CN112945130A - Ultrafast microscopic imaging system for simultaneously obtaining depth and surface information - Google Patents
Ultrafast microscopic imaging system for simultaneously obtaining depth and surface information Download PDFInfo
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- 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
- G01B11/22—Measuring arrangements characterised by the use of optical techniques for measuring depth
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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
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02041—Interferometers characterised by particular imaging or detection techniques
Abstract
The invention provides an ultrafast microscopic imaging system for simultaneously obtaining depth and surface information, which comprises a laser generator, wherein the output end of the laser generator is connected with the input end of a first coupler through a dispersion medium, the first output end of the first coupler is connected with the first end of a circulator, the second end of the circulator is connected with the first end of a collimator, the second end of the collimator is aligned with the first input/output end of a diffraction device, the second input/output end of the diffraction device is aligned with the plane of a plano-convex lens, the convex surface of the plano-convex lens is aligned with a sample to be detected, the third end of the circulator is connected with the first input end of a second coupler, the second output end of the first coupler is connected with the second input end of the second coupler through an adjustable delay medium, the output end of the second coupler is connected with the input end of a detector, and the output end of the detector is connected with the input end of a, the output end of the high-speed oscilloscope is connected with the signal processing module.
Description
Technical Field
The invention belongs to the field of ultrafast microscopic imaging, and particularly relates to an ultrafast microscopic imaging system for simultaneously obtaining depth and surface information.
Background
The ultrafast imaging is mainly of two types, one is to perform one-dimensional diffraction on ultrafast laser by using one-dimensional diffraction devices such as prisms and gratings so as to perform line scanning on a sample to be detected, and the other is to perform two-dimensional diffraction on the ultrafast laser by adopting a mode of combining the gratings and a virtual phase array so as to perform surface scanning on the sample to be detected. Although the method has a good application prospect in the field of microscopic imaging, the depth information of the sample to be detected cannot be obtained. However, in the current technology for measuring the depth information of a sample to be measured, an Optical Coherence Tomography (OCT) technology is usually adopted, which is to intensively irradiate an optical pulse to one point of the sample to be measured, the point on the sample to be measured returns reflected light after receiving the optical pulse, and the depth information of the sample is reflected according to the change of a Free Spectral Range (FSR) of an interference spectrum in the reflected light.
Disclosure of Invention
The invention provides an ultrafast microscopic imaging system for simultaneously obtaining depth and surface information, which aims to solve the problem that the depth and surface information of a sample to be detected cannot be simultaneously obtained by using the same laser signal at present.
According to a first aspect of the embodiments of the present invention, there is provided an ultrafast microscopic imaging system for simultaneously obtaining depth and surface information, comprising a laser generator, an output terminal of the laser generator connected to an input terminal of a first coupler through a dispersive medium, a first output terminal of the first coupler connected to a first terminal of a circulator, a second terminal of the circulator connected to a first terminal of a collimator, a second terminal of the collimator aligned with a first input/output terminal of a diffraction device, a second input/output terminal of the diffraction device aligned with a plane of a plano-convex lens, a convex surface of the plano-convex lens aligned with a sample to be measured, a third terminal of the circulator connected to a first input terminal of a second coupler, a second output terminal of the first coupler connected to a second input terminal of the second coupler through an adjustable delay medium, an output terminal of the second coupler connected to an input terminal of a detector, the output end of the detector is connected with the input end of the high-speed oscilloscope, and the output end of the high-speed oscilloscope is connected with the signal processing module;
the dispersion medium stretches the laser signal generated by the laser generator in the time domain, the first coupler divides the stretched laser signal into two paths, wherein one path of laser signal is transmitted to the diffraction device through the circulator and the collimator in turn, the laser signal generates diffracted lights with different diffraction paths through the diffraction device, the diffracted lights with different diffraction paths are converted into a plurality of parallel lights through the plano-convex lens, the plurality of parallel lights irradiate different positions of the sample to be detected, the corresponding positions of the sample to be detected generate reflected lights after receiving the parallel lights, the reflectivity at the corresponding position is coded into the spectrum of the reflected light, and the reflected light is transmitted to the circulator through the plano-convex lens, the diffraction device and the collimator in sequence along the original transmission path; the circulator transmits the reflected light to the second coupler;
the adjustable delay medium delays another laser signal divided by the first coupler to perform optical path matching with the returned reflected light, and the delayed another laser signal is used as reference light to be transmitted to the second coupler; the reflected light and the reference light interfere at the second coupler to generate a reflected light interference signal, and the detector detects the reflected light interference signal to generate an electric signal; the high-speed oscilloscope performs analog-to-digital conversion on the electric signal to generate a digital signal;
the signal processing module determines the reflectivity of the sample to be detected at the corresponding position according to the spectral intensity of the digital signal, so as to determine the surface information of the corresponding position, performs Fourier transformation on the digital signal, and determines the depth information of the sample to be detected at the corresponding position according to the free spectral range of the digital signal after the Fourier transformation.
In an optional implementation manner, the device further includes a stepper motor, the same plane where each parallel light is located is a first plane, an X axis is located on the first plane and perpendicular to each parallel light, a Z axis is parallel to each parallel light, a Y axis is perpendicular to the X axis and the Z axis, the sample to be measured is located under at least part of the parallel light in each parallel light, so that the corresponding parallel light performs line scanning on the sample to be measured in the X axis direction, and the stepper motor drives the sample to be measured to move along the Y axis direction, so that the sample to be measured performs plane scanning of two dimensions of X-Y.
In another optional implementation, the optical fiber further comprises an optical amplifier, and the dispersive medium is connected with the input end of the first coupler through the optical amplifier.
In another optional implementation manner, the polarization controller is further included, and the third end of the circulator is connected to the second input end of the second coupler through the polarization controller.
In another alternative implementation, the laser signal includes a plurality of spectral costs having different wavelengths within a period.
In another alternative implementation, the laser generator is an ultrafast laser, the spectral range of the laser signal is on the order of tens of nanometers, and the pulse repetition rate is greater than megahertz.
In another optional implementation manner, the tunable delay medium performs delay processing on spectral components with different wavelengths in the laser signal according to the size of the wavelength, so as to implement optical path matching between the delayed spectral components and the returned reflected light.
In another alternative implementation, the size of the field of view of the system is determined by the dispersive power of the diffraction device, the focal length of the microscope objective, and the spectral bandwidth of the laser signal.
In another alternative implementation, the wavelength resolving power of the system is determined by several factors: the dispersion capacity of a dispersion medium, the spectral resolution capacity of Dispersion Fourier Transform (DFT) and the spectral resolution capacity determined by the bandwidths of a detector and a high-speed oscilloscope are the first, and the final spectral resolution capacity of the system is determined by the maximum of the three parameters.
In another alternative implementation, the imaging frame rate of the system is determined by the pulse frequency of the light source, typically the pulse frequency of the ultrafast laser is greater than megahertz; the effective frame rate of imaging also depends on the moving speed of the sample to be measured on the Y axis; the pixel point of the image is determined by the spectral width of the laser signal, the dispersion coefficient of the dispersion medium and the sampling rate of the high-speed oscilloscope.
The invention has the beneficial effects that:
1. the invention can simultaneously measure the depth and surface information of a sample to be measured by using the same laser signal, records the spectrum by using a Dispersion Fourier Transform (DFT) technology, and can directly collect the spectrum information by using a detector while ensuring the spectral resolution compared with the traditional spectrometer, thereby increasing the sampling rate to megahertz; the ultrafast laser can ensure that one pulse not only can contain spectral information up to dozens of nanometers, but also has a wider scanning range compared with the traditional Optical Coherence Tomography (OCT), and in addition, the ultrafast laser has the repetition frequency of megahertz, so that an imaging system can be ensured to have a higher imaging frame rate; the spatial position and the spectrum can be made to correspond by adopting a diffraction grating for dispersion, so that the information of different spatial positions of the sample can be reflected by the spectral intensity of the reflected light;
2. in addition, because the diffraction angles of the light with different wavelengths are fixed after the light with different wavelengths enters the diffraction device, when the position relationship between the diffraction device and the plano-convex lens is determined, the relationship between each parallel light and the X-axis coordinate is also fixed, and the reflected light can be identified from which X-coordinate position on the sample to be detected returns according to the wavelength of the returned reflected light; when the depth information is measured, the beam splitting light is not set for each parallel light, but the adjustable delay medium is set, so that the adjustable delay medium respectively delays the spectral components with different wavelengths in the laser signal according to the wavelength, and the optical path matching between the delayed spectral components and the returned reflected light is realized, therefore, the construction cost of multipoint depth measurement can be reduced, and the position of the conventionally arranged beam splitter is not required to be respectively adjusted even if the wavelength of the spectral components in the laser signal is changed, so that the adaptability is strong; before the laser signal is transmitted to the first coupler, the laser signal is stretched in the time domain through the dispersion medium (the spectrum and the light pulse are corresponding in the process), and compared with the traditional spectrometer, the spectrum signal can be directly collected by a detector while the spectrum resolution is ensured, so that the sampling rate is increased to megahertz;
3. the invention is also provided with a stepping motor, the sample to be detected is positioned under at least part of parallel light in each parallel light so as to enable the corresponding parallel light to carry out line scanning on the sample to be detected in the X-axis direction, and the stepping motor drives the sample to be detected to move along the Y-axis direction, so that the sample to be detected is subjected to surface scanning in two dimensions of X-Y.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of an ultrafast microscopic imaging system for simultaneously acquiring depth and surface information according to the present invention;
FIG. 2 is a schematic diagram of diffraction light output by a diffraction device being incident on a sample to be measured;
FIG. 3 is a schematic structural diagram of an ultrafast microscopic imaging system for acquiring depth and surface information simultaneously according to another embodiment of the present invention.
Detailed Description
In order to make the technical solutions in the embodiments of the present invention better understood and make the above objects, features and advantages of the embodiments of the present invention more comprehensible, the technical solutions in the embodiments of the present invention are described in further detail below with reference to the accompanying drawings.
In the description of the present invention, unless otherwise specified and limited, it is to be noted that the term "connected" is to be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, or a communication between two elements, or may be a direct connection or an indirect connection through an intermediate medium, and a specific meaning of the term may be understood by those skilled in the art according to specific situations.
Referring to fig. 1, a schematic structural diagram of an embodiment of an ultrafast microscopic imaging system for simultaneously acquiring depth and surface information according to the present invention is shown. The system can comprise a laser generator, wherein the output end of the laser generator is connected with the input end of a first coupler through a dispersion medium, the first output end of the first coupler is connected with the first end of a circulator, the second end of the circulator is connected with the first end of a collimator, the second end of the collimator is aligned with the first input/output end of a diffraction device, the second input/output end of the diffraction device is aligned with the plane of a plano-convex lens, the convex surface of the plano-convex lens is aligned with a sample to be measured, the third end of the circulator is connected with the first input end of a second coupler, the second output end of the first coupler is connected with the second input end of the second coupler through an adjustable delay medium, the output end of the second coupler is connected with the input end of a detector, and the output end of the detector is connected with the input end of a high-speed oscilloscope, and the output end of the high-speed oscilloscope is connected with the signal processing module.
The dispersion medium stretches the laser signal generated by the laser generator in the time domain, the first coupler divides the stretched laser signal into two paths, wherein one path of laser signal is transmitted to the diffraction device through the circulator and the collimator in turn, the laser signal generates diffracted lights with different diffraction paths through the diffraction device, the diffracted lights with different diffraction paths are converted into a plurality of parallel lights through the plano-convex lens, the plurality of parallel lights irradiate different positions of the sample to be detected, the corresponding positions of the sample to be detected generate reflected lights after receiving the parallel lights, the reflectivity at the corresponding position is coded into the spectrum of the reflected light, and the reflected light is transmitted to the circulator through the plano-convex lens, the diffraction device and the collimator in sequence along the original transmission path; the circulator transmits the reflected light to the second coupler.
The adjustable delay medium delays another laser signal divided by the first coupler to perform optical path matching with the returned reflected light, and the delayed another laser signal is used as reference light to be transmitted to the second coupler; the reflected light and the reference light interfere at the second coupler to generate a reflected light interference signal, and the detector detects the reflected light interference signal to generate an electric signal; the high-speed oscilloscope performs analog-to-digital conversion on the electric signal to generate a digital signal; the signal processing module determines the reflectivity of the sample to be detected at the corresponding position according to the spectral intensity of the digital signal, so as to determine the surface information of the corresponding position, performs Fourier transformation on the digital signal, and determines the depth information of the sample to be detected at the corresponding position according to the free spectral range corresponding to the digital signal after the Fourier transformation.
In this embodiment, after the incident light enters the diffraction device, the diffraction angle of the diffracted light output from the diffraction device is related to the wavelength of the incident light, that is, the diffraction paths of the incident light with different wavelengths corresponding to the diffracted light emitted from the diffraction device are different, so that in the ultra-fast imaging of the prior art or in the present invention, a laser signal generated by a laser generator includes a plurality of spectral components with different wavelengths within one period, so as to perform line scanning on a sample to be measured, wherein the same plane where each parallel light is located is set as a first plane, an X axis is located on the first plane and perpendicular to each parallel light, a Z axis is parallel to each parallel light, and a Y axis is perpendicular to both the X axis and the Z axis. In addition, in the conventional Optical Coherence Tomography (OCT) technique, a light pulse is intensively irradiated to a point of a sample to be measured, the point on the sample to be measured receives the light pulse and returns reflected light, and depth information of the sample is reflected according to a change in a Free Spectral Range (FSR) of an interference spectrum in the reflected light. Because the existing ultrafast imaging technology can already scan the line of the sample to be detected, and a plurality of points act on the sample to be detected in the process, when the existing ultrafast imaging technology is combined with an Optical Coherence Tomography (OCT) technology, a person skilled in the art usually thinks that the reflected light returned by the plurality of points on the sample to be detected in the existing ultrafast imaging technology is directly used for detecting the depth of each point, so that the number of points of the sample to be detected with depth information at a time is increased. However, as shown in fig. 2, when the second step from left to right in the sample to be measured is shown as a solid line, the diffracted light intersects with the point a in the sample to be measured, and when the second step in the sample to be measured is shown as a dotted line, the diffracted light intersects with the point B in the sample to be measured, and the positions of the point a and the point B on the sample to be measured are different, it can be seen that if the depth is directly detected by using the reflected light returned from the sample to be measured in the conventional ultrafast imaging technology, the same diffracted light cannot measure the depth of different samples to be measured at the same X-axis coordinate. Therefore, the plano-convex lens is added between the diffraction device and the sample to be measured, so that diffracted lights with different diffraction angles are vertically incident on the sample to be measured, each parallel light vertically incident on the sample to be measured corresponds to a unique X-axis coordinate, in addition, after the lights with different wavelengths are incident on the diffraction device, the diffraction angles are fixed, when the position relationship between the diffraction device and the plano-convex lens is determined, the relationship between each parallel light and the X-axis coordinate is also fixed, and according to the wavelength of the returned reflected light, the position of which X-axis coordinate the reflected light returns from on the sample to be measured can be identified.
In addition, the existing Optical Coherence Tomography (OCT) technology splits an optical signal incident on a sample to be measured, transmits a part of the optical signal to the sample to be measured, and transmits a part of the optical signal to a reference mirror. When a sample to be detected is not placed on the horizontal table surface below the plano-convex lens, and each horizontal light directly enters the horizontal table surface, on the premise that the positions of the diffraction device, the plano-convex lens and the horizontal table surface are fixed, aiming at each spectral component in the laser signal, after the diffraction device receives the spectral component with the corresponding wavelength, the optical path of the output diffracted light, the parallel light and the returned reflected light is fixed, so that the adjustable delay medium respectively performs delay processing on the spectral components with different wavelengths in the laser signal according to the wavelength, and the optical path matching between the delayed spectral components and the returned reflected light can be realized. When the depth information is measured, the adjustable delay medium is arranged instead of beam splitting light aiming at each parallel light, so that the adjustable delay medium respectively delays the spectral components with different wavelengths in the laser signal according to the wavelength, and the optical path matching between the delayed spectral components and the returned reflected light is realized, thereby not only reducing the construction cost of multipoint depth measurement, but also not needing to respectively adjust the position of the conventionally arranged beam splitter even if the wavelength of the spectral components in the laser signal changes, and having strong adaptability.
For the sample to be detected, when the sample to be detected is an ideal reflector, the intensity of the returned reflected light is the same as the intensity of the corresponding spectral component in the original laser signal, and when the surface of the sample to be detected is uneven, the reflectivity of the surface of the sample to be detected changes, and the intensity of the returned reflected light also changes, so that the signal processing module can determine the reflectivity of the sample to be detected at the corresponding position according to the spectral intensity corresponding to the digital signal, and further determine the surface information of the corresponding position. For a sample to be detected with a layered structure, the free spectral ranges FSR of interference spectra of reflected light at different depth positions are different correspondingly due to different optical path differences, so that Fourier change is performed on digital signals corresponding to the reflected light interference signals output by the second coupler, and depth information of the sample to be detected at the corresponding position can be determined according to the free spectral range of the digital signals after Fourier change. In addition, the laser generator can be an ultrafast laser, the spectral range of the laser signal can be tens of nanometers, the pulse repetition frequency is greater than megahertz, the spectral range of the laser signal can be tens of nanometers, compared with the traditional Optical Coherence Tomography (OCT) technology, the laser generator has a wider scanning range, the laser signal has the repetition frequency of megahertz, and the imaging system can be ensured to have a higher imaging frame rate. Before the laser signal is transmitted to the first coupler, the laser signal is stretched in the time domain through the dispersion medium (the spectrum and the optical pulse are corresponding in the process), and compared with a traditional spectrometer, the spectrum signal can be directly collected by a detector while the spectrum resolution is guaranteed, so that the sampling rate is increased to megahertz.
The structure can only realize the line scanning of the sample to be measured, and the synchronous measurement of the depth and the surface information on the corresponding position on the sample to be measured is realized in the line scanning process. In order to realize the surface scanning of the sample to be detected, the invention is also provided with a stepping motor, the sample to be detected is positioned under at least part of parallel light in each parallel light so as to enable the corresponding parallel light to carry out the line scanning on the sample to be detected in the X-axis direction, and the stepping motor drives the sample to be detected to move along the Y-axis direction, so that the surface scanning of the sample to be detected in two dimensions of X-Y is carried out. In one example, the laser generator may be: an ultrafast pulse laser with center wavelength of 1565nm, spectral bandwidth of 15nm and repetition frequency of MHz; the dispersion medium can be a dispersion compensation fiber with the dispersion coefficient of 1.2 ns/nm; the first coupler can be an 80:20 coupler, the low-power laser signal divided by the first coupler is transmitted to the adjustable delay medium, and the high-power laser signal is transmitted to the circulator; the diffraction device is a 1200-line diffraction grating; the power coupling ratio of the second coupler is 1: 1; the sampling rate of the detector is 50Gsa/s, the sampling time is longer than the pulse time after the dispersion medium is stretched, and the number of collected pulses depends on the size of a sample to be scanned and is limited by the storage capacity of the high-number oscillograph.
The field size of the microscopic imaging system is mainly determined by the dispersion capacity of the diffraction device, the focal length of the microobjective and the spectral bandwidth of the laser signal; the wavelength resolving power is mainly determined by several factors: the dispersion capacity of a dispersion medium, the spectral resolution capacity of Dispersion Fourier Transform (DFT) and the spectral resolution capacity determined by the bandwidth of digital devices such as a detector, a high-speed oscilloscope and the like are adopted, and the maximum spectral resolution capacity of the system is determined by the maximum of the three parameters; the imaging frame rate is mainly determined by the pulse frequency of the light source, and the pulse frequency of the ultrafast laser is usually greater than megahertz; the effective frame rate of imaging also depends on the moving speed of the sample to be measured on the Y axis; the pixel point of the image is mainly determined by the spectral width of the laser signal, the dispersion coefficient of the dispersion medium and the sampling rate of the high-speed oscilloscope.
The embodiment shows that the depth and surface information of a sample to be measured can be measured simultaneously by using the same laser signal, the spectrum is recorded by using a Dispersion Fourier Transform (DFT) technology, and compared with the traditional spectrometer, the spectrum analyzer can ensure the spectral resolution and directly collect the spectral information by using a detector, so that the sampling rate is increased to megahertz; the ultrafast laser can ensure that one pulse not only can contain spectral information up to dozens of nanometers, but also has a wider scanning range compared with the traditional Optical Coherence Tomography (OCT), and in addition, the ultrafast laser has the repetition frequency of megahertz, so that an imaging system can be ensured to have a higher imaging frame rate; the spatial position and the spectrum can be made to correspond by using the diffraction grating for dispersion, so that the spectral intensity of the reflected light can be used for reflecting the information of different spatial positions of the sample.
Referring to fig. 3, it is a schematic structural diagram of another embodiment of the ultrafast microscopic imaging system for simultaneously acquiring depth and surface information according to the present invention. Fig. 3 is different from the system shown in fig. 1 in that it further includes an optical amplifier and a polarization controller, the dispersive medium is connected to the input end of the first coupler through the optical amplifier, and the optical amplifier is used for amplifying the stretched laser signal; and the third end of the circulator is connected with the second input end of the second coupler through the polarization controller, and the polarization controller is used for adjusting the polarization state of the reflected light.
The embodiment shows that the depth and surface information of a sample to be measured can be measured simultaneously by using the same laser signal, the spectrum is recorded by using a Dispersion Fourier Transform (DFT) technology, and compared with the traditional spectrometer, the spectrum analyzer can ensure the spectral resolution and directly collect the spectral information by using a detector, so that the sampling rate is increased to megahertz; the ultrafast laser can ensure that one pulse not only can contain spectral information up to dozens of nanometers, but also has a wider scanning range compared with the traditional Optical Coherence Tomography (OCT), and in addition, the ultrafast laser has the repetition frequency of megahertz, so that an imaging system can be ensured to have a higher imaging frame rate; the spatial position and the spectrum can be made to correspond by using the diffraction grating for dispersion, so that the spectral intensity of the reflected light can be used for reflecting the information of different spatial positions of the sample.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is to be controlled solely by the appended claims.
Claims (10)
1. An ultrafast microscopic imaging system for simultaneously obtaining depth and surface information, comprising a laser generator, wherein the output end of the laser generator is connected with the input end of a first coupler through a dispersion medium, the first output end of the first coupler is connected with the first end of a circulator, the second end of the circulator is connected with the first end of a collimator, the second end of the collimator is aligned with the first input/output end of a diffraction device, the second input/output end of the diffraction device is aligned with the plane of a plano-convex lens, the convex surface of the plano-convex lens is aligned with a sample to be measured, the third end of the circulator is connected with the first input end of a second coupler, the second output end of the first coupler is connected with the second input end of the second coupler through an adjustable delay medium, the output end of the second coupler is connected with the input end of a detector, the output end of the detector is connected with the input end of the high-speed oscilloscope, and the output end of the high-speed oscilloscope is connected with the signal processing module;
the dispersion medium stretches the laser signal generated by the laser generator in the time domain, the first coupler divides the stretched laser signal into two paths, wherein one path of laser signal is transmitted to the diffraction device through the circulator and the collimator in turn, the laser signal generates diffracted lights with different diffraction paths through the diffraction device, the diffracted lights with different diffraction paths are converted into a plurality of parallel lights through the plano-convex lens, the plurality of parallel lights irradiate different positions of the sample to be detected, the corresponding positions of the sample to be detected generate reflected lights after receiving the parallel lights, the reflectivity at the corresponding position is coded into the spectrum of the reflected light, and the reflected light is transmitted to the circulator through the plano-convex lens, the diffraction device and the collimator in sequence along the original transmission path; the circulator transmits the reflected light to the second coupler;
the adjustable delay medium delays another laser signal divided by the first coupler to perform optical path matching with the returned reflected light, and the delayed another laser signal is used as reference light to be transmitted to the second coupler; the reflected light and the reference light interfere at the second coupler to generate a reflected light interference signal, and the detector detects the reflected light interference signal to generate an electric signal; the high-speed oscilloscope performs analog-to-digital conversion on the electric signal to generate a digital signal;
the information processing module determines the reflectivity of the sample to be detected at the corresponding position according to the spectral intensity of the digital signal, so as to determine the surface information of the corresponding position, performs Fourier transformation on the digital signal, and determines the depth information of the sample to be detected at the corresponding position according to the free spectral range of the digital signal after the Fourier transformation.
2. The ultrafast microscopic imaging system capable of simultaneously obtaining depth and surface information as claimed in claim 1, further comprising a stepper motor, wherein the same plane where each parallel light is located is a first plane, the X axis is located on the first plane and perpendicular to each parallel light, the Z axis is parallel to each parallel light, the Y axis is perpendicular to both the X axis and the Z axis, the sample to be tested is located right below at least a portion of the parallel light in each parallel light, so that the corresponding parallel light performs line scanning on the sample to be tested in the X axis direction, and the stepper motor drives the sample to be tested to move along the Y axis direction, thereby performing plane scanning on the sample to be tested in two dimensions of X-Y.
3. The system of claim 1 or 2, further comprising an optical amplifier, wherein the dispersive medium is connected to the input of the first coupler through the optical amplifier.
4. The system of claim 3, further comprising a polarization controller, wherein the third end of the circulator is connected to the second input of the second coupler via the polarization controller.
5. The system of claim 1, wherein the laser signal includes a plurality of spectral costs having different wavelengths within a period.
6. The system of claim 1 or 5, wherein the laser generator is an ultrafast laser, the laser signal has a spectral range of tens of nanometers, and the pulse repetition rate is greater than MHz.
7. The system of claim 1, wherein the tunable delay medium delays the spectral components of the laser signal having different wavelengths according to the wavelength, so as to match the optical path length between the delayed spectral components and the returned reflected light.
8. The system of claim 1, wherein the field of view of the system is determined by the dispersive power of the diffraction device, the focal length of the microscope objective, and the spectral bandwidth of the laser signal.
9. The system of claim 1, wherein the wavelength resolution of the system is determined by: the dispersion capacity of a dispersion medium, the spectral resolution capacity of Dispersion Fourier Transform (DFT) and the spectral resolution capacity determined by the bandwidths of a detector and a high-speed oscilloscope are the first, and the final spectral resolution capacity of the system is determined by the maximum of the three parameters.
10. The system of claim 2, wherein the frame rate of the system is determined by the pulse frequency of the light source, typically the ultrafast laser pulse frequency is greater than megahertz; the effective frame rate of imaging also depends on the moving speed of the sample to be measured on the Y axis; the pixel point of the image is determined by the spectral width of the laser signal, the dispersion coefficient of the dispersion medium and the sampling rate of the high-speed oscilloscope.
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| CN113624453A (en) * | 2021-07-30 | 2021-11-09 | 重庆大学 | Large-caliber optical element high-speed detection system based on ultrafast microscopic imaging |
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