TWI395991B - Aspheric optical lens system for taking image - Google Patents

Description

Aspheric imaging lens group

The present invention relates to a lens group, and more particularly to an aspherical imaging lens group applied to a miniaturized photographic lens.

In recent years, with the rise of mobile phone cameras, the demand for miniaturized photographic lenses has been increasing, and the photosensitive elements of general photographic lenses are nothing more than a Charge Coupled Device (CCD) or a Complementary Metallic Semiconductor (Complementary Metal). -Oxide Semiconductor, CMOS), due to the advancement of semiconductor process technology, the pixel area of the photosensitive element is reduced, and the miniaturized photographic lens is gradually developing into the high-pixel field. Therefore, the requirements for image quality are increasing, and Aberration is corrected in a limited lens space to achieve good image quality, and an aspheric surface is generally placed on the lens.

As the photographic lens develops in the field of higher paintings and the space of the lens becomes smaller, it is no longer possible to reduce the lens volume to match the optical system arbitrarily. Therefore, it is necessary to find a method of increasing the degree of freedom from the optical system. One of them is to enhance the ability of aspherical surfaces.

The present invention provides an aspherical imaging lens group composed of at least two lenses for improving the degree of freedom of the optical system and effectively reducing the lens volume. The gist is as follows: an aspherical imaging lens set comprising: at least two lenses, at least one lens surface being aspherical, having a taper coefficient of k, which will satisfy the following relationship: k<-2000; and at least one lens surface is aspherical And its aspherical parameter is set with an odd-order term other than 0.

In the aspherical imaging lens group of the present invention, a non-zero odd-order term is introduced into the aspherical coefficient, and the degree of freedom in selecting the shape of the lens can be increased. In the aspherical imaging lens group of the present invention, the aspherical cone surface coefficient is k, which satisfies the following relationship: k<-2000; the above relationship can reduce the dependence of the aspherical curvature radius, thereby increasing the degree of freedom of selecting the lens shape. Further, it is more desirable to make k<-10000.

In the aspherical imaging lens group of the present invention, when the aspherical surface has a taper coefficient k<-2000 and a non-zero odd-order term, it is more advantageous to increase the degree of freedom in selecting the lens shape, thereby reducing the volume of the lens group. It is more preferable that the above-mentioned taper coefficient k < -10000. It is more preferable to have a plurality of mirrors having the above characteristics.

In the aspherical imaging lens group of the present invention, the distance from the inflection point to the optical axis on the aspherical surface is Y', and the optical effective path Y of the lens surface satisfies the following relationship: 0<Y'/Y<0.03; Satisfying the above relationship can increase the degree of freedom of the central region of the lens, making the shape selection of the central region of the lens more flexible. It is preferable to provide the aspherical surface with a taper coefficient k<-2000 or a non-zero odd-order term, and to make the aspherical surface have a taper coefficient k<-2000 and a non-zero odd-order term, which is more advantageous for increasing the selected lens shape. The degree of freedom. It is more preferable that the above-mentioned taper coefficient k < -10000. It is more preferable to have a plurality of mirrors having the above characteristics.

In the aspherical imaging lens group of the present invention, the aspherical cone surface coefficient is k<-2000, and the radius of curvature is R, and the focal length of the entire aspherical imaging lens group is f, which satisfies the following relationship: |R|/f<0.5 When the above relationship is satisfied, the lens volume can be effectively reduced, and the space requirement of the miniaturized lens group can be satisfied, and it is more desirable to further |R|<1.5 mm. It is more preferable that the above-mentioned taper coefficient k < -10000.

In the aspherical imaging lens group of the present invention, the object is imaged on the electronic photosensitive element, and the total optical length of the entire aspheric imaging lens group is TTL, and the maximum imaging height of the entire aspheric imaging lens group is ImgH, which satisfies the following relationship: TTL/ ImgH<2.5; satisfying the above relationship, the characteristics of miniaturization of the optical lens group can be maintained.

For the first embodiment of the present invention, please refer to FIG. 1A. For the aberration curve of the first embodiment, refer to FIG. 1B. The object side and the image side of the first embodiment include: a first lens 10 having a positive refractive power. The first lens 10 has a front surface 11 and a rear surface 12, the front surface 11 of the first lens 10 is aspherical, and the rear surface 12 of the first lens 10 is aspherical with a taper coefficient k of -31257.2, and thereafter the surface 12 The aspherical coefficient contains a non-zero odd-order term; a second lens 20 having a negative refractive power, the second lens 20 has a front surface 21 and a rear surface 22, and the front surface 21 of the second lens 20 is aspherical, and the tapered surface thereof The coefficient k is -6135.91. The aspherical coefficient of the surface 21 previously contains an odd-order term other than 0, and the rear surface 22 of the second lens 20 is aspherical. The aspherical coefficient of the surface 22 thereafter has an odd-order term other than 0; a negative refractive power The third lens 30 has a front surface 31 and a rear surface 32, the front surface 31 of the third lens 30 is aspherical, the rear surface 32 of the third lens 30 is aspherical, and an aperture 40 is placed on the third lens 30. Before a lens 10; an infrared filter (IR Filter) 50, which is made of glass, is placed in the third After the mirror 30, which does not affect the focal length of the system; an imaging surface 60, is placed after the infrared filter 50.

The equation for the aspheric curve is expressed as follows:

Where: X: the cross-sectional distance of the lens; Y: the height of the point on the aspheric curve from the optical axis; k: the taper coefficient; Ai: the i-th aspheric coefficient.

In the aspherical imaging lens group of the first embodiment, the front surface of the second lens has a radius of curvature R3, which is |R3| = 0.55369 mm.

In the aspherical imaging lens group of the first embodiment, the focal length of the entire aspheric imaging lens group is f, and the curvature radius R3 of the front surface of the second lens is: |R3|/f=0.16578.

In the aspherical imaging lens group of the first embodiment, the total optical length of the entire aspheric imaging lens group is TTL, and the maximum imaging height of the entire aspheric imaging lens group is ImgH, and the relationship is: TTL/ImgH=1.75.

The detailed structural data of the first embodiment is shown in Table 1, and its aspherical data is as shown in Table 2, in which the unit of curvature radius, thickness, and focal length is mm, and HFOV is defined as half of the maximum viewing angle.

For the second embodiment of the present invention, please refer to FIG. 2A. For the aberration curve of the second embodiment, refer to FIG. 2B. The object side and the image side of the second embodiment include: a first lens 10 having a positive refractive power. The first lens 10 has a front surface 11 and a rear surface 12, the front surface 11 of the first lens 10 is aspherical, the aspherical coefficient of the front surface 11 contains an odd-order term other than 0, and the rear surface 12 of the first lens 10 is aspherical. The taper coefficient k is -22051.3, and thereafter the aspherical coefficient of the surface 12 contains a non-zero odd-order term; a second lens 20 having a negative refractive power, the second lens 20 has a front surface 21 and a rear surface 22, The front surface 21 of the second lens 20 is aspherical, the rear surface 22 of the second lens 20 is aspherical; a third lens 30 having a positive refractive power, the third lens 30 has a front surface 31 and a rear surface 32, and a third The front surface 31 of the lens 30 is aspherical, and its taper coefficient k is -12328.5. The aspherical coefficient of the front surface 31 contains an odd-order term other than 0, and the rear surface 32 of the third lens 30 is aspherical, and the taper coefficient k is - 27825.6, after which the aspherical coefficient of the surface 32 contains a non-zero odd-order term; an aperture 40, placed first Between the mirror 10 and the second lens 20; an IR filter 50, which is made of glass, is placed behind the third lens 30, which does not affect the focal length of the system; an imaging surface 60 is placed in the infrared filter After the light sheet 50.

a sensor cover glass 70 is disposed between the infrared filter 50 and the image plane 60, which does not affect the focal length of the system; The expression of the aspheric curve equation of the second embodiment is the same as that of the first embodiment.

In the aspherical imaging lens group of the second embodiment, the total optical length of the entire aspheric imaging lens group is TTL, and the maximum imaging height of the entire aspheric imaging lens group is ImgH, and the relationship is: TTL/ImgH=1.97.

The detailed structural data of the second embodiment is shown in Table 3. The aspherical data is as shown in Table 4, in which the unit of curvature radius, thickness, and focal length is mm, and HFOV is defined as half of the maximum viewing angle.

For the third embodiment of the present invention, please refer to FIG. 3A. For the aberration curve of the second embodiment, refer to FIG. 3B. The second embodiment includes: a first lens 10 having a positive refractive power between the object side and the image side. The first lens 10 has a front surface 11 and a rear surface 12, the front surface 11 of the first lens 10 is aspherical, the aspherical coefficient of the front surface 11 contains an odd-order term other than 0, and the rear surface 12 of the first lens 10 is aspherical. a second lens 20 having a negative refractive power, the second lens 20 has a front surface 21 and a rear surface 22, the front surface 21 of the second lens 20 is aspherical, and the rear surface 22 of the second lens 20 is aspherical; a third lens 30 having a negative refractive power, the third lens has a front surface 31 and a rear surface 32, and the front surface 31 of the third lens 30 is aspherical, the front surface 31 The aspherical coefficient contains an odd-order term other than 0, and the rear surface 32 of the third lens 30 is aspherical, and the taper coefficient k is -100,000. Thereafter, the aspherical coefficient of the surface 32 contains an odd-order term other than 0, and is applied to the third lens. The back surface 31 of the 30 is provided with an inflection point; an aperture 40 is disposed between the first lens 10 and the second lens 20; and an IR filter 50 is made of glass and placed on the third lens 30. Thereafter, it does not affect the focal length of the system; an imaging surface 60 is placed behind the infrared filter 50.

The expression of the aspheric curve equation of the third embodiment is the same as that of the first embodiment.

In the aspherical imaging lens group of the third embodiment, the distance from one of the inflection points of the third lens rear surface to the optical axis is Y', and the optical effective diameter Y of the lens surface is: Y'/ Y=0.004.

In the aspherical imaging lens group of the third embodiment, the total optical length of the entire aspheric imaging lens group is TTL, and the maximum imaging height of the entire aspheric imaging lens group is ImgH, and the relationship is: TTL/ImgH=2.29.

The detailed structural data of the third embodiment is as shown in Table 3, and the aspherical data is as shown in Table 4, in which the unit of curvature radius, thickness, and focal length is mm, and HFOV is defined as half of the maximum angle of view.

In the aspherical imaging lens group of the present invention, the first lens, the second lens, and the third lens are made of a plastic material or a glass material.

It is to be noted here that Tables 1 to 6 show different numerical value change tables of the embodiment of the aspherical imaging lens group, but the numerical values of the various embodiments of the present invention are experimentally obtained, even if different values are used, the products of the same structure are used. It should still fall within the scope of protection of the present invention.

In summary, the present invention is an aspherical imaging lens group, whereby the lens structure, the arrangement and the lens configuration can effectively reduce the volume of the lens group, and can simultaneously obtain a higher resolution.

Therefore, the "industry availability" of the present invention should be unquestionable. In addition, the feature technology disclosed in the embodiment of the present invention has not been seen in publications before the application, nor has it been publicly used, and has not only As described above, the fact that the effect is enhanced is more indispensable, and therefore, the "novelty" and "progressiveness" of the present invention are in compliance with the patent regulations, and the application for the invention patent is filed according to law, and the application for review is prayed for. And as soon as the patent is granted, it is really good.

10‧‧‧ first lens

11‧‧‧ front surface

12‧‧‧Back surface

20‧‧‧second lens

21‧‧‧ front surface

22‧‧‧Back surface

30‧‧‧ third lens

31‧‧‧ front surface

32‧‧‧Back surface

40‧‧‧ aperture

50‧‧‧Infrared filter

60‧‧‧ imaging surface

70‧‧‧Photosensitive element protection glass

K‧‧‧cone coefficient

Y’‧‧‧The distance from the inflection point to the optical axis on the aspheric surface

Y‧‧‧ Optical Effective Path of Lens Surface

Half of the maximum field of view of HFOV‧‧

Optical total length of TTL‧‧‧ integral aspheric imaging lens set

Maximum imaging height of the ImgH‧‧‧ overall aspheric imaging lens set

Fig. 1A is a schematic view showing an optical system of a first embodiment of the present invention.

Fig. 1B is a diagram showing aberrations of the first embodiment of the present invention.

2A is a schematic view of an optical system of a second embodiment of the present invention.

Fig. 2B is a diagram showing aberrations of the second embodiment of the present invention.

Fig. 3A is a schematic view showing an optical system of a third embodiment of the present invention.

Fig. 3B is a diagram showing the aberration of the third embodiment of the present invention.

[Table description]

Table 1 Structure data of the first embodiment of the present invention.

Table 2 Aspherical data of the first embodiment of the present invention.

Table 3 Structure data of the second embodiment of the present invention.

Table 4 Aspherical data of a second embodiment of the present invention.

Table 5 Structure data of the third embodiment of the present invention.

Table 6 Aspherical data of a third embodiment of the present invention.

10‧‧‧ first lens

11‧‧‧ front surface

12‧‧‧Back surface

20‧‧‧second lens

21‧‧‧ front surface

22‧‧‧Back surface

30‧‧‧ third lens

31‧‧‧ front surface

32‧‧‧Back surface

40‧‧‧ aperture

50‧‧‧Infrared filter

60‧‧‧ imaging surface

Claims (6)

An aspherical imaging lens set comprising: a three lens, at least one lens surface is aspherical and provided with an inflection point, and a distance from one of the aspherical surfaces to the optical axis is Y′, and an optical effective diameter of the lens surface Y, and at least one position of the inflection point is set to satisfy the following relationship: 0 < Y' / Y < 0.03, and the number of refractive power lenses in the aspherical imaging lens group is only three. The aspherical imaging lens group according to claim 1, wherein at least one of the lens surfaces is aspherical, and the aspherical parameter is set with an odd-order term other than zero. The aspherical imaging lens group according to claim 2, wherein at least two lens surfaces are aspherical, and the aspherical parameter thereof is provided with an odd-order term other than zero. The aspherical imaging lens group according to claim 1, wherein at least one lens surface is aspherical and k<-2000. The aspherical imaging lens group according to claim 4, wherein k < -10000. The aspherical imaging lens set according to claim 1, wherein the aspherical imaging lens group further comprises an electronic photosensitive element for imaging the object, and the total optical length of the aspherical imaging lens group is TTL, the aspherical imaging The maximum imaging height of the lens group is ImgH, and the foregoing two satisfy the following relationship: TTL/ImgH<2.5.