Projection lens

Abstract

The utility model discloses a projection lens, which is sequentially arranged from an image side to a light source side along an optical axis of the lens: a first lens which is a spherical glass lens with positive focal power; the second lens is a spherical glass lens with negative focal power; the third lens is a spherical glass lens with positive focal power; and the fourth lens is a spherical glass lens with positive focal power. According to the projection lens, four glass lenses are adopted, F # can be 1.46, high illumination, large divergence angle and small CRA are achieved, and the projection lens has high cost performance.

Description

Technical Field

[0001] The utility model relates to the field of optical lenses, and particularly to a projection lens. Background Art

[0002] With the rapid development of automotive lighting technology, technologies with low cost and high relative illuminance have gradually entered the field of automotive lighting. In recent years, with the improvement of living standards, people's demand for driving experience has also been continuously increasing, and the light projection technology has also been widely applied in the field of intelligent driving. For example, the welcome light can be installed at the bottom of the car door or under the rearview mirror to project customized patterns. However, at present, the projection lenses on the market have a large aperture, and the projected graphics are prone to vignetting, which is difficult to meet the needs of customers. Content of the Utility Model

[0003] Based on this, the purpose of the utility model is to provide a projection lens with high relative illuminance and no vignetting.

[0004] The purpose of the utility model is realized through the following technical solutions:

[0005] A projection lens, defining the surface adjacent to the left side of the lens as the image side, and the surface adjacent to the right side of the lens as the light source side. Along the optical axis of the lens, from left to right, the following are arranged in sequence:

[0006] A first lens, the first lens being a glass lens with positive optical power, the image side of the first lens being convex, and the light source side being concave;

[0007] A second lens, the second lens being a glass lens with negative optical power, the image side of the second lens being concave;

[0008] A third lens, the third lens being a glass lens with positive optical power, the image side of the third lens being convex;

[0009] A fourth lens, the fourth lens being a spherical glass lens with positive optical power, the image side of the fourth lens being convex, and the light source side being concave;

[0010] The lens further includes a diaphragm, and the diaphragm is located between the first lens and the second lens.

[0011] Further, the aperture of the lens is F#, satisfying F# ≤ 3.1;

[0012] The total focal length of the lens is f, satisfying f ≤ 35mm;

[0013] The overall optical length of the lens is TTL, satisfying TTL ≤ 57mm;

[0014] The divergence angle of the lens ≤ 40°;

[0015] The chief ray angle of the lens is CRA, and CRA < 1°.

[0016] Furthermore, the lens satisfies the following relational expressions:

[0017] 0.9 ≤ f1 / f ≤ 1.2,

[0018] -1.4 ≤ f2 / f ≤ -0.4,

[0019] 0.7 ≤ f3 / f ≤ 2,

[0020] 1 ≤ f4 / f ≤ 3.2,

[0021] IH / TTL ≥ 0.25,

[0022] TTL / f ≤ 1.8,

[0023] OBFL / TTL ≥ 0.03;

[0024] In the relational expressions, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, and IH is the full image height of the chip equipped with the lens system.

[0025] Furthermore, the focal lengths, refractive indices, and curvature radii of the first lens, second lens, third lens, fifth lens, and sixth lens respectively satisfy the following conditions:

[0026] f1 25～35 ND1 1.70～1.90 R11 12.3～22.1 R12 25.1～181.0 f2 -39～-14 ND2 1.75～1.96 R21 -28.9～-7.2 R22 -34.3～19.3 f3 23～54 ND3 1.52～1.80 R31 25.4～57.5 R32 -117.0～252.6 f4 29～96 ND4 1.75～1.90 R41 15.9～23.9 R42 13.9～2780.2

[0027] Among them, f1 is the focal length of the first lens, ND1 is the refractive index of the first lens, R11 is the image-side curvature radius of the first lens, and R12 is the light-source-side curvature radius of the first lens; f2 is the focal length of the second lens, ND2 is the refractive index of the second lens 2, R21 is the image-side curvature radius of the second lens, and R22 is the light-source-side curvature radius of the second lens; f is the focal length of the third lens, ND3 is the refractive index of the third lens, R31 is the image-side curvature radius of the third lens, and R32 is the light-source-side curvature radius of the third lens; f4 is the focal length of the fourth lens, ND4 is the refractive index of the fourth lens, R41 is the image-side curvature radius of the fourth lens, and R42 is the light-source-side curvature radius of the fourth lens;

[0028] The unit of the focal length is mm; the unit of the curvature radius is mm; the "-" sign indicates a negative direction.

[0029] The beneficial effects of the present utility model are:

[0030] The present utility model is sequentially arranged from the image side to the light source side along the lens optical axis: a first lens, which is a spherical glass lens with a positive optical power; a second lens, which is a spherical glass lens with a negative optical power; a third lens, which is a spherical glass lens with a positive optical power; and a fourth lens, which is a spherical glass lens with a positive optical power. This lens uses 4 glass lenses, and the F# can reach 1.46, improving the relative illumination, having good optical performance, and at the same time having a large divergence angle, meeting the customer's miniaturization requirements while having a good projection effect. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the optical structure of Embodiment 1 of the present utility model;

[0032] Figure 2 It is the axial chromatic aberration diagram of visible light 0.435 - 0.656μm of Embodiment 1 of the present utility model;

[0033] Figure 3 It is the relative illumination diagram of visible light 0.546μm of Embodiment 1 of the present utility model;

[0034] Figure 4 It is the field curvature of visible light 0.435 - 0.656μm of Embodiment 1 of the present utility model;

[0035] Figure 5 It is the F - Theta distortion diagram of visible light 0.435 - 0.656μm of Embodiment 1 of the present utility model;

[0036] Figure 6 It is a schematic diagram of the optical structure of Embodiment 2 of the present utility model;

[0037] Figure 7 It is the axial chromatic aberration diagram of visible light 0.435 - 0.656μm of Embodiment 2 of the present utility model;

[0038] Figure 8 It is a schematic diagram of the optical structure of Embodiment 3 of the present utility model;

[0039] Figure 9 It is the axial chromatic aberration diagram of visible light 0.435 - 0.656μm of Embodiment 3 of the present utility model;

[0040] Figure 10 It is the relative illumination diagram of visible light 0.546μm of Embodiment 3 of the present utility model;

[0041] Figure 11 It is the field curvature diagram of visible light 0.435 - 0.656μm of Embodiment 3 of the present utility model;

[0042] Figure 12This is the visible light 0.435 - 0.656μm F-Theta distortion curve graph of Embodiment 3 of the present utility model; Reference numerals: 1 - first lens; 2 - second lens; 3 - third lens; 4 - fourth lens; 5 - aperture stop. Detailed implementation manners

[0043] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. 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. The shape of the spherical or aspherical surface is not limited to the spherical or aspherical surface shown in the accompanying drawings. The accompanying drawings are only for illustration and are not drawn strictly to scale.

[0044] In the present utility model, 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; if the lens surface is not defined as convex, concave or flat, it means that the lens surface can be convex, concave or flat.

[0045] Unless otherwise defined, all terms (including technical terms and scientific terms) used in the present utility model have the same meaning as the ordinary understanding of those of ordinary skill in the technical field 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 clearly defined as such in the present utility model.

[0046] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present utility model. For better understanding and implementation, the present utility model will be described in detail below with reference to the accompanying drawings.

[0047] The present utility model provides a projection lens. Define the surface adjacent to the left side of the lens as the image side surface, and the surface adjacent to the right side of the lens as the light source surface (i.e., the projection surface). They are arranged in sequence from left to right along the optical axis of the lens:

[0048] The first lens 1, the first lens 1 is a glass lens with positive optical power. The image side surface of the first lens 1 is convex, and the light source surface is concave;

[0049] The second lens 2 is a glass lens with a negative optical power. The image side of the second lens 2 is concave;

[0050] The third lens 3 is a glass lens with a positive optical power. The image side of the third lens 3 is convex;

[0051] The fourth lens 4 is a spherical glass lens with a positive optical power. The image side of the fourth lens 4 is convex, and the light source side is concave;

[0052] The lens further includes a diaphragm 5. The diaphragm 5 is located between the first lens 1 and the second lens 2 and is close to the image side of the second lens 2.

[0053] Among them, the diameters of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are all less than 28 mm.

[0054] The image light source in the present utility model is arranged on the light source side of the fourth lens 4.

[0055] In the present utility model, in order to make the optical system present better performance, during the design process, we should reasonably select the lens materials, reasonably allocate the focal lengths of each lens, and reasonably optimize the optical system to correct the aberration of the system, and finally optimize the performance of the optical system. In the present utility model, the focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, and the total focal length of the lens is f. The ratio of the focal length of each lens to the total focal length of the system satisfies the following conditions:

[0056] 0.9 ≤ f1 / f ≤ 1.2,

[0057] -1.4 ≤ f2 / f ≤ -0.4,

[0058] 0.7 ≤ f3 / f ≤ 2,

[0059] 1 ≤ f4 / f ≤ 3.2.

[0060] In the present utility model, considering the aberration problem of the optical system, the focal lengths, refractive indices, and curvature radii of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 respectively satisfy the following conditions:

[0061] f1 25～35 ND1 1.70～1.90 R11 12.3～22.1 R12 25.1～181.0 f2 -39～-14 ND2 1.75～1.96 R21 -28.9～-7.2 R22 -34.3～19.3 f3 23～54 ND3 1.52～1.80 R31 25.4～57.5 R32 -117.0～252.6 f4 29～96 ND4 1.75～1.90 R41 15.9～23.9 R42 13.9～2780.2

[0062] Among them, f1 is the focal length of the first lens 1, ND1 is the refractive index of the first lens 1, R11 is the curvature radius of the image side of the first lens 1, and R12 is the curvature radius of the light source side of the first lens 1;

[0063] f2 is the focal length of the second lens 2, ND2 is the refractive index of the second lens 2, R21 is the image-side curvature radius of the second lens 2, and R22 is the light-source-side curvature radius of the second lens 2;

[0064] f3 is the focal length of the third lens 3, ND3 is the refractive index of the third lens 3, R31 is the image-side curvature radius of the third lens 3, and R32 is the light-source-side curvature radius of the third lens 3;

[0065] f4 is the focal length of the fourth lens 4, ND4 is the refractive index of the fourth lens 4, R41 is the image-side curvature radius of the fourth lens 4, and R42 is the light-source-side curvature radius of the fourth lens 4;

[0066] The unit of the focal length is mm; the unit of the curvature radius is mm; the "-" sign indicates a negative direction.

[0067] In the present utility model, f is the total focal length of the lens, TTL is the optical total length of the lens, OBFL is the optical back focal length of the lens, and the optical back focal length of the lens is the distance from the light-source surface to the nearest point of the fourth lens 4; IH is the full image height of the chip matched with the lens system; they satisfy the following relationships:

[0068] IH / TTL≥0.25,

[0069] TTL / f≤2,

[0070] OBFL / TTL≥0.15;

[0071] In the present utility model, the aperture of the lens is F#, satisfying F#≤3.1; the focal length of the lens is f, satisfying f≤35mm; the optical total length of the lens is TTL, satisfying TTL≤57mm, the divergence angle of the lens≤40°, and the chief ray angle of the lens is CRA<1°.

[0072] The following gives specific embodiments according to the above settings of the present utility model to specifically illustrate the projection lens according to the present utility model. The main element symbols are shown in Table 1:

[0073] Table 1

[0074] S1 First lens image side S6 Third lens image side S2 First lens light source side S7 Third lens light source side S3 Diaphragm S8 Fourth lens image side S4 Second lens image side S9 Fourth lens light source side S5 Second lens light source side S10 Imaging light source

[0075] The data summary of the specific embodiments is shown in Table 2 below:

[0076] Table 2

[0077]

[0078]

[0079] Example 1

[0080] Refer toFigure 1 As shown, it is a schematic diagram of the optical structure of Embodiment 1. In this embodiment, the total focal length f of the lens is 28.2 mm, the aperture value F# is 3.1, the full image height IH is 14.9 mm, the field of view angle DFOV is 30°, and the total optical length TTL of the lens is 47 mm.

[0081] In this embodiment, the radius of curvature (unit: mm), the central thickness d (unit: mm), the refractive index (ND), and the Abbe number (VD) of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are shown in Table 3.

[0082] Table 3

[0083] Surface number Radius of curvature R Central thickness d Refractive index ND Abbe number VD S1 12.374 9.0138 1.7 55.5 S2 25.0847 5.2259 S3 Infinity 2.4471 S4 -7.3313 7.6307 1.95 17.9 S5 -13.8417 2.0741 S6 25.4025 7.4999 1.52 64.2 S7 252.5313 0.1999 S8 23.8821 8.8025 1.8 46.6 S9 2780.126 4.1816 S10 Infinity

[0084] In Table 3, the radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side, where "Infinity" represents that the surface is a plane; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the light deflection ability of the current lens material, and the Abbe number represents the chromatic dispersion characteristics of the current lens material.

[0085] Please refer to Figure 2 , which shows the axial chromatic aberration diagram of the lens in this embodiment. The horizontal axis represents the intersection position of the light ray and the optical axis (unit: mm), and the vertical axis represents different apertures of the lens. From Figure 2 , it can be seen that the axial chromatic aberration is about 0.25 mm.

[0086] Refer to Figure 3 As shown, the relative illuminance of the lens at the maximum field of view is greater than 85%, and the light input is sufficient, ensuring that even when the lens is used in a relatively dim environment, there will be no vignetting in the actual captured image.

[0087] Please refer to Figure 4 and Figure 5 , which are the field curvature and F-Tan(Theta) distortion diagrams of the lens in this embodiment respectively. In the field curvature diagram, the horizontal axis represents the field curvature amount (unit: mm), and the vertical axis represents the semi-field angle (unit: °). From Figure 4 , it can be seen that the change in the field curvature amount is less than 0.5 mm. In the distortion Figure 5 , the horizontal axis represents the F-Theta distortion (unit: %), and the vertical axis represents the semi-field angle (unit: °). From the figure, it can be seen that the F-Tan(Theta) distortion of the lens is small and less than 2%, indicating that the distortion is well corrected.

[0088] Embodiment 2

[0089] Refer to Figure 6As shown, it is a schematic diagram of the optical structure of Embodiment 2. In this embodiment, the total focal length f of the lens is 33 mm, the aperture value F# is 3.1, the full image height IH is 14.9 mm, the field of view angle DFOV is 30°, and the total optical length TTL of the lens is 57 mm.

[0090] In this embodiment, the radius of curvature (unit: mm), central thickness d (unit: mm), refractive index (ND), and Abbe number (VD) of the first lens 1, second lens 2, third lens 3, and fourth lens 4 are shown in Table 4.

[0091] Table 4

[0092]

[0093]

[0094] In Table 4, the radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side, where "Infinity" represents that the surface is a plane; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the current lens material to deflect light, and the Abbe number represents the dispersion characteristics of the current lens material with respect to light.

[0095] Please refer to Figure 7 , which shows the axial chromatic aberration diagram of the lens in this embodiment. The horizontal axis represents the intersection position of the light ray and the optical axis (unit: mm), and the vertical axis represents different apertures of the lens. It can be seen from the figure that the axial chromatic aberration is less than 0.35 mm.

[0096] Embodiment 3

[0097] Refer to Figure 8 As shown, it is a schematic diagram of the optical structure of Embodiment 3. In this embodiment, the total focal length f of the lens is 28 mm, the aperture value F# is 1.46, the full image height IH is 14.8 mm, the field of view angle DFOV is 30°, and the total optical length TTL of the lens is 50 mm.

[0098] In this embodiment, the radius of curvature (unit: mm), central thickness d (unit: mm), refractive index (ND), and Abbe number (VD) of the first lens 1, second lens 2, third lens 3, and fourth lens 4 are shown in Table 5.

[0099] Table 5

[0100] Surface number Radius of curvature R Central thickness d Refractive index ND Abbe number VD S1 22.0290 4.1069 1.88 39.2 S2 180.9835 0.4219 S3 Infinity 7.6514 S4 -28.7848 2.9446 1.81 22.7 S5 19.2811 5.7415 S6 57.4853 7.8115 1.74 52.7 S7 -23.5395 0.1693 S8 22.3502 11.2273 1.8 46.6 S9 33.7814 9.9483 S10 Infinity

[0101] In Table 5, the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. Among them, "Infinity" represents that the surface is a plane; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the light-bending ability of the current lens material, and the Abbe number represents the chromatic dispersion characteristics of the current lens material.

[0102] Please refer to Figure 9 , which shows the axial chromatic aberration diagram of the lens in this embodiment. The horizontal axis represents the intersection position of the light ray and the optical axis (unit: mm), and the vertical axis represents different apertures of the lens. It can be seen from the figure that the axial chromatic aberration is about 0.25 mm.

[0103] Refer to Figure 10 As shown, the relative illuminance of the lens at the maximum field of view is greater than 95%, and the light input is sufficient. On the basis of Embodiment 1, the relative illuminance is further improved, ensuring that there is no vignetting in the actual shooting image even when the lens is used in a relatively dim environment.

[0104] Please refer to Figure 11 and Figure 12 , which shows the field curvature and F-Tan(Theta) distortion diagrams of the lens in this embodiment. In the field curvature diagram, the horizontal axis represents the field curvature amount (unit: mm), and the vertical axis represents the semi-field angle (unit: °). In the distortion diagram, the horizontal axis represents the F-Tan(Theta) distortion (unit: %), and the vertical axis represents the semi-field angle (unit: °). It can be seen from Figure 11 that the change in the field curvature amount is less than 0.5 mm; it can be seen from Figure 12 that the F-Tan(Theta) distortion of the lens is small and less than 3%, indicating that the distortion is well corrected.

[0105] In summary, this projection lens adopts a 4-piece all-glass structure. The total focal length f of the optical lens satisfies f ≤ 35 mm, and the aperture F# can reach F# ≤ 3.1. At large apertures and large focal lengths, the clear aperture is relatively large, which can ensure a high relative illuminance of the system and no vignetting in the captured image. At the same time, the system aberrations are well corrected, and the optical performance is good. In terms of manufacturability, each lens is not sensitive, the lens surface type is simple and easy to manufacture, the structure between the lenses is compact, and its processing cost is relatively low compared to those on the market, with a high cost performance. It can achieve the characteristics of small size, light weight, good performance, and low cost. Moreover, through reasonable selection of lens materials, distribution of optical power, and optimization of optical design, this utility model has a relatively high relative illuminance.

[0106] The above only expresses the preferred technical solutions of the present utility model. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the utility model patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several variations and improvements can still be made, and the present utility model also intends to include these modifications and variations.

Claims

1. A projection lens, defining the surface adjacent to the left side of the lens as the image side and the surface adjacent to the right side of the lens as the light source side, characterized in that: They are arranged in sequence from the left side to the right side along the lens optical axis: A first lens, the first lens being a glass lens with a positive optical power, the image side of the first lens being convex and the light source side being concave; A second lens, the second lens being a glass lens with a negative optical power, the image side of the second lens being concave; A third lens, the third lens being a glass lens with a positive optical power, the image side of the third lens being convex; A fourth lens, the fourth lens being a spherical glass lens with a positive optical power, the image side of the fourth lens being convex and the light source side being concave; The lens satisfies the following relational expressions: 0.9 ≤ f1 / f ≤ 1.2, -1.4 ≤ f2 / f ≤ -0.4, 0.7 ≤ f3 / f ≤ 2, 1 ≤ f4 / f ≤ 3.2, TTL / f ≤ 1.8, In the relational expressions, TTL is the overall optical length of the lens, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

2. The projection lens according to claim 1, wherein: The lens satisfies the following relational expressions: IH / TTL ≥ 0.25, OBFL / TTL ≥ 0.03; In the relational expressions, f is the total focal length of the lens, OBFL is the optical back focal length of the lens, and IH is the full image height of the chip matched with the lens system.

3. The projection lens according to claim 1, wherein: The respective ranges of the focal lengths corresponding to the first lens, the second lens, the third lens, and the fourth lens are 25 to 35, -39 to -14, 23 to 54, and 29 to 96; the unit of the focal length is mm.

4. The projection lens according to claim 1, characterized in that: The respective ranges of the refractive indices corresponding to the first lens, the second lens, the third lens, and the fourth lens are 1.70 to 1.90, 1.75 to 1.96, 1.52 to 1.80, and 1.75 to 1.

90.

5. The projection lens according to claim 1, characterized in that: The respective ranges of the image side curvature radii corresponding to the first lens, the second lens, the third lens, and the fourth lens are 12.3 to 22.1, -28.9 to -7.2, 25.4 to 57.5, and 15.9 to 23.9; the respective ranges of the light source side curvature radii corresponding to the first lens, the second lens, the third lens, and the fourth lens are 25.1 to 181.0, -34.3 to 19.3, -117.0 to 252.6, and 13.9 to 2780.2; the unit of the curvature radius is mm.

6. The projection lens according to claim 1, wherein: The aperture of the lens is F#, satisfying F# ≤ 3.1; the total focal length of the lens is f, satisfying f ≤ 35 mm.

7. The projection lens according to claim 1, wherein: The overall optical length of the lens is TTL, satisfying TTL ≤ 57 mm.

8. The projection lens according to claim 1, characterized in that: The divergence angle of the lens ≤ 40°, and the chief ray angle of the lens is CRA, CRA < 1°.

9. The projection lens according to claim 1, wherein: The lens further includes a diaphragm, and the diaphragm is located between the first lens and the second lens.

Images