阅读说明：本技术 一种大靶面连续变倍远心镜头 (Large-target-surface continuous zoom telecentric lens ) 是由 王杰 龚昭宇 余飞鸿 于 2019-12-09 设计创作，主要内容包括：本发明公开了一种大靶面连续变倍远心镜头,所述远心镜头从物面起至像面依次包括具有正折射率光焦度的第一透镜组、具有正折射率光焦度的第二透镜组、具有正折射率光焦度的第三透镜组和具有正折射率光焦度的第四透镜组；其中第一透镜组、第四透镜组为固定组,第二透镜组、第三透镜组为移动组,当变倍远心镜头从低倍向高倍变倍时,第二透镜组向第一透镜组靠近,第三透镜组向第一透镜组靠近。本发明提供的大靶面连续变倍远心镜头能够实现匹配4/3英寸图像传感器,远心度小于0.05°,光学畸变小于0.02％,放大倍率0.5x-1x。(The invention discloses a large-target-surface continuous zooming telecentric lens, which sequentially comprises a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power and a fourth lens group with positive refractive power from an object surface to an image surface; when the zoom telecentric lens is zoomed from low power to high power, the second lens group approaches to the first lens group, and the third lens group approaches to the first lens group. The large-target-surface continuous zooming telecentric lens provided by the invention can realize matching with an 4/3-inch image sensor, the telecentricity is less than 0.05 degrees, the optical distortion is less than 0.02 percent, and the magnification ratio is 0.5x-1 x.)

1. The large-target-surface continuous zooming telecentric lens is characterized by comprising a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power and a fourth lens group with positive refractive power in sequence from an object surface to an image surface; when the zoom telecentric lens is zoomed from low power to high power, the second lens group approaches to the first lens group, and the third lens group approaches to the first lens group.

2. The large-target-surface continuous variable-power telecentric lens according to claim 1, wherein the first lens group, the second lens group, the third lens group and the fourth lens group satisfy the following relation:

0.15<|f_s2/f_s1|<0.9

0.1<|f_s3/f_s1|<0.85

0.75<|f_s4/f_s1|<1.25

wherein f is_s1Is the combined focal length of the first lens group, f_s2Is the combined focal length of the second lens group, f_s3Is the combined focal length of the third lens group, f_s4The combined focal length of the fourth lens group.

3. The large-target-surface continuous-zooming telecentric lens system of claim 2, wherein the first lens group S1 comprises a biconvex first lens G1 with positive power, a meniscus second lens G2 with positive power, a plano-convex third lens G3 with positive power and a biconcave fourth lens G4 with negative power, which are arranged in sequence from the object side to the image side; wherein the third lens G3 and the fourth lens G4 are cemented to form a first cemented lens group U1 with negative power and the focal length f of the first cemented lens group_U1And satisfies the relation:

0.1<|f_U1/f_s1|<0.3。

4. the large-target-surface continuous-zooming telecentric lens system of claim 2, wherein the second lens group S2 comprises a meniscus fifth lens G5 with negative power, a plano-convex sixth lens G6 with positive power and a meniscus seventh lens G7 with positive power, which are arranged in sequence from the object side to the image side; wherein the fifth lens G5 is cemented with the sixth lens G6 to form a second cemented lens group U2 with positive optical power and focal length f_U2And satisfies the relation:

1.0<|f_U2/f_s2|<1.8。

5. the large-target-surface continuous-zooming telecentric lens system of claim 2, wherein the third lens group S3 comprises a meniscus-shaped eighth lens G8 with positive power, a plano-convex ninth lens G9 with positive power and a plano-concave tenth lens G10 with negative power, which are arranged in order from the object side to the image side; wherein the ninth lens G9 is cemented with the tenth lens G10 to form a third cemented lens group U3 with positive optical power, and the focal length f of the second cemented lens group is_U3And satisfies the relation:

3<|f_U3/f_s3|<4.5。

6. the large-target-surface continuous-zooming telecentric lens system of claim 5, wherein the telecentric lens system further comprises a stop disposed between the eighth lens group G8 and the third cemented lens group U3.

7. The large-target-surface continuous variable-magnification telecentric lens according to claim 6, wherein the diaphragm is circular, follows the movement of the third lens group S3 and has a constant diameter.

8. The large-target-surface continuous-zooming telecentric lens system of claim 2, wherein the fourth lens group S4 comprises a biconcave eleventh lens G11 with negative optical power, a plano-convex twelfth lens G12 with positive optical power and a plano-convex thirteenth lens G13 with positive optical power, which are arranged in sequence from the object side to the image side.

9. The large-target-surface continuous variable-power telecentric lens according to claim 1, wherein the first lens group, the second lens group, the third lens group and the fourth lens group are all spherical lenses.

10. The large-target-surface continuous-zooming telecentric lens system of claim 1, wherein the air separation between the first lens group S1 and the second lens group S2 is D1, the air separation between the second lens group S2 and the third lens group S3 is D2, the air separation between the third lens group S3 and the fourth lens group S4 is D3, and D1, D2 and D3 satisfy the following relations:

0.3<|D₁/D₂|<7.5

0.25<|D₁/D₃|<7.5

0.15<|D₂/D₃|<4.25。

Technical Field

The invention belongs to the technical field of optical lenses, and particularly relates to a large-target-surface continuous zoom telecentric lens.

Background

The machine vision system is to use a machine to replace human eyes for measurement and judgment. Optical lenses are an important component of machine vision systems. Compared with the common imaging lens, the telecentric lens can effectively correct the parallax of the common imaging lens due to the unique light path structure, so that the imaging magnification can be kept unchanged within a certain object distance range, and the telecentric lens is widely applied to various machine vision detection systems.

The telecentric lens used for the machine vision inspection system in the current market mainly comprises the following parts:

the first magnification-invariant telecentric lens. The telecentric lens with constant magnification can be designed with a sensor matched with a large target surface, so that the telecentric lens has a larger visual field range and can well ensure the detection precision, but because the magnification is fixed, the lenses with different magnifications need to be replaced for detecting different objects, and the used scene is limited.

And the second continuous zoom telecentric lens. In order to achieve the purpose of zooming, the continuous zooming telecentric lens in the current market designs a matched sensor with a smaller target surface and a smaller observation visual field range. Meanwhile, due to poor telecentricity, when the lens is measured within the range of depth of field, the obtained measurement values are different, and the measurement result is not accurate enough. For example, chinese patent publication No. CN204188874U discloses a zoom telecentric lens, which relates to optical technology. The image plane from the object plane sequentially comprises: a first lens group having positive refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, and a fifth lens group having positive refractive power; when the zoom telecentric lens is zoomed from low power to high power, the second lens group approaches to the first lens group, and the fourth lens group approaches to the third lens group. Chinese patent publication No. CN109471244A discloses a large-field double telecentric lens based on machine vision, which includes: the first group of lenses, the second group of lenses, the third group of lenses, the fourth group of lenses and the fifth group of lenses are arranged in sequence from left to right in the incident direction of a light path; wherein the first group of lenses are plano-convex lenses with positive focal power; the second group of lenses are convex-concave lenses with positive focal power; the third group of lenses are biconcave lenses with negative focal power; a fourth lens group double cemented lens; the fifth lens group is a biconvex lens with positive focal power; and an aperture diaphragm is arranged between the third group of lenses and the fourth group of lenses.

Therefore, the matching 4/3-inch image sensor can be realized on the market at present, the telecentricity is less than 0.05 degrees, the optical distortion is less than 0.02 percent, and almost no variable-power telecentric lens with the magnification ratio of 0.5x-1x exists. Therefore, a zoom telecentric lens matched with an 4/3-inch image sensor, which has telecentricity less than 0.05 degrees, optical distortion less than 0.02 percent and magnification ratio of 0.5x-1x, is urgently needed to be developed to fill the market vacancy.

Disclosure of Invention

The invention aims to provide a large-target-surface continuous zooming telecentric lens which can be matched with an 4/3-inch image sensor, and has the telecentricity of less than 0.05 degrees, the optical distortion of less than 0.02 percent and the magnification of 0.5x-1 x.

The technical scheme adopted by the invention is as follows:

the large-target-surface continuous zooming telecentric lens is characterized by comprising a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power and a fourth lens group with positive refractive power in sequence from an object surface to an image surface; when the zoom telecentric lens is zoomed from low power to high power, the second lens group approaches to the first lens group, and the third lens group approaches to the first lens group.

Further, the first lens group, the second lens group, the third lens group and the fourth lens group satisfy the relation:

0.15<|f_s2/f_s1|<0.9

0.1<|f_s3/f_s1|<0.85

0.75<|f_s4/f_s1|<1.25

wherein f is_s1Is the combined focal length of the first lens group, f_s2Is the combined focal length of the second lens group, f_s3Is the combined focal length of the third lens group, f_s4The combined focal length of the fourth lens group.

Further, the first lens group S1 includes a biconvex first lens G1 having positive optical power, having positive focal power, disposed in order from the object side to the image sideA meniscus-shaped second lens G2 of power, a plano-convex third lens G3 having positive power, and a biconcave fourth lens G4 having negative power; wherein the third lens G3 and the fourth lens G4 are cemented to form a first cemented lens group U1 with negative power and the focal length f of the first cemented lens group_U1And satisfies the relation:

0.1<|f_U1/f_s1|<0.3。

further, the second lens group S2 includes a meniscus fifth lens G5 having negative power, a plano-convex sixth lens G6 having positive power, and a meniscus seventh lens G7 having positive power, which are arranged in this order from the object side to the image side; wherein the fifth lens G5 is cemented with the sixth lens G6 to form a second cemented lens group U2 with positive optical power and focal length f_U2And satisfies the relation:

1.0<|f_U2/f_s2|<1.8。

further, the third lens group S3 includes a meniscus eighth lens G8 having positive power, a plano-convex ninth lens G9 having positive power, and a plano-concave tenth lens G10 having negative power, which are arranged in this order from the object side to the image side. Wherein the ninth lens G9 is cemented with a tenth lens G10 to form a third cemented lens group U3 having positive optical power, the second cemented lens group having a focal length f_U3And satisfies the relation:

3<|f_U3/f_s3|<4.5。

still further, the telecentric lens further comprises a stop disposed between the eighth lens G8 and the third cemented lens group U3.

Further, the stop is circular, follows the movement of the third lens group S3 and has a constant diameter.

Further, the fourth lens group S4 includes a biconcave eleventh lens G11 having negative optical power, a plano-convex twelfth lens G12 having positive optical power, and a plano-convex thirteenth lens G13 having positive optical power, which are arranged in this order from the object side to the image side.

Preferably, the first lens group, the second lens group, the third lens group and the fourth lens group are all spherical lenses. That is, the first lens G1, the second lens G2, the third lens G3, the fourth lens G4, the fifth lens G5, the sixth lens G6, the seventh lens G7, the eighth lens G8, the ninth lens G9, the tenth lens G10, the eleventh lens G11, the twelfth lens G12, and the thirteenth lens G13 are all spherical lenses.

Preferably, the air interval between the first lens group S1 and the second lens group S2 is D1, the air interval between the second lens group S2 and the third lens group S3 is D2, the air interval between the third lens group S3 and the fourth lens group S4 is D3, and D1, D2 and D3 satisfy the following relations:

0.3<|D₁/D₂|<7.5

0.25<|D₁/D₃|<7.5

0.15<|D₂/D₃|<4.25。

the invention has the advantages that the four-component structure with simple structure is adopted, and the change of the magnification of the lens is realized through the matching of the moving group and the zoom group. The large-target-surface continuous zoom telecentric lens provided by the invention realizes the zoom range of 0.5x-1x, and clear imaging can be realized without readjusting the object distance and the image distance in the zoom process; the sensor can be matched with a maximum target surface 4/3 inches, and the observable visual field range is larger; the object space telecentricity is less than 0.05 degrees, so that the accuracy of the measured data and the repeatability of the measured data in the field depth range are ensured; the optical distortion is less than 0.02% under all magnification conditions, and the shape of the object to be measured is truly restored; the method has ultrahigh object space resolution, and the maximum object space resolution reaches 4.9 mu m.

Drawings

FIG. 1 is a schematic view of an optical system of a large-target-surface continuous variable-magnification telecentric lens in example 1;

FIG. 2 is a comparison of the low magnification to the high magnification of the large target surface continuous variable magnification telecentric lens in example 1;

FIG. 3 is the MTF curve of the large-target-surface continuous variable-power telecentric lens in the embodiment 1 at low magnification;

FIG. 4 is the MTF curve of the large-target-surface continuous variable-power telecentric lens in the embodiment 1 at high magnification;

FIG. 5 is a low-magnification distortion curve diagram of the large-target-surface continuous variable-magnification telecentric lens in example 1;

FIG. 6 is a graph showing the distortion of the large-target-surface continuous variable-magnification telecentric lens in example 1 at high magnification;

FIG. 7 is a dot-column diagram of the large-target-surface continuous variable-magnification telecentric lens in example 1 at low magnification;

FIG. 8 is a dot-column diagram of the large-target-surface continuous variable-magnification telecentric lens in example 1 at high magnification;

FIG. 9 is a schematic view of an optical system of a large-target-surface continuous variable-magnification telecentric lens according to embodiment 2;

FIG. 10 is a schematic view of an optical system of a large-target-surface continuous variable-magnification telecentric lens in embodiment 3.

Detailed Description

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

As shown in fig. 1, the large target surface continuous zoom telecentric lens provided by the present invention sequentially comprises, from the object plane to the image plane:

the first lens group S1 having positive refractive power: a biconvex first lens G1 with positive focal power, a meniscus second lens G2 with positive focal power, a plano-convex third lens G3 with positive focal power and a biconcave fourth lens G4 with negative focal power which are arranged in sequence from the object side to the image side; the third lens G3 and the fourth lens G4 are cemented to form a first cemented lens group U1 with negative focal power, and the focal length of the first cemented lens group is f_U1And satisfies the relation:

0.1<|f_U1/f_s1|<0.3；

a second lens group having positive refractive power: a meniscus fifth lens G5 having negative power, a plano-convex sixth lens G6 having positive power, and a meniscus seventh lens G7 having positive power, which are arranged in this order from the object side to the image side; wherein the fifth lens G5 and the sixth lens G6 are cemented to form a second cemented lens group U2 with positive focal power, and the focal length of the second cemented lens group is f_U2And satisfies the relation:

1.0<|f_U2/f_s2|<1.8；

a third lens group having positive refractive power: a meniscus-shaped eighth lens G8 having positive power, a plano-convex ninth lens G9 having positive power, and a plano-concave tenth lens G10 having negative power, which are arranged in this order from the object side to the image side; wherein the ninth lens G9 and the tenth lens G10 are cemented to form a third cemented lens group U3 with positive focal power, and the focal length f of the second cemented lens group_U3And satisfies the relation:

3<|f_U3/f_s3|<4.5；

wherein a circular diaphragm is arranged between the eighth lens G8 and the third cemented lens group U3, and the diaphragm moves along with the third lens group S3 with the diameter kept unchanged

A fourth lens group having positive refractive power: a biconcave eleventh lens G11 having negative power, a plano-convex twelfth lens G12 having positive power, and a plano-convex thirteenth lens G13 having positive power, which are arranged in this order from the object side to the image side.

The first lens group S1 and the fourth lens group S4 are fixed groups, the second lens group S2 and the third lens group S3 are moving groups, and when the variable power telecentric lens is changed from low power to high power, the second lens group S2 approaches the first lens group S1, and the third lens group S3 approaches the first lens group S1.

Wherein, the first lens group S1, the second lens group S2, the third lens group S3 and the fourth lens group S4 satisfy the relation:

0.15<|f_s2/f_s1|<0.9

0.1<|f_s3/f_s1|<0.85

0.75<|f_s4/f_s1|<1.25

wherein f is_s1Is the combined focal length, f, of the first lens group S1_s2Is the combined focal length, f, of the second lens group S2_s3Is the combined focal length, f, of the third lens group S3_s4Is the combined focal length of the fourth lens group S4.

Wherein, the air space between the first lens group S1 and the second lens group S2 is D1, the air space between the second lens group S2 and the third lens group S3 is D2, and the air space between the third lens group S3 and the fourth lens group S4 is D3, which satisfies the following relation:

0.3<|D₁/D₂|<7.5

0.25<|D₁/D₃|<7.5

0.15<|D₂/D₃|<4.25。

in the invention, the optical system structure composed of the lens achieves the following optical indexes:

magnification: 0.5x-1.0 x;

working distance: 80 mm;

target surface size: 4/3 inches;

object space telecentricity: less than 0.05 °;

optical distortion: less than 0.02%;

maximum resolution: 4.9 μm;

applicable spectral line range: 450-700 nm.