阅读说明：本技术 基于光栅泰伯像的物体表面曲率检测系统及方法 (Object surface curvature detection system and method based on grating Talbot image ) 是由 何勇 薛鹏永 徐海飞 侯陶冉 李建欣 郭仁慧 马骏 沈华 朱日宏 于 2019-10-10 设计创作，主要内容包括：本发明公开了一种基于光栅泰伯像的物体表面曲率检测系统及方法,该方法使用准直光垂直入射一朗奇光栅,透射的光线经过分束镜之后在被测物体表面呈现光栅清晰的泰伯像,反射光能在特定位置呈现含有被测物体表面曲率信息的光栅泰伯像,使用ccd采集该泰伯像,根据采集到的泰伯像计算被测物体表面曲率。本发明具有装置简单、成本低廉、抗干扰能力强、应用范围广等优点。(The invention discloses an object surface curvature detection system and method based on a grating Talbot image. The invention has the advantages of simple device, low cost, strong anti-interference capability, wide application range and the like.)

1. An object surface curvature detection system based on a grating Talbot image is characterized by comprising a laser (1), a collimation beam expander (2), a grating (3), a beam splitter (4), a ccd (6) and a curvature calculating module, the laser (1) is connected with the collimation and beam expansion lens (2) through an optical fiber, the grating (3) is arranged right opposite to the collimation and beam expansion lens (2), the beam splitter (4) is set to reflect the light transmitted by the grating (3) on the surface of the object to be measured (5) through the beam splitter (4) to form a sharp Talbot image of the grating, the ccd (6) is set to that the light beam reflected by the surface of the measured object (5) presents a Talbot image with surface curvature information on the ccd (6) through the beam splitter (4), the curvature calculating module is used for determining the surface curvature of the measured object according to the acquired Talbot image, the period of the Lambert grating and the optical path from the surface of the measured object to the ccd.

2. The system for object surface curvature detection based on grating Talbot images as claimed in claim 1, characterized in that the grating (3) is a Lambertian grating.

3. The system of claim 1, wherein the optical path length z from the grating to the measured object surface is₁Set to an integer number of Talbot distances, i.e.

4. The system of claim 1, wherein the z optical path from the measured object surface to ccd (6) is the length of the object surface to the ccd (6)₂At integer multiples of the generalized Talbot distance, i.e.

5. The system for detecting the curvature of the surface of the object based on the grating Talbot image as claimed in claim 1, wherein the curvature calculating module determines the surface curvature of the object to be measured according to the acquired Talbot image, the period of the Lambert grating and the optical path from the surface of the object to the ccd by the formula:

wherein p' is the period of grating Talbot image at ccd, z₁An optical path from the grating to the surface of the object to be measured; z is a radical of₂The optical path from the surface of the object to be measured to the ccd, and C is the curvature.

6. The system for detecting the curvature of the surface of the object based on the grating Talbot image as claimed in claim 5, wherein the period of the grating Talbot image is specifically:

p′＝1/v

in the formula, v is the peak frequency of the Talbot image.

7. The method based on the system of any one of claims 1 to 7, characterized by comprising the following specific steps:

step 1, leading out laser emitted by a laser (1) through an optical fiber, obtaining parallel light after passing through a collimation beam expander (2), and vertically emitting the parallel light onto a grating (3), so that transmitted light is in a Talbot image with clear grating at the surface (5) of a measured object through a beam splitter (4);

step 2, adjusting the position of the ccd (6) to enable the light beam reflected by the surface of the object to present a clear Talbot image on the ccd (6);

step 3, according to the Talbot image collected by the ccd (6), solving the peak frequency v of the Talbot image by using a frequency domain sub-pixel iteration method, and determining the period p' of the grating Talbot image at the ccd as 1/v;

and 4, solving the surface curvature of the measured object according to the period of the Talbot image, the period of the known Lambert grating and the optical path from the surface of the measured object to the ccd.

8. The method for detecting the curvature of the surface of the object based on the Talbot image of the grating as claimed in claim 7, wherein the specific formula for obtaining the curvature of the surface of the object to be measured according to the period of the Talbot image, the period of the known Lambert grating and the optical path from the surface of the object to the ccd is as follows:

in the formula, p' is the period of the grating Talbot image, wherein p is the period of the Lambert grating; z is a radical of₂An optical path from the surface of the object to be measured to the ccd; and R is the surface curvature radius of the object to be measured.

Technical Field

The invention belongs to the field of optical precision testing, and particularly relates to a system and a method for detecting the surface curvature of an object based on a grating Talbot image.

Background

Spherical mirrors are increasingly widely applied in modern optical systems, the curvature radius of the mirror is one of important parameters for determining the optical characteristics of the mirror, and the processing quality of an optical element to be measured can be judged by measuring the curvature radius of the optical element so as to further correct the optical element to achieve higher precision. Therefore, the accurate measurement technology of the curvature radius has important research significance and use value.

The mirror curvature radius measuring method can be classified into two major types, contact type and non-contact type. The contact measurement mainly comprises a spherical template method, a Newton ring method, a sphere diameter instrument method, a three-coordinate measurement method and a laser tracker method. The non-contact measurement mainly comprises a knife edge shadow method, an auto-collimation microscope method, a laser interferometry method, a laser differential confocal method and the like. The contact detection technology is mature, has good flexibility and large dynamic range, is suitable for different types of mirror surfaces, and has high precision. However, the contact detection technology needs point-by-point detection, and the measurement speed is slow; the method is influenced by the diameter of a measuring probe, has limited sampling density, is difficult to obtain high-frequency errors of the measured surface type, and is easy to scratch the surface of the measured lens; the equipment is expensive in manufacturing cost and high in maintenance cost. The non-contact measurement has no damage to the surface of the measured object, but generally has higher requirements on the measurement environment, and larger errors can be generated by slight vibration; and high-precision measuring equipment is complex to operate and high in manufacturing cost.

Disclosure of Invention

The invention aims to provide an object surface curvature detection system based on a grating Talbot image.

The technical solution for realizing the purpose of the invention is as follows: the utility model provides an object surface camber detecting system based on grating Talbot is like, includes laser instrument, collimation beam expander mirror, grating, beam splitter, ccd and camber and solves the module, the laser instrument passes through optic fibre and is connected with the collimation beam expander mirror, the grating is just setting up the collimation beam expander mirror, the beam splitter is set up to personally submit the clear Talbot like of grating at the measured object surface through beam splitter reflection for the light that passes through the grating transmission, ccd is set up to the beam of measured object surface reflection and presents the Talbot like that has surface camber information through the beam splitter on ccd, the camber is solved the module and is used for confirming measured object surface camber according to the Talbot like of gathering, the cycle of Lambert grating, measured object surface to ccd's optical path.

Preferably, the grating is a lambertian grating.

Preferably, the optical path z from the grating to the surface of the measured object₁Set to an integer number of Talbot distances, i.e.And finely adjusting the object to be measured before measurement to enable the surface of the object to present a clear grating image, wherein lambda is the working wavelength, p is the grating period, and n is a positive integer.

Preferably, the optical path z from the surface of the object to be measured to the ccd₂At integer multiples of the generalized Talbot distance, i.e.

And (3) finely adjusting the position of the ccd during measurement so that the ccd can acquire a clear grating image, wherein R is the curvature radius of the surface of the object to be measured, and m is a positive integer.

Preferably, the formula for determining the surface curvature of the measured object by the curvature calculating module according to the acquired Talbot image, the period of the Lambert grating and the optical path from the surface of the measured object to the ccd is as follows:

wherein p' is the period of grating Talbot image at ccd, z₁An optical path from the grating to the surface of the object to be measured; z is a radical of₂The optical path from the surface of the object to be measured to the ccd, and C is the curvature.

Preferably, the period of the grating talbot image is specifically:

p′＝1/v

in the formula, v is the peak frequency of the Talbot image.

The invention also provides an object surface curvature detection method based on the grating Talbot image, which comprises the following specific steps:

the method comprises the following specific steps:

step 1, leading out laser emitted by a laser through an optical fiber, obtaining parallel light after the laser passes through a collimation beam expander, and vertically emitting the parallel light onto a grating to enable transmitted light to form a Talbot image with clear grating on the surface of a measured object through a beam splitter;

step 2, adjusting the position of the ccd, so that the light beam reflected by the surface of the object presents a clear Talbot image on the ccd;

step 3, according to the Talbot image collected by the ccd, solving the peak frequency v of the Talbot image by using a frequency domain sub-pixel iteration method, and determining the period p' of the grating Talbot image at the ccd as 1/v;

and 4, solving the surface curvature of the measured object according to the period of the Talbot image, the period of the known Lambert grating and the optical path from the surface of the measured object to the ccd.

Compared with the prior art, the invention has the following remarkable advantages: 1) the common optical path design of the invention has strong anti-environmental interference capability; 2) the invention uses a single grating, the device is simple, the error superposition caused by a complex light path is avoided, and the cost is low; 3) the invention can match different curvature radiuses by adjusting the optical path from the ccd to the surface of the object to be measured, and has wide application range.

The present invention is described in further detail below with reference to the attached drawings.

Drawings

FIG. 1 is a schematic diagram of an object surface curvature detection system based on a grating Talbot image.

Detailed Description

The utility model provides an object surface curvature detecting system based on grating Talbot is like, includes that laser 1, collimation beam expander mirror 2, grating 3, beam splitter 4, ccd6 and camber resolve the module, laser 1 passes through optic fibre and is connected with collimation beam expander mirror 2, grating 3 is just setting up to collimation beam expander mirror 2, beam splitter 4 is set up to be the sharp Talbot of grating at measured object 5 surface through beam splitter 4 reflection, ccd6 is set up to the beam of measured object 5 surface reflection and presents the Talbot like that has surface curvature information through beam splitter 4 on ccd6, the camber is resolved the module and is used for confirming measured object surface camber according to the Talbot like that gathers, the cycle of lambertian grating, measured object surface to the optical path of ccd.

Laser emitted by a laser 1 generates a beam of parallel light through a collimation beam expander 2, the parallel light vertically enters a grating 3, a Talbot image of the grating is formed on the surface of a measured object 5 through a beam splitter 4, the Talbot image is reflected by the surface of the object and presents an amplified grating image on ccd6, the peak frequency v of the Talbot image is obtained according to the Talbot image collected by ccd6 by using a frequency domain subpixel iteration method, then the period of the grating Talbot image at ccd is obtained, and the surface curvature of the measured object is obtained according to the obtained period of the Talbot image, the known period of the Lambert grating and the optical path from the surface of the measured object to ccd.

In a further embodiment, the grating 3 is a lambertian grating.

In a further embodiment, the optical path z from the grating to the surface of the object to be measured₁Set to an integer number of Talbot distances, i.e.

And finely adjusting the object to be measured before measurement to enable the surface of the object to present a clear grating image, wherein lambda is the working wavelength, p is the grating period, and n is a positive integer.

In a further embodiment, the optical path z from the surface of the object to be measured to the ccd6₂At integer multiples of the generalized Talbot distance, i.e.

During measurement, the position of the ccd6 is finely adjusted, so that the ccd6 can acquire a clear grating image, wherein R is the curvature radius of the surface of the object to be measured, and m is a positive integer.

In a further embodiment, the formula for determining the surface curvature of the measured object by the curvature calculating module according to the acquired Talbot image, the period of the Lambert grating and the optical path from the surface of the measured object to the ccd is as follows:

wherein p' is the period of grating Talbot image at ccd, z₁An optical path from the grating to the surface of the object to be measured; z is a radical of₂The optical path from the surface of the object to be measured to the ccd, and C is the curvature.

In a further embodiment, the period of the grating talbot image is specifically:

p′＝1/v

in the formula, v is the peak frequency of the Talbot image.

An object surface curvature detection method based on a grating Talbot image comprises the following specific steps:

step 1, leading out laser emitted by a laser 1 through an optical fiber, obtaining parallel light after the laser passes through a collimation beam expander 2, and vertically emitting the parallel light onto a grating 3 to enable transmitted light to form a Talbot image with clear grating on the surface 5 of a measured object through a beam splitter 4;

step 2, adjusting the position of the ccd6, so that the light beam reflected by the surface of the object presents a clear Talbot image on the ccd 6;

step 3, according to the Talbot image collected by the ccd6, solving the peak frequency v of the Talbot image by using a frequency domain sub-pixel iteration method, and determining the period p' of the grating Talbot image at the ccd as 1/v;

step 4, solving the surface curvature of the measured object according to the period of the Talbot image, the period of the known Lambert grating and the optical path from the surface of the measured object to the ccd, wherein the specific formula is as follows:

in the formula, p' is the period of the grating Talbot image, wherein p is the period of the Lambert grating; z is a radical of₂An optical path from the surface of the object to be measured to the ccd; and R is the surface curvature radius of the object to be measured.