TWI425269B - Miniature lens - Google Patents

Description

Miniaturized lens

The present invention relates to an optical system, and more particularly to a miniaturized lens composed of three lenses.

In recent years, with the advancement of imaging technology, image capturing devices such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) have been widely used in image pickup devices such as digital cameras or mobile phones. Apparatus). With the miniaturization of these video devices in recent years, the size of the above-described image capturing device and the lens applied to the above-described image device has also been greatly reduced. In addition, since the pixels of the image capturing device are getting higher and higher, the lens used for the image capturing device can also have higher optical performance, so that the image capturing device can achieve high resolution. Degree and high contrast. Therefore, miniaturization and high optical performance are two essential elements for the lens of imaging equipment.

In the past, a lens consisting of one to two lenses was able to meet the needs of the image capture device at that time, but with the increase of pixels, the lens with more lenses can meet the demand of high pixels.

At present, the miniaturized lens used in imaging equipment consists of three lenses or four lenses. Among them, the three-lens lens is small in size, but the optical performance is insufficient, and it cannot meet the demand of high pixels. The four-lens lens has better optical performance, but its volume is larger than that of the three-lens lens. However, it has not been able to achieve effective miniaturization.

Based on the above, it can be known that the known miniaturized lens is still not perfect, and there is still room for improvement.

In view of this, the main object of the present invention is to provide a miniaturized lens which is composed of three lenses, which is not only small in size but also has high optical efficiency.

In order to achieve the above object, the miniaturized lens provided by the present invention comprises a first lens, an aperture, a second lens and a third arranged along an optical axis and arranged from an object side to an image side. a lens made of a glass material having a positive refractive power and at least one surface being an aspherical surface; the second lens being made of a plastic material and having a positive refractive power; and the third lens being made of a plastic material and having Negative refractive power for miniaturization and high optical performance.

In order that the present invention may be more clearly described, the preferred embodiments are illustrated in the accompanying drawings.

1 is a lens arrangement diagram of a miniaturized lens 1 according to a first embodiment of the present invention, and FIG. 2 is an optical path diagram of the embodiment shown in FIG. 1. Referring to FIG. 1 and FIG. 2, a first embodiment of the present invention will be described in detail below. Miniaturized lens 1.

The miniaturized lens 1 includes a first lens L1, an aperture ST, a second lens L2 and a third lens L3 disposed on the optical axis Z from the object side to the image side. The three lenses L1 to L3 can be All are single lenses, or they may all be composite lenses, or some lenses may be single lenses and some lenses may be composite lenses. In addition, depending on the requirements of use, a glass cover CG (Cover Glass) can be selectively disposed between the third lens L3 and the imaging plane IP (Image Plane), which is a flat glass. Wherein: the first lens L1 is made of a glass material, has a positive refractive power, and is a meniscus aspherical lens, the object side surface S1 is a convex surface, and the object side surface S1 and the image side surface S2 are aspherical surfaces. And meet the following conditions:

0.2<R1/F1<0.7

Wherein R1 is the radius of the first lens L1, and F1 is the effective focal length of the first lens L1.

The second lens L2 is made of a plastic material and has a positive refractive power and is a crescent-shaped aspherical mirror. The object side surface S4 is a concave surface, and the object side surface S4 and the image side surface S5 are aspherical surfaces.

The third lens L3 is made of a plastic material, and its refractive power gradually changes from a negative refractive power to a positive refractive power from the passage of the optical axis Z to the periphery. In addition, the image side surface S7 of the third lens L3 is aspherical, and the radius of curvature of the optical axis region of the image side surface S7 (referring to the vicinity of the optical axis Z passing through and its predetermined range) is positive, from the light The radius of curvature from the shaft area to the circumference is negative.

The surface of each of the lenses is close to the radius of curvature R at the optical axis Z, the thickness of each lens on the optical axis T, the refractive index of each lens nd (refractive index), and the Abbe's coefficient vd of each lens. (Abbe number) and the conic constant of the surface of each lens, as shown in Table 1:

In Table 1, the surface numbers S1 and S2 are the surfaces of the first lens L1; the surface number S3 refers to the surface of the aperture ST facing the second lens L2; the surface numbers S4 to S7 are respectively the second lens L2 and The surface of the third lens L3; the surface numbers S8 and S9 are the two surfaces of the glass covering CG.

The radius of curvature R shown in Table 1 is the radius of curvature on the corresponding surface close to the optical axis Z.

The lens thickness T shown in Table 1, wherein the data corresponding to S1 is the thickness of the first lens L1 on the optical axis Z; the data corresponding to S2 is the first lens L1 and the second lens L2 on the optical axis Z. Spacing; the data corresponding to S4 is the thickness of the second lens L2 on the optical axis Z; the data corresponding to S5 is the distance between the second lens L2 and the third lens L3 on the optical axis Z; the data corresponding to S6 is the first The thickness of the three lenses L3 on the optical axis Z; the data corresponding to S7 is the distance between the third lens L3 and the glass cover CG on the optical axis Z; the data corresponding to S8 is the thickness of the glass cover CG; the data corresponding to S9 is The distance between the glass cover CG and the imaging plane IP.

Further, the refractive index nd and the Abbe's coefficient vd corresponding to the surface numbers S1, S4, S6, and S8 are the refractive indices and Abbe coefficients of the first lens L1, the second lens L2, the third lens L3, and the glass cover CG, respectively. .

In each lens of this embodiment, the surface depression z of the aspherical surfaces S1, S2, S4, S5, and S7 is obtained by the following formula:

Where: z: the degree of depression of the aspherical surface; c: the reciprocal of the radius of curvature; h: the aperture radius of the surface; k: the conic coefficient; A to I: the order coefficients of the aperture radius h of the surface.

In the present embodiment, the conic coefficients k (conic constant) of each aspheric surface and the order coefficients A to I of the surface aperture radius h are as shown in Table 2:

Table II

With the above-described lens and aperture arrangement, the miniaturized lens 1 of the present embodiment can not only effectively reduce the volume required for miniaturization, but also achieve imaging quality, which can be seen from FIG. 3A to FIG. 3C.

FIG. 3A is a field curvature diagram and a distortion diagram of the miniaturized lens 1 of the present embodiment; and FIG. 3B is a defocus modulation transfer function diagram (Through Focus MTF) of the miniaturized lens 1 of the present embodiment. FIG. 3C shows a spatial frequency modulation transfer function (Spatial Frequency MTF) of the miniaturized lens 1 of the present embodiment. As can be seen from Fig. 3A, the maximum field curvature of this embodiment does not exceed 0.04 mm and -0.04 mm, and the distortion variable does not exceed 2%. As can be seen from Fig. 3B, this embodiment has a good resolution regardless of the field of view position. As can be seen from Fig. 3C, the value of the modulation optical transfer function of the present embodiment is maintained at 50% or more at 113.5 lp/mm. It is apparent that the resolution of the miniaturized lens 1 of the present embodiment is in compliance with the standard.

The above is the miniaturized lens 1 of the first embodiment of the present invention; the second embodiment of the present invention will be described below with reference to Figs. 4 and 5 in accordance with the technology of the present invention.

As in the first embodiment, the miniaturized lens 2 of the second embodiment of the present invention includes a first lens L1, an aperture ST, a second lens L2, and a photo lens Z disposed from the object side to the image side. A third lens L3, and a glass cover CG of a flat glass is also disposed between the third lens L3 and the imaging plane IP. The first lens L1 has a positive refractive power and is a crescent-shaped glass aspherical mirror. The object side surface S1 is a convex surface, and the object side surface S1 and the image side surface S2 are both aspherical surfaces, and the following conditions are also satisfied:

0.2<R1/F1<0.7

Wherein R1 is the radius of the first lens L1, and F1 is the effective focal length of the first lens L1.

The second lens L2 has a positive refractive power and is a crescent-shaped plastic aspherical mirror. The object side surface S4 is a concave surface, and both the object side surface S4 and the image side surface S5 are aspherical.

The third lens L3 is a plastic aspherical mirror, and the image side surface S7 is aspherical, and the radius of curvature of the optical axis region of the image side surface S7 is a positive value, and the radius of curvature from the optical axis region to the periphery of the third lens L3 is Negative value. In addition, the third lens L3 gradually changes from a negative refractive power to a positive refractive power from the point where the optical axis Z passes to the periphery.

Each of the lens surfaces is close to a radius of curvature R at the optical axis, a thickness T of each lens on the optical axis, a refractive index nd of each lens, and an Abbe's coefficient vd of each lens ( Abbe number) and the conic constant of the surface of each lens, as shown in Table 3:

In Table 3, the surface numbers S1 and S2 are the surfaces of the first lens L1; the surface number S3 refers to the surface of the aperture ST facing the second lens L2; the surface numbers S4 to S7 are respectively the second lens L2 and The surface of the third lens L3; the surface numbers S8 and S9 are the two surfaces of the glass covering CG.

The radius of curvature R shown in Table 3 is the radius of curvature at the corresponding surface on the optical axis Z.

The lens thickness T shown in Table 3, wherein the data corresponding to S1 is the thickness of the first lens L1 on the optical axis Z; the data corresponding to S2 is the first lens L1 and the second lens L2 on the optical axis Z. Spacing; the data corresponding to S4 is the thickness of the second lens L2 on the optical axis Z; the data corresponding to S5 is the distance between the second lens L2 and the third lens L3 on the optical axis Z; the data corresponding to S6 is the first The thickness of the three lenses L3 on the optical axis Z; the data corresponding to S7 is the distance between the third lens L3 and the glass cover CG on the optical axis Z; the data corresponding to S8 is the thickness of the glass cover CG; the data corresponding to S9 is The distance between the glass cover CG and the imaging plane IP.

Further, the refractive index nd and the Abbe's coefficient vd corresponding to the surface numbers S1, S4, S6, and S8 are the refractive indices and Abbe coefficients of the first lens L1, the second lens L2, the third lens L3, and the glass cover CG, respectively. .

In each lens of this embodiment, the surface depression z of the aspherical surfaces S1, S2, S4, S5, and S7 is obtained by the following formula:

Where: z: the degree of depression of the aspherical surface; c: the reciprocal of the radius of curvature; h: the aperture radius of the surface; k: the conic coefficient; A to I: the order coefficients of the aperture radius h of the surface.

In the present embodiment, the conic coefficients k (conic constant) of each aspheric surface and the order coefficients A to I of the surface aperture radius h are as shown in Table 4:

With the above-described lens and aperture arrangement, the miniaturized lens 2 of the present embodiment can not only effectively reduce the volume to be miniaturized, but also achieve imaging quality, which can be seen from FIG. 6A to FIG. 6C.

FIG. 6A is a field curvature diagram and a distortion diagram of the miniaturized lens 2 of the present embodiment; and FIG. 6B is a defocus modulation transfer function diagram (Through Focus MTF) of the miniaturized lens 2 of the present embodiment. FIG. 6C shows the spatial frequency modulation transfer function (Spatial Frequency MTF) of the miniaturized lens 2 of the present embodiment. As can be seen from Fig. 6A, the maximum field curvature of this embodiment does not exceed 0.06 mm and -0.04 mm, and the distortion variable does not exceed 2%. As can be seen from Fig. 6B, this embodiment has a good resolution regardless of the field of view position. As can be seen from Fig. 6C, the value of the modulation optical transfer function of the present embodiment is maintained at 30% or more at 113.5 lp/mm. It is apparent that the resolution of the miniaturized lens 2 of the present embodiment is in compliance with the standard.

As can be seen from the above detailed description, the miniaturized lens of the present invention is not only small in size, but also has high optical performance, so as to meet the demand for imaging equipment.

The above description is only for the preferred embodiments of the present invention, and the equivalent structures and manufacturing methods of the present invention and the scope of the patent application are intended to be included in the scope of the present invention.

1. . . Miniaturized lens

L1. . . First lens

L2. . . Second lens

L3. . . Third lens

CG. . . Glass cover

IP. . . Imaging plane

ST. . . aperture

S1~S9. . . surface

2. . . Miniaturized lens

L1. . . First lens

L2. . . Second lens

L3. . . Third lens

CG. . . Glass cover

IP. . . Imaging plane

ST. . . aperture

S1~S9. . . surface

Z. . . Optical axis

1 is a lens configuration diagram of a miniaturized lens according to a first embodiment of the present invention;

2 is a light path diagram of a first embodiment of the present invention;

3A is a field curvature diagram and a distortion representation diagram of a first embodiment of the present invention;

3B is a diagram showing a defocus modulation transfer function of the first embodiment of the present invention;

3C is a diagram showing a spatial frequency modulation transfer function according to a first embodiment of the present invention;

4 is a lens configuration diagram of a miniaturized lens according to a second embodiment of the present invention;

Figure 5 is a light path diagram of a second embodiment of the present invention

6A is a field diagram representation and a distortion representation diagram of a second embodiment of the present invention;

6B is a diagram showing a defocus modulation transfer function of a second embodiment of the present invention;

6C is a diagram showing a spatial frequency modulation transfer function according to a second embodiment of the present invention;

1. . . Miniaturized lens

L1. . . First lens

L2. . . Second lens

L3. . . Third lens

CG. . . Glass cover

IP. . . Imaging plane

ST. . . aperture

S1~S9. . . surface

Z. . . Optical axis

Claims (4)

A miniaturized lens comprising a first lens disposed along an optical axis and arranged from an object side to an image side: a first lens made of a glass material having a positive refractive power and at least one surface being an aspherical surface; A second lens, which is made of plastic material and has positive refractive power; a third lens is made of plastic material and has negative refractive power; in addition, the miniaturized lens satisfies the following conditions: 0.2<R1/F1< 0.7, wherein R1 is the radius of the first lens, and F1 is the effective focal length of the first lens. The miniaturized lens of claim 1, wherein at least one side of the second lens is an aspherical surface. The miniaturized lens of claim 1, wherein the third lens has at least one aspherical surface, and from the point where the optical axis passes to the periphery thereof, the refractive power is gradually converted from a negative refractive power to a positive refractive power. The miniaturized lens according to claim 1, wherein a radius of curvature of an optical axis region of the surface of the third lens on the image side (referring to an adjacent region including the optical axis passing through and a predetermined range thereof) is a positive value, The radius of curvature of the region to the periphery of the third lens is a negative value.