CN115877582A - Polarization beam splitter, optical module and head-mounted display device - Google Patents

Abstract

The embodiment of the application discloses a polarization beam splitter, an optical module and a head-mounted display device; the polarization beam splitter comprises a substrate and a microstructure array arranged on the substrate; the microstructure array is formed by a plurality of microstructure units which are periodically arranged, and any two adjacent microstructure units are arranged at intervals; the microstructure units are nano medium columns with first refractive indexes; the microstructure array is used for splitting incident linearly polarized light in any polarization state into first polarized light and second polarized light, one of the first polarized light and the second polarized light is reflected, and the other of the first polarized light and the second polarized light can transmit.

Description

Polarization beam splitter, optical module and head-mounted display equipment

Technical Field

The application belongs to the technical field of polarized optics, and in particular relates to a polarization beam splitter, an optical module and a head-mounted display device.

Background

For the folded light path scheme, the key process is the performance of the optical film, including the optical film and the bonding process. In the optical film constituting the folded optical path, a polarization splitting film is indispensable, and the polarization splitting film can split one light beam into two polarized light beams orthogonal to each other.

The existing polarization beam splitting films mainly comprise two types: one is a co-extruded stack of polymer film layers, which achieves polarized reflection by means of birefringence interference, and the processing procedure requires stretching the polymer film material in a set direction to increase or decrease the refractive index of the material in that direction, and passing through the stack of hundreds of layers of polymer, which ultimately achieves the function of polarized reflection by means of birefringence interference effect. The disadvantage is that it is difficult to attach the polarizing beam splitting film flat to a curved lens surface, and the stress accumulated during the attachment process affects the index of refraction of the polymer layer, thereby reducing the performance of the polarizing beam splitting film. Another is a metal wire grid polarizer, where the incident light will cause free electrons in the metal wires to oscillate along their length, and this interaction causes re-radiation of light and some energy dissipation by joule heating, in which way the incident light is reflected. For the case where the polarization direction is orthogonal to the metal wire grid, given the small diameter of the metal wire grid, the electric field component of the incident light will not interact with the metal wire grid in the same way and will therefore be fully transmitted without any reflection. Polarization control is to control the amplitude and phase of the electric field in two directions, so different material properties are required in the two directions, and few natural materials can achieve a refractive index difference of more than 10% in two orthogonal directions, so that an ideal platform cannot be provided for polarization control.

Disclosure of Invention

The application aims at providing a polarization beam splitting device, optical module and wear display device, has solved the problem that current polarization beam splitting component can't realize high equivalent refractive index contrast based on the material restriction orthogonal polarization state of focusing.

In order to solve the technical problem, the present application is implemented as follows:

in a first aspect, an embodiment of the present application provides a polarization beam splitter. The polarization light splitting device comprises a substrate and a microstructure array arranged on the substrate;

the microstructure array is formed by periodically arranging a plurality of microstructure units, and any two adjacent microstructure units are arranged at intervals;

the microstructure units are nano medium columns with first refractive indexes;

the microstructure array is used for splitting incident linearly polarized light in any polarization state into first polarized light and second polarized light, one of the first polarized light and the second polarized light is reflected, and the other of the first polarized light and the second polarized light is capable of transmitting.

In a second aspect, an embodiment of the present application provides an optical module. The optical module includes:

a lens group comprising at least one lens; and

the light splitting element, the phase retarder and the polarization reflecting element are arranged in the lens group;

the polarization reflection element adopts the polarization beam splitter as described in the first aspect, and the phase retarder is located between the beam splitter and the polarization beam splitter.

In a third aspect, an embodiment of the present application provides a head-mounted display device. The head-mounted display device comprises the optical module according to the second aspect.

In the embodiments of the present application, there is provided a polarization beam splitter, which is configured by forming a microstructure unit periodically arranged on a substrate, and a birefringence effect required for polarization-type reflection can be generated by an effective refractive index difference caused by anisotropy of the microstructure unit itself; the high equivalent refractive index contrast ratio can be provided between the orthogonal polarization states of light by regulating and controlling parameters such as the number and the size of the microstructure units which are periodically arranged.

Drawings

The above and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram of a polarization beam splitter according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a partial structure of a polarization beam splitter according to an embodiment of the present application;

FIG. 3 is a schematic structural diagram of a microstructure unit according to an embodiment of the present application;

FIG. 4 is a schematic diagram of a polarization beam splitter according to an embodiment of the present application attached to a curved surface;

FIG. 5 is a graph of reflectivity of a polarizing reflective device according to an embodiment of the present application for incident light of different polarization degrees;

fig. 6 is a schematic diagram of a polarization beam splitter according to an embodiment of the present application attached on a plane.

Reference numerals:

10. a substrate; 20. a microstructure unit; 30. a protective layer; 01. a curved surface; 02. and (4) a plane.

Detailed Description

Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.

The features of the terms first and second in the description and in the claims of the present application may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specified. In addition, "and/or" in the specification and claims means at least one of connected objects, a character "/", and generally means that the former and latter related objects are in an "or" relationship.

In the description of the present application, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present application.

In the description of the present application, it is to be understood that the terms "a" and "an" are used herein unless otherwise specifically defined or limited

"mounted," "connected," and "coupled" are to be construed broadly and may include, for example, fixed and fixed connections as well as connections between two elements

Detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly 5 to each other or indirectly through an intermediate medium, or they may be connected internally between the two elements. For the

The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The polarization beam splitter, the optical module and the head-mounted display device provided by the embodiments of the present application are further described below with reference to the accompanying drawings.

According to one embodiment of the present application, there is provided a polarization splitting device, which may be, for example, a composite film layer in a thickness direction. The polarization light splitting device can be applied to a folding light path, and can form an optical module of the folding light path together with a lens, a light splitting element, a phase retarder and the like.

Referring to fig. 1 to 3, the polarization beam splitter provided in the embodiment of the present application includes: the device comprises a substrate 10 and a microstructure array arranged on the substrate 10; the microstructure 5 array is formed by a plurality of microstructure units 20 which are periodically arranged, and any two adjacent microstructure units 20 are arranged at intervals; the microstructure units 20 are nano-medium columns with a first refractive index;

the microstructure array can be used to split incident linearly polarized light of an arbitrary polarization state into first polarized light and second polarized light, one of the first polarized light and the second polarized light being reflected, and the other of the first polarized light and the second polarized light being transmissive.

In the embodiment of the application, a new structural design scheme of the polarization beam splitter is provided. Specifically, the polarization beam splitter may include a substrate 10, and a plurality of microstructure units 20 formed on the substrate 10 and arranged periodically. The substrate 10 may serve as a support for the microstructure unit 20.

Wherein each microstructure unit 20 is designed to have a completely uniform geometric size 5 on the surface of one side of the substrate 10. The microstructure units 20 are nano-medium columns with geometric dimensions

The optical axis angle and other dimensions can be included in the aspect of representing the length, the width and the height. In the embodiment of the present application, for example, each microstructure unit 20 may be designed to have a completely uniform geometric dimension because: when the light wave enters the microstructure unit 20, no extra phase difference is generated on the interface, so that the problem of wave front interference of the diffraction element can be avoided. The concrete can be represented as follows: the polarization beam splitter of the embodiment of the application only changes the propagation direction of incident light, but does not change the shape of the wave front.

For example, when a plane wave enters the polarization beam splitter according to the embodiments of the present application, the reflection component and the transmission component are formed to continue propagating the plane wave along their respective paths without changing the shape of the plane wave. This is advantageous in simplifying the design of an optical system to which the polarization splitting device is applied.

The polarization beam splitter according to the embodiment of the present application has a birefringence effect formed by the difference in anisotropy of the microstructure unit 20 itself, such as the difference in the geometric dimensions of the length L and the width W in the cross section, i.e., the difference in the effective refractive index caused by L ≠ W. In this way, the above-described effects can be achieved without changing the properties of the film material itself by external force stretching. The preparation of the polarization beam splitter becomes more controllable and flexible.

Referring to fig. 1, the microstructure units 20 may be arranged on one side of the substrate 10 in multiple rows and multiple columns according to a set array, and any two adjacent microstructure units 20 are arranged at intervals, so that a plurality of microstructure units 20 are formed on the surface of the substrate 10, and are uniformly arranged, that is, periodically arranged as described above.

In an embodiment of the present application, one of the first polarized light and the second polarized light is, for example, P-polarized light, and the other of the first polarized light and the second polarized light is, for example, S-polarized light.

Natural light is actually composed of many linearly polarized light with different vibration directions. For clarity, the propagation direction of the light is defined as the Z-axis direction in the embodiments of the present application. That is, the light enters the polarization beam splitter in the Z-axis direction, and the polarization beam splitter can split the linearly polarized light into the first polarized light and the second polarized light (i.e., into two polarized lights orthogonal to each other).

For example, light having a polarization vector in the X-axis direction is defined as S-polarized light, and light having a polarization vector in the Y-axis direction is defined as P-polarized light. Specifically, the polarization splitting device according to the embodiment of the present application has a characteristic that it can transmit one of the P-polarized light and the S-polarized light and reflect the other of the P-polarized light and the S-polarized light.

Controlling polarization essentially controls the amplitude and phase of the electric field in two orthogonal directions, and therefore requires different material properties in the two orthogonal directions. However, few natural materials achieve a difference in refractive index of over 10% in two orthogonal directions. In the embodiments of the present application, the anisotropic medium "microstructure unit 20" can provide a high equivalent refractive index contrast between orthogonal polarization states of light through the number, size, and arrangement structure parameter control, thereby providing an ideal platform for polarization control. As a birefringent element, a "microstructure unit 20" having a specifically designed unit structure can be used to achieve polarization control of sub-wavelength pixels.

Wherein the microstructure unit 20 is an artificial optical material having a subwavelength scale structural unit. The microstructure unit 20 can effectively control the amplitude, phase and polarization state of the optical field at the sub-wavelength scale, and has a high application value.

The polarization beam splitter of the embodiment of the application can be directly attached to the surface (which can be a curved surface or a plane) of an optical lens or a plane structure of a lens through optical cement when in use. Wherein the substrate 10 is adapted to bond to a surface of an optical lens while supporting the microstructure array.

According to the polarization beam splitter provided by the embodiment of the application, the periodically arranged microstructure array is formed on the substrate 10, and the birefringence effect required by polarization type reflection can be generated by the effective refractive index difference caused by the anisotropy of the microstructure units, and the polarization beam splitter can be realized without changing the characteristics of the film material by external force stretching. Wherein, high equivalent refractive index contrast can be provided between the orthogonal polarization states of light by adjusting parameters such as the number and the size of the arranged microstructure units 20.

In addition, the microstructure array is, for example, an artificial microstructure array.

In some examples of the present application, referring to fig. 1 and 2, the polarization splitting device may further include a protective layer 30, wherein the protective layer 30 is disposed on one side of the substrate 10 and covers the microstructure array.

Referring to fig. 2, in the polarization beam splitter according to the embodiment of the present application, a protection layer 30 is further disposed on one side of the substrate 10 on which the microstructure array is disposed, and the protection layer 30 is configured to cover and protect each microstructure unit 20.

That is, in the embodiment of the present application, the microstructure array is embedded between the substrate 10 and the protection layer 30, so as to fix the microstructure array and well protect the microstructure array.

Optionally, the microstructure unit 20 is a nano-medium pillar when viewed from the shape. Which can be made of a material having a high refractive index. Such as a high refractive index photoresist, which is not limited in the embodiments of the present application.

In some examples of the present application, the microstructure unit 20 has a size difference in a cross section in a first direction and a second direction, wherein the first direction is different from the second direction.

For example, the microstructure elements 20 themselves have geometric differences in length (e.g., X-axis) and width (e.g., Y-axis) that can create an effective index difference.

Alternatively, the cross section of the microstructure unit 20 is configured to be rectangular or elliptical.

When the cross section of the microstructure unit 20 is rectangular, as shown in fig. 2 and 3, the microstructure unit 20 may have a cubic structure as a whole.

Fig. 2 shows a cross-sectional view of the polarization beam splitter in the XZ plane, and the protective layer 30 is used to completely cover the microstructure unit 20.

With continued reference to fig. 3, the microstructure unit 20 is configured as a cube, and its cross section is rectangular, and its length L and width W are different. In this way, the birefringence effect required for vibration mode reflection can be generated by the difference of effective refractive index indices caused by the difference of the geometric dimensions of the length (X axis direction) and the width (Y axis direction) of the microstructure unit 20 itself, and can be achieved without changing the characteristics of the film material by external force stretching.

Of course, the cross section of the microstructure unit 20 of the embodiment of the present application may also be an ellipse having different sizes in the major axis direction and the minor axis direction.

For example, referring to fig. 3, the microstructure unit 20 has a height H set to 300nm to 800nm; the maximum size of the cross section of the microstructure unit 20 in the first direction is L, the maximum size in the second direction is W, and the L and the W are 50 nm-500 nm.

Referring to fig. 2 and 3, the microstructure unit 20 is, for example, a cubic nano-dielectric cylinder, and its cross section is a regular rectangle. Due to the difference in optical parameters of various dielectric materials, the height H of the microstructure unit 20 may be designed to be 300nm to 800nm, and the maximum size in the length direction and the width direction may be 50nm to 500nm in the cross section thereof. It should be noted that the microstructure units 20 are designed to have different lengths and widths in cross-section, and reference is made to the rectangular or elliptical design.

In some examples of the present application, the microstructure unit 20 includes silicon nitride Si ₃ N ₄ Titanium oxide TiO ₂ At least one of amorphous silicon a-Si and photoresist.

These materials are high refractive index, high transmittance materials; and the material source is wide, the material is easy to obtain, and the production cost cannot be increased.

In some examples of the present application, the substrate 10 and the protective layer 30 are flexible materials.

Referring to fig. 1 and fig. 2, both show the structure of the polarization beam splitter according to the embodiment of the present application, wherein the substrate 10 may be made of a flexible material, for example. The microstructure array may be embedded or arranged in a flexible substrate material to meet the requirement of curved surface attachment, see fig. 5. That is, when the polarization splitting device is to be mounted on the curved surface 01 of the lens, the substrate 10 of the polarization splitting device may be made of a flexible material.

On the basis that the substrate 10 is a flexible material, the protective layer 30 may also be a flexible material.

Alternatively, the flexible material used for the protective layer 30 may be the same substance as the flexible material used for the substrate 10. Of course, other flexible materials may be selected for the protective layer 30.

The protective layer 30 is used to cover and protect the microstructure unit 20. The microstructure units 20 may be made of a material with a high refractive index, such as a high refractive index resist, and are embedded between the substrate 10 and the protective layer 30.

Wherein at least one of the substrate 10 and the protective layer 30 is polymethyl methacrylate or polydimethylsiloxane.

After the materials are used for manufacturing the substrate 10, the formed substrate 10 has better flexibility, which is beneficial to attaching the formed polarization beam splitter on the curved surface 01 of the lens. This design in this application embodiment need not stretch the characteristic change to membrane material itself with the help of external force and realize, and the stress that produces when this kind of curved surface is attached will not influence the optical performance of the polarization beam splitting device that this application embodiment provided.

The microstructure units 20 may be embedded or arranged in a flexible substrate material to meet the requirement of curved surface attachment.

Referring to fig. 4, the polarization beam splitter according to the embodiment of the present application may transmit S-polarized light and reflect P-polarized light, for example. The polarization beam splitter using the flexible material as the substrate 10 will generate a very small stress when the curved surface is attached, and the stress will not have a great influence on the physical size and arrangement of the microstructure array, so that the performance of the whole polarization beam splitter as an optical film will maintain an excellent stable state.

In order to verify the function of the polarization beam splitter provided by the application, the performance of light with different polarization degrees after being incident on the polarization beam splitter is calculated by using a time domain finite difference method. Referring to fig. 5 (a), an angle between the polarization direction of incident light and the Y axis is defined as α, and when α =0 °, the polarization direction is along the Y axis, that is, P-polarized light; when α =90 °, the polarization direction is along the X axis, i.e., S-polarized light. As a result of the calculation, as shown in fig. 5 (b), the polarization beam splitter according to the embodiment of the present application has a transmittance of approximately 100% for S-polarized light and a transmittance of approximately 0% for P-polarized light (a reflectance of approximately 100%). The calculation result conforms to the Malus law.

In some examples of the present application, the substrate 10 is a hard material, the protective layer 30 has a second refractive index, and a set difference is provided between the second refractive index and the first refractive index.

Referring to fig. 6, in the embodiment of the present application, the material of the substrate 10 for supporting the microstructure unit 20 includes, but is not limited to, the flexible material described above. That is, the material of the substrate 10 may also be a hard material. At this time, the microstructure unit 20 may be covered by the protection layer 30, that is, the microstructure unit 20 is embedded between the substrate 10 and the protection layer 30. This solution is more suitable for laminating the flat 02 surfaces of the lenses.

Optionally, the material of the substrate 10 may be glass, and may also be a polymer plastic material, etc. So that the substrate 10 is formed to have a certain support property, which is beneficial to stable adhesion between planes.

It should be noted that the material of the protection layer 30 can be flexibly selected according to the requirement, but a certain difference in refractive index from the microstructure unit 20 needs to be ensured.

For example, if the microstructure unit 20 has a first refractive index and the protective layer 30 has a second refractive index, the first refractive index is greater than the second refractive index. It is of course also possible that the first refractive index is smaller than said second refractive index.

In some examples of the present application, any two adjacent microstructure units 20 have the same interval therebetween.

In a specific example of the present application, referring to fig. 4, the polarization beam splitter includes a substrate 10 and a microstructure array disposed on the substrate 10, and the polarization beam splitter further includes a protection layer 30, where the protection layer 30 is disposed on one side of the substrate 10 and covers the microstructure array, so that the microstructure array is embedded between the substrate 10 and the protection layer 30; the substrate 10 and the protective layer 30 are both made of flexible materials, and the flexible materials used by the substrate 10 and the protective layer may be the same or different; the microstructure array is formed by a plurality of microstructure units 20 which are arranged periodically, and any two adjacent microstructure units 20 have the same interval; the microstructure unit 20 is a nano-medium column with a first refractive index, and the cross section of the microstructure unit 20 has size difference in the length direction and the width direction; the microstructure array is used for splitting incident linearly polarized light in any polarization state into P polarized light and S polarized light, one of the P polarized light and the S polarized light is reflected, and the other of the P polarized light and the S polarized light can transmit.

In the above-mentioned specific example, the polarization beam splitter using a flexible material as the substrate 10 will generate very small stress when it is attached to the curved surface 01 of the lens, and the stress will not have a great influence on the physical size and arrangement of the microstructure units 20 thereon, so that the polarization beam splitter proposed in this embodiment can maintain an excellent stable state.

In another specific example of the present application, referring to fig. 6, the polarization beam splitter includes a substrate 10 and a microstructure array disposed on the substrate 10, and the polarization beam splitter further includes a protection layer 30, where the protection layer 30 is disposed on one side of the substrate 10 and covers the microstructure array, so that the microstructure array is embedded between the substrate 10 and the protection layer 30; the substrate 10 is made of a hard material such as glass or polymer plastic, the microstructure array is formed by periodically arranging a plurality of microstructure units 20, and any two adjacent microstructure units 20 have the same interval therebetween; the microstructure unit 20 is a nano-medium pillar having a first refractive index, and the cross section of the microstructure unit 20 has size differences in the length direction and the width direction, the first refractive index having a difference with a second refractive index of the protective layer 30; the microstructure array is used for splitting incident linearly polarized light in any polarization state into P polarized light and S polarized light, wherein one of the P polarized light and the S polarized light is reflected, and the other of the P polarized light and the S polarized light can transmit.

That is, for the film to be applied on the plane 02 of the lens, the material of the substrate 10 supporting the microstructure array can be selected from thin glass, polymer plastic, etc. The full-plane laminating technology can directly paste the polarization light splitting device on the plane structure of the lens by glue, for example, the polarization light splitting device and the plane structure of the lens can be in a vacuum state during laminating, and therefore bubbles or orange-peel-shaped grains can be prevented from appearing during film pasting.

Optionally, the distance between the centers of any two adjacent microstructure units 20 is the period P of the microstructure unit 20, and the period P is 300nm to 600nm.

In the embodiments of the present application, the period of the microstructure unit 20 can be defined as the distance between the center points of two adjacent microstructure units 20. In consideration of the requirement of human eyes for color separation of three colors of red R, green G and blue B, the microstructure units 20 (nano-media pillars) are designed to be arranged with P as a period, and the size of P is designed to be 300nm to 600nm, for example. The requirements of users on imaging colors can be met on the basis of reducing the production cost.

According to another embodiment of the present application, an optical module is provided. The optical module includes:

a lens group comprising at least one lens; and

the light splitting element, the phase retarder and the polarization reflecting element are arranged in the lens group;

the polarization reflection element adopts the polarization beam splitter as described in any one of the above items, and the phase retarder is located between the beam splitter and the polarization beam splitter.

The optical module that this application embodiment provided is for example a folding light path, and the light that the screen sent can be in beam splitting component with turn back between the polarization beam splitter to obtain good formation of image effect.

According to another embodiment of the present application, there is also provided a head mounted display device. The head-mounted display device comprises the optical module.

It should be noted that, the optical module provided in the embodiment of the present application includes but is not limited to be applied to a head-mounted display device, and may also be applied to other forms of intelligent electronic devices.

In the description herein, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the application, the scope of which is defined by the claims and their equivalents.

Claims (14)

1. A polarization beam splitter is characterized by comprising a substrate (10) and a microstructure array arranged on the substrate (10);

the microstructure array is formed by periodically arranging a plurality of microstructure units (20), and any two adjacent microstructure units (20) are arranged at intervals;

the microstructure units (20) are nano-medium columns with a first refractive index;

the microstructure array is used for splitting incident linearly polarized light in any polarization state into first polarized light and second polarized light, one of the first polarized light and the second polarized light is reflected, and the other of the first polarized light and the second polarized light is capable of transmitting.

2. The polarization splitting device according to claim 1, further comprising a protective layer (30), wherein the protective layer (30) is disposed on one side of the substrate (10) and covers the microstructure array.

3. A polarizing beam splitter according to claim 1, characterized in that the cross-section of the microstructure units (20) has a size difference in a first direction and a second direction, wherein the first direction is different from the second direction.

4. A polarizing beam splitter device according to claim 1, characterized in that the cross-section of the microstructure unit (20) is arranged as a rectangle or an ellipse.

5. The polarization splitting device according to claim 3, wherein the height of the microstructure unit (20) is H, which is set to 300nm to 800nm;

the maximum size of the cross section of the microstructure unit (20) in the first direction is L, the maximum size in the second direction is W, and the L and the W are 50 nm-500 nm.

6. The polarization beam splitter according to claim 1, wherein the microstructure unit (20) comprises silicon nitride (Si) ₃ N ₄ Titanium oxide TiO ₂ At least one of amorphous silicon a-Si and photoresist.

7. A polarization splitting device according to claim 2, wherein the substrate (10) and the protective layer (30) are flexible materials.

8. A polarizing beam splitter device according to claim 2 or 7, wherein at least one of the substrate (10) and the protective layer (30) is polymethyl methacrylate or polydimethylsiloxane.

9. A polarization splitting device according to claim 2, wherein the substrate (10) is a hard material, the protective layer (30) has a second refractive index, and the second refractive index has a set difference from the first refractive index.

10. A polarization splitting device according to claim 2 or 9, wherein the substrate (10) is made of a glass material or a polymer plastic material.

11. The polarization splitting device according to claim 1, wherein any two adjacent microstructure units (20) have the same interval therebetween.

12. The polarization splitting device according to claim 1, wherein the distance between the centers of any two adjacent microstructure units (20) is the period P of the microstructure unit (20), and the period P is set to be 300nm to 600nm.

13. An optical module, comprising:

a lens group comprising at least one lens; and

the light splitting element, the phase retarder and the polarization reflecting element are arranged in the lens group;

the polarization reflection element adopts the polarization splitting device as claimed in any one of claims 1 to 12, and the phase retarder is located between the polarization splitting device and the light splitting element.

14. A head-mounted display device comprising the optical module of claim 13.

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