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CN-116772713-B - Device and method for measuring glass tube wall based on time domain spectrum interference

CN116772713BCN 116772713 BCN116772713 BCN 116772713BCN-116772713-B

Abstract

The invention discloses a measuring device and a measuring method for a glass tube wall based on time domain spectrum interference, wherein the measuring device comprises a femtosecond laser used for emitting a coherent light source, an optical fiber circulator connected with the femtosecond laser, an optical fiber collimator connected with the optical fiber circulator, an optical fiber amplifier connected with the optical fiber circulator and used for amplifying a pulse signal of femtosecond pulse return light, a dispersion compensation optical fiber connected with the optical fiber amplifier, and a photoelectric detection and data acquisition device connected with the dispersion compensation optical fiber. The invention uses the spectrum interference effect between two return light pulses reflected by the upper and lower surfaces of the glass wall, and uses the interference fringe period to calculate the pulse interval and further calculate the wall thickness. The invention can realize the measuring function through a simple laser receiving and transmitting and data processing device, and the scheme has the advantages of simplicity, reliability, rapidness and high precision.

Inventors

  • LU QIAO

Assignees

  • 南京信息工程大学

Dates

Publication Date
20260508
Application Date
20230615

Claims (8)

  1. 1. The measuring method is characterized by comprising a femtosecond laser (1) for emitting a coherent light source, an optical fiber annular device (2) connected with the femtosecond laser (1), an optical fiber collimator (3) connected with the optical fiber annular device (2), an optical fiber amplifier (5) connected with the optical fiber annular device (2) and used for amplifying a pulse signal of femtosecond pulse return light, a dispersion compensating optical fiber (6) connected with the optical fiber amplifier (5), and a photoelectric detection and data acquisition device (7) connected with the dispersion compensating optical fiber (6), wherein the central lines of the femtosecond laser (1), the optical fiber annular device (2) and the optical fiber collimator (3) are positioned at the same horizontal position, the coherent light source emitted by the femtosecond laser (1) sequentially passes through the optical fiber annular device (2) and the optical fiber collimator (3) to be measured, the upper surface and the lower surface of the pipe wall of the glass to be measured are reflected to form two femtosecond pulse return lights with a certain time interval, and the femtosecond pulse return lights sequentially pass through the optical fiber collimator (3), the annular device (2), the optical fiber amplifier (5) and the photoelectric detection and the dispersion compensating optical fiber (7) are acquired by the optical fiber and the optical fiber acquisition device; the method comprises the following steps: s1, a femtosecond laser is incident to the upper surface and the lower surface of the pipe wall of a glass pipe to be detected through an optical fiber circulator and an optical fiber collimator, the pipe wall is reflected twice to form two femtosecond pulse return lights with a certain time difference, and the femtosecond pulse return lights return to the optical fiber collimator to form return light pulse signals; s2, the return pulse signals enter an optical fiber amplifier through an optical fiber circulator for amplification and then enter a dispersion compensation optical fiber for time stretching, the spectrum information of the return pulse is mapped to a time domain, and then the time domain signals are transmitted through a photoelectric detection and data acquisition device; S3, calculating the thickness of the glass tube wall through the acquired time domain signals, wherein the method for calculating the thickness of the glass tube wall is as follows: The method comprises the steps of detecting time domain signals (T, U) through a photoelectric detection and data acquisition device, wherein T represents time, U represents voltage, framing continuously acquired return light pulses according to pulse period length (T, U), determining mapping coefficients K of the time domain spectrum according to characteristic intervals of the pulse spectrum, and determining how long the spectral width of 1nm can be stretched by the K according to characteristic intervals of the pulse spectrum, wherein time domain coordinates T can be converted into spectra through the coefficients K, and further converted into frequency coordinates Wherein Is the speed of light, which is the speed of light, Is the central wavelength of the light source, and each frame is subjected to inverse fast Fourier transform to obtain an autocorrelation trace curve, and the frequency domain interference period obtained by curve peak searching is the time interval Wall thickness of glass Wherein n is the refractive index of the glass.
  2. 2. The method for measuring the glass tube wall based on time domain spectrum interference according to claim 1, wherein the femtosecond laser (1) is connected with the optical fiber circulator (2) through an input end tail fiber connector of the optical fiber circulator (2), a straight-through output end tail fiber of the optical fiber circulator (2) is connected with a tail fiber of the optical fiber collimator (3) in a fusion mode, and the tail fiber at the other end of the optical fiber circulator (2) is connected with an input end of the optical fiber amplifier (5) in an optical fiber fusion mode.
  3. 3. The method for measuring the glass tube wall based on time domain spectrum interference according to claim 1, wherein the output end optical fiber of the optical fiber amplifier (5) is in fusion connection with the input end optical fiber of the dispersion compensation optical fiber (6), and the other end of the dispersion compensation optical fiber (6) is connected with a signal light input joint of the photoelectric detection and data acquisition device (7).
  4. 4. The method for measuring a glass tube wall based on time domain spectral interferometry according to claim 1, wherein the measuring device further comprises a computer (8) connected with the photoelectric detection and data acquisition device (7), and the computer (8) is connected with the photoelectric detection and data acquisition device (7) through a data line.
  5. 5. The method for measuring the glass tube wall based on time domain spectrum interference according to claim 1, wherein the femtosecond laser (1) meets the following conditions that the central wavelength 1560nm plus or minus 20nm, the full width at half maximum of the spectrum is > 0.5 nm, the repetition frequency is 10 kHz-50 MHz, and the single pulse energy is >1 nJ.
  6. 6. The method for measuring the glass tube wall based on time domain spectrum interference according to claim 1, wherein the wall thickness of the glass tube to be measured, which is suitable for the measuring device, is 0.1-50 mm.
  7. 7. The method for measuring a glass tube wall based on time-domain spectral interferometry according to claim 1, characterized in that the total dispersion of the dispersion compensating fiber (6) is >500ps/nm.
  8. 8. The method for measuring a glass tube wall based on time-domain spectral interferometry according to claim 1, wherein in step S3, the thickness of the glass tube wall is calculated by a computer (8) connected to a photoelectric detection and data acquisition device.

Description

Device and method for measuring glass tube wall based on time domain spectrum interference Technical Field The invention relates to a measuring device and a measuring method for a glass tube wall, in particular to a measuring device and a measuring method for a glass tube wall based on time domain spectrum interference, and belongs to the field of laser interferometry. Background The glass tube has wide application in production and life, and has high requirements on the outer diameter, the inner diameter and the wall thickness of the glass tube in some application scenes, such as medical glass bottles, measuring cylinders and the like. In order to ensure the consistency and accuracy of the glass tube, the thickness of the glass tube needs to be measured and regulated on line in the production of the glass tube. Since the glass tube has a circular ring-shaped structure, the laser thickness gauge conventionally used for the thickness measurement of the flat panel type is no longer applicable. The method has the advantages that the method is low in detection efficiency, poor in precision and consistency, difficult to meet the requirements of mass production and quality control, and finally, the measuring method can only measure the tube head and the tube tail, belongs to local measurement and does not have the capability of measuring the thickness body distribution of the glass tube. There are measurement hysteresis, randomness and locality issues. The light transmission characteristic of the glass enables the thickness to be measured more conveniently by adopting an optical method, for example, a glass plate thickness monitoring device (authorized bulletin No. CN 206056517U) is proposed by Luo glass group Luoyang Long glass limited company, a scheme of using a sweep continuous laser to enter the glass and detecting the light intensity of a return light signal is adopted, the signal is enhanced when the wavelength of the laser just reaches the transmission peak of the glass plate by utilizing the Fabry-Perot effect (FP) of the glass plate, and the glass thickness is calculated by utilizing the wavelength difference between two enhanced signals. The method depends on the FP effect of the glass plate, cannot be used in a curved glass tube scene, and the light intensity detection disturbance and the wavelength scanning precision of the laser seriously influence the measurement function and precision, so that the optical path debugging and calibration are complex, and the method is not beneficial to the application of industrial sites. Disclosure of Invention The invention aims to provide a simple, reliable, rapid and high-precision measuring device for a glass tube wall based on time domain spectrum interference, which is used for measuring pulse thickness by a spectrum interference method based on femtosecond laser and realizing spectrum-time domain mapping conversion of femtosecond pulses by a dispersion compensation optical fiber, so that spectrum interference period information can be obtained by adopting simple and universal data acquisition equipment, and the glass tube thickness information can be rapidly analyzed, real-time measurement data can be provided for production, and the other aim of the invention is to provide a measuring method for the glass tube wall based on time domain spectrum interference. The invention provides a measuring device for a glass tube wall based on time domain spectrum interference, which comprises a femtosecond laser used for emitting a coherent light source, an optical fiber annular device connected with the femtosecond laser, an optical fiber collimator connected with the optical fiber annular device, an optical fiber amplifier connected with the optical fiber annular device and used for amplifying a pulse signal of femtosecond pulse return light, a dispersion compensation optical fiber connected with the optical fiber amplifier, and a photoelectric detection and data acquisition device connected with the dispersion compensation optical fiber, wherein the central lines of the femtosecond laser, the optical fiber annular device and the optical fiber collimator are positioned at the same horizontal position, the coherent light source emitted by the femtosecond laser sequentially passes through the optical fiber annular device and the optical fiber collimator to be irradiated on the glass tube to be measured, the upper surface and the lower surface of the tube wall of the glass tube to be measured are reflected to form two femtosecond pulse return lights with a certain time interval, and the femtosecond pulse return lights are sequentially acquired by the photoelectric detection and data acquisition device after passing through the optical fiber annular device, the optical fiber annular device and the optical fiber amplifier and the dispersion compensation optical fiber. As a further improvement of the scheme, the femtosecond laser is connected with the optical fiber circulat