TWI426293B - Lens system - Google Patents

Description

Lens system

The present invention relates to an optical technology, and more particularly to a lens system.

In recent years, with the development of multimedia, there is an increasing demand for digital products such as solid-state imaging devices such as CCD (Charged Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) as imaging elements. This increase in demand itself requires further miniaturization of the lens system.

On the other hand, due to the improved process technology of these solid-state imaging devices such as CCD or CMOS, imaging devices having a size of only a few micrometers per pixel have been fabricated. Previous lens systems have aberrations when the zoom ratio is high. Correction becomes difficult so that the lens system is poor in quality while satisfying miniaturization.

In view of this, it is necessary to provide a lens system that satisfies miniaturization while having good imaging quality.

A lens system includes a first lens of positive power, a second lens of negative power, a third lens of positive power, and a positive power of a positive power along the optical axis from the object side to the image side The fourth lens and an imaging surface. The lens system satisfies the conditional formula D/L>1.18; L/T2>14, where D is the diameter of the effective imaging range of the lens system; L is the total length of the lens system; and T2 is the on-axis thickness of the second lens.

In the above lens system, when the above two conditional expressions are satisfied, the lens system has a small height, and the distance from the first side of the lens to the imaging surface (ie, the total length of the lens system) is shorter, thereby satisfying the lens system. Miniaturization requirements while ensuring image quality.

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

Please refer to FIG. 1, which is a lens system 100 provided by the present invention. Along the optical axis of the lens system 100, a first lens 10 of positive refractive power, a pupil 50, a second lens 20 of negative optical power, and a third positive refractive power are sequentially arranged from the object side to the image side direction. The lens 30, a fourth lens 40 of positive power, a filter 60 and an imaging surface 70.

When the lens system 100 is used for imaging, light from a subject is incident on the lens system 100 from the object side direction and sequentially passes through the first lens 10, the aperture 50, the second lens 20, and the third lens 30. And the fourth lens 40 is finally collected by the filter 60 onto the imaging surface 70. By placing a solid imaging device such as a CCD or a CMOS on the imaging surface 70, the image of the object can be acquired. .

In order to achieve low height and low spherical aberration of the entire lens system 100, the lens system 100 satisfies the following conditional formula:

(1) D/L>1.18; and

(2) L/T2>14,

Where D is the diameter of the effective imaging range of the lens system 100; L is the total length of the lens system 100; and T2 is the on-axis thickness of the second lens 20. In the case where the conditional expressions (1) and (2) are satisfied, the lens system 100 has a small height, and the distance from the first face of the lens to the imaging surface (ie, the total length of the lens system 100) is shorter, thereby satisfying The lens system 100 is miniaturized while ensuring image quality.

Preferably, the first lens 10 satisfies the conditional expression:

(3) 0.25<F/G1R1<0.45; and

(4) νd1>50,

Where F is the total focal length of the lens system 100; G1R1 is the radius of curvature of the surface of the first lens 10 near the object side. Νd1 is the Abbe number of the first lens 10. Conditional formula (3) can reduce spherical aberration, coma, and the like. Conditional expression (4) ensures that after the light passes through the first lens 10, the dispersion is light and the axial chromatic aberration can be reduced.

Preferably, the second lens 20 satisfies the conditional expression:

(5) νd2<32; and

(6) -1.5<F2/F<-0.9,

Where νd2 is the Abbe number of the second lens 20. F2 is the focal length of the second lens 20; F is the total focal length of the lens system 100. Conditional expression (5) ensures that after the light passes through the second lens 20, the dispersion is light and the axial chromatic aberration can be reduced. The conditional expression (6) can ensure the ratio of the power of the second lens 20 in the lens system 100, and can reduce the spherical aberration and the coma.

Preferably, the third lens 30 satisfies the conditional expression:

(7) -1<G3R1/F<-0.5<G3R2/F<-0.15,

Wherein, G3R1 is a radius of curvature of a surface of the third lens 30 close to the object side; and G3R2 is a radius of curvature of a surface of the third lens 30 close to the image side. In this way, the spherical aberration, coma, and the like can be reduced, and the imaging quality of the lens system 100 is greatly improved.

The aperture 50 is located between the first lens 10 and the second lens 20 to limit the light flux passing through the first lens 10 into the second lens 20, and allows the light cone after passing through the first lens 10 to be more Symmetry, the coma of the lens system 100 is corrected. Preferably, the aperture 50 is disposed on a surface of the first lens 10 near the image side, thereby reducing the number of components of the lens system 100 and reducing the complexity of assembly of the lens system 100. In actual operation, a peripheral annular region on the surface of the first lens 10 near the image side may be directly blacked out as the aperture 50. The filter 60 is located between the fourth lens 40 and the imaging surface 70, and is mainly used for filtering light in the infrared band entering the light of the lens system 100.

2 to 10, the lens system 100 of the present invention will be described in detail by way of specific embodiments.

In each of the following embodiments, the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 are all aspherical lenses. In this way, spherical aberration, coma and astigmatism can be reduced, and the image quality is greatly improved.

The aspherical surface expression is as follows:

among them, For the height from the optical axis to the lens surface, the k-type quadric coefficient, Is the aspherical surface coefficient of the i-th order.

2ω: field of view.

First embodiment

The optical components of the lens system 100 satisfy the conditions of Tables 1 and 2, and 2ω = 68.7°.

Table 1

Table 2

The field curvature, distortion and spherical aberration of the lens system 100 are shown in Figures 2 to 4, respectively. The meridional curvature values and the sagittal field curvature values in Fig. 2 are both controlled within the range of (-0.05 mm, 0.05 mm). The distortion rate in Fig. 3 is controlled in the range of (-2%, 2%). Figure 4 for the f line ( Value 435.8nm), d line ( Value 587.6nm), c line ( The value of the sphere observed was 656.3 nm). In general, the spherical aberration value of the lens system 100 of the present embodiment for visible light is in the range of (-0.05 mm, 0.05 mm). It can be seen that the aberration, field curvature and distortion of the lens system 100 can be well corrected.

Second embodiment

The optical elements of the lens system 100 satisfy the conditions of Tables 3 and 4, and 2ω = 68.3°.

table 3

Table 4

The field curvature, distortion and spherical aberration of the lens system 100 are shown in Figures 5 to 7, respectively. The meridional field curvature value and the sagittal field curvature value in Fig. 5 are both controlled within the range of (-0.05 mm, 0.05 mm). The distortion rate in Fig. 6 is controlled within the range of (-2%, 2%). Figure 7 is for the f line ( Value 435.8nm), d line ( Value 587.6nm), c line ( The value of the sphere observed was 656.3 nm). In general, the spherical aberration value of the lens system 100 of the present embodiment for visible light is in the range of (-0.05 mm, 0.05 mm). It can be seen that the aberration, field curvature and distortion of the lens system 100 can be well corrected.

Third embodiment

The optical elements of the lens system 100 satisfy the conditions of Tables 5 and 6, and 2ω = 68.2°.

table 5

Table 6

The curvature of field, distortion and spherical aberration of the lens system 100 are shown in Figs. 8 to 10, respectively. The meridional field curvature value and the sagittal field curvature value in Fig. 8 are both controlled within the range of (-0.05 mm, 0.05 mm). The distortion rate in Fig. 9 is controlled in the range of (-5%, 5%). Figure 10 for the f line ( Value 435.8nm), d line ( Value 587.6nm), c line ( The value of the sphere observed was 656.3 nm). In general, the spherical aberration value of the lens system 100 of the present embodiment for visible light is in the range of (-0.05 mm, 0.05 mm). It can be seen that the aberration, field curvature and distortion of the lens system 100 can be well corrected.

In summary, in the lens system described above, the lens system has a small height when the conditional expression is satisfied, and the distance from the first side of the lens to the imaging surface (ie, the total length of the lens system) is short. Meet the requirements of miniaturization of the lens system while ensuring image quality.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

100‧‧‧ lens system
10‧‧‧ first lens
20‧‧‧second lens
30‧‧‧ third lens
40‧‧‧Fourth lens
50‧‧‧Light
60‧‧‧Filter
70‧‧‧ imaging surface

FIG. 1 is a schematic diagram of a lens system provided by the present invention.

2 is a field curvature diagram of the lens system of the first embodiment.

Fig. 3 is a distortion diagram of the lens system of the first embodiment.

4 is a spherical aberration diagram of the lens system of the first embodiment.

Fig. 5 is a field curvature diagram of the lens system of the second embodiment.

Fig. 6 is a distortion diagram of the lens system of the second embodiment.

Fig. 7 is a spherical aberration diagram of the lens system of the second embodiment.

Fig. 8 is a field curvature diagram of the lens system of the third embodiment.

Fig. 9 is a distortion diagram of the lens system of the third embodiment.

Fig. 10 is a spherical aberration diagram of the lens system of the third embodiment.

100‧‧‧ lens system

10‧‧‧ first lens

20‧‧‧second lens

20‧‧‧ third lens

40‧‧‧Fourth lens

50‧‧‧Light

60‧‧‧Filter

70‧‧‧ imaging surface

Claims (10)

A lens system includes a first lens of positive power, a second lens of negative power, a third lens of positive power, and a positive power of a positive power along the optical axis from the object side to the image side The fourth lens and an imaging surface are improved in that the lens system satisfies the conditional formula D/L>1.18; L/T2>14, where D is the diameter of the effective imaging range of the lens system; L is the lens system The total length; T2 is the on-axis thickness of the second lens. The lens system of claim 1, wherein the first lens satisfies the conditional formula 0.25 < F / G1R1 < 0.45, wherein F is the total focal length of the lens system; G1R1 is the first lens close to the object side The radius of curvature of the surface. The lens system of claim 1, wherein the first lens satisfies the conditional expression νd1>50, wherein νd1 is an Abbe number of the first lens. The lens system of claim 1, wherein the second lens satisfies the conditional expression νd2<32, wherein νd2 is an Abbe number of the second lens. The lens system of claim 1, wherein the second lens satisfies the conditional expression -1.5 < F2 / F < - 0.9, wherein F2 is the focal length of the second lens; F is the total of the lens system focal length. The lens system of claim 1, wherein the third lens satisfies the conditional expression -1 < G3R1/F < -0.5 < G3R2 / F < -0.15, wherein G3R1 is the third lens close to the object side The radius of curvature of the surface; G3R2 is the radius of curvature of the surface of the third lens near the image side. The lens system of claim 1, wherein the first lens, the second lens, the third lens, and the fourth lens are aspherical lenses. The lens system of claim 1, wherein the lens system includes a diaphragm between the first lens and the second lens. The lens system of claim 8, wherein the aperture is disposed on a surface of the first lens near the image side. The lens system of claim 8, wherein the aperture is a black layer on a peripheral annular region on a surface of the first lens near the image side.