Projection lens

Abstract

The utility model provides a projection lens, which comprises four lenses from a projection surface to an image source surface along an optical axis: a diaphragm; the projection side of the first lens is a convex surface, and the image source side of the first lens is a concave surface; the projection side of the second lens is a concave surface, and the image source side of the second lens is a convex surface or a concave surface; the projection side of the third lens is a convex surface, and the image source side of the third lens is a concave surface; the projection side of the fourth lens is a concave surface, and the image source side of the fourth lens is a convex surface; wherein the total optical length TTL of the projection lens meets the following conditions: 6.6 mmlt; tTLlt; the aperture number FNO of the projection lens meets the following conditions: 1.4 lt; fNOlt, FNOlt; 1.7, the total optical length TTL of the projection lens, the air gap T34 between the third lens and the fourth lens on the optical axis, and the air gap T23 between the second lens and the third lens on the optical axis meet the following conditions: 6lt; tTL / (T23-T34) lt; and 15, so that the projection lens is small in size and light in weight.

Description

Technical Field

[0001] The technical field of the imaging lens of the present utility model specifically relates to a projection lens. Background Art

[0002] With the rapid development of technology, the applications of projection lenses have also become diversified. The diverse application environments of lenses require the lenses to maintain stable performance and imaging quality in diverse environments. The display eyepiece is the core optical component of an AR glasses. Key indicators such as the imaging quality, weight, and size of the eyepiece directly affect the user experience and comfort when people wear AR glasses. People also have higher requirements for the optical engine systems in this type of portable products in terms of volume, weight, and image quality.

[0003] Currently, the optical engines used in products such as augmented reality glasses are large in volume and high in overall weight, making it difficult to meet the requirements of continuously shrinking and lightweight smart glasses. Summary of the Utility Model

[0004] To solve the above technical problems, the present utility model provides a projection lens to solve the problems in the above background art.

[0005] The utility model provides the following technical solution. A projection lens, which has a total of four lenses, includes, in order from the projection plane to the image source plane along the optical axis:

[0006] A diaphragm;

[0007] A first lens with positive optical power, whose projection side is convex and whose image source side is concave;

[0008] A second lens, whose projection side is concave and whose image source side is convex or concave;

[0009] A third lens with positive optical power, whose projection side is convex and whose image source side is concave;

[0010] A fourth lens with negative optical power, whose projection side is concave and whose image source side is convex;

[0011] Wherein, the overall optical length TTL of the projection lens satisfies: 6.6mm < TTL < 7mm, the f-number FNO of the projection lens satisfies: 1.4 < FNO < 1.7, and the overall optical length TTL of the projection lens, the air gap T34 between the third lens and the fourth lens on the optical axis, and the air gap T23 between the second lens and the third lens on the optical axis satisfy: 6 < TTL / (T23 - T34) < 15.

[0012] Compared with the prior art, the beneficial effects of the present utility model are as follows: by setting the total optical length TTL of the projection lens to satisfy 6.6 mm < TTL < 7 mm and the aperture number FNO of the projection lens to satisfy 1.4 < FNO < 1.7, a micro projection lens with a small volume and light weight is obtained. This optical system includes four spherical lenses, and the lens has a short total length, a small volume, a large aperture, and the reduction of the number of lenses is also beneficial to the light weight of the optical engine.

[0013] Further, the outer diameter D11 on the projection side of the first lens, the outer diameter D21 on the projection side of the second lens, the radius of curvature R22 on the image source side of the second lens, and the focal length f of the projection lens satisfy -21 < (D11 + D21) * R22 / f < 4.

[0014] Further, the maximum projection field of view FOV of the projection lens and the total optical length TTL of the projection lens satisfy FOV / TTL < 4.8.

[0015] Further, the combined focal length f12 of the first lens and the second lens and the combined focal length f34 of the third lens and the fourth lens satisfy 4.3 < |f34 / f12| < 42.

[0016] Further, the focal length f of the projection lens, the entrance pupil diameter EPD of the projection lens, and the maximum projection field of view FOV of the projection lens satisfy 4.5 < TAN(FOV / 2) / f / EPD < 7.5.

[0017] Further, the radius of curvature R11 on the projection side of the first lens at the optical axis, the thickness CT1 of the first lens on the optical axis, and the focal length f of the projection lens satisfy 20 < (R11 / CT1) * f < 25.

[0018] Further, the focal length f2 of the second lens and the focal length f of the projection lens satisfy -10 < f2 / f < 29.

[0019] Further, the radius of curvature R41 on the projection side of the third lens at the optical axis, the radius of curvature R42 on the image source side of the third lens at the optical axis, and the thickness CT4 of the fourth lens on the optical axis satisfy R41 / (R42 * CT4) ≤ 1.2.

[0020] Further, the total optical length TTL of the projection lens and the focal length f of the projection lens satisfy TTL / f < 1.2.

[0021] Further, the focal length f1 of the first lens and the focal length f of the projection lens satisfy f1 / f < 1.1. Description of the Drawings

[0022] Figure 1 It shows a schematic structural diagram of the projection lens according to Embodiment 1 of the present utility model;

[0023] Figure 2 It shows a field curvature and distortion curve graph of the projection lens according to Embodiment 1 of the present utility model;

[0024] Figure 3 It shows a schematic structural diagram of the projection lens according to Embodiment 2 of the present utility model;

[0025] Figure 4 It shows a field curvature and distortion curve graph of the projection lens according to Embodiment 2 of the present utility model;

[0026] Figure 5 It shows a schematic structural diagram of the projection lens according to Embodiment 3 of the present utility model;

[0027] Figure 6 It shows a field curvature and distortion curve graph of the projection lens according to Embodiment 3 of the present utility model;

[0028] Figure 7 It shows a schematic structural diagram of the projection lens according to Embodiment 4 of the present utility model;

[0029] Figure 8 It shows a field curvature and distortion curve graph of the projection lens according to Embodiment 4 of the present utility model.

[0030] The following specific embodiments will further illustrate the present utility model in conjunction with the above-mentioned drawings. Specific Embodiments

[0031] To better understand the present application, more detailed descriptions of various aspects of the present application will be made with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application and do not limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] It should be noted that in this specification, the expressions such as first, second, and third are only used to distinguish one feature from another feature and do not represent any limitation on the features. Therefore, without departing from the teachings of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0033] In the drawings, for the sake of clarity, the thickness, dimensions, and shape of the lenses have been slightly exaggerated. Specifically, the spherical or aspherical shapes shown in the drawings are shown by way of example. That is, the spherical or aspherical shapes are not limited to the spherical or aspherical shapes shown in the drawings. The drawings are for illustrative purposes only and are not drawn to an exact scale.

[0034] In this text, 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 defined, 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 defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the projection surface is called the projection side of the lens, and the surface of each lens closest to the image source surface is called the image source side of the lens.

[0035] It should also be understood that the terms "comprises", "comprising", "has", "including" and / or "including" when used in this specification denote the presence of the stated features, elements and / or components, but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. Further, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of listed features rather than individual elements in the list. Further, when describing embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the term "exemplary" is intended to refer to an example or illustration.

[0036] Unless otherwise defined, all terms (including 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. It should also be understood that terms (such as those defined in a common dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0037] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0038] The projection lens according to an embodiment of the present application includes a micro LED image source and a projection lens group. The light emitted by the image source passes through the projection lens group, exits from the exit pupil and enters the optical waveguide sheet, and finally the transmitted image and the real external environment enter the human eye at the same time, achieving the purpose of not delaying the observation of the external environment while seeing the information image.

[0039] Wherein, the projection lens group sequentially includes: a diaphragm, a first lens, a second lens, a third lens, and a fourth lens along the optical axis from the exit pupil side (projection surface) to the image source side (image source surface).

[0040] In some embodiments, there is one diaphragm; there is exactly one diaphragm, which may be located in front of the first lens.

[0041] In some embodiments, the first lens may have a positive optical power, with its projection side being convex and its image source side being concave.

[0042] In some embodiments, the second lens may have a positive optical power or a negative optical power, with its projection side being concave and its image source side being convex or concave. The object side (projection side) surface of the second lens is concave, which can effectively refract light rays to obtain a larger picture and meet the function of magnifying and imaging the picture of the AR projection lens.

[0043] In some embodiments, the third lens has a positive optical power, with its projection side being convex and its image source side being concave. The first lens and the third lens converge light rays, shortening the total length of the optical system and reducing the volume of the lens.

[0044] In some embodiments, the fourth lens has a negative optical power, with its projection side being concave and its image source side being convex. The imaging side (image source side) surface of the fourth lens is convex, which can effectively refract and converge light rays passing through the fourth lens.

[0045] In some embodiments, the total optical length TTL of the projection lens satisfies: 6.6 mm < TTL < 7 mm, the f-number FNO of the projection lens satisfies: 1.4 < FNO < 1.7, and the total optical length TTL of the projection lens, the air gap T34 on the optical axis between the third lens and the fourth lens, and the air gap T23 on the optical axis between the second lens and the third lens satisfy: 6 < TTL / (T23 - T34) < 15. Reasonably setting the air gap on the optical axis between the second lens and the third lens and the air gap on the optical axis between the third lens and the fourth lens is beneficial to reducing the sensitivity of the lens and improving the yield of lens production and assembly. The comprehensive control of the above conditional expressions enables the projection lens to meet the small volume design goal while enhancing the market competitiveness of the lens.

[0046] In some embodiments, the outer diameter D11 of the projection side of the first lens, the outer diameter D21 of the projection side of the second lens, the radius of curvature R22 of the image source side of the second lens, and the focal length f of the projection lens satisfy: -21 < (D11 + D21) * R22 / f < 4. Reasonably setting the outer diameter of the first lens of the projection lens and the radius of curvature of the image source side surface of the second lens achieves the goal of minimizing and lightening the overall dimensions of the lens.

[0047] In some embodiments, the following relationship is satisfied between the maximum projection field of view FOV of the projection lens and the total optical length TTL of the projection lens: FOV / TTL < 4.8. Since the projection lens is connected to the waveguide sheet, and currently available waveguide sheets on the market can only receive parallel light with a small angle, the FOV in the embodiments of this patent is all < 40°, ensuring that the projected image can smoothly enter the waveguide sheet for transmission. Satisfying the above relationship allows the system to have a shorter total length and a smaller volume while having a smaller FOV.

[0048] In some embodiments, the following relationship is satisfied between the combined focal length f12 of the first lens and the second lens and the combined focal length f34 of the third lens and the fourth lens: 4.3 < |f34 / f12| < 42. By making the optical system satisfy the above relationship, it is beneficial to reduce the design sensitivity of the optical system, reasonably configure the refractive power of each lens in the optical system, and improve the imaging quality of the optical system; at the same time, it is also beneficial to reduce the angle at which the light exits the optical system after being refracted by the lens group, thereby reducing the incident angle of the light entering the image-side photosensitive element of the optical system, improving the photosensitive performance of the photosensitive element, and enhancing the imaging quality of the optical system.

[0049] In some embodiments, the following relationship is satisfied among the focal length f of the projection lens, the entrance pupil diameter EPD of the projection lens, and the maximum projection field of view FOV of the projection lens: 4.5 < TAN(FOV / 2) / f / EPD < 7.5. Satisfying the above relationship is beneficial to the reasonable configuration of the ratio of the total optical length and the aperture number of the optical system, achieving the effect of a large aperture, and ensuring the light input and imaging quality of the optical system.

[0050] In some embodiments, the following relationship is satisfied among the radius of curvature R11 at the optical axis on the projection side of the first lens, the thickness CT1 of the first lens on the optical axis, and the focal length f of the projection lens: 20 < (R11 / CT1)*f < 25. By making the optical system satisfy the above relationship, the ratio of the radius of curvature at the optical axis of the object side of the first lens and the thickness of the first lens on the optical axis is reasonably configured, reducing the sensitivity of the first lens, and thus reducing the processing and manufacturing difficulty of the first lens.

[0051] In some embodiments, the following relationship is satisfied between the focal length f2 of the second lens and the focal length f of the projection lens: -10 < f2 / f < 29. By making the optical system satisfy the above relationship, it is beneficial for the refractive power of the second lens to be properly coordinated in the optical system (projection lens), the surface shape design of the second lens is more simple and flexible, reducing aberration, and simplifying the overall aberration correction and imaging quality balance of the optical system.

[0052] In some embodiments, the following condition is satisfied among the radius of curvature R41 at the optical axis on the projection side of the third lens, the radius of curvature R42 at the optical axis on the image source side of the third lens, and the thickness CT4 of the fourth lens on the optical axis: R41 / (R42 * CT4) ≤ 1.2. By making the optical system satisfy the above relationship, it is beneficial to control the shape of the third lens, reduce the processing difficulty of the fourth lens, comprehensively balance the spherical aberration, chromatic aberration, and field curvature of the optical system, and improve the imaging quality of the optical system.

[0053] In some embodiments, the following condition is satisfied between the overall optical length TTL of the projection lens and the focal length f of the projection lens: TTL / f < 1.2. Satisfying the above relationship enables the optical system to have the advantage of a short overall length. The volume of the projection lens can be made < 0.2 cc, and the weight is also correspondingly reduced. Applying it to augmented reality glasses can improve the comfort of the wearer and has broad application prospects.

[0054] In some embodiments, the following condition is satisfied between the focal length f1 of the first lens and the focal length f of the projection lens: f1 / f < 1.1. Reasonably configuring the focal length of the first lens is beneficial to compressing the overall system length and further reducing the volume.

[0055] It should be noted that the combination of the optical powers of the lenses in the embodiments can reduce aberrations such as astigmatism and field curvature in the optical system, improve the image quality, and at the same time make the overall system length smaller. In this application, the lens material is optical glass, which is more beneficial to the temperature drift stability of the fixed-focus lens. In this application, the image source is a Macro LED, which can emit light by itself and carry images, but is not limited thereto. The optical lens examples in the above embodiments of this application should not be construed as limitations, and this optical lens can also be applied to other fields as needed.

[0056] The utility model will be further described below with multiple embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the projection lens are partially different. For specific differences, refer to the parameter tables of each embodiment. The following embodiments are only the 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 substitution methods and are included in the protection scope of the present invention.

[0057] Embodiment 1

[0058] Please refer to Figures 1 to 2 As shown, a projection lens in Embodiment 1 of the present utility model includes, along the optical axis from the projection surface to the image source surface in sequence: a diaphragm ST, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. Among them, the projection lens further includes a protective glass G1 and an image source surface S9 that are sequentially arranged behind the fourth lens.

[0059] A first lens L1 with a positive focal power, having a convex surface on its projection side S1 and a concave surface on its image source side S2;

[0060] A second lens L2 with a positive focal power, having a concave surface on its projection side S3 and a convex surface on its image source side S4;

[0061] A third lens L3 with a positive focal power, having a convex surface on its projection side S5 and a concave surface on its image source side S6;

[0062] A fourth lens L4 with a negative focal power, having a concave surface on its projection side S7 and a convex surface on its image source side S8;

[0063] Wherein, the total optical length of the projection lens is 6.6, the air gap between the third lens and the fourth lens on the optical axis is 1.1, and the air gap between the second lens and the third lens on the optical axis is 0.633, satisfying: 6.6 / (1.1 - 0.633) = 14.1327623126338.

[0064] Wherein, the maximum projection field angle of the projection lens is 31.52, and the total optical length of the projection lens is 6.6, satisfying: 31.52 / 6.6 = 4.77575757575758.

[0065] Wherein, the combined focal length of the first lens and the second lens is -25.92, and the combined focal length of the third lens and the fourth lens is 5.77, satisfying |-25.92 / 5.77| = 4.49220103986135.

[0066] Wherein, the focal length of the projection lens is 5.21, the entrance pupil diameter of the projection lens is 3.656, and the maximum projection field angle of the projection lens is 31.5, satisfying: TAN(31.5 / 2) / 5.21 / 3.656 = 5.05286284101101.

[0067] Wherein, the radius of curvature at the optical axis of the projection side of the first lens is 3.94, the thickness of the first lens on the optical axis is 0.928, and the focal length of the projection lens is 5.21, satisfying: (3.94 / 0.928) * 5.21 = 22.1200431034483.

[0068] The focal length of the second lens is 145, and the focal length of the projection lens is 5.21, satisfying: 145 / 5.21 = 27.831094049904.

[0069] Among them, the radius of curvature at the optical axis on the projection side of the third lens is -2.44, the radius of curvature at the optical axis on the image source side of the third lens is -6.55, and the thickness of the fourth lens on the optical axis is 0.4, satisfying: |-2.44 / (-6.55 * 0.4)| = 0.931297709923664.

[0070] The total optical length of the projection lens is 6.6, and the focal length of the projection lens is 5.21, satisfying: 6.6 / 5.21 = 1.26679462571977.

[0071] The focal length of the first lens is 5.48, and the focal length of the projection lens is 5.21, satisfying: 5.48 / 5.21 = 1.05182341650672.

[0072] The relevant parameters of each lens in the projection lens in Embodiment 1 are shown in Table 1, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0073]

[0074] Table 1

[0075] In this embodiment, the field curvature curve graph and the distortion curve graph of the projection lens are as Figure 2 shown. According to Figure 2 it can be known that the projection system given in Embodiment 1 can achieve good imaging quality.

[0076] Embodiment 2

[0077] Please refer to Figures 3 to 4 shown. A projection lens in Embodiment 2 of the present invention, the projection lens sequentially includes, along the optical axis from the projection surface to the image source surface: a diaphragm ST, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. Among them, the projection lens further includes a protective glass G1 and an image source surface S9 sequentially arranged behind the fourth lens.

[0078] The first lens L1 with positive optical power, its projection side S1 is a convex surface, and its image source side S2 is a concave surface;

[0079] The second lens L2 with negative optical power, its projection side S3 is a concave surface, and its image source side S4 is a convex surface;

[0080] The third lens L3 with positive optical power, its projection side S5 is a convex surface, and its image source side S6 is a concave surface;

[0081] The fourth lens L4 with negative optical power, its projection side S7 is a concave surface, and its image source side S8 is a convex surface.

[0082] The relevant parameters of each lens in the projection lens in Embodiment 2 are shown in Table 2, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0083]

[0084] Table 2

[0085] In this embodiment, the field curvature curve graph and the distortion curve graph of the projection lens are as Figure 4 shown. According to Figure 4 it can be known that the projection system given in Embodiment 1 can achieve good imaging quality.

[0086] Embodiment 3

[0087] Please refer to Figures 5 to 6 shown. A projection lens in Embodiment 3 of the present utility model, the projection lens sequentially includes along the optical axis from the projection plane to the image source plane: a diaphragm ST, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.

[0088] The first lens L1 with positive optical power, its projection side S1 is a convex surface, and its image source side S2 is a concave surface;

[0089] The second lens L2 with negative optical power, its projection side S3 is a concave surface, and its image source side S4 is a concave surface;

[0090] The third lens L3 with positive optical power, its projection side S5 is a convex surface, and its image source side S6 is a concave surface;

[0091] The fourth lens L4 with negative optical power, its projection side S7 is a concave surface, and its image source side S8 is a convex surface.

[0092] The relevant parameters of each lens in the projection lens in Embodiment 3 are shown in Table 3, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0093]

[0094] Table 3

[0095] In this embodiment, the field curvature curve graph and the distortion curve graph of the projection lens are as Figure 6 shown. According to Figure 6 it can be known that the projection system given in Embodiment 1 can achieve good imaging quality.

[0096] Embodiment 4

[0097] Please refer to Figures 7 to 8As shown in the figure, a projection lens in Embodiment 4 of the present utility model includes, along the optical axis from the projection plane to the image source plane: a diaphragm ST, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4.

[0098] The first lens L1 with positive optical power has a convex surface on its projection side S1 and a concave surface on its image source side S2;

[0099] The second lens L2 with negative optical power has a concave surface on its projection side S3 and a convex surface on its image source side S4;

[0100] The third lens L3 with positive optical power has a convex surface on its projection side S5 and a concave surface on its image source side S6;

[0101] The fourth lens L4 with negative optical power has a concave surface on its projection side S7 and a convex surface on its image source side S8.

[0102] The relevant parameters of each lens in the projection lens in Embodiment 4 are shown in Table 4, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0103]

[0104] Table 4

[0105] In this embodiment, the field curvature curve graph and the distortion curve graph of the projection lens are as Figure 8 shown. According to Figure 8 it can be seen that the projection system given in Embodiment 4 can achieve good imaging quality.

[0106] Please refer to Tables 5 to 16, which show the optical characteristics corresponding to the projection lenses provided in the above four embodiments, including the total optical length TTL of the projection lens, the air gap T34 between the third lens and the fourth lens on the optical axis, the air gap T23 between the second lens and the third lens on the optical axis, the outer diameter D11 of the projection side of the first lens, the outer diameter D21 of the projection side of the second lens, the radius of curvature R22 of the image source side of the second lens, the focal length f of the projection lens, the maximum projection field of view FOV of the projection lens, the combined focal length f12 of the first lens and the second lens, the combined focal length f34 of the third lens and the fourth lens, the entrance pupil diameter EPD of the projection lens, the radius of curvature R11 of the projection side of the first lens at the optical axis, the thickness CT1 of the first lens on the optical axis, the focal length f2 of the second lens, the radius of curvature R41 of the projection side of the third lens at the optical axis, the radius of curvature R42 of the image source side of the third lens at the optical axis, the thickness CT4 of the fourth lens on the optical axis, and the relevant numerical values corresponding to the focal length f1 of the first lens and each of the foregoing conditional expressions. And the positive and negative optical powers of the four lenses, and whether the projection side and the image source side are convex or concave surfaces.

[0107]

[0108] Table 5

[0109]

[0110] Table 6

[0111]

[0112] Table 7

[0113]

[0114] Table 8

[0115]

[0116] Table 9

[0117]

[0118] Table 10

[0119]

[0120] Table 11

[0121]

[0122] Table 12

[0123]

[0124] Table 13

[0125]

[0126] Table 14

[0127]

[0128] Table 15

[0129]

[0130] Table 16

[0131] In summary, for the projection lens in the above embodiments of the present utility model, by setting the total optical length TTL of the projection lens to satisfy: 6.6 mm < TTL < 7 mm, and the f-number FNO of the projection lens to satisfy: 1.4 < FNO < 1.7, a micro projection lens with a small volume and light weight is obtained. This optical system includes four spherical lenses. The lens has a short total length, a small volume, a large aperture, and the reduction in the number of lenses is also beneficial to the light weight of the optical engine.

[0132] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean 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 utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0133] The above-described embodiments only represent several implementation manners of the present utility model. Their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the patent of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can still be made, and these all belong to the protection scope of the present utility model. Therefore, the protection scope of the patent of the present utility model should be subject to the appended claims.

Claims

1. A projection lens, characterized in that, There are four lenses in total, which successively include along the optical axis from the projection plane to the image source plane: A diaphragm; A first lens with positive optical power, whose projection side is convex and whose image source side is concave; A second lens, whose projection side is concave and whose image source side is convex or concave; A third lens with positive optical power, whose projection side is convex and whose image source side is concave; A fourth lens with negative optical power, whose projection side is concave and whose image source side is convex; Among them, the total optical length TTL of the projection lens satisfies: 6.6mm < TTL < 7mm, the aperture number FNO of the projection lens satisfies: 1.4 < FNO < 1.7, and the total optical length TTL of the projection lens, the air gap T34 between the third lens and the fourth lens on the optical axis, and the air gap T23 between the second lens and the third lens on the optical axis satisfy: 6 < TTL / (T23 - T34) < 15.

2. The projection lens according to claim 1, wherein The outer diameter D11 of the projection side of the first lens, the outer diameter D21 of the projection side of the second lens, the curvature radius R22 of the image source side of the second lens, and the focal length f of the projection lens satisfy: -21 < (D11 + D21)*R22 / f < 4.

3. The projection lens according to claim 1, characterized in that, The maximum projection field of view FOV of the projection lens and the total optical length TTL of the projection lens satisfy: FOV / TTL < 4.

8.

4. The projection lens according to claim 1, characterized in that, The combined focal length f12 of the first lens and the second lens and the combined focal length f34 of the third lens and the fourth lens satisfy 4.3 < |f34 / f12| < 42.

5. The projection lens according to claim 1, characterized in that, The focal length f of the projection lens, the entrance pupil diameter EPD of the projection lens, and the maximum projection field of view FOV of the projection lens satisfy: 4.5 < TAN(FOV / 2) / f / EPD < 7.

5.

6. The projection lens according to claim 1, wherein The curvature radius R11 of the projection side of the first lens at the optical axis, the thickness CT1 of the first lens on the optical axis, and the focal length f of the projection lens satisfy: 20 < (R11 / CT1)*f < 25.

7. The projection lens according to claim 1, wherein The focal length f2 of the second lens and the focal length f of the projection lens satisfy: -10 < f2 / f < 29.

8. The projection lens according to claim 1, wherein The curvature radius R41 of the projection side of the third lens at the optical axis, the curvature radius R42 of the image source side of the third lens at the optical axis, and the thickness CT4 of the fourth lens on the optical axis satisfy: R41 / (R42*CT4) ≤ 1.

2.

9. The projection lens according to claim 1, characterized in that, The total optical length TTL of the projection lens and the focal length f of the projection lens satisfy: TTL / f < 1.

2.

10. The projection lens according to claim 1, characterized in that, The focal length f1 of the first lens and the focal length f of the projection lens satisfy: f1 / f < 1.1.

Images