CN114384676B

CN114384676B - Achromatic object space telecentric lens

Info

Publication number: CN114384676B
Application number: CN202210061295.8A
Authority: CN
Inventors: 陈建伟
Original assignee: Guangdong OPT Machine Vision Co Ltd
Current assignee: Guangdong OPT Machine Vision Co Ltd
Priority date: 2022-01-19
Filing date: 2022-01-19
Publication date: 2023-05-05
Anticipated expiration: 2042-01-19
Also published as: CN114384676A

Abstract

The invention discloses an achromatic object side telecentric lens, which consists of a front group lens, a diaphragm and a rear group lens which are sequentially arranged from an object side to an image side; the front group lens consists of a first lens with positive focal power and a biconvex structure, a second lens with positive focal power and a biconvex structure, a third lens with negative focal power and a biconcave structure and a fourth lens with positive focal power, and the second lens, the third lens and the fourth lens form a first cemented lens; the rear group lens is composed of a fifth lens having negative power, a biconcave structure, and a sixth lens having positive power, a biconvex or plano-convex structure, and the fifth lens and the sixth lens constitute a second cemented lens. According to the achromatic object side telecentric lens, through the front group lens, the diaphragm and the rear group lens which are sequentially arranged from the object side to the image side, chromatic aberration can be eliminated, and the achromatic object side telecentric lens has higher magnification and resolution.

Description

Achromatic object space telecentric lens

Technical Field

The invention relates to the technical field of optical system and device design, in particular to an achromatic object side telecentric lens.

Background

In a precision optical measurement system, there are the following problems with using a general industrial lens: the object distance change can cause different magnifications, has the problems of parallax, large distortion and the like, and is difficult to meet the requirement of high-precision detection. The telecentric lens can reduce or even eliminate the problems, the obtained image magnification can not change along with the change of the object distance within a certain object distance range, and the principle advantages of the telecentric lens are very suitable for the field of precise measurement and detection.

The existing high-resolution telecentric lens on the market is concentrated on low magnification, the aperture of the telecentric lens with the magnification of more than 1 time is smaller, the resolution is not high, the application requirements of high magnification and high resolution are not met, the magnification or numerical aperture of the telecentric lens is increased, the correction difficulty of chromatic aberration is increased, and if chromatic aberration is not corrected or eliminated, part of areas in an image can present unattractive color edges, so that the image quality is reduced.

Disclosure of Invention

The present invention aims to provide an achromatic object-side telecentric lens, which solves or at least partially solves the above technical problems.

To achieve the purpose, the invention adopts the following technical scheme:

an achromatic object side telecentric lens comprises a front group lens, a diaphragm and a rear group lens which are sequentially arranged from an object side to an image side;

the front group lens consists of a first lens with positive focal power and a biconvex structure, a second lens with positive focal power and a biconvex structure, a third lens with negative focal power and a biconcave structure and a fourth lens with positive focal power, and the second lens, the third lens and the fourth lens form a first cemented lens;

the rear group lens is composed of a fifth lens having negative power, a biconcave structure, and a sixth lens having positive power, a biconvex or plano-convex structure, and the fifth lens and the sixth lens constitute a second cemented lens.

Optionally, the front group lens has a combined focal length fA, the rear group lens has a combined focal length fB, and they satisfy the following relation: 0.1< |fA/fB| <0.35.

Optionally, the focal length of the first lens is f1, and the combined focal length fA of the first lens and the front group lens satisfies the following relationship: 0.5< |f1/fA| <1.5.

Optionally, the first lens is made of a high refractive index glass material.

Optionally, the focal length of the second lens is f2, and the combined focal length fA of the front group lens satisfies the following relationship: 0.6< |f2/fA| <1.6.

Optionally, the refractive index of the second lens is n2, the abbe number is v2, which satisfies the relation: 1.45< n2<1.55;70< v2<85.

Optionally, the focal length of the third lens is f3, and the combined focal length fA of the third lens and the front group lens satisfies the following relationship: 0.2< |f3/fA| <0.7.

Optionally, the focal length of the fourth lens is f4, and the combined focal length fA of the fourth lens and the front group lens satisfies the following relationship: 0.6< |f4/fA| <1.6.

Optionally, the fourth lens is made of low-dispersion glass material.

Optionally, the lens further comprises a prism, and the prism is arranged between the fourth lens and the diaphragm.

Compared with the prior art, the embodiment of the invention has the following beneficial effects:

according to the achromatic object side telecentric lens, chromatic aberration can be eliminated through the front group lens, the diaphragm and the rear group lens which are sequentially arranged from the object side to the image side, and the achromatic object side telecentric lens has higher magnification and resolution.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

The structures, proportions, sizes, etc. shown in the present specification are shown only for the purposes of illustration and description, and are not intended to limit the scope of the invention, which is defined by the claims, so that any structural modifications, changes in proportions, or adjustments of sizes, which do not affect the efficacy or the achievement of the present invention, should fall within the scope of the invention.

Fig. 1 is a block diagram of an achromatic telecentric lens according to an embodiment of the present invention;

FIG. 2 is another block diagram of an achromatic telecentric lens according to an embodiment of the present invention;

FIG. 3 is an axial chromatic aberration diagram of an achromatic telecentric lens according to an embodiment of the present invention;

fig. 4 is an MTF diagram of an achromatic telecentric lens according to an embodiment of the present invention.

Illustration of:

A. a front group lens; B. a rear group lens; g1, a first lens; g2, a second lens; g3, a third lens; g4, fourth lens; g5, fifth lens; g6, sixth lens; p, a prism; s, a diaphragm; u1, a first cemented lens; u2, a second cemented lens.

Detailed Description

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is apparent that the embodiments described below are only some embodiments of the present invention, not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Referring to fig. 1, the present embodiment provides an achromatic object-side telecentric lens, which includes a front group lens a, a diaphragm S, and a rear group lens B sequentially arranged from an object side to an image side, so as to not only eliminate chromatic aberration, but also have higher magnification and resolution.

Specifically, the front group lens a is composed of a first lens G1 having positive power, a biconvex structure, a second lens G2 having positive power, a third lens G3 having negative power, a biconcave structure, and a fourth lens G4 having positive power, the second lens G2, the third lens G3, and the fourth lens G4 constituting a first cemented lens U1; the rear group lens B is composed of a fifth lens G5 having a negative power, a biconcave structure, and a sixth lens G6 having a positive power, a biconvex or plano-convex structure, and the fifth lens G5 and the sixth lens G6 constitute a second cemented lens U2.

It should be noted that, the front group lens a formed by the first lens G1 and the first cemented lens U1 takes on the main tasks of aberration correction and balancing of the optical system, and the first cemented lens U1 and the low-dispersion material are beneficial to correcting the chromatic aberration of the optical system, so as to achieve the effect of eliminating the chromatic aberration. The rear group lens B can balance the residual aberration of the front group lens a, correcting curvature of field.

As an alternative implementation of this embodiment, the front group lens a has a combined focal length fA, and the rear group lens B has a combined focal length fB, which satisfy the following relation: 0.1< |fA/fB| <0.35.

As an alternative implementation manner of this embodiment, the focal length of the first lens G1 is f1, and the combined focal length fA of the front group lens a satisfies the following relationship: 0.5< |f1/fA| <1.5.

Specifically, the first lens G1 is made of a high refractive index glass material, and the curvature of the lens can be reduced by using the high refractive index glass material, so that the high-order aberration is reduced, and the tolerance sensitivity is reduced.

As an alternative implementation manner of this embodiment, the focal length of the second lens G2 is f2, and the combined focal length fA of the front group lens a satisfies the following relationship: 0.6< |f2/fA| <1.6.

Further, the refractive index of the second lens G2 is n2, the abbe number is v2, which satisfies the relation: 1.45< n2<1.55;70< v2<85.

As an alternative implementation manner of this embodiment, the focal length of the third lens G3 is f3, and the combined focal length fA of the front group lens a satisfies the following relationship: 0.2< |f3/fA| <0.7.

As an alternative implementation manner of this embodiment, the focal length of the fourth lens G4 is f4, and the combined focal length fA of the front group lens a satisfies the following relationship: 0.6< |f4/fA| <1.6.

Specifically, the fourth lens G4 is made of a low-dispersion glass material.

Referring to fig. 2, in another embodiment of the present application, the achromatic telecentric lens further includes a prism P disposed between the fourth lens G4 and the stop S, through which a coaxial illumination source or other imaging system can be introduced.

In another embodiment of the present application, an optical system of an achromatic telecentric lens is provided with the following table data, the axial chromatic aberration diagram and the MTF diagram of which are shown with reference to fig. 3 and 4.

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In this embodiment, the working distance of the optical system of the achromatic telecentric lens is 114mm, the object-image conjugate distance is 273.6mm, the image plane size is 11mm, the working F-number is 7.5, and the magnification is 1.5 times. The combined focal length of the front group lens a is fa=61.35 mm; the combined focal length of the rear group lens B is fb= -257.76mm; the focal length of the first lens G1 is f1= 60.04mm; the focal length of the second lens G2 is f2=62.54 mm; the focal length of the third lens G3 is f3= -26.72mm; the focal length of the fourth lens G4 is f4=60.39 mm.

They satisfy the following relation:

0.1<(|fA/fB|＝0.24)<0.35；0.5<(|f1/fA|＝0.98)<1.5；

0.6<(|f2/fA|＝1.02)<1.6；0.2<(|f3/fA|＝0.44)<0.7；

0.6<(|f4/fA|＝0.98)<1.6。

specifically, fig. 3 is an on-axis chromatic aberration diagram of the telecentric lens optical system according to the present embodiment, in which the horizontal axis represents the offset, the vertical axis represents the normalized pupil, and the offset between wavelengths near the 0.76 pupil is small, so as to achieve chromatic aberration elimination.

The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An achromatic object-side telecentric lens is characterized by comprising a front group lens (A), a diaphragm (S) and a rear group lens (B) which are sequentially arranged from an object side to an image side;

the front group lens (A) is composed of a first lens (G1) with positive focal power and a biconvex structure, a second lens (G2) with positive focal power and a biconcave structure, a third lens (G3) with negative focal power and a biconcave structure and a fourth lens (G4) with positive focal power; the second lens (G2), the third lens (G3) and the fourth lens (G4) constitute a first cemented lens (U1);

the rear group lens (B) is composed of a fifth lens (G5) with negative focal power and a biconcave structure and a sixth lens (G6) with positive focal power and a biconvex or plano-convex structure; and the fifth lens (G5) and the sixth lens (G6) constitute a second cemented lens (U2);

the front group lens (a) has a combined focal length fA, the rear group lens (B) has a combined focal length fB, and they satisfy the following relation: 0.1< |fA/fB| <0.35.

2. The achromatic telecentric lens according to claim 1, wherein the focal length of the first lens (G1) is f1, and the combined focal length fA with the front group lens (a) satisfies the following relation: 0.5< |f1/fA| <1.5.

3. The achromatic telecentric lens according to claim 2, wherein the first lens (G1) is made of a high refractive index glass material.

4. The achromatic telecentric lens according to claim 1, wherein the focal length of the second lens (G2) is f2, and the combined focal length fA with the front group lens (a) satisfies the following relation: 0.6< |f2/fA| <1.6.

5. The achromatic telecentric lens according to claim 4, characterized in that the refractive index of the second lens (G2) is n2, the abbe number is v2, which satisfies the relation: 1.45< n2<1.55;70< v2<85.

6. The achromatic telecentric lens according to claim 1, wherein the focal length of the third lens (G3) is f3, and the combined focal length fA with the front group lens (a) satisfies the following relation: 0.2< |f3/fA| <0.7.

7. The achromatic telecentric lens according to claim 1, wherein the fourth lens (G4) has a focal length f4 and the combined focal length fA with the front group lens (a) satisfies the following relation: 0.6< |f4/fA| <1.6.

8. The achromatic telecentric lens according to claim 7, wherein the fourth lens (G4) is made of low dispersion glass material.

9. The achromatic object-side telecentric lens according to claim 1, further comprising a prism (P) arranged between the fourth lens (G4) and the stop (S).