CN-121977447-A - Non-contact narrow space shape measurement system with direction switching function

Abstract

The invention discloses a non-contact narrow space shape measurement system with a direction switching function, which comprises a low-coherence light source, a polarization direction switcher, a circulator, a coupler, a measurement arm, a reference arm, a spectrometer, a computer, an indicating laser and an object to be measured, wherein the visible light emitted by the indicating laser is used for adjusting the light path, the invisible light emitted by the low-coherence light source is used for switching and controlling P light (depth direction measurement) or S light (side direction measurement) through the polarization direction switcher, the P light or the S light is input into the coupler through the circulator and is divided into two beams of light to be respectively input into the measurement arm and the reference arm, the reflected measurement light and the reference light are converged at the coupler to generate interference, and then are input into the spectrometer through the circulator, and interference signals in the spectrometer are collected and processed through the computer to obtain the optical path difference between the measurement light and the reference light. According to the invention, the measuring directions of the depth direction and the side direction can be switched according to the measuring requirements, so that the depth and the aperture of the blind hole can be accurately measured.

Inventors

• ZHAO HUINING
• CHEN SHUAI
• Xi Yunan
• ZHU YUEYANG
• WANG BO
• XIA HAOJIE

Assignees

• 合肥工业大学

Dates

Publication Date

20260505

Application Date

20260316

Claims (2)

1. 1. The non-contact narrow space shape measurement system with the direction switching function is characterized by comprising a low-coherence light source (1), a polarization direction switcher (2), a circulator (3), a coupler (4), a measurement arm (5), a reference arm (6), a spectrometer (7), a computer (8), an indicating laser (9) and an object to be measured (10); The measuring arm (5) comprises an optical fiber focusing device (51), 2 quarter wave plates, a rotating motor (53), a polarized beam splitter (54), an XY displacement table (55), a Z displacement table (56) and a probe (57), wherein the measured object (10) is placed on the XY displacement table (55), the probe (57) is carried on the Z displacement table (56), the optical axis of the first quarter wave plate (52 a) is arranged at 45 degrees relative to the polarization direction of incident light, and the second quarter wave plate (52 b) and the polarized beam splitter (54) are both arranged on the rotating motor (53); The reference arm (6) comprises a collimator (61), a reflecting mirror (62) and a displacement table (63); The indicating laser (9) emits visible light to be split into a measuring arm (5) and a reference arm (6) through the coupler (4), and the visible light irradiates the surfaces of the measured object (10) and the reflecting mirror (62) respectively; the invisible light emitted by the low-coherence light source (1) is subjected to switching control of the polarization direction switcher (2) to obtain P polarized light or S polarized light, and the P polarized light or the S polarized light is input into the coupler (4) through the circulator (3) so as to be divided into two light beams with the power ratio of 9:1, wherein the light with higher output power is input into the measuring arm (5) and the light with lower output power is input into the reference arm (6); The light input into the measuring arm is input into a first quarter wave plate (52 a) after passing through an optical fiber focusing device (51), so that the polarization state of incident light is converted into circularly polarized light, the circularly polarized light is converted into linearly polarized light again after passing through a second quarter wave plate (52 b) and is input into a polarized beam splitter (54), the P polarized light with the vibration direction parallel to the incident surface is transmitted through the polarized beam splitter (54) and directly irradiates the surface of an object (10) to be measured, or the S polarized light with the vibration direction perpendicular to the incident surface is reflected by the polarized beam splitter (54) to the surface of the object (10) to be measured, and then the polarized beam splitter (54), the 2 quarter wave plates and the optical fiber focusing device (51) are sequentially returned to the coupler (4) after being reflected by the object (10) to be measured, and measuring light is obtained; The light input into the reference arm irradiates to the surface of a reflecting mirror (62) through the collimator (61), and the obtained reflected light returns to the coupler (4) after passing through the collimator (61) again, and the reference light is obtained; After the measuring light and the reference light are converged in the coupler (4), interference signals are generated, the interference signals are input into the spectrometer (7) through the circulator (3), and the interference signals in the spectrometer (7) are acquired and processed through the computer (8) to obtain the optical path difference between the measuring light and the reference light; If the optical path difference between the measuring light and the reference light is in the interference range, using a polarization direction switcher (2) to switch the invisible light emitted by the low coherence light source (1) into P polarized light for measuring the depth direction of the measured object (10), and controlling an XY displacement table (55) and a Z displacement table (56) to respectively adjust the measuring direction and the depth direction in the measuring process by a computer (8) so that the optical path of the measuring light is in a measuring range, thereby obtaining the surface morphology of the measured object (10); Or the invisible light emitted by the low-coherence light source (1) is switched to S polarized light by using the polarization direction switcher (2) and used for measuring the side direction of the measured object (10), and the XY displacement table (55) and the Z displacement table (56) are controlled by the computer (8) to respectively adjust the measuring direction and the depth direction in the measuring process so that the optical path of the measured light is in a measuring range; If the optical path difference is not within the interference range, the displacement stage (63) is adjusted so that the optical path difference between the measurement light and the reference light is within the interference range.
2. 2. The non-contact narrow space shape measuring system with direction switching function according to claim 1, wherein the computer (8) collects and processes the interference signal as follows: S1, the computer (8) collects interference signals and intercepts a section of interference spectrum close to the central wavelength, so as to obtain the interference spectrum shown in the formula (1) : (1) In the formula (1), the components are as follows, Representing wavelength; a spectral intensity distribution function representing the invisible light emitted by the low coherence light source (1); And The reflection coefficients of the reflecting mirror (62) and the measured object (10) are respectively shown, wherein n represents the refractive index of air, theta represents the initial phase of an interference spectrum, and d represents the optical path difference between measuring light and reference light; S2, the computer (8) singly collects the spectrum of the reference light for interference spectrum Shaping to obtain a shaped interference spectrum represented by formula (2) : (2) In the formula (2), the amino acid sequence of the compound, Representing a window function; S3, obtaining by using formula (3) Fourier transform representation of (a) : (3) In the formula (3), k is the actual center frequency of the interference spectrum, and Y is a window function Is used for the fourier transform of (a), A variable representing the delay of the optical path, Representing a convolution; s4, by pairing Performing four-spectral line interpolation to construct a fitting function of Y as shown in formula (4) ; (4) In the formula (4), the amino acid sequence of the compound, 、 Representing the actual center frequency point of the interference spectrum 2 Spectral lines with the largest amplitude on the left side of (c), 、 Representing the actual center frequency point of the interference spectrum 2 Spectral lines with the largest amplitude on the right side of (c), Representing the actual center frequency point And (3) with And (2) difference of (2) ,0≤ Is less than or equal to 1, and , , , ; S5, pairing Performing four-spectral line interpolation to construct an interference spectrum fitting function shown in formula (5) : (5) In the formula (5), the amino acid sequence of the compound, A fourier transform representing the interference spectrum; S6, according to Obtaining Thereby obtaining the actual center frequency of the interference spectrum Wherein, the method comprises the steps of, A table inverse function; S7, according to the center frequency k, obtaining an optical path difference d by using the formula (6): (6) In the formula (6), c represents the speed of light, N represents the data cut-off length of the interference spectrum, Representing the optical frequency separation of the interference spectrum.

Description

Non-contact narrow space shape measurement system with direction switching function Technical Field The invention belongs to the field of precise optical measurement, and particularly relates to a non-contact narrow space shape measurement system with a direction switching function. Background At present, the traditional industrial manufacturing industry faces deep transformation, the processing fineness requirement of countless emerging industries on products is higher and higher, and high-end and intelligent production technology becomes an important support for industrial upgrading and building industrial strong countries. The accurate and rapid detection of the parts is realized, and the door-facing pin for accurate manufacture is formed. Along with the increasing complexity of the functions of modern equipment, parts with complex and various structures are more and more, and the measurement of parameters such as shape errors of the microstructure on the surface of a product becomes an important basis for evaluating the quality of the parts and adjusting the production process. The measuring requirement of the hole piece is that not only the side surface direction size of the hole is required to be detected, but also the depth direction measurement is required to be completed, and the precision of the hole axis relative to the opening end surface is evaluated in the form of geometric tolerance. According to whether the measuring system is in contact with the sample or not, the hole part parameter measuring technology can be divided into two types of contact type measurement and non-contact type measurement. Contact measurement refers to measurement by means of mechanical contact, and such measurement techniques have been developed earlier, mainly including stylus measurement and scanning probe microscopy measurement. The stylus is driven to move on the surface to be measured by a micro-displacement controller, the sensor detects the height change of the stylus along with the fluctuation of the surface of the sample, the scanning probe microscopy technology is divided into a scanning tunnel microscope and an atomic force microscope, and the probe contacting the surface of the sample is moved to measure the parameters of the hole piece point by point. The contact type measuring precision is higher, repeatability is good, but the needle point is easy to damage the sample, and meanwhile, the precision is reduced due to abrasion, and the contact type measuring precision is limited by the structural size of the probe, so that the parameters of the hole piece are difficult to accurately measure when the micro-pore structure with the large depth-diameter ratio and the surface side wall are measured. The non-contact measurement is performed by electric field, optical, ultrasonic, etc. techniques, including scanning electron microscopy, optical measurement, ultrasonic, etc. The optical measurement obtains the morphology information of the microscopic profile of the sample surface after analyzing the optical signal, can overcome the defect of non-contact measurement, has the advantages of rapidness, simple operation process and the like, and has wide application in the field of pore member measurement. Based on different principles, the optical measurement technology mainly comprises a zoom deep microscope technology, a laser confocal microscope technology, an interferometry technology and the like. The interferometry technology is developed rapidly, and is the most main hole parameter measurement technology at present, and mainly comprises monochromatic light phase shift interferometry, white light vertical scanning interferometry and white light spectrum interferometry. The optical coherence tomography in the white light spectrum interference technology has the advantages of rapidness, no damage, high precision and the like, and is a hole part parameter detection scheme with very wide development prospect. However, most of these optical methods can only measure radial surface distance, and it is difficult to measure distance in depth direction, so there are problems that blind hole depth cannot be measured accurately, evaluation based on geometric tolerance of hole is difficult, and the like. Therefore, it is desirable to design a system and method for measuring the shape of a narrow space. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides a non-contact narrow space shape measurement system with a direction switching function, so that the measurement directions of the depth direction and the side direction can be switched according to the measurement requirements, and the depth and the aperture of a blind hole can be accurately measured. In order to achieve the aim of the invention, the invention adopts the following technical scheme: The invention relates to a non-contact narrow space shape measurement system with a direction switching function, which is characterize