Optical evanescent wave photoacoustic detection device

Abstract

The present invention discloses an optical evanescent wave photoacoustic detection device, comprising an excitation laser emission module, an excitation laser focusing module, a photoacoustic wave propagation module, a detection laser emission module, a beam splitting module, an optical evanescent wave generation module, a reference beam module, a beam combining module, and a photoacoustic signal acquisition module. The optical evanescent wave generation module receives a first p-polarized light beam and performs total internal reflection to generate an optical evanescent wave, and generates a new first p-polarized light beam based on the optical evanescent wave. The beam combining module combines the new first p-polarized light beam with a second p-polarized light beam to form an interference light beam. The photoacoustic signal acquisition module converts the light intensity change information of the interference light beam into a photoacoustic signal and stores it. The present invention uses a portion of the p-polarized detection laser to excite the optical evanescent wave and couple it to the photoacoustic wave. Because the optical evanescent wave has ultrafast time response characteristics and its phase change has high refractive index sensitivity, the structure can simultaneously have ultra-large bandwidth and ultra-high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of photoacoustic wave measurement, and in particular to an optical evanescent wave photoacoustic detection device. Background Art

[0002] Photoacoustic imaging technology, through the optical absorption imaging contrast mechanism, combines multiple advantages such as label-free observation, large penetration depth, and high spatial resolution, and has shown great application potential in the field of biomedical imaging, such as brain imaging, retinal imaging, and pathological imaging. In addition to providing one-dimensional depth resolution information for photoacoustic imaging, photoacoustic signals also carry photoacoustic spectrum information, that is, the frequency domain information of the photoacoustic signal, which can distinguish the microstructure of tissue samples. Analyzing photoacoustic signals in the frequency domain provides more opportunities for quantitatively evaluating the microstructural characteristics of biological tissues (including size, shape, orientation, and density). Therefore, by combining photoacoustic morphological imaging and photoacoustic spectrum analysis methods, it is possible to comprehensively analyze the information of each imaging pixel position of biological tissue from the perspectives of morphology and physical properties, and then determine characteristics such as tissue type, composition, and lesions.

[0003] Accurate photoacoustic signal measurement is the foundation of photoacoustic microscopy and photoacoustic spectroscopy. Because biological tissue has a low damage threshold to pulsed light energy, the pulse energy of photoacoustic excitation is typically limited to very low levels to ensure lossless imaging capabilities. Compared to the sound pressure radiated by traditional ultrasound transducers, the sound pressure of photoacoustic signals is 2-4 orders of magnitude lower. Furthermore, the size of biological particles within tissue is typically at the micron or even submicron level, and the corresponding photoacoustic waves have an ultra-wide spectral response, reaching hundreds of megahertz.

[0004] Currently, photoacoustic detection technology is commonly used in two ways. One method uses traditional piezoelectric ultrasonic transducers to detect photoacoustic signals. Although their acoustic detection sensitivity is high (tens of Pa), they are limited by the inherent properties of piezoelectric ultrasonic detectors and the inherent acoustic spectrum response bandwidth of the piezoelectric material. The acoustic response bandwidth is typically only ~30 MHz. This narrow detection bandwidth generally suffers from the drawback that the measured photoacoustic signal is actually the frequency domain filtering result of the original photoacoustic signal of the bioparticles, making it difficult to recover the true photoacoustic wave signal. The other method uses phase-type optical evanescent wave sensors to detect photoacoustic signals. Leveraging their ultrafast temporal response characteristics, phase-type evanescent wave sensors can increase the photoacoustic detection bandwidth to over 170 MHz. However, their noise equivalent pressure (NEP) sensitivity is only maintained at ~100 Pa, which is lower than the tens of Pa of ultrasonic transducers. This poor sensitivity of ultrasonic detection often causes some weaker photoacoustic signals to be submerged in the noise, making it impossible to accurately recover the true photoacoustic wave signal. Therefore, the existing photoacoustic detection technology has a technical bottleneck that cannot simultaneously achieve high sensitivity and large bandwidth photoacoustic detection, which easily causes signal detection distortion. Summary of the Invention

[0005] The embodiment of the present invention provides an optical evanescent wave photoacoustic detection device, which aims to solve the problem that the existing photoacoustic detection technology cannot simultaneously achieve high sensitivity and wide bandwidth photoacoustic detection, which easily causes signal detection distortion.

[0006] An embodiment of the present invention provides an optical evanescent wave photoacoustic detection device, which includes: an excitation laser emission module, an excitation laser focusing module, a photoacoustic wave propagation module, a detection laser emission module, a beam splitting module, an optical evanescent wave generation module, a reference beam module, a beam combining module, and a photoacoustic signal acquisition module;

[0007] The excitation laser emission module is used to emit pulsed laser to the excitation laser focusing module;

[0008] The excitation laser focusing module is used to return the pulsed laser and focus it on the biological tissue to be tested, so that the biological tissue to be tested generates photoacoustic waves;

[0009] The photoacoustic wave propagation module is used to propagate the photoacoustic wave to the optical evanescent wave generation module;

[0010] The detection laser emission module is used to generate a p-polarized detection laser beam;

[0011] The beam splitting module is used to split the p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam;

[0012] The optical evanescent wave generating module is configured to receive the first p-polarized light beam and perform total internal reflection to generate an optical evanescent wave, generate a new first p-polarized light beam based on the optical evanescent wave, and transmit the new first p-polarized light beam to the beam combining module; wherein the phase of the optical evanescent wave is perturbed by the photoacoustic wave to change the phase of the first p-polarized light beam, thereby obtaining the new first p-polarized light beam;

[0013] The reference beam module is used to transmit the second p-polarized beam to the beam combining module;

[0014] The beam combining module is used to combine the new first p-polarized light beam and the second p-polarized light beam and interfere with each other to form an interference light beam;

[0015] The photoacoustic signal acquisition module is used to convert the light intensity change information of the interference light beam into a photoacoustic signal and store it.

[0016] In one technical solution, the excitation laser emission module is a nanosecond pulse laser.

[0017] In one technical solution, the excitation laser focusing module includes a first reflector and an objective lens; the first reflector is used to return the pulsed laser to the objective lens; the objective lens is used to focus the pulsed laser on the biological tissue to be tested.

[0018] In one technical solution, the photoacoustic wave propagation module includes a placement component and a coupling medium; the placement component is used to place the coupling medium and the biological tissue to be tested; the coupling medium is used to couple the photoacoustic waves generated by the biological tissue to be tested to propagate the photoacoustic waves to the optical evanescent wave generation module.

[0019] In one technical solution, the detection laser emission module includes a helium-neon laser, a polarizer and a half-wave plate; the helium-neon laser is used to generate a detection laser beam; the polarizer is used to modulate the detection laser beam into a standard linearly polarized light; and the half-wave plate is used to adjust the polarization direction of the linearly polarized light to generate a p-polarized detection laser beam.

[0020] In one technical solution, the beam splitting module is a first beam splitter.

[0021] In one technical solution, the optical evanescent wave generating module includes a first prism and a second reflector; the first prism is used to receive the first p-polarized light beam and perform total internal reflection to generate an optical evanescent wave, and generate a new first p-polarized light beam based on the optical evanescent wave; the second reflector is used to reflect the new first p-polarized light beam to the beam combining module.

[0022] In one technical solution, the reference beam module includes a third reflector and a second prism; the third reflector is used to reflect the second p-polarized beam to the second prism; the second prism is used to receive the second p-polarized beam and perform total internal reflection to transmit the second p-polarized beam to the beam combining module.

[0023] In one technical solution, the beam combining module is a second beam splitter.

[0024] In one technical solution, the photoacoustic signal acquisition module includes a photodetector and an oscilloscope; the photodetector is used to convert the light intensity change information of the interference light beam into a photoacoustic signal; the oscilloscope is used to receive the photoacoustic signal transmitted by the photodetector, and display and store the photoacoustic signal.

[0025] An embodiment of the present invention provides an optical evanescent wave photoacoustic detection device, including an excitation laser emitting module, an excitation laser focusing module, a photoacoustic wave propagation module, a detection laser emitting module, a beam splitting module, an optical evanescent wave generating module, a reference beam module, a beam combining module and a photoacoustic signal acquisition module; the beam splitting module splits a p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam; the optical evanescent wave generating module receives the first p-polarized beam and performs total internal reflection to generate an optical evanescent wave, and generates a new first p-polarized beam based on the optical evanescent wave; the beam combining module forms an interference beam with the new first p-polarized beam and the second p-polarized beam; the photoacoustic signal acquisition module converts light intensity change information of the interference beam into a photoacoustic signal and stores it. The present invention uses a portion of p-polarized detection laser to excite optical evanescent waves and couple them with photoacoustic waves. Since the optical evanescent waves have ultrafast time response characteristics and their phase changes are highly sensitive to refractive index, they are combined with a second p-polarized light beam that is not coupled with the photoacoustic waves. This converts the phase changes of the optical evanescent waves caused by the photoacoustic disturbance into light intensity disturbances, which are detected by a high-speed photoacoustic signal acquisition module. This structure can simultaneously have ultra-large bandwidth and ultra-high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 A schematic block diagram of an optical evanescent wave photoacoustic detection device provided in one embodiment of the present invention;

[0028] Figure 2 A schematic diagram of the principle of an optical evanescent wave photoacoustic detection device provided by one embodiment of the present invention.

[0029] Wherein, description of the accompanying drawings:

[0030] 100. Excitation laser emission module; 110. Excitation laser focusing module; 120. Photoacoustic wave propagation module; 130. Detection laser emission module; 140. Beam splitting module; 150. Optical evanescent wave generation module; 160. Reference beam module; 170. Beam combining module; 180. Photoacoustic signal acquisition module; 1. Nanosecond pulse laser; 2. First reflector; 3. Objective lens; 4. Biological tissue to be measured; 5. Placement component; 6. Coupling medium; 7. Helium-neon laser; 8. Polarizer; 9. Half-wave plate; 10. First beam splitter; 11. First prism; 12. Second reflector; 13. Third reflector; 14. Second prism; 15. Second beam splitter; 16. Photodetector; 17. Oscilloscope; 18. Photoacoustic wave. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0032] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0033] It should also be understood that the terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should further be understood that the term "and / or" as used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, including and including these combinations.

[0034] See also Figures 1 to 2 , Figure 1 A schematic block diagram of an optical evanescent wave photoacoustic detection device provided in one embodiment of the present invention; Figure 2 A schematic diagram of the principle of an optical evanescent wave photoacoustic detection device provided by one embodiment of the present invention.

[0035] See Figure 1 and Figure 2The embodiment of the present invention provides an optical evanescent wave photoacoustic detection device, comprising: an excitation laser emitting module 100, an excitation laser focusing module 110, a photoacoustic wave propagation module 120, a detection laser emitting module 130, a beam splitting module 140, an optical evanescent wave generating module 150, a reference beam module 160, a beam combining module 170 and a photoacoustic signal acquisition module 180; the excitation laser emitting module 100 is used to emit a pulsed laser to the excitation laser focusing module 110; the excitation laser focusing module 110 is used to return and focus the pulsed laser on a biological tissue 4 to be tested, so that the biological tissue 4 to be tested generates a photoacoustic wave 18; the photoacoustic wave propagation module 120 is used to propagate the photoacoustic wave 18 to the optical evanescent wave generating module 150; the detection laser emitting module 130 is used to generate a p-polarized detection laser beam; the beam splitting module 140 is used to generate a p-polarized detection laser beam; 0 is used to divide the p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam; the optical evanescent wave generating module 150 is used to receive the first p-polarized beam and perform total internal reflection to generate an optical evanescent wave, generate a new first p-polarized beam according to the optical evanescent wave and transmit it to the beam combining module 170; wherein, the phase of the optical evanescent wave is disturbed by the photoacoustic wave 18 to change the phase of the first p-polarized beam to obtain the new first p-polarized beam; the reference beam module 160 is used to transmit the second p-polarized beam to the beam combining module 170; the beam combining module 170 is used to combine the new first p-polarized beam and the second p-polarized beam and interfere to form an interference beam; the photoacoustic signal acquisition module 180 is used to convert the light intensity change information of the interference beam into a photoacoustic signal and store it.

[0036] In this embodiment, the excitation laser emitting module 100 emits a pulsed laser to the excitation laser focusing module 110. The pulsed laser is used to excite the photoacoustic wave 18 of the biological tissue 4 to be tested. The excitation laser focusing module 110 returns the pulsed laser and focuses it on the biological tissue 4 to be tested, causing the biological tissue 4 to generate broadband photoacoustic waves 18. The biological tissue 4 to be tested is placed in the photoacoustic wave propagation module 120, so that the photoacoustic wave 18 generated by the biological tissue 4 to be tested is propagated to the optical evanescent wave generation module 150 through the photoacoustic wave propagation module 120. At the same time, the detection laser emitting module 130 generates a p-polarized detection laser beam and transmits the p-polarized detection laser beam to the beam splitting module 140. The beam splitting module 140 splits the p-polarized probe laser beam into a first p-polarized beam and a second p-polarized beam in a 1:1 ratio, wherein the first p-polarized beam and the second p-polarized beam have different propagation directions and equal energy. The beam splitting module 140 outputs the first p-polarized beam toward the optical evanescent wave generating module 150 and outputs the second p-polarized beam toward the reference beam module 160. The optical evanescent wave generating module 150 receives the first p-polarized beam and performs total internal reflection to generate an optical evanescent wave. The optical evanescent wave is used to couple with the photoacoustic wave 18, causing the phase of the optical evanescent wave to change under the action of the photoacoustic wave 18, thereby changing the phase of the first p-polarized beam. The phase-changed first p-polarized beam is used as a new first p-polarized beam, and the new first p-polarized beam is transmitted to the beam combining module 170. The reference beam module 160 transmits the second p-polarized beam to the beam combining module 170. The beam combining module 170 combines the new first p-polarized light beam and the second p-polarized light beam to form an interference beam, which is then transmitted to the photoacoustic signal acquisition module 180. Upon receiving the interference beam, the photoacoustic signal acquisition module 180 converts the light intensity variation information of the interference beam into a photoacoustic signal and stores it.

[0037] The optical evanescent wave photoacoustic detection device provided in an embodiment of the present invention adopts a Mach-Zehnder interferometer structure. A first p-polarized light beam is used to excite the optical evanescent wave and couple the photoacoustic wave 18, while a second p-polarized light beam is not coupled to the photoacoustic wave 18 (i.e., a portion of the p-polarized detection laser is used to excite the optical evanescent wave and couple the photoacoustic wave 18, while the other portion is not coupled to the photoacoustic wave 18). This allows the measured phase difference change to be solely that of the p-polarized light, which is relatively large. Furthermore, the introduction of the interference structure converts phase information into intensity information, thereby greatly improving sensitivity. Experimental verification has shown that, compared to a method of achieving photoacoustic detection based on phase changes between s- and p-polarized light when subjected to the same photoacoustic wave perturbation, the optical evanescent wave photoacoustic detection device of the present invention improves the sensitivity of photoacoustic detection by more than five times. The present invention uses a portion of p-polarized detection laser to excite an optical evanescent wave and couple it to a photoacoustic wave. Since the optical evanescent wave has ultrafast time response characteristics and its phase change has high refractive index sensitivity, it is combined with a second p-polarized light beam that is not coupled to the photoacoustic wave, thereby converting the phase change of the optical evanescent wave caused by the photoacoustic disturbance into a light intensity disturbance, which is detected by a high-speed photoacoustic signal acquisition module. This can simultaneously achieve highly sensitive and broadband photoacoustic signal measurement.

[0038] In a more specific embodiment, the excitation laser emission module 100 is a nanosecond pulse laser 1 .

[0039] In this embodiment, see Figure 1 and Figure 2 The excitation laser emitting module 100 can be specifically configured as a nanosecond pulse laser 1, which emits a pulsed laser to excite the biological tissue 4 to be tested to generate a photoacoustic wave 18. The wavelength of the pulsed laser can be any one of 1064nm, 532nm, and 266nm, or other wavelengths. Different wavelengths correspond to different samples of the excitation photoacoustic wave 18. For example, a wavelength of 532nm is generally used to excite the photoacoustic wave 18 of red blood cells, and a wavelength of 266nm is generally used to excite the photoacoustic wave 18 of cell nuclei. The wavelength of the pulsed laser is not specifically limited here.

[0040] In a more specific embodiment, the excitation laser focusing module 110 includes a first reflector 2 and an objective lens 3; the first reflector 2 is used to return the pulsed laser to reflect the pulsed laser to the objective lens 3; the objective lens 3 is used to focus the pulsed laser on the biological tissue 4 to be tested.

[0041] In this embodiment, see Figure 1 and Figure 2The excitation laser focusing module 110 is composed of a first reflector 2 and an objective lens 3. The first reflector 2 receives the pulsed laser emitted by the excitation laser emitting module 100 and reflects the pulsed laser back to the objective lens 3. The objective lens 3 focuses the pulsed laser on the biological tissue 4 to be tested, so that the biological tissue 4 to be tested generates broadband photoacoustic waves 18 under the action of the pulsed laser.

[0042] In a more specific embodiment, the photoacoustic wave propagation module 120 includes a placement component 5 and a coupling medium 6; the placement component 5 is used to place the coupling medium 6 and the biological tissue to be tested 4; the coupling medium 6 is used to couple the photoacoustic wave 18 generated by the biological tissue to be tested 4 to propagate the photoacoustic wave 18 to the optical evanescent wave generating module 150.

[0043] In this embodiment, see Figure 1 and Figure 2 The photoacoustic wave propagation module 120 is composed of a storage assembly 5 and a coupling medium 6. The coupling medium 6 is placed in the storage assembly 5, and the biological tissue 4 to be tested is placed in the coupling medium 6. When the biological tissue 4 to be tested is irradiated by a pulsed laser, a photoacoustic wave 18 is generated. The photoacoustic wave 18 propagates in the coupling medium 6, thereby propagating the photoacoustic wave 18 to the optical evanescent wave generation module 150. The coupling medium 6 can be a solid or liquid medium. Preferably, the coupling medium 6 is water.

[0044] In a more specific embodiment, the detection laser emission module 130 includes a helium-neon laser 7, a polarizer 8 and a half-wave plate 9; the helium-neon laser 7 is used to generate a detection laser beam; the polarizer 8 is used to modulate the detection laser beam into a standard linearly polarized light; the half-wave plate 9 is used to adjust the polarization direction of the linearly polarized light so as to generate a p-polarized detection laser beam.

[0045] In this embodiment, see Figure 1 and Figure 2 The detection laser emission module 130 is composed of a HeNe laser 7, a polarizer 8, and a half-wave plate 9. The HeNe laser 7 generates a detection laser beam and transmits it to the polarizer 8. The wavelength of the detection laser beam can be 532nm, 633nm, or 1064nm, etc., and is not specifically limited here. The detection laser beam is then modulated into standard linearly polarized light by the polarizer 8. The polarization direction of the linearly polarized light is then adjusted by the half-wave plate 9, so that the output beam from the half-wave plate 9 is a p-polarized detection laser beam.

[0046] In a more specific embodiment, the beam splitting module 140 is a first beam splitter 10 .

[0047] In this embodiment, see Figure 1 and Figure 2The beam splitting module 140 is configured as a first beam splitter 10 , and the first beam splitter 10 splits the p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam.

[0048] In a more specific embodiment, the optical evanescent wave generating module 150 includes a first prism 11 and a second reflector 12; the first prism 11 is used to receive the first p-polarized light beam and perform total internal reflection to generate an optical evanescent wave, and generate a new first p-polarized light beam based on the optical evanescent wave; the second reflector 12 is used to reflect the new first p-polarized light beam to the beam combining module 170.

[0049] In this embodiment, see Figure 1 and Figure 2 The optical evanescent wave generation module 150 is composed of a first prism 11 and a second reflector 12. The first prism 11 receives the first p-polarized light beam output by the beam splitting module 140 and performs total internal reflection, generating an optical evanescent wave. The phase of the optical evanescent wave is then disturbed and changed by the photoacoustic wave 18 transmitted from the photoacoustic wave propagation module 120, thereby changing the phase of the first p-polarized light beam and generating a new first p-polarized light beam. The second reflector 12 reflects the new first p-polarized light beam emitted by the first prism 11 to the beam combining module 170 for interference.

[0050] In one embodiment, a first prism 11 is disposed above the photoacoustic wave propagation module 120. One side of the first prism 11 receives a parallel incident first p-polarized light beam and refracts the first p-polarized light beam at a specific angle, causing the first p-polarized light beam to be incident on the lower surface of the first prism 11. At this time, the lower surface of the first prism 11 serves as the coupling medium 6 in the photoacoustic wave propagation module 120. The angle of incidence of the first p-polarized light beam on the lower surface of the first prism 11 is exactly the angle of total internal reflection, causing the light beam reflected by the other side of the first prism 11 to be a parallel light beam. The specific angle is slightly greater than the critical angle, which is determined based on the wavelength of the first p-polarized light beam. Alternatively, it can be understood that the critical angle is determined based on the wavelength of the detection laser beam generated by the HeNe laser 7 in the detection laser emission module 130. Furthermore, when the photoacoustic wave propagation module 120 propagates the photoacoustic wave 18 to the lower surface of the first prism 11, the refractive index of the coupling medium 6 on the lower surface of the first prism 11 changes, thereby causing the phase of the first p-polarized light beam to change. Furthermore, the excitation laser focusing module 110 is arranged above the first prism 11. The excitation laser focusing module 110 allows the pulsed laser to pass through the first prism 11 and focus on the biological tissue to be tested 4 placed in the photoacoustic wave propagation module 120, so that the excitation of the photoacoustic wave 18 and the detection of the photoacoustic wave 18 are both on the same side of the biological tissue to be tested 4, thereby being able to detect or image very thick biological tissue to be tested 4.

[0051] In a more specific embodiment, the reference beam module 160 includes a third reflector 13 and a second prism 14; the third reflector 13 is used to reflect the second p-polarized light beam to the second prism 14; the second prism 14 is used to receive the second p-polarized light beam and perform total internal reflection to transmit the second p-polarized light beam to the beam combining module 170.

[0052] In this embodiment, see Figure 1 and Figure 2 The reference beam module 160 is composed of a third reflector 13 and a second prism 14. The beam splitting module 140 outputs a second p-polarized light beam to the third reflector 13. The second p-polarized light beam is reflected by the third reflector 13 to the second prism 14. The second prism 14 then receives the second p-polarized light beam and performs total internal reflection, thereby transmitting the second p-polarized light beam to the beam combining module 170. Preferably, the second prism 14 and the first prism 11 have the same angle. Since the lower surface of the second prism 14 is air, the incident angle of the second p-polarized light beam incident on the lower surface of the second prism 14 is greater than the critical angle, which can achieve total internal reflection.

[0053] In a more specific embodiment, the beam combining module 170 is a second beam splitter 15 .

[0054] In this embodiment, see Figure 1 and Figure 2 The beam combining module 170 is configured as a second beam splitter 15, and the second beam splitter 15 combines the new first p-polarized light beam transmitted by the optical evanescent wave generating module 150 and the second p-polarized light beam transmitted by the test light beam module to interfere with each other, thereby forming an interference light beam, thereby converting the phase change of the optical evanescent wave generated by the disturbance of the photoacoustic wave 18 (that is, the phase change of the first p-polarized light beam) into a change in the intensity of the interference light.

[0055] In a more specific embodiment, the photoacoustic signal acquisition module 180 includes a photodetector 16 and an oscilloscope 17; the photodetector 16 is used to convert the light intensity change information of the interference light beam into a photoacoustic signal; the oscilloscope 17 is used to receive the photoacoustic signal transmitted by the photodetector 16, and display and store the photoacoustic signal.

[0056] In this embodiment, see Figure 1 and Figure 2The photoacoustic signal acquisition module 180 includes a photodetector 16 and an oscilloscope 17. Specifically, the photodetector 16 is in communication with the oscilloscope 17 via a BNC cable to achieve signal transmission. The photodetector 16 converts the intensity variation of the interference beam into a photoacoustic signal and transmits the photoacoustic signal to the oscilloscope 17. Upon receiving the photoacoustic signal transmitted by the photodetector 16, the oscilloscope 17 displays and stores the signal. Preferably, the oscilloscope can also be a combination of a computer (PC) and a data acquisition card for displaying and storing data.

[0057] The optical evanescent wave photoacoustic detection device provided by an embodiment of the present invention includes an excitation laser emitting module 100, an excitation laser focusing module 110, a photoacoustic wave propagation module 120, a detection laser emitting module 130, a beam splitting module 140, an optical evanescent wave generating module 150, a reference beam module 160, a beam combining module 170 and a photoacoustic signal acquisition module 180; the beam splitting module 140 splits the p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam; the optical evanescent wave generating module 150 receives the first p-polarized beam and performs total internal reflection to generate an optical evanescent wave, and generates a new first p-polarized beam according to the optical evanescent wave; the beam combining module 170 forms an interference beam with the new first p-polarized beam and the second p-polarized beam; the photoacoustic signal acquisition module 180 converts light intensity change information of the interference beam into a photoacoustic signal and stores it. The present invention uses a part of the p-polarized detection laser to excite the optical evanescent wave and couple the photoacoustic wave 18. Since the optical evanescent wave has ultrafast time response characteristics and its phase change has high refractive index sensitivity, it is combined with another part of the second p-polarized light beam that is not coupled with the photoacoustic wave, thereby converting the phase change of the optical evanescent wave of the photoacoustic disturbance into light intensity disturbance, which is detected by a high-speed photoacoustic signal acquisition module. Such a structure can have both ultra-large bandwidth and ultra-high sensitivity.

[0058] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. An optical evanescent wave photoacoustic detection device, characterized in that: include: Excitation laser emission module, excitation laser focusing module, photoacoustic wave propagation module, detection laser emission module, beam splitting module, optical evanescent wave generation module, reference beam module, beam combining module and photoacoustic signal acquisition module; The excitation laser emission module is used to emit pulsed laser to the excitation laser focusing module; The excitation laser focusing module is used to return the pulsed laser and focus it on the biological tissue to be tested, so that the biological tissue to be tested generates photoacoustic waves; The photoacoustic wave propagation module is used to propagate the photoacoustic wave to the optical evanescent wave generation module; The detection laser emission module is used to generate a p-polarized detection laser beam; The beam splitting module is used to split the p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam; The optical evanescent wave generating module is configured to receive the first p-polarized light beam and perform total internal reflection to generate an optical evanescent wave, generate a new first p-polarized light beam based on the optical evanescent wave, and transmit the new first p-polarized light beam to the beam combining module; wherein the phase of the optical evanescent wave is perturbed by the photoacoustic wave to change the phase of the first p-polarized light beam, thereby obtaining the new first p-polarized light beam; The reference beam module is used to transmit the second p-polarized beam to the beam combining module; The beam combining module is used to combine the new first p-polarized light beam and the second p-polarized light beam and interfere with each other to form an interference light beam; The photoacoustic signal acquisition module is used to convert the light intensity change information of the interference light beam into a photoacoustic signal and store it.

2. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The excitation laser emission module is a nanosecond pulse laser.

3. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The excitation laser focusing module includes a first reflecting mirror and an objective lens; The first reflecting mirror is used to return the pulse laser to reflect the pulse laser to the objective lens; The objective lens is used to focus the pulse laser on the biological tissue to be measured.

4. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The photoacoustic wave propagation module includes a placement component and a coupling medium; The placement component is used to place the coupling medium and the biological tissue to be tested; The coupling medium is used to couple the photoacoustic waves generated by the biological tissue to be measured, so as to propagate the photoacoustic waves to the optical evanescent wave generating module.

5. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The detection laser emission module includes a helium-neon laser, a polarizer and a half-wave plate; The helium-neon laser is used to generate a detection laser beam; The polarizer is used to modulate the detection laser beam into standard linear polarized light; The half-wave plate is used to adjust the polarization direction of the linearly polarized light so as to generate a p-polarized detection laser beam.

6. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The beam splitting module is a first beam splitter.

7. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The optical evanescent wave generating module includes a first prism and a second reflecting mirror; The first prism is used to receive the first p-polarized light beam and perform total internal reflection to generate an optical evanescent wave, and generate a new first p-polarized light beam according to the optical evanescent wave; The second reflector is used to reflect the new first p-polarized light beam to the beam combining module.

8. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The reference beam module includes a third reflector and a second prism; The third reflector is used to reflect the second p-polarized light beam to the second prism; The second prism is used to receive the second p-polarized light beam and perform total internal reflection to transmit the second p-polarized light beam to the beam combining module.

9. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The beam combining module is a second beam splitter.

10. The optical evanescent wave photoacoustic detection device according to claim 1, characterized in that: The photoacoustic signal acquisition module includes a photodetector and an oscilloscope; The photodetector is used to convert the light intensity change information of the interference light beam into a photoacoustic signal; The oscilloscope is used to receive the photoacoustic signal transmitted by the photodetector, and to display and store the photoacoustic signal.

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