WO2021164202A1 - 一种双视场光相干断层扫描成像***及材料厚度检测法 - Google Patents

一种双视场光相干断层扫描成像***及材料厚度检测法 Download PDF

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WO2021164202A1
WO2021164202A1 PCT/CN2020/105692 CN2020105692W WO2021164202A1 WO 2021164202 A1 WO2021164202 A1 WO 2021164202A1 CN 2020105692 W CN2020105692 W CN 2020105692W WO 2021164202 A1 WO2021164202 A1 WO 2021164202A1
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sample
light source
thickness
arm
imaging system
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PCT/CN2020/105692
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French (fr)
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莫建华
吴倩
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苏州大学
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
    • G01B11/0675—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating using interferometry

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  • the invention relates to the technical field of material detection, in particular to the technical field of non-transparent material thickness detection, in particular to a dual-field optical coherence tomography imaging system and a non-transparent material thickness detection method.
  • Optical coherence tomography is a low-coherence optical interference imaging technology that can scan and image optical scattering media such as biological tissues, and the obtained image resolution can reach the micron level.
  • OCT has a new type of technical means, which has the advantages of non-contact, non-invasive, non-invasive and high resolution. According to its imaging mechanism, this technology is very suitable for imaging and thickness measurement of multilayer structures. Therefore, OCT has been widely used in medical diagnosis. So far, OCT has been successfully applied to ophthalmology imaging as a routine tool in ophthalmology, and has shown great potential in clinical fields such as dermatology, cardiology, and gastroenterology.
  • OCT In many non-medical fields, OCT has also developed rapidly, especially in non-destructive testing, including non-destructive testing of paper, drug tablet coatings, jade, industrial ceramics, etc. At the same time, due to the micron-level resolution of OCT, it is also of great significance in thickness measurement and has a wide range of application prospects in the medical and industrial fields.
  • OCT In the medical field, OCT is often used to measure the thickness of the fiber layer, fiber cap and cornea.
  • OCT In the industrial field, OCT is often used for thickness measurement of PCBs, metal foils, automotive coatings, pearls, eggshells, etc.
  • Thickness is one of the measurement units of material properties, and its measurement method is also a common content in production and life.
  • the methods of measuring material thickness can be divided into contact measurement and non-contact measurement.
  • the contact measurement method mainly uses tools such as vernier calipers and spiral micrometers.
  • the measuring tool of the contact measurement method directly contacts the material to produce stress, which not only affects the measurement accuracy, but also easily scratches the surface of the material.
  • the non-contact measurement method is mainly carried out by the ultrasonic method and the eddy current method. With the development of optical technology and electronic technology, the accuracy of non-contact measurement methods is getting higher and higher, and it has become the main measurement method in the field of industrial production.
  • the ultrasonic method determines the thickness of the measured material by measuring the wave's reflected echo time in the material.
  • the ultrasonic method determines the thickness of the measured material by measuring the wave's reflected echo time in the material.
  • multiple reflected waves and transmitted waves are generated at the heterogeneous interface.
  • the echoes on the upper and lower surfaces of the medium will be mixed together, making it difficult to distinguish. This makes it difficult for conventional ultrasonic thickness measurement techniques to obtain the necessary parameters such as sound velocity and sound attenuation.
  • the eddy current method uses a certain relationship between the lift-off distance and the coating thickness, and realizes the thickness measurement through the lift-off effect.
  • OCT has better performance in both axial resolution and lateral resolution.
  • OCT is currently only used to measure the thickness of transparent materials.
  • the present invention overcomes the shortcomings of the prior art and provides a method for detecting the thickness of non-transparent materials based on swept optical coherence tomography imaging. It adopts a dual-side view OCT system to further extend the OCT technology to the thickness measurement of opaque materials. Improve the accuracy of measuring the thickness of non-transparent materials.
  • the technical solution adopted by the present invention is: a dual-field optical coherence tomography imaging system, including a scanning imaging system with a data acquisition function, and a swept frequency light source that provides a light source for the scanning imaging system.
  • the scanning imaging system adopts the DSV-OCT system.
  • the DSV-OCT system includes a sample arm and a reference arm that are respectively connected to the sweep light source, and the sweep light source provides the sample arm and the reference arm with a sampling light source or Reference light source; the sample arm is also correspondingly connected with a sample placement platform, the sample placement platform includes a posture adjustment unit for positioning the sample to be tested; the sample arm interferes with the light returned by the reference arm to form an interference signal, the The interference signal is detected by the balanced photodetector and transmitted back to the PC.
  • an optical fiber coupler 1 is arranged between the light source output end of the swept frequency light source and the sample arm and the reference arm.
  • the optical fiber coupler 1 divides the light source into a sampling light source and a reference arm. There are two light sources, and the sampling light source and the reference light source are respectively introduced into the sample arm and the reference arm.
  • the attitude adjustment unit is drivingly connected to the DSV-OCT system; the attitude adjustment unit includes one or more of an X-axis position platform, a Y-axis displacement platform, and a Z-axis displacement platform .
  • a second optical fiber coupler is arranged between the sample arm and the sample placement platform, and the second optical fiber coupler creates two sampling light sources from the sampling light source; the sample to be tested
  • the correction introduction device is arranged opposite to the two sides of the test sample, the correction introduction device includes a collimator one and a focusing lens; the two sampling light sources pass through the correction introduction device on both sides of the sample to be tested. After passing through the focusing lens, the sampling light source is provided on both sides of the sample to be tested to perform double-side imaging.
  • one end of the reference arm corresponds to the optical fiber coupler
  • the other end of the reference arm introduces a reference light source
  • the other end of the reference arm corresponds to the return device, so After the reference light source passes through the return device, the reference light source is input to the balanced photodetector.
  • the return device includes a collimator and a flat mirror that are arranged oppositely; after the reference light source is introduced into the return device, it passes through a set of two collimators and a flat mirror, and then the opposite A set of plane mirrors and a second collimator introduce the reference light source into the balanced photodetector.
  • a method for detecting the thickness of a non-transparent material in a swept optical coherence tomography imaging system :
  • Step one select and calibrate the corresponding detection system, select the DSV-OCT system, and position the sample to be tested on the posture adjustment unit of the sample placement platform;
  • Step 2 Provide a sampling light source to the sample arm through the swept frequency light source and a reference light source to the reference arm; perform data collection on the sample to be tested, and the sampling light source output after the data collection sampling light source passes through the sample to be tested;
  • Step 3 Perform B scan or/and C scan through the sample arm, sampling arm, and posture adjustment unit of the sample placement platform in the DSV-OCT system; collect and process the returned data through the PC;
  • a scan Point measurement of the sample;
  • B scan realize the one-dimensional linear scan of the light spot on the sample surface to obtain the cross-sectional view of the scanning position;
  • C scan realize the scan of the light spot on the two-dimensional area of the sample surface to obtain the three-dimensional structure of the scanning position picture;
  • Step 4 The PC converts the processed data and calculates the thickness of the sample.
  • A-scan point measurement is performed on a sample to obtain interference spectrum signals, and the structure of the sample measurement point along the depth direction can be obtained through signal processing, which is called A-scan.
  • B-scan The sample is moved at a constant speed along the x-direction through the posture adjustment unit, so as to realize a one-dimensional linear scan of the light spot on the sample surface. The acquired data can be processed to obtain a cross-sectional view of the scanning position, which is called This is B scan.
  • C-scan The posture adjustment unit makes the sample move at a constant speed along the x and y directions, so as to realize the scanning of the light spot on the two-dimensional area of the sample surface, and process the acquired data to obtain the three-dimensional structure diagram of the scanning position. This is called C-scan.
  • a method for detecting the thickness of a non-transparent material in a swept optical coherence tomography imaging system In a preferred embodiment of the present invention, a method for detecting the thickness of a non-transparent material in a swept optical coherence tomography imaging system.
  • step 2 after the sample arm creates the output sampling light source into two sampling light sources.
  • the two sampling light sources are introduced symmetrically to the opposite sides of the sample to be tested, and the reference light source returned from the reference arm is three-coupled through the fiber coupler, and then input to the balanced photodetector, interference occurs Signal, and then transmit the interference signal back to the PC.
  • a method for detecting the thickness of non-transparent materials of a dual-field optical coherence tomography imaging system In a preferred embodiment of the present invention, a method for detecting the thickness of non-transparent materials of a dual-field optical coherence tomography imaging system.
  • the thickness measurement is performed by the DSV-OCT system, and the DSV-OCT system uses the opaque material.
  • the thickness of the surface profile is measured, so it is not limited by the imaging depth;
  • the actual thickness can be calculated using the axial gap between the two surface contours in the C scan; if there is a virtual reflective surface with a thickness of 0 on the focal plane, the reflective surface displayed by two independent sampling beams will be in B There are two different depth positions in the scan, and the depths are defined as z af and z bf respectively ; if there is no sample to be measured, there is a bright horizontal line in the B scan because of the unidirectional light between the two sampling optical elements Pass, it is defined as the reference plane z rp ; the relationship between these three depths is as follows:
  • the focal plane is slightly deviated from the middle plane of the material, so the left and right surfaces will have some offsets, and the depths are z rs and z ls respectively ; the thickness can be calculated according to the following formula:
  • px represents the pixel size in the axial direction.
  • a method for detecting the thickness of a non-transparent material of a dual-field optical coherence tomography imaging system in step 4:
  • the focal plane is inside the material, but slightly deviated from the middle plane of the material, so the left and right surfaces will have some offset.
  • the left and right surfaces are on the same side of the reference plane, and the depths are z rs and z ls respectively ; according to the following formula Calculate the thickness:
  • px represents the pixel size in the axial direction
  • Method 2 The common situation of sample placement is that the focal plane is not inside the material, and the two surfaces are on different sides of the reference depth; the thickness is calculated according to the following formula:
  • the present invention solves the defects existing in the background technology, and the beneficial effects of the present invention are as follows:
  • the invention provides a new feasible and effective method for measuring the thickness of opaque materials with a dual-field optical coherence tomography imaging system.
  • a dual-field optical coherence tomography imaging system By evaluating the performance of DSV-OCT on glass slides and comparing it with traditional optical OCT, the results show that DSV-OCT maintains the imaging capabilities of OCT and has good thickness measurement capabilities for opaque materials.
  • the scheme designed by the present invention is also suitable for spectral domain optical coherence tomography imaging system.
  • this method has the following advantages: 1.
  • the method proposed in the present invention is non-contact and will not damage the surface of the material. 2. Realize objective measurement through optical imaging, which can reduce the influence of human subjective factors.
  • this method Compared with the existing non-contact measurement methods, this method has the following advantages: 1.
  • the method is non-invasive and can detect the thickness of non-transparent materials non-destructively. 2. Higher measurement accuracy. 3. Not affected by the surface roughness of the material itself.
  • Figure 1 is a schematic diagram of the DSV-OCT system
  • FIG. 2 Two-sided sampling scheme: (a) The virtual reflection plane with zero thickness is located at the focal point to obtain the reference plane; (b) and (c) are the focal planes located inside and outside the sample with thickness d, respectively.
  • the z rs line and z ls line respectively represent the left and right contours of the opaque sample, and the dashed line is the position of the reference plane.
  • Figs. 3(a) to (c) are actual B-scan images of non-transparent materials corresponding to Figs. 2(a) to (c), respectively.
  • Figure 4 (a) B-scan with DSV-OCT focal plane inside the glass slide; (b) B-scan with DSV-OCT focal plane outside the glass slide.
  • the z ls_a and z rs_a lines represent the imaging of the left surface and the right surface of the glass slide by the left sampling beam, respectively, and the z rs_b and z ls_b lines represent the imaging of the right surface and the left surface of the glass slide by the right sampling beam, respectively.
  • the L line is not used in the actual measurement. It is the signal detected after the light goes from the left beam to the right beam, or the signal is detected after the light goes from the right beam to the left beam. The two signals overlap. of.
  • Thickness C curve measured with a micrometer and thickness measured with DSV-OCT focus is on the A curve inside the sample and B curve outside the sample, and the difference between the thickness measured with a micrometer and the thickness measured by DSV-OCT (AC Curve and BC curve);
  • Figure 6 The histogram and Gaussian fitting curve of the difference in the thickness of the slide glass
  • Figure 7 (a) 3D surface profile with the focus inside the opaque material, with an area of 4mm ⁇ 4mm; (b) the OCT cross-sectional image corresponding to the area marked by the dashed line in (a);
  • Figure 8 corresponds to the top and bottom surface profile of Figure 7 (b); (b) the thickness curve calculated based on the surface profile;
  • Figure 9 Thickness structure diagram of opaque material, the focal plane is inside the opaque material
  • Figure 10 (a) Use DSV-OCT to image ten-layer frosted belt; (b) Image of ten-layer frosted belt after image fusion;
  • 1-PC machine 2-balanced photodetector, 3-fiber coupler one, 6-fiber coupler two, 7-fiber coupler three, 51-collimator one, 52-collimator two, 4 -Plane mirror, 8-focus lens, 9- sample to be tested.
  • this embodiment discloses a dual-field optical coherence tomography imaging system for achieving the above purpose, including a scanning imaging system with data acquisition function, and a swept frequency light source that provides a light source for the scanning imaging system ,
  • the scanning imaging system adopts the DSV-OCT system.
  • the DSV-OCT system includes a sample arm and a reference arm that are respectively connected to the sweep light source.
  • the sweep light source provides the sample arm and the reference arm with a sampling light source or a reference light source; the sample arm There is also a sample placement platform correspondingly connected.
  • the sample placement platform includes a posture adjustment unit for positioning the sample 9; the light returned by the sample arm and the reference arm interferes to form an interference signal.
  • the interference signal is detected by the balanced photodetector 2 and transmitted back to the PC.
  • Machine 1 is also a posture adjustment unit for positioning the sample 9; the light returned by the sample arm and the reference arm interferes to form an interference signal.
  • the interference signal is detected by the balanced photodet
  • the sample placement platform is also provided with a posture adjustment unit for placing the sample 9 to be tested.
  • the posture adjustment unit includes an X-axis electric displacement platform, a Y-axis electric displacement platform, and a Z-axis manual platform connected to the detection system.
  • the sample placement platform is connected to the DSV-OCT system drive.
  • the X-axis electric displacement platform, Y-axis electric displacement platform, and Z-axis manual stage of the sample placement platform cooperate with the sample arm and reference arm in the DSV-OCT system to create two symmetrical sampling beams to achieve dual sides Imaging lays the foundation for thickness measurement of non-transparent materials.
  • the light source output end of the swept frequency light source is provided with an optical fiber coupler 3, which divides the light source into a sampling light source and a reference light source, and the sampling light source and the reference light source are respectively introduced into the sample arm And reference arm.
  • the frequency sweep light source is preferably a frequency sweep laser light source.
  • the frequency sweep laser light source uses a center wavelength of 1310 nanometers and a wavelength range of 1249.4 nanometers to 1359.6 nanometers. As shown in Figure 1.
  • the light emitted by the swept frequency laser light source is divided into two beams through a 50:50 fiber coupler, of which 50% enters the sample arm as a sampling light source, and 50% enters the reference arm as a reference light source.
  • the calibration introduction device is arranged opposite to the two sides of the sample 9 to be tested.
  • the calibration introduction device includes a collimator 51 and a focusing lens 8; the sample arm and the sample placement platform are provided with a fiber coupling at the corresponding end
  • the second 6 and the second fiber coupler 6 create the sampling light source into two sampling light sources; both of the two sampling light sources pass through the collimator 51 in the correction introduction device on both sides of the sample 9 to be tested, and then pass through the focusing lens 8.
  • Sampling light sources are provided on both sides of the sample 9 to be tested.
  • Fiber Coupler Two 6 uses a 1 ⁇ 2 fiber coupler to create two sampling beams. Two sets of the same collimator 51 and focusing lens 8 are placed symmetrically on both sides of the sample 9 to be tested.
  • one end of the reference arm corresponds to the fiber coupler one 3
  • one end of the reference arm introduces the reference light source
  • the other end of the reference arm corresponds to the return device
  • the reference light source is input into the reference light source after passing through the calibration device Balance photodetector 2.
  • the return device includes a second collimator 52 and a flat mirror 4 that are arranged oppositely; after the reference light source is introduced into the return device, it passes through a set of two collimators 52 and a flat mirror 4, and then a set of flat mirrors 4 and a second collimator 4 opposite to each other. 52 Introduce the reference light source into the balanced photodetector 2.
  • the sample arm uses the output sampling light source as the sampling light source after passing through the sample 9 to be tested, and the reference light source output by the reference arm, the backscattered light reflected by the sample arm and the reference arm respectively passes through the optical fiber Coupler three 7, the 50/50 optical fiber coupler interferes, and the interference signal is transmitted by the balanced photodetector 2 by using a pair of vertically placed electric translation stages to fix the sample to realize the sample scanning, and then transmit it back to the PC 1.
  • the output sampling light source as the sampling light source after passing through the sample 9 to be tested
  • the reference light source output by the reference arm the backscattered light reflected by the sample arm and the reference arm respectively passes through the optical fiber Coupler three 7, the 50/50 optical fiber coupler interferes
  • the interference signal is transmitted by the balanced photodetector 2 by using a pair of vertically placed electric translation stages to fix the sample to realize the sample scanning, and then transmit it back to the PC 1.
  • a method for detecting the thickness of non-transparent materials of a dual-field optical coherence tomography imaging system a method for detecting the thickness of non-transparent materials of a dual-field optical coherence tomography imaging system
  • Step one select and calibrate the corresponding detection system, select the DSV-OCT system, and position the sample 9 to be tested on the posture adjustment unit of the sample placement platform;
  • Step 2 Sweep the frequency light source to provide the sample arm with a sampling light source and the reference arm with a reference light source; perform data collection on the sample 9 to be tested, and the data collection sample light source passes through the sample 9 to be tested and then outputs the sample light source;
  • Step 3 A scan or/and B scan or/and C scan are performed through the sample arm, sampling arm, and posture adjustment unit of the sample placement platform in the DSV-OCT system; B scan and C scan are preferred in the present invention. Collect and process the returned data through the PC 1;
  • Step 4 The PC 1 converts the processed data and calculates the thickness of the sample.
  • A-scan point measurement is performed on a sample to obtain interference spectrum signals, and the structure of the sample measurement point along the depth direction can be obtained through signal processing, which is called A-scan.
  • B-scan The sample is moved at a constant speed along the x-direction through the posture adjustment unit, so as to realize a one-dimensional linear scan of the light spot on the sample surface. The acquired data can be processed to obtain a cross-sectional view of the scanning position, which is called This is B scan.
  • C-scan The posture adjustment unit makes the sample move at a constant speed along the x and y directions, so as to realize the scanning of the light spot on the two-dimensional area of the sample surface, and process the acquired data to obtain the three-dimensional structure diagram of the scanning position. This is called C-scan.
  • a method for detecting the thickness of a non-transparent material in a swept optical coherence tomography imaging system In a preferred embodiment of the present invention, a method for detecting the thickness of a non-transparent material in a swept optical coherence tomography imaging system.
  • step 2 after the sample arm creates the output sampling light source into two sampling light sources.
  • the two sampling light sources are introduced symmetrically into the opposite sides of the sample 9 to be tested, they are coupled with the reference light source returned by the reference arm through the fiber coupler 37, and then input to the balanced photodetector 2 to generate The interference generates an interference signal, and then the interference signal is transmitted back to the PC 1.
  • a method for detecting the thickness of non-transparent materials of a dual-field optical coherence tomography imaging system In a preferred embodiment of the present invention, a method for detecting the thickness of non-transparent materials of a dual-field optical coherence tomography imaging system.
  • the thickness measurement is performed by the DSV-OCT system, and the DSV-OCT system uses the opaque material.
  • the thickness of the surface profile is measured, so it is not limited by the imaging depth;
  • the actual thickness can be calculated using the axial gap between the two surface contours in the C scan; if there is a virtual reflective surface with a thickness of 0 on the focal plane, the reflective surface displayed by two independent sampling beams will be in B There are two different depth positions in the scan, and the depths are defined as z af and z bf respectively ; if there is no sample to be measured, there is a bright horizontal line in the B scan because of the unidirectional light between the two sampling optical elements Pass, it is defined as the reference plane z rp ; the relationship between these three depths is as follows:
  • the focal plane is slightly deviated from the middle plane of the material, so the left and right surfaces will have some offsets, and the depths are z rs and z ls respectively ; the thickness can be calculated according to the following formula:
  • px represents the pixel size in the axial direction.
  • a method for detecting the thickness of a non-transparent material of a swept optical coherence tomography imaging system in step four:
  • the focal plane is inside the material, but slightly deviated from the middle plane of the material, so the left and right surfaces will have some offset.
  • the left and right surfaces are on the same side of the reference plane, and the depths are z rs and z ls respectively ; according to the following formula Calculate the thickness:
  • px represents the pixel size in the axial direction
  • Method 2 The common situation of sample placement is that the focal plane is not inside the material, and the two surfaces are on different sides of the reference depth; the thickness is calculated according to the following formula:
  • B-scan and C-scan are performed in cooperation with the sample arm in the DSV-OCT system and the posture adjustment unit of the sample placement platform through the PC 1, and data acquisition and processing are realized.
  • the PC 1 uses the external k clock provided by the laser source as the sampling clock to perform analog-to-digital conversion of the signal output by the balanced detector through the data acquisition card set up in the PC 1, and the obtained interference spectrum signal is evenly distributed in the wave number space at equal intervals and stored in Computer memory, used for subsequent Fourier transform calculations.
  • the data acquisition program is built on the LabVIEW platform to collect data and control the movement of the electric translation stage to realize B-scan and C-scan.
  • Data processing is mainly through spectral shaping, Fourier transform and removal of fixed pattern noise on the detected interference signal, thereby converting the interference signal into a signal in the depth domain of the sample.
  • FIG. 2 illustrates the mechanism of the DSV-OCT system for thickness measurement.
  • the DSV-OCT system measures thickness through the surface profile of opaque materials, so it is not limited by the imaging depth.
  • the actual thickness can be calculated using the axial gap between the two surface profiles in the same C-scan.
  • the reflective surface displayed by two independent sampling beams will be located at two different depths in the B-scan, and the depths are defined as z af and z bf respectively ; if there is no sample to be measured, then There is a bright horizontal line in the B-scan. This is due to the unidirectional passage of light between the two sampling optical elements, which is defined as the reference plane z rp ; the relationship between these three depths is as follows:
  • a material with a thickness of d is placed between the two focusing lenses 8.
  • the sample can be placed in two ways.
  • Figure 2(b) shows that the focal plane is inside the material, but it is slightly deviated from the middle plane of the material, so the left and right surfaces will have some offset.
  • the left and right surfaces are on the same side of the reference plane, and the depths are z rs and z ls respectively .
  • the thickness can be calculated according to the following formula:
  • px represents the pixel size in the axial direction
  • the reference plane passes through without placing any sample, the beam starts from one side of the sample arm and is received by the other side and is finally detected.
  • the depth position of the signal on the OCT image is used as the reference plane, as shown in Figure 3(a).
  • Figure 3 (b) and (c) are B-scans of the silica gel model collected using the DSV-OCT system, corresponding to the two situations described in Figure 2 (b) and (c). Obviously, only very shallow depth areas can be imaged from both sides of the sample 9 to be tested. Therefore, each sampled beam produces only one surface profile in a single B-scan. Moreover, the depth distribution of the two surfaces imaged in the B-scan is consistent with the theoretical prediction in Figure 2. It is worth mentioning that in the experiment, due to the inherent characteristics of the electric translation stage, the movement of the sample driven by it has a process from acceleration, uniform speed to deceleration. Since the data collected during acceleration and deceleration is not uniform, each B-scan only retains the data of the same uniform speed process.
  • the accuracy of the DSV-OCT system in the thickness measurement of the present invention uses a transparent glass slide with a thickness of about 1 mm as a sample, and compares the thickness measured using the DSV-OCT system and a micrometer.
  • Figure 4 (a) and Figure 4 (b) are the images of DSV-OCT on the glass slide.
  • the reference plane here is the same as in Figure 3 (a).
  • both sampling beams image the entire depth of the slide, which can explain the existence of four surfaces in the B scan of the DSV-OCT slide.
  • there is a bright horizontal line which is due to the unidirectional transmission of light between the two sampled optical elements.
  • Figure 4 shows the thickness calculated from (a) to (b) and the thickness obtained by averaging ten times of micrometer measurements as shown in Figure 5.
  • the internal thickness of the focal plane measured by DSV-OCT (1.01mm ⁇ 1.18 ⁇ m) and the external thickness (1.01mm ⁇ 1.14 ⁇ m) are basically the same as the average thickness measured by the micrometer (1.01mm ⁇ 1.6 ⁇ m).
  • the thickness difference curve in Figure 5 can make the difference more intuitive. It can be clearly seen from Figure 5 that the inconsistency of the two methods is close to zero in the full range of 3mm.
  • the histogram in Figure 6 illustrates the statistical data of the measurement error in Figure 5, and the A curve is a Gaussian fit of the thickness difference histogram.
  • the thickness difference between the DSV-OCT system and the micrometer ranges from -5.8 to 6.08 ⁇ m, the average difference is 0.4 ⁇ m, the standard deviation is 1.18 ⁇ m, and the FWHM of the Gaussian curve is 2.2 ⁇ m.
  • the difference range is -6.88 ⁇ 5 ⁇ m
  • the average difference is -0.28 ⁇ m
  • the standard deviation is 1.14 ⁇ m
  • the FWHM of the Gaussian curve is 2.2 ⁇ m.
  • the DSV-OCT system has the ability to generate a two-dimensional thickness map.
  • a 4mm square area was scanned with the DSV-OCT system, and the scanned original 3D image is shown in Figure 7 (a).
  • FIG. 7(b) is an example of a cross-sectional image at the dotted rectangle frame in FIG. 7(a).
  • mean filtering is used to further reduce noise.
  • Figure 8 (a) plots the contours of the two surfaces, and the material thickness calculated using formula (4) is shown in Figure 8 (b). There are some slight fluctuations in the thickness, indicating that the surface roughness of the material is not very good.
  • Figure 10 (a) is an image of a 10-layer frosted belt generated by DSV-OCT.
  • the two sample arms have a good signal-to-noise ratio, but neither can image more than the first 4 to 5 layers.
  • Figure 10 (b) by selecting the region of interest from the generated image and then fusing, the ten-layer image of the entire matte tape can be clearly seen, as shown in Figure 10 (b).
  • the results show that the developed DSV-OCT system maintains the imaging capabilities of OCT and can provide thickness measurement of opaque materials, and the DSV-OCT system can also overcome the limitations of penetration depth and focus depth to achieve thick and weak scattering materials Full-depth imaging.

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  • Length Measuring Devices By Optical Means (AREA)

Abstract

本发明涉及一种双视场光相干断层扫描成像***及材料厚度检测法，扫频光学相干断层扫描成像***包括扫描成像***，以及给扫描成像***提供光源的扫频光源，扫描成像***采用DSV-OCT***，DSV-OCT***包括分别与扫频光源对应衔接的样品臂和参考臂，扫频光源分别给所述样品臂和参考臂提供采样光源或参考光源；样品臂还对应有样品放置平台，样品放置平台包括定位待测样品的姿态调整单元；样品臂与参考臂返回的光发生干涉形成干涉信号，干涉信号由平衡光电探测器检测并回传给PC机。本发明提供了一种双侧视图OCT***，将OCT技术进一步扩展到了不透明材料的厚度测量，提高了测量非透明材料厚度的精度。

Description

一种双视场光相干断层扫描成像***及材料厚度检测法 技术领域
本发明涉及材料检测技术领域，具体涉及一种非透明材料厚度检测技术领域，尤其涉及一种双视场光相干断层扫描成像***及非透明材料厚度检测法。
背景技术
光学相干断层扫描成像(Optical Coherence Tomography,OCT)是一种低相干光学干涉成像技术，可以对光学散射介质如生物组织等进行扫描成像,获得的图像分辨率可以达到微米级。OCT有着新型技术手段，具有非接触、非侵入、无损伤和分辨率高等优点。根据其成像机理，该技术非常适合多层结构的成像和厚度测量，因此，OCT在医学诊断上得到了广泛应用。迄今为止，OCT已作为眼科常规工具成功地应用于眼科影像学，并且在皮肤病学，心脏病学，肠胃病学等临床领域也显示出了巨大的潜力。在许多非医学领域，OCT也得到了快速的发展，尤其是在无损检测中，包括纸张、药物片剂包衣、玉石、工业陶瓷等的无损检测。同时，由于OCT的微米级分辨率，其在厚度测量方面也具有重要意义，在医学和工业领域中有着广泛的应用前景。在医学领域，OCT常用于对纤维层，纤维帽和角膜的厚度进行测量。在工业领域，OCT常用于PCB、金属箔片、汽车涂料、珍珠、蛋壳等的厚度测量。
在其他领域，也有很多测量材料厚度的方法。厚度作为材料属性的衡量单位之一，其测量方法也是生产生活中较为常见的内容。当前，测量材料厚度的方法可以分为接触式测量和非接触式测量。接触式测量方法主要采用游标卡尺、螺旋测微计等工具。但是，接触式测量方法的量具直接接触材料产生应力，不但影响测量精度，而且容易划伤材料表面。非接触式测量方法则主要通过超声法和涡流法来进行。随着光学技术和电子技术的 发展，非接触测量方法的精度越来越高，现已成为工业生产领域的主要测量方法。超声法通过测量波在材料中的反射回波时间来确定被测材料的厚度。然而，当超声波入射到多层介质上时，在异质界面处产生多个反射波和透射波。当材料的厚度薄时，会造成介质上下表面的回波混叠在一起，不易分辨。这使得常规超声测厚技术难以得到测量所必须的声速、声衰减等参数。涡流法式利用提离距离与涂层厚度之间一定的关系，通过提离效应实现对厚度的测量。然而，涡流法受材料表面粗糙度的影响很大，必须去除材料表面和探头之间的附着物质，以消除由于粗糙表面引起的***误差和偶然误差。因此，开发一种具有较强鲁棒性和较高精度的材料厚度测量方法是十分必要的。与这些方法相比，OCT在轴向分辨率和横向分辨率上均具有更好的性能。但是由于有限的成像深度，目前OCT只用于测量透明材料的厚度。
发明内容
本发明克服了现有技术的不足，提供一种基于扫频光学相干断层扫描成像的非透明材料厚度检测法，采用一种双侧视图OCT***，将OCT技术进一步扩展到了不透明材料的厚度测量，提高了测量非透明材料厚度的精度。
为达到上述目的，本发明采用的技术方案为：一种双视场光相干断层扫描成像***，包括带有数据采集功能的扫描成像***，以及给扫描成像***提供光源的扫频光源，所述扫描成像***采用DSV-OCT***，所述DSV-OCT***包括分别与所述扫频光源对应衔接的样品臂和参考臂，所述扫频光源分别给所述样品臂和参考臂提供采样光源或参考光源；所述样品臂还对应衔接有样品放置平台，所述样品放置平台包括定位待测样品的姿态调整单元；所述样品臂与所述参考臂返回的光发生干涉形成干涉信号，所述干涉信号 由平衡光电探测器检测并回传给PC机。
本发明一个较佳的实施例中，扫频光源的光源输出端与所述样品臂与所述参考臂之间设置有光纤耦合器一，所述光纤耦合器一将光源分为采样光源和参考光源两束，所述采样光源和参考光源分别引入所述样品臂和参考臂。
本发明一个较佳的实施例中，姿态调整单元与所述DSV-OCT***驱动连接；所述姿态调整单元包括X轴位平台、Y轴位移平台、Z轴位移平台中的一种或多种。
本发明一个较佳的实施例中，所述样品臂与所述样品放置平台之间设置有光纤耦合器二，所述光纤耦合器二将采样光源创建成两束采样光源；所述待测样品的两侧相对设置的校正引入装置，所述校正引入装置包括准直仪一和聚焦透镜；所述两束采样光源均通过所述待测样品两侧的校正引入装置中的准直仪一，再经过聚焦透镜后，给所述待测样品两侧提供所述采样光源，进行双侧面成像。
本发明一个较佳的实施例中，参考臂的一端与所述光纤耦合器一对应，所述参考臂的另一端引入参考光源，所述参考臂的另一端与所述回传装置对应，所述参考光源经过回传装置后将参考光源输入所述平衡光电探测器。
本发明一个较佳的实施例中，回传装置包括相对设置的一对准直仪和平面镜；所述参考光源引入所述回传装置后经过一组准直仪二和平面镜，再由相对的一组平面镜和准直仪二将所述参考光源引入所述平衡光电探测器。
本发明一个较佳的实施例中，一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法：
步骤一，选择并校准对应的检测***，选用DSV-OCT***，将待测样品定位放置在样品放置平台的姿态调整单元上；
步骤二，通过扫频光源给样品臂提供采样光源，给参考臂提供参考光源；对待测样品进行数据采集，数据采集采样光源穿过待测样品后输出的采样光源；
步骤三，通过DSV-OCT***中的样品臂、采样臂，以及样品放置平台的姿态调整单元配合进行B扫描或/和C扫描；通过PC机将回传的数据进行采集和处理；A扫描：对样品进行点测量；B扫描：实现光点在样品表面的一维线性扫描，获得扫描位置的横截面图；C扫描：实现光点在样品表面的二维区域扫描，获得扫描位置的三维结构图；
步骤四，PC机将处理的数据进行转化，计算样品厚度。
具体的，A扫描：对样品进行点测量，获取得到干涉光谱信号，通过信号处理可获得该样品测量点沿着深度方向的结构，这称之为A扫描。B扫描：通过姿态调整单元使得样品沿着x方向作匀速运动，从而实现光点在样品表面的一维线性扫描，对获取得到的数据进行处理，即可获得扫描位置的横截面图，这称之为B扫描。C扫描：通过姿态调整单元使得样品沿着x和y方向作匀速运动，从而实现光点在样品表面的二维区域扫描，对获取得到的数据进行处理，即可获得扫描位置的三维结构图，这称之为C扫描。
本发明一个较佳的实施例中，一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法，步骤二中，所述样品臂将输出的采样光源创建成两束采样光源后，分别将两束采样光源对称引入所述待测样品的相对两侧后，与所述参考臂返回的参考光源分别通过光纤耦合器三耦合后，再输入所述平衡光电探测器，发生干涉产生干涉信号，再将所述干涉信号回传给PC机。
本发明一个较佳的实施例中，一种双视场光相干断层扫描成像***的非透明材料厚度检测的方法，步骤四中，通过DSV-OCT***进行厚度测量，DSV-OCT***通过不透明材料的表面轮廓进行厚度测量，因此不受成像深度的限制；
实际厚度可以使用C扫描中两个表面轮廓之间的轴向间隙来计算；设在焦平面上存在一个厚度为0的虚拟反射面，则通过两个独立的采样光束显示的反射面将在B扫描中位于两个不同深度位置，深度分别定义为z af和z bf；若没有测量样品，则在B扫描中存在一条明亮的水平线，这是因为两个采样光学元件之间的光的单向通过，它被定义为参考平面z rp；这三个深度之间的关系如下式：
Figure PCTCN2020105692-appb-000001
焦平面与材料的中间平面略有偏离，因此左右表面会有一些偏移，深度分别为z rs和z ls；可以根据以下公式计算厚度：
d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
其中，px代表轴向的像素大小。
本发明一个较佳的实施例中，一种双视场光相干断层扫描成像***的非透明材料厚度检测的方法，步骤四中：
将厚度为d的材料放置在两个聚焦透镜之间，此时样品的放置会有两种方式；
方式一，焦平面在材料的内部，但与材料的中间平面略有偏离，因此左右表面会有一些偏移，左右表面都位于参考平面同一侧，深度分别为z rs和z ls；根据以下公式计算厚度：
d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
其中，px代表轴向的像素大小；
方式二，样品放置的常见情况是焦平面不在材料内部，两个表面位于参考深度的不同侧；根据以下公式计算厚度：
d＝[(z bf-z rs)-(z ls-z af)]×px；公式(3)
公式(2)和(3)可以重新表述为相同的形式
Figure PCTCN2020105692-appb-000002
本发明解决了背景技术中存在的缺陷，本发明的有益效果：
本发明提供了一种新的具有可行性和有效性的用一种双视场光相干断层扫描成像***进行不透明材料厚度测量的方法。通过对DSV-OCT在载玻片上的性能进行了测评，并与传统光学OCT进行了比较，结果表明DSV-OCT保持了OCT的成像能力，对不透明材料具有良好的厚度测量能力。本发明所设计的方案也适用于谱域光学相干断层扫描成像***。
相比于现有的接触式测量方法，该方法有如下几点优势：1、本发明提出的方法是非接触式的，不会损伤材料表面。2、通过光学成像实现客观测量，可以减少人为主观因素的影响。
与现有非接触式的测量方法比较，该方法有如下几点优势：1、该方法是非侵入式的，能无损地检测出非透明材料的厚度。2、测量精度更高。3、不受材料本身表面粗糙度的影响。
附图说明
下面结合附图和实施例对本发明进一步说明。
图1是DSV-OCT***原理图；
图2双侧采样方案：(a)厚度为零的虚拟反射平面位于焦点处得到参考平面；(b)和(c)分别为焦平面位于厚度为d的样品内部和外部。z rs线和z ls线分别表示不透明样本的左右轮廓，虚线是参考平面位置。
图3(a)～(c)分别是对应于图2(a)～(c)的对非透明材料的实际B扫描图像。
图4(a)DSV-OCT焦平面在载玻片内部的B扫描；(b)DSV-OCT焦平面在载玻片外部的B扫描。z ls_a和z rs_a线分别表示左侧采样光束对载玻片的左表面和右表面的成像，z rs_b和z ls_b线分别表示右侧采样光束对载玻片的右表面和左表面的成像,L线在实际测量中没有用到，它是光从左侧光束到右侧光束后被探测到的信号，或者是光从右侧光束到左侧光束后被探测到的信号，两个信号重合的。
图5用千分尺测得的厚度C曲线和用DSV-OCT测得的厚度(焦点在样品内部A曲线和样品外部B曲线，以及用千分尺测得的厚度与DSV-OCT测得的厚度差异(A-C曲线和B-C曲线)；
图6载玻片厚度差异的直方图和高斯拟合曲线；
图7(a)焦点位于不透明材料内部的3D表面轮廓图，面积为4mm×4mm；(b)对应于(a)中虚线标记区域的OCT横截面图像；
图8(a)对应于图7(b)的上下表面轮廓图；(b)根据表面轮廓计算出的厚度曲线；
图9不透明材料的厚度结构图，焦平面在不透明材料内部；
图10(a)用DSV-OCT对十层磨砂带进行成像；(b)图像融合后的十层磨砂带图像；
其中，1-PC机,2-平衡光电探测器,3-光纤耦合器一,6-光纤耦合器二,7-光纤 耦合器三,51-准直仪一,52-准直仪二,4-平面镜,8-聚焦透镜,9-待测样品。
具体实施方式
为了本技术领域的人员更好的理解本发明专利，下面结合附图和实施例对本发明作进一步详细描述。
以下所描述的实施例仅仅是本发明一部分实施例，并不是全部的实施例；基于本发明中的实施例，本领域的普通技术人员在没有做出创造性劳动前提下所获得的其他所用实施例，都属于本发明的保护范围。
如图1所示，本实施例公开了为达到上述目的，一种双视场光相干断层扫描成像***，包括带有数据采集功能的扫描成像***，以及给扫描成像***提供光源的扫频光源，扫描成像***采用DSV-OCT***，DSV-OCT***包括分别与扫频光源对应衔接的样品臂和参考臂，扫频光源分别给所述样品臂和参考臂提供采样光源或参考光源；样品臂还对应衔接有样品放置平台，样品放置平台包括定位待测样品9的姿态调整单元；样品臂与参考臂返回的光发生干涉形成干涉信号，干涉信号由平衡光电探测器2检测并回传给PC机1。
具体的，样品放置平台上还设置有用于放置待测样品9的姿态调整单元，姿态调整单元包括与检测***连接的X轴电动位移平台，Y轴电动位移平台，以及Z轴手动平台。样品放置平台上与DSV-OCT***驱动连接。通过样品放置平台的X轴电动位移平台，Y轴电动位移平台，以及Z轴手动平台与DSV-OCT***中的样品臂和参考臂配合，通过创建两束对称的采样光束，实现了双侧面成像，为非透明材料厚度测量打下基础。
本发明一个较佳实施例中，扫频光源的光源输出端设置有光纤耦合器一3，光纤耦合器一3将光源分为采样光源和参考光源两束，采样光源和参考光源分别引入样品臂和参考臂。扫频光源优选扫频激光光源，扫频激光光 源采用中心波长为1310纳米，波长范围为1249.4纳米到1359.6纳米。如图1所示。扫频激光光源发出的光通过50:50光纤耦合器被分成两束，其中50％作为采样光源进入样品臂，50％作为参考光源进入参考臂。
本发明一个较佳实施例中，待测样品9的两侧相对设置的校正引入装置，校正引入装置包括准直仪一51和聚焦透镜8；样品臂与样品放置平台对应的一端设置有光纤耦合器二6，光纤耦合器二6将采样光源创建成两束采样光源；两束采样光源均通过待测样品9两侧的校正引入装置中的准直仪一51，再经过聚焦透镜8后，给待测样品9两侧提供采样光源。光纤耦合器二6使用1×2光纤耦合器创建两个采样光束。两组相同的准直仪一51和聚焦透镜8在待测样品9的两侧对称放置。
本发明一个较佳实施例中，参考臂的一端与光纤耦合器一3对应，参考臂的一端引入参考光源，参考臂的另一端与回传装置对应，参考光源经过校准装置后将参考光源输入平衡光电探测器2。回传装置包括相对设置的一对准直仪二52和平面镜4；参考光源引入回传装置后经过一组准直仪二52和平面镜4，再由相对的一组平面镜4和准直仪二52将参考光源引入平衡光电探测器2。
本发明一个较佳实施例中，样品臂将输出的采样光源经过待测样品9后作为采样光源，与参考臂输出的参考光源，经由样品臂和参考臂反射回来的背向散射光分别通过光纤耦合器三7，型号为50/50的光纤耦合器发生干涉，并且干涉信号由平衡光电探测器2通过使用一对垂直放置的电动平移台固定样品以实现样品扫描，回传给PC机1，从而提供B扫描和C扫描。
本发明一个较佳实施例中，一种双视场光相干断层扫描成像***的非透明材料厚度检测的方法，
步骤一，选择并校准对应的检测***，选用DSV-OCT***，将待测样品9 定位放置在样品放置平台的姿态调整单元上；
步骤二，通过扫频光源给样品臂提供采样光源，给参考臂提供参考光源；对待测样品9进行数据采集，数据采集采样光源穿过待测样品9后输出的采样光源；
步骤三，通过DSV-OCT***中的样品臂、采样臂，以及样品放置平台的姿态调整单元配合进行A扫描或/和B扫描或/和C扫描；本发明优选B扫描和C扫描。通过PC机1将回传的数据进行采集和处理；
步骤四，PC机1将处理的数据进行转化，计算样品厚度。
具体的，A扫描：对样品进行点测量，获取得到干涉光谱信号，通过信号处理可获得该样品测量点沿着深度方向的结构，这称之为A扫描。B扫描：通过姿态调整单元使得样品沿着x方向作匀速运动，从而实现光点在样品表面的一维线性扫描，对获取得到的数据进行处理，即可获得扫描位置的横截面图，这称之为B扫描。C扫描：通过姿态调整单元使得样品沿着x和y方向作匀速运动，从而实现光点在样品表面的二维区域扫描，对获取得到的数据进行处理，即可获得扫描位置的三维结构图，这称之为C扫描。
本发明一个较佳的实施例中，一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法，步骤二中，所述样品臂将输出的采样光源创建成两束采样光源后，分别将两束采样光源对称引入所述待测样品9的相对两侧后，与所述参考臂返回的参考光源分别通过光纤耦合器三7耦合后，再输入所述平衡光电探测器2，发生干涉产生干涉信号，再将所述干涉信号回传给PC机1。
本发明一个较佳的实施例中，一种双视场光相干断层扫描成像***的非透明材料厚度检测的方法，步骤四中，通过DSV-OCT***进行厚度测量，DSV-OCT***通过不透明材料的表面轮廓进行厚度测量，因此不受成像深度的限 制；
实际厚度可以使用C扫描中两个表面轮廓之间的轴向间隙来计算；设在焦平面上存在一个厚度为0的虚拟反射面，则通过两个独立的采样光束显示的反射面将在B扫描中位于两个不同深度位置，深度分别定义为z af和z bf；若没有测量样品，则在B扫描中存在一条明亮的水平线，这是因为两个采样光学元件之间的光的单向通过，它被定义为参考平面z rp；这三个深度之间的关系如下式：
Figure PCTCN2020105692-appb-000003
焦平面与材料的中间平面略有偏离，因此左右表面会有一些偏移，深度分别为z rs和z ls；可以根据以下公式计算厚度：
d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
其中，px代表轴向的像素大小。
本发明一个较佳的实施例中，一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法，步骤四中：
将厚度为d的材料放置在两个聚焦透镜8之间，此时样品的放置会有两种方式；
方式一，焦平面在材料的内部，但与材料的中间平面略有偏离，因此左右表面会有一些偏移，左右表面都位于参考平面同一侧，深度分别为z rs和z ls；根据以下公式计算厚度：
d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
其中，px代表轴向的像素大小；
方式二，样品放置的常见情况是焦平面不在材料内部，两个表面位于参考 深度的不同侧；根据以下公式计算厚度：
d＝[(z bf-z rs)-(z ls-z af)]×px；公式(3)
公式(2)和(3)可以重新表述为相同的形式
Figure PCTCN2020105692-appb-000004
实施例一
通过PC机1与DSV-OCT***中的样品臂，以及样品放置平台的姿态调整单元配合进行B扫描和C扫描，并实现数据采集与处理。PC机1中通过设置的数据采集卡以激光源提供的外部k时钟作为采样时钟将平衡探测器输出的信号进行模数转换，所获得的干涉光谱信号在波数空间等间隔均匀分布，并存入电脑内存，用于后续的傅立叶变换计算。数据采集程序建立在LabVIEW平台上，用来采集数据和控制电动平移台的移动，实现B扫描和C扫描。数据处理主要是通过对探测到的干涉信号进行光谱整形、傅立叶变换和去除固定模式噪声，从而把干涉信号转变成样品深度域的信号。
具体的，厚度计算。图2说明了DSV-OCT***进行厚度测量的机制。DSV-OCT***通过不透明材料的表面轮廓进行厚度测量，因此不受成像深度的限制。实际厚度可以使用同一C扫描中两个表面轮廓之间的轴向间隙来计算。如图2中(a)图所示，通过两个独立的采样光束显示的反射面将在B扫描中位于两个不同深度位置，深度分别定义为z af和z bf；若没有测量样品，则在B扫描中存在一条明亮的水平线，这是因为两个采样光学元件之间的光的单向通过，它被定义为参考平面z rp；这三个深度之间的关系如下式：
Figure PCTCN2020105692-appb-000005
然后，将厚度为d的材料放置在两个聚焦透镜8之间，此时样品的放置会有两种方式。图2(b)为焦平面在材料的内部，但与材料的中间平面略有偏离，因此左右表面会有一些偏移。左右表面都位于参考平面同一侧，深度分别为z rs和z ls。最后，可以根据以下公式计算厚度：
d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
其中，px代表轴向的像素大小；
另一种样品放置的常见情况是焦平面不在材料内部，两个表面位于参考深度的不同侧，如图2(c)所示，根据以下公式计算厚度：
d＝[(z bf-z rs)-(z ls-z af)]×px；公式(3)
公式(2)和(3)可以重新表述为相同的形式
Figure PCTCN2020105692-appb-000006
在实验中，参考平面通过不放置任何样品的情况下，光束从样品臂中一侧出发由另一侧接收并最终被探测得到。该信号在OCT图像上的深度位置作为参考平面，如图3(a)所示。
图3(b)和(c)为使用DSV-OCT***采集的硅胶模型的B扫描，对应于图2中(b)、(c)描述的两种情况。显然，从待测样品9的两侧只能成像非常浅的深度区域。因此，每个采样光束在单次B扫描中仅会产生一个表面轮廓。而且，两个表面在B扫描中成像的深度分布与图2中的理论预测一致。值得一提的是，在实验中由于电动平移台固有的特性，其驱动的样品运动具有从加速、匀速再到减速的过程。由于在加速和减速过程中收集的数据不均匀，因此每次B扫描 仅保留相同匀速过程的数据。
本发明中DSV-OCT***在厚度测量中的准确性，使用厚度约1mm的透明载玻片作为样品，并比较使用DSV-OCT***和千分尺测量的厚度。图4中(a)图和图4中(b)图为DSV-OCT对载玻片所成的图像。此处的参考平面与图3中(a)图一致。同时，两个采样光束都对载玻片的整个深度成像，这就可以解释DSV-OCT的载玻片B扫描中存在四个表面。另外，在DSV-OCT***成像中，存在一条明亮的水平线，这是由于光在两个采样的光学元件之间单向传递形成的。
根据先前讨论的厚度理论计算载玻片的光学厚度。图4中(a)图～(b)图计算得出的厚度以及千分尺十次测量取平均得到的厚度如图5所示。总的来说,DSV-OCT测量焦平面在内部的厚度(1.01mm±1.18μm)和在外部的厚度(1.01mm±1.14μm)与千分尺测量的平均厚度(1.01mm±1.6μm)基本一致。但是仍然存在一些细微的差异，通过图5中的厚度差异曲线可以使差异更加直观。从图5中可以清楚地看到，在3mm的全范围内，两种方法的不一致性接近于零。图6中的直方图说明了图5中测量误差的统计数据，A曲线是厚度差直方图的高斯拟合。焦平面在载玻片内部时，DSV-OCT***与千分尺之间的厚度差范围为-5.8～6.08μm，平均差异为0.4μm，标准差为1.18μm，高斯曲线的FWHM为2.2μm。焦平面在载玻片外部时，差异范围为-6.88～5μm，平均差异为-0.28μm，标准差为1.14μm，高斯曲线的FWHM为2.2μm。最后,假定每个测量的真实值在±ε的范围内概率是95％，定义ε为绝对精度，我们通过计算ε从而量化DSV-OCT的性能。从图6中可以看出DSV-OCT计算出的绝对精度结果大约为3μm。
实施例二
在实施例一的基础上，DSV-OCT***生成二维厚度图的能力。定制一个刻有圆形壁(内径：2mm，外径：3mm，高度：0.3mm)的1英寸不透明圆盘作为样品。用DSV-OCT***扫描了一个4mm的方形区域，扫描的原始3D图像如图7中(a) 图所示。从三维图形可以清楚地看到两个表面的整体轮廓。图7中(b)图为图7中(a)图中虚线矩形框处的截面图像的示例。在计算厚度之前，用均值滤波以进一步降低噪声。图8中(a)图绘制了两个表面的轮廓，使用公式(4)计算出的材料厚度如图8中(b)图所示。厚度存在一些微小的波动，表明材料表面粗糙度不是很好。
此外，DSV-OCT***增加成像深度方面的潜力。图10中(a)图为DSV-OCT生成的10层磨砂带图像。两个样品臂具有良好的信噪比，但都不能成像超过前4～5层。相比之下，通过将生成的图像选取感兴趣区域再进行融合，整个磨砂胶带的十层图像都可以清晰可见，如图10中(b)图。
总的来说，结果表明开发的DSV-OCT***保持了OCT的成像能力并可以提供不透明材料的厚度测量，并且DSV-OCT***还可以克服穿透深度和聚焦深度的限制，实现厚弱散射材料的全深度成像。
以上依据本发明的理想实施例为启示，通过上述的说明内容，相关人员完全可以在不偏离本项发明技术思想的范围内，进行多样的变更以及修改。本项发明的技术性范围并不局限于说明书上的内容，必须要根据权利要求范围来确定技术性范围。

Claims (10)

  1. 一种双视场光相干断层扫描成像***，包括带有数据采集功能的扫描成像***，以及给扫描成像***提供光源的扫频光源，其特征在于：所述扫描成像***采用DSV-OCT***，所述DSV-OCT***包括分别与所述扫频光源对应衔接的样品臂和参考臂，所述扫频光源分别给所述样品臂和参考臂提供采样光源或参考光源；所述样品臂还对应衔接有样品放置平台，所述样品放置平台包括定位待测样品的姿态调整单元；所述样品臂与所述参考臂返回的光发生干涉形成干涉信号，所述干涉信号由平衡光电探测器检测并回传给PC机。
  2. 根据权利要求1所述的一种双视场光相干断层扫描成像***，其特征在于：所述扫频光源的光源输出端与所述样品臂与所述参考臂之间设置有光纤耦合器一，所述光纤耦合器一将光源分为采样光源和参考光源两束，所述采样光源和参考光源分别引入所述样品臂和参考臂。
  3. 根据权利要求2所述的扫频光学相干断层扫描成像***，其特征在于：所述姿态调整单元与所述DSV-OCT***驱动连接；所述姿态调整单元包括X轴位平台、Y轴位移平台、Z轴位移平台中的一种或多种。
  4. 根据权利要求3所述的一种双视场光相干断层扫描成像***，其特征在于：
    所述样品臂与所述样品放置平台之间设置有光纤耦合器二，所述光纤耦合器二将采样光源创建成两束采样光源；
    所述待测样品的两侧相对设置的校正引入装置，所述校正引入装置包括准直仪一和聚焦透镜；
    所述两束采样光源均通过所述待测样品两侧的校正引入装置中的准直仪一，再经过聚焦透镜后，给所述待测样品两侧提供所述采样光源，进行双侧面成像。
  5. 根据权利要求4中所述的一种双视场光相干断层扫描成像***，其特征在于：所述参考臂的一端与所述光纤耦合器一对应，所述参考臂的另一端引入参考光源，所述参考臂的另一端与所述回传装置对应，所述参考光源经过回传装置后将参考光源输入所述平衡光电探测器。
  6. 根据权利要求5中所述的一种双视场光相干断层扫描成像***，其特征在于：所述回传装置包括相对设置的一对准直仪和平面镜；所述参考光源引入所述回传装置后经过一组准直仪二和平面镜，再由相对的一组平面镜和准直仪二将所述参考光源引入所述平衡光电探测器。
  7. 采用上述权利要求1～6中任一权利要求所述的一种双视场光相干断层扫描成像***的非透明材料厚度检测的方法，其特征在于：
    步骤一，选择并校准对应的检测***，选用DSV-OCT***，将待测样品定位放置在样品放置平台的姿态调整单元上；
    步骤二，通过扫频光源给样品臂提供采样光源，给参考臂提供参考光源；对待测样品进行数据采集，数据采集采样光源穿过待测样品后输出的采样光源；
    步骤三，通过DSV-OCT***中的样品臂、采样臂，以及样品放置平台的姿态调整单元配合进行A扫描或/和B扫描或/和C扫描；通过PC机将回传的数据进行采集和处理；A扫描：对样品进行点测量；B扫描：实现光点在样品表面的一维线性扫描，获得扫描位置的横截面图；C扫描：实现光点在样品表面的二维区域扫描，获得扫描位置的三维结构图；
    步骤四，PC机将处理的数据进行转化，计算样品厚度。
  8. 根据权利要求5中所述的一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法，其特征在于：步骤二中，所述样品臂将输出的采样光源创建成两束采样光源后，分别将两束采样光源对称引入所述待测样品的 相对两侧后，与所述参考臂返回的参考光源分别通过光纤耦合器三耦合后，再输入所述平衡光电探测器，发生干涉产生干涉信号，再将所述干涉信号回传给PC机。
  9. 根据权利要求7中所述的一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法，其特征在于：步骤三中，通过DSV-OCT***进行厚度测量，DSV-OCT***通过不透明材料的表面轮廓进行厚度测量，因此不受成像深度的限制；
    实际厚度可以使用C扫描中两个表面轮廓之间的轴向间隙来计算；设在焦平面上存在一个厚度为0的虚拟反射面，则通过两个独立的采样光束显示的反射面将在B扫描中位于两个不同深度位置，深度分别定义为z af和z bf；若没有测量样品，则在B扫描中存在一条明亮的水平线，这是因为两个采样光学元件之间的光的单向通过，它被定义为参考平面z rp；这三个深度之间的关系如下式：
    Figure PCTCN2020105692-appb-100001
    焦平面与材料的中间平面略有偏离，因此左右表面会有一些偏移，深度分别为z rs和z ls；可以根据以下公式计算厚度：
    d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
    其中，px代表轴向的像素大小。
  10. 根据权利要求9中所述的一种扫频光学相干断层扫描成像***的非透明材料厚度检测的方法，其特征在于：
    将厚度为d的材料放置在两个聚焦透镜之间，此时样品的放置会有两种方式；
    方式一，焦平面在材料的内部，但与材料的中间平面略有偏离，因此左右 表面会有一些偏移，左右表面都位于参考平面同一侧，深度分别为z rs和z ls；根据以下公式计算厚度：
    d＝[(z bf-z rs)+(z af-z ls)]×px；公式(2)
    其中，px代表轴向的像素大小；
    方式二，样品放置的常见情况是焦平面不在材料内部，两个表面位于参考深度的不同侧；根据以下公式计算厚度：
    d＝[(z bf-z rs)-(z ls-z af)]×px；公式(3)
    公式(2)和(3)可以重新表述为相同的形式
    Figure PCTCN2020105692-appb-100002
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