Projection system

Abstract

The invention provides a projection system. From an exit pupil side to an image source side, the projection system comprises a diaphragm; the first lens is a spherical lens, the object side surface of the first lens is a convex surface, the image side surface of the first lens is a concave surface, or the object side surface of the first lens is a concave surface, and the image side surface of the first lens is a convex surface; the second lens is a spherical lens, the object side surface of the second lens is a concave surface, the image side surface of the second lens is a convex surface, or both the object side surface and the image side surface are concave surfaces, or both the object side surface and the image side surface are convex surfaces; the third lens is a spherical lens or an aspherical lens, and the object side surface and the image side surface of the third lens are convex surfaces; a fourth lens with positive focal power or negative focal power; and the object side surface of the fourth lens is a convex surface, the image side surface of the fourth lens is a concave surface, or both the object side surface and the image side surface are concave surfaces, or the object side surface is a concave surface, and the image side surface is a convex surface. According to the invention, the projection system has the advantages of large field of view, large aperture and miniaturization.

Description

Technical Field

[0001] The present invention relates to the technical field of imaging lenses, and in particular to a projection system. Background Art

[0002] In recent years, with the rapid development of augmented reality (AR) and virtual reality (VR), AR glasses and VR headsets have become increasingly popular. This has led to higher demands on the optical and mechanical systems used in these portable products in terms of size, weight, and image quality. Currently, the projection lenses used in AR glasses and other products on the market generally use spherical or aspherical optical systems with four or more elements. While these systems offer good imaging, the optical and mechanical systems are bulky and heavy, making them difficult to meet the demands of ever-shrinking and lightweight smart glasses. Summary of the Invention

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

[0004] In order to achieve the above object, the present invention is implemented through the following technical solutions: A projection system with five lenses, from the exit pupil side to the image source side along the optical axis, is as follows: Aperture; a first lens having positive or negative optical power, wherein the first lens is a spherical lens, and the object-side surface of the first lens is convex and the image-side surface is concave, or the object-side surface is concave and the image-side surface is convex; a second lens having positive or negative refractive power, wherein the second lens is a spherical lens, and the object-side surface of the second lens is concave and the image-side surface is convex, or both the object-side surface and the image-side surface are concave, or both the object-side surface and the image-side surface are convex; a third lens having positive optical power, wherein the third lens is a spherical lens or an aspherical lens, and both the object-side surface and the image-side surface of the third lens are convex; a fourth lens having positive or negative power; the fourth lens being a spherical or aspherical lens, the object-side surface of the fourth lens being convex and the image-side surface being concave, or both the object-side surface and the image-side surface being concave, or the object-side surface being concave and the image-side surface being convex; The total optical length TTL and the effective focal length f of the projection system satisfy the following: TTL / f<1.73.

[0005] According to one 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.

[0006] According to one 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.

[0007] According to one 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.

[0008] According to one aspect of the above technical solution, the total optical length TTL of the projection system, the air gap T12 between the first lens and the second lens on the optical axis, and the air gap T23 between the second lens and the third lens on the optical axis satisfy 2 <TTL*(T12+T23)<10。

[0009] According to one aspect of the above technical solution, the curvature radius R1 of the first lens close to the exit pupil side and the effective focal length f of the projection system meet the following conditions: -0.7 <R1 / f<0.7。

[0010] According to one 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: <F2 / f<15。

[0011] Compared with the prior art, the present invention has the following beneficial effects: The projection system of the present application achieves the advantages of a large field of view, a large aperture, and miniaturization by reasonably matching the lens shapes and optical power combinations of each lens.

[0012] Additional aspects and advantages of the present invention will be given in part in the description which follows and in part will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of the projection system in Example 1 of the present invention; Figure 2 The astigmatism curve (left) and distortion curve (right) of the projection system in Example 1 of the present invention are shown; Figure 3 Schematic diagram of the structure of the projection system in Example 2 of the present invention; Figure 4 The astigmatism curve (left) and distortion curve (right) of the projection system in Example 2 of the present invention are shown; Figure 5 Schematic diagram of the structure of the projection system in Example 3 of the present invention; Figure 61. The astigmatism curve (left) and distortion curve (right) of the projection system in Example 3 of the present invention; Figure 7 Schematic diagram of the structure of the projection system in Example 4 of the present invention; Figure 8 1. The astigmatism curve (left) and distortion curve (right) of the projection system in Example 4 of the present invention; The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0014] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0015] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0016] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0017] The present invention provides a projection system, which comprises five lenses, which are arranged in order from the exit pupil side to the image source side along the optical axis: Aperture; a first lens having positive or negative optical power, wherein the first lens is a spherical lens, and the object-side surface of the first lens is convex and the image-side surface is concave, or the object-side surface is concave and the image-side surface is convex; a second lens having positive or negative refractive power, wherein the second lens is a spherical lens, and the object-side surface of the second lens is concave and the image-side surface is convex, or both the object-side surface and the image-side surface are concave, or both the object-side surface and the image-side surface are convex; a third lens having positive optical power, wherein the third lens is a spherical lens or an aspherical lens, and both the object-side surface and the image-side surface of the third lens are convex; a fourth lens having positive or negative power; the fourth lens being a spherical or aspherical lens, the object-side surface of the fourth lens being convex and the image-side surface being concave, or both the object-side surface and the image-side surface being concave, or the object-side surface being concave and the image-side surface being convex; In some embodiments, the projection system's total optical length (TTL) and effective focal length (f) satisfy the following relationship: TTL / f < 1.73. Meeting this range allows the projection system to have a short overall length, and the projection lens can be reduced in size to < 0.4cc, resulting in a corresponding reduction in weight. Application of this system in augmented reality glasses can enhance wearer comfort and has broad application prospects.

[0018] In some embodiments, the projection system's maximum field of view (FOV) and the projection system's total optical length (TTL) satisfy the following relationship: FOV / TTL < 2.8. Because the projection lens is connected to the optical waveguide, conventional optical waveguides can only receive parallel light at relatively small angles. Therefore, the FOV in this application is always < 40°, ensuring that the projected image can be smoothly transmitted into the optical waveguide. Satisfying this relationship allows the projection system to maintain a relatively small FOV while maintaining a relatively short overall length and compact size.

[0019] In some embodiments, the combined effective focal length f12 of the first and second lenses and the combined effective focal length f34 of the third and fourth lenses satisfy the relationship: -2.2 < f12 / f34 < 1.8. Ensuring that the projection system satisfies this relationship helps reduce the design sensitivity of the projection system, allowing for optimal configuration of the refractive power of each lens in the projection system and improving the imaging quality of the optical system. Furthermore, it helps reduce the angle at which light exits the optical system after being refracted by the lens assembly, thereby reducing the angle of incidence of light entering the image-side photosensitive element of the optical system, improving the photosensitivity of the photosensitive element and enhancing the imaging quality of the optical system.

[0020] 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 meeting these limits, the outer diameter of the first lens and the radius of curvature of the image-source-side surface of the second lens of the projection lens are appropriately configured to minimize the overall lens dimensions and achieve lightweighting.

[0021] In some embodiments, the total optical length TTL of the projection system, the air gap T12 between the first lens and the second lens on the optical axis, and the air gap T23 between the second lens and the third lens on the optical axis satisfy 2 < TTL * (T12 + T23) < 10. Meeting the above range and reasonably setting the air gap between the first lens and the second lens on the optical axis and the air gap between the second lens and the third lens on the optical axis is beneficial to reducing the sensitivity of the lens and improving the yield rate of lens production and assembly. The comprehensive control of the above conditional formula enables the projection lens to meet the small volume design goal while enhancing the market competitiveness of the lens.

[0022] In some embodiments, the radius of curvature R1 of the side of the first lens close to the exit pupil and the effective focal length f of the projection system satisfy: -0.7 < R1 / f < 0.7. The larger R1 is, the lower the sensitivity is, and the higher the yield rate during actual production and assembly. The smaller R1 is, the stronger the ability of the first lens to converge light rays, the shorter the focal length, and it is more conducive to compressing the total length of the system. Meeting the above range and achieving a reasonable configuration of the ratio of R1 / f can ensure the actual assembly yield rate while reducing the lens volume.

[0023] In some embodiments, the effective focal length F2 of the second lens and the effective focal length f of the projection system satisfy: -1 < F2 / f < 15. By making the projection system meet the above relational formula, it is beneficial for the refractive power of the second lens in the optical system to be properly coordinated, the surface shape design of the second lens to be simpler and more flexible, reducing aberration, and simplifying the overall aberration correction and imaging quality balance of the optical system.

[0024] The present invention will be further described in multiple embodiments below. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection system are somewhat different. For specific differences, refer to the parameter tables of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following embodiments. Any other changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0025] Embodiment 1 Please refer to Figure 1 , which shows a schematic structural diagram of the projection system provided in Embodiment 1 of the present invention. Along the optical axis from the exit pupil side to the image source side, they are in sequence: Aperture ST0; A first lens L1 with positive optical power, the first lens is a spherical lens, the object side S1 of the first lens is a convex surface, and the image side S2 is a concave surface; A second lens L2 with positive optical power, the second lens is a spherical lens, the object side S3 of the second lens is a concave surface, and the image side S4 is a convex surface; a third lens L3 having positive refractive power, wherein the third lens is a spherical lens, and both the object-side surface S5 and the image-side surface S6 of the third lens are convex; The fourth lens L4 has negative optical power; the fourth lens is an aspherical lens, the object-side surface S7 of the fourth lens is concave, and the image-side surface S8 is convex.

[0026] Prism L5; The relevant parameters of each lens in the projection system in Example 1 are shown in Table 1-1, where the units of curvature radius and thickness are both millimeters (mm).

[0027] Table 1-1

[0028] The surface parameters of the aspheric lens of the projection system in Example 1 are shown in Table 1-2.

[0029] Table 1-2

[0030] In this embodiment, according to Figure 2 It can be seen that the projection system provided in the first embodiment can achieve good imaging quality.

[0031] Example 2 See also Figure 3 , which is a schematic diagram of the structure of the projection system provided in Example 3 of the present invention, is shown in FIG. , from the exit pupil side to the image source side along the optical axis: Aperture ST0; a first lens L1 having positive refractive power, wherein the first lens is a spherical lens, the object-side surface S1 of the first lens is convex, and the image-side surface S2 of the first lens is concave; a second lens L2 having negative optical power, wherein the second lens is a spherical lens, the object-side surface S3 of the second lens is concave, and the image-side surface S4 of the second lens is convex; a third lens L3 having positive refractive power, wherein the third lens is a spherical lens, and both the object-side surface S5 and the image-side surface S6 of the third lens are convex; a fourth lens L4 having positive refractive power; the fourth lens is an aspherical lens, the object side surface S7 of the fourth lens is concave, and the image side surface S8 is concave; Prism L5.

[0032] The relevant parameters of each lens in the projection system in Example 2 are shown in Table 2-1, where the units of curvature radius and thickness are both millimeters (mm).

[0033] Table 2-1

[0034] The surface parameters of the aspheric lens of the projection system in Example 2 are shown in Table 2-2.

[0035] Table 2-2

[0036] In this embodiment, according to Figure 4 It can be seen that the projection system provided in Example 2 can achieve good imaging quality.

[0037] Example 3 See also Figure 5 , which is a schematic diagram of the structure of the projection system provided in Example 3 of the present invention, is shown in FIG. , from the exit pupil side to the image source side along the optical axis: Aperture ST0; a first lens L1 having positive refractive power, wherein the first lens is a spherical lens, the object-side surface S1 of the first lens is convex, and the image-side surface S2 of the first lens is concave; a second lens L2 having positive refractive power, the second lens being a spherical lens, the object-side surface S3 of the second lens being concave, and the image-side surface S4 of the second lens being concave; a third lens L3 having positive refractive power, wherein the third lens is a spherical lens, and both the object-side surface S5 and the image-side surface S6 of the third lens are convex; a fourth lens L4 having negative optical power; the fourth lens is an aspherical lens, the object-side surface S7 of the fourth lens is convex, and the image-side surface S8 is concave; Prism L5.

[0038] The relevant parameters of each lens in the projection system in Example 3 are shown in Table 3-1, where the units of curvature radius and thickness are both millimeters (mm).

[0039] Table 3-1

[0040] The surface parameters of the aspheric lens of the projection system in Example 3 are shown in Table 3-2.

[0041] Table 3-2

[0042] In this embodiment, according to Figure 6 It can be seen that the projection system provided in Example 3 can achieve good imaging quality.

[0043] Example 4 See also Figure 7 , which is a schematic diagram of the structure of the projection system provided in Example 4 of the present invention, is shown in FIG. , from the exit pupil side to the image source side along the optical axis: Aperture ST0; a first lens L1 having positive refractive power, wherein the first lens is a spherical lens, the object-side surface S1 of the first lens is concave, and the image-side surface S2 of the first lens is convex; a second lens L2 having positive refractive power, wherein the second lens is a spherical lens, and the object-side surface S3 and the image-side surface S4 of the second lens are convex; a third lens L3 having positive refractive power, wherein the third lens is a spherical lens, and both the object-side surface S5 and the image-side surface S6 of the third lens are convex; a fourth lens L4 having negative optical power; the fourth lens is an aspherical lens, the object-side surface S7 of the fourth lens is convex, and the image-side surface S8 is concave; Prism L5.

[0044] The relevant parameters of each lens in the projection system in Example 4 are shown in Table 4-1, where the units of curvature radius and thickness are both millimeters (mm).

[0045] Table 4-1

[0046] The surface parameters of the aspheric lens of the projection system in Example 4 are shown in Table 4-2.

[0047] Table 4-2

[0048] In this embodiment, according to Figure 8 It can be seen that the projection system provided in Example 4 can achieve good imaging quality.

[0049] Please refer to Table 5, which shows the optical characteristics of the projection systems provided in the above four embodiments, including the relevant values ​​corresponding to each of the above expressions.

[0050] Table 5

[0051] In summary, the projection system in the present application achieves the advantages of a large field of view, a large aperture, and miniaturization by reasonably matching the lens shapes and optical focal lengths of the lenses.

[0052] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0053] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A projection system, characterized in that: There are five lenses in total, and they are as follows from the exit pupil side to the image source side along the optical axis: Aperture; a first lens having positive or negative optical power, wherein the first lens is a spherical lens, and the object-side surface of the first lens is convex and the image-side surface is concave, or the object-side surface is concave and the image-side surface is convex; a second lens having positive or negative refractive power, wherein the second lens is a spherical lens, and the object-side surface of the second lens is concave and the image-side surface is convex, or both the object-side surface and the image-side surface are concave, or both the object-side surface and the image-side surface are convex; a third lens having positive optical power, wherein the third lens is a spherical lens or an aspherical lens, and both the object-side surface and the image-side surface of the third lens are convex; a fourth lens having positive or negative power; the fourth lens being a spherical or aspherical lens, the object-side surface of the fourth lens being convex and the image-side surface being concave, or both the object-side surface and the image-side surface being concave, or the object-side surface being concave and the image-side surface being convex; The total optical length TTL and the effective focal length f of the projection system satisfy the following: TTL / f<1.

73.

2. The projection system according to claim 1, wherein: The maximum field of view (FOV) of the projection system and the total optical length (TTL) of the projection system satisfy the following conditions: FOV / TTL<2.

8.

3. The projection system according to claim 1, wherein: 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 the following: -2.2<f12 / f34<1.

8.

4. The projection system according to claim 1, wherein: 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.

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

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