TWI390246B - Zoom lens - Google Patents

Description

Zoom lens

The present invention relates to an optical technique, and more particularly to a zoom lens for an imaging device.

In recent years, network cameras have been widely used in military defense, police patrol and home security. The high performance of network cameras has gradually improved. With the development trend of digital cameras and miniaturization, the use of network cameras The zoom lens also needs to be developed in the direction of miniaturization.

In view of this, it is necessary to provide a miniaturized zoom lens.

A zoom lens includes, in order from the object side to the image side, a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, and one having The fourth lens group of positive power. The zoom lens satisfies the following conditions: 12<TTL/FW<16 and 6<F1/F<8, wherein TTL is the overall length of the zoom lens, and FW is the focal length of the zoom lens at the wide-angle end state, F For the focal length of the entire zoom lens, F1 is the focal length of the first lens group.

The conditional expressions <T/FW<16 and 6<F1/F<8 can realize miniaturization of the entire zoom lens.

The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

Please refer to FIG. 1 , FIG. 2 and FIG. 3 , which are zoom lens 100 according to an embodiment of the present invention. The zoom lens 100 includes, in order from the object side to the image side, a first lens group 10 having positive power, a second lens group 20 having negative power, and a third lens group 30 having positive power. And a fourth lens group 40 having positive power.

The zoom lens 100 further includes a light reduction sheet 50, a diaphragm 60, an infrared cut filter 70, a glass sheet 80, and an image plane 90. The light reduction sheet 50 is located between the second lens group 20 and the third lens group 30, and is used when the brightness is too high to reduce the amount of light incident. The aperture 60 is located between the light reducing sheet 50 and the third lens group 30. The infrared cut filter 70 is located between the third lens group 30 and the fourth lens group 40. The glass sheet 80 is disposed between the infrared cut filter 70 and the image forming surface 90 for preventing the image forming surface 90 from being contaminated by dust.

The first lens group 10 includes, in order from the object side to the image side, a first lens 11 having a negative power, a second lens 12 having a positive power, and a third lens 13 having a positive power. The first lens 11 and the second lens 12 are bonded together to form a cemented lens to improve the chromatic aberration generated by the light passing through the zoom lens 100. The first lens 11, the second lens 12 and the third lens 13 are all spherical lenses. .

The second lens group 20 includes, in order from the object side to the image side, a fourth lens 21 having a negative refractive power, a fifth lens 22 having a negative refractive power, a sixth lens 23 having a positive refractive power, and a A seventh lens 24 having positive power. The seventh lens 24 and the sixth lens 23 are bonded together to form a cemented lens to improve the chromatic aberration generated by the light passing through the zoom lens 100, and the fourth lens 21, the fifth lens 22, the sixth lens 23, and the seventh lens are transparent. The mirrors 24 are all spherical lenses.

The third lens group 30 includes, in order from the object side to the image side, an eighth lens 31 having positive power, a ninth lens 32 having positive power, and a tenth lens 33 having negative power. The tenth lens 33 and the ninth lens 32 are bonded together to form a cemented lens to improve the chromatic aberration generated by the light passing through the zoom lens 100. The object side surface of the eighth lens 31 and the image side surface of the eighth lens 31 are Aspherical, other lenses are spherical lenses.

The fourth lens group 40 includes, in order from the object side to the image side, an eleventh lens 41 having positive refractive power, a twelfth lens 42 having negative refractive power, and a thirteenth lens 43 having positive refractive power. . The twelfth lens 42 and the eleventh lens 41 are bonded together to form a cemented lens to improve the chromatic aberration generated by the light passing through the zoom lens 100, the object side surface of the thirteenth lens 43 and the thirteenth lens 43. The image side surface is aspherical, and the other lenses are spherical lenses.

When the zoom lens 100 is used for imaging, light from a subject is incident on the zoom lens 100 from the object side direction and sequentially passes through the first lens group 10, the second lens group 20, the third lens group 30, and the fourth lens group. 40. Finally, the image is collected on the image side, and an image sensing device such as a CCD or a CMOS is disposed on the imaging surface 90 to acquire an image of the object. When the zoom lens 100 is zoomed, movement of the second lens group 20 and the fourth lens group 40 on the optical axis is performed.

In order to achieve miniaturization, the zoom lens 100 satisfies the following conditional formula: (1) 12 < TTL / FW < 16, (2) 6 < F1/F < 8.

The TTL is the overall length of the zoom lens 100, FW is the focal length of the zoom lens 100 at the wide-angle end state, F is the focal length of the entire zoom lens 100, and F1 is the focal length of the first lens group 10.

The conditional expression (1) 12 < TTL / FW < 16 ensures that the overall length of the zoom lens 100 is small; the conditional expression (2) limits the first lens group 10 to a positive power lens, and ensures the optical focus of the first lens group 10 The ratio of the degree in the zoom lens 100 is such that the zoom lens 100 has an appropriate back focus, and the conditional expression (1) and the conditional expression (2) can effectively control the miniaturization of the zoom lens 100.

The zoom lens 100 further satisfies the following condition: (3) 30 < (v2 - v1) < 60, wherein v1 and v2 are the Abbe numbers of the first lens 11 and the second lens 12, and the conditional expression is satisfied to effectively correct the system color difference. .

(4)-3<[ra+rb/ra-rb]<-1, where ra is the radius of curvature of the object side surface of the third lens 13, and rb is the radius of curvature of the image side surface of the third lens 13, which is It is necessary to control the spherical aberration at the far end. If it is larger than the upper limit of the condition, it will increase the amount of excessive spherical aberration. If it is less than the lower limit of the condition, it will increase the amount of excessive negative spherical aberration.

The eighth lens 31 and the thirteenth lens 43 are both aspherical lenses, and the surface of the lens surface is the origin, and the optical axis is the x-axis, and the surface thereof satisfies the aspherical surface type calculation formula:

among them, For the height from the optical axis x to the lens surface, the k-type quadric surface coefficient, A _i is the a-plane surface coefficient of the i-th order. Σ A _i h ⁱ indicates the accumulation of Aihi, where i is a natural number.

The zoom lens 100 will be further described below in conjunction with the attached table. Wherein F: system focal length of the zoom lens 100; FNO: F (aperture) number; 2 ω: field of view angle. D5 is an on-axis distance from the image side surface of the third lens 13 to the object side surface of the fourth lens 21, and D12 is an on-axis distance from the image side surface of the seventh lens 24 to the object side surface of the light reduction sheet 50. D21 is the on-axis distance from the image side surface of the infrared cut filter 70 to the object side surface of the eleventh lens 41, and D26 is the axis of the thirteenth lens 43 from the image side surface to the side surface of the glass sheet 80. distance.

Embodiment 1

Each optical element of the zoom lens 100 of the first embodiment satisfies the conditions listed in Tables 1 to 4.

In the zoom lens 100, aberration characteristics at the wide angle end, the intermediate end, and the telephoto end are as shown in FIGS. 4 to 12, respectively. When the zoom lens 100 is at the wide-angle end, both S (meridian curvature value) and T (sagittal curvature value) in FIG. 4 are controlled. In the range of (-0.05mm, 0.05mm), the distortion rate in Fig. 5 is controlled in the range of (-5%, 5%), and the spherical aberration in Fig. 6 is controlled in the range of (-0.05mm, 0.05mm); When the zoom lens 100 is at the intermediate end, the S (meridian curvature value) and the T (satellite curvature value) in Fig. 7 are both controlled within the range of (-20 μm, 20 μm), and the distortion rate in Fig. 8 is controlled at (-0.5). In the range of %, 0.5%), the spherical aberration in Fig. 9 is controlled in the range of (-0.01 mm, 0.01 mm); when the zoom lens 100 is at the telephoto end, S (meridian curvature value) and T (arc) in Fig. 10 The field curvature values are controlled in the range of (-0.05mm, 0.05mm), the distortion rate in Fig. 11 is controlled in the range of (-1%, 1%), and the spherical aberration in Fig. 12 is controlled at (-0.01mm, Within 0.01mm). It can be seen that the field curvature, distortion and spherical aberration of the zoom lens 100 at the wide-angle end, the intermediate end and the telephoto end can be well corrected.

Embodiment 2

Each optical element of the zoom lens 100 of the second embodiment satisfies the conditions listed in Tables 5 to 8.

In the zoom lens 100, aberration characteristics at the wide angle end, the intermediate end, and the telephoto end are as shown in FIGS. 13 to 21, respectively. The zoom lens 100 is wide At the angular end, the S (meridian curvature value) and T (the radial field curvature value) in Fig. 13 are both controlled within the range of (-20 μm, 20 μm), and the distortion rate in Fig. 14 is controlled at (-5%, 5%). In the range, the spherical aberration in Fig. 15 is controlled within the range of (-0.05 mm, 0.05 mm); when the zoom lens 100 is at the intermediate end, S (mercury curvature value) and T (sagittal curvature value) in Fig. 16 Both are controlled within the range of (-20 μm, 20 μm), the distortion rate in Fig. 17 is controlled in the range of (-0.2%, 0.2%), and the spherical aberration in Fig. 18 is controlled in the range of (-0.01 mm, 0.01 mm); When the zoom lens 100 is at the telephoto end, the S (meridian curvature value) and the T (satellite curvature value) in FIG. 19 are both controlled within the range of (-20 μm, 20 μm), and the distortion rate in FIG. 20 is controlled at (-0.2). In the range of %, 0.2%), the spherical aberration in Fig. 21 is controlled within the range of (-0.01mm, 0.01mm); thus, the field curvature, distortion and spherical aberration of the zoom lens 100 at the wide-angle end, the intermediate end and the telephoto end are visible. Both can be well corrected.

The zoom lens of the present invention satisfies the conditional expressions 12<TTL/FW<16 and 6<F1/F<8, so that the zoom lens can be miniaturized; in addition, the zoom lens satisfies the conditional expression 30<(v2- V1) <60 and -3<[(ra+rb)/(ra-rb)]<-1, so that the system color difference and spherical aberration can be effectively corrected, thereby having a good imaging effect.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiments, and equivalent modifications or variations made by those skilled in the art in light of the spirit of the present invention are It should be covered by the following patent application.

100‧‧‧ zoom lens

10‧‧‧First lens group

11‧‧‧First lens

12‧‧‧second lens

13‧‧‧ third lens

20‧‧‧second lens group

21‧‧‧Fourth lens

22‧‧‧ fifth lens

23‧‧‧ sixth lens

24‧‧‧ seventh lens

30‧‧‧third lens group

31‧‧‧ eighth lens

32‧‧‧ ninth lens

33‧‧‧11th lens

40‧‧‧Fourth lens group

41‧‧‧ eleventh lens

42‧‧‧ twelfth lens

43‧‧‧13th lens

50‧‧‧Densors

60‧‧‧Light

70‧‧‧Infrared cut filter

80‧‧‧Stainless glass

90‧‧‧ imaging surface

FIG. 1 is a schematic structural view of a zoom lens provided at a wide angle end according to the present invention.

FIG. 2 is a schematic structural view of a zoom lens provided at an intermediate end according to the present invention.

FIG. 3 is a schematic structural view of a zoom lens provided at a telephoto end according to the present invention.

4 is a graph showing field curvature characteristics of the zoom lens of the first embodiment at a wide angle end.

Fig. 5 is a graph showing the distortion characteristic of the zoom lens of the first embodiment at the wide angle end.

Fig. 6 is a graph showing spherical aberration characteristics at the wide angle end of the zoom lens of the first embodiment.

Fig. 7 is a graph showing the field curvature characteristics of the zoom lens of the first embodiment at the intermediate end.

Fig. 8 is a graph showing the distortion characteristic of the zoom lens of the first embodiment at the intermediate end.

Fig. 9 is a graph showing spherical aberration characteristics at the intermediate end of the zoom lens of the first embodiment.

Fig. 10 is a graph showing the field curvature characteristics of the zoom lens of the first embodiment at the telephoto end.

Fig. 11 is a graph showing the distortion characteristic of the zoom lens of the first embodiment at the telephoto end.

Fig. 12 is a graph showing spherical aberration characteristics of the zoom lens of the first embodiment at the telephoto end.

FIG. 13 is a field curvature characteristic of the zoom lens of the second embodiment at the wide angle end. line graph.

Fig. 14 is a graph showing distortion characteristics of the zoom lens of the second embodiment at the wide angle end.

Fig. 15 is a graph showing spherical aberration characteristics at the wide angle end of the zoom lens of the second embodiment.

Fig. 16 is a graph showing the field curvature characteristics of the zoom lens of the second embodiment at the intermediate end.

Fig. 17 is a graph showing the distortion characteristic of the zoom lens of the second embodiment at the intermediate end.

Fig. 18 is a graph showing spherical aberration characteristics at the intermediate end of the zoom lens of the second embodiment.

Fig. 19 is a graph showing the field curvature characteristics of the zoom lens of the second embodiment at the telephoto end.

Fig. 20 is a graph showing the distortion characteristic of the zoom lens of the second embodiment at the telephoto end.

Fig. 21 is a graph showing spherical aberration characteristics of the zoom lens of the second embodiment at the telephoto end.

100‧‧‧ zoom lens

10‧‧‧First lens group

11‧‧‧First lens

12‧‧‧second lens

13‧‧‧ third lens

20‧‧‧second lens group

21‧‧‧Fourth lens

22‧‧‧ fifth lens

23‧‧‧ sixth lens

24‧‧‧ seventh lens

30‧‧‧third lens group

31‧‧‧ eighth lens

32‧‧‧ ninth lens

33‧‧‧11th lens

40‧‧‧Fourth lens group

41‧‧‧ eleventh lens

42‧‧‧ twelfth lens

43‧‧‧13th lens

50‧‧‧Densors

60‧‧‧Light

70‧‧‧Infrared cut filter

80‧‧‧Stainless glass

90‧‧‧ imaging surface

Claims (10)

A zoom lens includes, in order from the object side to the image side, a first lens group having positive power, a second lens group having negative power, a third lens group having positive power, and one having a fourth lens group of positive power, the zoom lens satisfies the following conditions: 12 < TTL / FW < 16 and 6 < F1/F < 8, wherein TTL is the overall length of the zoom lens, and FW is the zoom The focal length of the lens in the wide-angle end state, F is the focal length of the entire zoom lens, and F1 is the focal length of the first lens group. The zoom lens according to claim 1, wherein the first lens group includes, in order from the object side to the image side, a first lens having a negative refractive power, a second lens having a positive refractive power, and A third lens having positive power, the first lens, the second lens and the third lens are spherical lenses. The zoom lens of claim 2, wherein the zoom lens satisfies the following condition: 30 < (v2-v1) < 60, wherein v1 and v2 are the first lens and the second lens, respectively Abbe number. The zoom lens according to the second aspect of the invention, wherein the zoom lens satisfies the following condition: -3<[(ra+rb)/(ra-rb)]<-1, wherein ra is the third The radius of curvature of the object side surface of the lens, rb is the radius of curvature of the image side surface of the third lens. The zoom lens according to claim 1, wherein the second lens group includes, in order from the object side to the image side, a fourth lens having a negative refractive power and a fifth lens having a negative refractive power. a sixth lens having positive power and a seventh lens having positive power, wherein the fourth lens, the fifth lens, the sixth lens, and the seventh lens are spherical lenses. The zoom lens according to claim 1, wherein the third lens group includes, in order from the object side to the image side, an eighth lens having positive power, a ninth lens having positive power, and a A tenth lens having negative power, at least one surface of the eighth lens is aspherical, and the other lenses are spherical lenses. The zoom lens according to claim 1, wherein the fourth lens group includes, in order from the object side to the image side, an eleventh lens having a positive power and a twelfth having a negative power. A lens and a thirteenth lens having positive power, the thirteenth lens has at least one surface aspherical, and the other lenses are spherical lenses. The zoom lens according to claim 1, wherein the zoom lens includes a detachable infrared cut filter disposed between the third lens group and the fourth lens group. The zoom lens according to claim 1, wherein the zoom lens includes a detachable light reduction sheet disposed between the second lens group and the third lens group. The zoom lens according to claim 9, wherein the zoom lens includes an aperture between the light reduction sheet and the third lens group.