WO2024235269A1 - Light-emitting element and projection apparatus - Google Patents

Abstract

A projection apparatus (1), comprising: a light source module (10), which emits projected light rays having rotating circularly polarized light; a lens module (20), which is arranged on the path of the projected light rays from the light source module (10) and receives the projected light rays; and an optical path folding assembly (30), wherein the structure of the optical path folding assembly (30) close to the light source module (10) has a chiral structure with spin properties when viewed from the direction of the projected light rays. The rotating circularly polarized light of the projected light rays and the chiral structure with spin properties have opposite rotation directions, thus enabling the function of selectively transmitting the projected light rays from the light source module (10) in a directional manner, and thereby implementing folding of the projected light rays from the light source module (10).

Description

Light emitting element and projection device Technical Field

The present application relates to a light emitting element, and more particularly to a light emitting element and a projection device.

Background Art

A virtual head-mounted display is a visual optical system that projects the image or data information of a microdisplay into the pupil of the human eye. According to the different projection methods, head-mounted displays are divided into eyepiece head-mounted displays and projection head-mounted displays. The eyepiece head-mounted display places the image within the focal length of the optical system to produce an enlarged virtual image, and forms a system exit pupil at the pupil of the human eye through refraction or reflection by the subsequent lens group. The exit pupil position coincides with the aperture stop position of the optical system. The projection head-mounted display consists of a microdisplay, a projection optical system, a beam splitter, and a retroreflective screen. The image of the microdisplay is placed outside the focal length of the projection optical system to produce an enlarged real image, which is reflected by the beam splitter to the retroreflective screen. Due to the special material of the retroreflective screen, the light returns along the original path and is transmitted through the beam splitter to form a system exit pupil, which ultimately allows the user to view the image. Compared with the eyepiece head-mounted display, the projection head-mounted display can provide a clearer picture.

An augmented reality head-mounted display is also a visual optical system that projects the image or data information of a microdisplay into the pupil of the human eye. The user also needs to see the external real environment to provide a sense of augmented reality. The augmented reality head-mounted display requires the user to wear it frequently to provide an immersive sense of augmented reality.

With the development of science and technology, the optoelectronic industry has higher and higher performance requirements for optical systems. Both virtual head-mounted displays and augmented reality head-mounted displays need to develop in the direction of miniaturization and high performance, which requires the corresponding optical systems to achieve high imaging quality with a compact structure. Head-mounted display is a typical modern optoelectronic display system, which has great application value and market in multimedia entertainment, military, industry, medical, virtual reality and augmented reality. Both augmented reality head-mounted display and virtual head-mounted display are projection devices. Consumers now require that such head-mounted projection devices can provide the characteristics of comfortable wearing, compact structure, small size, high imaging quality and the largest possible field of view.

Summary of the invention

In response to the above problems, the present application provides a projection device, comprising a light source module, wherein the light source module emits projection light with rotated circularly polarized light, a lens module, wherein the lens module is arranged on the projection light path of the light source module, the lens module receives the projection light, and a folded light path component. When viewed along the direction of the projection light, a spin-like chiral structure exists in the structure of the folded light path component close to the light source module, and the spin direction of the rotated circularly polarized light of the projection light is opposite to the spin direction of the spin-like chiral structure, thereby achieving the function of directional selective transmission of the projection light of the light source module, so as to achieve the folding of the projection light of the light source module.

In one embodiment, the folded light path component is provided with a cholesteric liquid crystal layer, which has a spin-like chiral structure and is in a multi-domain state. A spiral structure exists in each domain. The cholesteric liquid crystal layer is arranged in a direction close to the light source module. The rotation direction of the projected light received by the cholesteric liquid crystal layer is opposite to the rotation direction of the spin-like chiral structure. The cholesteric liquid crystal layer can pass the projected light of the rotated circularly polarized light emitted by the light source module in a certain direction. By directional passing of the projected light by the cholesteric liquid crystal layer, the folded light path component can achieve the effect of directional passing of the rotated circularly polarized light. Compared with the semi-reflective and semi-transparent film formed by the coating process, although the size of the cholesteric liquid crystal material is increased, the cost of the cholesteric liquid crystal material is lower, the manufacturing process is simpler, and a cheaper technical solution can be provided.

In view of the above problems, the present invention provides a projection device including a light source module, which emits projection light with rotated circularly polarized light, a lens module, which is arranged on the projection light path of the light source module, and the lens module receives the projection light, and a folded light path component, wherein a portion of the folded light path component is arranged on a surface of the lens module away from the light source module, and a portion of the folded light path component is arranged on a surface of the lens module close to the light source module, the folded light path component forms a folded optical path between a surface away from the light source module and a surface close to the light source module, the portion of the folded light path component close to the light source module can transmit the rotated circularly polarized light, the folded light path component can convert the rotated circularly polarized light into linearly polarized light, the portion of the folded light path component away from the light source module can transmit the linearly polarized light, and a portion of the folded light path component is arranged on a flat optical surface of the lens module, thereby improving the assembly yield of the projection device.

In one embodiment, the lens module of the projection device includes a first lens, a second lens The projection device is provided with a first lens and a third lens, wherein the first lens is arranged in a direction away from the light source module, the third lens is arranged in a direction close to the light source module, the second lens is arranged between the first lens and the third lens, the first lens has at least one flat optical surface, and the second lens and the third lens have at least one flat optical surface, thereby improving the assembly yield of the projection device.

In one embodiment, the folded optical path component includes a semi-reflective and semi-transparent film, a quarter-wave plate, a polarization beam splitter and a polarizer. Along the direction of the projected light, the semi-reflective and semi-transparent film, the quarter-wave plate, the polarization beam splitter and the polarizer are sequentially arranged on the lens module. The polarization beam splitter and the polarizer are attached together to form a planar composite film material. The polarization beam splitter and the polarizer are arranged on a flat optical surface of the lens module, and the quarter-wave plate is arranged on another flat optical surface of the lens module, thereby increasing the attachment yield of the folded optical path component and improving the assembly yield of the projection device.

Further objectives and advantages of the present application will be fully reflected through understanding of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

By describing the embodiments of the present application in more detail in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present application will become more apparent. The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

FIG. 1 shows a schematic structural diagram of a projection device according to a first embodiment of the present application.

FIG. 2 is a schematic diagram showing the optical path of a folding assembly according to an embodiment.

FIG. 3A is a schematic structural diagram of a folding assembly and a lens module according to an embodiment.

FIG. 3B is a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 3C shows a schematic structural diagram of a folding assembly and a lens module according to yet another embodiment.

FIG. 3D shows a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 3E shows a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 3F shows a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 4 is a schematic diagram showing the optical path of a folding assembly according to another embodiment.

FIG. 5 is a schematic diagram showing the optical path of a folding assembly according to another embodiment.

FIG. 6 is a schematic structural diagram of a folding assembly and a lens module according to an embodiment.

FIG. 7 shows a flow chart of a method for assembling a folding assembly and a lens module according to an embodiment.

FIG. 8 is a schematic structural diagram of a folding assembly and a lens module according to an embodiment.

FIG. 9 shows a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 10 is a flow chart showing a method for assembling a folding assembly and a lens module according to another embodiment.

FIG. 11 is a schematic diagram showing the optical path of a folding assembly according to another embodiment.

FIG. 12 is a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 13 shows a schematic structural diagram of a folding assembly and a lens module according to another embodiment.

FIG. 14 is a schematic diagram showing the optical path of a folding assembly according to another embodiment.

DETAILED DESCRIPTION

Below, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described here.

In the description of the present invention, it should be noted that directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of narrating the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of the present invention.

It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

The terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, It can also be a detachable connection or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or a contact connection or an indirect connection through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

Figure 1 illustrates an embodiment of the projection device of the present application, wherein the projection device 1 includes a light source module 10 and a lens module 20, wherein the light source module 10 is used to emit an incident light signal, and the lens module 20 is used to receive the incident light signal emitted from the light source module 10 to form a projection light signal, and finally project the light.

Still referring to FIG. 1 , the lens module 20 of this embodiment includes a first lens 201, a second lens 202 and a third lens 203, wherein the third lens 203 is close to the light source module 10, the first lens 201 is arranged in a direction away from the light source module 10, and the second lens 202 is arranged between the first lens 201 and the third lens 203.

In this embodiment, the projection device also includes a folding light path component 30, wherein the folding light path component 30 is disposed on the lens module 20, and the folding light path component 30 is used to realize the folding of the light emitted by the light source module 10 within the lens module 20 to increase the distance of the light, thereby being able to reduce the size of the projection device 1.

2 illustrates an implementation of a folded optical path component 30 of the present application, wherein the folded optical path component 30 includes a semi-reflective semi-transparent film 304, a quarter wave plate 303, a polarizing beam splitter 302, and a polarizer 301, wherein the semi-reflective semi-transparent film 304 performs an optical effect of semi-reflecting and semi-transmitting the light emitted by the light source module 10. In this embodiment, the semi-reflective semi-transparent film 304 is configured by stacking tio2 (titanium dioxide), nbox (niobium oxide) and sio2 (silicon dioxide), and in this embodiment, the reflectivity of the semi-reflective semi-transparent film 304 for visible light is not less than 25% and not more than 75%.

The quarter wave plate 303 is a birefringent single crystal wave plate of a certain thickness. When light passes through the quarter wave plate 303 from normal incidence, the phase difference between the ordinary light (o light) and the extraordinary light (e light) will be equal to π/2 or an odd multiple thereof. Such a chip is called a quarter wave plate or simply a 1/4 wave plate. When linearly polarized light is incident vertically on the quarter wave plate 303, and the polarization direction of the light forms an angle θ with the optical axis plane (vertical to the natural cleavage plane) of the quarter wave plate 303, the light will become elliptically polarized light after exiting the quarter wave plate 303. In particular, when θ=45°, the light exiting the quarter wave plate 303 will turn back into circularly polarized light. The fast axis and slow axis of the quarter wave plate 303 are related to the type of crystal. Generally speaking, Ve>Vo of a negative crystal, the optical axis direction of the quarter wave plate 303 is parallel to the plane of the quarter wave plate 303, and the optical axis direction of a quarter wave plate made of a negative crystal is In the fast axis direction, the fast axis direction of the positive crystal is perpendicular to the optical axis direction and is located in the plane of the quarter wave plate. According to design requirements, the quarter wave plate 303 can be selected as a negative crystal or a positive crystal.

The polarization beam splitter 302 serves to split the incident light according to a certain percentage of reflected and transmitted light according to the corresponding polarization state of the light.

The main function of the polarizer 301 is to selectively transmit certain polarized light, so that the light passing through the polarizer 301 becomes polarized light of certain states.

In this embodiment, the light projected by the light source module 10 is itself left-handed polarized light. After the projected light passes through the semi-reflective semi-transparent membrane 304, about 50% of the left-handed polarized light will pass through the semi-reflective semi-transparent membrane 304. After the 50% left-handed polarized light passes through the quarter-wave plate 303, the left-handed polarized light will be processed into P linear polarized light at an angle of +45° to the fast axis of the quarter-wave plate 303. The polarization direction of the P linear polarized light is parallel to the reflection axis of the polarization beam splitter 302. The reflected light generated after the P linear polarized light is reflected by the polarization beam splitter 302 is at an angle of -45° to the fast axis of the quarter-wave plate 303, thereby the light is converted into left-handed circularly polarized light. After the left-handed circularly polarized light reaches the semi-reflective semi-transparent membrane 304, about 50% of the light will be reflected (thereby the energy of the light becomes 25% of the initial light energy). Since the light of the quarter-wave plate 303 at this time The axis is reversed, and the reflected light will become right-handed circular polarized light. After passing through the quarter wave plate 303, the right-handed circular polarized light will be converted into linear polarized light. The polarization direction of the light is -45° (45° counterclockwise for the fast axis) with the fast axis of the quarter wave plate 303. At this time, the polarization direction of the light is consistent with the transmission direction of the polarization beam splitter 302, and the light is consistent with the transmission axis direction of the polarization beam splitter 302. Therefore, the light can pass through the polarization beam splitter 302, and finally the light is emitted through the polarizer 301. The light emitted by the light source module 10 can be folded back by the folded optical path component 30 in the lens module 20, so that the lens module 20 can reflect the light multiple times, so that the light can pass through multiple optical curved surfaces, so that the light can be modulated multiple times. Compared with the solution of directly penetrating the lens module, this embodiment can greatly shorten the size of the lens module. In this embodiment, the gap between the components in the folded optical path component 30 is increased, thereby increasing the optical path of the light to shorten the total path of the optical system.

Still referring to FIG. 1 , FIG. 1 illustrates an embodiment of the projection device of the present application, wherein the lens module 20 has the first lens 201, the second lens 202 and the third lens 203 in sequence from the end away from the light source module 10 to the end close to the light source module 10, wherein the second lens 202 and the third lens 203 are glued together by transparent glue, and the light transmittance of the glue between the second lens 202 and the third lens 203 is greater than 90%, thereby improving the system integration and shortening the size of the projection device 1.

In this embodiment, the surface of the first lens 201 away from the projection light end is the first surface 2011, the surface of the first lens 201 close to the projection light end is the second surface 2012, the surface of the second lens 202 away from the projection light end is the third surface 2021, the surface of the second lens 202 close to the projection light end is the fourth surface 2022, the surface of the third lens 203 away from the projection light end is the fifth surface 2031, and the surface of the second lens 203 close to the projection light end is the sixth surface 2032. The polarizer 301 and the polarization beam splitter 302 are superimposed on the first surface 2011 in the order shown in FIG. 2, and the polarizer 301 is located at a position farther away from the projection light end, so as to improve the packaging integration of the optical machine module and shorten the size of the projection device.

The second surface 2012 of the first lens 201 is a convex surface, and the third surface 2021 of the second lens 202 is a concave surface. The shapes of the third surface 2021 and the second surface 2012 are roughly complementary, that is, the convex surface of the second surface 2012 can be roughly nested into the concave surface of the third surface 2021, thereby reducing the aberration of the projected image, improving the image quality of the projected image, and reducing the size.

The fourth surface 2022 of the second lens 202 is also a plane, and the third surface 2021 of the second lens 201 is a concave surface, which can reduce the aberration of the projected image, improve the quality of the projected image, and reduce the size.

The fifth surface 2031 of the third lens 202 is also a plane, and the sixth surface 2032 of the third lens is a convex surface, thereby reducing the aberration of the projected image, improving the quality of the projected image, and reducing the size.

The second lens 202 and the third lens 203 mentioned above are glued together by a glue layer 305. In this embodiment, the quarter wave plate 303 is attached between the second lens 202 and the third lens 203. The glue layer 305 is arranged between the quarter wave plate 303 and the fourth surface 2022. The glue layer 305 is also arranged between the quarter wave plate 303 and the fifth surface 2031. The glue layer 305 can be used to attach the quarter wave plate 303 to the planar fourth surface 2022 and the planar fifth surface 2031, thereby improving the yield rate of the installation of the quarter wave plate 303.

In this embodiment, the semi-reflective and semi-transparent membrane 304 is arranged on the outer side of the sixth surface 2032. In this embodiment, the semi-reflective and semi-transparent membrane 304 can reflect 40% and transmit 60% of the light emitted by the light source module 10, or can reflect 60% and transmit 40%. In this embodiment, it is preferred to reflect 50% and transmit 50%, so as to improve the brightness utilization rate of the projected image.

In this embodiment, the semi-reflective and semi-transparent membrane 304 is formed on the surface of the second lens close to the projected light (the sixth surface 2032) by vapor deposition. By vapor deposition, chemical molecules or atoms are evaporated and formed on the sixth surface 2032, so the semi-reflective and semi-transparent membrane 304 does not have an angle problem of assembly tilt relative to the sixth surface 2032.

The polarizer 301 and the polarization beam splitter 302 are substantially flat before being assembled into the lens module 20. The plate-shaped film material, the polarizer 301 is attached to the polarization beam splitter 302, and the polarizer 301 is farther away from the projection light direction than the polarization beam splitter 302. The polarization beam splitter 302 is attached to the first surface 2011, and the flatness of the first surface 2011 is less than 5μm (the actual surface of the first surface 201 can be compared with the ideal plane, and the line value distance between the two is the flatness error value, and 20-100 points of the first surface 2011 can be taken for measurement and comparison).

In this embodiment, the polarizer 301 and the polarization beam splitter 302 are planar film materials before assembly. When the planar film material is attached to the curved surface, the planar film material may be wrinkled after bending. On the other hand, the curved surface shape of the lens itself will also have an error with the designed shape. After the polarizer 301 and the polarization beam splitter 302 are attached, the angle of the quarter wave plate 303 after assembly will also deviate due to the deviation of the curved surface from the design value, resulting in an error in the assembly angle of the quarter wave plate 303, thereby affecting the projection effect. In this embodiment, the polarizer 301 and the polarization beam splitter 302 are attached to the first plane of the plane, which can improve the assembly yield. In other words, this embodiment ultimately makes the flatness of the polarizer 301 on the surface away from the light source module 10 less than 7μm (the actual surface of the first surface 2011 can be compared with the ideal plane, and the line value distance between the two is the flatness error value, and 20-100 points of the first surface 2011 can be taken for measurement and comparison).

In this embodiment, the curvature radius of the second surface 2012 and the third surface 2021 is a spherical or aspherical surface with a negative value, and the curvature radius of the sixth surface 2032 is a spherical or aspherical surface with a negative value, thereby reducing the aberration of the projected image, improving the quality of the projected image, and shortening the size of the optical machine module.

In this embodiment, the first lens 201 and the third lens 203 are made of high refractive index materials with a refractive index of 1.7-1.8. The second lens 202 is made of low refractive index materials with a refractive index of 1.60-1.65, thereby optimizing the optical design of the optical machine and shortening the size of the optical machine module.

In the prior art, the core of the quarter wave plate 303 is to control the phase delay of the wavelength. The preparation of the quarter wave plate 303 is generally achieved by bonding multiple uniaxial wafers, or by precisely designed metamaterials and metasurfaces. The assembly position of the quarter wave plate 303 is to be attached and installed according to the phase angle relationship between the absorption axis and the transmission axis. Since the relative angle between the absorption axis and the transmission axis is required to be accurately around 90°, the quarter wave plate is very sensitive to the assembly angle. In this embodiment, the assembly angle limit value of the quarter wave plate 303 is within 3 degrees. In order to obtain a better projection effect, the assembly angle error of the quarter wave plate 303 is often required to be within 1 degree. In this embodiment, the quarter wave plate 303 is assembled on the fourth surface 2022 of the plane and the fifth surface 2031 of the plane, so a higher flatness can be obtained. If the quarter wave plate 303 is attached to a curved surface, on the one hand, since the quarter wave plate 303 is a flat film material before assembly, it is attached to the curved surface. On the one hand, the flat film material may wrinkle after bending. On the other hand, the curved surface shape of the lens itself may deviate from the designed shape. After the quarter wave plate 303 is attached, the curved surface itself deviates from the designed value, which causes the angle of the quarter wave plate 303 after assembly to deviate, resulting in an error in the assembly angle of the quarter wave plate 303, thereby affecting the projection effect.

It can be obtained that the present embodiment proposes a projection device 1, comprising a light source module 10, wherein the light source module 10 emits a projection light with a rotated circularly polarized light, a lens module 20, wherein the lens module 20 is arranged on the projection light path of the light source module 10, wherein the lens module 20 receives the projection light, and a folded light path component 30, wherein a portion of the folded light path component 30 is arranged on a surface of the lens module 20 away from the light source module 10, wherein a portion of the folded light path component 30 is arranged on a surface of the lens module 20 close to the light source module 10, wherein the folded light path component 30 forms a surface away from the light source module 20 and The folded optical path between the surfaces close to the light source module 10, the portion of the folded optical path component 30 close to the light source module 10 can transmit the rotated circularly polarized light, the folded optical path component 30 can convert the rotated circularly polarized light into linearly polarized light, the portion of the folded optical path component 30 away from the light source module 10 can transmit the linearly polarized light, and the portion of the folded optical path component 30 is arranged on the flat optical surface of the lens module 20. By increasing the attachment accuracy of the elements of the folded optical path component 30 and reducing the error with the design, the assembly accuracy of the folded optical path component 30 is improved, thereby improving the production yield of the projection device 1.

FIG3A illustrates an implementation of a lens module of the present application, wherein the lens module 20A comprises a first lens 201A, a second lens 202A, and a third lens 203A, from the end farthest from the projection light end to the end close to the projection light end, wherein the second lens 202A and the third lens 203A are connected together by a bonding layer 305A, thereby improving system integration and shortening the size of the optical-mechanical module.

In this embodiment, the first lens 201A and the second lens 202A are also bonded together by a bonding layer 305A, thereby realizing that the first lens 201A, the second lens 202A and the third lens 203A are connected and combined into a whole, so as to enhance the reliability of the lens module 20A.

The surface of the first lens 201A close to the projection light end is concave, and the surface of the first lens 201A away from the projection light end is flat, thereby reducing the aberration of the projection image, improving the image quality of the projection image, and shortening the size of the optical machine module.

The surface of the second lens 202A close to the projection light end is a plane, and the surface of the second lens 202A far from the projection light end is a convex surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the third lens 203A close to the projected light end is convex. The surface of the projection light end is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

In this embodiment, the surface of the first lens 201A away from the projection light end is the first surface 2011A, the surface of the first lens 201A close to the projection light end is the second surface 2012A, the surface of the second lens 202A away from the projection light end is the third surface 2021A, the surface of the second lens 202A close to the projection light end is the fourth surface 2022A, the surface of the third lens 203A away from the projection light end is the fifth surface 2031A, and the surface of the second lens 203A close to the projection light end is the sixth surface 2032A. The polarizer 301A and the polarization beam splitter 302A are sequentially stacked on the first surface 2011A, and the polarizer 301A is located at a position farther away from the projection light end, so as to improve the packaging integration of the projection device and shorten the size of the optical machine module.

In this embodiment, the quarter wave plate 303A is still attached to the planar fourth surface 2022A and the planar fifth surface 2031A, and a high flatness can still be obtained to improve the assembly yield of the quarter wave plate 303A, and ultimately improve the projection effect of the projection device.

In this embodiment, the polarizer 301A and the polarization beam splitter 302A are attached to the planar first surface 2011A, which can achieve a higher flatness, thereby improving the assembly yield of the polarizer 301A and the polarization beam splitter 302A, and ultimately improving the projection effect of the projection device.

In this embodiment, the curvature radius of the second surface 2012A and the third surface 2021A is a spherical or aspherical surface with a positive value, and the curvature radius of the sixth surface 2032A is a spherical or aspherical surface with a negative value, thereby reducing the aberration of the projected image, improving the quality of the projected image, and shortening the size of the optical machine module.

In this embodiment, the first lens 201A and the third lens 203A are made of high refractive index materials with a refractive index of 1.7-1.8, and the second lens 202A is made of low refractive index materials with a refractive index of 1.60-1.65, thereby optimizing the optical design of the optical machine and shortening the size of the optical machine module.

FIG3B illustrates another embodiment of the lens module of the present application, wherein the lens module 20B comprises a first lens 201B, a second lens 202B and a third lens 203B in order from the end farthest from the projection light end to the end close to the projection light end, wherein the second lens 202B and the third lens 203B are connected together by a bonding layer 305B, thereby improving the system integration and shortening the size of the optical-mechanical module.

In this embodiment, the surface of the first lens 201B away from the projection light end is the first surface 2011B, the surface of the first lens 201B close to the projection light end is the second surface 2012B, the surface of the second lens 202B away from the projection light end is the third surface 2021B, the surface of the second lens 202B close to the projection light end is the fourth surface 2022B, the surface of the third lens 203B away from the projection light end is the fifth surface 2031B, and the surface of the second lens 203B close to the projection light end is the sixth surface The polarizer 301B and the polarization beam splitter 302B are sequentially stacked on the first surface 2011B, and the polarizer 301B is located at a position farther away from the projection light end, so as to improve the packaging integration of the projection device and shorten the size of the optical-mechanical module.

The second surface 2012B of the first lens 201B is a concave surface, and the third surface 2021B of the second lens 202B is a convex surface. The shapes of the third surface 2021B and the second surface 2012B are roughly complementary, that is, the concave surface of the second surface 2012B can be roughly complementary to the convex surface of the third surface 2021B, thereby reducing the aberration of the projected image, improving the image quality of the projected image, and reducing the size.

The fourth surface 2022B of the second lens 202B is also a plane, and the third surface 2021B of the second lens 201B is a convex surface, which can reduce the aberration of the projected image, improve the quality of the projected image, and reduce the size.

The fifth surface 2031B of the third lens 203B is also a plane, and the sixth surface 2032B of the third lens 203B is a convex surface, thereby reducing the aberration of the projected image, improving the quality of the projected image, and reducing the size.

In this embodiment, the quarter wave plate 303B is attached to the planar fourth surface 2022B and the planar fifth surface 2031B through the adhesive layer 305B, and a high flatness can still be obtained to improve the assembly yield of the quarter wave plate 303B, and ultimately improve the projection effect of the projection device.

In this embodiment, the polarizer 301B and the polarization beam splitter 302B are attached to the planar first surface 2021B, which can achieve a higher flatness, thereby improving the assembly yield of the polarizer 301B and the polarization beam splitter 302B, and ultimately improving the projection effect of the projection device.

In this embodiment, the curvature radius of the second surface 2012B and the third surface 2021B is a spherical or aspherical surface with a positive value, and the curvature radius of the sixth surface 2032B is a spherical or aspherical surface with a negative value, thereby reducing the aberration of the projected image, improving the quality of the projected image, and shortening the size of the optical machine module.

In this embodiment, the first lens 201B and the third lens 203B are made of high refractive index materials with a refractive index of 1.7-1.8, and the second lens 202B is made of low refractive index materials with a refractive index of 1.60-1.65, thereby optimizing the optical design of the optical machine and shortening the size of the optical machine module.

FIG3C illustrates another embodiment of a lens module 20C of the present application, wherein the lens module 20C comprises a first lens 201C, a second lens 202C and a third lens 203C in sequence from the end farthest from the projection light end to the end close to the projection light end, wherein the third lens 203C and the second lens 202C are connected together by a bonding layer 305C, thereby improving the system integration and shortening the size of the optical-mechanical module.

For the sake of simplicity, the surface of the first lens away from the projection light end is the first surface 2011C. The surface of the first lens close to the projection light end is the second surface 2012C, the surface of the second lens away from the projection light end is the third surface 2021C, the surface of the second lens close to the projection light end is the fourth surface 2022C, the surface of the third lens away from the projection light end is the fifth surface 2031C, and the surface of the third lens close to the projection light end is the sixth surface 2032C.

The polarizer 301C and the polarization beam splitter 302C are sequentially stacked on the first surface 2021C, and the polarizer is located at a position farther away from the end of the projected light, thereby improving the packaging integration of the optomechanical module and shortening the size of the optomechanical module.

In this embodiment, the quarter wave plate 303C is attached to the planar fourth surface 2022C and the planar fifth surface 2031C, and a high flatness can still be obtained to improve the assembly yield of the quarter wave plate 303C, and ultimately improve the projection effect of the projection device.

In this embodiment, the polarizer 301C and the polarization beam splitter 302C are attached to the planar first surface 2021C, which can achieve a higher flatness, thereby improving the assembly yield of the polarizer 301C and the polarization beam splitter 302C, and ultimately improving the projection effect of the projection device.

The semi-reflective and semi-transparent membrane 304 is arranged on the outside of the sixth surface 2032C. In this embodiment, the reflection ratio of the semi-reflective and semi-transparent membrane 304 can be 40% and 60%, or 60% and 40%. Preferably, the reflection ratio is 50% and the transmission ratio is 50% (the overall lighting efficiency of the system is the highest), thereby improving the brightness utilization rate of the projected image.

FIG3D illustrates another implementation of a lens module 20D of the present application, in which the lens module 20D comprises a first lens 201D, a second lens 202D, a third lens 203D, and a fourth lens 204D in sequence from the end farthest from the projection light end to the end close to the projection light end, wherein the third lens 203D and the fourth lens 204D are connected together by a bonding layer 305D, thereby improving the system integration and shortening the size of the optical-mechanical module.

The end surface of the first lens 201D close to the projection light is a flat surface, and the end surface of the first lens 201D far from the projection light is a convex surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the second lens 202D close to the projection light end is convex, and the plane of the second lens 202D far from the projection light end is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the third lens 203D close to the projection light end is a flat surface, and the surface of the third lens 203D far from the projection light end is a concave surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The end surface of the fourth lens 204D close to the projection light is convex, and the end surface of the fourth lens 204D far from the projection light is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

For the sake of simple description, the surface of the first lens 201D away from the projection light end is the first surface 2011D, the surface of the first lens close to the projection light end is the second surface 2012D, the surface of the second lens away from the projection light end is the third surface 2021D, the surface of the second lens close to the projection light end is the fourth surface 2022D, the surface of the third lens away from the projection light end is the fifth surface 2031D, the surface of the third lens close to the projection light end is the sixth surface 2032D, the surface of the fourth lens away from the projection light end is the seventh surface 2041D, and the surface of the fourth lens close to the projection light end is the eighth surface 2042D.

The polarizer 301D and the polarization beam splitter 302D are sequentially stacked on the third surface 2021D, and the polarizer 301D is located at a position farther from the end of the projected light, thereby improving the packaging integration of the optical-mechanical module and shortening the size of the optical-mechanical module.

The third lens 203D and the fourth lens 204D in this embodiment are bonded together by a bonding layer 305D. In this embodiment, the quarter wave plate 303D is attached between the third lens 203D and the fourth lens 204D. The bonding layer 305D is arranged between the quarter wave plate 303D and the sixth surface 2032D. The bonding layer 305D is also arranged between the quarter wave plate 303D and the seventh surface 2041D, thereby improving the packaging integration of the optical-mechanical module and shortening the size of the optical-mechanical module.

The semi-reflective and semi-transparent membrane 304D is arranged on the outside of the eighth surface 2042D. In this embodiment, the reflection ratio of the semi-reflective and semi-transparent membrane 304D can be 40% and 60%, or 60% and 40%, preferably 50% and 50% (the overall lighting efficiency of the system is the highest), thereby improving the brightness utilization rate of the projected image.

Other surfaces in contact with air in the lens module 20D may be coated with an anti-reflection film (AR film), the reflectivity of which is less than 0.5%, thereby enhancing the utilization rate of the projected light.

In this embodiment, the refractive index of the first lens 201D is 1.5-1.6, preferably 1.54. The refractive index of the second lens 202D is 1.6-1.7, preferably 1.62. The refractive index of the third lens 203D is 1.7-1.8, preferably 1.76. The refractive index of the fourth lens 204D is 1.6-1.7, preferably 1.62. The optical design of the optical machine can be optimized and the size of the optical machine module can be shortened.

FIG. 3E shows another embodiment of a lens module 20E of the present invention. The lens module 20E has a first lens 201E, a second lens 202E, and a second lens 203E in sequence from the end farthest from the projection light to the end close to the projection light. The third lens 202E, the third lens 203E, and the fourth lens 204E are connected together by a bonding layer 305E, thereby improving the system integration and shortening the size of the optical-mechanical module.

The end surface of the first lens 201E close to the projection light is a flat surface, and the end surface of the first lens 201E far from the projection light is a convex surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the second lens 202E close to the projection light end is concave, and the plane of the second lens 202E far from the projection light end is convex, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The end surface of the third lens 203E close to the projection light is a flat surface, and the end surface of the third lens 20E far from the projection light is a convex surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The end surface of the fourth lens 204E close to the projection light is convex, and the end surface of the fourth lens 204E far from the projection light is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

For the sake of simple description, the surface of the first lens away from the projection light end is the first surface 2011E, the surface of the first lens close to the projection light end is the second surface 2012E, the surface of the second lens away from the projection light end is the third surface 2021E, the surface of the second lens close to the projection light end is the fourth surface 2022E, the surface of the third lens away from the projection light end is the fifth surface 2031E, the surface of the third lens close to the projection light end is the sixth surface 2032E, the surface of the fourth lens away from the projection light end is the seventh surface 2041E, and the surface of the fourth lens close to the projection light end is the eighth surface 2042E.

The polarizer 301E and the polarization beam splitter 302E are sequentially stacked on the third surface 2021E, and the polarizer 301E is located at a position farther away from the end of the projected light, thereby improving the packaging integration of the optical-mechanical module and shortening the size of the optical-mechanical module.

In this embodiment, the second lens 202E and the third lens 203E are bonded together by a bonding layer 305E. The bonding by the glue layer 305E enables the second lens 202E and the third lens 203E to obtain a relatively firm assembly relationship, thereby enhancing the reliability of the lens module 20E.

The third lens 203E and the fourth lens 204E in this embodiment are bonded together by a bonding layer 305E. In this embodiment, the quarter wave plate 303E is attached between the third lens 203E and the fourth lens 204E. The bonding layer 305E is disposed between the quarter wave plate 303E and the sixth lens 204E. The adhesive layer 305E is also disposed between the quarter wave plate 303E and the seventh surface 2041E, thereby improving the packaging integration of the optomechanical module and shortening the size of the optomechanical module.

The semi-reflective and semi-transparent membrane 304E is arranged on the outside of the eighth surface 2042E. In this embodiment, the reflection ratio of the semi-reflective and semi-transparent membrane 304E can be 40% and 60%, or 60% and 40%, preferably 50% and 50% (the overall lighting efficiency of the system is the highest), thereby improving the brightness utilization rate of the projected image.

Other surfaces in contact with air in the lens module 20E may be coated with an anti-reflection film (AR film), the reflectivity of which is less than 0.5%, thereby enhancing the utilization rate of the projected light.

In this embodiment, the refractive index of the first lens 201E is 1.5-1.6, preferably 1.54. The refractive index of the second lens 202E is 1.6-1.7, preferably 1.62. The refractive index of the third lens 203E is 1.7-1.8, preferably 1.76. The refractive index of the fourth lens 204E is 1.6-1.7, preferably 1.62. The optical design of the optical machine can be optimized and the size of the optical machine module can be shortened.

FIG3F illustrates another implementation of a lens module 20F of the present application, in which the lens module 20F comprises a first lens 201F, a second lens 202F, a third lens 203F, and a fourth lens 204F in sequence from the end farthest from the projection light end to the end close to the projection light end, wherein the second lens 202F and the third lens 203F are connected together by a bonding layer 305F, thereby improving the system integration and shortening the size of the optical-mechanical module.

The surface of the first lens 201F close to the projection light end is a flat surface, and the surface of the first lens 201F far from the projection light end is a convex surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The end surface of the second lens 202F close to the projection light is a flat surface, and the end surface of the second lens 202F away from the projection light is a convex surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The end surface of the third lens 203F close to the projection light is convex, and the end surface of the third lens 20F far from the projection light is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the fourth lens 204F close to the projection light end is a flat surface, and the surface of the fourth lens 204F far from the projection light end is a concave surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

For the sake of simplicity, the surface of the first lens 201F away from the projection light end is the first surface 2011F, and the surface of the first lens 201F close to the projection light end is the second surface 2012F. The surface of the lens 202F away from the projection light end is the third surface 2021F, the surface of the second lens 202F close to the projection light end is the fourth surface 2022F, the surface of the third lens 203F away from the projection light end is the fifth surface 2031F, the surface of the third lens 203F close to the projection light end is the sixth surface 2032F, the surface of the fourth lens 204F away from the projection light end is the seventh surface 2041F, and the surface of the fourth lens 204F close to the projection light end is the eighth surface 2042F.

The polarizer 301F and the polarization beam splitter 302F are sequentially stacked on the second surface 2012F, and the polarizer 301F is located at a position farther away from the end of the projected light, thereby improving the packaging integration of the optomechanical module and shortening the size of the optomechanical module.

In this embodiment, the second lens 202F and the third lens 203F are bonded together by a bonding layer 305F. The bonding by the glue layer 305F enables the second lens 202F and the third lens 203F to obtain a relatively firm assembly relationship, thereby enhancing the reliability of the lens module 20F.

In this embodiment, the quarter wave plate 303F is attached between the second lens 202F and the third lens 203F, the bonding layer 305F is arranged between the quarter wave plate 303F and the fourth surface 2022F, and the bonding layer 305F is also arranged between the quarter wave plate 303F and the fifth surface 2031F, thereby improving the packaging integration of the optomechanical module and shortening the size of the optomechanical module.

The semi-reflective and semi-transparent membrane 304F is arranged on the outside of the eighth surface 2042F. In this embodiment, the reflection ratio of the semi-reflective and semi-transparent membrane 304F can be 40% and 60%, or 60% and 40%, preferably 50% and 50% (the overall lighting efficiency of the system is the highest), thereby improving the brightness utilization rate of the projected image.

In this embodiment, all elements of the folding assembly are arranged on a flat optical surface. The aforementioned polarizer 301F, polarization beam splitter 302F, and quarter wave plate 303F are all planar film materials before assembly. Those skilled in the art should know that the planar film material attached to the curved surface may cause the film material to wrinkle and the assembly angle to deviate. In some low-cost solutions, the semi-reflective semi-transparent film 304F may also be attached to a planar film material. In this embodiment of the present application, when the semi-reflective semi-transparent film 304F is also a planar film material, by arranging the semi-reflective semi-transparent film 304F on a flat optical surface (the eighth surface 2042F), problems in assembly can be reduced and the assembly yield can be improved.

Other surfaces in contact with air in the lens module 20F may be coated with an anti-reflection film (AR film), the reflectivity of which is less than 0.5%, thereby enhancing the utilization rate of the projected light.

In this embodiment, the refractive index of the first lens 201F is 1.5-1.6, preferably 1.54. The refractive index of the second lens 202F is 1.6-1.7, preferably 1.62. The refractive index of the third lens 203F is 1.7-1.8, preferably 1.76. The refractive index of the fourth lens 204F is 1.6-1.7, preferably 1.62. It can optimize the optical design of the optomechanical machine and shorten the size of the optomechanical module.

In summary, in these embodiments, two lenses close to the projection light end are connected by gluing. The lens gluing solution can reduce the chromatic aberration of the projected image, improve the projection effect and enhance the immersiveness of augmented reality. In addition, in some solutions, by gluing two positive and negative lenses, the positive and negative lenses can achieve the negative lens to bring the display distance of the virtual image closer, and at the same time, the positive lens is used to offset the impact of the negative lens on the external environment. Under the premise of ensuring that the convergence conflict of the projection device meets the requirements, the lens gluing solution can improve the structural strength of the system, thereby improving the reliability of the projection device.

On the other hand, gluing two lenses close to the projection light end can also minimize reflection or refraction between the elements of the folded light path and the air interface, thereby reducing the aberration of the optical module and improving the projection quality.

On the other hand, in this embodiment, the quarter wave plate is separated so that the polarization state of the light in the ghost image light path does not change during the reflection process, and thus cannot be emitted at the position of the polarization beam splitter, thereby reducing the ghost image.

On the other hand, by separating the quarter-wave plate from other films and gluing it between two lenses, there is no refraction or reflection at the air interface, which can minimize surface reflection and reduce ghost images.

On the other hand, the quarter wave plate is attached to the surface of another lens so that the optical path of the reflected light on the surface between the quarter wave plate and the polarization beam splitter does not pass through the quarter wave plate, the polarization state of the light does not change, and the light cannot be emitted from the polarization beam splitter, thereby reducing ghost images.

In order to further explain the improvements of the present application, reference is made to FIGS. 4 and 5 , wherein FIG. 4 illustrates a prior art folded optical path module 30 . In FIG. 4 , the quarter wave plate 303 is arranged on the inner side of the optical surface. Those skilled in the art should know that although the transmittance of the lens is higher than 90%, reflection may still occur on the optical surface. For example, the optical surface in this embodiment is generally the second surface of the first lens in this embodiment, the first surface of the second lens and other surfaces of unexpected optical reflection (refer to FIG. B1 which illustrates an unexpected optical surface. It can be considered that at B1 of the accompanying figure, the projection light deviates after reflection and transmission on the lens surface, resulting in low brightness of the projection light and low light efficiency of the projection device). In complex cases, the polarization state of the light reflected on the surface between the quarter wave plate 303 and the semi-reflective and semi-transparent surface 304 is completely consistent with that when the light path is designed. Stray light can be emitted through the optical system to form a ghost image. For example, in FIG. 4 , about 0.25% of the projection light will eventually pass through the polarizer and be emitted on an unexpected optical surface such as the first surface of the second lens, which can easily cause a ghost image.

In summary, the present application proposes a projection device, including a light source module, which emits projection light with rotated circularly polarized light, a lens module, which is arranged on the projection light path of the light source module, and the lens module receives the projection light, and a folded light path component, wherein a portion of the folded light path component is arranged on a surface of the lens module away from the light source module, and a portion of the folded light path component is arranged on a surface of the lens module close to the light source module, the folded light path component forms a folded optical path between a surface away from the light source module and a surface close to the light source module, the portion of the folded light path component close to the light source module can transmit the rotated circularly polarized light, the folded light path component can convert the rotated circularly polarized light into linearly polarized light, the portion of the folded light path component away from the light source module can transmit linearly polarized light, and a portion of the folded light path component is arranged on a flat optical surface of the lens module. By partially arranging the folded light path component on the flat optical surface, the overall attachment accuracy of the folded light path component can be improved, thereby improving the optical performance of the folded light path component.

In addition, it can be concluded that the lens module in the present application includes a first lens, a second lens and a third lens, the first lens is arranged in a direction away from the light source module, the third lens is arranged in a direction close to the light source module, the second lens is arranged between the first lens and the third lens, the first lens has at least one flat optical surface, and the second lens and the third lens have at least one flat optical surface. By arranging the folded optical path assembly on the lens module, the assembly accuracy of the folded optical path assembly to the lens module can be high, and the overall optical performance of the lens module and the folded optical path assembly is good.

FIG5 illustrates a schematic diagram of the optical path of a folded optical path module 30 of the present application, wherein a quarter wave plate 303 is disposed in the bonding layer between two lenses (refer to the aforementioned embodiment), the quarter wave plate 303 is separated from other membranes (such as a polarizer 301, a polarization beam splitter 302, and a semi-reflective semi-transparent membrane 304), and the quarter wave plate 303 is attached to the lens surface in the other direction of the lens where the semi-reflective semi-transparent membrane 304 is located (refer to the aforementioned embodiment), so that the reflected light on the surface between the quarter wave plate 303 and the polarization beam splitter 302 does not pass through the quarter wave plate 303 to be emitted. Since the polarization state of the light will not change at this time, a small part of the light will not be emitted from the polarization beam splitter. Referring to B2 in the accompanying figure, an unexpected optical surface is illustrated. Although some light may be emitted from an unexpected optical surface, only about 0.125% of the light finally passes through the polarizer to be emitted, thereby reducing the ghost image phenomenon in the light finally projected.

In the prior art, the film materials need to be attached together by a film attaching device. In the prior art, the polarizer, polarization beam splitter and quarter wave plate need to be attached by a film attaching device. In some low-cost solutions, Semi-reflective and semi-transparent films also need film sticking equipment for attachment. In fact, the polarizer, polarization beam splitter, quarter wave plate and semi-reflective and semi-transparent film are more sensitive to assembly accuracy. For example, the polarization beam splitter and quarter wave plate need to be attached according to the phase angle relationship between the absorption axis and the transmission axis. If the assembly angle of the polarization beam splitter and quarter wave plate is tilted relative to the preset angle, it is very likely to cause deviations in light reflection, transmission or processing. Generally speaking, in the prior art, the polarization beam splitter and quarter wave plate need to ensure an error requirement of 2-3 degrees for the absorption axis angle, the polarizer needs to ensure an error requirement of 4-5 degrees, and the semi-reflective and semi-transparent film needs to ensure an error requirement of 3-4 degrees. Therefore, the assembly angle of the polarization beam splitter and quarter wave plate is as high as possible, which can better ensure the projection effect of the projection device.

In the prior art, the polarizer, the polarization splitter and the quarter wave plate are attached together. Errors are accumulated between each film layer, which may eventually cause an overall angle error of more than 3 degrees among the polarizer, the polarization splitter and the quarter wave plate, thereby affecting light processing and the projected image.

In addition, during the attachment process in the film attaching equipment, the large film material is positioned solely by mechanical positioning. As described in the previous process, there will be a problem of error accumulation after multiple film materials are superimposed, which will affect the phase deviation of the absorption axis or the transmission axis of the film material, and ultimately lead to error accumulation in the projected light. Many of the aforementioned embodiments have structural solutions to reduce assembly errors.

FIG6 shows a schematic diagram of the structure of a folded optical path component and a lens module of a projection device, wherein the lens module 20 includes a first lens 201 and a second lens 202 , wherein the first lens 201 is arranged in a direction away from the light source module 10 .

The folded optical path component 30 includes a semi-reflective semi-transparent film 304, a quarter wave plate 303, a polarization beam splitter 302, a polarizer 301 and a flat plate element 307. The polarizer 301, the polarization beam splitter 302, the quarter wave plate 303 and the semi-reflective semi-transparent film 304 are sequentially arranged from the direction away from the projected light to the direction close to the projected light.

In the same manner as described in the previous embodiment, in this embodiment, the polarizer 301 and the polarization beam splitter 302 are attached together as a whole. Since the polarizer 301 and the polarization beam splitter 302 are planar film materials, they remain planar after being attached together, so wrinkles will not occur after being attached. In this embodiment, the quarter-wave plate 303 is firstly attached planarly on a thin flat plate element 307 as an element to be assembled. In this embodiment, the semi-reflective semi-transparent film 304 is preferably an optical coating process. The semi-reflective semi-transparent film 304 is deposited on the surface of the second lens 202 close to the projected light by vapor phase deposition. Therefore, in this embodiment, the semi-reflective semi-transparent film 304 has no assembly tilt. Bevel angle problem.

In this embodiment, the first lens 201 and the second lens 202 are assembled together through active calibration. After assembly, there is an angle within 3° between the first lens 201 and the second lens 202, thereby improving the assembly angle error of the quarter wave plate 303 assembled to the flat element 307, which can achieve a better assembly effect.

On the other hand, the first lens 201 can be assembled with the quarter wave plate 303 and the flat plate element 307 through active calibration. There is an angle within 3° between the first lens 201 and the flat plate element 307, thereby improving the assembly angle error of the quarter wave plate 303 assembled to the flat plate element 307, which can achieve a better assembly effect.

On the other hand, the second lens 202 can be assembled with the quarter wave plate 303 and the flat plate element 307 through active calibration. There is an angle within 3° between the second lens 202 and the flat plate element 307, thereby improving the assembly angle error of the quarter wave plate 303 assembled to the flat plate element 307, which can achieve a better assembly effect.

In summary, in this embodiment, the folded optical path component 30 includes the semi-reflective and semi-transparent membrane 304, the quarter-wave plate 303, the polarization beam splitter 302, the polarizer 301 and the flat element 307, wherein the polarizer 301 and the polarization beam splitter 302 are attached together as a whole, and the quarter-wave plate 303 and the whole of the polarizer 301 and the polarization beam splitter 302 exist at an angle within 3°. Because the polarization beam splitter 302, the polarizer 301 and the quarter-wave plate 303 in the folded component 30 are sensitive to angles, it is generally required that the assembly angle can only deviate from the preset angle by 3°. Therefore, as long as the relative By correcting the relative angles of the polarization beam splitter 302, the polarizer 301 and the quarter wave plate 303, and making the relative positions of the three capable of having a good projection imaging together with the lens module 20, it can be explained that the relative positions (mainly the relative angles) of the polarization beam splitter 302, the polarizer 301 and the quarter wave plate 303 and the lens module 20 do not affect the projection imaging, and the overall imaging is good. The assembly is performed in an active calibration manner, which can achieve a better assembly effect of the folded optical path component 30, improve the assembly angle error between the folded optical path components 30, and make the assembly yield higher.

On the other hand, the quarter wave plate 303 is attached to the flat surface 307 . Since the quarter wave plate 303 is attached to a flat surface, the quarter wave plate 303 will not wrinkle.

To further illustrate the effect, this application provides two assembly methods:

Referring to FIG. 7 , an assembly method corresponding to the structure of FIG. 6 is illustrated, comprising the following steps:

Step S1, attaching a polarizer and a polarization beam splitter together to form a composite film;

Step S2, attaching a quarter wave plate to a flat plate element to form a flat quarter wave plate assembly;

Step S3, attaching the first lens and the composite film material together as a first component;

In the prior art, the film material will be deformed when attached to a curved surface. At the same time, the overall shape change caused by the material stress after deformation causes the optical performance to decline, thereby affecting the overall optical performance. In the prior art, the curved surface attachment yield is often not high. In step S3, attaching a quarter-wave plate to a flat element can improve the attachment yield.

In step S4, the first component, the second lens and the flat quarter-wave plate component are assembled together through an active calibration process;

Furthermore, in the step of attaching the first lens and the composite film material together as the first component in step S3, the composite film material is preferably attached to the flat surface of the first lens, as shown in FIG6, wherein the polarizer 301 and the polarization beam splitter 302 are attached to the first surface of the first lens, when the surface is a plane, the film attaching equipment of the prior art can make the film material attach to the flat surface with a better yield and a better flat attaching effect. It is worth noting that when the film attaching equipment of the prior art attaches the curved surface of the lens, the curved surface of the film material will be deformed when attached, and the overall shape changes caused by the material stress after deformation, so the curved surface attachment yield in the prior art is often not high.

Further, in step S4, in which the first component, the second lens and the flat quarter-wave plate component are assembled together through an active calibration process, the active calibration process controls the relative positions of the first component, the second lens and the flat quarter-wave plate component respectively, adjusts the rotation angle of the first component, the second lens or the flat quarter-wave plate component relative to the optical axis, and assembles after finding the best effect of the projected image. This method can improve efficiency and reduce stray light and ghost images.

Specifically, two of the three components, namely the first component, the second lens and the flat quarter-wave plate component, can be clamped and actively calibrated, and the remaining component can be fixed and the assembly adjustment basis can achieve better assembly of the first component, the second lens and the flat quarter-wave plate component.

It is worth mentioning that in this embodiment, it is preferred to fix the flat quarter wave plate assembly, clamp the first assembly and the second lens, and calibrate the first assembly and the second lens relative to the plane where the flat quarter wave plate assembly is located. Since the flat quarter wave plate assembly is roughly in the shape of a flat plate, the physical plane where the flat quarter wave plate assembly is located is easier to test and The solution of positioning and then calibrating with the plane where the flat quarter-wave plate component is located can improve the assembly efficiency.

In addition, the quarter wave plate in the flat quarter wave plate assembly is more sensitive to the assembly angle. In the prior art, the assembly angle limit of the quarter wave plate is approximately within 3 degrees, preferably within 1 degree. By pre-positioning the flat quarter wave plate assembly before assembling it, the first component and the second lens can be actively calibrated so that there is a certain tilt angle between the first component and the second lens to improve the assembly angle error of the quarter wave plate when assembled to the flat element, which can achieve a better assembly effect.

FIG8 shows a schematic diagram of the structure of a folded optical path component and a lens module of another projection device, wherein the lens module 20 includes a first lens 201 and a second lens 202 , and the first lens 201 is arranged in a direction away from the light source module 10 .

The folded optical path component 30 includes a semi-reflective and semi-transparent membrane 304, a quarter wave plate 303, a polarization beam splitter 302, a polarizer 301 and a flat plate element 307, which are arranged in sequence from the direction away from the projection light to the direction close to the projection light: the polarizer 301, the polarization beam splitter 302, the quarter wave plate 303 and the semi-reflective and semi-transparent membrane 304.

In this embodiment, the polarizer 301 and the polarization beam splitter 302 are attached together as a whole. Since the polarizer 301 and the polarization beam splitter 302 are planar film materials, they remain planar after being attached together, and thus wrinkles will not occur after attachment.

It is worth mentioning that in this embodiment, the quarter wave plate 303 is mounted on the second lens 202 through the flat plate element 307. Since the quarter wave plate 303 is firstly attached to a thin flat plate element 307 in a planar manner, the assembly yield of the quarter wave plate 303 can be improved. Then, the flat plate element 307 is assembled to the surface of the second lens 202 away from the projection light, and a transparent glue can be set between the flat plate element 307 and the second lens 202 for bonding.

In the present embodiment, the semi-reflective and semi-transparent film 304 is preferably formed by an optical coating process. The semi-reflective and semi-transparent film 304 is vapor deposited on the surface of the second lens 202 close to the projection light. Therefore, in the present embodiment, the semi-reflective and semi-transparent film 304 does not have an assembly tilt angle problem.

In this embodiment, the first lens 201 and the second lens 202 are assembled together through active calibration. After assembly, there is an angle within 3° between the first lens 201 and the second lens 202, which can improve the assembly angle error of the quarter wave plate 303 when assembled to the flat element 307, and can achieve a better assembly effect.

FIG9 shows a schematic diagram of the structure of a folded optical path component and a lens module of another projection device, wherein the lens module 20 includes a first lens 201 and a second lens 202 , wherein the first lens 201 is arranged in a direction away from the light source module 10 .

The folded optical path component 30 includes a semi-reflective semi-transparent film 304, a quarter wave plate 303, a polarization beam splitter 302, and a polarizer 301. The polarizer 301, the polarization beam splitter 302, the quarter wave plate 303, and the semi-reflective semi-transparent film 304 are sequentially arranged from the direction away from the projected light to the direction close to the projected light.

In this embodiment, the polarizer 301 and the polarization beam splitter 302 are attached together as a whole. Since the polarizer 301 and the polarization beam splitter 302 are planar film materials, they remain planar after being attached together, and thus wrinkles will not occur after attachment.

It is worth mentioning that, different from the embodiment of FIG. 8 , the quarter wave plate 303 is directly attached to the surface of the second lens 202 away from the projection light.

Although in the embodiment of FIG. 8 , the assembly effect can be improved by directly assembling the quarter wave plate 303 on the flat element, the total length of the optical system is increased due to the certain thickness of the flat element. The solution of FIG. 9 can relatively shorten the total optical length.

In this embodiment, the semi-reflective and semi-transparent film 304 is preferably produced by an optical coating process. The semi-reflective and semi-transparent film 304 is vapor deposited on the surface of the second lens 202 close to the projected light. Therefore, in this embodiment, the semi-reflective and semi-transparent film 304 does not have an assembly tilt angle problem.

In this embodiment, the assembly angle of the quarter wave plate 303 assembled to the second lens 202 is controlled within 2 degrees. In this embodiment, the first lens 201 and the second lens 202 are assembled together through active calibration. There is an angle of less than 3° between the assembled first lens 201 and the second lens 202, which is sufficient to improve the assembly angle error of the quarter wave plate 303 assembled to the second lens 202, thereby achieving a better assembly effect.

FIG. 10 schematically illustrates another assembly process of the present application. The assembly process of FIG. 10 corresponds to the structural schemes of FIG. 8 and FIG. 9 . The assembly process of FIG. 10 includes the following steps:

In step A1, the polarizer and the polarization beam splitter are attached together to form a composite film;

In step A2, a quarter wave plate is connected to the second lens as a second component;

In step A2, the quarter wave plate is connected to the second lens as the second component so that the components to be assembled can be prepared in advance.

In step A3, the first lens and the composite film material are attached together as a first component;

Furthermore, in the step of attaching the first lens and the composite film material together as the first assembly in step A3, the composite film material is preferably attached to the flat surface of the first lens, referring to As shown in FIG. 6 , the polarizer and the polarization beam splitter are attached to the first surface of the first lens. When the surface is a plane, the film attaching equipment of the prior art can make the film material attach to the flat surface with a better yield and a better flat attaching effect. It is worth noting that when the film attaching equipment of the prior art attaches the curved surface of the lens, the film material will be deformed when attached to the curved surface. At the same time, the overall shape changes caused by the material stress after deformation, and the film material is prone to wrinkling. Therefore, the yield of film attachment to the curved surface in the prior art is often not high.

In step A4, the first component and the second component are assembled together through an active calibration process;

In step A4, in which the first component and the second component are assembled together through an active calibration process, the active calibration process is performed by only controlling the first component or the second component, adjusting the position of the first component relative to the second component, adjusting the rotation angle between the first component or the second component relative to the optical axis, and finding the optimal position of the projected image to perform assembly. This method can improve efficiency while reducing stray light and ghost images. Different from the previous assembly process, in this embodiment, the folded optical path component and the lens module are first assembled into two components separately. It is only necessary to ensure that the attachment accuracy between the flat quarter-wave plate component and the second lens in the second component is within 2-3 degrees, so that the projected image can be optimized in the subsequent active calibration process of the first component and the second component.

In the above process, the quarter-wave plate is first attached to a flat element to form a flat quarter-wave plate assembly. It is necessary to reserve a flat element in the optical design. In the prior art, the glass of the flat element can be as thick as 0.2 mm, but this thickness will still increase the size of the optical machine module. In order to solve the problem of miniaturized assembly errors, another embodiment is illustrated with reference to FIG9. In this embodiment, the quarter-wave plate is attached to the surface of the second lens in the form of a curved film. Preferably, the quarter-wave plate is attached to the relatively flat surface of the second lens, that is, the quarter-wave plate is attached to the plane of the second lens with a larger curvature radius. Since the radius of curvature of the curved surface tends to infinity, the curved surface tends to a plane. By attaching the quarter-wave plate to the relatively flat surface of the second lens, the attachment yield of the quarter-wave plate can be improved, thereby reducing the defects of the quarter-wave plate and reducing the influence of stray light and ghosting of the projection device.

In this embodiment, an active calibration is performed between the first component made of the first lens and its polarizer and polarization beam splitter and the second component made of the quarter wave plate and the second lens (with the semi-reflective and semi-transparent film 304), the first lens and the second lens are controlled respectively, and the rotation angle of the first lens and the second lens relative to the optical axis is adjusted online, so that the relative position in six degrees of freedom can be found through active calibration to find the best clear position of the projected light, and the first component and the second component can be adjusted. The projection device is fixed after active calibration, so that the projection effect of the projection device is better. This solution can improve assembly efficiency, reduce stray light of projected imaging, and reduce ghost images of projected imaging.

FIG11 shows a schematic diagram of the optical path of a projection optical system with a folded optical path of the present application, wherein a cholesteric liquid crystal layer 306 is used in the projection optical system to reduce the generation of stray light ghost images. The projection device of this embodiment also includes a folded optical path component 30, wherein the folded optical path component 30 is sequentially provided with a cholesteric liquid crystal layer 306, a quarter wave plate 303, a semi-reflective and semi-transparent film 304 and a polarizer 301 in a direction from close to the projection light end to far from the projection light end, wherein the cholesteric liquid crystal layer 306 plays an optical effect of passing the projection light.

FIG. 11 shows a schematic diagram of another optical path of a folded optical path assembly of the present invention. The material of the cholesteric liquid crystal layer 306 (also called cholesteric multistable liquid crystal) in this embodiment can present three different molecular structure arrangements, namely:

Planar texture state (PlanarTexture), referred to as P state;

Focal conic texture (FC state for short); and

Homeotropic texture, also known as field-induced nematic phase, referred to as H state. When the applied voltage reaches the critical voltage Ec of the H state, the cholesteric liquid crystal is in the H state. The cholesteric liquid crystal in the H state is transparent and can directly transmit the incident light. When the applied voltage reaches the critical voltage Ec of the H state and then drops rapidly to zero, the cholesteric liquid crystal is driven to the planar state, i.e., the P state. The cholesteric liquid crystal in the P state reflects light of a fixed wavelength. When the applied voltage reaches the critical voltage Ec of the H state and then the step voltage drops to zero, the cholesteric liquid crystal is driven to the FC state. The cholesteric liquid crystal in the FC state presents a multi-domain state, and there is still a spiral structure in each domain. At this time, it will produce a strong scattering effect on the incident light. On the basis of the FC state, different driving voltages (less than Ec) are applied to the cholesteric liquid crystal to control the steering of multiple domains, so as to obtain different hazes (scattering rates) to meet the demands of reflected light of different intensities. In this embodiment, the intensity of projected light can be controlled to achieve the effects of projected light of different intensities.

Generally speaking, cholesteric liquid crystal is a wavelength-selective single-layer film with an adjustable spectral bandwidth of 2000nm, which can cover from ultraviolet to visible light and even to the near-infrared region. Cholesteric liquid crystal can have a single-layer structure, a double-layer structure, polarization, reflection, bandpass, band-stop filtering and other functions. Cholesteric liquid crystal has thermal stability and heat resistance up to 250°C. Cholesteric liquid crystal has high polarization efficiency and the transmittance of non-polarized light is close to the theoretical limit of 50%. Cholesteric liquid crystal can be composed of a polymer component, chiral nematic liquid crystal, also known as cholesteric liquid crystal (CLC), which can be obtained by combining nematic liquid crystal with chiral dopants. CLC molecules are arranged in a spiral to form a uniform spiral structure.

Cholesteric liquid crystal has a spin-chiral structure, and spin-selective broadband Bragg reflection is the most important characteristic of CLC chiral structure. When the rotation direction of the incident light is consistent with that of the cholesteric liquid crystal, the cholesteric liquid crystal will reflect the incident light in the wavelength range of no p-nep, where p is the pitch, and no and ne are the refractive indices of o-light and e-light. In other words, the light that the cholesteric liquid crystal chooses to transmit is related to the structural rotation direction of the cholesteric liquid crystal. If the arrangement of the cholesteric liquid crystal molecules is left-handed, then left-handed circularly polarized light is reflected and right-handed circularly polarized light is transmitted. If the cholesteric liquid crystal molecules are right-handed, then right-handed light is reflected and left-handed light is transmitted. According to the needs, the cholesteric liquid crystal in the FC state with a specific spiral direction can be designed to adapt to the folded optical path solution (pancake).

With the continuous development of virtual reality (VR) display technology in recent years, VR lenses of Pancake solution have gradually achieved mass production. Compared with traditional VR optical solutions, while maintaining a large field of view (FOV) and a large aperture (EPD), it has achieved a shorter system length and higher image display quality. However, as the core polarization devices in Pancake optical solutions: IQPS/IQPE/APF/PBS1000, etc., are subject to technical monopoly by certain companies, are expensive, and the polarization reflection performance is not ideal. The ghost image caused by light leakage affects the user experience. Moreover, these materials are all in the form of film materials. Due to the limitations of processing technology and the characteristics of the film materials themselves, they are mainly attached on a flat surface at this stage. However, when the surface of the film is flat, it cannot contribute to the correction of the optical system aberration, which limits the freedom of optical design and is not conducive to the development of Pancake solution towards the goal of shorter system size and higher imaging quality. Now manufacturers need a new projection optical system that realizes folded light path.

In summary, the present application proposes a projection device, including a light source module, which emits projection light with rotated circularly polarized light, a lens module, which is arranged on the projection light path of the light source module, and the lens module receives the projection light, and a folded light path component. When viewed along the projection light direction, there is a spin chiral structure in the structure of the folded light path component close to the light source module, and the rotation direction of the rotated circularly polarized light of the projection light is opposite to the rotation direction of the spin chiral structure, so that the folded light path component can selectively pass the circularly polarized light that rotates in a certain direction emitted by the light source module. This method can achieve the effect of directional passage of rotated circularly polarized light by using liquid crystal materials with spin chiral structures.

The present application proposes a folded optical path component, which is provided with a cholesteric liquid crystal layer, the cholesteric liquid crystal layer has a spin-chiral structure, the cholesteric liquid crystal layer is in a multi-domain state, and a spiral structure exists in each domain. The cholesteric liquid crystal layer is arranged in a direction close to the light source module, and the rotation direction of the projected light received by the cholesteric liquid crystal layer is opposite to the rotation direction of the spin-chiral structure. The cholesteric liquid crystal layer can transmit the projected light of the rotated circularly polarized light emitted by the light source module in a certain direction. Line, through the directional projection of light by the cholesteric liquid crystal layer, can make the folded light path component achieve the effect of directional rotation of circularly polarized light, and compared with the semi-reflective and semi-transparent film formed by the coating process, although the cholesteric liquid crystal material increases the size, the cost of the cholesteric liquid crystal material is lower, the manufacturing process is simpler, and a cheaper technical solution can be provided.

FIG. 12 shows a folded optical path assembly and a lens module of the present application. In this embodiment, the lens module 20 has a first lens 201, a second lens 202, and a third lens 203 from the end far from the projection light to the end close to the projection light, wherein the second lens 202 and the third lens 203 are connected together by gluing, thereby improving the system integration and shortening the size of the optical machine module.

The surface of the first lens 201 close to the projection light end is convex, and the surface of the first lens 201 away from the projection light end is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the second lens 202 close to the projection light end is convex, and the surface of the second lens 202 away from the projection light end is flat, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

The surface of the third lens 203 close to the projection light end is a plane, and the surface of the third lens 203 close to the projection light end is a concave surface, thereby reducing the aberration of the projection image, improving the quality of the projection image, and shortening the size of the optical machine module.

For the sake of simple description, the surface of the first lens 201 away from the projection light end is the first surface 2011, the surface of the first lens 201 close to the projection light end is the second surface 2012, the surface of the second lens away from the projection light end is the third surface 2021, the surface of the second lens close to the projection light end is the fourth surface 2022, the surface of the third lens away from the projection light end is the fifth surface 2031, and the surface of the second lens close to the projection light end is the sixth surface 2031.

The polarizer 301 is disposed on the first surface 2011, and the semi-reflective and semi-transparent film 304 is formed on the second surface 2012. In this embodiment, the semi-reflective and semi-transparent film 304 is formed by an optical coating process and is vapor-deposited on the second surface 2012. Therefore, in this embodiment, there is no problem of an assembly tilt angle for the semi-reflective and semi-transparent film 304. The polarizer 301 is a thin film material that can be attached to the flat first surface 2011 to improve the attachment yield, thereby improving the packaging integration of the projection device and shortening the size of the optical system.

The quarter wave plate 303 is attached to the third surface 2021 . The quarter wave plate 303 is a thin film material. By attaching it to a flat surface, the attachment yield can be improved.

It is worth mentioning that, in this embodiment, the second lens 202 and the third lens 203 are glued together. After that, a sandwich layer 308 with an opening (not shown in the figure) is formed, and the sandwich layer 308 is formed between the fourth surface 2022 and the fifth surface 2031. It is worth mentioning that, since the cholesteric liquid crystal in the FC state in this embodiment can be maintained without power, it is not required to power the cholesteric liquid crystal when completing the basic function of passing the projection light of the circularly polarized light rotated in a certain direction, and it is not necessary to set a power-on structure to change the voltage to change the pass rate of the projection light. Based on this, the embodiment proposed by the present application, in which the second lens and the third lens are glued to form a sandwich layer with an opening (not shown in the figure), and the cholesteric liquid crystal is injected into the sandwich layer through the opening (not shown in the figure) and sealed, so that the cholesteric liquid crystal can be maintained between the second lens 202 and the third lens 203, so that the cholesteric liquid crystal can always pass the projection light.

In another scheme, as shown in FIG. 13, a transparent conductive film 3062 is plated on the inner side of the interlayer 308, and an oriented film that can align the liquid crystal molecules in a certain direction is coated on the surface of the electrodes according to different display modes, and then the cholesteric liquid crystal is injected through the opening in the interlayer 308 to form a cholesteric liquid crystal layer 306, and finally sealed. Thus, the arrangement state of the liquid crystal molecules can be changed by applying an external electric field through the electrode 3061, which can cause the cholesteric liquid crystal layer 306 in the interlayer of the second lens 202 and the third lens 203 to change its optical properties, so that the light transmittance can be adjusted by changing the voltage of the electrode to change the brightness of the picture or part of the picture.

In this embodiment, cholesteric liquid crystal is used to replace the polarization splitter of the aforementioned folded light path solution (pancake solution), thereby avoiding the technical difficulty of curved film bonding of the polarization splitter. At the same time, the cholesteric liquid crystal can realize two reflective curved surfaces. The chiral structure of the cholesteric liquid crystal along the direction of the projected light is opposite to the chiral structure of the cholesteric liquid crystal away from the projected light. Specifically, the chiral structure of the cholesteric liquid crystal along the direction of the projected light is a left-handed structure, and when viewed from away from the projected light, the chiral structure of the cholesteric liquid crystal is a right-handed structure, thereby achieving a shorter total system length and higher imaging quality.

Still referring to the schematic diagram of the folded optical path shown in FIG. 11 , the basic optical path in this embodiment is as follows: the left-handed circularly polarized light emitted from the light source module 10 passes through the cholesteric liquid crystal layer 306 with a right-handed structure, and is normally transmitted, theoretically up to 100%, with no change in the rotation direction. After passing through the quarter-wave plate 302, the left-handed circularly polarized light changes to linearly polarized light, and the polarization direction is +45° with the fast axis of the wave plate (the fast axis is 45° clockwise). After being reflected by the semi-reflective and semi-transparent membrane 304, the energy loss is 50%, and the polarization direction of the reflected light is -45° with the fast axis of the wave plate (the fast axis is 45° counterclockwise), and changes to left-handed circular polarization. The rotation direction of the cholesteric liquid crystal is reversed due to the optical axis, and at this time it is a left-handed structure. Since the polarization direction of the incident light is consistent with the rotation direction of the liquid crystal, reflection occurs, and the incident left-handed circularly polarized light becomes right-handed circularly polarized light due to the reverse optical axis again. After passing through the quarter-wave plate 302, it becomes linearly polarized light, and the polarization direction is -45° with the fast axis of the quarter-wave plate 302 (relative to The light passes through the semi-reflective and semi-transparent film 304, and loses 50% of its energy again, and the energy becomes 25% of the original. At this time, the polarization state of the light is parallel to the transmission axis of the polarizer, and the light exits the system. Therefore, the folded optical path design can be realized, thereby reducing the total length (TTL) of the optical path and reducing the size of the whole device.

In addition, according to the experience of manufacturers in the industry, the polarization beam splitter of the folded optical path solution (pancake solution) is exclusively supplied by foreign companies (such as 3M) and is expensive. The use of cholesteric phase liquid crystal can bypass the polarization beam splitter to realize the pancake architecture. This embodiment can reduce costs and provide a new technical route for the pancake solution, and can provide other implementation solutions for Chinese companies.

In addition, cholesteric phase liquid crystal is basically a liquid, and there is no difficulty in curved surface film pasting. The problem that curved surface film cannot be mass-produced can be bypassed. It is only necessary to keep the cholesteric phase liquid crystal in the interlayer formed by gluing the second lens 202 and the third lens 203 to achieve the function of transmitting the projected light.

In addition, the use of cholesteric phase liquid crystal can reduce the reflection/refraction of unexpected interfaces. For the specific principle, please refer to the above content, which can reduce the intensity of ghost images.

FIG14 illustrates another projection optical system of folded optical path of the present application, wherein the projection optical system does not need the semi-reflective semi-transparent membrane 304 in the prior art. In this embodiment, the semi-reflective semi-transparent membrane 304 in the scheme can be replaced with IQPS/IQPE/PBS1000/WGF/APF and other membrane materials. In this embodiment, the semi-reflective semi-transparent membrane 304 is replaced with a polarizing beam splitter 302. The polarizing beam splitter 302 uses curved surface filming, film injection molding and other processes, and can be attached to the surface of the lens to replace the semi-reflective semi-transparent membrane 304. The polarization selection characteristics of membrane materials such as polarizing beam splitters are completely consistent with the polarization characteristics required by the design optical path, and the theoretical light efficiency can reach 100%.

In the prior art, the conventional projection folded light path solution (pancake solution) requires a semi-reflective and semi-transparent membrane 304 due to the need for light path folding. However, due to the existence of the semi-reflective and semi-transparent membrane 304, the system inherently has the defect of low light efficiency utilization, and the theoretical light efficiency is only 25%. It needs to be matched with a display screen with high brightness characteristics and used continuously in a high brightness state, which will cause high power consumption of the projection system, shorten the system battery life, and is not conducive to the miniaturization and lightweight of the system. In addition, due to the long-term use of the display screen with high brightness characteristics in a high brightness state, it will also cause the problem of heat accumulation in the augmented reality device. Augmented reality devices are generally AR glasses and the like, and excessive heat will also cause safety hazards.

Figure 14 illustrates another projection optical system with a folded light path of the present application, wherein the folded light path component 30 is provided with a cholesteric liquid crystal layer 306, a quarter wave plate 303, a polarization splitter 302 and a polarizer 301 in sequence from the projection light end to the direction away from the projection light end, wherein the cholesteric liquid crystal layer 306 plays an optical effect of passing the projection light.

The chiral structure of the spin of the cholesteric liquid crystal molecules is opposite to the rotation direction of the projected light of the light source module 10. In detail, if the projected light is left-handed, the cholesteric liquid crystal molecules are right-handed, so that the projected light can pass through. If the projected light is right-handed, the cholesteric liquid crystal molecules are left-handed, so that the projected light can pass through. According to this design, the cholesteric liquid crystal in the FC state of a specific spiral direction can pass most of the projected light, and in theory, 100% of the projected light can pass through.

The quarter wave plate 303 is a birefringent single crystal wave plate of a certain thickness. When light passes through the wave plate from normal incidence, the phase difference between ordinary light (o light) and extraordinary light (e light) is equal to π/2 or an odd multiple thereof. Such a chip is called a quarter wave plate or 1/4 wave plate. When linearly polarized light is incident vertically on the 1/4 wave plate, and the polarization of the light forms an angle θ with the optical axis plane of the wave plate (vertical to the natural cleavage plane), it becomes elliptically polarized light after emission. In particular, when θ=45°, the emitted light is circularly polarized light. The fast axis and slow axis of the wave plate are related to the type of crystal. Ve>Vo of the negative crystal, the optical axis direction of the wave plate is parallel to the wave plate plane, and the optical axis direction of the quarter wave plate made of the negative crystal is the fast axis direction. The fast axis direction of the positive crystal is perpendicular to the optical axis direction and is located in the plane of the glass slide. The polarization beam splitter 302 splits the incident light according to a certain percentage of reflected and transmitted light according to the corresponding polarization state of the light. The main function of the polarizer 301 is to convert the light passing through the polarizer into certain polarized light, and the polarizer selectively transmits certain polarized light.

The overall optical path can be explained as follows: the left-handed circularly polarized light emitted from the projection module passes through the cholesteric liquid crystal layer 306 with a right-handed structure normally, and the rotation direction does not change. Theoretically, it can reach 100% transmission through the cholesteric liquid crystal layer 306. The light emitted from the cholesteric liquid crystal layer 306 passes through the quarter-wave plate 303 again, and the left-handed circularly polarized light changes into linearly polarized light. The quarter-wave plate 303 only changes the polarization state without any loss of light efficiency. The polarization direction of the light emitted from the quarter-wave plate 303 is +45° (fast axis clockwise 45°) with the fast axis of the quarter-wave plate 303, and is parallel to the reflection axis of the polarization beam splitter 302. The incident polarized light is reflected, and the polarization direction of the reflected light is -45° with the fast axis of the quarter-wave plate 303 (fast axis counterclockwise 45°), and changes into left-handed circularly polarized light. The rotation direction of the cholesteric liquid crystal layer 306 is left-handed at this time because the optical axis is reversed. Since the polarization direction of the incident light is consistent with the rotation direction of the cholesteric liquid crystal layer 306, reflection occurs, and the incident left-handed circularly polarized light becomes right-handed circularly polarized light due to the reverse rotation of the optical axis, and becomes linearly polarized light after passing through the quarter-wave plate 303. The polarization direction of the light is -45° to the fast axis of the quarter-wave plate 303 (45° counterclockwise relative to the fast axis of the quarter-wave plate). At this time, the polarization state of the light is parallel to the transmission axis of the polarization beam splitter 302 and the polarizer 301. Theoretically, 100% of the light can be emitted from the optical system of the folded optical path component. The aforementioned solution only emits 25% of the light. In this application, the utilization rate of light can be greatly improved, and a display with a brightness of more than 800 nits (nit) is not required. The display screen can reduce the high brightness requirements of the display screen, reduce the heat generated by the display screen during operation, and reduce the safety hazards caused by high temperature.

The above describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only principles of the present invention. The present invention may be subject to various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications fall within the scope of the present invention to be protected. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims (23)

A projection device, characterized in that it comprises: A light source module, wherein the light source module emits a projection light with rotated circularly polarized light; A lens module, wherein the lens module is disposed on a projection light path of the light source module and receives the projection light; A folded optical path component, when viewed along the direction of the projected light, has a spin-like chiral structure in its structure close to the light source module, and the rotation direction of the rotated circularly polarized light of the projected light is opposite to that of the spin-like chiral structure. The projection device according to claim 1 is characterized in that the folded optical path component is provided with a cholesteric liquid crystal layer, the cholesteric liquid crystal layer has a spin-like chiral structure, the cholesteric liquid crystal layer is in a multi-domain state, and a spiral structure exists in each domain. The cholesteric liquid crystal layer is arranged in a direction close to the light source module, and the rotation direction of the projection light received by the cholesteric liquid crystal layer is opposite to the rotation direction of the spin-like chiral structure, so that the cholesteric liquid crystal layer can pass the projection light of the rotated circularly polarized light emitted by the light source module in a certain direction. The projection device according to claim 2 is characterized in that the lens module includes a first lens, a second lens and a third lens, the first lens is arranged in a direction away from the light source module, the third lens is arranged in a direction close to the light source module, the second lens is arranged between the first lens and the third lens, the first lens has at least one flat optical surface, and the second lens and the third lens have at least one flat optical surface. The projection device according to claim 3 is characterized in that the surface of the first lens away from the projection light end is the first surface, the surface of the first lens close to the projection light end is the second surface, the surface of the second lens away from the projection light end is the third surface, the surface of the second lens close to the projection light end is the fourth surface, the surface of the third lens away from the projection light end is the fifth surface, the surface of the second lens close to the projection light end is the sixth surface, the first surface is a plane, and the third surface is a plane. The projection device according to claim 4 is characterized in that the second lens and the third lens are glued to form a sandwich layer, the sandwich layer is formed between the fourth surface and the fifth surface, the cholesteric liquid crystal is injected into the sandwich layer, and the cholesteric liquid crystal is maintained between the second lens and the third lens. The projection device according to claim 5, characterized in that the inner side of the interlayer is plated with The transparent conductive film is arranged on the electrode surface of the inner wall of the interlayer to arrange the cholesteric liquid crystal molecules in a certain direction, so that the arrangement state of the cholesteric liquid crystal molecules is changed by applying an external electric field through the electrode. The projection device according to claim 5 or 6 is characterized in that, along the direction of the projected light, the folded optical path component includes a cholesteric liquid crystal layer, a quarter wave plate, a semi-reflective and semi-transparent membrane and a polarizer in sequence, wherein the polarizer is arranged on the first surface, the semi-reflective and semi-transparent membrane is arranged on the second surface, and the quarter wave plate is arranged on the third surface. The projection device according to claim 5 is characterized in that, along the direction of the projected light, the folded optical path component includes a cholesteric liquid crystal layer, a quarter wave plate, a polarization splitter and a polarizer in sequence, the polarizer is arranged on the first surface, the polarization splitter is arranged on the second surface, and the quarter wave plate is arranged on the third surface. The projection device according to claim 7, characterized in that the quarter wave plate reflects light to the cholesteric liquid crystal layer. The projection device according to claim 8 is characterized in that the cholesteric liquid crystal layer can present three different molecular structure arrangements, namely a planar texture state, a focal conic texture state, and a vertical texture state, and different driving voltages are applied to the cholesteric liquid crystal to control the steering of multiple domains and obtain different scattering rates to achieve transmitted light of different intensities. A projection device, characterized in that it comprises: A light source module, wherein the light source module emits a projection light with rotated circularly polarized light; A lens module, wherein the lens module is disposed on a projection light path of the light source module and receives the projection light; A folded optical path component, wherein a portion of the folded optical path component is disposed on a surface of the lens module away from the light source module, and a portion of the folded optical path component is disposed on a surface of the lens module close to the light source module, the folded optical path component forms a folded optical path between a surface away from the light source module and a surface close to the light source module, the portion of the folded optical path component close to the light source module is capable of transmitting rotated circularly polarized light, the folded optical path component is capable of converting rotated circularly polarized light into linearly polarized light, the portion of the folded optical path component away from the light source module is capable of transmitting linearly polarized light, and a portion of the folded optical path component is disposed on a flat optical surface of the lens module. The projection device according to claim 11, characterized in that the lens module comprises a first lens, a second lens and a third lens, the first lens is arranged in a direction away from the light source module, the third lens is arranged in a direction close to the light source module, and the second The lens is disposed between the first lens and the third lens, the first lens has at least one flat optical surface, and the second lens and the third lens have at least one flat optical surface. The projection device according to claim 12 is characterized in that the folded optical path component includes a semi-reflective and semi-transparent film, a quarter wave plate, a polarization beam splitter and a polarizer, and along the direction of the projection light, the semi-reflective and semi-transparent film, the quarter wave plate, the polarization beam splitter and the polarizer are sequentially arranged on the lens module, the polarization beam splitter and the polarizer are attached together to form a planar composite film material, the polarization beam splitter and the polarizer are arranged on a flat optical surface of the lens module, and the quarter wave plate is arranged on another flat optical surface of the lens module. The projection device according to claim 13, characterized in that the second lens and the third lens are connected together by a bonding layer, and the optical surface bonded between the second lens and the third lens is a flat optical surface. The projection device according to claim 14 is characterized in that the quarter wave plate is arranged in a bonding layer between the second lens and the third lens, and the semi-reflective and semi-transparent film is formed on the optical curved surface of the third lens by vapor deposition. The projection device according to claim 15 is characterized in that the lens module also includes a fourth lens, the fourth lens is arranged in a direction close to the light source module, the optical surface of the fourth lens close to the light source module is a plane, and the semi-reflective and semi-transparent film is attached to the optical surface of the fourth lens close to the light source module. The projection device according to claim 14 is characterized in that the surface of the first lens away from the projection light end is the first surface, the surface of the first lens close to the projection light end is the second surface, the surface of the second lens away from the projection light end is the third surface, the surface of the second lens close to the projection light end is the fourth surface, the surface of the third lens away from the projection light end is the fifth surface, the surface of the second lens close to the projection light end is the sixth surface, the first surface or the second surface is a plane, and the fourth surface and the fifth surface are planes. The projection device according to claim 17, characterized in that the first surface is a plane, the second surface is a convex surface, the third surface is a concave surface, and the sixth surface is a convex surface. The projection device according to claim 17, characterized in that the first surface is a plane, the second surface is a concave surface, the third surface is a convex surface, and the sixth surface is a convex surface. The projection device according to claim 17, characterized in that the first surface is a plane, the second surface is a convex surface, the third surface is a convex surface, and the sixth surface is a convex surface. The projection device according to claim 14 is characterized in that the lens module also includes a fourth lens, the surface of the first lens away from the projection light end is a first surface, the surface of the first lens close to the projection light end is a second surface, the surface of the second lens away from the projection light end is a third surface, the surface of the second lens close to the projection light end is a fourth surface, the surface of the third lens away from the projection light end is a fifth surface, the surface of the second lens close to the projection light end is a sixth surface, the surface of the fourth lens away from the projection light end is a seventh surface, and the surface of the fourth lens close to the projection light end is an eighth surface, wherein the first surface is a convex surface, the second surface is a plane, the third surface is a plane, the fourth surface is a convex surface, the fifth surface is a concave surface, the sixth surface is a plane, the seventh surface is a plane, and the eighth surface is a convex surface. The projection device according to claim 14 is characterized in that the lens module also includes a fourth lens, the surface of the first lens away from the projection light end is a first surface, the surface of the first lens close to the projection light end is a second surface, the surface of the second lens away from the projection light end is a third surface, the surface of the second lens close to the projection light end is a fourth surface, the surface of the third lens away from the projection light end is a fifth surface, the surface of the second lens close to the projection light end is a sixth surface, the surface of the fourth lens away from the projection light end is a seventh surface, and the surface of the fourth lens close to the projection light end is an eighth surface, wherein the first surface is a convex surface, the second surface is a plane, the third surface is a convex surface, the fourth surface is a concave surface, the fifth surface is a convex surface, the sixth surface is a plane, the seventh surface is a plane, and the eighth surface is a convex surface. The projection device according to claim 14 is characterized in that the lens module also includes a fourth lens, the surface of the first lens away from the projection light end is a first surface, the surface of the first lens close to the projection light end is a second surface, the surface of the second lens away from the projection light end is a third surface, the surface of the second lens close to the projection light end is a fourth surface, the surface of the third lens away from the projection light end is a fifth surface, the surface of the second lens close to the projection light end is a sixth surface, the surface of the fourth lens away from the projection light end is a seventh surface, and the surface of the fourth lens close to the projection light end is an eighth surface, wherein the first surface is a convex surface, the second surface is a plane, the third surface is a convex surface, the fourth surface is a plane, the fifth surface is a plane, the sixth surface is a convex surface, the seventh surface is a concave surface, and the eighth surface is a plane.