A free-form surface imaging lens

Abstract

The present invention discloses a free-form surface imaging lens, which includes, from the object side to the image side: a first lens with negative optical power, both surfaces of which are free-form surfaces; a second lens with negative optical power, both surfaces of which are free-form surfaces; a third lens with positive optical power, both surfaces of which are free-form surfaces; a filter; and a chip protection glass. The imaging lens satisfies the following relationships: -3.51 < f1 / f < -3.15 (1) -36.193 < f2 / f < -36.014 (2) 1.25 < f3 / f < 1.45 (3) 1.29 < f < 1.41 (4) where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and f is the effective focal length of the lens; all surfaces of the above lens are free-form surfaces, and the lens materials are all plastics, which can be mass-produced; the above lens has a strip-shaped field of view, with a large difference between the horizontal field of view angle and the vertical field of view angle, and different magnification ratios in the X direction and the Y direction.

Description

[Technical field]

[0001] The invention relates to a free-form surface imaging lens. [Background technology]

[0002] With the development of society and the progress of science and technology, more and more high-end technology products have entered people's lives. In addition to rotationally symmetrical lenses such as spherical and aspherical lenses, non-rotationally symmetrical optical systems have also become an indispensable part of high-tech equipment. The optical system composed of non-rotationally symmetrical lenses can show different imaging characteristics in the X and Y directions. This patent mainly involves an imaging lens with different field angles and different optical characteristics in the X and Y directions. [Summary of the invention]

[0003] 1. The imaging lens is characterized in that a first lens (L1), a second lens (L2), a third lens (L3), a filter, and a chip protection glass are sequentially arranged from the object plane to the image plane;

[0004] The first lens (L1) is made of plastic, and both surfaces of the lens are free-form surfaces. The second lens (L2) is made of plastic, and both surfaces of the lens are free-form surfaces. The third lens (L3) is made of plastic, and both surfaces of the lens are free-form surfaces. 2. The imaging lens satisfies the following relationship:

[0005] When DI<0.7*MDI, AN<30°;

[0006] TTL<8.7;

[0007] YZ direction: 93° <FOV<110°

[0008] XZ direction: 15° <FOV<23°。

[0009] -3.51 <f1 / f<-3.15;-36.193<f2 / f<-36.014;1.25<f3 / f<1.45;1.29<f<1.41;

[0010] Among them, AN is the acute angle between the normal direction of each point on the aspheric surface of the first lens close to the object plane and the optical axis, DI is the diameter of the aspheric surface of the first lens close to the image plane perpendicular to the optical axis, MDI is the maximum effective diameter, TTL is the distance from the object side surface of the first lens to the image plane on the optical axis, and FOV is the maximum field of view of the imaging lens.

[0011] f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and f is the effective focal length of the lens.

[0012] 3. The aperture is arranged between the image side surface of the second lens and the object side surface of the third lens, and the lens satisfies the following relationship:

[0013] YASP-XASP>1.5

[0014] YASP is the optically effective diameter of the object side of the first lens in the YZ direction, and XASP is the optically effective diameter of the object side of the first lens in the XZ direction.

[0015] 4. The imaging lens satisfies the following relationship:

[0016] 0.17 <T1 / ∑T<0.33;

[0017] 0.33 <T2 / ∑T<0.38;

[0018] 0.31 <T3 / ∑T<0.37;

[0019] Wherein, ∑T is the sum of the lens thicknesses of the first lens, the second lens, and the third lens on the optical axis, respectively, T1 is the lens thickness of the first lens on the optical axis, T2 is the lens thickness of the second lens on the optical axis, and T3 is the lens thickness of the third lens on the optical axis.

[0020] 5. The imaging lens satisfies the following relationship:

[0021] 1.29 <f<1.41;

[0022] -36.193 <f2 / f<-36.014;

[0023] Among them, f is the effective focal length of the lens, and f2 is the effective focal length of the second lens.

Brief Description of the Drawings

[0024] Figure 1 Schematic diagram of the structure of the imaging lens.

[0025] Figure 2 This is the transfer function curve of the imaging lens.

[0026] Figure 3 is the relative illumination diagram of the imaging lens.

[0027] Figure 4 This is the astigmatism curve of the imaging lens.

[0028] Figure 5 is the distortion diagram of the imaging lens. [Specific implementation method]

[0029] 1. As Figure 1As shown, the free-form surface optical system of this embodiment is provided with a first lens (L1), a second lens (L2), a third lens (L3), a filter, and a chip protection glass in sequence from the object plane to the image plane. The lens material is plastic material, and both surfaces of the lens are free-form surfaces.

[0030] 2. The imaging lens satisfies the following relationship:

[0031] When DI<0.7*MDI, AN<30°;

[0032] TTL<8.7;

[0033] YZ direction: 93° <FOV<110°

[0034] XZ direction: 15° <FOV<23°。

[0035] Among them, AN is the acute angle of the normal direction of each point on the aspheric surface of the first lens close to the object side relative to the optical axis, DI is the diameter of the aspheric surface of the first lens close to the image side perpendicular to the optical axis, MDI is the maximum effective diameter, TTL is the distance from the object side surface of the first lens to the image plane on the optical axis, FOV is the maximum field of view of the imaging lens, and the XZ and YZ directions have different field of view angles. It meets different imaging requirements in the X and Y directions.

[0036] 3. The aperture is arranged between the image side surface of the second lens and the object side surface of the third lens, and the lens satisfies the following relationship;

[0037] YASP-XASP>1.5

[0038] YASP is the optically effective diameter of the object side of the first lens in the YZ direction, and XASP is the optically effective diameter of the object side of the first lens in the XZ direction. The optically effective diameter in the YZ direction is greater than the optically effective diameter in the XZ direction, which is beneficial to increasing the field of view in the YZ direction and improving the imaging quality when the field of view in the two directions is different.

[0039] The first lens of the imaging lens is a meniscus lens with negative focal length, which is beneficial to increase the field of view in the Y and Z directions. The aperture is set between the second lens and the third lens, which is beneficial to the control of aberrations under a large field of view and reduces the total length of the optical system.

[0040] 4. The imaging lens satisfies the following relationship:

[0041] -3.51 <f1 / f<-3.15;-36.193<f2 / f<-36.014;1.25<f3 / f<1.45;1.29<f<1.41;

[0042] Among them, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and f is the effective focal length of the lens.

[0043] The first lens and the second lens have negative optical power, which can deflect the large-angle incident light into small-angle light as quickly as possible, and then converge onto the image plane through the third lens with positive optical power, which is beneficial to shortening the overall length of the lens.

[0044] 5. The imaging lens satisfies the following relationship:

[0045] 0.17 <T1 / ∑T<0.33;

[0046] 0.33 <T2 / ∑T<0.38;

[0047] 0.31 <T3 / ∑T<0.37;

[0048] Wherein, ∑T is the sum of the lens thicknesses of the first lens, the second lens, and the third lens on the optical axis, respectively, T1 is the lens thickness of the first lens on the optical axis, T2 is the lens thickness of the second lens on the optical axis, and T3 is the lens thickness of the third lens on the optical axis.

[0049] The second lens is the thickest, which is beneficial for the deflection of large-angle light, reducing the total length of the lens, and making the lens thinner and lighter. Controlling the thickness of each lens is beneficial for correcting aberrations and mutual compensation, reducing tolerance sensitivity and molding difficulty.

[0050] 6. The imaging lens satisfies the following relationship:

[0051] 1.29 <f<1.41;

[0052] -36.193 <f2 / f<-36.014;

[0053] Wherein, f is the effective focal length of the lens, and f2 is the effective focal length of the second lens. The second lens has a larger focal length in the YZ direction, which is beneficial for correcting high-order aberrations.

[0054] The following table is the lens data table of the embodiment

[0055] Table 1 is a table of structural parameters of the free-form surface imaging lens of the present invention.

[0056]

[0057]

[0058] Table 2 shows the ratio of the centerline sag / R of the X and Y directions of each lens surface to the radius R

[0059]

[0060]

Claims

1. A free-form surface imaging lens, characterized in that: A first lens (L1), a second lens (L2), a third lens (L3), a filter, and a chip protection glass are sequentially arranged from the object plane to the image plane; The first lens (L1) is made of plastic, and both surfaces of the lens are free-form surfaces; The second lens (L2) is made of plastic, and both surfaces of the lens are free-form surfaces; The third lens (L3) is made of plastic, and both surfaces of the lens are free-form surfaces; The number of lenses with optical power is 3; When DI<0.7*MDI, AN<30°; TTL<8.7; YZ direction: 93° <FOV<110°; XZ direction: 15° <FOV<23°; Wherein, AN is the acute angle between the normal direction of each point on the aspheric surface of the first lens close to the object plane and the optical axis, DI is the diameter of the aspheric surface of the first lens close to the image plane perpendicular to the optical axis, MDI is the maximum effective diameter, TTL is the distance from the object side surface of the first lens to the image plane on the optical axis, and FOV is the maximum field of view of the imaging lens; The imaging lens satisfies the following relationship: -3.51 <f1 / f<-3.15;-36.193<f2 / f<-36.014;1.25<f3 / f<1.45;1.29<f<1.41; Among them, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and f is the effective focal length of the lens.

2. According to the free-form surface imaging lens of claim 1, the aperture is arranged between the image side surface of the second lens and the object side surface of the third lens, and the lens satisfies the following relationship: YASP-XASP>1.5; YASP is the optically effective diameter of the object side of the first lens in the YZ direction, and XASP is the optically effective diameter of the object side of the first lens in the XZ direction.

3. The free-form surface imaging lens according to claim 1, wherein the imaging lens satisfies the following relationship: 0.17 <T1 / ∑T<0.33; 0.33 <T2 / ∑T<0.38; 0.31 <T3 / ∑T<0.37; in, ∑T is the sum of the lens thicknesses of the first lens, the second lens, and the third lens on the optical axis, respectively, T1 is the lens thickness of the first lens on the optical axis, T2 is the lens thickness of the second lens on the optical axis, and T3 is the lens thickness of the third lens on the optical axis.

Images