Projection system and ar projection device

Abstract

The application provides a projection system and an AR projection device. The projection system comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging module. The projection system has a first optical axis and a second optical axis which are perpendicular to each other. The fourth lens is a polarization beam splitter. The first optical axis and the second optical axis intersect in the polarization beam splitter. The first lens has positive focal power. The second lens has focal power. The third lens has focal power. The object side of the third lens is cemented with the image side of the second lens. The fifth lens has positive focal power. The total optical length TTL from the object side of the second lens to the image side along the second optical axis, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system satisfy the following relationship: 1.60 < TTL / (f*FNO*tan(FOV)) < 1.75. The application solves the problem that the projection system in the prior art is difficult to simultaneously achieve miniaturization and high-definition projection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical display devices, in particular to a projection system and an AR projection device. BACKGROUND

[0002] With the rapid development and application of portable consumer electronic display products, augmented reality (AR) devices have very wide application prospects in the fields of industrial manufacturing and maintenance, educational display, outdoor sports, and vehicle navigation.

[0003] Among them, the projection system is a kind of core device for the fusion of virtual and real visual effects of the AR projection device. With the iterative development of AR technology and the demand of consumers for high performance and light weight of portable devices, the projection system is developing towards miniaturization, high-definition display, and low cost. However, in general projection systems, high-definition projection often requires a large number of lenses, making it difficult to reduce the size in all aspects. High-definition projection using more aspherical lenses will quickly increase the manufacturing cost, and the separate assembly of each lens will bring more unstable factors to the process and tolerance.

[0004] That is, the projection system in the prior art has the problem that miniaturization and high-definition projection cannot be simultaneously considered. SUMMARY

[0005] The main purpose of the present application is to provide a projection system and an AR projection device to solve the problem that the projection system in the prior art cannot simultaneously consider miniaturization and high-definition projection.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a projection system is provided, the projection system comprising a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging module, the projection system having a first optical axis and a second optical axis perpendicular to each other, the diaphragm, the first lens and the fourth lens being sequentially arranged along the first optical axis, the second lens, the third lens, the fourth lens, the fifth lens and the imaging module being sequentially arranged along the second optical axis, the fourth lens being a polarization beam splitter, the first optical axis and the second optical axis intersecting in the polarization beam splitter; wherein the first lens has a positive focal power, the object side surface of the first lens being a convex surface; the second lens has a focal power, the object side surface of the second lens being a convex surface; the third lens has a focal power, the object side surface of the third lens being cemented with the image side surface of the second lens; the fifth lens has a positive focal power; along the second optical axis, the optical total length TTL from the object side surface of the second lens to the image surface, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system satisfy: 1.60 < TTL / (f*FNO*tan(FOV)) < 1.75.

[0007] Further, a focal length f1 of the first lens and a length T14 of the first lens along the first optical axis to a side surface of the fourth lens away from the stop satisfy: 3.00 < f1 / T14 < 6.10.

[0008] Further, the focal length f1 of the first lens and a system focal length f of the projection system satisfy: 3.10 < f1 / f < 6.60.

[0009] Further, the focal length f1 of the first lens and a central thickness T4 of the fourth lens satisfy: 3.50 < f1 / T4 < 7.70.

[0010] Further, the length T14 of the first lens along the first optical axis to the side surface of the fourth lens away from the stop and an optical total length TTL along the second optical axis from the object side surface of the second lens to the image surface satisfy: 0.50 < T14 / TTL < 0.70.

[0011] Further, a focal length f5 of the fifth lens and the system focal length f of the projection system satisfy: 1.40 < f5 / f < 2.10.

[0012] Further, an aperture SD21 of the object side surface of the second lens and the central thickness T4 of the fourth lens satisfy: 1.050 < SD21 / T4 < 1.064.

[0013] Further, an on-axis distance SP14 between the first lens and the fourth lens, an on-axis distance SP23 between the second lens and the fourth lens, an on-axis distance SP34 between the third lens and the fourth lens, an on-axis distance SP45 between the fourth lens and the fifth lens, and the optical total length TTL along the second optical axis from the object side surface of the second lens to the image surface satisfy: 0.05 < (SP14+SP23+SP34+SP45) / TTL < 0.12.

[0014] Further, a combined focal length f23 of the second lens and the third lens and the focal length f5 of the fifth lens satisfy: 1.00 < f23 / f5 < 1.60.

[0015] Further, a focal length f2 of the second lens and a focal length f3 of the third lens satisfy: -1.20 < f2 / f3 < -0.90.

[0016] Further, the projection system further comprises an optical waveguide structure, the optical waveguide structure being disposed at the stop.

[0017] Further, the optical waveguide structure has a coupling-in entrance, a size of the coupling-in entrance being equal to a size of the stop.

[0018] Further, the optical waveguide structure is one of an array optical waveguide, a geometric optical waveguide, and a diffractive optical waveguide.

[0019] According to another aspect of the present application, there is provided an AR projection device, comprising the projection system as described above.

[0020] According to the technical scheme of the present application, the projection system comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging module. The projection system has a first optical axis and a second optical axis perpendicular to each other. The diaphragm, the first lens and the fourth lens are sequentially arranged along the first optical axis. The second lens, the third lens, the fourth lens, the fifth lens and the imaging module are sequentially arranged along the second optical axis. The fourth lens is a polarization beam splitter. The first optical axis and the second optical axis intersect in the polarization beam splitter. The first lens has positive focal power. The object side of the first lens is convex. The second lens has focal power. The object side of the second lens is convex. The third lens has focal power. The object side of the third lens is cemented with the image side of the second lens. The fifth lens has positive focal power. The total optical length TTL from the object side of the second lens to the image side along the second optical axis, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system satisfy the condition formula: 1.60 < TTL / (f*FNO*tan(FOV)) < 1.75.

[0021] The projection system of the present application reasonably arranges the positional relationship of each lens, constrains the focal power and surface shape of each lens, and constrains the condition formula between the total optical length TTL from the object side of the second lens to the image side, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system: 1.60 < TTL / (f*FNO*tan(FOV)) < 1.75. This is beneficial to make the main parameters of the projection system meet the target value, take into account the system length size, keep the optical performance and overall size in a relatively balanced state, ensure miniaturization and high-definition display, and also be beneficial to maintain the projection system in a high-performance state with good optical element processing size and low process assembly difficulty, greatly improve the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the description of the exemplary embodiments of the present application, serve to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0023] Figure 1 A structural schematic diagram of the projection system of embodiment one of the present application is shown;

[0024] Figure 2 A light path diagram of the projection system in Figure 1 is shown;

[0025] Figures 3 to 6 respectively showFigure 1 The spherical aberration curve, field curvature curve, distortion curve and chromatic aberration curve of the projection system;

[0026] Figure 7 FIG2 shows a schematic structural diagram of a projection system according to a second embodiment of the present invention;

[0027] Figures 8 to 11 Shown respectively Figure 7 The spherical aberration curve, field curvature curve, distortion curve and chromatic aberration curve of the projection system;

[0028] Figure 12 FIG2 shows a schematic structural diagram of a projection system according to a third embodiment of the present invention;

[0029] Figures 13 to 16 Shown respectively Figure 12 The spherical aberration curve, field curvature curve, distortion curve and chromatic aberration curve of the projection system;

[0030] Figure 17 FIG2 shows a schematic structural diagram of a projection system according to a fourth embodiment of the present invention;

[0031] Figures 18 to 21 Shown respectively Figure 17 The spherical aberration curve, field curvature curve, distortion curve and chromatic aberration curve of the projection system.

[0032] The above drawings include the following reference numerals:

[0033] L0, aperture; L1, first lens; L1S1, object-side surface of the first lens; L1S2, image-side surface of the first lens; L2, second lens; L2S1, object-side surface of the second lens; L2S2, image-side surface of the second lens; L3, third lens; L3S1, object-side surface of the third lens; L3S2, image-side surface of the third lens; L4, fourth lens; L4S1, object-side surface of the fourth lens; L4S2, image-side surface of the fourth lens; L5, fifth lens; L5S1, object-side surface of the fifth lens; L5S2, image-side surface of the fifth lens; L6, protective glass. DETAILED DESCRIPTION

[0034] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0036] In the present application, the orientation words such as "upper", "lower", "top", "bottom" are generally directed to the directions shown in the drawings, or are directed to the vertical, perpendicular or gravity directions of the components themselves, unless otherwise specified. Similarly, for the convenience of understanding and description, "inner" and "outer" refer to the inner and outer relative to the contour of the components themselves, but the above orientation words are not used to limit the present application.

[0037] It should be noted that the terms first, second, third, etc. in the present description are only used to distinguish one feature from another, and do not represent any limitation on the features. Therefore, the first lens discussed below can also be referred to as the second lens or the third lens without departing from the teachings of the present application.

[0038] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for the convenience of illustration. Specifically, the shape of the spherical or aspherical surface shown in the drawings is shown by way of example. That is, the shape of the spherical or aspherical surface is not limited to the shape of the spherical or aspherical surface shown in the drawings. The drawings are merely examples and are not strictly drawn to scale.

[0039] In this context, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not specified, it means that the lens surface is concave at least in the paraxial region. The surface of each lens near the object side is the object side surface of the lens, and the surface of each lens near the image side is the image side surface of the lens. The judgment of the surface shape in the paraxial region can be based on the judgment method of those skilled in the art, with the R value (R refers to the radius of curvature in the paraxial region, usually refers to the R value on the lens data in the optical software) positive or negative to judge the convexity or concavity. In terms of the object side surface, when the R value is positive, it is determined to be convex, and when the R value is negative, it is determined to be concave; in terms of the image side surface, when the R value is positive, it is determined to be concave, and when the R value is negative, it is determined to be convex.

[0040] In order to solve the problem that the existing projection system cannot simultaneously achieve miniaturization and high-definition projection, the present application provides a projection system and an AR projection device.

[0041] As Figures 1 to 21As shown, in an optional embodiment of the present application, the projection system comprises a diaphragm, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and an imaging module, the projection system has a first optical axis and a second optical axis perpendicular to each other, the diaphragm, the first lens and the fourth lens are sequentially arranged along the first optical axis, the second lens, the third lens, the fourth lens, the fifth lens and the imaging module are sequentially arranged along the second optical axis, the fourth lens is a polarization beam splitter, the first optical axis and the second optical axis intersect in the polarization beam splitter; wherein the first lens has positive refractive power, the object side of the first lens is convex; the second lens has refractive power, the object side of the second lens is convex; the third lens has refractive power, the object side of the third lens is cemented with the image side of the second lens; the fifth lens has positive refractive power; along the second optical axis, the optical total length TTL from the object side of the second lens to the image, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system satisfy: 1.60 < TTL / (f*FNO*tan(FOV)) < 1.75.

[0042] The projection system of the present application reasonably arranges the positional relationship of each lens, constrains the refractive power and surface shape of each lens, constrains the condition formula between the optical total length TTL from the object side of the second lens to the image, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system: 1.60 < TTL / (f*FNO*tan(FOV)) < 1.75, which is beneficial to make the main parameters of the projection system meet the target value, take into account the system length size, keep the optical performance and overall size in a relatively balanced state, ensure miniaturization and high-definition display, and also be beneficial to maintain the projection system in a high-performance state with good optical element processing size and low process assembly difficulty, greatly improve the production efficiency.

[0043] In addition, the first optical axis is perpendicular to the diaphragm, and the second optical axis is perpendicular to the imaging module. The imaging module comprises at least one protective glass for protecting the image plane. The first lens receives the polarized light reflected by the fourth lens and converges the light out of the diaphragm. The converging effect of the first lens helps the fourth lens to have a smaller size. The image side of the first lens can be designed as a plane and is glued to the surface of the fourth lens facing the first lens. After gluing, the assembly tolerance can be further reduced to reduce the assembly difficulty, improve the assembly yield, and enhance the structural reliability. The object side of the second lens is attached to or prepared by an optical reflection device, which is an important design to realize the optical multiplexing function. The light from the image source is reflected by the optical reflection device and converges to the first lens through the polarized reflection surface of the fourth lens, realizing the repeated propagation of the light in the second lens, the third lens and the fourth lens. The image side of the second lens and the object side of the third lens are glued and are both curved surfaces, so that the curvatures are the same. After gluing, the assembly tolerance can be reduced and the structural reliability can be improved. The fourth lens has a polarization beam splitter layer inside the fourth lens, which is at an angle of 45° with the first optical axis and the second optical axis, respectively transmits and reflects different linearly polarized light. The surface of the fourth lens facing the third lens is glued with a transmission type quarter wave plate for changing the polarization of the transmitted light. The image side of the fourth lens is provided with a linear polarizer so that the light incident on the fourth lens is reflected at the polarization beam splitter layer to improve the contrast of the projected image. The image side of the third lens can also be designed as a plane. The image side of the third lens is glued to the fourth lens. After gluing with the fourth lens, the assembly tolerance can be reduced and the structural reliability can be improved. The fifth lens has positive focal power, which is helpful for converging the illumination light while correcting the imaging aberration. The image side of the fifth lens can also be designed as a plane. One surface of the first lens and the third lens can be designed as a plane and glued to the fourth lens. The reduction of the number of curved surfaces of the optical lens helps to reduce the processing cost. Each gluing of the optical lens can reduce the number of tolerances and assembly tolerances, thereby greatly improving the mass production of the lens.

[0044] The projection system provided by the application can reduce the material processing cost, reduce the process flow and assembly tolerance to improve the mass production, and has the advantages of high definition and miniaturization of the projection.

[0045] Preferably, along the second optical axis, the optical total length TTL from the object side of the second lens to the image plane, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system satisfy: 1.62 < TTL / (f*FNO*tan(FOV)) < 1.72.

[0046] In the embodiment, the focal length f1 of the first lens and the length T14 of the first lens along the first optical axis to the side surface of the fourth lens away from the stop satisfy: 3.00 < f1 / T14 < 6.10. Satisfying the condition formula is conducive to limiting the length of the projection system on the first optical axis, that is, controlling the length dimension of the projection system in the stop coupling-out direction in a smaller range, and also conducive to the miniaturization of the entire projection system.

[0047] Optionally, the effective maximum field of view FOV of the projection system satisfies: 29° < FOV < 31°. Such a setting can limit the projection field of view to a range that takes into account the viewing effect of the human eye and the coupling-in angle capability of various light waveguide structures, and is conducive to realizing high-definition projection with small distortion.

[0048] In the embodiment, the focal length f1 of the first lens and the system focal length f of the projection system satisfy: 3.10 < f1 / f < 6.60. Satisfying this relationship is conducive to reasonably distributing the optical power of the first lens, so that the optical power of the first lens is positive and within a certain range, which can avoid the case that the other lenses are too large in size and the overall size is too large due to the too large focal length of the first lens, and avoid the case that the tolerance sensitivity is increased due to the too small focal length of the first lens.

[0049] In the embodiment, the focal length f1 of the first lens and the central thickness T4 of the fourth lens satisfy: 3.50 < f1 / T4 < 7.70. Satisfying this relationship makes the ratio of the focal length of the first lens to the thickness of the fourth lens within a reasonable range, which is conducive to relatively gentle propagation of the light coupled out by the first lens within the fourth lens, while reducing the aberration generated within the fourth lens and keeping a relatively reasonable size.

[0050] In the embodiment, the length T14 of the first lens along the first optical axis to the side surface of the fourth lens away from the stop and the total optical length TTL along the second optical axis from the object side surface of the second lens to the image surface satisfy: 0.50 < T14 / TTL < 0.70. Satisfying the relationship is conducive to limiting the size of the projection system in the stop direction within a smaller range, which is conducive to the miniaturization of the projection system, and also avoids the problem of structural interference of the projection system when used in combination due to the too long size of the projection system on the second optical axis.

[0051] In the embodiment, the focal length f5 of the fifth lens and the system focal length f of the projection system satisfy: 1.40 < f5 / f < 2.10. Such a setting is conducive to balancing part of the system aberration of the fifth lens, and the CRA at the modulation image surface is at a smaller level, and the positive optical power is also conducive to the convergence of the illumination light.

[0052] In the embodiment, the aperture SD21 of the object side of the second lens and the central thickness T4 of the fourth lens satisfy 1.050<SD21 / T4<1.064. Such arrangement is conducive to the constraint of the size of the second lens and the fourth lens, and increases the processing feasibility of the second lens and the fourth lens while ensuring miniaturization.

[0053] In the embodiment, the on-axis distance SP14 between the first lens and the fourth lens, the on-axis distance SP23 between the second lens and the fourth lens, the on-axis distance SP34 between the third lens and the fourth lens, the on-axis distance SP45 between the fourth lens and the fifth lens, and the total optical length TTL from the object side of the second lens to the image plane along the second optical axis satisfy 0.05<(SP14+SP23+SP34+SP45) / TTL<0.12. Such arrangement is conducive to making full use of the structural space for setting the imaging lens, and makes the distribution of the lenses in space more compact, which is conducive to miniaturization.

[0054] In the embodiment, the combined focal length f23 of the second lens and the third lens and the focal length f5 of the fifth lens satisfy 1.00<f23 / f5<1.60. Satisfying the relationship can make the refractive power of each lens in the projection system be reasonably distributed, which is conducive to the balance of aberration and tolerance in the system.

[0055] In the embodiment, the focal length f2 of the second lens and the focal length f3 of the third lens satisfy -1.20<f2 / f3<-0.90. Such arrangement is conducive to better correction of system chromatic aberration, and greatly improves the imaging quality of the system.

[0056] In the embodiment, the projection system further comprises an optical waveguide structure, and the optical waveguide structure is arranged at the stop. The optical waveguide structure has a coupling entrance, and the size of the coupling entrance is equal to the size of the stop.

[0057] In the embodiment, the optical waveguide structure is one of an array optical waveguide, a geometric optical waveguide, and a diffractive optical waveguide. The array optical waveguide is a structure composed of a plurality of parallel arranged optical waveguides, the geometric optical waveguide is a structure in which light is refracted and reflected by different refractive index distributions, and the diffractive optical waveguide is a structure in which image light is expanded, coupled in, and coupled out by using a diffraction grating.

[0058] The application further provides an AR projection device, and the AR projection device comprises the projection system.

[0059] For example, the AR projection device can be a head-mounted virtual display device or a vehicle-mounted head-up display device.

[0060] Specifically, the lens in the projection system of the present application can be a spherical glass lens or an aspherical glass lens, or a spherical injection molded lens or an aspherical injection molded lens, which can be set according to actual needs.

[0061] In the present application, at least one of the mirror surfaces of each lens is an aspherical mirror surface. The aspherical lens has the characteristic that the curvature continuously changes from the center of the lens to the periphery of the lens. Unlike the spherical lens which has a constant curvature from the center of the lens to the periphery of the lens, the aspherical lens has better curvature radius characteristics, and has the advantages of improving the distortion aberration and improving the astigmatism aberration. After using the aspherical lens, the aberration that occurs during imaging can be eliminated as much as possible, thereby improving the imaging quality.

[0062] Since the aspherical surface is obtained by rotating the meridional surface around the optical axis for one revolution, the structure has rotational symmetry, and in an ideal optical system, the aberrations of the meridional surface and the sagittal surface can be well corrected; at the same time, due to its unique lens model, it can provide sufficient space for subsequent related adjustment, making the related structure and assembly process more flexible and not reducing the imaging quality too much.

[0063] The following further describes specific surface types and parameters of the projection system applicable to the above embodiments with reference to the accompanying drawings.

[0064] It should be noted that any one of the following embodiments one to four is applicable to all embodiments of the present application.

[0065] Embodiment one

[0066] As shown in Figures 1 to 6 , the projection system of embodiment one is described. Figure 1 A structural schematic diagram of the projection system of embodiment one is shown. Figure 2 A light path diagram of the projection system in Figure 1 is shown.

[0067] As shown in Figure 1 , the projection system includes: an aperture stop L0, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a protective glass L6. The aperture stop L0, the first lens L1, and the fourth lens L4 are sequentially arranged along a first optical axis, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass L6 are sequentially arranged along a second optical axis, the fourth lens L4 is a polarization beam splitter, and the first optical axis and the second optical axis intersect at the fourth lens L4. In the direction of the first optical axis, the side of the aperture stop is the object side, and the side away from the aperture stop is the image side. On the second optical axis, the side of the second lens L2 away from the third lens L3 is the object side, and the side of the protective glass L6 away from the fifth lens L5 is the image side.

[0068] The first lens L1 has positive optical power, with its object-side surface L1S1 being convex and its image-side surface L1S2 being flat. The second lens L2 has positive optical power, with its object-side surface L2S1 being convex and its image-side surface L2S2 being convex. The third lens L3 has negative optical power, with its object-side surface L3S1 being concave and its image-side surface L3S2 being flat. The fourth lens has its object-side surface L4S1 being flat and its image-side surface L4S2 being flat. The fifth lens L5 has positive optical power, with its object-side surface L5S1 being convex and its image-side surface L5S2 being flat.

[0069] The image-side surface L1S2 of the first lens is cemented to the surface of the fourth lens L4 facing the image-side surface L1S2. The second lens L2 is cemented to the third lens L3, and the third lens LE is cemented to the fourth lens LE.

[0070] In this embodiment, the total effective focal length f of the projection system is 6.434 mm, the total optical length TTL of the projection system along the second optical axis from the object side surface of the second lens to the image plane is 9.686 mm, the maximum field of view FOV of the projection system is 30°, and the aperture value FNO of the projection system is 1.608.

[0071] Table 1 shows the basic structural parameters of the projection system of Example 1, wherein the units of the curvature radius and thickness / distance are all millimeters (mm).

[0072]

[0073] Table 1

[0074] Figure 3 The spherical aberration curve of the projection system of the first embodiment is shown. Figure 4 The field curvature curve of the projection system of the first embodiment is shown. Figure 5 FIG. 4 shows a distortion curve of the projection system of the first embodiment. Figure 6 The chromatic aberration curve of the projection system of the first embodiment is shown.

[0075] according to Figures 3 to 6 It can be seen that the projection system provided in the first embodiment can achieve good imaging quality.

[0076] Example 2

[0077] like Figures 7 to 11 As shown, the projection system of the second embodiment is described. Figure 7 FIG. 1 shows a schematic structural diagram of a projection system according to a second embodiment.

[0078] like Figure 7As shown, the projection system comprises: a diaphragm L0, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a protective glass L6. The diaphragm L0, the first lens L1, and the fourth lens L4 are sequentially arranged along a first optical axis, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass L6 are sequentially arranged along a second optical axis, the fourth lens L4 is a polarization beam splitter, and the first optical axis and the second optical axis intersect at the fourth lens L4. In the direction of the first optical axis, the side of the diaphragm is the object side, and the side away from the diaphragm is the image side. On the second optical axis, the side of the second lens L2 away from the third lens L3 is the object side, and the side of the protective glass L6 away from the fifth lens L5 is the image side.

[0079] The first lens L1 has a positive focal power, the object side surface L1S1 of the first lens is a convex surface, and the image side surface L1S2 of the first lens is a plane. The second lens L2 has a negative focal power, the object side surface L2S1 of the second lens is a convex surface, and the image side surface L2S2 of the second lens is a concave surface. The third lens L3 has a positive focal power, the object side surface L3S1 of the third lens is a convex surface, and the image side surface L3S2 of the third lens is a plane. The object side surface L4S1 of the fourth lens is a plane, and the image side surface L4S2 of the fourth lens is a plane. The fifth lens L5 has a positive focal power, the object side surface L5S1 of the fifth lens is a plane, and the image side surface L5S2 of the fifth lens is a convex surface.

[0080] The image side surface L1S2 of the first lens and the side surface of the fourth lens L4 facing it are glued. The second lens L2 and the third lens L3 are glued, the third lens LE and the fourth lens LE are glued, and the object side surface L5S1 of the fifth lens and the fourth lens L4 are glued.

[0081] In this embodiment, the total effective focal length f of the projection system is 6.132 mm, the total optical length TTL of the projection system along the second optical axis from the object side surface of the second lens to the image surface is 9.315 mm, the maximum field of view FOV used by the projection system is 30°, and the aperture value FNO of the projection system is 1.53.

[0082] Table 2 shows the basic structure parameter table of the projection system of embodiment two, wherein the units of the curvature radius and the thickness / distance are millimeters (mm).

[0083]

[0084] Table 2

[0085] In embodiment two, the surface type of each aspheric lens can be defined by, but not limited to, the following aspheric formula:

[0086]

[0087] wherein x is the sag of the aspherical surface at a height h along the optical axis, c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the inverse of the radius of curvature R in Table 1 above), k is the conic constant, and Ai is the correction coefficient of the i-th order of the aspherical surface. Table 3 below gives the high-order term coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20 that can be used in the aspherical surface of Example Two.

[0088]

[0089]

[0090] Table 3

[0091] Figure 8 A curve of spherical aberration of the projection system of Example Two is shown. Figure 9 A curve of field curvature of the projection system of Example Two is shown. Figure 10 A curve of distortion of the projection system of Example Two is shown. Figure 11 A curve of chromatic aberration of the projection system of Example Two is shown.

[0092] According to Figures 8 to 11 It can be seen that the projection system given in Example Two can achieve good imaging quality.

[0093] Example Three

[0094] As Figures 12 to 16 shown, a projection system of Example Three is described. Figure 12 A structure schematic diagram of the projection system of Example Three is shown.

[0095] As Figure 12 shown, the projection system includes an aperture stop L0, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a protective glass L6. The aperture stop L0, the first lens L1, and the fourth lens L4 are sequentially arranged along a first optical axis, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass L6 are sequentially arranged along a second optical axis, the fourth lens L4 is a polarization beam splitter, and the first optical axis and the second optical axis intersect at the fourth lens L4. In the direction of the first optical axis, the side of the aperture stop is the object side, and the side away from the aperture stop is the image side. On the second optical axis, the side of the second lens L2 away from the third lens L3 is the object side, and the side of the protective glass L6 away from the fifth lens L5 is the image side.

[0096] The first lens L1 has positive refractive power, the object side surface L1S1 of the first lens is a convex surface, and the image side surface L1S2 of the first lens is a plane. The second lens L2 has negative refractive power, the object side surface L2S1 of the second lens is a convex surface, and the image side surface L2S2 of the second lens is a concave surface. The third lens L3 has positive refractive power, the object side surface L3S1 of the third lens is a convex surface, and the image side surface L3S2 of the third lens is a convex surface. The object side surface L4S1 of the fourth lens is a plane, and the image side surface L4S2 of the fourth lens is a plane. The fifth lens L5 has positive refractive power, the object side surface L5S1 of the fifth lens is a convex surface, and the image side surface L5S2 of the fifth lens is a plane.

[0097] The image side surface L1S2 of the first lens and the side surface of the fourth lens L4 facing the side surface are glued.

[0098] In the embodiment, the total effective focal length f of the projection system is 6.395 mm, the total optical length TTL of the projection system along the second optical axis from the object side surface of the second lens to the image surface is 9.82 mm, the maximum field of view FOV used by the projection system is 30°, and the aperture value FNO of the projection system is 1.59.

[0099] Table 4 shows a table of basic structural parameters of the projection system of embodiment three, wherein the units of the radius of curvature and the thickness / distance are millimeters (mm).

[0100]

[0101]

[0102] Table 4

[0103] Table 5 shows the high-order term coefficients of the aspherical surfaces that can be used in embodiment two, wherein each aspherical surface type can be defined by the formula (1) given in embodiment two.

[0104] Fifth lens Asphericity coefficient / face number L5S1 R 8.57213618963009 K -35.929707623052 A4 0.0199222667708863 A6 -0.030928347736135 A8 0.0337186435914787 A10 -0.0222713058809637 A12 0.00913777041956876 A14 -0.00234947058465942 A16 0.000368318123710091 A18 -3.21877409978883e-005 A20 1.20223428895953e-006

[0105] Table 5

[0106] Figure 13 The spherical aberration curve of the projection system of embodiment three is shown. Figure 14 The field curvature curve of the projection system of embodiment three is shown. Figure 15 The distortion curve of the projection system of embodiment three is shown. Figure 16 The chromatic aberration curve of the projection system of embodiment three is shown.

[0107] According to Figures 13 to 16 It can be seen that the projection system given in embodiment three can achieve good imaging quality.

[0108] Embodiment four

[0109] AsFigures 17 to 21 A projection system of embodiment four is shown. Figure 17 A structural schematic diagram of the projection system of embodiment four is shown.

[0110] As shown in Figure 17 The projection system comprises: a diaphragm L0, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a protective glass L6. The diaphragm L0, the first lens L1, and the fourth lens L4 are sequentially arranged along a first optical axis, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass L6 are sequentially arranged along a second optical axis, the fourth lens L4 is a polarization beam splitter, and the first optical axis and the second optical axis intersect at the fourth lens L4. In the direction of the first optical axis, the side of the diaphragm is the object side, and the side away from the diaphragm is the image side. On the second optical axis, the side of the second lens L2 away from the third lens L3 is the object side, and the side of the protective glass L6 away from the fifth lens L5 is the image side.

[0111] The first lens L1 has a positive focal power, the object side surface L1S1 of the first lens is a convex surface, and the image side surface L1S2 of the first lens is a plane. The second lens L2 has a negative focal power, the object side surface L2S1 of the second lens is a convex surface, and the image side surface L2S2 of the second lens is a concave surface. The third lens L3 has a positive focal power, the object side surface L3S1 of the third lens is a convex surface, and the image side surface L3S2 of the third lens is a convex surface. The object side surface L4S1 of the fourth lens is a plane, and the image side surface L4S2 of the fourth lens is a plane. The fifth lens L5 has a positive focal power, the object side surface L5S1 of the fifth lens is a convex surface, and the image side surface L5S2 of the fifth lens is a convex surface.

[0112] The image side surface L1S2 of the first lens and the side surface of the fourth lens L4 facing it are glued.

[0113] In this embodiment, the total effective focal length f of the projection system is 6.340 mm, the total optical length TTL of the projection system along the second optical axis from the object side surface of the second lens to the image surface is 9.73 mm, the maximum field of view FOV used by the projection system is 30°, and the aperture value FNO of the projection system is 1.58.

[0114] Table 6 shows the basic structural parameter table of the projection system of embodiment four, wherein the units of the curvature radius and the thickness / distance are millimeters (mm).

[0115]

[0116] Table 6

[0117] Table 7 shows the high-order term coefficients of the aspherical mirrors that can be used in embodiment two, wherein each aspherical surface type can be defined by the formula (1) given in embodiment two.

[0118]

[0119]

[0120] Table 7

[0121] Figure 18 A curve of spherical aberration of the projection system of Example Four is shown. Figure 19 A curve of field curvature of the projection system of Example Four is shown. Figure 20 A curve of distortion of the projection system of Example Four is shown. Figure 21 A curve of chromatic aberration of the projection system of Example Four is shown.

[0122] According to Figures 18 to 21 It can be seen that the projection system given by Example Four can achieve good imaging quality.

[0123] In summary, Examples One to Four respectively satisfy the relationships shown in Table 8.

[0124] Conditional expression / embodiment 1 2 3 4 TTL / (f*FNO*tan(FOV)) 1.62 1.72 1.67 1.68 f1 / T14 3.60 3.16 6.96 4.12 f1 / f 3.37 3.12 6.54 3.48 f1 / T4 3.99 3.60 7.67 4.58 T14 / TTL 0.62 0.65 0.61 0.55 f5 / f 1.84 1.41 1.66 2.06 (SP14+SP23+SP34+SP45) / TTL 0.11 0.11 0.11 0.06 f23 / f5 1.03 1.54 1.25 1.01 F2 / F3 -0.97 -1.07 -1.03 -1.16 SD21 / T4 1.050 1.064 1.062 1.062

[0125] Table 8

[0126] Table 9 gives the effective focal length f of the projection systems of Examples One to Four, the effective focal lengths f1 to f5 of each lens, etc. (unit: mm).

[0127]

[0128]

[0129] Table 9

[0130] Obviously, the above-described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work should belong to the scope of protection of the present application.

[0131] It should be noted that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0132] It should be noted that the terms "first", "second", and the like, used in the description and in the claims of the present application as well as above-mentioned figures are used to distinguish between similar objects and not necessarily for describing a specific sequential or chronological order. It is to be understood that the use of data so designated is not meant to limit a given item described by such data to the same category as other data designated by the same designations, but instead is so designated only for convenience as a means of discriminating between the two series of items that refer to a same data.

[0133] The preferred embodiments of the application described herein are examples of the present application and are not intended to limit the scope of the application. Various modifications and changes can be made thereto by those skilled in the art which freely adapt to the idea and principles of the application, without departing from the spirit and scope thereof, and it is to be understood that such modifications and changes are to be included within the scope of the application as defined by the appended claims.

Claims

1. A projection system, characterized in that: The projection system includes an aperture, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and an imaging module. The projection system has a first optical axis and a second optical axis that are perpendicular to each other. The aperture, the first lens, and the fourth lens are sequentially arranged along the first optical axis. The second lens, the third lens, the fourth lens, the fifth lens, and the imaging module are sequentially arranged along the second optical axis. The fourth lens is a polarizing beam splitter prism. The first optical axis and the second optical axis intersect in the polarizing beam splitter prism. The first lens has positive refractive power, and the object side surface of the first lens is convex; the second lens has optical power, and the object side surface of the second lens is convex; the third lens has optical power, and the object side surface of the third lens is cemented to the image side surface of the second lens; the fifth lens has positive refractive power; the projection system consists of five lenses; The total optical length TTL from the object side of the second lens to the image plane along the second optical axis, the system focal length f of the projection system, the effective maximum field angle FOV of the projection system and the aperture value FNO of the projection system satisfy the following conditions: 1.60 <TTL / (f*FNO*tan(FOV))<1.75。 2. The projection system according to claim 1, wherein: A focal length f1 of the first lens and a length T14 from the first lens along the first optical axis to a surface of the fourth lens away from the aperture satisfy the following: 3.16≤f1 / T14≤6.

96.

3. The projection system according to claim 1, wherein: The focal length f1 of the first lens and the system focal length f of the projection system satisfy: 3.10 <f1 / f≤6.54。 4. The projection system according to claim 1, wherein: The focal length f1 of the first lens and the center thickness T4 of the fourth lens satisfy the following relationship: 3.60≤f1 / T4<7.

70.

5. The projection system according to claim 1, wherein: The length T14 of the first lens along the first optical axis to the surface of the fourth lens away from the aperture and the total optical length TTL from the object side of the second lens to the image plane along the second optical axis meet the following conditions: 0.50 <T14 / TTL<0.70。 6. The projection system according to claim 1, wherein: The focal length f5 of the fifth lens satisfies the following relationship with the system focal length f of the projection system: 1.40 <f5 / f<2.10。 7. The projection system according to any one of claims 1 to 6, characterized in that The diameter SD21 of the object-side surface of the second lens and the center thickness T4 of the fourth lens satisfy the following: 1.050≤SD21 / T4≤1.

064.

8. The projection system according to any one of claims 1 to 6, characterized in that The on-axis distance SP14 between the first lens and the fourth lens, the on-axis distance SP23 between the second lens and the fourth lens, the on-axis distance SP34 between the third lens and the fourth lens, the on-axis distance SP45 between the fourth lens and the fifth lens, and the total optical length TTL from the object side surface of the second lens to the image plane along the second optical axis satisfy the following: 0.05<(SP14+SP23+SP34+SP45) / TTL<0.

12.

9. The projection system according to any one of claims 1 to 6, characterized in that The combined focal length f23 of the second lens and the third lens and the focal length f5 of the fifth lens satisfy: 1.00 <f23 / f5≤1.54。 10. The projection system according to any one of claims 1 to 6, characterized in that The focal length f2 of the second lens and the focal length f3 of the third lens satisfy: -1.20 <f2 / f3≤-0.97。 11. The projection system according to any one of claims 1 to 6, characterized in that: The projection system further includes a light waveguide structure, which is arranged at the aperture.

12. The projection system according to claim 11, wherein: The optical waveguide structure has a coupling inlet, and the size of the coupling inlet is equal to the size of the aperture.

13. The projection system according to claim 11, wherein: The optical waveguide structure is one of an array optical waveguide, a geometric optical waveguide and a diffraction optical waveguide.

14. An AR projection device, characterized in that: The AR projection device includes the projection system according to any one of claims 1 to 13.

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