansion panel 15 and the plane S151 of the second expansion panel 15 on the side close to the directional diffusion module 17 may not only have a diffractive microstructure, but also a holographic structure.

The directional diffusion module 17 is arranged on the outgoing light path of the second expansion panel 15 and is an optical film material that has a specific angle diffusion effect on the incident light beam. The directional diffusion module 17 is used to diffuse the outgoing beam in two mutually perpendicular directions. After the outgoing light is diffused by the directional diffusion module 17, the diffusion angle in the vertical Y direction is between 0° and 30°. The diffusion angle in the X direction of the horizontal direction is 0° to 30°, and the diffusion angles in the two directions can also be different. For example, for the human eye, the movement range of the pupil in the horizontal X direction is larger than the movement range of the pupil in the vertical direction Y Large, the diffusion angle of the directional diffusion module 17 in the vertical direction Y direction can be set to be 0° to 20°, while the diffusion angle in the horizontal direction X direction can be set to be 0° to 40°. The directional diffusion module 17 may be an orthogonally placed double cylindrical lens array or a bidirectional directional diffusion film or an orthogonally placed unidirectional directional diffusion film. The unidirectional directional diffusion film can usually be a thin film with micro-cylindrical lens structures distributed in a certain shape or arranged sequentially on the film substrate, and the diameter of the hemisphere of the micro-lens structure can be between several microns to hundreds of microns. The bidirectional directional diffusion film is usually a thin film with microlens structures distributed in a certain shape or arranged sequentially on the film substrate. The diameter of the hemisphere of the microlens structure can be between several microns to hundreds of microns.

In order to reduce the volume, the directional diffusion module 17 can be attached to the second expansion panel 15 .

The backlight module 10 provided by the preferred embodiment of the present invention uses the first extension panel 13 and the second extension panel 13 through the integration and design of the light source module 11, the first extension panel 13, the second extension panel 15 and the The expansion panel 15 expands the beam aperture of the light beam output by the light source module 11 in the vertical and horizontal directions, so the light source module 11 does not need to output a collimated wide beam or a near-collimated wide beam, so that the optical system of the light source module 11 The structure is simpler, and at the same time, the directional diffusion module 17 is used to control the outgoing beam angle of the output light to be smaller, thereby greatly improving the light energy utilization rate of the backlight module 10, reducing energy consumption and reducing the generation of stray light.

Please refer to FIG. 11 , another preferred embodiment of the present invention also provides an LCD display screen 1 , including a liquid crystal panel 19 and the aforementioned backlight module 10 .

The liquid crystal panel 19 is generally composed of polarizers, color filters, liquid crystal molecules, thin film transistors, and polarizers.

In order to reduce the volume, the liquid crystal panel 19 , the directional diffusion module 17 and the second extension panel 15 can be attached to each other in two or three.

The LCD display screen 1 provided by the preferred embodiment of the present invention includes the above-mentioned backlight module 10 , thus having similar beneficial effects.

The LCD display screen 1 provided by the embodiment of the present invention can be applied in occasions where the viewing angle of the LCD display screen 1 is relatively low. For example, the LCD display screen 1 in the virtual reality display helmet does not need a high viewing angle, so the LCD display screen 1 can be applied to the virtual reality display helmet.

Therefore, another preferred embodiment of the present invention also provides a virtual reality display helmet, including the above-mentioned LCD display screen 1 .

The virtual reality display helmet provided by the preferred embodiment of the present invention includes the above-mentioned LCD display screen 1, so it has similar beneficial effects, that is, improving the utilization rate of light energy, reducing energy consumption and reducing the generation of stray light.

Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless expressly stated otherwise, may be replaced by alternative features which are equivalent or serve a similar purpose. That is, unless expressly stated otherwise, each feature is one example only of a series of equivalent or similar features.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A backlight module, characterized in that it comprises a light source module, a first extension panel, a second extension panel and a directional diffusion module; The light source module is located on the incident light path of the first expansion panel, the second expansion panel is located on the outgoing light path of the first expansion panel, and the directional diffusion module is located on the outgoing light path of the second expansion panel. on the light path; The plane S131 on the side of the first extension panel close to the second extension panel has a diffractive microstructure or holographic structure that plays a role of transmission diffraction, and the first extension panel has a The plane S132 is coated with a total reflection film or Wherein, β1 is the angle between the collimated or near-collimated beam emitted by the light source module and the plane S131, ns is the refractive index of the material of the first expansion panel, and the plane S131 is parallel to the plane S132; The second expansion panel has a diffractive microstructure or holographic structure on the plane S151 on the side close to the directional diffusion module, and the second expansion panel has a The plane S152 is coated with a total reflection film or Wherein, β2 is the angle between the collimated or near-collimated light beam emitted by the first expansion panel group and the plane S151, ns' is the refractive index of the material of the second expansion panel, and the plane S151 is parallel to the plane S152 ; The collimated or near-collimated illumination beam provided by the light source module is transmitted and expanded in the vertical direction and the horizontal direction by the first expansion panel and the second expansion panel, respectively, to form a collimated wide beam or a near-collimated illumination beam. Wide beam, the directional diffusion module controls the output beam angle of the output light in the vertical direction and the horizontal direction according to the preset. 2. The backlight module according to claim 1, wherein the plane S131 of the first expansion panel is divided into a plurality of areas in the Y direction, and the transmitted energy of each area of the plane S131 tends to be the same, And the sum of the transmitted energy of all areas of the plane S131 tends to the total light energy emitted by the light source module, and the sum of the reflectance and transmittance of each area of the plane S131 is 1. 3. The backlight module according to claim 1, wherein the first expansion panel is used to expand the incident light beam in the Y direction, and the second expansion panel is used to expand the incident light beam in the X direction , then W=2*H*COSβ1; Among them, W is the beam aperture of the light source module along the direction perpendicular to the beam incident direction; H is the distance between the upper and lower planes of the first expansion panel along the X direction; β1 is the parallel or nearly parallel output of the light source module Angle between the light beam and the plane S131 of the first expansion panel. 4. The backlight module according to claim 1, wherein the first expansion panel controls the outgoing beam angle of the output light in the vertical direction to be between 0° and 30°, and the second expansion panel is between 0° and 30°. The horizontal direction controls the output beam angle of the output light to be between 0° and 30°. 5. The backlight module according to claim 1, wherein the first expansion panel controls the output beam angle of the output light in the vertical direction to be between 0° and 20°, and the second expansion panel is between 0° and 20°. The horizontal direction controls the outgoing beam angle of the output light to be between 0° and 40°. 6. The backlight module according to any one of claims 1-5, wherein the directional diffusion module is a bidirectional directional diffusion film, or a double cylindrical lens array placed orthogonally, or an orthogonal Placed unidirectional directional diffusion membrane. 7. The backlight module according to any one of claims 1-5, wherein the directional diffusion module is attached to the second expansion panel. 8. An LCD display, characterized in that it comprises a liquid crystal panel and the backlight module according to any one of claims 1-7. 9. The LCD display screen according to claim 8, wherein the liquid crystal panel, the directional diffusion module and the second expansion panel are attached to each other. 10. A virtual reality display helmet, characterized in that it comprises the LCD display screen according to claim 8.