CN105487202B - The four-piece type optical shooting lens and its imaging method for the angle of visual field of being grown up with short mirror - Google Patents

Abstract

The present invention relates to a four-piece optical imaging lens with a short lens and a long field of view, comprising an aperture stop arranged sequentially along the optical axis of the lens from the object side to the image side, and a first lens L1 with positive diopter , a second lens L2 with a negative diopter, a third lens L3 with a positive diopter, a fourth lens L4 with a negative diopter, an optical filter and an image acquisition element; The imaging method of the four-piece optical imaging lens. The invention can effectively shorten the total length of the lens, reduce the system sensitivity, and obtain good imaging quality; in addition, the surface shape of each lens is simple and easy to manufacture, and the tolerance is relatively loose, which greatly reduces the production cost.

Description

Four-piece optical imaging lens with short lens and long field of view and imaging method thereof

technical field

The invention relates to a four-piece optical imaging lens with a short lens and a long field of view and an imaging method thereof.

Background technique

With the advancement of technology, optical imaging lenses are developing towards short, high resolution, large field of view and low cost. In terms of electronic products, such as: digital cameras, mobile phones, and personal digital aids, optical imaging lenses They all occupy half of the country.

Imaging lenses used in small electronic products currently have three-lens, four-lens, and five-lens designs. At present, the three-element imaging lens has basically been eliminated. From the perspective of imaging quality, the multi-element optical imaging lens has better performance in terms of aberration correction and optical transfer function MTF. Advantages, it can be used in electronic products with high pixel requirements, but the total length of the lens is too long, which is not conducive to use on ultra-thin mobile phones. The difference between the structural design or technical features of the existing four-piece optical imaging lens is determined by the change or combination of the following factors, such as the corresponding convex/concave directions of the four lenses. , in order to adjust the angle of light incident and exit; or related data between the four lenses, such as focal length EFL, distance TC _i between each optical surface, curvature R _i of each optical surface, etc., to meet different conditions respectively.

In practice, a design with a short lens length, good aberration correction, high resolution, and low cost is an urgent need for users.

Contents of the invention

In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a four-piece optical imaging lens with a short lens and a long field of view and an imaging method thereof with reasonable structural design, practicality and low cost.

In order to solve the above technical problems, the technical solution of the present invention is: a four-piece optical imaging lens with a short lens and a long field of view, including aperture light arrays arranged in sequence from the object side to the image side along the optical axis of the lens Stop, first lens L1 with positive diopter, second lens L2 with negative diopter, third lens L3 with positive diopter, fourth lens L4 with negative diopter, filter and image acquisition element.

Preferably, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all aspheric lenses, wherein the object side of the first lens L1 is convex, and the object side of the first lens L1 is The image side is a concave surface, the object side of the second lens L2 is a concave surface, the image side of the second lens L2 is a convex surface, and the large aperture of the image side of the second lens L2 is bent to the image side, and the third lens The object side of L3 is concave, the image side of the third lens L3 is convex, and the object side and image side of the fourth lens L4 are W-shaped.

Preferably, the distance TTL from the object side of the first lens L1 to the imaging surface of the image acquisition element on the optical axis of the lens, the central air gap between the first lens L1 and the second lens L2 is ACT ₁ , and the second lens L1 The central air gap between lens L2 and third lens L3 is ACT ₂ , the central air gap between third lens L3 and fourth lens L4 is ACT ₃ , the central thickness of third lens L3 is GCT ₃ , and the third lens L3 has a central air gap of ACT 3 . The edge thickness GET ₃ of the lens L3, the distance from the nearest point from the image side of the fourth lens L4 to the imaging surface of the image acquisition element and the imaging surface of the image acquisition element is BFL, and the focal length EFL of the overall optical imaging lens group satisfies The following relationships: 0.19<BFL/TTL<0.23, 1.2<TTL/EFL<1.5, 0.18<(ACT ₁ +ACT ₂ +ACT ₃ )/EFL<0.45, 0.44<GCT ₃ /GET ₃ <0.74.

Preferably, the focal length f 1 of the first lens L1, the focal length f ₃ of the _third lens L3, and the focal length EFL of the overall optical imaging lens group satisfy the following relationship: 1.0<EFL/f ₁ <1.14, 0.26< EFL/f ₃ <0.47.

Preferably, the curvature radius R3 of the object side surface of the second lens L2 and the curvature radius R4 of the image side surface of the second lens L2 satisfy the following relationship: 0.4<R3/R4<1.1.

Preferably, the chief ray incident angle CRA of the image acquisition element, the half y of the diagonal line of the effective pixel area of the image acquisition element, the half w of the overall field of view, and the object side surface of the first lens L1 to The distance TTL of the imaging surface of the image acquisition element satisfies the following relationship: 1.5<TTL/y<1.6, 1.2<w/CRA<1.4.

Preferably, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 all satisfy the following relationship: In the formula, z is the vector height of the aspheric surface, c is the curvature of the aspheric surface, K is the conic coefficient of the quadric surface, r is the radial coordinate of the aspheric surface, A ₄ , A ₆ , A ₈ ... are the four, six, and Eight...Equal-order aspheric coefficients.

Preferably, the first lens L1 , the second lens L2 , the third lens L3 and the fourth lens L4 are all made of plastic material with a refractive index less than 1.65, and the filter is made of Schott-BK7 material.

An imaging method of a four-piece optical imaging lens with a short mirror and a long field of view, comprising any of the four-piece optical imaging lenses with a short mirror and a long field of view, comprising the following steps:

(1) The light beam enters the first lens L1 through the aperture stop, wherein the on-axis light beam passing through the first lens L1 tends to converge, and the light with a large field of view has a larger exit angle;

(2) The light beam passes through the second lens L2 with high refractive index, wherein the central beam is further converged, and the inflection at the large aperture on the image side of the second lens L2 makes the light rays in the outermost field of view gather, which can effectively control the most Spherical aberration and speckle in the outer field of view;

(3) After the light beams pass through the regular low-refraction third lens L3, the light beams in each field of view are evenly distributed, and the light beams transition smoothly, and the chromatic aberration can be better corrected after the light beams pass through the second lens L2 and the third lens L3;

(4) The light beam converges to the image acquisition element after passing through the fourth lens L4, and the object side and the image side of the fourth lens L4 are both W-shaped, which not only ensures that each field of view is on the imaging surface of the image acquisition element The incident angle of the chief ray is as small as possible, and the field area and distortion aberration are effectively improved.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The structure design of the present invention is reasonable, can effectively correct aberrations, increase the back focus of the lens, reduce the sensitivity of the system, make the lens more compact and thus shorten the total length, thereby improving the applicability of the present invention;

(2) The use of the same plastic material for the first lens L1, the third lens L3, and the fourth lens L4 of the present invention is beneficial to reduce materials and costs, and can achieve a larger image height;

(3) The configuration of the lens spacing of the present invention is conducive to assembly, further shortening the total length of the lens to be suitable for miniaturized electronic devices;

(4) Each lens surface of the present invention is simple and easy to manufacture, and the tolerance is relatively loose, which greatly reduces the production cost.

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

FIG. 1 is an optical structure diagram of Embodiment 1 of the present invention.

Fig. 2 is a longitudinal spherical aberration diagram of Embodiment 1 of the present invention.

FIG. 3 is a field curvature diagram of Embodiment 1 of the present invention.

FIG. 4 is a distortion diagram of Embodiment 1 of the present invention.

FIG. 5 is an optical structure diagram of Embodiment 2 of the present invention.

Fig. 6 is a diagram of longitudinal spherical aberration of Embodiment 2 of the present invention.

FIG. 7 is a field curvature diagram of Embodiment 2 of the present invention.

FIG. 8 is a distortion diagram of Embodiment 2 of the present invention.

FIG. 9 is an optical structure diagram of Embodiment 3 of the present invention.

Fig. 10 is a diagram of longitudinal spherical aberration of Embodiment 3 of the present invention.

FIG. 11 is a field curvature diagram of Embodiment 3 of the present invention.

FIG. 12 is a distortion diagram of Embodiment 3 of the present invention.

Fig. 13 is an optical structure diagram of Embodiment 4 of the present invention.

Fig. 14 is a longitudinal spherical aberration diagram of Embodiment 4 of the present invention.

FIG. 15 is a field curvature diagram of Embodiment 4 of the present invention.

FIG. 16 is a distortion diagram of Embodiment 4 of the present invention.

Fig. 17 is an optical structure diagram of Embodiment 5 of the present invention.

Fig. 18 is a longitudinal spherical aberration diagram of Embodiment 5 of the present invention.

FIG. 19 is a field curvature diagram of Embodiment 5 of the present invention.

Fig. 20 is a distortion diagram of Embodiment 5 of the present invention.

In the figure: L1-first lens L1, L2-second lens L2, L3-third lens L3, L4-fourth lens L4, 5-aperture stop, 6-filter, 7-image acquisition element.

Detailed ways

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail with reference to the accompanying drawings.

As shown in Figures 1 to 20, a four-piece optical imaging lens with a short lens and a long field of view includes an aperture stop 5 arranged in sequence along the optical axis of the lens from the object side to the image side, and has a positive A first lens L1 with a diopter, a second lens L2 with a negative diopter, a third lens L3 with a positive diopter, a fourth lens L4 with a negative diopter, a filter 6 and an image acquisition element 7; the aperture stop 5 It belongs to a kind of aperture front, which can be realized by a mirror frame when designing the mechanism; the filter 6 can be made of BK7 or K9 glass, and its surface should be coated with a film layer that can cut off infrared light; the image acquisition Element 7 includes CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), which can convert image signals into electronic signal output; the combination of positive and negative diopters of the first lens L1 and the second lens L2 has It is conducive to better correction of chromatic aberration.

In the embodiment of the present invention, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all aspheric lenses, wherein the object side surface of the first lens L1 is a convex surface, and the second lens L1 is convex. The image side of a lens L1 is a concave surface, the object side of the second lens L2 is a concave surface, the image side of the second lens L2 is a convex surface, and the image side of the second lens L2 is bent toward the image side at a large aperture, so The object side of the third lens L3 is concave, the image side of the third lens L3 is convex, and the object side and image side of the fourth lens L4 are W-shaped.

In the embodiment of the present invention, the distance TTL from the object side of the first lens L1 to the imaging surface of the image acquisition element 7 on the optical axis of the lens, and the central air gap between the first lens L1 and the second lens L2 are ACT ₁ , The center air gap between the second lens L2 and the third lens L3 is ACT ₂ , the center air gap between the third lens L3 and the fourth lens L4 is ACT ₃ , the center thickness GCT ₃ of the third lens L3 , the edge thickness GET ₃ of the third lens L3, the distance from the nearest point from the image side of the fourth lens L4 to the imaging surface of the image acquisition element 7 and the imaging surface of the image acquisition element 7 is BFL, and the overall optical The focal length EFL of the image lens group satisfies the following relationship: 0.19<BFL/TTL<0.23, 1.2<TTL/EFL<1.5, 0.18<(ACT ₁ +ACT ₂ +ACT ₃ )/EFL<0.45, 0.44<GCT ₃ /GET ₃ <0.74.

In the embodiment of the present invention, the focal length f 1 of the first lens L1, the focal length f ₃ of the _third lens L3, and the focal length EFL of the overall optical imaging lens group satisfy the following relationship: 1.0<EFL/f ₁ < 1.14, 0.26<EFL/ _f3 <0.47.

In the embodiment of the present invention, the curvature radius R3 of the object side surface of the second lens L2 and the curvature radius R4 of the image side surface of the second lens L2 satisfy the following relationship: 0.4<R3/R4<1.1.

In the embodiment of the present invention, the chief ray incident angle CRA of the image acquisition element 7, the half y of the diagonal line of the effective pixel area of the image acquisition element 7, the half w of the overall field of view, and the first The distance TTL from the object side of the lens L1 to the imaging surface of the image acquisition element 7 satisfies the following relationship: 1.5<TTL/y<1.6, 1.2<w/CRA<1.4.

In the embodiment of the present invention, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 all satisfy the following relationship: In the formula, z is the vector height of the aspheric surface, c is the curvature of the aspheric surface, K is the conic coefficient of the quadric surface, r is the radial coordinate of the aspheric surface, A ₄ , A ₆ , A ₈ ... are the four, six, and Eight...Equal-order aspheric coefficients.

In the embodiment of the present invention, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all made of plastic material with a refractive index less than 1.65, and the filter 6 is made of Schott-BK7 material.

In an embodiment of the present invention, an imaging method of a four-piece optical imaging lens with a short lens and a long field of view includes any of the above-mentioned four-piece optical imaging lenses with a short lens and a long field of view , with the following steps:

(1) The light beam enters the first lens L1 through the aperture stop 5, the aperture stop 5 is also the entrance pupil of the imaging lens, the position of the aperture stop 5 is close to the first lens L1, and the first lens L1 The object side of the first lens L1 is convex to ensure a larger viewing angle, and the image side of the first lens L1 is also convex, so that the on-axis beams have a tendency to converge, and the large field of view can also be made larger. The light has a larger exit angle, thereby ensuring a large image height;

(2) The light beam passes through the second lens L2 with high refractive index, wherein the central beam is further converged, and the inflection at the large aperture on the image side of the second lens L2 makes the light rays in the outermost field of view gather, which can effectively control the most Spherical aberration and speckle in the outer field of view;

(3) After the light beam passes through the regular low-refraction third lens L3, the light beams in each field of view are evenly distributed, and the light beams transition smoothly, and the combination of the second lens L2 and the third lens L3 can better correct chromatic aberration;

(4) The light beam converges to the image acquisition element 7 after passing through the fourth lens L4, and the object side and the image side of the fourth lens L4 are W-shaped, which not only ensures that each field of view is on the imaging surface of the image acquisition element 7 The incident angle of the chief ray on the lens is as small as possible, and the field area and distortion aberration are effectively improved.

In Embodiment 1 of the present invention, the following Table 1 lists the optical surface number (Surface Number) in order from the object side to the image side, and the radius of curvature Ri (unit: mm) of the optical surface on the optical axis (The Radius of Curvature R), the distance d _i (unit: mm) between each surface on the optical axis (The on-axis Surface Spacing), the refractive index of each lens (Nd _i ), the Abbe's Number of each lens (Abbe's Number) Vd _i .

Table I

In Embodiment 1 of the present invention, in Table 1, the optical surfaces marked with * are aspherical optical surfaces, R11 and R12 respectively represent the object side and image side of the first lens L1; R21 and R22 represent the second lens respectively The object side and image side of L2; R31 and R32 respectively represent the object side and image side of the third lens L3; R41 and R42 represent the object side and image side of the fourth lens L4 respectively, Fno is the focal length ratio of the optical lens, and EFL is The effective focal length of the orientation lens, 2w is the field angle of the optical orientation lens; the following table two lists the coefficients of the aspheric surface of each optical surface:

Table II

K A4 A6 A8 A10 A12 A14 A16 *R11 2.084E+00 -9.799E-02 -7.519E-01 3.822E+00 -1.440E+01 1.946E+01 3.687E+00 -2.586E+01 *R12 -1.507E+01 -3.250E-01 -8.317E-02 -2.379E-01 -2.140E+00 1.102E+01 -1.837E+01 9.804E+00 *R21 -9.005E+00 -9.588E-01 5.048E-01 7.224E-01 4.789E+00 -1.123E+01 6.081E+00 4.198E-01 *R22 -1.694E+01 1.509E-01 -1.496E+00 1.642E+00 5.548E+00 -1.435E+01 1.313E+01 -4.512E+00 *R31 -1.698E+01 9.131E-01 -2.970E+00 3.875E+00 1.284E-01 -6.414E+00 7.070E+00 -2.536E+00 *R32 -9.227E-01 1.169E-01 1.228E-01 -2.642E-01 1.526E-01 4.185E-02 -3.579E-02 -4.152E-03 *R41 -2.343E+00 -4.366E-01 2.821E-01 -9.734E-02 9.436E-03 7.029E-03 -2.264E-03 1.019E-04 *R42 -8.281E-01 -6.378E-01 5.101E-01 -3.486E-01 1.630E-01 -4.874E-02 8.213E-03 -5.916E-04

In Embodiment 1 of the present invention, the first lens L1 is made of a plastic material with a refractive index _Nd1 of 1.54 and _an Abbe number Vd1 of 55.9; the _second lens L2 is made of a plastic material with a refractive index Nd2 of 1.64 and Abbe The shell number Vd ₂ is made of a plastic material of 22.4; the third lens L3 is made of a plastic material with a refractive index Nd ₃ of 1.54 and an Abbe number Vd ₃ of 55.9; the fourth lens L4 is made of a refractive index Nd ₄ of 1.54, the Abbe number Vd ₄ is made of plastic material of 55.9; the filter 66 is made of BK7-SCHOTT glass material.

In Embodiment 1 of the present invention, the effective focal length of the optical imaging lens is 2.595, the back focal length is 0.794, and the same plastic material is used for the first lens L1, the third lens L3, and the fourth lens L4, which is beneficial to reduce materials and cost. And can achieve a larger image height, the total length of the lens is 3.605, which satisfies: 0.19<BFL/TTL<0.23, 0.18<(ACT ₁ +ACT ₂ +ACT ₃ )/EFL<0.45, 1.5<TTL/y <1.6.

In Embodiment 1 of the present invention, the above materials can prove that the optical imaging lens of the present invention can effectively correct aberrations, making the lens more compact and shortening the total length, thereby improving the applicability of the present invention.

In the second embodiment of the present invention, the following table three lists the optical surface number (Surface Number) in order from the object side to the image side, and the curvature radius Ri (unit: mm) of the optical surface on the optical axis (The Radius ofCurvature R), the distance d _i (unit: mm) between each surface on the optical axis (The on-axis Surface Spacing), the refractive index of each lens (Nd _i ), the Abbe's Number of each lens (Abbe's Number) Vd _i .

Table three

In Embodiment 2 of the present invention, in Table 3, the optical surface (surface) marked with * is an aspheric optical surface, and R11 and R12 respectively represent the object side and image side of the first lens L1; R21 and R22 represent respectively The object side and image side of the second lens L2; R31 and R32 represent the object side and image side of the third lens L3 respectively; R41 and R42 represent the object side and image side of the fourth lens L4 respectively, and Fno is the focal length ratio of the optical lens , EFL is the effective focal length of the orientation lens, 2w is the field angle of the optical orientation lens; the following table 2 lists the coefficients of the aspheric surface of each optical surface:

Table four

K A4 A6 A8 A10 A12 A14 A16 *R11 2.089E+00 -1.010E-01 -7.332E-01 3.882E+00 -1.440E+01 1.901E+01 2.759E+00 -2.273E+01 *R12 -1.502E+01 -3.140E-01 -1.115E-01 -3.029E-01 -2.098E+00 1.143E+01 -1.798E+01 8.154E+00 *R21 -7.351E+00 -9.581E-01 5.290E-01 7.292E-01 4.756E+00 -1.131E+01 6.069E+00 4.462E-01 *R22 -1.557E+01 1.588E-01 -1.502E+00 1.633E+00 5.541E+00 -1.435E+01 1.312E+01 -4.505E+00 *R31 -1.004E+01 9.117E-01 -2.972E+00 3.862E+00 1.242E-01 -6.415E+00 7.074E+00 -2.550E+00 *R32 -8.644E-01 1.158E-01 1.126E-01 -2.706E-01 1.508E-01 4.220E-02 -3.551E-02 -4.267E-03 *R41 -1.654E+00 -4.442E-01 2.764E-01 -9.884E-02 9.152E-03 7.063E-03 -2.202E-03 1.417E-04 *R42 -8.429E-01 -6.490E-01 5.125E-01 -3.494E-01 1.629E-01 -4.871E-02 8.222E-03 -5.902E-04

In the second embodiment of the present invention, the first lens L1 is made of a plastic material with a refractive index _Nd1 of 1.54 and _an Abbe number Vd1 of 55.9; the _second lens L2 is made of a plastic material with a refractive index Nd2 of 1.64 and Abbe The shell number Vd ₂ is made of a plastic material of 22.4; the third lens L3 is made of a plastic material with a refractive index Nd ₃ of 1.54 and an Abbe number Vd ₃ of 55.9; the fourth lens L4 is made of a refractive index Nd ₄ of 1.54, the Abbe number Vd ₄ is made of plastic material of 55.9; the filter 66 is made of BK7-SCHOTT glass material.

In Embodiment 2 of the present invention, the effective focal length of the optical imaging lens is 2.595, and the back focal length is 0.863; the object side R41 is an aspheric surface with an inflection point, and the first lens L1, the third lens L3, and the fourth lens L4 Using the same plastic material is beneficial to reduce material and cost, and can achieve a larger image height. The total length of the lens is 3.654, which satisfies: 0.19<BFL/TTL<0.23, 0.18<(ACT ₁ +ACT ₂ + ACT ₃ )/EFL<0.45, 1.0<EFL/f1<1.14, 0.4<R3/R4<1.1, _1.2 <w/CRA<1.4.

In the second embodiment of the present invention, the above materials can prove that the optical imaging lens of the present invention can effectively correct aberrations, increase the back focus of the lens, reduce the sensitivity of the system, and further improve the applicability of the present invention.

In the third embodiment of the present invention, the following table five lists the optical surface number (Surface Number) in order from the object side to the image side, and the curvature radius Ri (unit: mm) of the optical surface on the optical axis (The Radius of Curvature R), the distance d _i (unit: mm) between each surface on the optical axis (The on-axis Surface Spacing), the refractive index of each lens (Nd _i ), the Abbe's Number of each lens (Abbe's Number) Vd _i .

Table five

In Embodiment 3 of the present invention, in Table 5, the optical surface (Surface) marked with * is an aspheric optical surface, and R11 and R12 respectively represent the object side and image side of the first lens L1; R21 and R22 represent respectively The object side and image side of the second lens L2; R31 and R32 represent the object side and image side of the third lens L3 respectively; R41 and R42 represent the object side and image side of the fourth lens L4 respectively, and Fno is the focal length ratio of the optical lens , EFL is the effective focal length of the orientation lens, 2w is the field angle of the optical orientation lens; the following table six lists the coefficients of the aspheric surface of each optical surface:

Table six

K A4 A6 A8 A10 A12 A14 A16 *R11 2.127E+00 -9.598E-02 -7.557E-01 3.838E+00 -1.437E+01 1.931E+01 3.197E+00 -2.431E+01 *R12 -1.501E+01 -3.072E-01 -9.915E-02 -2.831E-01 -2.162E+00 1.117E+01 -1.823E+01 9.496E+00 *R21 -7.590E+00 -9.455E-01 5.191E-01 6.709E-01 4.719E+00 -1.119E+01 6.340E+00 2.219E-01 *R22 -1.514E+01 1.568E-01 -1.501E+00 1.640E+00 5.547E+00 -1.435E+01 1.312E+01 -4.507E+00 *R31 -1.098E+01 9.340E-01 -2.962E+00 3.863E+00 1.272E-01 -6.410E+00 7.076E+00 -2.555E+00 *R32 -1.005E+00 1.259E-01 1.155E-01 -2.693E-01 1.516E-01 4.264E-02 -3.566E-02 -5.131E-03 *R41 -1.581E+00 -4.404E-01 2.779E-01 -9.860E-02 9.074E-03 7.016E-03 -2.211E-03 1.409E-04 *R42 -8.381E-01 -6.456E-01 5.129E-01 -3.496E-01 1.629E-01 -4.870E-02 8.219E-03 -5.927E-04

In Embodiment 3 of the present invention, the first lens L1 is made of a plastic material with a refractive index _Nd1 of 1.54 and _an Abbe number Vd1 of 55.9; the _second lens L2 is made of a plastic material with a refractive index Nd2 of 1.64 and Abbe The shell number Vd ₂ is made of a plastic material of 22.4; the third lens L3 is made of a plastic material with a refractive index Nd ₃ of 1.54 and an Abbe number Vd ₃ of 55.9; the fourth lens L4 is made of a refractive index Nd ₄ of 1.54, the Abbe number Vd ₄ is made of plastic material of 55.9; the filter 66 is made of BK7-SCHOTT glass material.

In Embodiment 3 of the present invention, the effective focal length of the optical imaging lens is 2.619, and the back focal length is 0.812; the object side R41 is an aspheric surface with an inflection point, and the first lens L1, the third lens L3, and the fourth lens L4 uses the same plastic material to help reduce material and cost, and can achieve a larger image height. The total lens length is 3.638, which satisfies: 0.19<BFL/TTL<0.23, 1.2<TTL/EFL<1.5, 1.5<TTL/y<1.6, 1.0<EFL/f1<1.14, 0.4< _R3 /R4<1.1, 0.26<EFL/ _f3 <0.47, 0.44< _GCT3 / _GET3 <0.74.

In the third embodiment of the present invention, the above-mentioned materials can prove that the optical imaging lens of the present invention can effectively correct aberrations, and the configuration of the lens spacing facilitates assembly, and further shortens the total length of the lens to be suitable for miniaturized electronic devices.

In Embodiment 4 of the present invention, the following Table 7 lists the optical surface number (Surface Number) in order from the object side to the image side, and the radius of curvature Ri (unit: mm) of the optical surface on the optical axis (The Radius of Curvature R), the distance d _i (unit: mm) between each surface on the optical axis (The on-axis Surface Spacing), the refractive index of each lens (Nd _i ), the Abbe's Number of each lens (Abbe's Number) Vd _i .

Table seven

In Embodiment 4 of the present invention, in Table 7, the optical surface (surface) marked with * is an aspheric optical surface, and R11 and R12 represent the object side and image side of the first lens L1 respectively; R21 and R22 represent respectively The object side and image side of the second lens L2; R31 and R32 represent the object side and image side of the third lens L3 respectively; R41 and R42 represent the object side and image side of the fourth lens L4 respectively, and Fno is the focal length ratio of the optical lens , EFL is the effective focal length of orientation lens, and 2w is the angle of view of optical orientation lens; In the embodiment of the present invention four, following table eight lists the coefficients of the aspheric surface of each optical surface:

table eight

In Embodiment 4 of the present invention, the first lens L1 is made of a plastic material with a refractive index _Nd1 of 1.54 and _an Abbe number Vd1 of 55.9; all _second lenses L2 are made of a plastic material with a refractive index Nd2 of 1.64 and an Abbe number Vd1 of 55.9. The number Vd ₂ is made of a plastic material of 22.4; the third lens L3 is made of a plastic material with a refractive index Nd ₃ of 1.54 and an Abbe number Vd ₃ of 55.9; the fourth lens L4 is made of a refractive index Nd ₄ of 1.54 1. Made of plastic material whose Abbe number Vd ₄ is 55.9; the filter 66 is made of BK7-SCHOTT glass material.

In Embodiment 4 of the present invention, the effective focal length of the optical imaging lens is 2.651, and the back focal length is 0.707; the object side R41 is an aspheric surface with an inflection point, and the first lens L1, the third lens L3, and the fourth lens L4 Using the same plastic material is beneficial to reduce materials and cost, and can achieve a larger image height. The total length of the lens is 3.658, which satisfies: 0.19<BFL/TTL<0.23, 1.2<TTL/EFL<1.5, 0.18 <(ACT ₁ +ACT ₂ +ACT ₃ )/EFL<0.45, 1.0<EFL/f ₁ <1.14, 0.4<R3/R4<1.1, 0.26<EFL/f ₃ <0.47, 0.44<GCT ₃ /GET ₃ < 0.74.

In Embodiment 4 of the present invention, the above can prove that the optical imaging lens of the present invention can effectively correct aberrations, so that the lens has a shorter total length and a larger image height, thereby improving the applicability of the present invention.

In Embodiment 5 of the present invention, the following Table 9 lists the optical surface number (SurfaceNumber) in order from the object side to the image side, and the radius of curvature Ri (unit: mm) of the optical surface on the optical axis (The Radius of CurvatureR), the distance between each surface on the optical axis d _i (unit: mm) (The on-axis Surface Spacing), the refractive index of each lens (Nd _i ), the Abbe's Number (Abbe's Number) Vd of each lens _i .

Table nine

In Embodiment 5 of the present invention, in Table 9, the optical surface (Surface) marked with * is an aspheric optical surface, and R11 and R12 represent the object side and image side of the first lens L1 respectively; R21 and R22 represent respectively The object side and image side of the second lens L2; R31 and R32 represent the object side and image side of the third lens L3 respectively; R41 and R42 represent the object side and image side of the fourth lens L4 respectively, and Fno is the focal length ratio of the optical lens , EFL is the effective focal length of the orientation lens, 2w is the field angle of the optical orientation lens; the following table two lists the coefficients of the aspheric surface of each optical surface; the following table ten lists the coefficients of the aspheric surface of each optical surface :

table ten

K A4 A6 A8 A10 A12 A14 A16 *R11 2.345E+00 -1.182E-01 -7.712E-01 3.326E+00 -1.256E+01 2.037E+01 -1.694E+01 3.488E+00 *R12 -3.020E+00 -2.992E-01 -3.272E-01 4.842E-01 -3.007E+00 8.502E+00 -9.520E+00 2.363E+00 *R21 -9.702E+00 -7.187E-01 2.992E-01 5.621E-01 4.542E+00 -1.169E+01 1.131E+01 -4.818E+00 *R22 -1.708E+00 2.690E-01 -1.457E+00 1.597E+00 5.427E+00 -1.436E+01 1.340E+01 -4.773E+00 *R31 1.812E+00 9.791E-01 -2.958E+00 3.716E+00 2.835E-01 -6.258E+00 7.006E+00 -2.636E+00 *R32 4.098E-01 -2.639E-02 1.944E-01 -2.539E-01 1.354E-01 5.308E-02 -6.814E-03 -1.802E-02 *R41 -2.450E+00 -5.032E-01 3.201E-01 -9.826E-02 5.730E-03 6.487E-03 -1.597E-03 5.492E-06 *R42 -8.760E-01 -7.415E-01 5.973E-01 -3.890E-01 1.703E-01 -4.737E-02 7.437E-03 -5.001E-04

In Embodiment 5 of the present invention, the first lens L1 is made of a plastic material with a refractive index _Nd1 of 1.54 and _an Abbe number Vd1 of 55.9; the _second lens L2 is made of a plastic material with a refractive index Nd2 of 1.64 and A The shell number Vd ₂ is made of a plastic material of 22.4; the third lens L3 is made of a plastic material with a refractive index Nd ₃ of 1.54 and an Abbe number Vd ₃ of 55.9; the fourth lens L4 is made of a refractive index Nd ₄ of 1.54, the Abbe number Vd ₄ is made of plastic material of 55.9; the filter 66 is made of BK7-SCHOTT glass material.

In Embodiment 5 of the present invention, the effective focal length of the optical imaging lens is 2.505, and the back focal length is 0.710; the object side R41 is an aspheric surface with an inflection point, and the first lens L1, the third lens L3, and the fourth lens L4 Using the same plastic material is beneficial to reduce materials and cost, and can achieve a larger image height. The total length of the lens is 3.610, which satisfies: 0.19<BFL/TTL<0.23, 1.2<TTL/EFL<1.5, 0.18 <(ACT ₁ +ACT ₂ +ACT ₃ )/EFL<0.45, 1.5<TTL/y<1.6, 1.0<EFL/f ₁ <1.14, 0.4<R3/R4<1.1, 0.26<EFL/f ₃ <0.47, 0.44< _GCT3 / _GET3 <0.74, 1.2<w/CRA<1.4.

In Embodiment 5 of the present invention, the above materials can prove that the optical imaging lens of the present invention can effectively correct aberrations, so that the lens has a shorter total length and a larger image height, thereby improving the applicability of the present invention.

In the spherical aberration graphs shown in Figs. 2, 6, 10, 14, and 18, the ordinate is the longitudinal spherical aberration (Longitudinal Spherical Aber), and the abscissa is the focal length, and the unit is millimeter. It can be seen from the figure that the spherical aberration changes under different focal length offsets.

Figures 3, 7, 11, 15, and 19 show the field curvature (Astigmatic Field Curves) curves. The abscissa indicates the focal length in millimeters; the ordinate indicates the image height (Image) (including tangential and radial), It can be seen from the figure that for different focal length offsets, the field curvature changes caused by different image heights of the optical axis.

Figures 4, 8, 12, 16, and 20 show the imaging distortion (Distortion) curves, the abscissa indicates the percentage of the distortion rate; the ordinate indicates the different image heights (Image HT) on the optical axis, from the figure It can be seen that the twist rate changes at different image heights.

The present invention is not limited to the above-mentioned best implementation mode, and anyone can obtain other various forms of four-piece optical imaging lens with short lens and long field of view and its imaging method under the enlightenment of the present invention. All equivalent changes and modifications made according to the patent scope of the present invention shall fall within the scope of the present invention.

Claims (7)

1. A four-piece optical imaging lens with a short lens and a long field of view is characterized in that: it includes an aperture stop arranged in sequence from the object side to the image side along the optical axis of the lens, and the first diopter with positive diopter A lens L1, a second lens L2 with a negative diopter, a third lens L3 with a positive diopter, a fourth lens L4 with a negative diopter, a filter and an image acquisition element, the first lens L1, the second lens L2 , the third lens L3 and the fourth lens L4 are both aspheric lenses, wherein the object side of the first lens L1 is a convex surface, the image side of the first lens L1 is a concave surface, and the object side of the second lens L2 The image side of the second lens L2 is a concave surface, and the image side of the second lens L2 is curved to the image side at a large aperture, the object side of the third lens L3 is a concave surface, and the image side of the third lens L3 is concave. The image side is convex, the object side and the image side of the fourth lens L4 are W-shaped, and the distance TTL from the object side of the first lens L1 to the imaging surface of the image acquisition element on the optical axis of the lens is TTL. The central air gap between a lens L1 and the second lens L2 is ACT ₁ , the central air gap between the second lens L2 and the third lens L3 is ACT ₂ , and the central air gap between the third lens L3 and the fourth lens L4 is ACT ₃ , the central thickness GCT ₃ of the third lens L3, the edge thickness GET ₃ of the third lens L3, the closest point from the image side of the fourth lens L4 to the imaging surface of the image acquisition element and the image acquisition The distance of the imaging surface of the component is BFL, and the focal length EFL of the overall optical imaging lens group satisfies the following relationship: 0.19<BFL/TTL<0.23, 1.2<TTL/EFL<1.5, 0.18<(ACT ₁ +ACT ₂ +ACT ₃ )/EFL<0.45, 0.44< _GCT3 / _GET3 <0.74. 2. The four-piece optical imaging lens with a short lens and a long field of view according to claim 1, characterized in that: the focal length f ₁ of the first lens L1, the focal length f of the third lens L3 _3. And the focal length EFL of the overall optical imaging lens group satisfies the following relationship: 1.0<EFL/f ₁ <1.14, 0.26<EFL/f ₃ <0.47. 3. The four-piece optical imaging lens with short mirror and long field of view according to claim 1, characterized in that: the radius of curvature R3 of the object side of the second lens L2, the second lens L2 The curvature radius R4 of the image side satisfies the following relationship: 0.4<R3/R4<1.1. 4. The four-piece optical imaging lens with short lens and long field of view according to claim 1, characterized in that: the chief ray incident angle CRA of the image acquisition element, the effective pixel of the image acquisition element Half of the area diagonal y, half of the overall field of view w, and the distance TTL from the object side of the first lens L1 to the imaging surface of the image acquisition element satisfy the following relationship: 1.5<TTL/y<1.6, 1.2< w/CRA<1.4. 5. The four-piece optical imaging lens with short lens and long field of view according to claim 1, characterized in that: the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 all satisfy the following relationship: In the formula, z is the vector height of the aspheric surface, c is the curvature of the aspheric surface, K is the conic coefficient of the quadric surface, r is the radial coordinate of the aspheric surface, A ₄ , A ₆ , A ₈ ... are the four, six, and Eight...Equal-order aspheric coefficients. 6. The four-piece optical imaging lens with a short lens and a long field of view according to claim 1, characterized in that: the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 is made of plastic material with a refractive index less than 1.65, and the filter is made of Schott-BK7 material. 7. An imaging method of a four-piece optical imaging lens with a short mirror and a long field of view, comprising the four-piece optical lens with a short mirror and a long field of view as described in any one of claims 1 to 6. The imaging lens is characterized in that it comprises the following steps: (1) The light beam enters the first lens L1 through the aperture stop, wherein the on-axis light beam passing through the first lens L1 tends to converge, and the light with a large field of view has a larger exit angle; (2) The light beam passes through the second lens L2 with high refractive index, wherein the central beam is further converged, and the inflection at the large aperture on the image side of the second lens L2 makes the light rays in the outermost field of view gather, which can effectively control the most Spherical aberration and speckle in the outer field of view; (3) After the light beams pass through the regular low-refraction third lens L3, the light beams in each field of view are evenly distributed, and the light beams transition smoothly, and the chromatic aberration can be better corrected after the light beams pass through the second lens L2 and the third lens L3; (4) The light beam converges to the image acquisition element after passing through the fourth lens L4. The fourth lens L4 not only ensures that the chief ray incident angle of each field of view on the imaging surface of the image acquisition element is as small as possible, but also effectively improves the field and distortion aberrations.