CN214502376U

CN214502376U - Wide-range spectrum confocal displacement detection device

Info

Publication number: CN214502376U
Application number: CN202121094433.XU
Authority: CN
Inventors: 张浩然; 李劲松; 苏衍峰; 王洵园
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2021-05-21
Filing date: 2021-05-21
Publication date: 2021-10-26
Anticipated expiration: 2031-05-21

Abstract

The utility model provides a confocal displacement detection device of spectrum of wide range, including white light source, slit, collimating lens, beam splitter prism, fresnel lens, testee, focusing lens, spectrum appearance, wherein: a white light source emits a beam of white light, the white light enters a beam splitter prism through a slit and a collimating lens, the white light is dispersed along the direction of an optical axis after passing through a Fresnel lens, light with different wavelengths is converged at different positions of the optical axis, the light beam focused on the surface of a measured object is reflected and returns in the original path, and the reflected light beam passes through the beam splitter prism and a focusing lens and enters a spectrometer behind the slit. The spectrograph receives two specific wavelengths selected by the confocal characteristic, and the specific wavelengths are used for solving a corresponding focal length difference value, namely the displacement distance of the object to be measured. The device focuses light beams with different wavelengths on different positions of an optical axis by utilizing the Fresnel lens, so that axial dispersion is generated, the limit distance between focuses corresponding to the light source wavelength is greatly increased, and the measuring range of the displacement detection device is expanded by two orders of magnitude.

Description

Wide-range spectrum confocal displacement detection device

Technical Field

The utility model belongs to optics non-contact precision displacement measurement field, in particular to confocal displacement detection device of spectrum of wide range.

Background

The spectrum confocal displacement detection is a precise displacement measuring device and has the following principle: a beam of polychromatic light (white) is emitted by a light source, and is focused on the surface of an object to be measured through a lens group, monochromatic light with different wavelengths is formed in a measuring range, and a focus of each wavelength corresponds to a distance value. The measuring light is emitted to the surface of an object and is reflected back, only monochromatic light meeting confocal conditions can be sensed by the spectrometer through the slit, and the displacement distance of the measured object is obtained by calculating the focus difference value corresponding to the wavelength of the detected light wave. The spectral confocal displacement measuring device is widely used in precise non-contact measurement, and is one of the few feasible schemes in the submicron field and the field of the diversification of the surface of the measured object.

In the prior art, a spectrum confocal displacement sensor is invented by Liubin, Wei Jia Tong et al of the university of North and Central, the patent name is a spectrum confocal displacement sensor, the granted patent number is CN 107084665A, and the granted publication date is 8 months and 22 days in 2017. The utility model discloses a install the polarizer group additional before the battery of lens for the light beam has the polarization, recycles the synchronous measurement that same platform equipment realized the multiple spot displacement of detection analysis completion of analyzer. But the measuring range of the utility model is only about 2 mm. In addition, people of the university of fertilizer combination industry, such as Zhang, Guilian beam and the like, invented a spectrum confocal displacement sensor based on chirped fiber grating, with the patent authorization number of CN 110567379B and the authorization date of No. 3/30 in 2021, the invention utilizes chirped fiber grating to realize dispersion, replaces a dispersion lens with a complex structure, and realizes the miniaturization of a precision measurement system, but the measuring range of the invention is also reduced to 50 micrometers, so that the measuring range of the spectrum confocal displacement sensor in the prior art is limited, and the application range of the device is limited.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model aims at: and the displacement precision detection with a large range is realized.

In order to achieve the above object, the technical solution of the present invention is specifically realized as follows:

the utility model provides a confocal displacement detection device of spectrum of wide range, include: the device comprises a white light source, a slit, a collimating lens, a beam splitting prism, a Fresnel lens, a measured object, a focusing lens and a spectrometer. The white light source and the measured object are coaxial, the slit, the collimating lens, the beam splitter prism and the Fresnel lens are sequentially arranged between the white light source and the measured object, and the focusing lens, the slit and the spectrometer are sequentially arranged on the right side of the beam splitter prism.

The utility model provides a confocal displacement detection device of spectrum of wide range, its work flow is as follows:

the white light source emits a beam of white light, parallel light is emitted after the white light passes through the slit and the collimating lens, after the parallel light enters the light splitting prism, part of light beams enter the Fresnel lens and are dispersed in the direction of the optical axis after passing through the Fresnel lens, light with different wavelengths is converged at different positions of the optical axis, and when the light reaches the surface of a measured object on the main optical axis, the light is reflected and returns in the original path. The wavelength of the reflected light is different because the position of the measured object is changed. The two light waves pass through the beam splitter prism and the focusing lens and enter the spectrometer after the slit. The spectrometer can measure the wavelength peak values of the two light waves to determine the displacement distance between the measured surfaces.

Fresnel lens lie in beam splitting prism and measured object between, this Fresnel lens's main focal length can independently be formulated according to the demand.

Since the technical scheme is adopted, the utility model discloses the beneficial effect who gains is:

the device focuses light beams with different wavelengths on different positions of an optical axis by utilizing the Fresnel lens, so that axial dispersion is generated, the limit distance between focuses corresponding to the wavelengths of the light sources is greatly increased, and the measuring range of the displacement detection device is expanded by two orders of magnitude; meanwhile, compared with a dispersion lens of a common lens group, the Fresnel lens greatly reduces the cost.

Drawings

The drawings that constitute the present invention are intended to provide a further understanding of the invention, and the illustrative embodiments and descriptions thereof are intended to explain the invention without constituting an undue limitation on the invention.

FIG. 1 is a schematic structural view of the present invention;

description of reference numerals: 1-a white light source; 2-a slit; 3-a collimating lens; 4-a beam splitting prism; 5-a Fresnel lens; 6-the object to be tested; 7-a focusing lens; 8-a slit; 9-spectrometer.

Detailed Description

It should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict. Embodiments of the present invention will be described with reference to the accompanying drawings, which are simplified and schematic in nature;

the utility model provides a wide-range spectrum confocal displacement detection device, as shown in figure 1, which is a structural schematic diagram of a wide-range spectrum confocal displacement detection device, wherein the device comprises a white light source (1); a slit (2); a collimating lens (3); a beam splitter prism (4); a Fresnel lens (5); an object to be measured (6); a focusing lens (7); a slit (8); a spectrometer (9).

In the embodiment, the primary focal length of the Fresnel lens is f₀600mm, corresponding to a wavelength λ₀＝600nm。

In the embodiment, the spectrometer is FX2000, the detection range of the spectrometer is 200nm-1100nm, the wavelength range of visible light is covered, the highest resolution of the spectrometer can reach 0.24nm, the detection range of two orders of magnitude is expanded in a matching mode, and the application range of the device is greatly expanded.

When the device works, a white light beam is emitted from a white light source (1), parallel beams are formed after passing through a slit (2) and a collimating lens (3), then partial beams enter a Fresnel lens (5) after passing through a beam splitting prism (4), and light waves with different wavelengths are converged at different positions on an optical axis after passing through the Fresnel lens (5), so that axial dispersion is generated. The light beam focused on the surface of the measured object is reflected and returns in the original path. When the surface displacement distance of the measured object (6) is within the range of the device, the light beams reflected by the measured object twice pass through the Fresnel lens (5), the beam splitter prism (4) and the focusing lens (7) on the right side and enter the spectrometer (9) behind the slit (8), the spectrometer analyzes the specific wavelength selected by the confocal characteristic to obtain the corresponding peak wavelength, and the displacement distance of the measured object is solved according to the corresponding peak wavelength.

In the embodiment, when the wavelength of the white light source is 380nm-760nm, f is satisfied according to the formula of the Fresnel lens₀×λ₀Substituting the main focal length f in the embodiment₀And corresponding wavelength lambda₀The distance between the corresponding focal points of the long wavelength and the short wavelength is 478mm, which is the range of the large-range spectrum confocal displacement detection device in this embodiment. Compared with the common spectral confocal displacement detection device with the measuring range of 1mm, the measuring range in the embodiment is 478 times that of the common measuring range.

For a better understanding of the utility model device, it is right to the utility model discloses theoretical part supplements the explanation:

in an optical system, the structure of the fresnel lens is based on a half-zone plate, and can be regarded as a multi-step phase-shaped structure made of a plurality of concentric rings. Each concentric ring converges the light wave onto the optical axis, and the fresnel lens satisfies:

f＝r²/mλ

the wavelength information and the focal length value are converted by utilizing the axial chromatic aberration, and the method is a key for realizing the spectrum confocal measurement system. The measuring range of the system is a distance value L between focus points between long wavelength and short wavelength of a white light source, and the formula is as follows:

L＝f(λ_min)-f(λ_max)

the primary focal length of the Fresnel lens can be customized autonomously if it is f₀Corresponding to a wavelength λ₀Then the focal lengths of the other incident wavelengths and the focal length of the center wavelength satisfy:

by combining the above formulas, when the light beam passes through the fresnel lens, the wavelength is inversely proportional to the focal length, and by determining the main focal length and the corresponding wavelength thereof, the focal length difference corresponding to other wavelengths can be increased, i.e., the measuring range of the detection device is also greatly increased. The range of the detection device can be expressed as:

in addition, the resolution of the spectrometer is also a factor influencing the measurement accuracy of the whole spectrum confocal system, and needs to be selected according to actual requirements. Since the light source of the present system is a white light source, the choice of spectrometer must encompass the wavelength range of the white light source.

Claims

1. The wide-range spectrum confocal displacement detection device comprises a white light source, a slit, a collimating lens, a beam splitter prism, a Fresnel lens, a measured object, a focusing lens and a spectrometer.

2. A wide range of spectral confocal displacement detection apparatus according to claim 1, wherein: the Fresnel lens is located between the beam splitter prism and a measured object, and the main focal length of the Fresnel lens can be set according to actual requirements.