CN104181673A - Large-aperture camera lens - Google Patents

Abstract

The invention discloses a large-aperture camera lens. The large-aperture camera lens comprises a first lens which is a positive lens with the convex object side surface, a second lens which is a negative lens with a concave object side surface, and a third lens which is a positive lens, wherein the image side surface of the third lens is a double-peak face with the concave middle and the convex two sides, and a piece of first flat plate glass is arranged on the third lens and faces towards the image side. The composite of the large-aperture camera lens conforms to the conditional expressions, namely, the quotient of R1 and tt is larger than 0 but smaller than 0.35, the quotient of T2 and tt is larger than 0.13 but smaller than 0.25, and the quotient of R1 and T2 is larger than 2 but smaller than 2.6, wherein R1 represents the curvature radius of the first lens, tt represents the distance between the convex face vertex and the image face of the first lens, and T2 represents the thickness of the second lens. According to the camera lens, the aperture can reach F2.0, the relative brightness reaches 75% or above, the structure is compact, the large-aperture camera lens is particularly suitable for camera lenses of light and thin mobile terminals such as mobile phones and computer camera lenses, the large-aperture camera lens has good performance under the low-illumination environment, the surfaces of all the lenses are easy to machine and form, and the tolerance is large.

Description

A kind of large aperture camera lens

Technical field

The present invention relates to a kind of camera lens, specifically, relate to a kind of large aperture camera lens.

Background technology

At present a lot of intelligent terminals (as mobile phone, panel computer, intelligent TV set etc.) are all installed the camera lens with photograph or recording function, along with intelligent terminal structure do more and more frivolous, therefore to embed camera lens wherein corresponding also require more and more frivolous.For slim tiny lens, at present the main problem existing is that aperture is less, and little aperture is because the light that can arrive on sensitive chip is less, and image quality is bad when under low illuminance environment, produces in batches with high costs.

Summary of the invention

The present invention, in order to solve the bad problem of image quality under little, the low illuminance environment of existing tiny lens aperture, has proposed a kind of large aperture camera lens, for a kind of aperture reaches the large aperture tiny lens of F2.0.

In order to solve the problems of the technologies described above, the present invention is achieved by the following technical solutions:

A large aperture camera lens, comprising:

First lens, is positive lens, and its thing side surface is convex surface;

The second lens, are negative lens, and its thing side surface is concave surface;

The 3rd lens, are positive lens, and it is protruding bimodal in middle concave both sides as side surface;

And, its formation formula that meets the following conditions:

0<R1/tt<0.35；

0.13<T2/tt<0.25；

2<R1/T2<2.6；

Wherein, the radius-of-curvature that R1 is first lens, the convex surface summit that tt is first lens and the distance of image planes, T2 is the thickness of the second lens.

Further, the focal distance f of described camera lens, the focal distance f 3 of focal distance f 2, the three lens of focal distance f 1, the second lens of first lens meets following relational expression:

2<f1<f<-f2<5.2；

40<f3<50；

3.5<f3/tt<4.5；

0.35<R1/f<0.6。

Further again, the visual field of described camera lens is small field of view, and its angle of half field-of view θ meets:

0.4<tanθ<0.5。

Further again, between described first lens and the second lens, be provided with aperture diaphragm.

Preferably, the fixed aperture that the aperture diaphragm of described large aperture camera lens is middle-containing structure.

Preferably, between described the 3rd lens and imaging side, along light incident direction, be disposed with the first sheet glass and the second sheet glass.

Further, described the first sheet glass adopts the glass of BK7 model material, and utilizes IR-cut film plating process to eliminate Infrared.

Further, described each lens are even aspheric surface, and each asphericity coefficient meets following equation:

$z=\frac{{\mathrm{CY}}^2}{1+\sqrt{1-(1+k)C^2{Y}^2}}+\underset{i=2}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_1{Y}^{21}$

Wherein, z is the coordinate along optical axis direction, the radial coordinate that Y Wei Yigai length of lens unit is unit, and C is the curvature of these lens, and k is circular cone coefficient, and α i is the coefficient of each high-order term, and 2i is this aspheric high power.

Or described each lens are odd aspheric surface, each asphericity coefficient meets following equation:

$z=\frac{{\mathrm{CY}}^2}{1+\sqrt{1-(1+k)C^2{Y}^2}}+\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_1{Y}^1.$

Preferably, described each lens are plastic material, and the refractive index n 1 of described first lens and dispersion v1 meet: 1.5 < n1 < 1.65,50 < v1 < 60;

The refractive index n 2 of described the second lens and dispersion v2 meet: 1.5 < n2 < 1.65,20 < v2 < 30;

The refractive index n 3 of described the 3rd lens and dispersion v3 meet: 1.5 < n3 < 1.65,50 < v3 < 60.

Compared with prior art, advantage of the present invention and good effect are: camera lens of the present invention, and aperture can reach F2.0, relative brightness reaches more than 75%, compact conformation, the camera lens of the light and thin type mobile terminals such as especially applicable mobile lens, computer camera lens has good performance under low-light (level) environment, in addition, each eyeglass is the eyeglass of plastic material, and eyeglass cost is low, and each lens surface is easy to processing and moulding, tolerance is good, is beneficial to production in enormous quantities.

Read by reference to the accompanying drawings after the detailed description of embodiment of the present invention, it is clearer that the other features and advantages of the invention will become.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the sectional view of a kind of embodiment of large aperture camera lens proposed by the invention;

Fig. 2 is the transfer curve figure under a kind of situation of large aperture camera lens proposed by the invention;

Fig. 3 is transfer curve figure under another situation of large aperture camera lens proposed by the invention;

Fig. 4 is the optics curvature of field and the distortion figure of large aperture camera lens proposed by the invention;

Fig. 5 is the point range figure of large aperture camera lens proposed by the invention;

Fig. 6 is the system chromatic curve figure of large aperture camera lens proposed by the invention;

Fig. 7 is the system relative luminance curve figure of large aperture camera lens proposed by the invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.

Embodiment mono-, and as shown in Figure 1, the large aperture camera lens of the present embodiment, comprising:

First lens 1, is positive lens, and its thing side surface is convex surface;

The second lens 2, are negative lens, and its thing side surface is concave surface;

The 3rd lens 3, are positive lens, and it is protruding bimodal in middle concave both sides as side surface;

At described the 3rd lens towards be provided with the first sheet glass 4 as side;

And, its formation formula that meets the following conditions:

0<R1/tt<0.35；

0.13<T2/tt<0.25；

2<R1/T2<2.6；

Wherein, R1 is the radius-of-curvature of first lens 1, and tt is the convex surface summit of first lens 1 and the distance of image planes, and T2 is the thickness of the second lens.

The large aperture camera lens of the present embodiment, its aperture can reach F2.0, camera lens overall length is less than 3.5mm,. system transter (MTF) (143lp/mm) 0.85 visual field under 1/2Nyquist frequency reaches more than 0.5 with interior, system imaging is better, realizes visible light wave range (430nm-650nm) blur-free imaging.System focal length 2.84mm, CMOS pixel dimension 1.75um, Diagonal Dimension 2.57mm, cutoff frequency 286lp/mm.

Described each lens are plastic material, and the refractive index n 1 of described first lens and dispersion v1 meet: 1.5 < n1 < 1.65,50 < v1 < 60;

The refractive index n 2 of described the second lens and dispersion v2 meet: 1.5 < n2 < 1.65,20 < v2 < 30;

The refractive index n 3 of described the 3rd lens and dispersion v3 meet: 1.5 < n3 < 1.65,50 < v3 < 60.

Described first lens 1 adopts the version of positive lens, has positive focal power, and the face of thing side is convex surface, plays the effect of collecting light and converging off-axis ray angle.The second lens 2 adopt the version of negative lens, there is negative focal power, the face of thing side is the effect that concave surface plays beam shaping, and the marginal ray after making light by the second lens 2 and chief ray have good collimation and guaranteed again the inclination angle of chief ray to optical axis simultaneously.The 3rd lens 3 adopt positive lens, have positive light coke, and in order better to mate the CRA eyeglass of imager chip, the 3rd lens 3 shapes adopt polymorphic structures, are also that bimodal structure is carried out shaping to light beam, can eliminate off-axis aberration simultaneously.

Preferably, between described first lens 1 and the second lens 2, be provided with aperture diaphragm (not shown).In the present embodiment, the aperture diaphragm of camera lens preferably adopts the fixed aperture of middle-containing structure, and such structure tolerance is better, can elimination off-axis aberration, guaranteed the yield of volume production in the future.

Between described the 3rd lens and imaging side, along light incident direction, be disposed with the first sheet glass 4 and the second sheet glass 5.The first sheet glass 4 utilizes IR-cut film plating process to eliminate Infrared.The cover glass that the second sheet glass 5 is imager chip, for the protection of imager chip.

Such as, the first sheet glass 4 is IR cut filter (cutoff filter), adopts such optical filter can effectively filter out the infrared light that does not need to arrive imaging surface, gained color of image effect and the same scene of eye-observation consistent.Optical filter material is BK7, and refractive index and dispersion are respectively n=1.5168, v=64.17.Utilize IR cut film plating process to eliminate infrared light and enter sensor.Front group adopts positive lens and negative lens collection off-axis ray integer to guarantee certain chief ray angle incident angle, positive and negative combination contributes to color difference eliminating, the 3rd lens 3 Main Functions are by the further integer of light and eliminate coma aberration and the astigmatism outside axle, and revise accurately chief ray angle.

The camera lens that the present embodiment provides adopts 3 eyeglasses (first lens 1, the second lens 2 and the 3rd lens 3), be plastic aspherical element eyeglass, 3 eyeglasses are according to architectural characteristic Rational Arrangement between each element, lens thickness and airspace even thickness distribute, therefore there is no excessive center thickness, there is no too small center thickness yet, such structure is very favourable for allowance control, the production yield of subsequent production, lens shape is easy to processing and moulding, met the requirement of the high relative brightness of large aperture, and the quality of high low temperature imaging is optimized and proofreaied and correct.It is simple in structure, function admirable, and tolerance is good, manufactures simple, cheap.

As a preferred embodiment, the refractive index of first lens 1 and dispersion range can be at 1.5 < n1 < 1.65,50 < v1 < 60, adopt the plastic material of E48R model, its refractive index and dispersion are respectively n1=1.53, v1=56.

The refractive index of the second lens 2 and dispersion range can be at 1.5 < n2 < 1.65,20 < v2 < 30, in the present embodiment, preferably adopt the plastic material of OKP4ht model, its refractive index and dispersion are respectively n2=1.63, v2=23.4.

The refractive index of the 3rd lens 3 and dispersion range can be at 1.5 < n3 < 1.65,50 < v3 < 60, in the present embodiment, preferably adopt the plastic material of E48R model, its refractive index and dispersion are respectively n3=1.53, v3=56.

The camera lens of the present embodiment, aperture can reach F2.0, and relative brightness reaches more than 75%, compact conformation, the camera lens of the light and thin type mobile terminals such as especially applicable mobile lens, computer camera lens has good performance under low-light (level) environment, each lens surface is easy to processing and moulding, and tolerance is good.

Embodiment bis-, the designed requirement of the focal length of camera lens in the present embodiment, and the focal distance f of camera lens, the focal distance f 3 of focal distance f 2, the three lens of focal distance f 1, the second lens of first lens meets following relational expression:

2<f1<f<-f2<5.2；

40<f3<50；

3.5<f3/tt<4.5；

0.35<R1/f<0.6。

In order to realize the allomeric function of camera lens, aperture is large, camera lens is thin and light transmission is applicable to well low illuminance environment, and the visual field of described camera lens is small field of view, and its angle of half field-of view θ meets:

0.4<tanθ<0.5。

Provide a kind of lens data of large aperture camera lens of the present embodiment below, wherein, the angle of view is 50 °, and aperture reaches the large aperture small field of view CCM camera lens of F2.0.As shown in table 1, wherein: surface type (Type), the curvature of each optical surface (C) on optical axis, along the thickness (T) between each optical surface on the optical axis of light incident direction and adjacent next optical surface, along the material (Glass) between each optical surface on the optical axis of light incident direction and adjacent next optical surface, half bore (Semi-Diameter), circular cone coefficient (Conic), focal power (Focal power), wherein, the unit of thickness (T) and half bore (Semi-Diameter) is mm, the unit of curvature (C) and focal power (Focal power) is mm ^-1.

As T in Fig. 1 represent the second lens 2 near picture side the distance to rear one side, described each lens are even aspheric surface, and even asphericity coefficient α 2, α 3, α 4, α 5, α 6, α 7, α 8, each asphericity coefficient meets following equation:

$z=\frac{{\mathrm{CY}}^2}{1+\sqrt{1-(1+k)C^2{Y}^2}}+\underset{i=2}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_1{Y}^{21}$

Wherein, z is the coordinate along optical axis direction, the radial coordinate that Y Wei Yigai length of lens unit is unit, and C is the curvature of these lens, and k is circular cone coefficient, and α i is the coefficient of each high-order term, and 2i is this aspheric high power.

Wherein, z is the coordinate along optical axis direction, the radial coordinate that Y Wei Yi length of lens unit is unit, C is curvature (1/R), k is circular cone coefficient (Coin Constant), α i is the coefficient of each high-order term, and 2i is aspheric high power (the order of Aspherical Coefficient), and in the design, i=8 is that quadratic term is up to 16 powers.

Table 1

Table 2

The large aperture camera lens of the present embodiment, coordinates OV9726 sensitive chip can reach the field angle of 50 °, and system imaging is superior in quality, and relative exposure evenly and guarantee more than 70%, has well guaranteed the performance under low-light (level).

Certainly, in this embodiment, also can adopt odd aspherical equation to design, the general formula of odd aspherical equation is as follows:

$z=\frac{{\mathrm{CY}}^2}{1+\sqrt{1-(1+k)C^2{Y}^2}}+\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_1{Y}^1$

Wherein, i=1,2,3,4 ... N.Equally also can reach purpose of design.

The first described sheet glass 4 and as being provided with the second sheet glass 5 between side, is the cover glass of imager chip, and after the flange of system, Jiao guarantees more than 0.3mm.

As shown in Figure 2 and Figure 3, the MTF of camera lens embodiment of the present invention, the image quality that MTF transfer curve figure (optical transfer function) can concentrated expression system, its curve shape is more level and smooth, and X-axis height is higher relatively, and the image quality of proof system is better.What Fig. 2 reflected is the MTF curve under sensor limiting resolution, and what Fig. 3 figure reflected is that 1/2 limit is differentiated MTF curve under frequency.In figure, different lines represent respectively each field rays, from figure, two curves that pass in letter curve map are comparatively level and smooth compact, the mtf value that Curves characterizes is very high, in limiting resolution situation, 0.85 visual field has all reached more than 0.25 with interior MTF, and the aberration of illustrative system has obtained good correction.

As shown in Figure 4, the optics curvature of field and the distortion figure of the present embodiment camera lens, different colours represents different wavelength, same color right side graph is meridian direction, left side curve is for being Sagittal field curvature, the two does difference is exactly the astigmatism of system, astigmatism and the curvature of field are the important aberrations that affects the outer field rays of axle, astigmatism is crossed the image quality of the serious system that the has influence on off-axis ray of conference, the curvature of field can cause center and peripheral optimal imaging not in one plane, and from figure, the curvature of field of system and astigmatism are all corrected in 50um.In figure, another curve is the distortion curve of system, distortion does not affect the sharpness of system, but can cause the anamorphose of system, for wide-angle lens, correcting distorted is very difficult, the optical distortion of native system is less than 2%, and this explanation distortion has been remedied to an extraordinary degree.

As shown in Figure 5, it is the point range figure of the present embodiment camera lens, each field rays of point range figure display system converges at image planes place and the disperse degree that forms, so it has characterized system and has obtained the various characteristics that differ, the image quality of the less proof system of RMS radius of point range figure is better.The disc of confusion RMS diameter of native system is all less than 4.5um, illustrates that aberration correction is very good.

As shown in Figure 6, system chromatic curve figure, as can be seen from Figure 6, the aberration of the present embodiment camera lens (the mutual differences of red, green, blue three colors) is controlled in 0.5um, for slim tiny lens, can say the fairly good of control, the rank that generally current existing sampling image lens design aberration reaches 1 pixel is just good at last, and the design's chip pixel is of a size of 1.75um.

As shown in Figure 7, system relative luminance curve figure, as can be seen from Figure 7, the relative brightness of the present embodiment camera lens can reach more than 65%, generally the design of sampling image lens on the market more than 50% is being exactly mean level relatively twice, relatively highlyer twice represents that the consistance of periphery brightness and center brightness is higher; Otherwise if relative brightness is lower, image corner looks can be darker, imaging effect is bad.

Certainly; above-mentioned explanation is not limitation of the present invention; the present invention is also not limited in above-mentioned giving an example, and the variation that those skilled in the art make in essential scope of the present invention, remodeling, interpolation or replacement, also should belong to protection scope of the present invention.

Claims (10)

1. a large aperture camera lens, is characterized in that, comprising:

First lens, is positive lens, and its thing side surface is convex surface;

The second lens, are negative lens, and its thing side surface is concave surface;

The 3rd lens, are positive lens, and it is protruding bimodal in middle concave both sides as side surface;

And, its formation formula that meets the following conditions:

0<R1/tt<0.35；

0.13<T2/tt<0.25；

2<R1/T2<2.6；

Wherein, the radius-of-curvature that R1 is first lens, the convex surface summit that tt is first lens and the distance of image planes, T2 is the thickness of the second lens.

2. large aperture camera lens according to claim 1, is characterized in that, the focal distance f of described camera lens, and the focal distance f 3 of focal distance f 2, the three lens of focal distance f 1, the second lens of first lens meets following relational expression:

2<f1<f<-f2<5.2；

40<f3<50；

3.5<f3/tt<4.5；

0.35<R1/f<0.6。

3. large aperture camera lens according to claim 2, is characterized in that, the visual field of described camera lens is small field of view, and its angle of half field-of view θ meets:

0.4<tanθ<0.5。

4. large aperture camera lens according to claim 1, is characterized in that, between described first lens and the second lens, is provided with aperture diaphragm.

5. large aperture camera lens according to claim 4, is characterized in that, the fixed aperture that the aperture diaphragm of described large aperture camera lens is middle-containing structure.

6. according to the large aperture camera lens described in any one in claim 1-3, it is characterized in that, between described the 3rd lens and imaging side, along light incident direction, be disposed with the first sheet glass and the second sheet glass.

7. large aperture camera lens according to claim 6, is characterized in that: described the first sheet glass adopts the glass of BK7 model material, and utilizes IR-cut film plating process to eliminate Infrared.

8. according to the large aperture camera lens described in claim 1-3 any one, it is characterized in that, described each lens are even aspheric surface, and each asphericity coefficient meets following equation:

$z=\frac{{\mathrm{CY}}^2}{1+\sqrt{1-(1+k)C^2{Y}^2}}+\underset{i=2}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_1{Y}^{21}$

Wherein, z is the coordinate along optical axis direction, the radial coordinate that Y Wei Yigai length of lens unit is unit, and C is the curvature of these lens, and k is circular cone coefficient, and α i is the coefficient of each high-order term, and 2i is this aspheric high power.

9. according to the large aperture camera lens described in claim 1-3 any one, it is characterized in that, described each lens are odd aspheric surface, and each asphericity coefficient meets following equation:

$z=\frac{{\mathrm{CY}}^2}{1+\sqrt{1-(1+k)C^2{Y}^2}}+\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_1{Y}^1.$

10. according to the large aperture camera lens described in any one in claim 1-3, it is characterized in that: described each lens are plastic material, the refractive index n 1 of described first lens and dispersion v1 meet: 1.5 < n1 < 1.65,50 < v1 < 60;

The refractive index n 2 of described the second lens and dispersion v2 meet: 1.5 < n2 < 1.65,20 < v2 < 30;

The refractive index n 3 of described the 3rd lens and dispersion v3 meet: 1.5 < n3 < 1.65,50 < v3 < 60.