CN109297434B - Full-depth type curved surface contour measuring device based on optical coherence tomography and control method - Google Patents
Full-depth type curved surface contour measuring device based on optical coherence tomography and control method Download PDFInfo
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Abstract
The invention relates to a full-depth curved surface contour measuring device based on optical coherence tomography, which comprises: the device comprises an SLD light source, a convex lens, a first cylindrical lens, a first spectroscope, a reference lens, a curved surface profile to be tested, a second cylindrical lens, a reflecting mirror, a reflective grating, a cylindrical lens and an area array CCD camera; the point light source emitted by the SLD light source is collimated into a parallel light beam through a convex lens; the parallel light beam is focused into a focal line light beam through a first cylindrical lens, the focal line light beam is divided into two light beams with equal intensity by a first spectroscope, one light beam is reference light and converged on a reference mirror, and the other light beam is detection light and converged on a curved surface profile to be tested; the two light beams are reflected and overlapped to generate interference, the interference light beams are converged into interference spectral lines by a cylindrical lens after being spatially split according to wavelength by a reflection type grating, and two-dimensional interference spectrum fringes are acquired by a CCD camera. The invention can realize high-precision, non-contact and damage-free precise detection of the curved surface contour.
Description
Technical Field
The invention relates to the technical field of optical measurement and imaging, in particular to a full-depth curved surface contour measuring device and a control method based on optical coherence tomography.
Background
The traditional curved surface contour measurement is mostly carried out by a contact type mechanical instrument, and in the occasions with high requirements on precision, high requirements on surface processing quality and non-contact type test, the traditional contact type can not meet the detection requirements. The invention uses two-dimensional frequency domain optical coherence tomography as a detection principle, and aims at the traditional optical coherence tomography to detect interference fringe image contrast difference, DC and background interference exist, and the DC and background interference is removed by adopting a two-step phase shifting method, so that the interference is effectively removed, and the interference fringe contrast is improved. The traditional coherent chromatography detection method has the defects that the detection imaging and the mirror images are overlapped and staggered due to the existence of the complex conjugate mirror image, and cannot effectively and practically image and mirror image respectively. Therefore, on the basis of understanding and researching the existing curved surface contour measuring method, the curved surface contour measuring device and method which are capable of improving the contrast of a two-dimensional spectrum image, effectively removing direct current interference, removing complex conjugate mirror images, high in efficiency, high in precision, non-contact, lossless and high in resolution are designed, and have great engineering significance.
Disclosure of Invention
In view of the above, the invention aims to provide a full-depth type curved surface contour measuring device and a control method based on optical coherence tomography, which realize non-contact measurement of curved surface contour, and have the advantages of high measuring speed and high precision.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a full-depth curved surface profile measurement device based on optical coherence tomography, the device comprising: the device comprises an SLD light source, a convex lens, a first cylindrical lens, a first spectroscope, a reference lens, a curved surface profile to be tested, a second cylindrical lens, a reflecting mirror, a reflective grating, a cylindrical lens and an area array CCD camera; the point light source emitted by the SLD light source is collimated into a parallel light beam through a convex lens; the parallel light beam is focused into a focal line light beam through a first cylindrical lens, the focal line light beam is divided into two light beams with equal intensity by a first spectroscope, one light beam is reference light and converged on a reference mirror, and the other light beam is detection light and converged on a curved surface profile to be tested; the two light beams are reflected and overlapped to generate interference, the interference light beams are converged into interference spectral lines by a cylindrical lens after being spatially split according to wavelength by a reflection type grating, and two-dimensional interference spectrum fringes are acquired by a CCD camera.
Further, an electric displacement platform scanning module is also arranged and comprises an electric linear displacement platform and an adjustable sample mounting rack; the electric linear displacement platform can perform motion control on one axial direction through the controller, and drives the linear scanning displacement platform to move perpendicular to the direction of the detection light beam, so that scanning detection is realized; the adjustable sample mounting rack is used for fixedly mounting the curved surface profile to be tested and can adjust the gesture of the curved surface profile to be tested.
Further, a phase shifter is also arranged; the phase shifter is a piezoelectric ceramic controlled by a programmable direct-current voltage source; the reflecting mirror is arranged on the piezoelectric ceramic, different voltages are input to the piezoelectric ceramic through the programmable direct-current voltage source, and the piezoelectric ceramic is driven to realize nano-scale displacement.
Further, the laser beam splitter also comprises a single-frequency laser source and a second beam splitter; the second beam splitter is arranged between the second lens and the reflecting mirror, and laser emitted by the single-frequency laser source is emitted to a first light inlet of the second beam splitter.
Furthermore, the single-frequency laser light source and the second spectroscope are used for introducing characteristic spectral lines with known wavelengths for the wavelength calibration of the two-dimensional spectrometer system of the whole device.
Further, the two-dimensional interference spectrum fringes of the two-dimensional interference spectrum fringes acquired by the CCD camera are processed by a computer, and surface information of the profile of the curved surface to be detected is obtained.
Further, the control method of the full-depth curved surface contour measuring device based on optical coherence tomography is characterized by comprising the following steps:
s1, adjusting the position and the posture of a curved surface profile to be detected by adjusting an adjustable sample mounting frame to generate an interference signal;
s2, inputting different voltages to the piezoelectric ceramics through a programmable direct-current voltage source, driving the piezoelectric ceramics to realize the displacement of a fixed pitch, and imaging and recording interference fringe images by adopting an area array CCD camera image acquisition module to obtain a plurality of groups of interference spectrums with different phase differences;
s3, transmitting the acquired interference spectrum to a computer to finish two-phase DC removal, and reconstructing a complex two-dimensional interference spectrum signal by a corrected five-step phase shift method;
and S4, processing the stripe signal by adopting image processing software according to the obtained two-dimensional interference spectrum signal to obtain a detection curve of the curved surface profile, and scanning to obtain the curved surface profile information of the whole detection curved surface.
Further, the step S4 specifically includes:
s41, an image processing software module adds a Hanning window function to the light intensity of each row of pixel points of a two-dimensional interference spectrum signal, then carries out fast Fourier transform, corrects peak frequency by adopting an energy concentricity method and accurately extracts the intensity change frequency of each row of pixel points;
and S42, multiplying the intensity change frequency of each row of pixel points by the system distance resolution determined by the self-built spectrometer after wavelength calibration to obtain a detection curve of the curved surface profile, and scanning to obtain the curved surface profile information of the whole detection curve.
Further, a two-step phase shift method is adopted to remove direct current interference in imaging signals, and the method specifically comprises the following steps:
DC term signal I in interference signal r (k,y)| 2 Mutual interference term I s (k,y)| 2 Is not affected by optical path difference, and sequentially collects two-dimensional spectrum signals I in measurement 1 (k, y) and a further two-dimensional spectral signal I obtained after shifting by a phase shifter 2 (k, y) the spectral signal can be expressed as:
I 1 (k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(Δφ 1 (k,y))
⑴
I 2 (k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(Δφ 2 (k,y))
⑵
wherein k is wave number, y is vertical position coordinate of detection point on detection focal line, delta phi 1 (k, y) is the phase angle of the reference light and the sample light at the time of first acquisition, delta phi 2 And (k, y) is the phase angle of the reference light and the sample light during the second acquisition, and the interference signal with direct current and self-coherence removed is obtained by subtracting the formula:
I 3 (k,y)＝2|I r (k,y)||I s (k,y)|cos(Δφ(k,y))
the phase of the interference signal is changed by changing the optical path difference, and the two groups of spectrum signals are subtracted to obtain a two-dimensional interference spectrum only containing the surface position information of the curved surface profile.
Compared with the prior art, the invention has the following beneficial effects:
the device has the advantages of simple light path structure, easy realization, and capability of realizing high-precision, non-contact and damage-free precise detection of the curved surface profile.
Drawings
Fig. 1 is a schematic view of the structure of an apparatus according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of the removed single-frequency laser light source and the second beam splitter device according to the embodiment of the present invention.
FIG. 3 shows a two-dimensional interference fringe generation and two-step phase shift DC removal process for acquiring a two-dimensional spectrum I at zero phase difference in an embodiment of the present invention 1 (k, y), the phase shifter shifts the phase and acquires another two-dimensional spectrum I 2 (k, y) the two spectra are subtracted to obtain a two-dimensional spectral signal with dc and background noise removed.
FIG. 4 shows the contrast of the two-step DC removal process according to the embodiment of the present invention, wherein the contrast of the two-dimensional interference fringe pattern fringe is improved greatly after DC and background noise are removed by comparing the spectrum images, and the DC signal S is obtained after Fourier transform 0 An effective removal is obtained.
FIG. 5 shows a process of reconstructing complex spectrum by five-step phase shift method according to the embodiment of the present invention, wherein the five interference spectrums (I) with fixed phase difference can be obtained by controlling the displacement variation of the characteristics of the piezoelectric ceramics driven by the programmable DC voltage source and introducing a specific optical path difference 1 (k)、I 2 (k)、I 3 (k)、I 4 (k)、I 5 (k) And solving the two-dimensional interference spectrum signals with complex forms obtained by solving the light intensity amplitudes A (k) and the phases phi (k) of different wavelengths of the two-dimensional interference spectrum, and performing Fourier transformation on the reconstructed two-dimensional complex signals to obtain a DC-removed and conjugate mirror imaging diagram.
Fig. 6 is a process of performing fourier transform, spectrum correction processing and scanning on a reconstructed two-dimensional complex signal to obtain an overall curved surface contour in the embodiment of the present invention, performing fourier transform and spectrum correction processing on the reconstructed two-dimensional complex signal to obtain accurate intensity variation frequency value multiplied by ranging resolution to obtain detected curve control position information, and scanning to obtain overall curved surface contour spatial information.
In FIG. 1, 1-SLD light source, 2-convex lens, 3-cylindrical lens, 4-spectroscope 1, 5-reference mirror, 6-phase shifter (piezoceramics), 7-curved profile to be measured, 8-curved profile mounting frame, 9-electric displacement platform, 10-cylindrical lens, 11-single frequency laser light source, 12-spectroscope 2, 13-reflecting mirror, 14-reflecting grating, 15-cylindrical lens, 16-area CCD camera. The 1-SLD light source and the 2-convex lens form a tungsten halogen light source module, the 3-cylindrical lens, the 4-spectroscope 1, the 5-reference mirror and the 6-phase shifter (piezoelectric ceramic) are arranged, the 7-curved surface profile to be tested and the light source form a Michelson interferometer module, and the 13-reflecting mirror, the 14-reflecting grating, the 15-cylindrical lens and the 16-area array CCD camera form a two-dimensional spectrometer module.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples.
Referring to fig. 1, the present invention provides a full-depth curved surface contour measurement device based on optical coherence tomography, which specifically includes: the SLD light source module is used for detecting the curved surface contour, and the divergent SLD point light source is collimated into a parallel light beam through a convex lens;
the Michelson interferometer module comprises a cylindrical lens, a spectroscope and a reference mirror, wherein the cylindrical lens focuses parallel light beams into focal lines, the focal lines generally comprise hundreds to thousands of detection points, the spectroscope divides the light beams into two light beams with equal intensity, one light beam is used as reference light to be converged on the reference mirror, the other light beam is used as detection light to be converged on the surface of a curved surface to be detected, and the two light beams are overlapped after being reflected to generate interference;
the system comprises a reflective grating, a cylindrical lens and an area array CCD camera, wherein interference light beams are converged into interference spectral lines by the cylindrical lens after being spatially split according to wavelengths by the grating, and two-dimensional interference spectrum fringes are acquired by the area CCD camera;
the electric displacement platform scanning module comprises an electric linear displacement platform and an adjustable sample mounting rack, wherein the electric linear displacement platform is a precise servo motor and a screw-nut pair mechanism, a computer can be used for controlling the movement of one axis direction through a controller, and the linear scanning displacement platform is driven to move perpendicular to the direction of a detection light beam, so that the scanning detection is realized, the adjustable sample mounting rack is used for mounting and fixing a sample piece with a detection curved surface, and the gesture of the sample piece with the detection curved surface can be adjusted to generate interference fringes with high contrast;
the phase shifter module is piezoelectric ceramics controlled by a programmable direct-current voltage source, a reflecting mirror is arranged on the piezoelectric ceramics, and different voltages are input to the piezoelectric ceramics through the programmable direct-current voltage source to drive the piezoelectric ceramics to realize nano-scale displacement;
the computer is used for controlling the two-dimensional interference fringe image acquisition and transmission module and the scanning electric displacement platform, and storing and processing fringe image signals transmitted to the computer;
the image processing software module is used for processing the stripe image signals, including filtering, phase shifting, complex signal reconstruction, fast Fourier transformation, spectrum correction and the like, and obtaining the surface information of the contour of the curved surface to be detected.
The laser beam splitter also comprises a single-frequency laser source and a second beam splitter; the second beam splitter is arranged between the second lens and the reflecting mirror, and laser emitted by the single-frequency laser source is emitted to a first light inlet of the second beam splitter; the system uses a single-frequency laser light source as a self-built spectrometer wavelength calibration characteristic light source, the single-frequency laser light source and the second beam splitter are used for introducing characteristic spectral lines with known wavelengths for the whole device two-dimensional spectrometer system wavelength calibration, the self-built two-dimensional spectrometer system wavelength calibration is required to be completed before detection, then the single-frequency laser light source and the second beam splitter can be removed, and the single-frequency laser light source and the second beam splitter are not used in a subsequent detection light path.
At the beginning of detection, the system is required to be calibrated in a vertical coordinate mode to determine the actual length represented by a single pixel point of a camera in the vertical direction in detection.
In an embodiment of the present invention, a control method of a full-depth curved surface contour measurement device based on optical coherence tomography includes the following steps:
A. adjusting a sample mounting frame and an attitude according to the position of the curved surface profile to be detected to generate an interference signal;
B. inputting different voltages to the piezoelectric ceramic through a programmable direct-current voltage source, driving the piezoelectric ceramic to realize the displacement of a fixed pitch, and imaging and recording interference fringe images by adopting an area array CCD camera image acquisition module to obtain five groups of interference spectrums with different phase differences;
C. transmitting the acquired interference fringe image to a computer to complete two-phase DC removal, reconstructing a complex two-dimensional interference spectrum signal by a corrected five-step phase shift method, and processing the fringe signal by adopting an image processing software module;
D. the image processing software module adds a Hanning window function to the light intensity of each row of pixel points of a series of acquired images, then carries out Fast Fourier Transform (FFT), corrects peak frequency by adopting an energy concentricity method, and accurately extracts the intensity change frequency of each row of pixel points;
E. the image processing software module multiplies the intensity change frequency of each row of pixel points by the system distance resolution determined by the self-built spectrometer after wavelength calibration to obtain the detection curve of the curved surface profile, and the curved surface profile information of the whole detection curve can be obtained through scanning.
Further, the full-depth curved surface contour measuring device based on optical coherence tomography is characterized in that: in a full-depth curved surface contour measurement system of two-dimensional optical coherence tomography, a two-dimensional interference pattern acquired by a camera is reference light I r With sample light I s The interference vector addition occurs by the sensitization of the camera sensitization element. Reference light I r Can be expressed as: i r (k,y)＝S r (k)e i2kr Wherein k is the spectral wavenumber, r is the reference optical path, S r (k) Is a spectral power distribution function of the reference light. Sample light I s Can be represented as I s (k,y)＝S s (k)e i2k(r+n*Δz(y))
Wherein S is s (k) N is the refractive index of light in air, and n is the optical path difference between the reference light and the sample light. The two-dimensional interference fringes I (k, y) can be expressed as:
I(k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(Δφ(k,y))
where Δφ (k, y) =4πnΔz (y) k, Δz (y) is the depth change of the curved profile of each point on the detection focal line in the direction of the optical path.
The method comprises the steps of inputting different voltages to piezoelectric ceramics through a programmable direct-current voltage source, driving the piezoelectric ceramics to realize step displacement, obtaining five groups of interference spectrums with different phase differences, reconstructing complex-form spectrum signals by a corrected five-step phase-shifting method so as to remove complex conjugate mirror image signals in imaging signals, realizing full-depth detection, carrying out Fast Fourier Transform (FFT) on the light intensity of each row of pixels of a reconstructed two-dimensional interference fringe I (k, y), extracting the intensity change frequency of each row of pixels, multiplying the system distance resolution determined by a self-built spectrometer after wavelength calibration, and obtaining the curve profile depth change deltaz (y) in the light path direction, namely the full-depth curve profile measurement detection principle.
In one embodiment of the present invention, the DC interference in the imaging signal and the DC term signal I in the interference signal are removed by a two-step phase shift method r (k,y)| 2 Mutual interference term I s (k,y)| 2 Is not affected by optical path difference, and sequentially collects two-dimensional spectrum signals I in measurement 1 (k, y) and a further two-dimensional spectral signal I obtained after shifting by a phase shifter 2 (k, y) the spectral signal can be expressed as:
I 1 (k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(Δφ 1 (k,y)) ⑴
I 2 (k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(Δφ 2 (k,y)) ⑵
wherein k is wave number, y is vertical position coordinate of detection point on detection focal line, delta phi 1 (k, y) is the phase angle of the reference light and the sample light at the time of first acquisition, delta phi 2 And (k, y) is the phase angle of the reference light and the sample light during the second acquisition, and the interference signal with direct current and self-coherence removed is obtained by subtracting the formula:
I 3 (k,y)＝2|I r (k,y)||I s (k,y)|cos(Δφ(k,y))
from the expression, the direct current interference and the autocorrelation noise can be completely removed after subtraction. The method is to change the phase in the interference signal by changing the optical path difference, and to subtract the two groups of spectrum signals to obtain the two-dimensional interference spectrum only containing the surface position information of the curved surface profile.
In an embodiment of the invention, for complex conjugate image interference existing in real fourier transform, an image signal is usually overlapped with an imaging signal and is difficult to effectively distinguish the imaging signal, but conventionally, a curved surface sample to be detected is placed at a positive optical path or a negative optical path part of an optical path, so that half of detection capability and imaging depth of an optical system are wasted, different voltages are input to piezoelectric ceramics through a programmable direct-current voltage source to drive the piezoelectric ceramics to realize step displacement, five sets of interference spectrums with different phase differences are obtained, and a complex form spectrum signal is reconstructed by a modified five-step phase shift method so as to remove the complex conjugate image signal in the imaging signal, thereby realizing full-depth detection.
When the optical path difference between the reference mirror and the curved surface profile to be measured changes, a phase difference can be obtained, the displacement change of the characteristics is realized by controlling the programmable direct current voltage source to drive the piezoelectric ceramics, five interference spectrums with fixed phase difference can be obtained after the specific optical path difference is introduced, and therefore the light intensity and the phase of different wavelengths of the two-dimensional interference spectrums are solved. The light intensity expression is:
wherein I is 0 (k) Is a direct current term signal I r (k,y)| 2 Mutual interference term I s (k,y)| 2 The sum of A (k) is the light intensity of different wavelengths of the two-dimensional interference spectrum, phi (k) is the phase of different wavelengths of the two-dimensional interference spectrum, delta 0 A (k) cos (phi (k) -2 delta for phase-shifted phase difference 0 ) To remove direct current and self-coherent interference signals.
Solving the two-dimensional interference spectrum to obtain light intensities and phases of different wavelengths:
by adding correction factors k/k 0 And obtaining the light intensity and the phase of different wavelengths of the corrected two-dimensional interference spectrum:
thus, a complex two-dimensional interference spectrum signal can be reconstructed.
In an embodiment of the present invention, the image processing software module adds a Hanning window function to the two-dimensional interference spectrum signal reconstructed into complex form, then performs Fast Fourier Transform (FFT), and corrects the peak frequency by using an energy concentricity method, thereby accurately extracting the intensity variation frequency.
The calculation formula of the intensity change frequency of each row of pixel points by the energy gravity center method is as follows:
wherein f i 1 Normalized frequency for the ith frame (i.e., instant i) fringe image, G k For maximum value of discrete spectrum, k represents kth discrete power spectral line, G k+j For the value of the (k+j) th spectral line, z is the number of spectral lines employed for the energy centroid calculation. Stripe density d of the i-th frame (i.e., i time) i And normalized fringe frequency f i 1 The calculation formula is as follows:
d i ＝f i 1 N
where N is the number of pixels of the stripe image in the width direction.
The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (4)
1. A full-depth curved surface contour measurement device based on optical coherence tomography, the device comprising:
the device comprises an SLD light source, a convex lens, a first cylindrical lens, a first spectroscope, a reference lens, a curved surface profile to be tested, a second cylindrical lens, a reflecting mirror, a reflective grating, a cylindrical lens and an area array CCD camera; the point light source emitted by the SLD light source is collimated into a parallel light beam through a convex lens; the parallel light beam is focused into a focal line light beam through a first cylindrical lens, the focal line light beam is divided into two light beams with equal intensity by a first spectroscope, one light beam is reference light and converged on a reference mirror, and the other light beam is detection light and converged on a curved surface profile to be tested; the two beams of light are reflected and overlapped to generate interference, the interference beams are converged into interference spectral lines by a cylindrical lens after being spatially split according to wavelength by a reflection type grating, and two-dimensional interference spectrum fringes are acquired by an area array CCD camera;
the electric displacement platform scanning module is also arranged and comprises an electric linear displacement platform and an adjustable sample mounting rack; the electric linear displacement platform can perform motion control on one axial direction through the controller, and drives the linear scanning displacement platform to move perpendicular to the direction of the detection light beam, so that scanning detection is realized; the adjustable sample mounting rack is used for fixedly mounting the curved surface profile to be tested and can adjust the gesture of the curved surface profile to be tested;
a phase shifter is also arranged; the phase shifter is a piezoelectric ceramic controlled by a programmable direct-current voltage source; the piezoelectric ceramic is provided with a reflecting mirror, different voltages are input to the piezoelectric ceramic through a programmable direct-current voltage source, and the piezoelectric ceramic is driven to realize nano-scale displacement;
the laser beam splitter also comprises a single-frequency laser source and a second beam splitter; the second beam splitter is arranged between the second lens and the reflecting mirror, and laser emitted by the single-frequency laser source is emitted to a first light inlet of the second beam splitter; the single-frequency laser light source and the second beam splitter are used for introducing characteristic spectral lines with known wavelengths for the wavelength calibration of the two-dimensional spectrometer system of the whole device;
and acquiring two-dimensional interference spectrum fringes of the two-dimensional interference spectrum fringes by an area array CCD camera, and processing the two-dimensional interference spectrum fringes by a computer to acquire surface information of the profile of the curved surface to be detected.
2. The control method of a full-depth curved surface contour measuring device based on optical coherence tomography according to claim 1, comprising the steps of:
s1, adjusting the position and the posture of a curved surface profile to be detected by adjusting an adjustable sample mounting frame to generate an interference signal;
s2, inputting different voltages to the piezoelectric ceramics through a programmable direct-current voltage source, driving the piezoelectric ceramics to realize the displacement of a fixed pitch, and imaging and recording interference fringe images by adopting an area array CCD camera image acquisition module to obtain a plurality of groups of interference spectrums with different phase differences;
s3, transmitting the acquired interference spectrum to a computer to finish two-phase DC removal, and reconstructing a complex two-dimensional interference spectrum signal by a corrected five-step phase shift method;
and S4, processing the stripe signal by adopting image processing software according to the obtained two-dimensional interference spectrum signal to obtain a detection curve of the curved surface profile, and scanning to obtain the curved surface profile information of the whole detection curved surface.
3. The control method of the full-depth curved surface contour measuring device based on optical coherence tomography according to claim 2, wherein: the step S4 specifically includes:
s41, an image processing software module adds a Hanning window function to the light intensity of each row of pixel points of a two-dimensional interference spectrum signal, then carries out fast Fourier transform, corrects peak frequency by adopting an energy concentricity method and accurately extracts the intensity change frequency of each row of pixel points;
and S42, multiplying the intensity change frequency of each row of pixel points by the system distance resolution determined by the self-built spectrometer after wavelength calibration to obtain a detection curve of the curved surface profile, and scanning to obtain the curved surface profile information of the whole detection curve.
4. The control method of the full-depth curved surface contour measuring device based on optical coherence tomography according to claim 3, wherein: the direct current interference in the imaging signal is removed by adopting a two-step phase shifting method, and the method is concretely as follows:
DC term signal I in interference signal r (k,y)| 2 Mutual interference term I s (k,y)| 2 Is not affected by optical path difference, and sequentially collects two-dimensional spectrum signals I in measurement 1 (k, y) and a further two-dimensional spectral signal I obtained after shifting by a phase shifter 2 (k, y) the spectral signal can be expressed as:
I 1 (k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(φ 1 (k,y)) ⑴
I 2 (k,y)＝|I r (k,y)| 2 +|I s (k,y)| 2 +2|I r (k,y)||I s (k,y)|cos(φ 2 (k,y)) ⑵
wherein k is wave number, y is vertical position coordinate of detection point on detection focal line, phi 1 (k, y) is the phase angle of the reference light and the sample light at the first acquisition, phi 2 And (k, y) is the phase angle of the reference light and the sample light during the second acquisition, and the interference signal with direct current and self-coherence removed is obtained by subtracting the formula:
I 3 (k,y)＝2|I r (k,y)||I s (k,y)|cos(φ(k,y))
the phase of the interference signal is changed by changing the optical path difference, and the two groups of spectrum signals are subtracted to obtain a two-dimensional interference spectrum only containing the surface position information of the curved surface profile.
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