CN118276314A

CN118276314A - Projection module

Info

Publication number: CN118276314A
Application number: CN202211658283.XA
Authority: CN
Inventors: 李泓; 徐昊天; 刘俊杰; 李潍
Original assignee: Ningbo Sunny Opotech Co Ltd
Current assignee: Ningbo Sunny Opotech Co Ltd
Priority date: 2022-12-22
Filing date: 2022-12-22
Publication date: 2024-07-02
Also published as: WO2024131877A1

Abstract

The application provides a projection module, which comprises a projection unit, an adjusting unit and an optical unit, wherein the optical unit comprises at least one optical lens and a polarizing element, and the polarizing element is arranged at the rear side of the projection unit. Wherein the polarizing element is arranged between the optical lenses, the light signal emitted by the projection unit is emitted through the optical lenses through multiple refraction and/or reflection actions of the polarizing element, wherein, the adjusting unit can correspondingly adjust the distance between the optical lenses, and the adjusting unit is matched with the polarizing element, so that the display with large exit pupil diameter, short focus and high optical performance is realized by prolonging the light path passing through the optical lenses.

Description

Projection module

Technical Field

The invention relates to the field of virtual reality projection modules, in particular to an augmented reality projection module.

Background

A virtual head mounted display is a visual optical system that projects images or data information of a micro display to the pupil of a human eye. According to different projection modes, the head-mounted display is divided into an eyepiece-type head-mounted display and a projection-type head-mounted display, wherein the eyepiece-type head-mounted display is used for placing an image within the focal length of an optical system to generate an enlarged virtual image, and the system exit pupil is formed at the pupil of a human eye through refraction or reflection of a subsequent lens group, and the position of the exit pupil is overlapped with the position of an aperture diaphragm of the optical system. The projection type head-mounted display is used for amplifying an image on the ultra-micro display screen through a group of optical systems (mainly precision optical lenses), and projecting the image on retina so as to present a large-screen image in eyes of a viewer.

Currently, both eyepiece and projection head-mounted displays require the user to fix the device in position to the human eye to better receive the light signal emitted by the projection unit. The optical lens arranged in the existing head-mounted display can effectively improve the imaging effect of the head-mounted display, but has large volume and weight, and the optical lens is arranged on the head-mounted display, so that discomfort of a user can be caused by long-time wearing of the optical lens, and the experience effect of the user is further affected.

Miniaturization of head-mounted displays is a mainstream trend of development, and the projection module is also required to be miniaturized as an important component element of the head-mounted display.

Disclosure of Invention

The camera module is used as an important component of the head-mounted display and comprises a projection unit, a lens unit and an adjusting unit, wherein a light ray signal emitted by the projection unit is received by human eyes through the action of the lens unit, and the adjusting unit can adjust the gap between each lens sheet in the lens unit so as to adjust the imaging definition according to actual conditions.

Furthermore, in order to enable the light signal emitted by the projection module to be imaged clearly through the lens unit, a certain adjustment gap is required between the lens sheets of the lens unit, and meanwhile, a certain gap is also required between the lens sheets to meet the imaging requirement. The camera module is provided with a lens unit, and the lens unit is arranged on the head-mounted display.

One embodiment of the application provides a projection module, which can effectively improve the imaging quality of the projection module by fixing a first optical lens and a second optical lens and adjusting a gap between the second optical lens and a third optical lens.

One embodiment of the application provides a projection module, wherein the polarization element is directly integrated on an optical lens in a film plating mode, so that the imaging of the optical system is met, and meanwhile, the focal length of the optical system can be effectively shortened.

One embodiment of the application provides a projection module, wherein the 1/4 wave plate is integrated on the second optical lens, and the mounting position of the 1/4 wave plate is adjusted by calibrating the position between the first optical lens and the second optical lens, so that the mounting precision of the 1/4 wave plate can be effectively improved.

One embodiment of the present application provides a projection module, in which two surfaces of a first optical lens and a second optical lens, which are opposite to each other, are configured to be planar, so that a coating can be conveniently disposed between the first optical lens and the second optical lens, thereby extending a propagation path of a projection light.

One embodiment of the present application provides a projection module, in which a cover is fixed at a position where a rotating ring is connected to a lens barrel, so that the rotating ring is prevented from excessively moving relative to the lens barrel, and at the same time, external dust is prevented from entering a gap between the lens barrel and the rotating ring.

One embodiment of the application provides a projection module, wherein a through hole with a certain inclination angle with the bottom surface of the lens barrel is arranged on the lens barrel, the third optical lens is connected with a rotating ring through the intermediary of a fastener, and when the rotating ring moves along the direction of an optical axis, the third optical lens can be driven to move, so that the position of the third optical lens can be adjusted.

One embodiment of the application provides a projection module, wherein a vertical groove structure is arranged in a rotating ring, through a preset through hole in a lens barrel, the vertical groove and a third optical lens generate corresponding linkage action, the position of the third optical lens can be realized by adjusting the outer rotating ring, and the structure of an adjusting unit is simplified.

One of the embodiments of the present application provides a projection module, in which an optical lens is fixed on a stepped structure by arranging a corresponding stepped structure inside a lens barrel, and gaps between lenses are reserved by the height of the steps, so that the assembly process can be effectively simplified.

One embodiment of the application provides a projection module, wherein a semi-reflective and semi-transparent film in a polarizing element is arranged on the surface of a third optical lens, so that light projected from a projection unit passes through the third optical lens first, and the utilization rate of the projected light can be effectively improved.

One embodiment of the present application provides a projection module, in which the second optical lens is made of a material with a low refractive index, so that the projection light passing through the second optical lens is reflected to the third optical lens again, and the propagation path of the projection light is prolonged.

The application provides a projection module, wherein a polarizing element is introduced into an optical lens structure, so that imaging of an optical system is realized, the focal length of the whole optical system is shortened, and the miniaturization of the whole structure of the projection module is realized.

In order to achieve the above purpose, the application adopts the following technical scheme:

A projection module comprises a projection unit, an adjusting unit and an optical unit, wherein the projection light emitted by the projection unit can be emitted through the optical unit, and the optical unit is arranged inside the adjusting unit;

The optical unit further comprises at least one optical lens and at least one polarizing element, wherein the polarizing element is mainly used for changing the propagation path of the projection light, and the polarizing element is arranged between the optical lenses;

The number of the optical lenses is a plurality, the optical lenses comprise a first optical lens, a second optical lens and a third optical lens, the first optical lens and the second optical lens form a fixed lens group, the fixed lens group is fixedly arranged on the adjusting unit, the third optical lens is movably arranged on the adjusting unit and used for focusing, the surface of the first optical lens facing the projection unit is planar, and part of the polarizing element is arranged between the first optical lens and the second optical lens; the method is characterized in that:

the adjusting unit is provided with an adjusting channel, the adjusting channel corresponds to the fixed lens group, and the position of the optical lens in the at least one fixed lens group can be corrected through the adjusting channel.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing embodiments of the present invention in more detail with reference to the attached drawings. The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, and not constitute a limitation to the invention. In the drawings, like reference numerals generally refer to like parts or steps.

FIG. 1 is a schematic diagram of the overall structure of a projection module according to the present application;

FIG. 2 is a schematic diagram of a projection unit of a projection module according to the present application;

FIG. 3 is a schematic cross-sectional view of a projection module according to the present application;

FIG. 4 is an exploded view of the projection module of the present application;

FIG. 5 is a schematic diagram of an optical unit in a projection module according to the present application;

FIG. 6 is a schematic diagram of another embodiment of an optical unit of the projection module according to the present application;

FIG. 7 is a schematic view of a portion of a projection module with a tuning channel according to the present application;

FIG. 8 is a schematic diagram of an adjusting unit of the projection module according to the present application;

fig. 9 is a schematic view of a lens barrel with a through hole according to the present application;

Fig. 10 is a side cross-sectional view of an adjustment unit provided with an optical lens in the present application.

Detailed Description

The present invention will be further described with reference to the following specific embodiments, and it should be noted that, on the premise of no conflict, new embodiments may be formed by any combination of the embodiments or technical features described below.

In the description of the present invention, it should be noted that, for the azimuth words such as terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the azimuth and positional relationships are based on the azimuth or positional relationships shown in the drawings, it is merely for convenience of describing the present invention and simplifying the description, and it is not to be construed as limiting the specific scope of protection of the present invention that the device or element referred to must have a specific azimuth configuration and operation.

It should be noted that the terms "first," "second," and the like in the description and in the claims are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.

The terms "comprises" and "comprising," along with any variations thereof, in the description and claims, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; either directly or indirectly through intermediaries, or both elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

As shown in fig. 1 to 9, the present application provides a projection module, which includes an adjusting unit 10, an optical unit 20 and a projection unit 30, wherein the projection unit 30 is disposed at the rear side of the optical unit 20, and an optical signal projected by the projection unit 30 passes through the optical unit 20 to form an image acceptable to human eyes. The optical unit 20 is disposed in the adjusting unit 10, and the optical unit 20 includes at least one optical lens 211 and a polarizing element 212, wherein the polarizing element 212 may be integrated on the optical lens 211 or may be separately disposed apart from the optical lens 211. The adjusting unit 10 can adjust the gap between the lenses of the optical lens 211 to extend the light path of the light beam projected by the projection unit 30, thereby realizing a larger exit pupil straight-through, and obtaining clearer imaging with a smaller focal length, thereby reducing the height of the projection module. Further, the polarizer 212 can be implemented as various types of polarizers, and can be correspondingly matched with the light signal projected by the projection unit 30, so that the projected light signal passes through the effect of the projector 212, and the focal length of the overall projection module is reduced while the light propagation path is prolonged, and the height of the projection module is reduced.

As shown in fig. 2 to 3, in a specific embodiment, the projection unit 30 provided in the present application includes a screen bracket 311 and a display screen 312, where the screen bracket 311 forms a corresponding supporting function for the display screen 312, and further, the screen bracket 311 has a first light-passing hole 231 and a screen supporting seat 322. The first light-passing hole 321 is disposed at the middle position of the screen support 322, wherein the shape of the projection support 322 is consistent with the shape of the display screen 312, and the display screen 312 can be directly disposed inside the screen support 322 to reduce the height of the projection unit 30 formed by combining the screen support 311 and the display screen 312.

In a specific embodiment, the display screen 312 provided in the present application may be a combined package structure, further, the display screen 312 includes a light emitting chip 323, a substrate 324 and a packaging layer 325, the light emitting chip 323 is disposed on the substrate 324 in an array, in this embodiment, the light emitting chip 323 is preferably a mini LED chip or MicroLED chip, and the LED is used as a light source to save energy. The encapsulation layer 325 is used to encapsulate the light emitting chip 323 on the substrate 324, and in some embodiments, the encapsulation layer 325 is formed by applying an encapsulation compound on the surface of the Mini LED lamp panel and drying, and the encapsulation layer 325 may include a transparent photo-curing or thermosetting resin, and the encapsulation layer 325 may also be implemented as a transparent protective compound.

Further, the display screen 312 may further include a lens array, which may include a plurality of superlenses disposed on a surface of the encapsulation layer 325 remote from the substrate 324, and each superlens may include a plurality of columnar microstructures. In this embodiment, each superlens unit corresponds to an individual light-emitting chip 323, so as to implement diffraction and amplification of the angle of light emitted by the light-emitting chip 323. The superlens array is implemented as columnar microstructures, wherein the columnar microstructures are perpendicular to the upper surface of the encapsulation layer 325, each columnar microstructure may be cylindrical or prismatic, i.e. the orthographic projection of each columnar microstructure on the first surface may have a shape of a circle, rectangle, polygon, or the like. Furthermore, the lens array is implemented as a super lens, which can realize the emission of parallel light, and can also reduce the light emission angle, and the super lens array is adopted to perform light diffraction, so as to homogenize the brightness of the projected light, thereby improving the light utilization rate of the light emitting chip 323.

As shown in fig. 3 and 5, the projection module of the present application further includes an optical unit 20, where the optical unit 20 is disposed at the front end of the projection unit 30 and is mainly used for receiving the light emitted by the projection unit 30, and the light emitted by the projection unit 30 can be received by human eyes under the action of the optical unit 20, so as to obtain the light information emitted by the projection unit 30. The optical unit 20 includes at least one optical lens 211 and a projection element 212, wherein the optical lens 211 is mainly used for transmitting the light emitted by the projection unit 30, and the projection unit 212 can change the propagation path of the light emitted by the projection unit 30 or lengthen and/or shorten the propagation path of the light so as to shorten the imaging distance of the optical system, thereby reducing the length of the optical system and realizing miniaturization of the overall structure of the projection module.

As shown in fig. 5, in a specific embodiment, the optical lens includes a first optical lens 221, a second optical lens 222 and a third optical lens 223, and a gap between the first optical lens 221 and the second optical lens 222 can be adjusted, and a gap between the second optical lens 222 and the third optical lens 223 can be correspondingly adjusted. The first optical lens 221 has a first surface 2311 and a second surface 2312, wherein a side close to the projection unit 30 is a second surface 2313, a side far from the projection unit 30 is a first surface 2311, and the first surface 2311 and the second surface 2312 are integrated on the same lens. Further, the surface shapes of the first surface 2311 and the second surface 2312 can be selected according to practical needs. Specifically, the first surface 2311 and the second surface 2312 of the first optical lens 221 can be one of spherical, aspherical, planar or other irregular surface types, and the specific surface type can be selected according to the requirements of the imaging optical system.

Further, the optical lens 211 of the present application further includes a second optical lens 222 and a third optical lens 223, wherein the second optical lens 222 has a third surface 2313 and a fourth surface 2314, and a side close to the projection unit 30 is the fourth surface 2314, and a side far from the projection unit 30 is the third surface 2313. The third optical lens 223 has a fifth surface 2315 and a sixth surface 2316, wherein the side close to the projection unit 30 is the fifth surface 2315, and the side far from the projection unit 30 is the sixth surface 2316, and the surface types of the third surface 2312 and the fourth surface 2314 of the second optical lens 222, the fifth surface 2315 and the sixth surface 2316 of the third optical lens 223 can be correspondingly selected according to the imaging requirements of the actual optical system.

In one embodiment, as shown in fig. 5, the polarizing element 212 of the optical unit 20 is integrated on the optical lens 21, wherein the polarizing element 212 comprises a semi-reflective and semi-transmissive film 224, a 1/4 wave plate 225, a polarizing beam splitter 226 and a polarizer 227. In this embodiment, the layers of the semi-reflective and semi-permeable membrane are generally laminated with tio2, nbox and sio2, and because tio2, nbox and sio2 are used, the reflectivity of the semi-reflective and semi-permeable membrane 224 in this embodiment is not less than 25% and not more than 75% for visible light. Specifically, the semi-reflective and semi-permeable membrane 224 can be disposed on the sixth surface 2316 of the third optical lens 223, and in order to ensure the adhesion between the third optical lens 223 and the semi-reflective and semi-permeable membrane 224, the semi-reflective and semi-permeable membrane 224 can be directly plated on the sixth surface 2316 of the third optical lens 223 by a plating process.

Further, the 1/4 wave plate 225, the polarizing beam splitter 226 and the polarizer are disposed between the first optical lens 221 and the second optical lens 222, and in order to further reduce the total length of the optical system, the 1/4 wave plate may be first disposed on the second surface 2312 of the first optical lens 221 by using a layered coating method, so that the 1/4 wave plate 225 is located between the second surface 2312 and the third surface 2313. The 1/4 wave plate 225 is a birefringent single crystal plate of a thickness such that when light is transmitted through the plate from normal incidence, the phase difference between ordinary (o) and extraordinary (e) light is equal to pi/2 or an odd multiple thereof, such a wafer being referred to as a quarter wave plate or 1/4 wave plate. When the linearly polarized light vertically enters the 1/4 wave plate, and the light polarization and the optical axis surface (vertical natural splitting surface) of the wave plate form an angle theta, the light is emergent to form elliptical polarized light. Particularly when θ=45°, the outgoing light is circularly polarized light. The fast and slow axes of the waveplate are related to the type of crystal. The 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 positive crystal fast axis direction is perpendicular to the optical axis direction and is positioned in the wave plate plane.

The polarization beam splitter 226 splits incident light according to a certain percentage of reflected and transmitted light according to the polarization state of the corresponding light, and the polarizer plays a main role of converting light passing through the polarizer into certain polarized light, and the polarizer selectively transmits the certain polarized light. The polarization beam splitter 226 is disposed on the surface of the 1/4 wave plate, fixed on the first surface 2311 of the first optical lens 221, and the polarizer 227 is disposed on the surface of the polarization beam splitter 226, and fixed on the first surface 2311 of the first optical lens 221 together with the polarization beam splitter 226. The polarizing element 212 may form a light refracting layer, which is fixed on the first surface 2311 of the first optical lens 221, and the first surface 2311 adjacent to the first optical lens 221 is sequentially a 1/4 wave plate 225, a polarizing beam splitter 226 and a polarizer 227. In another possible embodiment, the light refracting layer may be fixedly disposed on the third surface 2313 of the second optical lens 222, and in order to make the coating between the second optical lens 222 and the light refracting layer more stable, the third surface 2313 of the second optical lens 222 may be disposed in a planar shape.

In a specific imaging process, the light projected by the projection unit 30 is left-handed polarized light, and after passing through the semi-reflective and semi-transparent film 224, 50% of the left-handed polarized light passes through the 1/4 wave plate 225 and is processed into parallel polarized light (parallel refers to parallel to the optical axis direction) having +45° with respect to the fast axis of the 1/4 wave plate. The polarization direction is parallel to the reflection axis of the polarization beam splitter 226, the reflected light reflected by the polarization beam splitter 226 forms-45 ° with the fast axis of the 1/4 wave plate 225, the parallel polarized light is converted into left-handed polarized light, and 50% of the projected light is reflected (the energy of the projected light becomes the first 25%) after the left-handed polarized light reaches the semi-reflective and semi-transmissive film 224 again. Because the direction of the optical axis is opposite, the projected light is reflected again into right-handed polarized light, the right-handed polarized light is converted into linear polarized light through the 1/4 wave plate, the included angle between the direction of the light polarization and the fast axis of the wave plate is-45 ° (the fast axis is anticlockwise 45 °), and at this time, the direction of the light polarization is consistent with the transmission direction of the polarizing beam splitter 226 and the transmission direction of the polarizer 227. In this solution, the gap between the polarizing elements is increased, thereby increasing the optical path through which the light passes. The optical unit 20 in the present application uses the polarizing element 212 to extend the light path of the light beam projected by the projection unit 30, so as to shorten the actual size of the optical unit 20 and reduce the height of the projection module while satisfying the imaging requirements of the optical system.

Referring to fig. 5 and 6, fig. 6 shows another possible embodiment of the optical unit 10 according to the present application, specifically, the optical unit 10 includes a first optical lens 221, a second optical lens 222, and a third optical lens 223, where the optical unit 10 further includes a polarizing element 212. The polarizing element 212 includes a plurality of polarizing plates, which are sequentially arranged from far to near with respect to the projection unit 30: a polarizer 227, a polarizing beam splitter 226, a 1/4 wave plate 225 and a semi-reflective and semi-transmissive film 224, wherein the semi-reflective and semi-transmissive film 224 may be integrated on the third optical lens 223, and in particular, the semi-reflective and semi-transmissive film 224 is disposed on a side of the third optical lens 223 close to the projection unit 30, i.e., the semi-reflective and semi-transmissive film 224 is disposed on a sixth surface 2316 of the third optical lens 223. Further, to extend the optical path of the projected light, a part of the polarizing element 212 may be disposed between the first optical lens 221 and the second optical lens 222. Further, a polarizer 227, a polarizing beam splitter 226 and a 1/4 wave plate 225 are disposed between the first optical lens 221 and the second optical lens 222, and the polarizing elements 212 are required to be disposed in a certain order to facilitate the transmission of the projected light. Specifically, the second surface 2312 of the first optical lens 221 is provided with the polarizer 227, the polarizing beam splitter 226 is disposed on the surface of the polarizer 227, and the 1/4 wave plate may be disposed between the first optical lens 221 and the second optical lens 222 alone or may be integrated on the third surface 2313 of the second optical lens 222. In order to enhance the stability of the connection between the 1/4 wave plate 225 and the second optical lens 222, the 1/4 wave plate may be directly fixed on the surface of the second optical lens 222 by a plating method. Further, in the actual manufacturing process, the polarizer 227, the polarizing beam splitter 226 and the 1/4 wave plate 225 are sensitive to assembly accuracy, for example, the polarizing beam splitter 226 and the 1/4 wave plate 225 need to be attached according to the phase angle relationship between the absorption axis and the transmission axis. If the polarizing beam splitter 226 and the 1/4 wave plate 225 are inclined with respect to a predetermined angle, there is a high possibility that deviation of light reflection or transmission or processing occurs, and generally, in the prior art, the polarizing beam splitter 226 and the 1/4 wave plate 225 have an error requirement within 2-3 ° with respect to an absorption axis angle. in the prior art, the three films of the polarizer 227, the polarizing beam splitter 226 and the 1/4 wave plate 225 are required to be attached together, and errors are accumulated between each film layer, so that the overall angle errors of the polarizer 227, the polarizing beam splitter 226 and the 1/4 wave plate 225 may be larger than 3 degrees, thereby affecting light processing and projected images. In addition, in the process of attaching in the film attaching equipment, the large film material is positioned by only mechanical positioning, as in the process described above, the problem of error accumulation can occur after the superposition of a plurality of film materials, the phase deviation of the absorption axis or the transmission axis of the film material can be affected, and finally, the error accumulation of the projection light is caused.

In order to solve the above problems, in the present application, the surface of the first optical lens 221 close to the projection unit 30 is configured as a plane, and the surface of the first optical lens far from the projection unit 30 is configured as a convex surface, so as to reduce the aberration of the projection screen, improve the image quality of the projection screen, and shorten the size of the optical machine module. Further, in this embodiment, the polarizer 227 and the polarizing beam splitter 226 are attached together as a whole, except that the 1/4 wave plate 225 is first attached to a thin plate in a planar manner and assembled as a component to be assembled. In this embodiment, the semi-reflective and semi-transmissive film 224 is formed by an optical coating process, and is deposited on the surface of the third optical lens 223 close to the projected light by vapor deposition. Therefore, in the present embodiment, the semi-reflective and semi-permeable membrane 224 does not have an assembly inclination angle problem. The first optical lens 221 and the second optical lens 222 are actively aligned, and an included angle within 3 ° exists between the first optical lens 221 and the second optical lens 222, so as to improve an assembly angle error of the 1/4 wave plate 225 assembled on the flat plate, and enable an assembly effect to be better. Or the first optical lens 221, the 1/4 wave plate 225 and the flat plate are assembled together through active calibration, and an included angle of less than 3 degrees exists between the first optical lens 221 and the flat plate, so that an assembly angle error of the 1/4 wave plate 225 assembled on the flat plate is improved, and an assembly effect can be better. Or the second optical lens 222, the 1/4 wave plate 225 and the flat plate are actively calibrated and assembled together, and an included angle of less than 3 degrees exists between the second optical lens 222 and the flat plate, so that the assembly angle error of the quarter wave plate assembled on the flat plate is improved, and the assembly effect is better.

In a preferred embodiment, in order to reduce the total optical length of the optical unit 20 and achieve miniaturization of the overall projection module structure, the 1/4 wave plate 225 is directly integrated on the third surface 2313 of the second optical lens 222, wherein, in order to ensure the mounting accuracy of the 1/4 wave plate 225, the third surface 2313 of the second optical lens 222 may be configured to be planar or nearly planar. Further, the second surface 2312 of the first optical lens 211 is also disposed in a corresponding plane shape or is close to a plane shape, and the polarizing beam splitter 226 and the polarizer 227 are integrated on the second surface 2312 of the first optical lens 211, so that the connection between the polarizing beam splitter 226, the polarizer 227 and the first optical lens 221 is more stable due to the plane shape. In the present application, only by relatively correcting the relative angles of the polarizer 227, the polarizing beam splitter 226 and the 1/4 wave plate 225, and enabling the relative positions of the polarizer 227, the polarizing beam splitter 226 and the 1/4 wave plate 225 to have a good projection image under the combined action of the optical lens 211, it can be explained that the relative positions of the polarizer 227, the polarizing beam splitter 226 and the 1/4 wave plate 225 and the optical lens 211 do not affect the projection image, and the whole has a good image. Further, the polarizing beam splitter 226 and the polarizer 227 are fixed on the first optical lens 221, and the 1/4 wave plate 225 is fixed on the second optical lens 222 to assemble the first optical lens 221 and the second optical lens 222 in an active alignment manner, so that the assembly effect of the folded optical path component is better, the assembly angle error between the folded optical path components is improved, and the assembly yield is higher.

As shown in fig. 7, specifically, the optical lens 211 is disposed in the lens barrel 114, and a side surface of the lens barrel 114 may be provided with a corresponding adjustment channel 129, and the adjustment channel 129 is mainly used for adjusting the position of the optical lens 211. In a specific embodiment, the adjustment channels 129 are disposed at positions corresponding to the second optical lens 222, wherein the number of the adjustment channels 129 is at least two, which are symmetrically disposed on the lens barrel 114. In the assembly process, the tilt or rotation position of the second optical lens 222 can be adjusted through the adjustment channel 129 reserved on the lens barrel 114, specifically, the first optical lens 221 is in a fixed state, the second optical lens 222 is adjusted through an active calibration mode, and since the polarizing element 212 is integrated on the optical lens 211, the position of the second optical lens 222 and/or the polarizing element 212 can be adjusted through adjusting the position of the optical lens 221, so that the assembly precision between the optical units 20 is improved, a clear projection image is obtained, and the assembly yield of the projection module is improved.

In another possible embodiment, the polarizing element 212 is disposed separately from the optical lens 211, that is, a part of the polarizing element 212 is disposed between the first optical lens 221 and the second optical lens 222, wherein the polarizing element 212 disposed between the first optical lens 221 and the second optical lens 222 further includes a 1/4 wave plate 225, a polarizing beam splitter 226 and a polarizer 227, and the part of the polarizing element 212 may be directly integrated on the optical lens 221, as in at least one embodiment of the present application, the polarizing beam splitter 226 and the polarizer 227 in the polarizing element 212 are integrated on the second surface of the first optical lens 221. Further, the 1/4 wave plate 225 may be used as a separate optical element, wherein an alternative embodiment is integrated on a planar transparent substrate, and the planar transparent substrate on which the 1/4 wave plate is integrated is disposed adjacent to the third surface 2313 of the second optical lens 222, i.e. the surface of the second optical lens 222 away from the projection unit 30, and in some alternative embodiments, a certain gap exists between the 1/4 wave plate and the third surface 2313 of the second optical lens 222. The side wall of the lens barrel 114 corresponding to the side edge of the second optical lens 222 is provided with an adjusting channel 129, and the position of the polarizing element 212 can be adjusted through the adjusting channel 129 reserved on the lens barrel 114, in some alternative embodiments, the tilt or rotation position of the 1/4 wave plate 225 can be specifically adjusted, so that the 1/4 wave plate is matched with other polarizing elements 212 integrated on the optical lens 221, and thus, the assembly error of the 1/4 wave plate 225 relative to other optical unit devices is improved, so as to obtain a clearly projected image.

In another possible embodiment, a side wall of the lens barrel 114 corresponding to a side edge of the first optical lens 221 is provided with an adjusting channel 129, and the position of the polarizing element 221 can be adjusted through the adjusting channel 129 reserved on the lens barrel 114, so that, in at least one embodiment of the present application, the polarizing beam splitter 226 and the polarizer 227 in the polarizing element 212 are integrated on the second surface of the first optical lens 221, and the relative position of the first optical lens 221 and/or the polarizing beam splitter 226 and/or the polarizer 227 can be adjusted through the adjusting channel 129 reserved on the lens barrel 114, and in some embodiments, the tilt or rotation position of the above device is not adjusted, so that the 1/4 wave plate is matched with other polarizing elements 212 integrated on the optical lens 221, thereby improving the assembly error of the 1/4 wave plate 225 relative to other optical unit devices, so as to obtain a clear projection image.

As shown in fig. 5 and 6, the present application provides a folded light path scheme for reducing parasitic light, wherein the first optical lens 2211, the second optical lens 222 and the third optical lens 223 are sequentially disposed at one end of the optical lens 211 away from the projection unit 30, and the second optical lens 222 and the third optical lens 223 are connected by gluing, so as to improve the integration of the optical system and shorten the size of the projection module. The first surface 2311 of the first optical lens 221 is convex, and the third surface 2313 of the second optical lens 222 is concave with substantially the same curvature, so as to reduce aberration of the projected image, improve image quality of the projected image, and shorten the size of the lens module. The fourth surface 2314 of the second optical lens 222 is a plane, and the third surface 2313 of the second optical lens is a concave surface, which can reduce aberration of the projection screen. The sixth surface 2316 of the third optical lens 223 is convex, and the fifth surface 2315 of the third optical lens 223 is convex, so as to reduce aberration of the projection screen, improve image quality of the projection screen, and shorten the height of the projection module. The polarizer 227 and the polarization beam splitter 226 are sequentially stacked on the first surface 2311, and the polarizer 227 is located at a position further away from the projection unit 30, so as to improve the packaging integration of the projection module and shorten the size of the projection module.

The second optical lens 222 and the third optical lens 223 are glued by glue, and in this embodiment, the 1/4 wave plate 225 is attached between the second optical lens 222 and the third optical lens 223, and a glue layer is disposed between the 1/4 wave plate 225 and the fourth surface 2314, and further, the glue layer is disposed between the 1/4 wave plate 225 and the fifth surface 2315. The semi-reflective and semi-transparent film 224 is disposed outside the sixth surface 2316, and in this embodiment, the reflective ratio of the semi-reflective and semi-transparent film 224 may be 40% reflective, 60% reflective, 40% reflective, and preferably 50% reflective (the overall system light efficiency is the highest), so as to improve the utilization of the overall projected light.

Specifically, the other surfaces of the optical lens 211 that contact air may be coated with a reflective film (AR film), and the reflectance of the anti-reflective film is less than 0.5%, so that the utilization of the projected light can be enhanced. In this embodiment, the second surface 2312 and the third surface 2313 have a spherical or aspherical surface with a negative radius of curvature, and the sixth surface 2316 has a spherical or aspherical surface with a negative radius of curvature, so as to reduce the aberration of the projection screen, improve the quality of the projection screen, and shorten the size of the projection module. In the present embodiment, the materials of the first optical lens 221 and the third optical lens 223 are high refractive index materials, and the refractive index is 1.7-1.8, wherein the refractive index of the second optical lens 222 is low refractive index materials, and the refractive index is 1.60-1.65, so as to optimize the optical design of the module and shorten the size of the lens projection module.

The present application also provides another possible folded light path scheme for reducing stray light, wherein the end of the optical lens 211 away from the projection unit 30 is the first optical lens 221, the second optical lens 222 and the third optical lens 223 at a time, and the first optical lens 221 and the second optical lens 222 are fixedly connected by gluing. Further, the gap between the first optical lens 221 and the second optical lens 222 is smaller than the gap between the second optical lens 222 and the third optical lens 223, and the distance between the second optical lens 222 and the first optical lens 221 is kept constant. The distance between the second optical lens 222 and the third optical lens 223 can be adjusted accordingly, and the specific adjusting device will be described in detail below in connection with the projection module.

Specifically, the second surface 2312 of the first optical lens 221 is planar, the third surface 2213 of the second optical lens 222 adjacent thereto is also planar, and the optical unit 20 further has a polarizing element 212 for extending the optical path, wherein a part of refractive devices are disposed between the first optical lens 221 and the second optical lens 222. In order to further reduce the space occupied by the refraction device, the refraction device may be directly integrated on the second surface 2312 and/or the third surface 2313 by plating, and the 1/4 wave plate 225, the polarizing beam splitter 226 and the polarizing plate 227 in the polarizing element 212 are disposed between the second surface 2212 and the third surface 2213. In an alternative embodiment, the 1/4 wave plate may be integrated on the second surface 2312, the polarizing beamsplitter 226 is integrated on the 1/4 wave plate 225, the polarizer 226 is integrated on the polarizing beamsplitter 227, i.e., the refractive devices are all fixed on the second surface 2312. In another alternative embodiment, the 1/4 wave plate 225 is fixed to the second surface 2312 by plating, and then the polarizing beamsplitter 226 and the polarizer 227 are sequentially fixed to the 1/4 wave plate 225. Specifically, the 1/4 wave plate 225, the polarizing beam splitter 226 and the polarizer 227 can be selectively disposed on the second surface 2312 and/or the third surface 2313, so long as the function of extending the optical path is achieved.

Further, to facilitate the corresponding plating on the optical lens 211, the surfaces of the first optical lens 221, the second optical lens 222 and the third optical lens 223 that are optionally plated may be configured to be planar, specifically, the 1/4 wave plate 225, the polarizing beam splitter 226 and the polarizing plate 227 are fixed on the second surface 2312 and/or the third surface 2313, and the corresponding second surface 2312 and the third surface 2313 may be configured to be planar to facilitate the process plating. The first surface 2211 of the first optical lens 221 is configured as a convex surface, and the fourth surface 2214 of the second optical lens 222 is configured as a concave surface, so as to reduce aberration of a projection screen, improve image quality of the projection screen, and shorten the size of the projection module. The fifth surface 2315 and the sixth surface 2316 of the third optical lens 223 can be selectively arranged to be convex to better optimize the optical imaging system, and the light projected by the projection unit 30 passes through the third optical lens 223, passes through the second optical lens 222 and then exits the first optical lens 221 to be received by human eyes.

The semi-reflective and semi-transparent film 224 is disposed on the sixth surface 2316, and in this embodiment, the reflective ratio of the semi-reflective and semi-transparent film 224 may reflect 40% of the projected image 60%, or may reflect 60% of the projected image 40%, and preferably reflect 50% of the projected image 50% (the light efficiency of the whole system is the highest), so as to improve the brightness utilization rate of the projected image. The surface of the optical lens 211 where the refraction device is not provided may be plated with an antireflection film (AR film) having a reflectance of less than 0.5%, thereby enabling enhancement of the utilization ratio of the projected light. In this embodiment, the second surface 2312 and the third surface 2313 of the optical lens 211 are planar, so that a film can be coated on the planar lens to extend the light path of the projection light, and the sixth surface 2316 can be configured as a convex surface, wherein the radius of curvature of the sixth surface 2316 is a sphere or an aspherical surface with a negative value, so as to reduce the aberration of the projection screen, improve the image quality of the projection screen, and shorten the size of the projection module. In this embodiment, the materials of the first optical lens 221 and the third optical lens 223 are high refractive index materials, and the refractive index is 1.60-1.65, so that the optical design of the projection module can be optimized, and the size of the projection module can be shortened.

As shown in fig. 4 to 10, in particular, the gap between the lenses of the optical lens 211 can be adjusted accordingly, in this embodiment, the distance between the lenses is mainly adjusted by the adjusting unit 10, in this embodiment, the optical lens 211 includes the first optical lens 221, the second optical lens 222 and the third optical lens 223, wherein the distance between the first optical lens 221 and the second optical lens 222 is kept fixed, and the distance between the second optical lens 222 and the third optical lens 223 can be adjusted accordingly. Further, the adjusting unit 10 includes a pressing cover 111, a rotating ring 112, a gasket 113 and a lens barrel 114, wherein the lens barrel 114 is mainly used for accommodating the optical lens 211, and the rotating ring 112 is disposed on an outer side surface of the lens barrel 114 and can rotate relative to the lens barrel 114 to adjust a distance between lenses of the optical lens 211. The gasket 113 is disposed between the rotating ring 112 and the lens barrel 114 to ensure the stability of the connection between the lens barrel 114 and the rotating ring 112, and the gland 111 is disposed on the combined upper end surface of the rotating ring 112 and the lens barrel 114 to prevent external dust from entering into the gap between the rotating ring 112 and the lens barrel 114 while restricting the upward movement of the rotating ring 112, thereby ensuring the imaging stability of the projection module.

As shown in fig. 10, in a specific embodiment, the lens barrel 114 is mainly used for accommodating the optical lens 211, and in order to facilitate the passing of the projection light, the lens barrel 114 has a second light through hole 127, the second light through hole 127 is reserved in the middle of the lens barrel 114, and the optical lens 211 is accommodated in the second light through hole 127 of the lens barrel 114. The light beam projected by the projection unit 30 passes through the optical lens 211 and then is emitted from the second light-passing hole 127 of the lens barrel 114, so as to reach the human eye or other receiving units. Further, the lens barrel 114 has a barrel body 128, the barrel body 128 can be divided into a barrel inner side 1216 and a barrel outer side 1217, wherein the barrel inner side 1216 is mainly used for accommodating the optical lens 211, the barrel outer side 1217 is used for arranging the rotating ring 112, further, the barrel inner side 1216 has a plurality of steps on which the optical lens 211 is fixed, and the lenses are arranged separately by utilizing the structure of the steps, so that an adjustable gap exists between the lenses.

In the present application, the optical lens 211 includes a first optical lens 221, a second optical lens 222 and a third optical lens 223, and the corresponding barrel inner 1216 of the barrel 114 is provided with three steps, namely, a first step 12161, a second step 12162 and a third step 12163 along the optical axis. Wherein the first step 12161 is provided with the first optical lens 221, the second step 12162 is provided with the second optical lens 222, and the third step 12163 is provided with the third optical lens 223, the diameter of the first optical lens 221 may be made smaller than the diameter of the second optical lens 222 in order to achieve a smaller head of the optical unit 20. The height of the corresponding first step 12161 is smaller than the height of the second step 12162, so that the first optical lens 221 is disposed at the exit position of the lens barrel 114, and the distance between the second optical lens 222 and the third optical lens 223 can be adjusted accordingly, so that the distance between the second step 12162 and the third step 12163 is greater than the distance between the second step 12162 and the first step 12161.

As shown in fig. 9, in particular, in one alternative embodiment, the outer side 1217 of the lens barrel is composed of a first ring 12171 and a second ring 12172, the diameter of the first ring 12171 is smaller than the diameter of the second ring 12172, and the first ring 12171 and the second ring 12172 are integrally formed. The outer side 1217 of the lens barrel is provided with a rotating ring 112 and a pressing cover 111, so that the pressing cover 111 is better fixed with the outer side 12172 of the lens barrel, and the first ring 12171 of the outer side 1217 of the lens barrel is further provided with a corresponding fastening piece 12173 for fixing with the pressing cover 111. Wherein the diameters of the first ring 12171 and the second ring 12172 are different, a horizontal ring 12174 is formed at the connection between the first ring 12171 and the second ring 12172, and the horizontal ring 12174 can form a corresponding bearing action on the rotating ring 112. The outer side 1217 of the lens barrel further has a second circular ring 12172, in order to better arrange the rotating ring 112 on the second circular ring 12172, the second circular ring 12172 is correspondingly provided with the first circular groove 12173 and the second circular groove 12174, the first circular groove 12173 and the second circular groove 12174 are arranged on the second circular ring 12172 in parallel, wherein the first circular groove 12173 and the second circular groove 12174 are arranged in parallel with each other with a certain distance therebetween.

In order to adjust the position of the third optical lens 223 in the lens barrel, the second ring 12172 of the outer side 1217 of the lens barrel has a plurality of through holes 12175, which penetrate from the inner side 1216 of the lens barrel to the outer side 1217 of the lens barrel, wherein the number of through holes 12175 may be plural. In a specific embodiment, the number of through holes 12175 is three, which are equally spaced on the outer side of the second ring 12172. The through hole 12175 has a certain inclination angle with the bottom of the lens barrel 114, the inclination angle is not greater than 45 °, and further, the orthographic projection of the through hole 12175 on the bottom surface of the lens barrel 114 is consistent with the bottom edge of the lens barrel 114. The third optical lens 223 may be provided with a corresponding fastener, such as a screw, and the fastener is fixed to a side of the third optical lens 223, one side of the fastener is fixed to the third optical lens 223, and the other side is a free end, and the free end may extend a certain length along the through hole 12175 on the outer side 1217 of the lens barrel. Wherein the number of fasteners may be plural, in a specific embodiment, the number of fasteners is consistent with the number of through holes 12175, the fasteners are uniformly arranged along the edge of the third optical lens 223, and one side of the fasteners extends into the through holes 12175 to contact the rotating ring 112.

As shown in fig. 8, 9 and 10, further, the rotary ring 112 is disposed outside the lens barrel 114, the rotary ring 112 has a third through-hole 123 and a circular ring body 124, and the third through-hole 123 on the rotary ring 112 is aligned with the center of the second through-hole 127 on the lens barrel 114 to ensure the passing of the projection light. In a specific embodiment, the rotary ring 112 is disposed on an outer side surface of the lens barrel 114, and a corresponding gasket 113 is disposed between the rotary ring 112 and the lens barrel 114 in order to stably connect the rotary ring 112 and the lens barrel 114. The gasket 113 may be made of a rubber material, and specifically, the gasket 113 includes a first sealing ring 125 and a second sealing ring 126, where the first sealing ring 125 is disposed in the first circular groove 12173, and the second sealing ring 126 is disposed in the second circular groove 12174, so that the rotating ring 112 and the lens barrel 114 can be better fixed by the intermediary of the first sealing ring 125 and the second sealing ring 126.

As shown in fig. 8, the ring body 124 on the rotary ring 112 can be specifically divided into an inner ring 1214 and an outer ring 1215, the inner ring 1214 has a horizontal boss 12141 and a vertical groove 12142, and the horizontal boss 12141 is supported on the horizontal ring 12174 on the outer barrel 1217, so that the rotary ring 112 and the golden child 114 are supported by the horizontal ring 12174 correspondingly. Further, a plurality of vertical grooves 12142 are further disposed on the inner side 1214 of the ring, the positions of the vertical grooves 12142 correspond to the positions of the through holes 12175 disposed on the lens barrel 114, the vertical grooves 12142 have a certain height, and the number of the vertical grooves 12142 is consistent with the number of the through holes 12175. One side of the fastener on the third optical lens 223 is fixedly connected with the third optical lens 223, and the other side of the fastener passes through the through hole 12175 on the outer side 1217 of the lens barrel and stretches into the vertical groove 12142.

In the present application, by adjusting the position of the rotating ring 112 through the vertical groove 12142 on the inner ring 1214 of the rotating ring 112, the vertical groove 12142 limited on the inner ring 1414 drives the fastener to move along the direction of the through hole 12175 on the lens barrel 114. Further, the through hole 12175 of the lens barrel 114 has a predetermined direction, and the direction of the vertical groove 12142 of the inner side 1214 of the ring 112 is consistent with the direction of the optical axis. When the rotating ring 112 moves along the direction of the optical axis, the vertical groove 12142 disposed thereon can drive the third optical lens 223 to move along the direction of the optical axis, so as to adjust the gap between the third optical lens 223 and the optical lens 222, thereby changing the optical system parameters of the projection module to meet different imaging requirements. Further, in order to facilitate adjustment of the rotating ring 112, the outer ring side 1215 of the ring body 124 is provided with corresponding screw threads 12151, and the screw threads 1151 are mainly used to increase friction force of the rotating ring 112, so as to facilitate better holding of the rotating ring 112. Wherein the thread 12151 on the outer side 1215 of the ring may be provided as a horizontal thread or a vertical thread, without limitation.

In a specific embodiment, a corresponding gland 111 is disposed at a top end position of the rotating ring 112 contacting the lens barrel 114, and the gland 111 can be used to limit the movement of the rotating ring 112. The cover 111 has a fourth light-passing hole 121, the fourth light-passing hole 141 is aligned with the center of the third light-passing hole 123 on the rotating ring 112, and the projection light can be emitted from the fourth light-passing hole 121 on the cover 111. The gland 111 further has a gland ring 122, the gland ring 122 is mainly fixed at the top position of the lens barrel 114, corresponding fastening members 12173 are disposed at the top position of the lens barrel 114, corresponding fastening grooves 1313 are disposed on the gland ring 122, and the gland ring 122 is fixed with the lens barrel 114 through the fastening grooves 1313 thereon, so as to prevent the rotary ring 112 from being separated from the lens barrel 114.

Further, the gland ring 122 further has a first gland ring 1311 and a second gland ring 1312, the first gland ring 1311 and the second gland ring 1313 can be integrally formed, the diameter of the first gland ring 1311 is smaller than the diameter of the second gland ring 1312, wherein the first gland ring 1311 covers the surface of the first optical lens 221. By covering the surface of the first optical lens 221 with the first capping ring 1311, the light can be prevented from leaking out of the side of the first optical lens 221, and parasitic light can be prevented from being generated during imaging. The second cover ring 1312 is disposed on a side surface of the first optical lens 221, wherein a lower end surface of the second cover ring 1312 is supported on the horizontal boss 12141 of the rotating ring 112, and the size of the cover 111 can be further reduced while the gap between the rotating ring 112 and the lens barrel 114 is closed, thereby realizing miniaturization of the entire projection module.

The projection module provided by the application can be applied to virtual equipment, in particular to head-mounted virtual equipment, and in order to improve the use effect of a user, the number of the projection modules in the virtual equipment can be two, the two projection modules can be adjacently arranged, and the interval between the two projection modules is consistent with the interval of human eyes. Correspondingly, in order to improve the imaging quality of the virtual device, the gap between the two projection modules in the virtual device can be correspondingly adjusted according to the binocular gap of the user so as to improve the experience effect of the user. Referring to fig. 1, in the imaging process, the projection light emitted by the projection module 30 through the transmission of the optical unit 20 and the effect of the adjusting unit 10 can be emitted from the front end of the optical lens 211, so that the human eyes can receive the light signal emitted by the projection unit 30, i.e. the human eyes can receive the image information transmitted by the projection unit 30, thereby improving the imaging quality, enabling the user to feel like being personally on the scene and further enhancing the imaging authenticity.

The foregoing has outlined the basic principles, features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention, which is defined by the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A projection module comprises a projection unit, an adjusting unit and an optical unit, wherein the projection light emitted by the projection unit can be emitted through the optical unit, and the optical unit is arranged inside the adjusting unit;

2. The projection module of claim 1, wherein the polarizing element comprises a semi-reflective semi-transmissive film, a 1/4 wave plate, a polarizing beamsplitter and a polarizer, the polarizing element being capable of being integrated onto the optical lens by coating, wherein the semi-reflective semi-transmissive film is integrated onto a third optical lens.

3. The projection module of claim 2, wherein the polarizing element is a semi-reflective semi-transmissive film, a 1/4 wave plate, a polarizer, and a polarizing beam splitter in this order along the optical axis, wherein the 1/4 wave plate, the polarizer, and the polarizing beam splitter are disposed between the first optical lens and the second optical lens.

4. A projection module as claimed in claim 3, characterized in that the 1/4 wave plate is arranged on a planar object, which is arranged between the first optical lens and the second optical lens, wherein the 1/4 wave plate is fixed to the planar object by means of a coating.

5. The projection module according to claim 2, wherein the polarizer and the polarizing beam splitter are sequentially superimposed on the first optical lens, the polarizer being located at a position farther from a projection light end, wherein the polarizing beam splitter is in contact with a surface of the first optical lens, the polarizer being disposed on the polarizing beam splitter.

6. The projection module of any of claims 1-5, wherein the first optical lens and the third optical lens are made of a high refractive index material and the second optical lens is made of a low refractive index material.

7. The projection module of claim 6, wherein a distance between the optical lenses is adjustable, wherein a distance between the first optical lens and the second optical lens remains unchanged, and a distance between the second optical lens and the third optical lens is adjustable.

8. The projection module of claim 6, wherein a distance between the optical lenses is adjustable, wherein the second optical lens is glued to the third optical lens and a position of the first optical lens is adjustable.

9. The projection module of claim 7, wherein a gap between the first optical lens and the second optical lens is less than a gap between the second optical lens and the third optical lens.

10. The projection module of claim 9, wherein an end of the first optical lens adjacent to the projection unit is a first surface, and a lens surface shape of the first surface is a plane.

11. The projection module of claim 10, wherein the second optical lens is glued to the third optical lens, the 1/4 wave plate being disposed between the second optical lens and the third optical lens, wherein the first optical lens and the second optical lens are fixable by active alignment.