TWI412782B - Imaging lens - Google Patents

Abstract

The present invention relates to an imaging lens in order from the object side to the image side including: a first lens with positive refractive power, a second lens with positive refractive power, and a third lens with negtive refractive power. The imaging lens satisfies the following formulas: , 2.4 < S1/D1 < 3.0, 0.3 < R1/F < 0.7; wherein S1 is the effective diameter of the object side of the first lens, D1 is the distances along the optic axis from the object side to the image side of the first lens, R1 is the radius of curvature of the first lens, and F is the focus of the imaging lens.

Description

Image capture lens

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

With the continuous development of technology, electronic products are constantly moving towards light, short, and versatile. In electronic products, such as digital cameras and computers, there are already imaging devices, even portable phones or personal digital assistants. Devices such as PDAs also have the need for integrated image capture devices; for portable and ergonomic needs, the image capture device not only needs to have good image quality, but also requires lower cost, and can effectively enhance the image capture device. Applicability.

In order to improve the image capturing effect of the image capturing device, the aperture value is generally reduced to improve the light transmission performance of the image capturing lens, and the aperture value is decreased to increase the aperture of the image capturing lens, which also increases the optical efficiency of the lens in the image capturing lens. The diameter makes the optical imaging device not able to have a small volume or a low cost, and it is difficult to meet the requirements of light and thin electronic products.

In view of this, it is necessary to provide a small-sized image taking lens.

An image taking lens comprising, in order from the object side to the image side, a first lens having a positive power, a second lens having a positive power, and a third lens having a negative power; the image capturing lens satisfies a conditional expression : 2.4< T 1 / D 1<3.0, 0.3< R 1/ F <0.7; wherein T1 is the effective diameter diameter of the object side of the first lens, and D1 is the side of the object from the first lens to the image side along the optical axis The distance R1 is the radius of curvature of the object side of the first lens, and F is the focal length of the image taking lens.

100‧‧‧Image lens

10‧‧‧ first lens

20‧‧‧second lens

30‧‧‧ third lens

40‧‧‧Light

50‧‧‧ imaging surface

S1‧‧‧ first surface

S2‧‧‧ second surface

S3‧‧‧ third surface

S4‧‧‧ fourth surface

S5‧‧‧ fifth surface

S6‧‧‧ sixth surface

1 is a schematic view showing the optical structure of the image taking lens of the present invention; FIG. 2 is a graph showing the spherical aberration characteristic of the first embodiment of the image taking lens of the present invention; and FIG. 3 is a field curvature characteristic of the first embodiment of the image taking lens of the present invention. FIG. 4 is a distortion characteristic diagram of the first embodiment of the image taking lens of the present invention; FIG. 5 is a spherical aberration characteristic diagram of the second embodiment of the image taking lens of the present invention; FIG. 6 is a drawing lens of the present invention; A field curvature characteristic diagram of the second embodiment; and Fig. 7 is a distortion characteristic diagram of the second embodiment of the image taking lens of the present invention.

The technical solution will be further described in detail below with reference to the accompanying drawings and embodiments.

Please refer to FIG. 1 , which is a schematic structural diagram of an image taking lens 100 according to a preferred embodiment of the present invention. The image taking lens 100 includes, in order from the object side to the image side, a first lens 10 having a positive power, a second lens 20 having a positive power, and a third lens 30 having a negative power.

The side surface of the object facing the object side of the first lens 10 is a first surface S1 facing the image side The side is the second surface S2. The first surface S1 has a meniscus shape that is convex with respect to the object side, and the second surface S2 has a meniscus shape that is recessed with respect to the image side. The first surface S1 and the second surface S2 are both aspherical.

The object side surface of the second lens 20 facing the object side is the third surface S3, and the image side surface facing the image side is the fourth surface S4. The third surface S3 has a meniscus shape recessed with respect to the object side, the fourth surface S4 has a meniscus shape convex with respect to the image side, and the third and fourth surfaces S3 and S4 are aspherical surfaces.

The object side surface of the third lens 30 facing the object side is the fifth surface S5, and the image side surface facing the image side is the sixth surface S6. The fifth surface S5 has a meniscus shape convex with respect to the object side, the sixth surface S6 has a meniscus shape recessed with respect to the image side, and the fifth and sixth surfaces S5 and S6 are aspherical surfaces.

Specifically, the first lens 10, the second lens 20, and the third lens 30 in the above embodiment are all made of a plastic material to reduce the manufacturing cost of the image taking lens 100.

More specifically, the image taking lens 100 further includes an aperture stop 40 disposed before the second surface S2 of the first lens 10 and the third surface S3 of the second lens 20.

When the image capturing lens 100 is imaged, light is incident from the object side, and is sequentially imaged on the image forming surface 50 via the first lens 10, the second lens 20, and the third lens 30. An image sensing device can be constructed by providing a light sensing element at the imaging surface 50.

In order to obtain the image taking lens 100 having a small aperture value and a small volume, the image taking lens 100 satisfies the conditional expression: (1) 2.4 < T 1 / D 1 <3.0; wherein T1 is the first surface S1 of the first lens 10 The effective diameter diameter, D1, is the distance from the first surface S1 of the first lens 10 to the second surface S2 along the optical axis.

The conditional expression (1) limits the aperture value of the entire image taking lens 100, so that the image taking lens 100 has a better light transmission effect.

Preferably, the image taking lens 100 satisfies the conditional expression: (2) 0.3 < R 1 / F < 0.7

Wherein R1 is the radius of curvature of the first surface S1 of the first lens 10, and F is the focal length of the image taking lens 100.

Conditional expression (2) limits the volume of the entire image taking lens 100.

In addition, the image taking lens 100 satisfies the conditional expression: Wherein R1 is the radius of curvature of the first surface S1 of the first lens 10, and F1 is the focal length of the first lens 10.

The conditional expression (3) is advantageous for correcting the spherical aberration and distortion of the entire image taking lens 100.

Furthermore, the image taking lens 100 satisfies the conditional expression: (4) - 0.5 < R 3 / F 2 < R 4 / F 2 <-0.1; wherein R3 is the radius of curvature of the third surface S3 of the second lens 20, R4 It is the radius of curvature of the fourth surface S4 of the second lens 20, and F2 is the focal length of the second lens 20.

The conditional expression (4) is advantageous for correcting the field curvature of the entire image taking lens 100.

(5) - 1.0 < R 5 / F 3 < - 0.5; wherein R5 is the radius of curvature of the fifth surface S5 of the third lens 30, and F3 is the focal length of the third lens 30.

The conditional expression (5) is advantageous for the correction of the coma and astigmatism of the entire image taking lens 100.

(6) - 0.5 < R 6 / F 3 < - 0.1; wherein R6 is the radius of curvature of the sixth surface S6 of the third lens 30, and F3 is the focal length of the third lens 30.

The conditional expression (6) ensures that the astigmatism and distortion of the image taking lens 100 become effective correction.

Finally, the image taking lens 100 satisfies the conditional expression: (7) 45 < Vd 2 <60; wherein Vd2 is the Abbe's coefficient of the second lens 20.

Conditional formula (7) guarantees a shorter total optical length.

The image taking lens 100 will be further described below in conjunction with the attached table. Where R is the radius of curvature of the corresponding surface, D is the on-axis distance from the corresponding surface to the latter surface (image side) (the length of the optical axis of the two surfaces), Nd is the refractive index of the corresponding lens, and Vd is the corresponding lens The Abbe coefficient.

Embodiment 1

The image taking lens 100 of the first embodiment satisfies the conditions listed in Table 1, and the aperture value is 2.0, and the total length of the image taking lens 100 is 2.4 mm.

The aspherical coefficients of the lenses are listed below:

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), and A4 is four times. The 4 th order Aspherical Coefficient A6 is a 6 th order Aspherical Coefficient, A8 is an 8 th order Aspherical Coefficient, and A10 is a tenth aspherical Coefficient. 10 th order Aspherical Coefficient, A12 is a 12 th order Aspherical Coefficient.

The spherical aberration characteristic curve, the field curvature characteristic curve and the distortion characteristic curve of the image taking lens 100 of the first embodiment are shown in FIG. 2, FIG. 3 and FIG. 4, respectively. In Fig. 2, curves f, d and c are f-light (wavelength 486.1 nm, the same below), d (wavelength value 587.6 nm, the same below) light and c-light (wavelength 656.3 nm, the same below) image acquisition The spherical aberration characteristic curve produced by the lens 100 (the same applies hereinafter). It can be seen that the spherical aberration generated by the image capturing lens 100 of the first embodiment for visible light (400-700 nm) is controlled between -0.05 mm and 0.05 mm. In Fig. 3, the curves t and s are the tangential field curvature characteristic curve and the sagittal field curvature characteristic curve (the same applies hereinafter). It can be seen that the meridional curvature value and the sagittal curvature value are controlled between -0.10 mm and 0.10 mm. In Fig. 4, the curve is a distortion characteristic curve (the same applies hereinafter). It can be seen that the distortion variable is controlled between -2% and 2%. It can be seen that the aberration, field curvature and distortion of the image taking lens 100 can be well corrected.

Embodiment 2

The image taking lens 100 of the second embodiment satisfies the conditions listed in Table 3, the aperture value is 2.0, and the total length of the image taking lens 100 is 2.5 mm.

The aspherical coefficients of the lenses are listed below:

The spherical aberration characteristic curve, the field curvature characteristic curve, and the distortion characteristic curve of the image taking lens 100 of the second embodiment are shown in FIG. 5, FIG. 6, and FIG. 7, respectively. In Fig. 5, the spherical aberration generated by visible light is controlled between -0.05 mm and 0.05 mm. In Fig. 6, the meridional field curvature value and the sagittal field curvature value are controlled between -0.10 mm and 0.10 mm. In Figure 7, the distortion is controlled between -2% and 2%. It can be seen that the aberration, field curvature and distortion of the image taking lens 100 can be well corrected.

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‧‧‧Image lens

10‧‧‧ first lens

20‧‧‧second lens

30‧‧‧ third lens

40‧‧‧Light

50‧‧‧ imaging surface

S1‧‧‧ first surface

S2‧‧‧ second surface

S3‧‧‧ third surface

S4‧‧‧ fourth surface

S5‧‧‧ fifth surface

S6‧‧‧ sixth surface

Claims (8)

An image taking lens comprising, in order from the object side to the image side, a first lens having a positive power, a second lens having a positive power, and a third lens having a negative power; the image capturing lens satisfies a conditional expression : 2.4 < T 1 / D 1 < 3.0, 0.3 < R 1 / F < 0.7, where T 1 is the effective diameter diameter of the object side of the first lens, and D 1 is along the optical axis from the object side of the first lens Like the side distance, R 1 is the radius of curvature of the object side of the first lens, and F is the focal length of the image taking lens. The image taking lens according to claim 1, wherein the image capturing lens further satisfies a conditional expression: 1.4 R 1/ F 1 2.2; wherein R 1 is the radius of curvature of the side surface of the first lens, and F 1 is the focal length of the first lens. The image taking lens of claim 1, wherein the image taking lens further satisfies a conditional expression: -0.5 < R 3 / F 2 < R 4 / F 2 <-0.1; wherein R 3 is a second lens The radius of curvature of the side surface, R 4 is the radius of curvature of the image side of the second lens, and F 2 is the focal length of the second lens. The image taking lens according to claim 1, wherein the image capturing lens further satisfies the conditional expression: -1.0 < R 5 / F 3 <-0.5; wherein R 5 is a radius of curvature of the side surface of the third lens, F 3 is the focal length of the third lens. The image taking lens of claim 1, wherein the image taking lens further satisfies the conditional expression: -0.5 < R 6 / F 3 <-0.1; wherein R 6 is a radius of curvature of the image side of the third lens, F 3 is the focal length of the third lens. The image taking lens according to claim 1, wherein the image taking lens further satisfies the conditional expression: 45 < Vd 2 <60; wherein Vd 2 is an Abbe number of the second lens. The image taking lens according to any one of claims 1 to 6, wherein the first, second, and third lenses are aspherical lenses. The image taking lens of claim 7, wherein the first, second, and third lenses are made of a plastic material.