CN114136233A - Inner hole surface profile measuring system and method - Google Patents
Inner hole surface profile measuring system and method Download PDFInfo
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- CN114136233A CN114136233A CN202111374980.8A CN202111374980A CN114136233A CN 114136233 A CN114136233 A CN 114136233A CN 202111374980 A CN202111374980 A CN 202111374980A CN 114136233 A CN114136233 A CN 114136233A
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- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
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Abstract
The invention discloses a measuring system and a method for the surface profile of an inner hole, the system comprises a light path module, a signal acquisition module, an imaging module, a transverse scanning module and a motion control module, the motion control module is connected with the transverse scanning module and is used for controlling the transverse scanning module to do rotary motion and/or axial motion along the inner hole of the tested sample, the light emitted by the light path module is transmitted to the transverse scanning module, the transverse scanning module converges the light on the surface of the measured sample to form a light spot, and returning the light reflected by the surface of the tested sample to the optical path module to generate interference signals by interference in the optical path module, the signal acquisition module is connected with the light path module and the imaging module and used for acquiring the interference signal of the light path module and sending the interference signal to the imaging module. The invention can ensure the measurement precision and simultaneously go deep into the hole to restore the complete internal information of the hole.
Description
Technical Field
The invention relates to the field of non-contact three-dimensional measurement, in particular to a system and a method for measuring a surface profile based on an inner hole.
Background
The existing three-dimensional measuring method for the surface profile of the inner hole is commonly used in a grating projection method, a magnetic leakage method, an infrared temperature measuring sensor method, an ultrasonic method and the like. The detection technologies are used for detecting a certain specific range at the hole inlet, and the used method has physical characteristics based on magnetic fields, sound waves and the like, has certain requirements on the detection environment and is greatly influenced by the surrounding environment medium. In the process of acquiring an image by using a grating projection method, due to the particularity of the hole, the shadow area influences the acquisition of data, so that the reconstruction precision of the hole is low, and the information in the deep hole cannot be completely restored; the magnetic leakage method has the advantages of more interference factors and low resolution in the detection process; the infrared temperature measurement sensor method cannot detect the size of the pore and has certain limitation; the ultrasonic method needs a coupling medium for detection, and the main frequency and the piezoelectric conversion efficiency of the sensor influence the final detection efficiency.
The above background disclosure is only for the purpose of assisting understanding of the concept and technical solution of the present invention and does not necessarily belong to the prior art of the present patent application, and should not be used for evaluating the novelty and inventive step of the present application in the case that there is no clear evidence that the above content is disclosed at the filing date of the present patent application.
Disclosure of Invention
In order to solve the technical problems, the invention provides a system and a method for measuring the surface profile of an inner hole, which can penetrate into the hole while ensuring the measurement accuracy and restore the complete internal information of the hole.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention discloses a measuring system for the surface profile of an inner hole, which comprises a light path module, a signal acquisition module, an imaging module, a transverse scanning module and a motion control module, the motion control module is connected with the transverse scanning module and is used for controlling the transverse scanning module to do rotary motion and/or axial motion along the inner hole of the tested sample, the light emitted by the light path module is transmitted to the transverse scanning module, the transverse scanning module converges the light on the surface of the measured sample to form a light spot, and returning the light reflected by the surface of the tested sample to the optical path module to generate interference signals by interference in the optical path module, the signal acquisition module is connected with the light path module and the imaging module and used for acquiring the interference signal of the light path module and sending the interference signal to the imaging module.
Preferably, the optical path module comprises a swept-frequency light source and an interferometer, wherein the interferometer comprises a first fiber coupler, a second fiber coupler, a fiber circulator, a fiber delay line and a reference mirror.
Preferably, light emitted by the swept-frequency light source enters the first optical fiber coupler and is divided into two paths of light, the first path of light is transmitted to the transverse scanning module after passing through the optical fiber circulator, the transverse scanning module collects light reflected by the surface of the sample to be measured and returns to the optical fiber circulator, and the optical fiber circulator transmits the light to the second optical fiber coupler as a first part of coupled light; the second path of light sequentially passes through the optical fiber circulator and the optical fiber delay line and then irradiates the reference mirror, the light reflected by the reference mirror returns to the optical fiber circulator, the optical fiber circulator transmits the light to the second optical fiber coupler to serve as a second part of coupled light, and the first part of the coupled light and the second part of the coupled light interfere to generate the interference signal.
Preferably, the first optical fiber coupler is an 80-20 optical fiber coupler, and the second optical fiber coupler is a 50-50 optical fiber coupler.
Preferably, the signal acquisition module includes a balanced amplified photodetector, a data acquisition card and an image acquisition card, the balanced amplified photodetector is configured to detect the interference signal of the optical path module, the data acquisition card is configured to sample according to a predetermined frequency, and the image acquisition card is configured to convert an electrical signal sampled by the data acquisition card into a digital image.
Preferably, the transverse scanning module comprises an optical probe, the optical probe comprises a green lens and a right-angle prism, and light emitted by the light path module passes through the green lens and is emitted onto the right-angle prism, and is reflected to the surface of the measured sample through the right-angle prism.
Preferably, the motion control module includes step motor, linear electric motor and optic fibre rotary connector, step motor connects horizontal scanning module is in order to drive rotary motion is made to horizontal scanning module, linear electric motor connects step motor is in order to drive step motor with horizontal scanning module is together followed the axial motion of the hole of surveyed the sample, optic fibre rotary connector is equipped with stiff end and rotatory end, wherein the stiff end is connected the output of light path module, rotatory end is connected horizontal scanning module.
The invention also discloses an inner hole surface profile measuring method, which adopts the inner hole surface profile measuring system to measure and comprises the following steps: the optical path module, the motion control module and the signal acquisition module are synchronously controlled according to a time sequence relation, light emitted by the optical path module is transmitted to the transverse scanning module, the transverse scanning module is controlled by the motion control module to make rotary motion and/or axial motion along an inner hole of a measured sample, the transverse scanning module converges the light on the surface of the measured sample to form a light spot and returns the light reflected by the surface of the measured sample to the optical path module, the light path module generates interference signals after receiving the returned light, the signal acquisition module acquires the interference signals and sends the interference signals to the imaging module, and the imaging module images to measure the surface profile of the inner hole.
Preferably, the synchronously controlling the light path module, the motion control module and the signal acquisition module according to the time sequence relationship specifically includes: determining the number of sampling points of the signal acquisition module in each trigger period according to the sweep frequency speed of a light source in the light path module and the sampling frequency of the signal acquisition module, driving the light source to sweep frequency at the lower edge of a trigger signal of each signal acquisition module, and simultaneously driving the signal acquisition module to sample; and when the number of sampling points in the circumferential direction of the inner hole acquired by the signal acquisition module reaches a preset value, controlling the motion control module to start so as to ensure that each circumferential scan is followed by axial motion, and then executing the next circumferential scan until the whole inner hole profile is completely scanned.
Preferably, the imaging module imaging to measure the inner hole surface profile specifically includes: the imaging module carries out filtering processing on the received interference signal, obtains the depth information of the measured sample through Fourier transformation, and stores the depth information in rectangular coordinates after interpolation processing and coordinate transformation to obtain the measurement information of the surface profile of the inner hole.
Compared with the prior art, the invention has the beneficial effects that: the inner hole surface profile measuring system and method provided by the invention are based on the transverse scanning module which can simultaneously perform rotary motion and axial motion, compared with the existing optical three-dimensional measuring scheme, the inner hole surface profile measuring system and method can deeply restore the internal three-dimensional appearance in a hole, and the problems of difficult inner hole surface profile measurement and incomplete measurement data are solved. In addition, the invention adopts a precise optical coherence measurement mode, the axial resolution and the transverse resolution of the invention reach the micron level, and the invention has the characteristic of high detection precision.
In a further scheme, all modules are connected by optical fibers, the interference caused by environmental factors is small, and meanwhile, the interference signal contrast is improved, so that the result is clearer, and the system signal-to-noise ratio is higher.
In a further scheme, each device can be synchronously controlled according to a time sequence to finish the real-time acquisition and analysis of signals, and a fast frequency sweeping laser light source is adopted to be matched with a single-point detection time coded spectrum signal, so that the method has the characteristics of high scanning speed and high efficiency.
Drawings
FIG. 1 is a block diagram of a system for measuring the surface profile of an internal bore in accordance with a preferred embodiment of the present invention;
FIG. 2 is a block diagram of the package of the internal bore surface profile measurement system of the preferred embodiment of the present invention;
FIG. 3 is a schematic diagram of the connection of the motion control module and the transverse scanning module of the inner bore surface profile measurement system of the preferred embodiment of the present invention;
FIG. 4 is a schematic flow chart of a method for measuring the surface profile of an internal bore in accordance with a preferred embodiment of the present invention;
FIG. 5 is a graph illustrating the effect of measuring the profile of the inner bore surface of a transmission valve body according to an embodiment of the present invention;
fig. 6a and 6b are diagrams of analysis of the surface profile of the inner bore of the transmission valve body according to an embodiment of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings and preferred embodiments.
As shown in fig. 1, a preferred embodiment of the present invention discloses an inner bore surface profile measuring system, which includes a light path module 10, a signal acquisition module 20, an imaging module 30, a transverse scanning module 40 and a motion control module 50, wherein the motion control module 50 is connected to the transverse scanning module 40 for controlling the transverse scanning module 40 to perform a rotational motion and/or an axial motion along an inner bore of a sample to be measured, near-infrared light emitted by the light path module 10 is transmitted to the transverse scanning module 40 through an optical fiber, the transverse scanning module 40 focuses the near-infrared light on a surface of the sample to be measured to form a light spot, and the light reflected by the surface of the measured sample is returned to the optical path module 10 to generate interference signals in the optical path module 10, and the signal acquisition module 20 is connected to the optical path module 10 and the imaging module 30 and is used for acquiring the interference signals of the optical path module 10 and sending the interference signals to the imaging module 30.
Specifically, the optical path module 10 includes a swept-frequency light source 11 and an interferometer 12, and the interferometer 12 includes an 80-20 fiber coupler 121, a 50-50 fiber coupler 122, a fiber circulator 123, a fiber delay line 124 and a reference mirror 125; the signal acquisition module 20 comprises a balanced amplification photoelectric detector 21, a data acquisition card 22 and an image acquisition card 23; the imaging module 30 includes a computer 31; the transverse scanning module 40 includes an optical probe 41, the optical probe 41 includes a green lens 411 and a right-angle prism 412; the motion control module 50 includes a stepping motor 51, a linear motor 52, and a fiber rotation connection line 53.
The sweep frequency light source 11 is used for emitting near infrared light and has the characteristics of linear change of scanning frequency, narrow instantaneous line width, wide sweep frequency range and high output power; the interferometer 12 belongs to the michelson interferometer.
The optical path module 10 may be divided into a sample arm optical path and a reference arm optical path according to an optical path structure. The sample arm optical path comprises a tested sample 60, an optical probe 41, a motion control module 50 and a fiber circulator 123, and the reference arm optical path comprises a reference mirror 125, a fiber delay line 124 and a fiber circulator 123. As shown in fig. 2, the two optical paths connected to the two optical fibers at the right end output of the 50-50 fiber coupler 122 represent the two optical paths of the sample arm and the reference arm, respectively.
The light propagates in the sample and reference arms as follows: light is output from the swept-frequency light source 11, enters the 80-20 fiber coupler 121, and is divided into two paths of light, wherein one path of light enters the sample arm, and the other path of light enters the reference arm. The light entering the sample arm reaches the Green lens 411 in the transverse scanning module 40 through the optical fiber circulator 123 and the optical fiber rotary connecting line 53, then the light enters the Green lens 411 to focus the light beam and output the light beam to the right-angle prism 412 in the transverse scanning module 40 in a collimation manner, the direction of the light is changed after the light is reflected by the right-angle prism 412, the light is irradiated to the surface of the tested sample 60 from the side surface, and the light returns to the inlet of the 50-50 optical fiber coupler 122 as a part of the coupled light according to the original light path after being reflected by the tested sample 60. The light entering the reference arm directly irradiates the reference mirror 125 through the optical fiber circulator 123 and the optical fiber delay line 124, is reflected by the reference mirror 125, and returns to the entrance of the 50-50 optical fiber coupler 122 as another part of the coupled light according to the original light path.
The 80-20 optical fiber coupler 121 can improve the reflected signal with a weaker sample arm and generate interference with equal intensity; interference of two paths of light in the sample arm and the reference arm can be realized by adopting a 50-50 optical fiber coupler 122; the fiber optic circulator 123 allows bi-directional transmission of light over one fiber; the optical fiber delay line 124 finely adjusts the optical path of the reference arm, so as to find the position of the zero optical path; the reference mirror 125 receives the light input in the reference arm and reflects it back. The light path part is integrally packaged in the instrument shell, so that the stability of the light path structure is ensured.
The balanced amplification photoelectric detector 21 in the signal acquisition module 20 is used for detecting the interference spectrum signal output by the interferometer 12; the data acquisition card 22 realizes real-time data acquisition, synchronously controls the output light of the sweep frequency light source 11 through a trigger signal, the data acquisition card 22 selects a sampling point according to a certain frequency for sampling, and the motion control module 50 is matched with the sweep frequency light source 11 and the data acquisition card 22 to drive the optical probe 41 to rotate and advance; the image acquisition card 23 is used for sampling, quantifying and converting the electrical signals acquired by the data acquisition card 22 into digital images.
The imaging module 30 includes a computer 31 for hardware control, interface interaction, data acquisition, processing, and display. The method comprises the steps of realizing inner hole surface imaging based on a rotary probe through a demodulation algorithm, carrying out Fourier transformation on interference spectrum signals to obtain depth information of the inner hole in the circumferential direction, converting the interference signals in a spectrum space into depth space coordinate values, reconstructing a two-dimensional image through a coordinate transformation and interpolation algorithm, and reconstructing three-dimensional point cloud through a volume rendering algorithm through a two-dimensional slice image sequence.
The transverse scanning module 40 comprises an optical probe 41, wherein the optical probe 41 comprises a Green lens 411 and a right-angle prism 412 plated with a high-reflection dielectric film; the sample light is emitted from the single-mode fiber to the right-angle prism 412 through the Green lens 411, reflected by the right-angle prism 412, and emitted vertically, and then strikes the surface of the sample 60 to be measured.
The motion control module 50 includes a stepper motor 51, a linear motor 52, and a fiber optic rotary connector 53. The stepping motor 51 drives the optical probe 41 to rotate at a high speed, so that circumferential scanning is realized; the linear motor 52 drives the optical probe 41 to move forward and backward, so that axial scanning is realized; the fiber optic rotary connector 53 is used as a transmission medium for the stationary platform and the rotary platform, so that light is transmitted during the rotation process. As shown in fig. 3, the optical fiber rotary connector 53 has a fixed end 531 and a rotary end 532, the fixed end 531 is connected to the output end of the optical path of the sample arm and fixed on the housing, and the rotary end 532 is connected to the optical probe 41; the linear motor 52 is fixed on the outer side, the stepping motor 51 and the optical probe 41 are driven to do linear motion back and forth together, the optical probe 41 is connected to the rotating shaft 511 of the stepping motor 51 to rotate circumferentially under the driving of the stepping motor 51, and the scanning in the circumferential direction and the axial direction of the inner hole is realized by matching with the light path output.
The inner hole surface profile measuring system of the preferred embodiment of the invention has the advantages of high imaging speed, good scanning precision and high detection efficiency, is suitable for complex environment and can be used for batch detection; the measurement precision is guaranteed, meanwhile, the hole is deepened into the hole, and the complete internal information of the hole is restored. However, the existing optical measurement methods, such as structured light measurement, can only measure a part of the three-dimensional shape at the entrance of the hole.
Referring to fig. 4, another preferred embodiment of the present invention discloses a method for measuring the surface profile of an inner hole, based on the scenario of the system for measuring the surface profile of an inner hole shown in fig. 2, comprising the following steps:
s1: hardware system and software system preparation: and starting a system hardware power switch, and opening the inner hole surface profile measuring software. The measurement software comprises functions of data acquisition, three-dimensional reconstruction, image display, measurement and the like. The data acquisition part transmits a trigger signal to the serial port to control the sweep frequency light source 11, the data acquisition card 22 and the motion control module 50 to realize synchronous image acquisition; the three-dimensional reconstruction part realizes scanning imaging through a reconstruction algorithm and reconstructs three-dimensional point cloud from a two-dimensional image; image display includes real-time display, scaling, etc. of images; the measuring part comprises information such as the length and the diameter of the point cloud of the measured and reconstructed inner hole.
S2: and (3) signal testing: zero point test is needed after the system runs, and the test aims to find the position with zero optical path difference, debug the light intensity of the sample arm and the reference arm and optimize the interference contrast. An ASCII serial port scanning command is sent to the adjustable electric control optical fiber delay line 124 through a serial port, zero-order interference wave peaks are found through scanning, software prompts that zero-point positions are found successfully after the zero-optical-path-difference positions are determined, whether the positions are found again is selected according to actual two-dimensional image effects in the software at the moment, and the positions with the most obvious interference effects are found and serve as the positions of the zero points.
S3: and (3) scanning control: synchronously controlling the rotation of the stepping motor 51, the forward movement of the linear motor 52, the signal acquisition of the data acquisition card 22 and the frequency sweep of the frequency sweep light source 11 according to the time sequence relation. According to the sweep frequency speed fkHz, the trigger signal period of 1000/f mu s, the number N of sampling points and the sampling frequency f of the system sweep frequency light source 11sIs equal to N/fsAnd calculating to collect N sampling points in each trigger period. According to the duty ratio of the light source, the image acquisition card 23 sets that only a certain percentage of sampling points are acquired in each period so as to ensure that the spectral bandwidth is fully utilized and no useless signal is acquired. The sweep frequency light source 11 is driven to sweep frequency at the falling edge of each trigger signal, and the data acquisition card 22 is driven to acquire N pieces of sampling point data at the same time. When the software triggers the image acquisition card 23 to acquire sampling point data in the circumferential direction of the inner hole, the software sends a command to the serial port to control the linear motor 52 to move forward, so that axial movement is performed after each circumferential scan, and the next circumferential scan is completed after the axial movement until the whole inner hole profile is scanned.
Step S4, image processing: the obtained interference signal is firstly filtered, then the depth information of the tested sample is obtained through Fourier transformation, and the depth information is stored in rectangular coordinates after interpolation processing and coordinate conversion. The image processing includes signal filtering, fourier transformation, coordinate transformation and interpolation. In order to reduce the influence of the autocorrelation term and the direct current term in the signal on the sample signal, low-frequency filtering is firstly carried out on the direct current component. And acquiring a reference signal without a sample signal as background noise, and subtracting the background noise from a subsequently acquired signal, namely eliminating a direct current term and an autocorrelation term.
The current detected by the balanced amplified photodetector 21 can be expressed as:
the above equation sums the three terms to calculate the total detected intensity received by the balanced amplified photodetector 21, where S (k) represents the light source power spectrum, RSnThe reflectivity of the nth layer in the sample, N represents the number of different reflective layers, ρ represents the response coefficient of the balanced amplification photodetector 21, and zSnRepresents the axial position of the n-th layer in the measured sample, zSmRepresenting the axial position of the mth layer in the tested sample, and the second term and the third term containing m and n represent mutual interference generated by different depths; z is a radical ofRIs the mirror position; k represents a wave number. The first term in the above formula isAnd the direct current term is irrelevant to the delay quantity of two light paths of the sample arm and the reference arm and is removed through low-frequency filtering. The second item is a cross-correlation item which carries the information of the depth direction of the measured sample. The third term is an autocorrelation term, which is generated by the interference of tissues at different depths in the measured sample and is also removed when calculating the depth of the sample.
And obtaining the depth information of the sample through Fourier transformation of the signal after the direct current term is removed through filtering.
Where G (z) is the Fourier transformed coherence function of S (k), δ is also a Fourier transformed function, RRIs the reflectance of the reference mirror without the sample.
After the z value is calculated by the above formula, the axial length of the measured sample is obtained by halving the axial coordinate, because the light passes through the back and forth in the sample.
In actual acquisition, the optical probe 41 scans signals circumferentially in a polar coordinate mode, the data acquisition card 22 acquires circumferential depth information of a single circle, and rectangular coordinates are required for processing in order to reconstruct three-dimensional information. The conversion relation between the pixel point (x, y) and the polar coordinate point (rho, theta) is as follows:
and carrying out interpolation calculation on the coordinates of the pixel points with non-integer coordinates in the polar coordinate image by using a bilinear interpolation algorithm to obtain the gray value of the point. The calculation method specifically comprises the following steps:
f(x,y)＝(1-Δρ)(1-Δθ)f([ρ]，[θ])+Δρ(1-Δθ)f([ρ]+1,[θ])+Δθ(1-Δρ)f([ρ],[θ]+1)+ΔρΔθf([ρ]+1,[θ]+1)
s5: three-dimensional reconstruction: three-dimensional reconstruction is performed by a volume rendering method. When the system works, the depth information in the radius direction is collected on the A dimension, and N sampling point data are collected. The rotation of the stepping motor 51 is matched to realize that the circumferential depth information at one circumferential axial position and the A dimension form a two-dimensional data matrix, namely a two-dimensional chromatographic image at the B dimension, and finally the linear motor 52 controls the acquisition of the information in the axial direction to form a three-dimensional volume data set at the C dimension. And (3) performing three-dimensional reconstruction by using a two-dimensional texture mapping method, firstly drawing a two-dimensional matrix sequence, and then loading the two-dimensional texture sequence onto the matrix sequence. And in order to eliminate the problem of two-dimensional texture gray overflow, a ray projection algorithm in volume rendering is adopted for processing. When light passes through the volume data field, voxels in the data field are sampled according to a certain step length, cubic linear interpolation is carried out on sampling points which are not on the voxels during sampling, the sampled data are multiplied by corresponding light transmittance, and the sampling points are accumulated to be regarded as values of pixel points on a view plane.
S6: detection and analysis: the obtained point cloud data of the holes is detected and analyzed, and the point cloud data of the holes can be detected in the aspects of contour, size, appearance, defects and the like.
The method for measuring the surface profile of the inner hole provided by the preferred embodiment of the invention is a scheme with rapidness, high efficiency and high detection precision, and has the characteristics of simple and convenient operation, high resolution and high scanning speed. The following advantages are also provided:
(1) the steps S3-S6 of the invention consider the time sequence relationship, synchronously control each device, finish the real-time acquisition and analysis of the signal, adopt the fast sweep laser light source to cooperate with the spectrum signal of the single-point detection time code, therefore have the fast scanning speed, very high-efficient characteristic.
(2) The invention adopts a precise optical coherence measurement mode, the axial resolution and the transverse resolution of the invention reach the micron level, and the invention has the characteristic of high detection precision. The whole system is packaged into 5 parts as shown in figure 2, the parts are mutually connected by optical fibers, the interference caused by environmental factors is small, and meanwhile, the interference signal contrast is improved, so that the result is clearer, and the system signal-to-noise ratio is higher.
(3) The transverse scanning device adopts a rotary probe form, can go deep into the hole to restore the internal three-dimensional appearance compared with other forms of optical three-dimensional measurement schemes, and perfectly solves the problems of difficult measurement of the surface profile of the inner hole and incomplete measurement data.
In a specific example, the surface profile of the inner hole of the gearbox valve body is measured by using the inner hole surface profile measuring system, and the specific steps comprise:
s1, preparing software and hardware of the system: and starting a computer and a power supply of the sweep frequency light source motion control device, and preparing inner hole surface profile measurement software.
S2, signal test: after the system runs, a zero point test is carried out, a zero point test button is clicked, a signal is sent to control the adjustable optical fiber delay line, a zero-finding level interference wave peak determines the position of a zero optical path so as to determine the coordinates of each later acquisition point relative to the position of the zero optical path, after the zero point is found, a confirmation button is clicked to complete the zero point test, and the software stores the background noise at the position so as to be processed subsequently.
S3, scan control: the manual control probe is aligned with the inlet of the gearbox valve body hole. And clicking a scanning button to start hole scanning, sending a signal to control the linear motor to advance, and driving the optical probe to rotate by the stepping motor. In order to realize real-time synchronous acquisition, the number of sampling points of the actual light source in each trigger period is determined according to the sweep frequency speed of the sweep frequency light source and the sampling frequency of the data acquisition card. And driving the sweep-frequency light source to sweep frequency at the falling edge of the trigger signal of each data acquisition card, and continuously sampling. Considering the rotation and the advance of the probe, the stepping motor is controlled to rotate when the scanning in the depth direction is completed once, and the linear motor is controlled to advance when the scanning in the circumferential direction is completed once. And repeating the steps to complete all circumferential scanning in the axial direction of the inner hole. After the scanning is finished, the reset button is clicked, the optical probe retracts to the entrance, and the motor returns to the initial position.
S4, image processing: the obtained interference signal is firstly filtered to remove a direct current item and an autocorrelation item in the interference signal, namely, a reference signal in a reference arm when no sample exists is collected, the reference signal is subtracted from the interference signal when the sample is tested, depth information in the radius direction of a tested inner hole is obtained through Fourier transform, a probe rotates to scan the signal in a polar coordinate (rho, theta) mode, and a pixel point which is stored in a collection card and is leaked out is subjected to interpolation on the gray value of the point through a bilinear interpolation algorithm. After the scanning is finished, the software automatically stores the two-dimensional chromatographic image obtained by scanning, and the two-dimensional chromatographic image can be checked and edited.
S5, three-dimensional reconstruction: and the software carries out three-dimensional reconstruction according to the two-dimensional image obtained in the last step, and three-dimensional point cloud data are reconstructed by drawing and fitting voxels according to a ray projection algorithm. The point cloud data of the inner hole of the gearbox valve body obtained by software is shown in figure 5.
S6, detection and analysis: the obtained hole point cloud data is imported into detection software for detection and analysis, the size and form and position tolerance of the hole point cloud data are analyzed, the detection result is shown in fig. 6a and 6b, and the obtained hole point cloud data comprises the following geometric parameters: height of the cylinder: 10.707, cylindrical radius: 9.751, standard deviation: 0.026, maximum deviation: 0.049, minimum deviation: 0.026.
the size of the surface profile of the inner hole of the gearbox valve body can be accurately obtained through the detection result, and the problems that the surface profile of the inner hole is difficult to measure and the measured data is incomplete in the prior art are solved.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications can be made without departing from the spirit of the invention, and all the properties or uses are considered to be within the scope of the invention.
Claims (10)
1. A bore surface profile measurement system, comprising:
the device comprises a light path module, a signal acquisition module, an imaging module, a transverse scanning module and a motion control module, wherein the motion control module is connected with the transverse scanning module and used for controlling the transverse scanning module to do rotary motion and/or move along the axial direction of an inner hole of a tested sample, light emitted by the light path module is transmitted to the transverse scanning module, the transverse scanning module converges the light on the surface of the tested sample to form a light spot, and returns the light reflected by the surface of the tested sample to the light path module to generate interference signals through interference in the light path module, and the signal acquisition module is connected with the light path module and the imaging module and used for acquiring the interference signals of the light path module and sending the interference signals to the imaging module.
2. The bore surface profile measurement system of claim 1, wherein the optical path module comprises a swept-frequency optical source and an interferometer, wherein the interferometer comprises a first fiber coupler, a second fiber coupler, a fiber optic circulator, a fiber optic delay line, and a reference mirror.
3. The system for measuring the surface profile of the inner hole according to claim 2, wherein light emitted by the swept-frequency light source enters the first optical fiber coupler and is divided into two paths of light, the first path of light is transmitted to the transverse scanning module after passing through the optical fiber circulator, the transverse scanning module collects light reflected by the surface of the sample to be measured and returns the light to the optical fiber circulator, and the light is transmitted to the second optical fiber coupler as a first part of coupled light; the second path of light sequentially passes through the optical fiber circulator and the optical fiber delay line and then irradiates the reference mirror, the light reflected by the reference mirror returns to the optical fiber circulator, the optical fiber circulator transmits the light to the second optical fiber coupler to serve as a second part of coupled light, and the first part of the coupled light and the second part of the coupled light interfere to generate the interference signal.
4. The bore surface profile measuring system of claim 2, wherein the first fiber coupler is an 80-20 fiber coupler and the second fiber coupler is a 50-50 fiber coupler.
5. The system for measuring the surface profile of an inner bore according to claim 1, wherein the signal acquisition module comprises a balanced amplified photodetector, a data acquisition card and an image acquisition card, the balanced amplified photodetector is used for detecting the interference signal of the light path module, the data acquisition card is used for sampling according to a predetermined frequency, and the image acquisition card is used for converting an electrical signal sampled by the data acquisition card into a digital image.
6. The system for measuring the surface profile of the inner hole as claimed in claim 1, wherein the transverse scanning module comprises an optical probe, the optical probe comprises a Green lens and a right-angle prism, and the light emitted by the light path module passes through the Green lens to be emitted onto the right-angle prism and is reflected to the surface of the measured sample through the right-angle prism.
7. The system according to claim 1, wherein the motion control module comprises a stepping motor, a linear motor and an optical fiber rotary connector, the stepping motor is connected to the transverse scanning module to drive the transverse scanning module to rotate, the linear motor is connected to the stepping motor to drive the stepping motor and the transverse scanning module to move together along the axial direction of the inner hole of the sample to be tested, the optical fiber rotary connector is provided with a fixed end and a rotary end, the fixed end is connected to the output end of the optical path module, and the rotary end is connected to the transverse scanning module.
8. A method of measuring a surface profile of an internal bore, using the system of any one of claims 1 to 7, comprising the steps of:
the optical path module, the motion control module and the signal acquisition module are synchronously controlled according to a time sequence relation, light emitted by the optical path module is transmitted to the transverse scanning module, the transverse scanning module is controlled by the motion control module to make rotary motion and/or axial motion along an inner hole of a measured sample, the transverse scanning module converges the light on the surface of the measured sample to form a light spot and returns the light reflected by the surface of the measured sample to the optical path module, the light path module generates interference signals after receiving the returned light, the signal acquisition module acquires the interference signals and sends the interference signals to the imaging module, and the imaging module images to measure the surface profile of the inner hole.
9. The method for measuring the surface profile of an inner bore according to claim 8, wherein the synchronously controlling the optical path module, the motion control module and the signal acquisition module according to a time sequence relationship specifically comprises:
determining the number of sampling points of the signal acquisition module in each trigger period according to the sweep frequency speed of a light source in the light path module and the sampling frequency of the signal acquisition module, driving the light source to sweep frequency at the lower edge of a trigger signal of each signal acquisition module, and simultaneously driving the signal acquisition module to sample; and when the number of sampling points in the circumferential direction of the inner hole acquired by the signal acquisition module reaches a preset value, controlling the motion control module to start so as to ensure that each circumferential scan is followed by axial motion, and then executing the next circumferential scan until the whole inner hole profile is completely scanned.
10. The bore surface profile measurement method of claim 8, wherein the imaging module imaging to measure the bore surface profile specifically comprises: the imaging module carries out filtering processing on the received interference signal, obtains the depth information of the measured sample through Fourier transformation, and stores the depth information in rectangular coordinates after interpolation processing and coordinate transformation to obtain the measurement information of the surface profile of the inner hole.
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