CN110441311B

Movatterモバイル変換

Info

Publication number: CN110441311B
Application number: CN201910661174.5A
Authority: CN
Inventors: 唐顺兴; 朱宝强; 杨晓伟; 杨琳; 姜秀青; 郭亚晶; 杨朋千
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2019-07-22
Filing date: 2019-07-22
Publication date: 2021-10-08
Anticipated expiration: 2039-07-22
Also published as: CN110441311A

Abstract

A multi-axis and multi-focus lens for multi-object plane imaging comprises an object plane, an optical axis steering structure, an imaging optical system, a compensation flat plate and an image plane. The invention can realize the simultaneous imaging of the sample surfaces which are not in the same plane on one image plane through the combination of all parts of the lens. Compared with the traditional multi-camera-based machine vision system, the system has the advantages of more compact structure, capability of reducing the number of cameras and lenses and reducing the economic expenditure of the lenses and the expenditure of data processing resources.

Description

Multi-axis and multi-focus lens for multi-object plane imaging

Technical Field

The invention relates to a multi-axis multi-focus lens, in particular to a multi-axis multi-focus lens for imaging of multiple object planes.

Background

When the appearance of a product is detected to be poor in the existing production and processing, human eye detection is adopted, and human misjudgment is caused by human subjective judgment, visual fatigue and other factors. With the development of machine vision technology, the automatic detection of machine vision is gradually realized for workpieces which cannot adopt machine vision in the past. Conventionally, there is a technique of detecting defects on a sample surface from a captured image obtained by capturing an image with a camera (see patent document 1: application No. CN03102169.7, inspection method and inspection system for an object surface), and many similar methods are used. However, only one target surface can be detected at a time, and in order to detect a plurality of target surfaces which are not in the same plane, cameras and lenses which are the same as the target surfaces to be detected in number are required to be equipped.

When the size of a workpiece is measured in the existing production and processing, the traditional method adopts a direct measurement method, and the method has the advantages of direct measurement, no need of additional calibration and low speed. The dimension measurement method based on image analysis is widely applied along with the development of machine vision technology. Conventionally, a technique for measuring a sample surface from a captured image captured by a camera is known (see patent document 2: application No. CN02107961.7, optical metrology device). As previously mentioned, similar methods typically measure for only one target surface.

Disclosure of Invention

The invention aims to provide a multi-axis multi-focus lens for imaging multiple object planes, which can realize simultaneous imaging of sample surfaces which are not in the same plane on one image plane through the combination of all parts of the lens. Compared with the traditional multi-camera-based visual system, the lens has the advantages of more compact structure, capability of reducing the number of cameras and lenses and reducing the economic expenditure of the lens and the expenditure of data processing resources.

To achieve the above object, the technical solution of the present invention is as follows:

a multi-axis and multi-focus lens for imaging of multiple object planes is characterized by comprising an object plane, an optical axis steering structure, an imaging optical system, a compensation flat plate and an image plane, wherein light emitted by the object plane sequentially passes through an optical system consisting of the optical axis steering structure, the imaging optical system and the compensation flat plate to reach the image plane.

The object plane at least comprises two sub-object planes, at least two sub-object planes are not in the same plane, and each sub-object plane is an optical conjugate plane of the image plane passing through the optical system.

The optical axis turning structure can be, but is not limited to, composed of a reflector and a prism, and beam deflection introduced by the optical axis turning structure needs to ensure that imaging beams of all sub-object planes of the object plane enter the imaging optical system after passing through the optical axis turning structure.

The imaging optical system images a limited far object plane on a limited far image plane, the object space working distance needs to be larger than the minimum distance required by the arrangement of the optical axis turning structures, the distance from the image plane to the image space end face of the imaging optical system needs to be larger than the minimum distance required by the arrangement of the compensation plates, and the pupil of the imaging optical system ensures that light rays for imaging each object plane pass through the corresponding optical axis turning structure and the corresponding compensation plate and do not interfere with each other.

The thickness d of the compensation plate is determined by the refractive index n of the compensation plate and the image distance difference delta needing compensation, and the relation d is n/(n-1) delta.

The image surface is divided into a plurality of subregions, each subregion corresponds to one sub-object surface of the object surface, and the subregions are not overlapped with each other.

Experiments show that the multi-axis multi-focus lens for multi-object plane imaging can realize simultaneous imaging of sample surfaces which are not in the same plane on one image plane through the combination of all parts of the lens. Compared with the traditional multi-camera-based machine vision system, the system has the advantages of more compact structure, capability of reducing the number of cameras and lenses and reducing the economic expenditure of the lenses and the expenditure of data processing resources.

Drawings

FIG. 1 is a schematic view of a multi-axis multi-focus lens for multi-object plane imaging according to the present invention

FIG. 2 is a schematic structural diagram of a multi-axis multi-focus lens used for multi-object plane imaging according to embodiment 1 of the present invention

FIG. 3 is a schematic structural diagram of a multi-axis multi-focus lens of the embodiment 2 for multi-object plane imaging according to the present invention

FIG. 4 is a schematic structural diagram of a multi-axis multi-focus lens in accordance with an embodiment 3 of the present invention

Detailed Description

The present invention will be further described with reference to the following examples and drawings, but the scope of the present invention should not be limited thereto.

Example 1

Fig. 2 is a schematic structural diagram of a multi-axis multi-focus lens in embodiment 1 for multi-object plane imaging according to the present invention. The sample (10) to be observed is provided with N step surfaces, namely afirst step surface 101, asecond step surface 102, a second step surface … … and anNth step surface 10N. The operation principle will be described by taking this as an example.

In this embodiment, the optical imaging system is a double telecentric structure, and the focal length f of theobject lens 301₁Focal length f ofimage side lens 302₂The distance between the two lenses is f₁+f₂. Thefirst step surface 101 is spaced from theobject side lens 301 by a distance u₁Passes through theoptical imaging system 30 and is imaged on asub-region 501 of theimage plane 50 with an image distance v₁. According to the ideal lens object image relationship, v₁And u₁The following relationships exist:

if no compensating optical element is added to the optical path, theNth step surface 10N is spaced from theobject side lens 301 by a distance u_NAfter passing through theoptical imaging system 30, the image is formed on theNth sub-image surface 60N with an image distance v_N. According to the ideal lens object image relationship, v_NAnd_Nthe following relationships exist:

to ensure image distance v₁And v_NAre all larger than zero and need to satisfy the object distance

The distance between theimage plane 50 and the Nthsub-image plane 60N is

From the above formula, when thefirst object plane 101 and theNth object plane 10N are not coincident, i.e., (u)_N-u₁) When the distance is not zero, the corresponding image planes of the first object plane and the second object plane do not coincide after passing through theoptical imaging system 30, and when the distance is larger than the focal depth of the optical imaging system, the first object plane and the Nth object plane cannot be imaged simultaneously by using the same camera.

Adding acompensation plate 40N with the thickness d to the imaging optical path of the Nth object plane_NThe refractive index is n, the converged light beam entering the flat optical system is refracted and emitted, and the emergent convergence point is moved backward by a distance delta from the convergence point_N＝d_N(n-1)/n. Image plane shift amount delta caused by insertedcompensation plate 40N_NThe distance delta between the image surfaces corresponding to the first object surface and the Nth object surface_NWhen they are equal, namely:

the first object plane and the Nth object plane can be ensured to form clear images on theimage plane 50. That is, the lens has a multi-focus function, and it can be considered that the lens realizes a function of simultaneously operating a plurality of working distances.

And a camera is arranged on the image surface, so that the shapes of the surfaces of a plurality of steps of the multi-step sample, including the size, the defects and the like, can be recorded simultaneously.

Example 2

Fig. 3 is a schematic structural diagram of a multi-axis multi-focus lens in embodiment 2 for multi-object plane imaging. Thesample 10 to be observed has N surfaces which respectively form a certain angle, namely afirst surface 101, asecond surface 102, … … and anNth surface 10N. The working principle is explained by taking this as an example.

In this embodiment, the optical imaging system is a double telecentric structure, and the focal length of the object lens 301f₁Focal length f ofimage side lens 302₂The distance between the two lenses is f₁+f₂. Thefirst surface 101 is at a distance u from the object lens₁The image passes through the optical imaging system and is imaged on asub-area 501 of theimage surface 50, and the image distance is v₁. According to the ideal lens object image relationship, v₁And u₁The following relationships exist:

to ensure image distance v₁Greater than zero, object distance needs to be satisfied

TheNth surface 10N travels a distance u_N1Then reflected by thenth mirror 20N, and the propagation direction of the light beam rotates by a certain angle, which is consistent with the propagation direction of the imaging light beam on thefirst surface 101; retransmission distance u_N2And then to theobject lens 301. Object distance of imaging of Nth surface is u_N＝u_N1+u_N2。

According to the Gaussian lens equation, if no compensation optical element is added in the optical path and theNth surface 10N needs to be clearly imaged, the distance u between theNth surface 10N and theobject lens 301 needs to be ensured_N＝u₁Can ensure that the image is imaged at an image distance v after passing through theoptical imaging system 30_N＝v₁I.e., imaged at theimage plane 50.

Thus, clear images of the first object plane, the second object plane … … and the nth object plane are obtained through one image plane, wherein the N object planes have the same object distance but different postures. The lens has a multi-axis function, and can realize simultaneous imaging of surfaces with a certain included angle under the condition of one working distance, so that simultaneous imaging of the surfaces in a plurality of spatial directions is realized.

By placing the camera on the image plane, the shapes of the surfaces in a plurality of spatial directions, including the sizes, defects and the like, can be recorded simultaneously.

Example 3

Fig. 4 is a schematic structural diagram of a multi-axis multi-focus lens in embodiment 3 for multi-object plane imaging according to the present invention. The basic principle has been explained in embodiment 1 and embodiment 2, where embodiment 1 is an implementation of a multi-focus lens, embodiment 2 is an implementation of a multi-axis lens, and embodiment 3 is an implementation of multi-axis multi-focus.

Thesample 10 to be observed has a plurality of surfaces which form a certain angle respectively, and the object distances from the surfaces to the lens are different, and the embodiment 3 of the multi-axis multi-focus lens for multi-object plane imaging can realize simultaneous imaging of a plurality of surfaces in different directions and with different object distances. The working principle is illustrated by taking the example as follows:

in this embodiment, the optical imaging system is an object telecentric structure, and according to the principle described in embodiment 2, different lightbeam steering systems 20 are disposed on different surfaces, so that the central light beam is in the same direction as the optical axis of theoptical system 30 when the imaging light beams on the surfaces reach the imaging system. Since the optical paths of the surfaces to theoptical system 30 are different, that is, the object distances are different, according to the principle described in embodiment 1, thecompensation plate 40 is disposed on the image side of the imaging beam to perform optical path compensation, so that all the target surfaces are imaged on thesame image plane 50.

By arranging the camera on the image surface, the shapes of the surfaces with different object distances and a plurality of spatial directions can be recorded simultaneously, wherein the shapes comprise sizes, defects and the like.

Experiments show that the invention can realize the simultaneous imaging of the sample surfaces which are not in the same plane on one image plane through the combination of all parts of the lens. Compared with the traditional multi-camera-based machine vision system, the system has the advantages of more compact structure, capability of reducing the number of cameras and lenses and reducing the economic expenditure of the lenses and the expenditure of data processing resources.

Claims

Translated fromChinese

1.一种用于多物面成像的多轴多焦镜头，其特征在于包括物面(10)、光轴转向结构(20)、成像光学系统(30)、补偿平板(40)和像面(50),所述的物面(10)发出的光依次经由所述光轴转向结构(20)、成像光学系统(30)和补偿平板(40)组成的光学系统，到达像面(50)；1. A multi-axis multifocal lens for multi-object plane imaging, characterized in that it comprises an object plane (10), an optical axis turning structure (20), an imaging optical system (30), a compensation plate (40) and an image plane (50), the light emitted from the object plane (10) reaches the image plane (50) through the optical system composed of the optical axis turning structure (20), the imaging optical system (30) and the compensation flat plate (40) in turn. ;

所述的物面(10)至少包括两个子物面，且至少有两个子物面不在同一个平面内,每个子物面均是所述像面(50)经过该光学系统的光学共轭面；The object plane (10) includes at least two sub-object planes, and at least two sub-object planes are not in the same plane, and each sub-object plane is an optical conjugate plane of the image plane (50) passing through the optical system ;

所述的成像光学系统(30)将有限远的物面(10)成像在有限远的像面(50)上，且物方工作距离需要大于排布所述光轴转向结构所需的最小距离，所述的像面(50)至所述成像光学系统(30)像方端面的距离需要大于排布所述的补偿板(40)所需的最小距离，该成像光学系统(30)的光瞳，保证用于各物面成像的光线均通过各自对应的所述的光轴转折结构(20)和所述的补偿平板(40)，互不干扰。The imaging optical system (30) images the object plane (10) at a finite distance on the image plane (50) at a finite distance, and the object-side working distance needs to be greater than the minimum distance required for arranging the optical axis turning structure , the distance from the image plane (50) to the image-side end face of the imaging optical system (30) needs to be greater than the minimum distance required for arranging the compensation plate (40). The pupil is used to ensure that the light used for imaging of each object plane passes through the corresponding optical axis turning structure (20) and the compensation plate (40), and does not interfere with each other.

2.根据权利要求1所述用于多物面成像的多轴多焦镜头，其特征在于所述的光轴转向结构(20)由反射镜和棱镜组成，该光轴转向结构(20)引入的光束偏折需保证物面(10)的所有子物面的成像光束经过光轴转向结构(20)后进入所述的成像光学系统(30)。2. The multi-axis multifocal lens for multi-object plane imaging according to claim 1, wherein the optical axis turning structure (20) is composed of a reflector and a prism, and the optical axis turning structure (20) introduces It is necessary to ensure that the imaging beams of all sub-object planes of the object plane (10) enter the imaging optical system (30) after passing through the optical axis turning structure (20).

3.根据权利要求1所述的用于多物面成像的多轴多焦镜头，其特征在于所述的补偿平板(40)的厚度d由补偿平板的折射率n和需要补偿的像距差值Δ决定，且满足关系d＝n/(n-1)Δ。3. The multi-axis multifocal lens for multi-object plane imaging according to claim 1, wherein the thickness d of the compensation plate (40) is determined by the refractive index n of the compensation plate and the aberration difference that needs to be compensated The value Δ is determined and satisfies the relation d=n/(n-1)Δ.

4.根据权利要求1至3任一项所述的用于多物面成像的多轴多焦镜头，其特征在于所述的像面(50)分为若干子区域，每个子区域对应所述的物面(10)的一个子物面，各子区域互不重合。4. The multi-axis multifocal lens for multi-object plane imaging according to any one of claims 1 to 3, wherein the image plane (50) is divided into several sub-areas, and each sub-area corresponds to the A sub-object plane of the object plane (10) of , and the sub-regions do not overlap with each other.