CN113984715A - Coherence tomography device and method - Google Patents
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Abstract
The disclosure provides a coherent tomography device and a coherent tomography method, and relates to the technical field of optics. The coherence tomography apparatus includes: the light source component consists of a wide-spectrum light source device, a chromatic dispersion device and a digital micromirror, wherein light rays emitted by the wide-spectrum light source device sequentially pass through the chromatic dispersion device and the digital micromirror, and the light source component provides light source output for the coherence tomography device; the interference assembly is arranged at a light ray outlet of the light source assembly, and light rays emitted by the light source assembly are split and interfered in the interference assembly; and the photoelectric detection assembly is arranged at the interference light ray outlet of the interference assembly and is used for acquiring the light intensity distribution of the interference light rays. The light source component in the coherence tomography device provided by the disclosure is composed of a wide-spectrum light source device, a dispersion device and a digital micro-mirror, and the light source with tunable frequency can be rapidly output by special light path integration of the three devices, so that the cost of the coherence tomography device is reduced, and the output speed of the light source is increased.
Description
Technical Field
The present disclosure relates to the field of optical technologies, and in particular, to a coherent tomography apparatus and method.
Background
Coherence Tomography (OCT) is an emerging Optical imaging technique, which uses interference information obtained after interference between scattered light irradiated on a sample and reference light in a light path to quickly obtain structural distribution of the sample in depth, thereby implementing non-invasive tomographic measurement of different depth levels of the sample. At present, OCT technology is divided into two major categories, namely time domain OCT and frequency domain OCT, wherein the frequency domain OCT is more and more emphasized in the fields of biomedical imaging and industrial imaging due to the characteristics of higher scanning speed, high signal to noise ratio and the like.
The frequency-sweep OCT in the frequency domain OCT can directly use the imaging camera to directly image the chromatographic surface without a spectrometer, so that the requirement of in-plane scanning can be reduced, the imaging speed is higher than that of other OCT methods, and the frequency-sweep OCT has huge development and application prospects. In the frequency-swept OCT, a light source capable of quickly tuning the light frequency is the core part of the frequency-swept OCT, and the light source used in the conventional frequency-swept OCT is a tunable laser which is expensive, complex in technology and limited in light source output speed, so that the price of the frequency-swept OCT equipment is greatly increased, and the development of the frequency-swept OCT equipment is limited to a certain extent.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
It is an object of the present disclosure to overcome the above-mentioned deficiencies of the prior art and to provide a coherence tomography apparatus and method.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, or in part will be obvious from the description, or may be learned by practice of the disclosure.
According to an aspect of the present disclosure, there is provided a coherent tomography apparatus, the apparatus including: the light source assembly comprises a wide-spectrum light source device, a dispersion device and a digital micromirror, wherein light rays emitted by the wide-spectrum light source device sequentially pass through the dispersion device and the digital micromirror, and the light source assembly provides light source output for the coherence tomography device;
the interference assembly is arranged at a light ray outlet of the light source assembly, and light rays emitted by the light source assembly are subjected to light splitting and interference in the interference assembly;
the photoelectric detection assembly is arranged at an interference light ray outlet of the interference assembly, and the light ray detection assembly is used for acquiring the light intensity distribution of the interference light ray.
In some embodiments of the present disclosure, based on the foregoing, the light source module further comprises a plurality of optical focusing elements disposed between the wide-spectrum light source element, the dispersive element, and the digital micromirror.
In some embodiments of the present disclosure, based on the foregoing, the optical focusing element is a focusing lens or a reflective focusing optic.
In some embodiments of the present disclosure, based on the foregoing scheme, the light source module has a light source output mode of light waveguide output or spatial light output.
In some embodiments of the present disclosure, based on the foregoing, the light source module further includes a light splitting element, and the light splitting element is configured to split light emitted from the wide-spectrum light source element.
In some embodiments of the present disclosure, based on the foregoing solution, the wavelength of the light source emitted by the wide-spectrum light source device is greater than or equal to 10nm, and the central wavelength of the light source emitted by the wide-spectrum light source device is in the range of 300-2500 nm.
In some embodiments of the present disclosure, based on the foregoing solution, the output optical power of the wide-spectrum light source device is greater than or equal to 0.1 mW.
According to another aspect of the present disclosure, there is provided a coherence tomography method, the method including: starting a light source assembly, wherein parallel light rays emitted by the light source assembly enter an interference assembly, and the parallel light rays are divided into a first light beam and a second light beam by a light splitting element in the interference assembly;
the first light beam irradiates on a preset sample and is reflected by the sample to form a first reflected light beam, and the second light beam irradiates on a reflecting element in the interference assembly and is reflected by the reflecting element to form a second reflected light beam;
the first reflected light beam and the second reflected light beam return to the light splitting element along an original optical path and interfere in the light splitting element to form an interference light beam;
the interference light beam enters the photoelectric detection assembly, and two-dimensional light intensity distribution of the sample is formed in the photoelectric detection assembly.
In some embodiments of the present disclosure, based on the foregoing scheme, after forming the two-dimensional light intensity distribution of the sample in the photodetection assembly, the method includes:
and analyzing, calculating and constructing a three-dimensional structural image of the sample according to the two-dimensional light intensity distribution of the sample and the distribution of light rays at different wavelengths.
In some embodiments of the present disclosure, based on the foregoing scheme, the constructing the three-dimensional structure image of the sample further comprises:
the method comprises the steps of obtaining calibration parameters of a preset calibration sample and three-dimensional structure image parameters of the sample, processing the calibration parameters and the three-dimensional structure image parameters of the sample, and reconstructing the three-dimensional structure image parameters of the sample to obtain a real three-dimensional structure image of the sample.
The disclosure provides a coherent tomography device, which can obtain three-dimensional structure imaging of a sample through the combination of a light source component, an interference component and a photoelectric detection component in the device, and has good imaging effect; the light source component in the device consists of a wide-spectrum light source device, a dispersion device and a digital micromirror, and a light source emitted by the light source component can replace the existing tunable laser to emit a light source with fast tunable light frequency, so that the production cost of the device is reduced, and the light frequency scanning speed of the light source is improved;
another aspect of the present disclosure provides a coherent tomography method, in which a light source assembly in a coherent tomography apparatus emits a light source with a fast tunable light frequency, and an interference assembly and a photodetection assembly are used in cooperation, so that a three-dimensional structural image of a sample can be obtained, and the method has a good imaging effect and a fast imaging speed.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.
Fig. 1 is a schematic structural diagram of a swept-frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Fig. 2 is a schematic view of a light source assembly in an exemplary embodiment of the present disclosure.
Fig. 3 is another schematic view of a light source assembly in an exemplary embodiment of the present disclosure.
Fig. 4 is a schematic structural diagram of a global imaging-based swept frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Fig. 5 is a schematic structural diagram of a line scanning-based swept frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Fig. 6 is another structural diagram of a line-scan-based swept-frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Fig. 7 is a schematic structural diagram of a point scanning-based swept frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Fig. 8 is a flow chart of a method of coherent tomography in an exemplary embodiment of the present disclosure.
Fig. 9 is a second structural diagram of a swept frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Fig. 10 is a schematic diagram of a third structure of a swept-frequency OCT apparatus in an exemplary embodiment of the present disclosure.
Wherein the reference numerals are as follows:
1: a light source assembly; 2: an interference component; 3: a photodetection component;
10: a wide-spectrum light source device; 11: a dispersive device; 12: a digital micromirror;
13: a light source output end; 141: a first optical focusing element;
142: a second optical focusing element; 143: a third optical focusing element;
15: a light-splitting element; 21: a light-splitting device; 22: a reflective element; 23: a sample;
24: an optical focusing element in the interference assembly; 25: an optical scanning element;
31: a photodetector; 32: an imaging optical lens group;
33: an optical focusing element in the photodetection assembly;
101: a superluminescent diode; 102: a fiber optic circulator; 103: focusing lens 1
104: a reflective grating; 201: a light splitting cube; 202: a flat plate mirror;
302: a telecentric lens; 100: port number 100; 200: port number 200;
300: port number 300; 1011: a light emitting diode; 1021: a plano-convex lens;
1031: a cylindrical mirror; 1041: a dispersive prism; 2021: a second focusing lens;
2031: a microscope objective; 2041: a flat plate beam splitter; 2051: a mirror.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted. Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale.
Although relative terms, such as "upper" and "lower," may be used in this specification to describe one element of an icon relative to another, these terms are used in this specification for convenience only, e.g., in accordance with the orientation of the examples described in the figures. It will be appreciated that if the device of the icon were turned upside down, the element described as "upper" would become the element "lower". When a structure is "on" another structure, it may mean that the structure is integrally formed with the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure via another structure.
The terms "a," "an," "the," "said," and "at least one" are used to indicate the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first," "second," and "third," etc. are used merely as labels, and are not limiting on the number of their objects.
In an actual optical path configuration of coherence tomography, a weak coherent light source is generally used as light source output, the light source is split by using a light splitting device, and one path of light is used as a reference optical path and irradiates a reference reflector to be used as a reference arm; the other path of light irradiates on a measurement sample and is reflected by reflecting surfaces at different depths or different positions of the sample to be used as a signal arm, the light reflected by the signal arm is combined with the light reflected by the reference arm at the light splitting device and is optically interfered, and due to the weak coherence characteristic of the light, only when the light reflected by the sample through the signal arm and the light reflected by the reference arm travel the same optical path, the interference signals of the two beams of light are strongest, so that the signals at different depths of the sample can be obtained by adjusting the position of a reflector of the reference arm, and the signals are collected through a photoelectric detector and are processed through an analytical algorithm, so that the depth chromatographic image of the sample can be obtained.
In frequency-domain OCT, a mirror of a reference arm is always kept still, and a tomographic image of a sample in depth is obtained by analyzing coherent information of an incident light source in frequency, while frequency-sweep OCT is one of frequency-domain OCT, which obtains spectral interference by rapidly scanning the frequency of incident light using a high-speed frequency tunable light source and a photodetector and obtaining intensity information of light at different frequencies by the photodetector, and finally calculates a depth tomographic signal. Compared with frequency spectrum OCT in frequency domain OCT, frequency sweep OCT has faster imaging speed and better signal-to-noise ratio, and frequency sweep OCT can directly use imaging camera to carry out the formation of chromatographic plane, does not need to use a spectrometer, reduces the number of times of in-plane scanning, and improves the imaging speed, but the tunable laser generally used by the light source of the existing frequency sweep OCT is expensive in price and complex in technology, therefore, a light source assembly capable of rapidly realizing wavelength scanning function and providing tunable light frequency is needed, so that the high-precision and high-speed sample three-dimensional signal acquisition of a coherence tomography device is realized.
The disclosed embodiments provide a coherence tomography apparatus, as shown in fig. 1, including: light source assembly 1, interference assembly 2 and photoelectric detection assembly 3.
Fig. 2 is a schematic structural diagram of a light source assembly in an exemplary embodiment of the present disclosure, and with reference to fig. 1 and fig. 2, the light source assembly 1 is composed of a wide-spectrum light source device 10, a chromatic dispersion device 11, and a digital micromirror 12, light emitted from the wide-spectrum light source device 10 passes through the chromatic dispersion device 11 and the digital micromirror 12 in sequence, the light source assembly 1 provides light source output for a coherence tomography apparatus, and light emitted from the light source assembly 1 can be output by a light source output end 13.
The digital micromirror is an optical switch, which utilizes a rotating reflector to realize the opening and closing of the optical switch, light is emitted from an optical fiber and then is emitted to a reflecting lens of the digital micromirror, when the digital micromirror is opened, photoetching enters the optical fiber at the other end through a symmetrical light path, when the digital micromirror is closed, namely the reflector of the digital micromirror generates a small rotation, and after the light is reflected, the light cannot enter the symmetrical other end, so that the effect of closing the optical switch is achieved.
In fig. 2, the wide-spectrum light source device 10, the dispersion device 11, and the digital micromirror 12 are arranged in order in spatial position, and a first optical focusing element 141 is arranged between the wide-spectrum light source device 10 and the dispersion device 11, a second optical focusing element 142 is arranged between the dispersion device 11 and the digital micromirror 12, and a third optical focusing element 143 is arranged between the digital micromirror 12 and the light source output end 13.
The light of the light source module is transmitted through the following processes: the light output by the wide-spectrum light source device 10 is focused by the first optical focusing element 141 to convert the output light of the wide-spectrum light source device 10 into focused light, and is focused on the dispersion device 11, and is split by the dispersion device 11 to split the focused light, so that the light with different frequencies is split at the transmission angle after being split by the dispersion device 11, the light with split frequencies is guided to the digital micromirror 12 by the second optical focusing element 142, and the digital micromirror 12 controls the switches at different positions thereof to reflect the light with the wavelength corresponding to the starting position to the third optical focusing element 143 by the digital micromirror 12, and the light passing through the third optical focusing element 143 is focused into the light source output end 13 to be output.
Fig. 3 is another schematic structural diagram of a light source module according to an exemplary embodiment of the present disclosure, as shown in fig. 3, in combination with fig. 3 and fig. 1, the light source module 1 further includes a light splitting element 15, and the light splitting element 15 is configured to split light reflected by the digital micromirror 12 and returned in a reverse direction along an original light path, so that the light is transmitted to the light source output end 13.
In fig. 3, the wide-spectrum light source device 10, the dispersion device 11, and the digital micromirror 12 are arranged in order in spatial position, and the light splitting element 15 and the first optical focusing element 141 are arranged between the wide-spectrum light source device 10 and the dispersion device 11, and the second optical focusing element 142 is arranged between the dispersion device 11 and the digital micromirror 12.
In such a light source module, the transmission of light is as follows: the light output by the wide-spectrum light source device 10 is guided to the first optical focusing element 141 through the light splitting element 15, the first optical focusing element 141 converts the output light into focused light and converges the focused light on the dispersion device 11, the light passing through the dispersion device 11 is separated from the transmission angle according to different frequencies and then guided to different positions of the digital micromirror 12 through the second optical focusing element 142, the light with different wavelengths is reflected to the second optical focusing element 142 by different positions on the digital micromirror 12 under the control action of the digital micromirror 12, and then the light with different wavelengths returns to the light splitting element 15 after passing through the dispersion device 11 and the first optical focusing element 141 and is guided to the light source output end 13 under the reflection action of the light splitting element 15.
The light source output mode of the light source assembly 1 is optical waveguide output or spatial light output, the light source output mode specifically can be output after optical fiber collimation or parallel spatial light output, if the light source output end 13 of the light source assembly disclosed herein is output after optical fiber collimation, the light source output end 13 is a combination form of the third optical focusing element 143 and the optical fiber, if the light source output end 13 of the light source assembly disclosed herein is parallel spatial light output, the light source output end 13 may not include the third optical focusing element 143, the specific light source output form and the composition of the light source output end can make specific adjustment according to actual use requirements, wherein the output mode after optical fiber collimation can use a single-mode optical fiber, a multimode optical fiber or an optical fiber bundle, which is not specifically limited in the present disclosure.
The wavelength of a light source emitted by the wide-spectrum light source device in the disclosure is greater than or equal to 10nm, and the output light power of the wide-spectrum light source device is greater than or equal to 0.1 mW.
It should be noted that the wide-spectrum light source device of the present disclosure may be a high-power LED (light-emitting diode), a super-continuum laser, and a super-light-emitting diode, which are collimated by a lens, but the present disclosure is not limited thereto; the dispersive device is a dispersive optical element, and the dispersive device can be a prism, a reflective grating or a transmissive grating, but the disclosure is not limited thereto; the optical focusing element may be a focusing lens or a reflective focusing optic, and the optical focusing element may be a cylindrical focusing lens, a spherical focusing lens, or a concave mirror, but the disclosure is not limited thereto; the light splitting element can be a spatial light splitting element or an optical fiber light splitting element, and the light splitting element can be a flat plate beam splitter, a light splitting prism or an optical fiber light splitting ring, an optical fiber beam splitter and an optical fiber circulator, which are not specifically limited in the disclosure.
According to the coherence tomography device, the light source component comprises the wide-spectrum light source device, the dispersion device and the digital micromirror, the digital micromirror is controlled at a high speed, the output of the light wave frequency tunable light source can be rapidly realized, the light source output speed is high, and the signal-to-noise ratio is high.
Wherein, interfere subassembly 2 and set up at the light exit of light source subassembly 1, the light that light source subassembly 1 sent carries out the beam split in interfering subassembly 2 and interferes.
The interference assembly 2 generally comprises a beam splitting device 21, a reflecting element 22 and a sample 23, and in some interference assemblies, an optical focusing element. The light output process at the interference module is as follows: the light source output by the light source assembly 1 enters the light splitting device 21 of the interference assembly, the light is split into two beams under the action of the light splitting device 21, one beam of light is guided into the reference arm, the other beam of light is guided into the signal arm, the light in the reference arm is reflected by the reflecting element 22 and returns to the light splitting device 21 again, the light in the signal arm irradiates on a sample and is reflected back to the light splitting device 22 by the sample, the reflected light of the reference arm and the reflected light of the signal arm are combined after interference in the light splitting device 21, and the combined light enters the photoelectric detection assembly.
Further, the type and number of the optical elements in the reference arm in the interference assembly need to be consistent with the type and number of the optical elements in the signal arm to ensure that the transmission modes of the light in the reference arm and the signal arm are consistent, but the disclosure is not limited thereto, and if the type and number of the optical elements in the reference arm and the signal arm are not consistent, the transmission modes of the reference arm and the signal arm can be ensured to be consistent.
It should be noted that the optical splitter 21 may be an optical splitter, specifically, a flat beam splitter, a beam splitter prism, and an optical fiber splitter; the reflecting element may be a plane mirror, and may specifically be a flat metal film mirror, a dielectric film mirror, but the present disclosure is not limited thereto, and the selection of the specific light splitting device and the reflecting element may be determined according to the actual use requirement.
The photoelectric detection component 3 is arranged at an interference light ray outlet of the interference component 2, and the light detection component 3 is used for acquiring light intensity distribution of the interference light ray.
The photodetection assembly 3 generally comprises an area array photodetector 31 and an imaging optical lens group 32. The working process of the light in the photoelectric detection assembly is as follows: the light after interference occurs through the interference component enters the photoelectric detection component, the sample plane image is imaged on the area array photoelectric detector 31 through the imaging optical lens group 32, and the device can obtain the interference image of the sample plane under the light sources with different frequencies by combining the light with different frequencies emitted by the light source with tunable frequency in the light source component 1.
It should be noted that the imaging optical lens group may be a mature camera lens or a lens combination, and specifically may be a telecentric lens, an optical zoom lens or a lens combination with an optical focusing element; the area-array photodetector may be a CCD (Charge Coupled Device) camera or a CMOS (Complementary Metal Oxide Semiconductor) camera, but the present disclosure is not limited thereto, and different imaging optical lens sets or area-array photodetectors may be selected according to specific use requirements.
The coherence tomography device comprises a light source component, an interference component and a photoelectric detection component, wherein the light source component can comprise a wide-spectrum light source device, a chromatic dispersion device and a digital micromirror, a frequency-tunable light source can be emitted by the light source component, and an image of a sample can be formed on the photoelectric detection component through the interference component.
The sweep frequency OCT device provided by the disclosure can realize scanning imaging in various sample chromatographic planes, and the specific implementation mode is as follows:
fig. 1 and 4 are schematic structural diagrams of a global imaging-based swept frequency OCT apparatus, as shown in fig. 1 and 4, the scanning mode is a global imaging scanning mode, and the apparatus in fig. 4 is a modification of the apparatus in fig. 1, and the operation process is as follows:
with respect to fig. 1, the broad spectrum light source in the light source module 1 outputs into the interference module as parallel collimated light, the light splitting device 21 in the interference assembly 2 splits the output light of the light source assembly into the reference arm and the signal arm, the light from the reference arm is reflected by the reflecting element 22 and returned to the beam splitter 21, the signal arm light is directed to the sample 23, and is reflected by the sample 23 back to the light splitting device 21, the reflected signal arm light and the reflected reference arm light are combined by the light splitting device, generates interference and outputs the interference light to the photoelectric detection component 3, the photoelectric detection component 3 inputs the interference light output by the interference component 2 to the imaging optical lens group 32, and the sample plane image is imaged on the area array photoelectric detector 31, and is combined with a frequency tunable light source in the light source assembly, so that the interference two-dimensional image of the sample plane under the irradiation of different frequency lights can be obtained.
With respect to fig. 4, equivalent modifications are made to the interference component and the photodetection component, and the number of optical focusing elements 33 in the photodetection component is increased in fig. 4 or by changing the position of a part of the optical focusing elements, or changing the number or position of the optical focusing elements 24 in the interference component, but the optical path and the operation of the apparatus are similar to those in fig. 1, and are not repeated here. It should be noted that the deformation apparatus based on fig. 1 is included in the coherence tomography apparatus of the present disclosure.
Fig. 5 and 6 are schematic structural diagrams of a line scan-based swept frequency OCT apparatus, as shown in fig. 5 and 6, which uses a tomographic line scan, and the apparatus in fig. 6 is a modification of the apparatus in fig. 5, and the operation procedure is as follows:
referring to fig. 5, the light source output by the light source assembly is output as spatially collimated light, and enters the interference assembly, the light source is input into the reference arm and the signal arm respectively after passing through the light splitter, the optical focusing element in the reference arm converges incident light into line-shaped focused light, and reflects the line-shaped focused light back into the light splitter through the reflecting element, the light in the signal arm passes through the optical scanning element 25 and the optical focusing element in the signal arm, and irradiates the incident light at different spatial positions of the sample in the form of line-shaped focused light, the light reflected by the sample is returned to the light splitter through the original optical path, and then combines with the light of the reference arm and interferes, the interfered light images the line-shaped focused light on the photodetector through the optical focusing element 33 in the photodetection assembly, and by obtaining the light intensities of different positions of the line-shaped focused light on the photodetector, the light is applied to different positions on the sample by combining the optical scanning element 25 at different times, two-dimensional light intensity distribution in a sample plane under a certain incident light frequency can be obtained through scanning, light frequency scanning is carried out on a light source in the light source assembly, linear scanning is carried out in a combining surface, and two-dimensional light intensity distribution of the sample under different frequency lights can be obtained.
With respect to fig. 6, equivalent modifications are made to the interference component and the photodetection component, and the number of optical focusing elements is increased in fig. 5 or the positions of part of the optical focusing elements or the optical scanning elements are changed, but the optical path and the operation of the apparatus are similar to those in fig. 5, and are not repeated here. It should be noted that the modified apparatus based on fig. 5 is included in the coherence tomography apparatus of the present disclosure.
Fig. 7 is a schematic structural diagram of a swept frequency OCT apparatus based on point scanning, and as shown in fig. 7, the scanning mode uses a point scanning mode, and the working process thereof is as follows:
the light source component outputs a light source with tunable frequency, which can be an optical fiber or space focusing light source output mode, the light source enters an interference component after being collimated by an optical focusing element, the light enters a reference arm and a signal arm respectively through the light splitting action of a light splitting element, the optical focusing element in the reference arm converges incident light into point focusing light, meanwhile, a reflecting element in the signal arm reflects the incident light back to the light splitting element, the light in the signal arm passes through an optical scanning element and the optical focusing element and irradiates the light at different spatial positions of a sample in the form of the point focusing light, wherein the optical scanning element can control the point focusing light to irradiate at different in-plane positions of the sample, the light reflected by the sample returns to the light splitting element through an original light path, the light is combined with the reflected light in the reference arm and interferes, and the interfered light irradiates on a photoelectric detector through the guiding action of the optical element in the photoelectric detection component, by acquiring the light intensity obtained by the photoelectric detector and combining different positions of the sample hit by the optical scanning element at different time, the two-dimensional light intensity distribution in the sample plane under a certain incident light frequency can be obtained through scanning, the light frequency scanning is carried out through the light source, the line scanning is carried out in the combining surface, and the two-dimensional light intensity distribution of the sample under different frequency lights can be obtained.
It should be noted that, the modifications to the point-scan-based swept-frequency OCT apparatus in fig. 7 all belong to the coherence tomography apparatus of the present disclosure.
The present disclosure provides a coherence tomography method, as shown in fig. 8, the method including:
s101: starting a light source assembly, wherein parallel light rays emitted by the light source assembly enter an interference assembly, and the parallel light rays are divided into a first light beam and a second light beam by a light splitting element in the interference assembly;
s012: the first light beam irradiates on a preset sample and is reflected by the sample to form a first reflected light beam, and the second light beam irradiates on a reflecting element in the interference assembly and is reflected by the reflecting element to form a second reflected light beam;
s103: the first reflected light beam and the second reflected light beam return to the light splitting element along an original optical path and interfere in the light splitting element to form an interference light beam;
s104: the interference light beam enters the photoelectric detection assembly, and two-dimensional light intensity distribution of the sample is formed in the photoelectric detection assembly.
Wherein, after step S014, the method further comprises: and constructing a three-dimensional structural image of the sample according to the two-dimensional light intensity distribution of the sample. The constructing a three-dimensional structural image of the sample comprises: the method comprises the steps of obtaining calibration parameters of a preset calibration sample and three-dimensional structure image parameters of the sample, processing the calibration parameters and the three-dimensional structure image parameters of the sample, and reconstructing the three-dimensional structure image parameters of the sample to obtain a real three-dimensional structure image of the sample.
Specifically, the method for constructing the three-dimensional structure image of the sample comprises the following steps:
step 1: obtaining the interference light intensity distribution I of each point of the plane of the test sample by scanning through the frequency-sweeping OCT device0(x,y,λ)；
Step 2: obtaining the background light intensity distribution B0(x, y) of the sample by measuring the light intensity distribution of the sample when no light source Is used for illumination, and background deducting the signal, i.e. Is (x, y, lambda) ═ I0(x,y,λ)-B0(x,y)；
And step 3: normalizing the measured interference light intensity distribution of each site with the intensity S (lambda) of the frequency-tunable light source along with the wavelength change, namely, I (x, y, lambda) Is (x, y, lambda)/S (lambda), wherein S (l) can be obtained by measuring through a power meter, a spectrometer or a spectrophotometer;
and 4, step 4: performing parameter transformation on I (x, y, lambda), obtaining the change I (x, y, k) of light intensity along with wave vector by k being 2 pi/lambda, and simultaneously performing linear interpolation and 0 extension and supplement on I (x, y, k) to ensure the convenience of a subsequent algorithm;
and 5: fourier transform of I (x, y, k), i.e.
Obtaining A (x, y, z) which is the z-direction structure distribution of the sample at the x, y coordinates;
step 6: filtering or removing noise from the A (x, y, z) signal by an algorithm for removing background and noise;
and 7: calibrating the deviation coefficient az between the distribution of A (z) obtained in the step 4 and the real z-direction distribution of the sample by using a standard sample calibration, and measuring the z-direction structure distribution of the real sample as A (z x a);
and 8: the data a (ax x, ay y, az z) are used to reconstruct a true three-dimensional structural image of the sample, again by scaling with standard samples to obtain the coefficients of deviation ax, ay of the measured x, y positions from the true x0, y0 positions of the sample.
In the above steps, the fourier transform algorithm may be a discrete fourier transform or a fast fourier transform algorithm; the algorithm for removing the background and the noise can be an algorithm such as a least square method, high-frequency filtering or wavelet transformation; the standard sample in the step 7 can be a thin film sample with known z-direction structural distribution or a flat plate reflector placed on a high-precision lifting platform; the standard sample used in step 8 may be a differentiation plate or a checkerboard sample having a standard size.
According to the coherence tomography method, the three-dimensional structural image of the sample can be obtained through imaging of the chromatographic plane of the sample, and the purpose of realizing rapid three-dimensional imaging of the sample by using a coherence tomography device is achieved.
It should be noted that although the various steps of the coherence tomography method of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that the steps must be performed in that particular order or that all of the depicted steps must be performed to achieve the desired results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions, etc.
The embodiment of the present disclosure provides a second structural diagram of a swept frequency OCT apparatus, where the apparatus is a configuration that embodies each component in the swept frequency OCT apparatus based on global imaging, as shown in fig. 9:
in this embodiment, the light source module uses a superluminescent diode light source 101 with a central wavelength of 850nm, a band width of 80nm, an output light power of 7mW based on single-mode fiber output, the superluminescent diode 101 is connected to the port 100 of the optical fiber circulator 102 with an operating band of 850nm through an optical fiber flange, light of the light source is directed to the port 200 in the circulator for output, and is collimated by two plano-convex lenses and then refocused onto a reflection grating 104 with a blazed wavelength of 750nm and a scribe number of 1200l/mm, light with different wavelengths diffracted by the reflection grating 104 is collimated by a focusing lens 103 and then irradiated onto different spatial positions of the digital micromirror 12, the digital micromirror 12 is controlled by a circuit to turn on and off switches at different spatial positions at a speed of 1KHz, so that light with different wavelengths is reflected by the digital micromirror 12 along an original incident light path back to the port 200 of the optical fiber circulator 102 at a frequency of 1KHz, the light entering from the No. 200 port is guided to the No. 300 port to be output, and the frequency tunable light source output of single-mode fiber output, tuning frequency of 1KHz, wavelength of 810-890nm and tuning wavelength precision of 1nm is realized.
After the light output by the light source component is collimated by the focusing lens I103, incident light is divided into a reference arm and a signal arm by an unpolarized beam splitter cube 201 with a working wavelength band of 700-, the surface of the sample is imaged on a photoelectric detector 31 connected with the telecentric lens through the telecentric lens 302, the photoelectric detector 31 is an area-array camera, the area-array camera adopts a cmos black-and-white camera with the highest frame rate of 800fps, and the resolution is 640 multiplied by 480.
In this embodiment, the refresh rates of the digital micromirror and the cmos camera are set to 100Hz, that is, the tunable light source performs wavelength switching once every 10ms, the camera takes pictures of the light intensity distribution on the surface of the sample within 10ms, and the picture taking of the full field of view of the sample under all tunable wavelengths is completed within about 0.8 s.
In this embodiment, a flat mirror placed on a high-precision lifting table is used as a standard sample, the lifting table with the lifting precision of 10um is used to scan the flat mirror within the range of 0-2mm, calibration correction coefficients of z-direction scale and real z-direction scale measured by sweep frequency OCT are obtained, and when the in-plane dimension is corrected, a grid ruler with the grid size of 10um is used to calibrate the real dimensions of the camera pixel and the sample.
The embodiment of the present disclosure provides a third structural diagram of a swept frequency OCT apparatus, which is a specific configuration of each component in the swept frequency OCT apparatus based on point scanning, as shown in fig. 10:
in this embodiment, the light source module uses a light emitting diode 1011 with a central wavelength of 420nm, a wavelength width of 50nm, and an output power of 200mW, the light emitting diode 1011 is collimated into parallel light by a plano-convex lens 1021, and is focused into linear focused light by a cylindrical lens 1031, and is input into a dispersion prism 1041, through the dispersion action of the dispersion prism 1041, the incident light is divided into a plurality of light beams, the plurality of different light beams are output from the dispersion prism 1041 at different angles, the light beams with different wavelengths output from the dispersion prism are collimated by the cylindrical lens 1031 and then irradiated onto different spatial positions of the digital micromirror 12, the digital micromirror is controlled by a circuit to open and close switches at different spatial positions at a speed of 10KHz, so that the light beams with different wavelengths are reflected by the digital micromirror 12 at a frequency of 10KHz and are focused into an optical fiber with a core diameter of 100um by the plano-convex lens 1021, the output of the wavelength tunable optical fiber light source with the wave band of 400-450nm is realized.
After the light output by the light source is collimated by the focusing lens II 2021, the incident light is divided into a reference arm and a signal arm by a non-polarizing plate beam splitter 2041 with the working wave band of 350-1100nm according to the proportion of 50:50, a microscope objective 2031 with the working multiple of 5 is arranged in the reference arm, the microscope objective 2031 focuses the incident light onto a fixed reflector 2051, the reflector is an ultraviolet aluminum coating film and the working wave band of 250-800nm, the incident light is reflected by the reflector and reflected onto the plate beam splitter 2041 along the original light path, in the signal arm, the incident light firstly irradiates on a biaxial galvanometer and is reflected into the microscope objective which is the same as that in the reference arm by the galvanometer, the microscope objective focuses the incident light into a focusing point with the size of 20um, and the angle of the incident light entering the microscope objective can be controlled by the change of the biaxial angle in the galvanometer, therefore, the spatial position of signal light focusing on a sample is controlled, light reflected from the sample returns to the flat plate beam splitter through an original light path and is combined with the reflected light of the reference arm and interfered, and then the interfered light is emitted into a photodiode with the sensing surface of 8mm in diameter, so that the intensity of the light signal reflected by a single point on the sample is detected.
In this embodiment, the response speed of the photodiode is 50MHz, and the scanning frequency of the galvanometer is 1 MHz; the light spot scanning range that biax galvanometer can be regulated and control is 1.5mm, and the precision is 20 um.
In the embodiments of the two coherence tomography apparatuses with specific elements provided by the present disclosure, the purpose of rapidly imaging the tomographic plane of the sample can be achieved, and the embodiments all use the light source assembly provided by the present disclosure, so that the light source frequency tuning speed is fast, the signal-to-noise ratio is high, and the cost of the apparatus is reduced.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
Claims (10)
1. A coherence tomography apparatus, comprising:
the light source assembly comprises a wide-spectrum light source device, a dispersion device and a digital micromirror, wherein light rays emitted by the wide-spectrum light source device sequentially pass through the dispersion device and the digital micromirror, and the light source assembly provides light source output for the coherence tomography device;
the interference assembly is arranged at a light ray outlet of the light source assembly, and light rays emitted by the light source assembly are subjected to light splitting and interference in the interference assembly;
the photoelectric detection assembly is arranged at an interference light ray outlet of the interference assembly, and the light ray detection assembly is used for acquiring the light intensity distribution of the interference light ray.
2. The coherence tomography apparatus according to claim 1,
the light source module further includes a plurality of optical focusing elements disposed between the broad spectrum light source element, the dispersive element, and the digital micromirror.
3. The coherence tomography apparatus according to claim 2,
the optical focusing element is a focusing lens or a reflective focusing optic.
4. The coherence tomography apparatus according to claim 1,
the light source output mode of the light source component is optical waveguide output or space light output.
5. The coherence tomography apparatus according to claim 1,
the light source component further comprises a light splitting element, and the light splitting element is used for splitting light rays emitted by the wide-spectrum light source element.
6. The coherence tomography apparatus according to claim 1,
the wavelength range of the light source emitted by the wide-spectrum light source device is more than or equal to 10nm, and the central wavelength of the wide-spectrum light source device is within the range of 300-2500 nm.
7. The coherence tomography apparatus according to claim 1,
the output light power of the wide-spectrum light source device is more than or equal to 0.1 mW.
8. A method of coherent tomography comprising:
starting a light source assembly, wherein parallel light rays emitted by the light source assembly enter an interference assembly, and the parallel light rays are divided into a first light beam and a second light beam by a light splitting element in the interference assembly;
the first light beam irradiates on a preset sample and is reflected by the sample to form a first reflected light beam, and the second light beam irradiates on a reflecting element in the interference assembly and is reflected by the reflecting element to form a second reflected light beam;
the first reflected light beam and the second reflected light beam return to the light splitting element along an original optical path and interfere in the light splitting element to form an interference light beam;
the interference light beam enters the photoelectric detection assembly, and two-dimensional light intensity distribution of the sample is formed in the photoelectric detection assembly.
9. The coherence tomography method of claim 8,
the forming of the two-dimensional light intensity distribution of the sample in the photodetection assembly comprises:
and analyzing, calculating and constructing a three-dimensional structural image of the sample according to the two-dimensional light intensity distribution of the sample and the distribution of light rays at different wavelengths.
10. The coherence tomography method of claim 9,
the constructing a three-dimensional structural image of the sample further comprises:
the method comprises the steps of obtaining calibration parameters of a preset calibration sample and three-dimensional structure image parameters of the sample, processing the calibration parameters and the three-dimensional structure image parameters of the sample, and reconstructing the three-dimensional structure image parameters of the sample to obtain a real three-dimensional structure image of the sample.
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