CN210864167U - Free-form surface imaging lens - Google Patents

Abstract

The utility model discloses a free-form surface imaging lens, belonging to the technical field of optical lenses, comprising a first lens with negative focal power, a second lens with negative focal power and a third lens with positive focal power from an object side to an image side, wherein two surfaces of the three lenses are free-form surfaces; an optical filter; chip protection glass; the imaging lens satisfies the following relation: -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). 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 lens are free curved surfaces, and the lens is made of plastic, so that the lens can be produced in a large scale; the lens has a strip-shaped field of view, the horizontal field of view and the vertical field of view are greatly different, and the magnification in the X direction is different from that in the Y direction.

Description

Free-form surface imaging lens

[ technical field ] A method for producing a semiconductor device

The invention belongs to the technical field of optical lenses, and particularly relates to a free-form surface imaging lens.

[ background of the invention ]

With social development and technological progress, more and more high-end technological products are in the middle of life of people. In addition to rotationally symmetric lenses such as spherical and aspherical lenses, non-rotationally symmetric optical systems are also an indispensable part of high-tech devices. An optical system composed of non-rotation symmetrical lenses can show different imaging characteristics in X, Y directions (horizontal/vertical), and the patent mainly relates to an imaging lens with different field angles and different optical characteristics in X-Y directions.

[ summary of the invention ]

In view of the above defects or improvement requirements of the prior art, the present invention provides a free-form surface imaging lens, which aims to meet the application requirements of the lens for inconsistent imaging ranges in different directions.

In order to achieve the purpose, the invention provides a free-form surface imaging lens, which is provided with a first lens (L1), a second lens (L2), a third lens (L3), an optical filter and chip protection glass in sequence from an object plane to an image plane;

the first lens (L1) is made of plastic material, and both surfaces of the lens are free-form surfaces. The second lens (L2) is made of plastic material, and both surfaces of the lens are free-form surfaces. The third lens (L3) is made of plastic material, and both surfaces of the lens are free curved surfaces; the focal length of each lens element satisfies the following relation: -3.51< f1/f < -3.15; -36.193< f2/f < -36.014; 1.25< f3/f < 1.45; YASP-XASP > 1.5; wherein 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, f is the effective focal length of the lens, YASP is the optical effective diameter of the object side surface of the first lens in the Y-Z direction, and XASP is the optical effective diameter of the object side surface of the first lens in the X-Z direction.

Preferably, the following relation is also satisfied: AN <30 ° when DI <0.7 × MDI; TTL < 8.7; Y-Z direction: 93 ° < FOV <110 °; X-Z direction: 15 ° < FOV <23 °; the AN is AN acute angle included angle between the normal direction of each point on the aspheric surface of the first lens close to the object plane side and the optical axis, the DI is the diameter of the aspheric surface of the first lens close to the image plane side, which is perpendicular to the optical axis direction, the MDI is the maximum effective diameter, the TTL is the distance between the object plane side surface of the first lens and the image plane on the optical axis, and the FOV is the maximum field angle of the imaging lens.

Preferably, the free-form surface imaging lens stop is disposed between the image side surface of the second lens and the object side surface of the third lens, and the lens satisfies the following relation: YASP-XASP > 1.5; YASP is the optical effective diameter of the object side surface of the first lens in the Y-Z direction, and XASP is the optical effective diameter of the object side surface of the first lens in the X-Z direction.

Preferably, the free-form surface imaging lens satisfies the following relation:

0.17< T1/∑ T <0.33, 0.33< T2/∑ T <0.38, and 0.31< T3/∑ T <0.37, wherein ∑ T is the sum of the thicknesses of the first lens, the second lens and the third lens on the optical axis, T1 is the thickness of the first lens on the optical axis, T2 is the thickness of the second lens on the optical axis, and T3 is the thickness of the third lens on the optical axis.

Preferably, the free-form surface imaging lens satisfies the following relation:

1.29< f < 1.41; f is the effective focal length of the lens.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

the focal length and the optical effective diameter of each lens element of the invention are compared with other same types under the condition of satisfying a certain relation: the imaging quality is ensured, and different field angles exist in the X-Z and Y-Z directions; the field angle in the Y-Z direction is larger than 93 degrees, and the shooting field is larger; the distortion is relatively small while the image quality is ensured by reasonably arranging the diaphragm, and the total length of the optical system is reduced; and each lens material belongs to plastic, has low optical sensitivity and is beneficial to mass production.

[ description of the drawings ]

Fig. 1 is a schematic structural diagram of the imaging lens.

Fig. 2 is a transfer function graph of the imaging lens.

Fig. 3 is a relative illuminance diagram of the imaging lens.

Fig. 4 is a graph of astigmatism of the imaging lens.

Fig. 5 is a distortion diagram of the imaging lens.

[ detailed description ] embodiments

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, the free-form optical system of the present embodiment includes a first lens (L1), a second lens (L2), a third lens (L3), an optical filter, and a chip cover glass in this order from the object plane to the image plane. The lens is made of plastic materials, and two surfaces of the lens are free-form surfaces. The focal length of each lens element satisfies the following relation: -3.51< f1/f < -3.15; -36.193< f2/f < -36.014; 1.25< f3/f < 1.45; YASP-XASP > 1.5;

wherein 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, f is the effective focal length of the lens, YASP is the optical effective diameter of the object side surface of the first lens in the Y-Z direction, and XASP is the optical effective diameter of the object side surface of the first lens in the X-Z direction. The first lens and the second lens have negative focal power, so that large-angle incident light can be deflected into small-angle light as soon as possible, and the small-angle light is converged on an image surface through the third lens with positive focal power, and the total length of the lens can be reduced.

The free-form surface imaging lens with the structure is compared with other same types: the imaging quality is ensured, and different field angles exist in the X-Z and Y-Z directions; the field angle in the Y-Z direction is larger than 93 degrees, and the shooting field is larger; the distortion is relatively small while the image quality is ensured by reasonably arranging the diaphragm, and the total length of the optical system is reduced; and each lens material belongs to plastic, has low optical sensitivity and is beneficial to mass production.

As another implementation example, the free-form surface imaging lens satisfies the following relation:

AN <30 ° when DI <0.7 × MDI; TTL < 8.7;

Y-Z direction: 93 ° < FOV <110 °,

X-Z direction: 15 ° < FOV <23 °.

The AN is AN acute angle included angle between the normal direction of each point on the aspheric surface of the first lens close to the object plane side and the optical axis, the DI is the diameter of the aspheric surface of the first lens close to the image plane side, which is perpendicular to the optical axis direction, the MDI is the maximum effective diameter, the TTL is the distance between the object plane side surface of the first lens and the image plane on the optical axis, the FOV is the maximum field angle of the imaging lens, and the X-Z direction and the Y-Z direction have different field angles. Satisfying the imaging requirements of X, Y different directions.

As another implementation example, the free-form surface imaging lens satisfies that an aperture is disposed between the image-side surface of the second lens and the object-side surface of the third lens, and the lens satisfies the following relational expression;

YASP-XASP > 1.5; the YASP is the optical effective diameter of the object side surface of the first lens in the Y-Z direction, the XASP is the optical effective diameter of the object side surface of the first lens in the X-Z direction, and the optical effective diameter of the Y-Z direction is larger than that of the X-Z direction, so that the visual angle of the Y-Z direction is increased, and the imaging quality is improved under the condition that the visual angles of the two directions are different.

The first lens of the imaging lens is a meniscus lens with negative focal power, and the Y-Z direction field angle can be increased. The diaphragm is arranged between the second lens and the third lens, so that aberration control under a large field angle is facilitated, and the total length of the optical system is reduced.

As another implementation example, the free-form surface imaging lens satisfies the following relation:

0.17<T1/∑T<0.33；0.33<T2/∑T<0.38；0.31<T3/∑T<0.37；

wherein ∑ T is the total of the optical thicknesses of the first lens, the second lens and the third lens, T1 is the optical thickness of the first lens, T2 is the optical thickness of the second lens, and T3 is the optical thickness of the third lens.

The second lens is thickest, so that deflection of large-angle light rays is facilitated, the total length of the lens is reduced, and the lens is light and thin. The thickness of each lens is controlled, which is beneficial to correcting aberration and compensating each other, and reduces tolerance sensitivity and forming difficulty.

As another implementation example, the free-form surface imaging lens satisfies the following relation:

1.29<f<1.41；-36.193<f2/f<-36.014；

where f is the effective focal length of the lens, and f2 is the effective focal length of the second lens. The focal length of the second lens in the Y-Z direction is larger, which is beneficial to correcting high-order aberration.

The following table is a table of lens data for the examples

Table 1 is a structural parameter table of the free-form surface imaging lens of the present embodiment

Here, the working distance of the free-form surface imaging lens of this example is 400 mm.

The central thickness of the first lens element is 1.5157mm, the central thickness of the rear surface S2 of the first lens element and the front surface S3 of the second lens element is 0.3994mm (namely, the air gap between the first lens element and the second lens element on the optical axis is 0.05mm), and the refractive index/abbe number of the first lens element is 1.624/22.37.

The center thickness from the front surface S3 to the middle surface S4 of the second lens element is 1.9644mm (i.e., the center thickness of the second lens piece is 1.9644 mm). The central thickness between the rear surface S4 of the second lens element and the stop STO is 0.01mm, and the central thickness between the stop STO and the front surface S5 of the third lens element is 0.01mm (i.e., the air gap between the second lens element and the third lens element on the optical axis is 0.01mm +0.01 mm — 0.02 mm); the refractive index/Abbe number of the second lens is 1.537/56.17.

The central thickness of the third lens element is 1.9214mm, the central thickness of the rear surface S6 and the filter front surface S7 of the third lens element is 0.1mm (namely, the air gap between the third lens element and the filter element on the optical axis is 0.1mm), and the refractive index/abbe number of the third lens element is 1.624/22.37.

The ratio of the rise to the radius R of each curved lens is shown in the following table.

Table 2 shows the ratio sag/R of the rise of the center line in the X and Y directions to the radius R of each lens surface

Claims (4)

1. The free-form surface imaging lens is characterized in that a first lens (L1), a second lens (L2), a third lens (L3), an optical filter and chip protection glass are arranged in sequence from an object plane to an image plane, and a diaphragm is arranged between the image side surface of the second lens and the object side surface of the third lens;

the first lens (L1) is made of plastic materials, and two surfaces of the lens are free-form surfaces;

the second lens (L2) is made of plastic materials, and two surfaces of the lens are both free-form surfaces;

the third lens (L3) is made of plastic materials, and two surfaces of the lens are both free-form surfaces;

and the focal length of each lens element satisfies the following relation:

-3.51<f1/f<-3.15；-36.193<f2/f<-36.014；1.25<f3/f<1.45；YASP-XASP>1.5；

wherein 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, f is the effective focal length of the lens, YASP is the optical effective diameter of the object side surface of the first lens in the Y-Z direction, and XASP is the optical effective diameter of the object side surface of the first lens in the X-Z direction.

2. The free-form surface imaging lens according to claim 1, characterized by satisfying the following relation:

AN <30 ° when DI <0.7 × MDI;

TTL<8.7；

Y-Z direction: 93 ° < FOV <110 °;

X-Z direction: 15 ° < FOV <23 °;

the AN is AN acute angle included angle between the normal direction of each point on the aspheric surface of the first lens close to the object plane side and the optical axis, the DI is the diameter of the aspheric surface of the first lens close to the image plane side, which is perpendicular to the optical axis direction, the MDI is the maximum effective diameter, the TTL is the distance between the object plane side surface of the first lens and the image plane on the optical axis, the FOV is the maximum field angle of the imaging lens, and the field angles in the X-Z direction and the Y-Z direction are different.

3. The free-form surface imaging lens according to claim 1, characterized by satisfying the following relation:

0.17<T1/∑T<0.33；

0.33<T2/∑T<0.38；

0.31<T3/∑T<0.37；

wherein ∑ T is the total of the optical thicknesses of the first lens, the second lens and the third lens, T1 is the optical thickness of the first lens, T2 is the optical thickness of the second lens, and T3 is the optical thickness of the third lens.

4. The free-form surface imaging lens according to claim 1, characterized by satisfying the following relation:

1.29<f<1.41；

wherein f is the effective focal length of the lens.

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