CN211857044U

CN211857044U - Double-telecentric lens

Info

Publication number: CN211857044U
Application number: CN202020543737.9U
Authority: CN
Inventors: 陈建伟
Original assignee: Guangdong OPT Machine Vision Co Ltd
Current assignee: Guangdong OPT Machine Vision Co Ltd
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2020-11-03
Anticipated expiration: 2030-04-14

Abstract

The utility model belongs to the technical field of optical device, concretely relates to two telecentric mirror heads, including optical device, optical device sets gradually the first lens G1 that has positive focal power and biconvex structure, the second lens G2 that has negative focal power and meniscus structure, the third lens G3 that has positive focal power and biconvex structure, the fourth lens G4 that has negative focal power and biconcave or plano-concave structure, beam splitter prism P, the fifth lens G5 that has negative focal power and biconcave structure, the sixth lens G6 that has positive focal power and meniscus structure and the seventh lens G7 that has positive focal power and meniscus or plano-convex structure to the image space by the object space, second lens G2 third lens G3 and third cemented lens U1 is constituteed to fourth lens G4. The utility model discloses can rectify the colour difference that high magnification telecentric lens exists, reduce the aberration that single refracting surface of lens bore simultaneously, effectively reduce optical device's tolerance sensitivity.

Description

Double-telecentric lens

Technical Field

The utility model belongs to the technical field of optical device, concretely relates to two telecentric mirror heads.

Background

In a machine vision precision measurement system, the problems of different magnification ratios, parallax, large distortion and the like caused by the change of object distance of a common industrial lens are difficult to meet the requirement of high-precision detection, and a telecentric lens can be in a certain object distance range, so that the magnification ratio of an obtained image cannot change along with the change of the object distance, and can be divided into object-side telecentricity and image-side telecentricity according to the design principle of a telecentric optical path.

However, the length and size of the double telecentric lenses in the market are large, the numerical aperture is small, the small numerical aperture can cause the resolution of the telecentric lens to be low, and the existing telecentric lens can not meet the requirement of keeping the total length of a short system and simultaneously having high resolution; the design difficulty and cost control are limited, and the high-resolution double telecentric lens on the market is concentrated on low magnification at present, generally below 0.5 times; the resolution of the double telecentric lens with high magnification is not high, and the application requirements of high magnification and high resolution can not be met. The resolution of the telecentric lens with high magnification is improved, so that the design difficulty is increased, and the tolerance sensitivity is also improved.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a: aiming at the defects of the prior art, the double telecentric lens is provided, which can correct chromatic aberration existing in the high-magnification telecentric lens, reduce the aberration born by a single refraction surface of the lens and effectively reduce the tolerance sensitivity of the optical device.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a double telecentric lens comprises an optical device, wherein the optical device is provided with a first lens G1 with positive focal power and a double convex structure, a second lens G2 with negative focal power and a meniscus structure, a third lens G3 with positive focal power and a double convex structure, a fourth lens G4 with negative focal power and a double concave or plano-concave structure, a beam splitter prism P, a fifth lens G5 with negative focal power and a double concave structure, a sixth lens G6 with positive focal power and a meniscus structure, and a seventh lens G7 with positive focal power and a meniscus or plano-convex structure in sequence from an object side to an image side, and the second lens G2, the third lens G3 and the fourth lens G4 form a third cemented lens U1.

As an improvement of two telecentric mirror heads, first lens G1 with preceding battery of lenses Ga is constituteed to three cemented lens U1, the focus of preceding battery of lenses Ga is fGa, fifth lens G5 sixth lens G6 reaches back battery of lenses Gb is constituteed to seventh lens G7, the focus of back battery of lenses Gb is fGb.

As an improvement of a pair of telecentric lens, first lens G1's focus is f1, first lens G1's focus f1 with preceding lens group Ga's focus fGa satisfies the relational expression: 0.8< | f1/fGa | < 1.8.

As an improvement of a pair of telecentric lens, the focus of three cemented lens U1 is fu1, with focus fGa of preceding lens group Ga satisfies the relational expression: 3< | fu1/fGa | < 5.

As an improvement of two telecentric mirror heads, the refracting index of second lens G2 is n2, and the abbe number is v2, and it satisfies the relational expression: 1.65< n2<1.75, 50< v2< 60; the refractive index of the third lens G3 is n3, the Abbe number is v3, and the third lens G3 satisfies the relation: 1.48< n3<1.55, 70< v3< 85; the refractive index of the fourth lens G4 is n4, the Abbe number is v4, and the relation is satisfied: 1.70< n4<1.80, 45< v4< 55.

As an improvement of two telecentric mirror heads, the focus of fifth lens G5 is f5, with the focus fGb of rear lens group Gb satisfies the relational expression: 0.25< | f5/fGb | < 0.5.

As an improvement of two telecentric mirror heads, the focus of sixth lens G6 is f6, with the focus fGb of rear lens group Gb satisfies the relational expression: 0.5< | f6/fGb | < 1.5.

As an improvement of two telecentric lens systems, the focus of seventh lens G7 is f7, with the focus fGb of rear lens group Gb satisfies the relational expression: 0.5< | f7/fGb | < 1.5.

As an improvement of two telecentric mirror heads, optical device' S diaphragm S is located fifth lens G5 is preceding, beam splitter prism P sets up fourth lens G4 with between the diaphragm S, beam splitter prism P is used for leading-in coaxial lighting source.

As an improvement of the double telecentric lens of the present invention, the first lens G1 is made of low dispersion glass material.

The beneficial effects of the utility model reside in that, the utility model discloses an optical device, optical device sets gradually the first lens G1 that has positive focal power and biconvex structure, the second lens G2 that has negative focal power and meniscus structure, the third lens G3 that has positive focal power and biconvex structure, the fourth lens that has negative focal power and biconcave or plano-concave structure, beam splitter prism P, the fifth lens G5 that has negative focal power and biconcave structure, the sixth lens G6 that has positive focal power and meniscus structure, and the seventh lens G7 that has positive focal power and meniscus or plano-convex structure to the image space, second lens G2 third lens G3 reaches third cemented lens U1 is constituteed to fourth lens G4. In the optical device, the utilization of the first lens with low dispersion and the tri-cemented lens is beneficial to correcting chromatic aberration existing in the high-magnification telecentric lens, and meanwhile, the tri-cemented lens is beneficial to reducing the aberration born by a single refraction surface of the lens, so that the tolerance sensitivity of the optical device can be effectively reduced. The object space telecentricity is less than 0.1 degree, and the image space telecentricity is less than 0.2 degree; distortion is less than 0.1%; the MTF is larger than 0.3 at 140lp/mm, and the requirement of the high-resolution double telecentric lens is met.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a light path diagram of the optical device of the present invention.

Fig. 3 is a distortion diagram of the optical device of the present invention.

Fig. 4 is an MTF diagram of the optical device of the present invention.

Detailed Description

As used in the specification and in the claims, certain terms are used to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. "substantially" means within an acceptable error range, and a person skilled in the art can solve the technical problem within a certain error range to substantially achieve the technical effect.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", horizontal "and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, detachable connections, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

The present invention will be described in further detail with reference to fig. 1 to 4, but the present invention is not limited thereto.

A double telecentric lens comprises an optical device, wherein the optical device is provided with a first lens G1 with positive focal power and a double convex structure, a second lens G2 with negative focal power and a meniscus structure, a third lens G3 with positive focal power and a double convex structure, a fourth lens G4 with negative focal power and a double concave or plano-concave structure, a beam splitter prism P, a fifth lens G5 with negative focal power and a double concave structure, a sixth lens G6 with positive focal power and a meniscus structure, a seventh lens G7 with positive focal power and a meniscus or plano-convex structure, and a third cemented lens U1 consisting of the second lens G2, the third lens G3 and the fourth lens G4 in sequence from an object side to an image side.

Preferably, the first lens G1 and the cemented triplet U1 constitute a front lens group Ga, the focal length of the front lens group Ga is fGa, the fifth lens G5, the sixth lens G6 and the seventh lens G7 constitute a rear lens group Gb, and the focal length of the rear lens group Gb is fGb.

Preferably, the focal length of the first lens G1 is f1, and the focal length f1 of the first lens G1 and the focal length fGa of the front lens group Ga satisfy the relation: 0.8< | f1/fGa | < 1.8.

Preferably, the focal length of the triplexed cemented lens U1 is fu1, and satisfies the relation with the focal length fGa of the front lens group Ga: 3< | fu1/fGa | < 5.

Preferably, the refractive index of the second lens G2 is n2, and the abbe number is v2, which satisfy the relation: 1.65< n2<1.75, 50< v2< 60; the refractive index of the third lens G3 is n3, and the abbe number is v3, which satisfy the relation: 1.48< n3<1.55, 70< v3< 85; the refractive index of the fourth lens G4 is n4, and the abbe number is v4, which satisfies the relation: 1.70< n4<1.80, 45< v4< 55.

Preferably, the focal length of the fifth lens G5 is f5, and satisfies the following relation with the focal length fGb of the rear lens group Gb: 0.25< | f5/fGb | < 0.5.

Preferably, the focal length of the sixth lens G6 is f6, and satisfies the following relation with the focal length fGb of the rear lens group Gb: 0.5< | f6/fGb | < 1.5.

Preferably, the focal length of the seventh lens G7 is f7, and satisfies the following relation with the focal length fGb of the rear lens group Gb: 0.5< | f7/fGb | < 1.5.

Preferably, the stop S of the optical device is located in front of the fifth lens G5, and the beam splitter prism P for guiding the coaxial illumination light source is disposed between the fourth lens G4 and the stop S. And is guided into a coaxial illumination light source or other imaging systems through a beam splitter prism P.

Preferably, the material of the first lens G1 is a low dispersion glass material. In the optical device, the utilization of the first lens with low dispersion and the tri-cemented lens is beneficial to correcting chromatic aberration existing in the high-magnification telecentric lens, and meanwhile, the tri-cemented lens is beneficial to reducing the aberration born by a single refraction surface of the lens, so that the tolerance sensitivity of the optical device can be effectively reduced.

In this example, the data for the optical device is as follows:

in this example, fGa-46.29 mm, fGb-52.88 mm, f 1-60.65 mm, fu 1-193.7 mm, f 5-18.92 mm, f 6-54.2 mm, f 7-48.59 mm; can obtain the product

|f1/fGa|＝1.31，|fu1/fGa|＝4.18，|f5/fGb|＝0.36，

|f6/fGb|＝1.02，|f7/fGb|＝0.92。

Satisfy the relation:

0.8<|f1/fGa|<1.8，3<|fu1/fGa|<5，0.25<|f5/fGb|<0.5，

0.5<|f6/fGb|<1.5，0.5<|f7/fGb|<1.5。

in this example, the working distance of the double telecentric lens optics is 114mm, the conjugate distance of the object image is 255mm, the half-image height is 5.5mm, the effective aperture value is 6.5, and the magnification is 1.

According to the utility model discloses optical device can reach: the object space telecentricity is less than 0.1 degree, and the image space telecentricity is less than 0.2 degree; distortion is less than 0.1%; the MTF is larger than 0.3 at 140lp/mm, and the requirement of the high-resolution double telecentric lens is met.

Variations and modifications to the above-described embodiments may become apparent to those skilled in the art from the disclosure and teachings of the above description. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious modifications, replacements or variations made by those skilled in the art on the basis of the present invention belong to the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A double telecentric lens is characterized in that: the optical device comprises an optical device, wherein a first lens G1 with positive focal power and a double convex structure, a second lens G2 with negative focal power and a meniscus structure, a third lens G3 with positive focal power and a double convex structure, a fourth lens G4 with negative focal power and a double concave or plano-concave structure, a beam splitter prism P, a fifth lens G5 with negative focal power and a double concave structure, a sixth lens G6 with positive focal power and a meniscus structure, and a seventh lens G7 with positive focal power and a meniscus or plano-convex structure are sequentially arranged from an object side to an image side, and the second lens G2, the third lens G3 and the fourth lens G4 form a three cemented lens U1.

2. A double telecentric lens system as recited in claim 1, wherein: the first lens G1 and the third cemented lens U1 form a front lens group Ga, the focal length of the front lens group Ga is fGa, the fifth lens G5, the sixth lens G6 and the seventh lens G7 form a rear lens group Gb, and the focal length of the rear lens group Gb is fGb.

3. A double telecentric lens system as recited in claim 2, wherein: the focal length of the first lens G1 is f1, and the focal length f1 of the first lens G1 and the focal length fGa of the front lens group Ga satisfy the relation: 0.8< | f1/fGa | < 1.8.

4. A double telecentric lens system as recited in claim 2, wherein: the focal length of the triplexed cemented lens U1 is fu1, and satisfies the relation with the focal length fGa of the front lens group Ga: 3< | fu1/fGa | < 5.

5. A double telecentric lens system as recited in claim 1, wherein: the refractive index of the second lens G2 is n2, the Abbe number is v2, and the relation is satisfied: 1.65< n2<1.75, 50< v2< 60; the refractive index of the third lens G3 is n3, the Abbe number is v3, and the third lens G3 satisfies the relation: 1.48< n3<1.55, 70< v3< 85; the refractive index of the fourth lens G4 is n4, the Abbe number is v4, and the relation is satisfied: 1.70< n4<1.80, 45< v4< 55.

6. A double telecentric lens system as recited in claim 2, wherein: the focal length of the fifth lens G5 is f5, and the focal length fGb of the rear lens group Gb satisfies the relation: 0.25< | f5/fGb | < 0.5.

7. A double telecentric lens system as recited in claim 2, wherein: the focal length of the sixth lens G6 is f6, and the focal length fGb of the rear lens group Gb satisfies the relation: 0.5< | f6/fGb | < 1.5.

8. A double telecentric lens system as recited in claim 2, wherein: the focal length of the seventh lens G7 is f7, and the focal length fGb of the rear lens group Gb satisfies the relation: 0.5< | f7/fGb | < 1.5.

9. A double telecentric lens system as recited in claim 1, wherein: the diaphragm S of the optical device is positioned in front of the fifth lens G5, and the beam splitter prism P is arranged between the fourth lens G4 and the diaphragm S and is used for leading in a coaxial illumination light source.

10. A double telecentric lens system as recited in claim 1, wherein: the material of the first lens G1 is a low-dispersion glass material.