CN221261371U - Short-distance identification lens - Google Patents

Abstract

The invention discloses a short-distance identification lens, which is sequentially provided with a first lens (L1), a diaphragm (STO), a second lens (L2), a third lens (L3) and chip protection glass (CG) from an object surface to an image surface; the first lens (L1) is a positive lens, the object side surface is a convex surface, the image side surface is a concave surface, and the first lens and the second lens are aspheric; the second lens (L2) is a positive lens, the object side surface is a concave surface, the image side surface is a convex surface, and the second lens is an aspheric surface; the third lens (L3) is a negative lens, the object side surface is a concave surface, the image side surface is a concave surface, and the third lens is an aspheric surface; the three lenses are all made of plastic materials, so that the structure is simple, and the cost is low; the combination of the positive lens and the negative lens is beneficial to correcting curvature of field and distortion, and has the characteristics of small tolerance, good depth of field and the like.

Description

Short-distance identification lens

[ Field of technology ]

The invention relates to a short-distance identification lens.

[ Background Art ]

With development of technology and continuous popularization of computer application, recognition lenses such as bar code recognition, face recognition, fingerprint recognition and the like are visible everywhere in daily life. The invention relates to a short-distance identification lens with small tolerance and good depth of field, and the optical lens belongs to plastic materials, and has lower cost and wide application prospect compared with a glass lens.

[ Invention ]

Aiming at the defects and the practical requirements of the prior art, the invention provides the short-distance identification lens with small tolerance and good depth of field, which realizes miniaturization and saves cost.

In order to achieve the above object, the present invention provides a short-distance recognition lens, comprising a first lens (L1), a Stop (STO), a second lens (L2), a third lens (L3), and a chip protection glass (CG) sequentially arranged from an object plane to an image plane;

The first lens (L1) is a positive lens, the material is plastic, and the focal length is 1.35< f1/f <1.64; the object side surface is a convex surface and an aspheric surface, and the image side surface is a concave surface and an aspheric surface;

the second lens (L2) is a positive lens, the material is plastic, and the focal length is 2.95< f2/f <3.84; the object side surface is concave and aspheric, and the image side surface is convex and aspheric;

The third lens (L3) is a negative lens, the material is plastic, and the focal length is-1.51 < f3/f < -1.28; the object side surface is a concave surface and is an aspheric surface, and the image side surface is a concave surface and is an aspheric surface;

The close-range recognition lens satisfies the following relation:

0.43<TTL/f<0.65；

Wherein f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, and TTL is the axial distance from the object side surface to the imaging surface of the first lens; f is the effective focal length of the short-range recognition lens.

Preferably, the short-distance recognition lens satisfies the following relation:

1.52＜f/F＜1.72；

wherein F is the effective focal length of the short-distance recognition lens, and F is the F-number of the short-distance recognition lens.

Preferably, the short-distance recognition lens satisfies the following relation:

1.12＜∑TC/∑TE＜1.28；

Wherein Σtc is the sum of lens thicknesses of the first lens (L1), the second lens (L2) and the third lens (L3) on the optical axis, and Σte is the sum of axial thicknesses of the first lens (L1), the second lens (L2) and the third lens (L3) at the maximum aperture.

Preferably, the short-distance recognition lens satisfies the following relation:

0.25<T1/∑T<0.56；

0.25<T2/∑T<0.56；

0.25<T3/∑T<0.56；

Wherein Σt is the sum of the lens thicknesses of the first lens, the second lens and the third lens on the optical axis, and T1, T2 and T3 are the lens thicknesses of the first lens, the second lens and the third lens on the optical axis.

[ Description of the drawings ]

Fig. 1 is a schematic diagram of the structure of the short-distance recognition lens.

Fig. 2 is a vertical axis chromatic aberration diagram (mm) of the short-distance recognition lens.

Fig. 3 is a field curve (%) of the short-distance recognition lens.

Fig. 4 is a distortion chart (%) of the short-distance recognition lens.

[ Detailed description ] of the invention

The following describes specific embodiments of the present invention in detail.

The short-distance identification lens is characterized by comprising a first lens (L1), a diaphragm (STO), a second lens (L2), a third lens (L3) and chip protection glass (CG) which are sequentially arranged from an object plane to an image plane;

The first lens (L1) is a positive lens, the material is plastic, and the focal length is 1.35< f1/f <1.64; the object side surface is a convex surface and an aspheric surface, and the image side surface is a concave surface and an aspheric surface;

the second lens (L2) is a positive lens, the material is plastic, and the focal length is 2.95< f2/f <3.84; the object side surface is concave and aspheric, and the image side surface is convex and aspheric;

The third lens (L3) is a negative lens, the material is plastic, and the focal length is-1.51 < f3/f < -1.28; the object side surface is a concave surface and is an aspheric surface, and the image side surface is a concave surface and is an aspheric surface;

the close-range recognition lens satisfies the relation:

0.43<TTL/f<0.65；

Wherein f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, TTL is the on-axis distance from the object side surface to the imaging surface of the first lens, and f is the effective focal length of the short-distance recognition lens.

The negative lens and the positive lens of the short-distance recognition lens are mutually combined, and the focal length of each lens is relatively close to the focal length ratio of the short-distance recognition lens, so that the correction of field curvature and distortion is facilitated, the balancing of the focal power of each lens is facilitated, the turning capacity of each lens to light is equivalent, and the tolerance is reduced.

Preferably, the close-range recognition lens satisfies the following relation:

1.52＜f/F＜1.72；

wherein F is the effective focal length of the short-distance recognition lens, and F is the F-number of the short-distance recognition lens.

Under the condition that the light quantity is enough, the smaller the effective focal length of the lens is, the larger the f-number is, and the better the depth of field is; the ratio of the effective focal length to the f-number of the short-distance recognition lens can be within the range of 1.52-1.72.

Preferably, the close-range recognition lens satisfies the following relation:

1.12＜∑TC/∑TE＜1.28；

Wherein, Σtc is the sum of lens thicknesses of the first lens (L1), the second lens (L2) and the third lens (L3) on the optical axis, Σte is the sum of axial thicknesses of the first lens (L1), the second lens (L2) and the third lens (L3) at the maximum aperture.

The ratio of the medium thickness sum to the side thickness sum of all lenses of the short-distance recognition lens is close to 1, which indicates that the optical path of the light rays of the central view field and the edge view field is similar, and obvious bending images can not be formed when the light rays reach the image surface, thereby being beneficial to reducing distortion.

Preferably, the close-range recognition lens satisfies the following relation:

0.25<T1/∑T<0.56；

0.25<T2/∑T<0.56；

0.25<T3/∑T<0.56；

Wherein Σt is the sum of the lens thicknesses of the first lens, the second lens and the third lens on the optical axis, and T1, T2 and T3 are the lens thicknesses of the first lens, the second lens and the third lens on the optical axis. The thickness of each lens is controlled within the range, so that aberration correction and mutual compensation are facilitated, tolerance can be reduced, the total length of the lens is reduced, and ultrathin and miniaturized lenses are realized.

The following is a lens data table of an embodiment

TABLE 1 Structure parameter Table for short-distance identification lens

Table 2 an aspherical lens surface coefficient table for short distance recognition lens

Claims (4)

1. The utility model provides a close range identification camera lens which characterized in that: the lens comprises a first lens (L1), a diaphragm (STO), a second lens (L2), a third lens (L3) and chip protection glass (CG) which are arranged in sequence from an object plane to an image plane;

the first lens (L1) is a positive lens, the material is plastic, and the focal length is 1.35< f1/f <1.64; the object side surface is a convex surface and an aspheric surface, and the image side surface is a concave surface and an aspheric surface;

the second lens (L2) is a positive lens, the material is plastic, and the focal length is 2.95< f2/f <3.84; the object side surface is concave and aspheric, and the image side surface is convex and aspheric;

The third lens (L3) is a negative lens, the material is plastic, and the focal length is-1.51 < f3/f < -1.28; the object side surface is a concave surface and is an aspheric surface, and the image side surface is a concave surface and is an aspheric surface;

The close-range recognition lens satisfies the following relation:

0.43<TTL/f<0.65；

Wherein f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, TTL is the on-axis distance from the object side surface to the imaging surface of the first lens, and f is the effective focal length of the short-distance recognition lens.

2. A short-range identification lens as claimed in claim 1, wherein the following relation is satisfied:

1.52＜f/F＜1.72；

wherein F is the effective focal length of the short-distance recognition lens, and F is the F-number of the short-distance recognition lens.

3. A short-range identification lens as claimed in claim 1, wherein the following relation is satisfied:

1.12＜∑TC/∑TE＜1.28；

Wherein, Σtc is the sum of lens thicknesses of the first lens (L1), the second lens (L2) and the third lens (L3) on the optical axis, Σte is the sum of axial thicknesses of the first lens (L1), the second lens (L2) and the third lens (L3) at the maximum aperture.

4. A short-range identification lens as claimed in claim 1, wherein the following relation is satisfied:

0.25<T1/∑T<0.56；

0.25<T2/∑T<0.56；

0.25<T3/∑T<0.56；

Wherein Σt is the sum of the lens thicknesses of the first lens, the second lens and the third lens on the optical axis, and T1, T2 and T3 are the lens thicknesses of the first lens, the second lens and the third lens on the optical axis.