Projection lens and AR projection device

Abstract

The utility model provides a projection lens and an AR projection device, and the projection lens comprises two lenses which sequentially comprise a first lens with positive focal power from a projection surface to an image source surface along an optical axis, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with negative focal power and a fifth lens with positive focal power from the projection surface to the image source surface, the second lens has negative focal power and is an aspheric lens; an image source; wherein one side, close to or far away from the image source, of the first lens is provided with a diaphragm, and the total optical length TTL of the projection lens and the focal length f of the projection lens meet the following condition: TTL / flt, and 1.2, the projection lens is small in size and light in weight, the optical system comprises two lenses, the total length of the lenses is small, the size is small, and the number of the lenses is reduced, so that the light weight of an optical machine is also facilitated.

Description

Technical Field

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

[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 engine systems in this type of portable products in terms of volume, weight, image quality, etc.

[0003] Currently, the projection lenses used in products such as augmented reality glasses basically adopt a spherical or aspherical optical system with four or more lenses. Although the imaging effect is good, the optical engine has a large volume and a high overall weight, making it difficult to meet the continuous miniaturization and lightweight of smart glasses. Summary of the Utility Model

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

[0005] On the one hand, the present utility model provides the following technical solution. A projection lens, which has a total of two lenses, and successively includes along the optical axis from the projection surface to the image source surface:

[0006] A first lens with positive optical power, its projection side is convex, and its image source side is concave;

[0007] A second lens with negative optical power, which is an aspherical lens;

[0008] An image source;

[0009] Wherein, a diaphragm is arranged on one side of the first lens close to or away from the image source, and the total optical length TTL of the projection lens and the focal length f of the projection lens satisfy: TTL / f < 1.2.

[0010] Compared with the prior art, the beneficial effect of the present utility model is that through the setting of the two lenses of the projection lens and the setting that the total optical length TTL of the projection lens and the focal length f of the projection lens satisfy: TTL / f < 1.2, a micro projection lens with a small volume and a light weight is obtained. This optical system includes two lenses, has a short total lens length and a small volume, and the reduction of the number of lenses is also beneficial to the lightweight of the optical engine.

[0011] Furthermore, the field of view FOV of the projection lens satisfies: 30° < FOV < 37°, and the effective focal length EFL of the projection lens satisfies: 4mm < EFL < 6mm.

[0012] Further, the focal length f of the projection lens and the f-number fno of the projection lens satisfy: 2 < f / fno < 4.

[0013] Further, the total optical length TTL of the projection lens and the maximum projection field of view FOV of the projection lens satisfy: FOV / TTL < 7.

[0014] Further, the focal length f1 of the first lens and the focal length f of the projection lens satisfy: f1 / f < 1.

[0015] Further, the radius of curvature R1 of the near-projection side of the first lens and the focal length f of the projection lens satisfy: 0.3 < R1 / f < 0.6.

[0016] Further, the total optical length TTL of the projection lens satisfies: 4.9 mm < TTL < 5.3 mm, and the f-number FNO of the projection lens satisfies: 1.7 < FNO < 2.5.

[0017] According to another aspect of the present invention, an AR projection device is further provided, and the AR projection device includes the above-mentioned projection lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It shows a schematic structural diagram of the projection lens according to Embodiment 1 of the present invention;

[0019] Figure 2 It shows the field curvature and distortion curve diagrams of the projection lens according to Embodiment 1 of the present invention;

[0020] Figure 3 It shows a schematic structural diagram of the projection lens according to Embodiment 2 of the present invention;

[0021] Figure 4 It shows the field curvature and distortion curve diagrams of the projection lens according to Embodiment 2 of the present invention;

[0022] Figure 5 It shows a schematic structural diagram of the projection lens according to Embodiment 3 of the present invention;

[0023] Figure 6 It shows the field curvature and distortion curve diagrams of the projection lens according to Embodiment 3 of the present invention;

[0024] Figure 7 It shows a schematic structural diagram of the projection lens according to Embodiment 4 of the present invention;

[0025] Figure 8 It shows the field curvature and distortion curve diagrams of the projection lens according to Embodiment 4 of the present invention.

[0026] The following specific embodiments will further illustrate the present utility model in conjunction with the above-mentioned drawings. Specific Embodiments

[0027] 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.

[0028] 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 feature. 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.

[0029] In the drawings, for the sake of convenience of illustration, the thickness, size, and shape of the lens 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 only examples and are not drawn strictly to scale.

[0030] In this article, 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 plane is called the projection side of the lens, and the surface of each lens closest to the image source plane is called the image source side of the lens.

[0031] It should also be understood that the terms "comprises", "comprising", "has", "including" and / or "including having", when used in this specification, indicate 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. In addition, 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. In addition, when describing the embodiments of the present application, the use of "may" means "one or more embodiments of the present application". And the term "exemplary" is intended to refer to an example or illustration.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used herein shall 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.

[0033] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the accompanying drawings and in combination with the embodiments.

[0034] The projection lens according to the embodiment of this application includes a Micro LED image source, a projection lens group. The light emitted by the image source passes through the projection lens group and exits from the exit pupil into the optical waveguide sheet. Finally, the transmitted image and the real external environment enter the human eye simultaneously, achieving the purpose of not delaying the observation of the external environment while seeing the information image.

[0035] Among them, the projection lens group successively includes: a first lens, a second lens, and an image source along the optical axis from the exit pupil side (projection plane) to the image source side (image source plane).

[0036] In some embodiments, a diaphragm; there is exactly one diaphragm, which can be located in front of or behind the first lens.

[0037] In some embodiments, the first lens has a positive focal power; it can be spherical or aspherical. Its projection side is convex, and its image source side is concave.

[0038] In some embodiments, the second lens has a negative focal power; both surfaces are aspherical. Its projection side and its image source side can be concave or convex. Among them, the concave and convex surfaces are the concavity and convexity at the optical axis.

[0039] In some embodiments, an image source.

[0040] In some embodiments, a diaphragm is provided on one side of the first lens close to or far from the image source. The total optical length TTL of the projection lens and the focal length f of the projection lens satisfy: TTL / f < 1.2. Meeting the above relational expression enables this optical system to have the advantage of a short total length. The volume of this 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.

[0041] In some embodiments, the field of view FOV of the projection lens satisfies: 30° < FOV < 37°, and the effective focal length EFL of the projection lens satisfies: 4 mm < EFL < 6 mm.

[0042] In some embodiments, the focal length f of the projection lens and the f-number fno of the projection lens satisfy: 2 < f / fno < 4. Satisfying the above relational expression can ensure that a sufficiently wide light beam enters the waveguide plate at the exit pupil, avoiding the problem of insufficient illuminance.

[0043] In some embodiments, the total optical length TTL of the projection lens and the maximum projection field of view FOV of the projection lens satisfy: FOV / TTL < 7. Since the projection lens is connected to the waveguide plate, and currently available waveguide plates on the market can only receive parallel light with a relatively small angle, the FOV in the embodiments of this patent is all < 40°, ensuring that the projected image can smoothly enter the waveguide plate for transmission. Satisfying the above relational expression can make the system have a shorter total length and a smaller volume while having a smaller FOV.

[0044] In some embodiments, the focal length f1 of the first lens and the focal length f of the projection lens satisfy: f1 / f < 1. Reasonably configuring the focal length of the first lens is beneficial to compressing the total optical length and further reducing the volume.

[0045] In some embodiments, the radius of curvature R1 on the near-projection side of the first lens and the focal length f of the projection lens satisfy: 0.3 < R1 / f < 0.6. The larger R1 is, the lower the sensitivity, and the higher the yield during actual production and assembly. The smaller R1 is, the stronger the ability of the first lens to converge light, the shorter the focal length, and it is more conducive to compressing the total optical length of the system. Reasonably configuring the ratio of R1 / f can ensure the actual assembly yield while reducing the lens volume.

[0046] In some embodiments, the total optical length TTL of the projection lens satisfies: 4.9 mm < TTL < 5.3 mm, and the f-number FNO of the projection lens satisfies: 1.7 < FNO < 2.5.

[0047] It should be noted that the first lens converges light, shortens the total optical length of the optical system, and reduces the lens volume; the second lens balances aberration and distortion to ensure good image quality.

[0048] The following further describes the utility model through 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 preferred embodiments of the present invention, but the embodiments of the present utility model are not limited only by the following embodiments. Any 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 utility model.

[0049] Embodiment 1

[0050] Please refer to Figures 1 to 2As shown, a projection lens in Embodiment 1 of the present utility model includes, along the optical axis from the projection plane to the image source plane: a first lens L1, a diaphragm ST, and a second lens L2.

[0051] The first lens L1 with positive optical power has a convex surface on its projection side 2 and a concave surface on its image source side 3.

[0052] A diaphragm ST with its side surface 4.

[0053] The second lens L2 with positive optical power has a concave surface on its projection side 5 and a convex surface on its image source side 6.

[0054] Among them, the following relationship is satisfied between the overall optical length 5 of the projection lens and the focal length 5.436 of the projection lens: 5 / 5.436 = 0.919794.

[0055] Among them, the following relationship is satisfied between the focal length 5.436 of the projection lens and the f-number 2.4 of the projection lens: 5.436 / 2.4 = 2.265.

[0056] Among them, the usage field of view angle of the projection lens is 30.94 deg, and the effective focal length of the projection lens is 5.436 mm.

[0057] Among them, the following relationship is satisfied between the overall optical length 30.94 of the projection lens and the maximum projection field of view angle 5 of the projection lens: 30.94 / 5 = 6.188.

[0058] The following relationship is satisfied between the focal length 4.74 of the first lens and the focal length 5.436 of the projection lens: 4.74 / 5.436 = 0.872.

[0059] Among them, the following relationship is satisfied between the radius of curvature 2.114 near the projection side of the first lens and the focal length 5.436 of the projection lens: 2.114 / 5.436 = 0.389.

[0060] 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 thickness are both millimeters (mm).

[0061]

[0062] Table 1

[0063] The following Table 2 gives the high-order term coefficients A4, A6, A8 and the conic coefficient values for each aspherical mirror surface that can be used in Embodiment 1.

[0064]

[0065] Table 2

[0066] In this embodiment, the field curvature curve graph and distortion curve graph of the projection lens are as shown in Figure 2 shown. According to Figure 2 it can be known that the projection system given in Embodiment 1 can achieve good imaging quality.

[0067] Embodiment 2

[0068] Please refer to Figures 3 to 4 shown. A projection lens in Embodiment 2 of the present utility model, the projection lens sequentially includes along the optical axis from the projection surface to the image source surface: a first lens L1, a diaphragm ST, and a second lens L2.

[0069] The first lens L1 with positive optical power, its projection side 2 is a convex surface, and its image source side 3 is a concave surface;

[0070] A diaphragm ST, its side surface 4;

[0071] The second lens L2 with positive optical power, its projection side 5 is a concave surface, and its image source side 6 is a convex surface.

[0072] 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).

[0073]

[0074] Table 3

[0075] The following Table 4 gives the higher-order term coefficients A4, A6, A8, A10, A12, A14, A16 of each aspherical mirror surface in Embodiment 1, and the conic coefficient values.

[0076]

[0077] Table 4

[0078] In this embodiment, the field curvature curve graph and distortion curve graph of the projection lens are as shown in Figure 4 shown. According to Figure 4 it can be known that the projection system given in Embodiment 2 can achieve good imaging quality.

[0079] Embodiment 3

[0080] 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 surface to the image source surface: a first lens L1, a diaphragm ST, and a second lens L2.

[0081] The first lens L1 with positive optical power, its projection side 2 is a convex surface, and its image source side 3 is a concave surface;

[0082] A diaphragm ST, its side surface 4;

[0083] The second lens L2 with positive optical power, its projection side 5 is a convex surface, and its image source side 6 is a convex-concave surface.

[0084] The relevant parameters of each lens in the projection lens of Embodiment 3 are shown in Table 5, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0085]

[0086] Table 5

[0087] The following Table 6 gives the higher-order term coefficients A4, A6, A8, A10, A12 and the conic coefficient values of each aspherical mirror surface that can be used in Embodiment 1.

[0088]

[0089] Table 6

[0090] 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 3 can achieve good imaging quality.

[0091] Embodiment 4

[0092] Please refer to Figures 7 to 8 as shown, a projection lens in Embodiment 4 of the present utility model, 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, and a second lens L2.

[0093] The first lens L1 with positive optical power, its projection side 2 is a convex surface, and its image source side 3 is a concave surface;

[0094] A diaphragm ST, its side surface 4;

[0095] The second lens L2 with positive optical power, its projection side 5 is a concave surface, and its image source side 6 is a convex surface.

[0096] The relevant parameters of each lens in the projection lens of Embodiment 4 are shown in Table 7, where the units of the radius of curvature and the thickness are both millimeters (mm).

[0097]

[0098] Table 7

[0099] The following Table 8 gives the higher-order term coefficients A4, A6, A8, A10, A12 and the conic coefficient values of each aspherical mirror surface that can be used in Embodiment 4.

[0100]

[0101] Table 8

[0102] In this embodiment, the field curvature curve and distortion curve of the projection lens are as shown in Figure 8 . According to Figure 8 , it can be seen that the projection system given in Embodiment 4 can achieve good imaging quality.

[0103] Please refer to Tables 9 to 15, which show the optical characteristics corresponding to the projection lenses provided in the above four embodiments, including the focal length f of the projection lens, the f-number fno of the projection lens, the total optical length TTL of the projection lens, the maximum projection field of view FOV of the projection lens, the focal length f1 of the first lens, the focal length of the projection lens, the curvature radius R1 of the first lens on the near-projection side, and the relevant numerical values corresponding to each of the foregoing conditional expressions. And the positive and negative optical powers of the two lenses, and whether the projection side and the image source side are convex or concave.

[0104] TTL / f < 1.2 First Embodiment 5 / 5.436 0.91 Second Embodiment 5 / 5.482 0.91 Third Embodiment 5.2 / 4.641 1.12 Fourth Embodiment 5.1 / 5.514 0.92

[0105] Table 9

[0106] 2 < f / fno < 4 First Embodiment 5.436 / 2.4 2.265 Second Embodiment 5.482 / 1.8 3.046 Third Embodiment 4.641 / 2.2 2.110 Fourth Embodiment 5.514 / 2.0 2.757

[0107] Table 10

[0108] fov / TTL < 7 First Embodiment 30.94 / 5 6.188 Second Embodiment 30.94 / 5 6.188 Third Embodiment 36.1 / 5.2 6.942 Fourth Embodiment 30.9 / 5.1 6.059

[0109] Table 11

[0110] f1 / f < 1 First Embodiment 4.74 / 5.436 0.872 Second Embodiment 3.95 / 5.482 0.721 Third Embodiment 4.6 / 4.641 0.991 Fourth Embodiment 4.05 / 5.514 0.734

[0111] Table 12

[0112] 0.3 < R1 / f < 0.6 First Embodiment 2.114 / 5.436 0.389 Second Embodiment 1.932 / 5.482 0.352 Third Embodiment 2.457 / 4.641 0.529 Fourth Embodiment 2.025 / 5.514 0.367

[0113] Table 13

[0114] First Lens Second Lens First Embodiment Positive Negative Second Embodiment Positive Negative Third Embodiment Positive Negative Fourth Embodiment Positive Negative

[0115] Table 14

[0116]

[0117] Table 15

[0118] In summary, for the projection lens in the above embodiments of the present utility model, by setting the two lenses of the projection lens and making the total optical length TTL of the projection lens and the focal length f of the projection lens satisfy: TTL / f < 1.2, a micro projection lens with a small volume and light weight is obtained. This optical system includes two lenses, has a short total lens length and a small volume, and the reduction in the number of lenses is also beneficial to the light weight of the optical engine.

[0119] The present utility model further provides an AR projection device, and the AR projection device includes the above-mentioned projection lens. Such an arrangement enables the overall size of the AR projection device to be reduced, which is beneficial for applications in miniaturized or head-mounted devices, realizing miniaturization while ensuring the quality of the projection screen.

[0120] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" 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 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 any one or more embodiments or examples in a suitable manner.

[0121] The above-described embodiments merely represent several implementation manners of the present utility model, and 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 shall be subject to the appended claims.

Claims

1. A projection lens, characterized in that, There are two lenses in total, which successively include, along the optical axis from the projection plane to the image source plane: A first lens with a positive optical power, whose projection side is convex and whose image source side is concave; A second lens with a negative optical power, which is an aspherical lens; An image source; Wherein, a diaphragm is arranged on one side of the first lens close to or far from the image source, and the relationship between the total optical length TTL of the projection lens and the focal length f of the projection lens satisfies: TTL / f < 1.

2.

2. The projection lens according to claim 1, wherein The field of view FOV of the projection lens in use satisfies: 30° < FOV < 37°, and the effective focal length EFL of the projection lens satisfies: 4mm < EFL < 6mm.

3. The projection lens according to claim 1, wherein, The relationship between the focal length f of the projection lens and the f-number fno of the projection lens satisfies: 2 < f / fno < 4.

4. The projection lens according to claim 1, characterized in that, The relationship between the total optical length TTL of the projection lens and the maximum projection field of view FOV of the projection lens satisfies: FOV / TTL < 7.

5. The projection lens according to claim 1, characterized in that, The relationship between the focal length f1 of the first lens and the focal length f of the projection lens satisfies: f1 / f < 1.

6. The projection lens according to claim 1, wherein The relationship between the radius of curvature R1 of the first lens near the projection side and the focal length f of the projection lens satisfies: 0.3 < R1 / f < 0.

6.

7. The projection lens according to claim 1, wherein The total optical length TTL of the projection lens satisfies: 4.9mm < TTL < 5.3mm, and the f-number FNO of the projection lens satisfies: 1.7 < FNO < 2.

5.

8. An AR projection device, characterized in that, The AR projection device includes the projection lens according to any one of claims 1 to 7.

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