A projection system

Abstract

The present application provides a kind of projection system, from exit pupil side to image source side in turn: diaphragm;The first lens of positive refractive power or negative refractive power is spherical lens, the object side of first lens is convex, the image side is concave, or the object side is concave, the image side is convex;The second lens of positive refractive power or negative refractive power is spherical lens, the object side of second lens is concave, the image side is convex, or the object side and the image side are both concave, or the object side and the image side are both convex;The third lens of positive refractive power is spherical lens or aspherical lens, the object side and the image side of third lens are both convex;The fourth lens of positive refractive power or negative refractive power is spherical lens or aspherical lens, the object side of fourth lens is convex, the image side is concave, or the object side and the image side are both concave, or the object side is concave, the image side is convex.The present application makes projection system realize with the advantages of large field of view, large aperture and miniaturization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of imaging lenses, in particular to a projection system. BACKGROUND

[0002] In recent years, with the rapid development of augmented reality and virtual reality, AR glasses and VR head-mounted products have gradually become popular, and people have higher requirements for the optical and mechanical system in such portable products in terms of volume, weight, image quality, etc. At present, the projection lenses used in augmented reality glasses and other products on the market basically adopt a spherical or aspherical optical system of four or more pieces, which has good imaging effect, but the optical and mechanical volume is large and the total weight is high, which is difficult to meet the continuous miniaturization and lightness of smart glasses. SUMMARY

[0003] In view of the deficiencies of the prior art, the purpose of the present application is to provide a projection system to solve the technical problems mentioned in the background art.

[0004] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0005] A projection system, a total of five lenses, in order along the optical axis from the exit pupil side to the image source side:

[0006] a diaphragm;

[0007] a first lens with positive or negative focal power, the first lens being a spherical lens, the object side of the first lens being convex and the image side being concave, or the object side being concave and the image side being convex;

[0008] a second lens with positive or negative focal power, the second lens being a spherical lens, the object side of the second lens being concave and the image side being convex, or both the object side and the image side being concave, or both the object side and the image side being convex;

[0009] a third lens with positive focal power, the third lens being a spherical lens or an aspherical lens, both the object side and the image side of the third lens being convex;

[0010] a fourth lens with positive or negative focal power; the fourth lens being a spherical lens or an aspherical lens, the object side of the fourth lens being convex and the image side being concave, or both the object side and the image side being concave, or the object side being concave and the image side being convex;

[0011] The total optical length TTL of the projection system and the effective focal length f satisfy: TTL / f < 1.73.

[0012] According to an aspect of the above technical solution, the maximum field of view fov of the projection system and the total optical length TTL of the projection system satisfy: fov / TTL<2.8.

[0013] According to an aspect of the above technical solution, the combined effective focal length f12 of the first lens and the second lens and the combined effective focal length f34 of the third lens and the fourth lens satisfy: -2.2<f12 / f34<1.8.

[0014] According to an aspect of the above technical solution, the outer diameter D11 of the object side surface of the first lens, the outer diameter D21 of the object side surface of the second lens, the curvature radius of the image source side surface of the second lens, and the effective focal length f satisfy: -8<(D11+D21)*R22 / f<13.

[0015] According to an aspect of the above technical solution, the total optical length TTL of the projection system, the air gap T12 of the first lens and the second lens on the optical axis, and the air gap T23 of the second lens and the third lens on the optical axis satisfy: 2<TTL*(T12+T23)<10.

[0016] According to an aspect of the above technical solution, the curvature radius R1 of the side surface close to the exit pupil of the first lens and the effective focal length f of the projection system satisfy: -0.7<R1 / f<0.7.

[0017] According to an aspect of the above technical solution, the effective focal length F2 of the second lens and the effective focal length f of the projection system satisfy: -1<F2 / f<15.

[0018] Compared with the prior art, the present application has the beneficial effects that:

[0019] The projection system of the present application realizes the advantages of large field of view, large aperture, and miniaturization by reasonably matching the lens shape and optical power combination between each lens.

[0020] Additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 FIG. 1 is a structural schematic diagram of a projection system according to an embodiment of the present application;

[0022] Figure 2 FIG. 2 is an astigmatism curve (left) and a distortion curve (right) of the projection system according to the embodiment of the present application;

[0023] Figure 3 FIG. 3 is a structural schematic diagram of a projection system according to another embodiment of the present application;

[0024] Figure 4 a plot of astigmatism (left) and a plot of distortion (right) of the projection system in Embodiment 2 of the present application;

[0025] Figure 5 a schematic structural diagram of the projection system in Embodiment 3 of the present application;

[0026] Figure 6 a plot of astigmatism (left) and a plot of distortion (right) of the projection system in Embodiment 3 of the present application;

[0027] Figure 7 a schematic structural diagram of the projection system in Embodiment 4 of the present application;

[0028] Figure 8 a plot of astigmatism (left) and a plot of distortion (right) of the projection system in Embodiment 4 of the present application;

[0029] The following detailed description will further describe the present application with reference to the above-mentioned drawings. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The accompanying drawings show several embodiments of the present application. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application is more thorough and complete.

[0031] It should be noted that when an element is referred to as being "fixedly attached" to another element, it can be directly on the other element or there can be intervening elements. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can be present. As used herein the terms "vertical", "horizontal", "left", "right", and the like are merely for purposes of illustration.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0033] The present application provides a projection system, which has five lenses, and along the optical axis, from the exit pupil side to the image source side, they are:

[0034] a diaphragm;

[0035] the first lens has positive refractive power or negative refractive power, the first lens is a spherical lens, the object side of the first lens is convex, and the image side of the first lens is concave, or the object side of the first lens is concave, and the image side of the first lens is convex;

[0036] the second lens has positive refractive power or negative refractive power, the second lens is a spherical lens, the object side of the second lens is concave, and the image side of the second lens is convex, or the object side and the image side of the second lens are both concave, or the object side and the image side of the second lens are both convex;

[0037] the third lens has positive refractive power, the third lens is a spherical lens or an aspherical lens, and the object side and the image side of the third lens are both convex;

[0038] the fourth lens has positive refractive power or negative refractive power, the fourth lens is a spherical lens or an aspherical lens, the object side of the fourth lens is convex, and the image side of the fourth lens is concave, or the object side and the image side of the fourth lens are both concave, or the object side of the fourth lens is concave, and the image side of the fourth lens is convex;

[0039] In some embodiments, the total optical length TTL of the projection system and the effective focal length f satisfy: TTL / f < 1.73. Satisfying the above range makes the projection system have the advantage of short total length, the volume of the projection lens can be <0.4 cc, and the weight is also reduced accordingly. When the projection lens is applied to an augmented reality glasses, the comfort of the wearer can be improved, and the application prospect is broad.

[0040] In some embodiments, the maximum field of view fov of the projection system and the total optical length TTL of the projection system satisfy: fov / TTL < 2.8. Because the optical waveguide sheet in the prior art can only receive parallel light with a small angle, the fov in the present application is <40°, so that the projected image can smoothly enter the optical waveguide sheet for transmission, and the above relationship can make the projection system have a small fov and a short total length and a small volume.

[0041] In some embodiments, the combined effective focal length f12 of the first lens and the second lens and the combined effective focal length f34 of the third lens and the fourth lens satisfy: -2.2 < f12 / f34 < 1.8. By making the projection system satisfy the above relationship, the design sensitivity of the projection system is reduced, the refractive power of each lens in the projection system is reasonably configured, the imaging quality of the optical system is improved, the angle of the light exiting the optical system after being folded by the lens group is reduced, the incident angle of the light entering the image side photosensitive element of the optical system is reduced, the photosensitive performance of the photosensitive element is improved, and the imaging quality of the optical system is improved.

[0042] In some embodiments, the outer diameter D11 of the object side surface of the first lens, the outer diameter D21 of the object side surface of the second lens, the radius of curvature of the image source side surface of the second lens, and the effective focal length f satisfy the following relationship: -8 < (D11+D21)*R22 / f < 13. By satisfying the above range, the outer diameter of the first lens and the radius of curvature of the image source side surface of the second lens are reasonably set, so as to achieve the minimum size and light weight of the entire lens.

[0043] In some embodiments, the optical total length TTL of the projection system, the air gap T12 of the first lens and the second lens on the optical axis, and the air gap T23 of the second lens and the third lens on the optical axis satisfy the following relationship: 2 < TTL*(T12+T23) < 10. By satisfying the above range, the air gap of the first lens and the second lens on the optical axis and the air gap of the second lens and the third lens on the optical axis are reasonably set, which is beneficial to reduce the sensitivity of the lens and improve the production and assembly yield of the lens. The comprehensive control of the above conditional formula makes the projection lens meet the small size design target while improving the market competitiveness of the lens.

[0044] In some embodiments, the radius of curvature R1 of the first lens near the side surface of the exit pupil and the effective focal length f of the projection system satisfy the following relationship: -0.7 < R1 / f < 0.7. The larger R1 is, the lower the sensitivity is, and the higher the actual production and assembly yield is. The smaller R1 is, the stronger the light converging ability of the first lens is, and the shorter the focal length is, which is more conducive to compressing the total length of the system. By satisfying the above range, the R1 / f ratio is reasonably configured, which can ensure the actual assembly yield while reducing the size of the lens.

[0045] In some embodiments, the effective focal length F2 of the second lens and the effective focal length f of the projection system satisfy the following relationship: -1 < F2 / f < 15. By making the projection system satisfy the above relationship, the refractive power of the second lens in the optical system is properly matched, the surface type design of the second lens is more simple and flexible, the aberration is reduced, and the balance of the overall aberration correction and imaging quality of the optical system is simplified.

[0046] The application will be further described in the following embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection system are different, and the specific differences can be referred to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the application, but the embodiments of the application are not limited to the following embodiments. Any changes, substitutions, combinations or simplifications made without departing from the innovative points of the application should be regarded as equivalent replacement methods, and are included in the protection scope of the application.

[0047] Embodiment 1

[0048] Please refer to Figure 1, as shown in the structural schematic diagram of the projection system provided in Embodiment 1 of the present application, sequentially from the exit pupil side to the image source side along the optical axis are:

[0049] a diaphragm ST0;

[0050] a first lens L1 with positive focal power, the first lens being a spherical lens, the object side S1 of the first lens being a convex surface and the image side S2 being a concave surface;

[0051] a second lens L2 with positive focal power, the second lens being a spherical lens, the object side S3 of the second lens being a concave surface and the image side S4 being a convex surface;

[0052] a third lens L3 with positive focal power, the third lens being a spherical lens, the object side S5 and the image side S6 of the third lens both being convex surfaces;

[0053] a fourth lens L4 with negative focal power; the fourth lens being an aspherical lens, the object side S7 of the fourth lens being a concave surface and the image side S8 being a convex surface.

[0054] a prism L5;

[0055] The related parameters of the lenses in the projection system in Embodiment 1 are shown in Table 1-1, wherein the units of the curvature radius and the thickness are millimeters (mm).

[0056] Table 1-1

[0057]

[0058] The surface type parameters of the aspherical lens of the projection system in Embodiment 1 are shown in Table 1-2.

[0059] Table 1-2

[0060]

[0061] In the present embodiment, according to Figure 2 It can be known that the projection system given in Embodiment 1 can achieve good imaging quality.

[0062] Embodiment 2

[0063] Please refer to Figure 3 , as shown in the structural schematic diagram of the projection system provided in Embodiment 3 of the present application, sequentially from the exit pupil side to the image source side along the optical axis are:

[0064] a diaphragm ST0;

[0065] a first lens L1 with positive focal power, the first lens being a spherical lens, the object side S1 of the first lens being a convex surface and the image side S2 being a concave surface;

[0066] a second lens L2 with negative focal power, the second lens being a spherical lens, the object side S3 of the second lens being a concave surface and the image side S4 being a convex surface;

[0067] a third lens L3 with positive focal power, the third lens being a spherical lens, the object side S5 and the image side S6 of the third lens both being convex surfaces;

[0068] a fourth lens L4 with positive focal power; the fourth lens being an aspherical lens, the object side S7 of the fourth lens being a concave surface and the image side S8 being a concave surface;

[0069] a prism L5.

[0070] The related parameters of the lenses in the projection system in Embodiment 2 are shown in Table 2-1, wherein the units of the curvature radius and the thickness are millimeters (mm).

[0071] Table 2-1

[0072]

[0073] The surface type parameters of the aspherical lens of the projection system in Embodiment 2 are shown in Table 2-2.

[0074] Table 2-2

[0075]

[0076] In this embodiment, according to Figure 4 It can be known that the projection system given in Embodiment 2 can achieve good imaging quality.

[0077] Embodiment 3

[0078] Please refer to Figure 5 , which is a structure schematic diagram of the projection system provided in Embodiment 3 of the present application, and along the optical axis, from the exit pupil side to the image source side, they are:

[0079] a stop ST0;

[0080] a first lens L1 with positive focal power, the first lens being a spherical lens, the object side S1 of the first lens being a convex surface and the image side S2 being a concave surface;

[0081] a second lens L2 with positive focal power, the second lens being a spherical lens, the object side S3 of the second lens being a concave surface and the image side S4 being a concave surface;

[0082] a third lens L3 with positive focal power, the third lens being a spherical lens, the object side S5 and the image side S6 of the third lens both being convex surfaces;

[0083] the fourth lens L4 has negative focal power; the fourth lens is an aspheric lens, the object side S7 of the fourth lens is a convex surface, and the image side S8 of the fourth lens is a concave surface;

[0084] the prism L5.

[0085] The related parameters of the lenses in the projection system in Embodiment 3 are shown in Table 3-1, wherein the units of the radius of curvature and the thickness are millimeters (mm).

[0086] Table 3-1

[0087]

[0088] The surface type parameters of the aspheric lenses in the projection system in Embodiment 3 are shown in Table 3-2.

[0089] Table 3-2

[0090]

[0091] In this embodiment, according to Figure 6 It can be known that the projection system given in Embodiment 3 can achieve good imaging quality.

[0092] Embodiment 4

[0093] Please refer to Figure 7 , which is a structural schematic diagram of a projection system provided in Embodiment 4 of the present application, and along the optical axis, from the exit pupil side to the image source side, there are sequentially:

[0094] the stop ST0;

[0095] the first lens L1 has positive focal power; the first lens is a spherical lens, the object side S1 of the first lens is a concave surface, and the image side S2 of the first lens is a convex surface;

[0096] the second lens L2 has positive focal power; the second lens is a spherical lens, the object side S3 of the second lens is a convex surface, and the image side S4 of the second lens is a convex surface;

[0097] the third lens L3 has positive focal power; the third lens is a spherical lens, the object side S5 and the image side S6 of the third lens are both convex surfaces;

[0098] the fourth lens L4 has negative focal power; the fourth lens is an aspheric lens, the object side S7 of the fourth lens is a convex surface, and the image side S8 of the fourth lens is a concave surface;

[0099] the prism L5.

[0100] The related parameters of the lenses in the projection system in Embodiment 4 are shown in Table 4-1, wherein the units of the radius of curvature and the thickness are millimeters (mm).

[0101] Table 4-1

[0102]

[0103] The surface parameters of the aspherical lens of the projection system in Example 4 are shown in Table 4-2.

[0104] Table 4-2

[0105]

[0106] In this embodiment, according to Figure 8 It can be seen that the projection system given in Example 4 can achieve good imaging quality.

[0107] Referring to Table 5, the optical characteristics corresponding to the projection systems provided in the above four embodiments are shown, including the related numerical values corresponding to each expression described above.

[0108] Table 5

[0109]

[0110] In summary, the projection system in the present application, by reasonably matching the lens shape and optical power combination between each lens, realizes the advantages of large field of view, large aperture and miniaturization.

[0111] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0112] The above-described embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but should not be understood as a limitation on the patent scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.

Claims

1. A projection system, characterized in that, There are five lenses in total, arranged along the optical axis from the exit pupil side to the image source side as follows: Aperture; A first lens with positive optical power, wherein the first lens is a spherical lens, and the object side of the first lens is convex and the image side is concave; A second lens with positive optical power, wherein the second lens is a spherical lens, and the object side of the second lens is concave and the image side is convex; A third lens with positive optical power, wherein the third lens is a spherical lens and both the object side and the image side of the third lens are convex surfaces; A fourth lens with negative optical power, wherein the fourth lens is an aspherical lens, and the object side of the fourth lens is concave and the image side is convex; The total optical length (TTL) and effective focal length (f) of the projection system satisfy the following condition: TTL / f < 1.73; The effective focal length of the first lens is 15.91, the effective focal length of the second lens is 87.56, the effective focal length of the third lens is 3.88, and the effective focal length of the fourth lens is -5.

84.

2. The projection system according to claim 1, characterized in that, The maximum field of view fov of the projection system and the total optical length TTL of the projection system satisfy: fov / TTL<2.

8.

3. The projection system according to claim 1, characterized in that, The combined effective focal length f12 of the first lens and the second lens and the combined effective focal length f34 of the third lens and the fourth lens satisfy: -2.2 < f12 / f34 < 1.

8.

4. The projection system according to claim 1, characterized in that, The outer diameter D11 of the object surface of the first lens, the outer diameter D21 of the object surface of the second lens, the radius of curvature of the image source side surface of the second lens, and the effective focal length f satisfy the following: -8 < (D11 + D21) * R22 / f < 13.

5. The projection system according to claim 1, characterized in that, The total optical length TTL of the projection system, the air gap T12 between the first and second lenses on the optical axis, and the air gap T23 between the second and third lenses on the optical axis satisfy a 2 <TTL*(T12+T23)<10。 6. The projection system according to claim 1, characterized in that, The radius of curvature R1 of the first lens near the exit pupil side satisfies -0.7 with the effective focal length f of the projection system. <R1 / f<0.7。 7. The projection system according to claim 1, characterized in that, The effective focal length F2 of the second lens and the effective focal length f of the projection system satisfy: -1 <F2 / f<15。

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