TWI418874B - Imaging lens - Google Patents

Description

Image capture lens

The present invention relates to imaging technology, and more particularly to an imaging lens.

At present, in order to improve the image quality, the image taking lens often requires a larger number of lenses, resulting in an excessive total length of the image taking lens, which is not conducive to miniaturization.

In view of this, it is necessary to provide an image taking lens which is excellent in image quality and small in size.

An image taking lens includes, in order from the object side to the image side, a first lens group having a negative power, a second lens group having a positive power and a moving arrangement, and a third lens group having a positive power. The first lens group includes a first lens having a negative power close to the object side and a second lens having a positive power near the image side. The second lens group includes a third lens having a positive power near the object side and a fourth lens having a positive power near the image side. The third lens group includes a fifth lens having a positive power near the image side. The image taking lens satisfies the following conditional expression: 2.1≦Lw/(α*Y)<2.5;1.9≦|Fp1/F1|≦2.2; 0.6≦|Fp2/F2|≦0.7; Where Lw is the total optical length of the image taking lens at the wide angle end, α is the ratio of the effective focal length of the image capturing lens at the telephoto end to the effective focal length of the wide angle end, Y is the maximum image height, and Fp1 is the effective focal length of the second lens, Fp2 For the effective focal length of the fourth lens, F1 is the effective focal length of the first lens group, and F2 is the effective focal length of the second lens group.

The above condition is such that the image taking lens has a zoom ratio of about four times (by changing the position of the second lens group), not only the image quality but also the miniaturization.

10‧‧‧Image lens

100‧‧‧First lens group

102‧‧‧ first lens

104‧‧‧second lens

130‧‧‧ imaging surface

150‧‧‧Infrared filter

160‧‧‧glass cover

200‧‧‧second lens group

202‧‧‧ third lens

204‧‧‧Fourth lens

300‧‧‧third lens group

303‧‧‧ fifth lens

400‧‧‧Light

S1‧‧‧ first surface

S2‧‧‧ second surface

S3‧‧‧ third surface

S4‧‧‧ fourth surface

S5‧‧‧ fifth surface

S6‧‧‧ sixth surface

S7‧‧‧ seventh surface

S8‧‧‧ eighth surface

S9‧‧‧ ninth surface

S10‧‧‧ tenth surface

S11‧‧‧ eleventh surface

S12‧‧‧ twelfth surface

S13‧‧‧ thirteenth surface

S14‧‧‧ fourteenth surface

1 is a schematic view showing the optical structure of an image taking lens at a wide angle end according to a preferred embodiment of the present invention.

2 is a schematic view showing the optical structure of the image taking lens of FIG. 1 at the telephoto end.

3 is a graph showing spherical aberration characteristics at the wide angle end of the image taking lens of FIG. 1.

4 is a graph showing a field curvature characteristic of the image taking lens of FIG. 1 at a wide angle end.

FIG. 5 is a distortion characteristic diagram of the image taking lens of FIG. 1 at a wide angle end. FIG.

Fig. 6 is a graph showing lateral chromatic aberration characteristics at the wide angle end of the image taking lens of Fig. 1.

Fig. 7 is a graph showing the spherical aberration characteristic at the telephoto end of the image taking lens of Fig. 1.

Figure 8 is a graph showing the field curvature characteristics of the image taking lens of Figure 1 at the telephoto end.

FIG. 9 is a distortion characteristic diagram of the image taking lens of FIG. 1 at the telephoto end.

Fig. 10 is a graph showing the lateral chromatic aberration characteristic at the telephoto end of the image taking lens of Fig. 1.

The following preferred embodiments will be described in detail below with reference to the accompanying drawings. .

Referring to FIG. 1 and FIG. 2, the image taking lens 10 according to the preferred embodiment of the present invention includes a first lens group 100 having a negative refractive power and a moving power setting from the object side to the image side. The second lens group 200 and a third lens group 300 having positive power.

The first lens group 100 includes a first lens 102 having a negative power close to the object side and a second lens 104 having a positive power near the image side. The first lens 102 includes a first surface S1 facing the object side and having a positive refractive power, and a second surface S2 having a negative refractive power facing the image side. The second lens 104 includes a third surface S3 facing the object side with a positive power and a fourth surface S4 facing the image side and having a negative power.

The second lens group 200 includes a third lens 202 having a positive power near the object side and a fourth lens 204 having a positive power near the image side. The third lens 202 includes a fifth surface S5 having a positive refractive power facing the object side and a sixth surface S6 having a positive refractive power facing the image side. The fourth lens 204 includes a seventh surface S7 having a positive refractive power facing the object side and an eighth surface S8 having a negative refractive power facing the image side.

The third lens group 300 includes a fifth lens 303 having a positive power near the image side. The fifth lens 303 includes a ninth surface S9 having a positive refractive power facing the object side and a tenth surface S10 having a positive refractive power facing the image side.

When the image capturing lens 10 is imaged, the light is incident from the object side, and sequentially passes through the first lens group 100, the second lens group 200, and the third lens group 300 to be concentrated (imaged) on an image forming surface 130. An image sensing device can be constructed by providing a light sensing element at the imaging surface 130.

In order to reduce the length of the entire image taking lens 10 and to ensure various optical properties of the lens The image pickup lens 10 satisfies the following three conditional expressions: (1) 2.1 ≦ Lw / (α * Y) < 2.5.

Where Lw is the total optical length of the image taking lens at the wide angle end, and α is the zoom ratio (that is, the ratio of the effective focal length of the image taking lens 10 at the telephoto end to the effective focal length at the wide angle end), and Y is the maximum image height.

When the ratio of Lw/(α*Y) is too small, the aberration is hard to be corrected, and if the ratio is too large, the total length of the image taking lens 10 is large. Therefore, the conditional expression (1) limits the overall length of the entire image taking lens 10 while ensuring that the aberration can be corrected.

(2) 1.9 ≦ | Fp1/F1|≦2.2.

Wherein Fp1 is the effective focal length of the second lens, and F1 is the effective focal length of the first lens group.

The ratio of |Fp1/F1| is too small, the field curvature becomes large, the ratio is too large, and the astigmatism becomes severe, which affects the resolution. Therefore, the conditional expression (2) ensures that the field curvature and the astigmatism of the image taking lens 10 are kept within an appropriate range.

(3) 0.6≦|Fp2/F2|≦0.7.

Wherein, Fp2 is the effective focal length of the fourth lens, and F2 is the effective focal length of the second lens group.

The ratio of |Fp2/F2| is too small, the astigmatism is severe, the ratio is too large, and the color difference between field curvature and edge field of view becomes severe. Therefore, the conditional expression (3) ensures that the astigmatism of the image taking lens 10, the field curvature, and the chromatic aberration of the edge field of view are kept within an appropriate range.

During the zooming of the image taking lens 10 from the wide-angle end to the telephoto end, the interval between the first lens group 100 and the second lens group 200 is reduced, and the interval between the second lens group 200 and the third lens group 300 is increased. To achieve variable magnification.

Preferably, the image taking lens 10 also satisfies the following two conditional expressions: (4) 0.65 < M2 / Ft < 0.76; (5) 0.25 < L12t / Ft < 0.3.

Wherein, M2 is the maximum movement amount of the second lens group 200 along the optical axis when the image taking lens 10 is from the wide angle end to the telephoto end, and L12t is the first lens 102 of the first lens group 100 when the image taking lens 10 is at the telephoto end. The distance from the optical axis to the surface of the third lens 202 of the second lens group 200 closest to the object side near the image side. Ft is the effective focal length of the image taking lens 10 at the telephoto end.

When the two ratios in the conditional expressions (4) and (5) are too small, the total length of the image taking lens 10 is too long, and if it is too large, the resolution quality is lowered. Therefore, the conditional expressions (4) and (5) are used to balance the total length, zoom ratio, and resolution quality of the image taking lens 10.

Preferably, the image taking lens 10 further includes an aperture stop 400 disposed between the second lens group 200 and the third lens group 300 and adjacent to the second lens group 200, and disposed on the third lens group 300 and The infrared filter 150 and the glass cover 160 between the imaging faces 130. The aperture 400 moves with the second lens group 200. The infrared filter 150 includes an eleventh surface S11 facing the object side and a twelfth surface S12 facing the image side. The cover glass 160 includes a thirteenth surface S13 facing the object side and a fourteenth surface S14 facing the image side.

Preferably, the first lens group 100, the second lens group 200, and the third lens group 300 are all made of glass, which is convenient for eliminating the image quality of the aberration lifting image taking lens 10. At the same time, the image capturing lens 10 has a strong adaptability to the environment and can withstand higher ambient temperatures.

The image taking lens 10 will be further described below in conjunction with the attached table. Wherein, the "distance" is an on-axis distance from the surface to the latter surface (the length of the optical axis of the two surfaces is cut). The distance and the radius of curvature are in millimeters. The image taking lens 10 in the present embodiment satisfies the conditions listed in Tables 1 to 3.

Table 1

The aspherical coefficients of the second lens 104 and the third lens 202 are listed in Table 2.

Table 2

Among them, the aspherical surface can be expressed by the following formula:

Where z is the displacement value of the surface apex as the reference distance from the optical axis along the optical axis direction, c is the radius of curvature, h is the lens height, K is the conical constant (Coin Constant), A, B, C, D, E, F, and G are the aspheric coefficients of four, six, eight, ten, twelve, fourteen, and sixteen, respectively.

When the image taking lens 10 is located at the wide-angle end and the telephoto end, the distance between the respective lens groups is as shown in Table 3.

table 3

Where f is the effective focal length of the image taking lens 10. D4 is the distance between the first lens group 100 and the second lens group 200, that is, the distance between the fourth surface S4 and the fifth surface S5 on the optical axis. D9 is the distance between the second lens group 200 and the third lens group 300, that is, the distance between the surface of the aperture 400 near the third lens group 300 and the ninth surface S9. D11 is the distance between the third lens group 300 and the infrared filter 150. That is, the distance between the tenth surface S10 and the eleventh surface S11.

The spherical aberration characteristic curve, the field curvature characteristic curve, the distortion characteristic curve, and the lateral chromatic aberration characteristic curve of the image taking lens 10 of the present embodiment at the wide-angle end and the telephoto end are as shown in FIGS. 2 to 9, respectively. Among them, curves a, b, c, d, and e represent characteristic curves of light having wavelengths of 436 nm, 486 nm, 546 nm, 588 nm, and 656 nm, respectively. As can be seen from FIG. 2 and FIG. 6, the spherical aberration generated by the image taking lens 10 for visible light (400-700 nm) is controlled between -0.2 mm and 0.2 mm. It can be seen from the tangential field curvature characteristic curve t and the sagittal field curvature characteristic s in FIGS. 3 and 7, that the meridional field curvature and the sagittal field curvature of the image taking lens 10 are controlled at -0.2. Between mm and 0.2 mm. As can be seen from Fig. 4 and Fig. 8, the distortion of the image taking lens 10 is controlled between -14% and 14%. As can be seen from Fig. 5 and Fig. 9, the lateral chromatic aberration of the image taking lens 10 is controlled between -5 μm and 5 μm. It can be seen that the aberration, curvature of field, distortion and chromatic aberration of the image taking lens 10 can be well corrected.

It should be understood by those skilled in the art that the above embodiments are merely illustrative of the invention and are not intended to limit the invention as long as the invention Appropriate changes and modifications of the above embodiments are intended to fall within the scope of the invention.

10‧‧‧Image lens

100‧‧‧First lens group

102‧‧‧ first lens

104‧‧‧second lens

130‧‧‧ imaging surface

150‧‧‧Infrared filter

160‧‧‧glass cover

200‧‧‧second lens group

202‧‧‧ third lens

204‧‧‧Fourth lens

300‧‧‧third lens group

303‧‧‧ fifth lens

400‧‧‧Light

S1‧‧‧ first surface

S2‧‧‧ second surface

S3‧‧‧ third surface

S4‧‧‧ fourth surface

S5‧‧‧ fifth surface

S6‧‧‧ sixth surface

S7‧‧‧ seventh surface

S8‧‧‧ eighth surface

S9‧‧‧ ninth surface

S10‧‧‧ tenth surface

S11‧‧‧ eleventh surface

S12‧‧‧ twelfth surface

S13‧‧‧ thirteenth surface

S14‧‧‧ fourteenth surface

Claims (8)

An image capturing lens includes, in order from the object side to the image side, a first lens group having a negative power, a second lens group having a positive power and a moving arrangement, and a third lens group having a positive power. The first lens group includes a first lens having a negative power near the object side and a second lens having a positive power near the image side; the second lens group includes a proximity side a third lens having a positive refractive power and a fourth lens having a positive power near the image side; the third lens group including a fifth lens having a positive power near the image side; the image capturing The lens satisfies the following conditional formula: 2.1≦Lw/(α *Y)<2.5;1.9≦|Fp1/F1|≦2.2;0.6≦|Fp2/F2|≦0.7; where Lw is the optical at the wide-angle end of the image taking lens The total length, α is the ratio of the effective focal length of the image taking lens at the telephoto end to the effective focal length at the wide angle end, Y is the maximum image height, Fp1 is the effective focal length of the second lens, Fp2 is the effective focal length of the fourth lens, and F1 is the first The effective focal length of the lens group, F2 is the effective focal length of the second lens group. The image taking lens of claim 1, wherein the distance between the first lens group and the second lens group is reduced during zooming of the image capturing lens from the wide-angle end to the telephoto end, The interval between the second lens group and the third lens group increases. The image taking lens of claim 1, wherein the image capturing lens further satisfies a conditional expression: 0.65 < M2 / Ft < 0.76; 0.25 < L12t / Ft < 0.3; wherein M2 is the image capturing lens The maximum amount of movement of the second lens group along the optical axis from the wide-angle end to the telephoto end, L12t is the surface of the first lens group closest to the image side along the optical axis when the image taking lens is at the telephoto end The distance of the third lens of the second lens group closest to the surface of the object side, and Ft is the effective focal length of the image taking lens at the telephoto end. The image taking lens of claim 1, wherein the first lens includes a first surface facing the object side and having a positive refractive power, and a second surface having a negative refractive power facing the image side. The second lens includes a third surface facing the object side with a positive power and a fourth surface facing the image side and having a negative power. The image taking lens of claim 1, wherein the third lens comprises a fifth surface facing the object side with a positive power and a sixth surface facing the image side with a positive power The fourth lens includes a seventh surface facing the object side with a positive power and an eighth surface facing the image side with a negative power. The image taking lens of claim 1, wherein the fifth lens includes a ninth surface facing the object side with a positive power and a tenth surface facing the image side with a positive power . The image capturing lens of claim 1, wherein the image taking lens further comprises an aperture disposed between the second lens group and the third lens group and adjacent to the second lens group, and An infrared filter and a glass cover disposed between the third lens and the imaging surface. The imaging lens of claim 1, wherein the first lens group, the second lens group, and the third lens group are both made of glass.