Method and system for modulating speckle imaging through photo-thermal optical coherence tomography

Abstract

The invention relates to a method and a system for modulating speckle imaging through photo-thermal optical coherence tomography. The method for modulating speckle imaging through photo-thermal optical coherence tomography comprises the following steps that equipment is debugged, and a photo-thermal OCT system is made to be in a speckle modulation state; a sample is placed on a sample table, and a two-dimensional scanning galvanometer is started; low-coherence laser and pump light generated by the photo-thermal OCT system irradiate a sample at the same time, so that the sample is scattered under the photo-thermal effect, and sample light is obtained; the sample light interferes with the reference light to obtain interference light; the spectrograph detects the interference light to obtain an interference signal; and the processing equipment performs post-processing on the interference signal to obtain an imaging image. According to the method for modulating speckle imaging through photo-thermal optical coherence tomography, speckles are modulated through the photo-thermal effect, clearer microangiography imaging can be obtained, and the good imaging effect is achieved for microflow-velocity microvessels which are difficult to image in the prior art.

Description

Technical Field

[0001] The present invention relates to the fields of optical detection and biomedical engineering, and particularly to a method and system for photothermal optical coherence tomography modulated speckle imaging. Background Art

[0002] In the field of optical imaging, speckles are usually regarded as a special type of noise that interferes with the observer's accurate identification of useful signals. For Optical Coherence Tomography (OCT), the generation mechanism of speckles stems from the superposition of the backscattered light emitted by scatterers and the reference light due to random phases and amplitudes when the scatterers are randomly distributed. Although the speckle phenomenon will have an adverse impact on the imaging quality of OCT images to a certain extent, during the in-depth study of OCT technology, it is found that speckles actually contain rich tissue structure and blood flow velocity information, providing an effective observation means for microvascular angiography. However, imaging parameters such as speckle variance signals and correlation coefficient signals generated by blood flow are not friendly to microvascular angiography with low flow rates. These passive measurement methods have low sensitivity to microvessels with slow flow rates, resulting in discontinuous microvessels and large noise, thus affecting the quality of vascular network construction.

[0003] Photothermal Optical Coherence Tomograph (PT-OCT) is a new technology that combines the photothermal effect for imaging on the basis of OCT technology. The photothermal effect refers to the phenomenon that an object absorbs light energy and converts it into heat energy, resulting in a change in the refractive index of the object or elastic expansion, and then causing a change in the optical path difference. PT-OCT can generate high-contrast images by utilizing the characteristics of the photothermal effect. The red blood cells in microvessels have a photothermal effect on 532nm laser. Based on this characteristic, the method of modulating speckles with PT-OCT can improve the contrast of microvessels with low flow rates and capture more detailed and continuous microvascular angiograms. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a method and system for photothermal optical coherence tomography modulated speckle imaging.

[0005] A method for photothermal optical coherence tomography modulated speckle imaging includes the following steps:

[0006] S10. Debug the device to make the PT-OCT system in the modulated speckle state;

[0007] S20. Place the sample on the sample stage and turn on the two-dimensional scanning galvanometer;

[0008] S30. The low-coherence laser and the pump light generated by the photo-thermal OCT system are simultaneously irradiated on the sample, causing the sample to scatter under the action of the photo-thermal effect to obtain sample light;

[0009] S40. The sample light interferes with the reference light to obtain interference light;

[0010] S50. The spectrometer detects the interference light to obtain an interference signal;

[0011] S60. The processing device post-processes the interference signal to obtain an imaging image;

[0012] Among them, the interference signal received at time t can be expressed as:

[0013]

[0014] In the formula, S(k) represents the power spectrum corresponding to the light source, k represents the wave number, n represents the refractive index of the sample, R(z) represents the scattering coefficient of the sample at a specific depth, E R represents the reference light signal, E s represents the sample light signal, z represents the depth, 2(r + nz) represents the optical path of the sample light at the z depth, φ s represents the phase difference between the layers of the sample, φ PT represents the phase function.

[0015] In the method for photo-thermal optical coherence tomography modulated speckle imaging according to the present invention, according to the characteristic that hemoglobin has a photo-thermal effect on laser, the photo-thermal effect is excited by pump light for microvascular with micro flow rate, thereby generating a clearer speckle signal, and a clearer and higher-contrast microvascular angiography imaging can be obtained.

[0016] Further, the step S10 includes the following sub-steps:

[0017] S11. Turn on the broadband light source to obtain low-coherence laser;

[0018] S12. The low-coherence laser is split into two beams of low-coherence laser with a ratio of 1:1 and respectively enter the reference arm optical path and the sample arm optical path;

[0019] S13. Turn on the pump light laser and adjust the signal generator to obtain periodic pump light;

[0020] S14. Adjust the pump light and the low-coherence laser in the sample arm optical path to make them coaxial.

[0021] Further, the periodic pump light satisfies the following relational expression:

[0022]

[0023] In the formula, Ip0 represents the total intensity of the pump light, μ t represents the loss coefficient of the laser attenuation when penetrating the medium, and ω represents the modulation frequency.

[0024] The present invention also provides a system for photo-thermal optical coherence tomography modulation speckle imaging to implement the above-mentioned method for photo-thermal optical coherence tomography modulation speckle imaging, including a spectral domain OCT system, a pump laser, and a signal generator. The pump laser is connected to the signal generator and is used to irradiate a sample with pump light to cause a photo-thermal effect on the sample; the spectral domain OCT system is used to perform photo-thermal OCT imaging on the sample that has produced the photo-thermal effect.

[0025] Furthermore, the spectral domain OCT system includes a broadband light source, an optical fiber coupler, a reference arm optical path, a sample arm optical path, a spectrometer, and a processing device. The optical fiber coupler includes a first interface, a second interface, a third interface, and a fourth interface. The first interface is connected to the broadband light source, the second interface is connected to the reference arm optical path, the third interface is connected to the sample arm optical path, the fourth interface is connected to the spectrometer, and the processing device is connected to the spectrometer.

[0026] Furthermore, the reference arm optical path includes a reference arm fiber collimator, a reference arm focusing lens, and a mirror. The reference arm fiber collimator is connected to the second interface of the optical fiber coupler, and the reference arm focusing lens is arranged between the reference arm fiber collimator and the mirror and is used to focus the light beam emitted from the reference arm fiber collimator on the mirror.

[0027] Furthermore, the sample arm optical path includes a sample arm fiber collimator, a two-dimensional scanning galvanometer, a sample arm focusing lens, and a sample stage. The sample arm fiber collimator is connected to the third interface of the optical fiber coupler, the two-dimensional scanning galvanometer is used to reflect the light beam emitted from the sample arm fiber collimator onto the sample stage, and the sample arm focusing lens is arranged between the two-dimensional scanning galvanometer and the sample stage and is used to focus the light beam on the sample stage.

[0028] Furthermore, the sample arm optical path further includes a semi-reflective mirror, and the transmissive side of the semi-reflective mirror faces the pump laser, and the reflective side faces the sample arm fiber collimator.

[0029] Furthermore, the spectrometer includes a collimator, a phase holographic transmission grating, a spectrometer focusing lens, and a CCD camera. The collimator is connected to the fourth interface of the optical fiber coupler, the phase holographic transmission grating is used to split the light beam emitted from the collimator and then irradiate it onto the CCD camera, and the spectrometer focusing lens is arranged between the phase holographic transmission grating and the CCD camera and is used to focus the light beam on the CCD camera.

[0030] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of a photo-thermal optical coherence tomography modulated speckle imaging system;

[0032] Figure 2 It is a flow chart of a photo-thermal optical coherence tomography modulated speckle imaging method;

[0033] Figure 3 It is a microvascular imaging diagram obtained by using the photo-thermal OCT modulated speckle imaging method on a mouse ear;

[0034] Figure 4 It is a microvascular imaging diagram obtained by using the photo-thermal OCT modulated speckle imaging method on a mouse ear;

[0035] Figure 5 It is a melanoma imaging diagram obtained by using the photo-thermal OCT modulated speckle imaging method on a mouse ear. Detailed Embodiment

[0036] Please refer to Figure 1 , a system for photo-thermal optical coherence tomography modulated speckle imaging, comprising a spectral domain OCT system, a pump laser 70 and a signal generator 80. The pump light generated by the pump laser 70 is modulated by the signal generator 80 and then irradiated onto the sample to cause a photo-thermal effect on the sample. At the same time, the spectral domain OCT system performs OCT imaging on the sample, thereby obtaining photo-thermal OCT modulated speckle imaging.

[0037] The spectral domain OCT system includes a broadband light source 10, an optical fiber coupler 20, a reference arm optical path 30, a sample arm optical path 40, a spectrometer 50 and a processing device 60. The broadband light source 10 is a superluminescent diode, which is used to generate low-coherence laser with a central wavelength of 1310 nm and a bandwidth of 50 nm. The optical fiber coupler 20 includes four interfaces, namely a first interface, a second interface, a third interface and a fourth interface. The first interface is connected to the broadband light source 10 through an optical fiber, the second interface is connected to the reference arm optical path 30 through an optical fiber, the third interface is connected to the sample arm optical path 40 through an optical fiber, and the fourth interface is connected to the spectrometer 50 through an optical fiber. After the low-coherence laser generated by the broadband light source 10 enters the optical fiber coupler 20 through the first interface, it is split into two beams of low-coherence laser with a ratio of 1:1, and respectively enter the reference arm optical path 30 and the sample arm optical path 40 through the second interface and the third interface.

[0038] The reference arm optical path 30 includes a reference arm fiber collimator 31, a reference arm focusing lens 32, and a mirror 33. The reference arm fiber collimator 31 is connected to the second interface of the fiber coupler 20 through an optical fiber, so that the low-coherence laser light emitted from the second interface irradiates on the mirror 33. The reference arm focusing lens 32 is arranged between the reference arm fiber collimator 31 and the mirror 33, and is used for focusing the low-coherence laser light on the mirror 33. The mirror 33 reflects the low-coherence laser light along the original optical path to form reference light, and the reference light enters the fiber coupler 20 through the reference arm fiber collimator 31 and the second interface.

[0039] The sample arm optical path 40 includes a sample arm fiber collimator 41, a two-dimensional scanning galvanometer 42, a sample arm focusing lens 43, and a sample stage 44. The sample arm fiber collimator 41 is connected to the third interface of the fiber coupler 20 through an optical fiber, so that the low-coherence laser light emitted from the third interface irradiates on the sample stage 44 through the two-dimensional scanning galvanometer 42. The sample arm focusing lens 43 is arranged between the sample arm fiber collimator 41 and the sample stage 44, and is used for focusing the low-coherence laser light on the sample stage 44. The sample stage 44 is used for placing the sample to be imaged, and the two-dimensional scanning galvanometer 42 is used for changing the propagation path of the low-coherence laser light, so as to change the position where the low-coherence laser light is focused, and realize the scanning of different positions of the sample. The low-coherence laser light irradiates on the sample and scatters to form sample light, and the sample light enters the fiber coupler 20 along the original optical path of the low-coherence laser light through the sample arm focusing lens 43, the sample arm fiber collimator 41, and the third interface.

[0040] After the reference light and the sample light enter the fiber coupler 20, they interfere with each other in the fiber coupler 20 to form interference light, and the interference light enters the spectrometer 50 through the fourth interface. The spectrometer 50 includes a collimator 51, a phase holographic transmission grating 52, a spectrometer focusing lens 53, and a CCD camera 54. The collimator 51 is connected to the fourth interface of the fiber coupler 20, so that the interference light emitted from the fourth interface irradiates on the phase holographic transmission grating 52. The phase holographic transmission grating 52 disperses the interference light and then irradiates it on the CCD camera 54. The spectrometer focusing lens 53 is arranged between the phase holographic transmission grating 52 and the CCD camera 54, and is used for focusing the interference light on the CCD camera 54.

[0041] The processing device 60 is electrically connected to the CCD camera 54, and is used for receiving and processing the optical signal acquired by the CCD camera 54.

[0042] The pump laser 70 is used to generate pump light with a wavelength of 532 nm. The signal generator 80 is connected to the pump laser 70 and is used to generate a sine wave signal to modulate the pump light. The modulated pump light is coaxial with the low-coherence laser irradiated on the sample, and they jointly irradiate the sample, so that the sample scatters the low-coherence laser under the action of the photo-thermal effect to generate sample light.

[0043] Preferably, a semi-reflective mirror 45 is further provided on the optical path 40 of the sample arm. The pump laser 70 forms a 90° angle with the optical path 40 of the sample arm. The semi-reflective mirror 45 is arranged at the intersection of the pump light and the optical path 40 of the sample arm, and the angles with both of them are 45°. The transmissive side faces the pump light optical path, and the reflective side faces the optical path 40 of the sample arm. In use, the pump light passes through the semi-reflective mirror 45 and irradiates the sample, and the low-coherence laser emitted from the second interface is reflected by the semi-reflective mirror 45 onto the sample. The pump light and the low-coherence laser jointly act on the sample to obtain sample light. The sample light is reflected back to the second interface by the semi-reflective mirror 45 along the original optical path of the low-coherence laser and enters the fiber coupler 20.

[0044] Please refer to Figure 2 , based on the above system of photo-thermal optical coherence tomography modulation speckle imaging, the present embodiment further provides a method for photo-thermal optical coherence tomography modulation speckle imaging, including the following steps:

[0045] S10. Debug the device to make the photo-thermal OCT system in the modulation speckle state.

[0046] Specifically, it includes the following sub-steps:

[0047] S11. Turn on the broadband light source to obtain low-coherence laser.

[0048] S12. The low-coherence laser enters the fiber coupler and is split into two beams of low-coherence laser with a ratio of 1:1, namely the first laser and the second laser. The first laser enters the reference arm optical path, and the second laser enters the sample arm optical path.

[0049] S13. Turn on the pump light laser and adjust the signal generator to obtain periodic pump light.

[0050] Specifically, the relationship between the intensity of the pump light and time can be expressed as:

[0051]

[0052] In the formula, I p0 represents the total intensity of the pump light, μ tThe loss coefficient representing the attenuation of the laser when penetrating the medium, and ω represents the modulation frequency, which can be adjusted in real time according to actual needs for clearer imaging to be obtained subsequently.

[0053] S14. Adjust the focusing lens to make the pump light and the second laser coaxial.

[0054] In this embodiment, a black iron plate is used as a sample and placed on the sample stage, and the two-dimensional scanning galvanometer is turned off so that the pump light and the second laser are focused on the same point of the black iron plate. Collect the spectral information of the laser, draw a two-dimensional spectrogram of the spectrum and time, judge the coaxial situation according to the peak data of the spectrogram, and adjust the focusing lens in real time. When the peak reaches the maximum, the coaxiality is completed.

[0055] S20. Place the sample on the sample stage and turn on the two-dimensional scanning galvanometer.

[0056] When the two-dimensional scanning galvanometer is turned on, the two-dimensional scanning galvanometer will change the positions where the pump light and the second laser irradiate on the sample, thereby irradiating different positions of the sample to achieve scanning imaging of a certain area of the sample.

[0057] S30. The second laser and the pump light irradiate the sample simultaneously. The pump light causes a photothermal effect at the irradiated part, and the second laser causes scattering at this part to obtain sample light.

[0058] S40. The first laser is reflected by a mirror in the reference light optical path and returns along the original optical path to the fiber coupler to form reference light; at the same time, the sample light returns to the fiber coupler along the original optical path of the second laser and interferes with the reference light to obtain interference light.

[0059] S50. The interference light enters the spectrometer from the fiber coupler, and the spectrometer detects the interference light to obtain an interference signal.

[0060] S60. The processing device post-processes the interference signal to obtain a coherent image.

[0061] Specifically, the interference signal received at time t can be expressed as:

[0062]

[0063] In the formula, S(k) represents the power spectrum corresponding to the light source, k represents the wave number, n represents the refractive index of the sample, R(z) represents the scattering coefficient of the sample at a specific depth, and E R represents the reference light signal, and E s represents the sample light signal, z represents the depth, 2(r + nz) represents the optical path of the sample light at the z depth, φ s represents the phase difference between the layers of the sample, and φ PT represents the phase function.

[0064] Among them, under the action of the photo-thermal effect, the phase function φ PT has the following variation relationship:

[0065]

[0066] In the formula, f(z) is a function related to the depth z, and λ0 represents the wavelength of the low-coherence laser, which is 1310 nm in this embodiment.

[0067] Let A(z) = 2E R E s R(z), A s (z) = A(z)A * (z′). Perform Fourier transform on I(z, t) in the k direction and take the amplitude value. Then, the variation relationship of the speckle signal intensity affected by the photo-thermal effect with time is as follows:

[0068]

[0069] Since A(z) >> A s (z), the expression of the speckle signal intensity can be simplified to:

[0070]

[0071] I(z, t) = A(z) + A s (z)cos(φ PT - φ s )

[0072] According to the above interference signal expression, performing algorithms such as Fourier transform can draw the corresponding coherence image.

[0073] Exemplarily, in order to further illustrate the technical effect of the present invention, this embodiment also provides the experimental results of using a mouse ear as a sample.

[0074] Please refer to Figure 3 , which is a microvascular angiography imaging diagram of a local part of a mouse ear, and the imaging frequency range is 374.4 Hz - 655.2 Hz. Figure 3 a is the spectral domain OCT imaging diagram without photo-thermal effect, Figure 3 b is the photo-thermal OCT modulation speckle imaging diagram with the pump light modulation frequency of 500 Hz, Figure 3 c is the photo-thermal OCT modulation speckle imaging diagram with the pump light modulation frequency of 1000 Hz, Figure 3 d is the photo-thermal OCT modulation speckle imaging diagram with the pump light modulation frequency of 1500 Hz; Figure 3 e - h are respectively Figure 3Cross-sectional view of the white dashed lines in a-d. Obviously, compared with the ordinary spectral-domain OCT imaging, the photo-thermal OCT modulated speckle imaging can show a richer microvascular image, and the imaging details of the microvessels are the richest at a modulation frequency of 500 Hz. This is because the imaging frequency range is 374.4 Hz - 655.2 Hz, and 500 Hz is exactly within this frequency range.

[0075] Please refer to Figure 4 , which is a microvascular angiography image of a local part of a mouse ear, and the imaging frequency range is 748.8 Hz - 1123.2 Hz. Figure 4 a is a spectral-domain OCT imaging without photo-thermal effect, Figure 4 b is a photo-thermal OCT modulated speckle imaging with a pump light modulation frequency of 500 Hz, Figure 4 c is a photo-thermal OCT modulated speckle imaging with a pump light modulation frequency of 1000 Hz, Figure 4 d is a photo-thermal OCT modulated speckle imaging with a pump light modulation frequency of 1500 Hz; Figure 4 e-h are respectively Figure 4 Cross-sectional view of the white dashed lines in a-d. Obviously, compared with the ordinary spectral-domain OCT imaging, the photo-thermal OCT modulated speckle imaging can also show a richer microvascular image, and the imaging details are richer at a modulation frequency of 1000 Hz. This is because the imaging frequency range is adjusted to 748.8 Hz - 1123.2 Hz, and the corresponding optimal modulation frequency is also changed to 1000 Hz.

[0076] Moreover, the imaging method described in the present invention can not only be applied to microvascular angiography imaging, but also has a good imaging effect on other biological tissues sensitive to photo-thermal effect. For example, melanin can also generate photo-thermal effect under the action of a 532 nm pump light, so it can also be used for the detection of melanoma.

[0077] Please refer to Figure 5 , which is an image for the detection of melanoma in a mouse ear. Figure 5 a is a physical image of a mouse ear. The red frame in the figure is the melanoma implantation area, and the white frame is the photo-thermal OCT scanning imaging area; Figure 5 b is an HE staining section image of melanocytes in a mouse ear; Figure 5 c is a cross-sectional image of the white frame area before implanting melanoma; Figure 5 d is a cross-sectional image of the white frame area 30 days after implanting melanoma; Figure 5 e is Figure 5 A partial enlarged image of d. It can be seen from the image that Figure 5 The melanoma in the red frame area of a is visible to the naked eye, while there is no obvious abnormality visible to the naked eye in the white frame area. However, Figure 5d indicates signs of melanoma metastasis in this area, that is to say, photo-thermal OCT modulated speckle imaging can detect early melanoma in a timely manner.

[0078] Compared with the prior art, the photo-thermal OCT modulated speckle imaging method described in the present invention uses the photo-thermal effect to modulate the speckle, enabling clear imaging of microvascular structures with micro-flow velocities and melanoma, etc., which are difficult to clearly image in the prior art, and also having good contrast with large structures such as the background and large blood vessels.

[0079] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and the present invention is also intended to include these modifications and variations.

Claims

1. A method for photo-thermal optical coherence tomography modulated speckle imaging, characterized in that: It includes the following steps: S10. Debug the device to make the photo-thermal OCT system in the modulated speckle state; S20. Place the sample on the sample stage and turn on the two-dimensional scanning galvanometer; S30. The low-coherence laser and the pump light generated by the photo-thermal OCT system irradiate the sample simultaneously, causing the sample to scatter under the action of the photo-thermal effect to obtain sample light; S40. The sample light interferes with the reference light to obtain interference light; S50. The spectrometer detects the interference light to obtain an interference signal; S60. The processing device post-processes the interference signal to obtain an imaging image; Among them, the interference signal received at time t can be expressed as: Wherein, S(k) represents the power spectrum corresponding to the light source, k represents the wave number, n represents the refractive index of the sample, R(z) represents the scattering coefficient of the sample at a specific depth, E R represents the reference optical signal, E s represents the sample optical signal, z represents the depth, 2(r + nz) represents the optical path of the sample light at the z depth, φ s represents the phase difference between the layers of the sample, φ OT represents the phase function.

2. The method of photothermal optical coherence tomography modulated speckle imaging according to claim 1, characterized in that: The step S10 includes the following sub-steps: S11. Turn on the broadband light source to obtain a low-coherence laser; S12. The low-coherence laser is split into two beams of low-coherence laser with a ratio of 1:1 and enter the reference arm optical path and the sample arm optical path respectively; S13. Turn on the pump light laser and adjust the signal generator to obtain a periodic pump light; S14. Adjust the pump light and the low-coherence laser in the sample arm optical path to make them coaxial.

3. The method for photo-thermal optical coherence tomography modulated speckle imaging according to claim 2, wherein: The periodic pump light satisfies the following relational expression: where I p0 represents the total intensity of the pump light, and μ t represents the loss coefficient of the laser attenuation when penetrating the medium, and ω represents the modulation frequency.

4. A system for photo-thermal optical coherence tomography modulated speckle imaging, which is used to implement the method for photo-thermal optical coherence tomography modulated speckle imaging according to any one of claims 1-3, characterized in that: It includes a spectral domain OCT system, a pump laser and a signal generator. The pump laser is connected to the signal generator and is used to irradiate the sample with pump light to cause a photo-thermal effect on the sample; the spectral domain OCT system is used for photo-thermal OCT imaging of the sample that generates the photo-thermal effect.

5. The system for photo-thermal optical coherence tomography modulated speckle imaging according to claim 4, wherein: The spectral domain OCT system includes a broadband light source, an optical fiber coupler, a reference arm optical path, a sample arm optical path, a spectrometer and a processing device. The optical fiber coupler includes a first interface, a second interface, a third interface and a fourth interface. The first interface is connected to the broadband light source, the second interface is connected to the reference arm optical path, the third interface is connected to the sample arm optical path, the fourth interface is connected to the spectrometer, and the processing device is connected to the spectrometer.

6. The system for photo-thermal optical coherence tomography modulated speckle imaging according to claim 5, characterized in that: The reference arm optical path includes a reference arm fiber collimator, a reference arm focusing lens and a reflector. The reference arm fiber collimator is connected to the second interface of the optical fiber coupler. The reference arm focusing lens is arranged between the reference arm fiber collimator and the reflector and is used to focus the beam emitted by the reference arm fiber collimator on the reflector.

7. The system for photo-thermal optical coherence tomography modulated speckle imaging according to claim 6, wherein: The sample arm optical path includes a sample arm fiber collimator, a two-dimensional scanning galvanometer, a sample arm focusing lens and a sample stage. The sample arm fiber collimator is connected to the third interface of the optical fiber coupler. The two-dimensional scanning galvanometer is used to reflect the beam emitted by the sample arm fiber collimator onto the sample stage. The sample arm focusing lens is arranged between the two-dimensional scanning galvanometer and the sample stage and is used to focus the beam on the sample stage.

8. The system for photo-thermal optical coherence tomography modulated speckle imaging according to claim 7, wherein: The sample arm optical path further includes a semi-reflecting mirror. The side with transmissivity of the semi-reflecting mirror faces the pump laser, and the side with reflectivity faces the sample arm fiber collimator.

9. The system for photo-thermal optical coherence tomography modulated speckle imaging according to claim 8, wherein: The spectrometer includes a collimator, a phase holographic transmission grating, a spectrometer focusing lens, and a CCD camera. The collimator is connected to the fourth interface of the fiber optic coupler. The phase holographic transmission grating is configured to split the outgoing light of the collimator and irradiate it onto the CCD camera. The spectrometer focusing lens is disposed between the phase holographic transmission grating and the CCD camera and is used to focus the light beam on the CCD camera.

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