Optical evanescent wave photoacoustic detection device

Abstract

The invention discloses an optical evanescent wave photoacoustic detection device which comprises 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 the first p polarized light beam, performs total internal reflection to generate an optical evanescent wave, and generates a new first p polarized light beam according to the optical evanescent wave; the beam combining module combines the new first p polarized light beam and the second p polarized light beam to form an interference light beam; and the photoacoustic signal acquisition module converts the light intensity change information of the interference light beam into a photoacoustic signal and stores the photoacoustic signal. Part of p polarization detection laser is used for exciting optical evanescent waves and coupling photoacoustic waves, the optical evanescent waves have the ultrafast time response characteristic, and the phase change of the optical evanescent waves has the high refractive index sensitive characteristic, so that the structure can have the ultra-large bandwidth and the ultra-high sensitivity at the same time.

Description

Technical Field

[0001] The 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 uses the optical absorption imaging contrast mechanism, combined with 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 photoacoustic signals, which can distinguish the microstructure of tissue samples. Analyzing photoacoustic signals in the frequency domain provides more opportunities for quantitative evaluation of the microstructural characteristics of biological tissues (including size, shape, orientation, and density, etc.). Therefore, combining photoacoustic morphological imaging and photoacoustic spectrum analysis methods, the information of each imaging pixel position of biological tissues can be comprehensively analyzed from the perspectives of morphology and physical properties, and then the characteristics such as tissue type, composition, and lesions can be determined.

[0003] Accurate photoacoustic signal measurement is the basis of photoacoustic microscopy and photoacoustic spectroscopy. Since biological tissues have a low damage threshold to pulsed light energy, the pulse energy of photoacoustic excitation is usually limited to a very low level to ensure lossless imaging capabilities. Compared with the sound pressure radiated by traditional ultrasonic transducers, the sound pressure of photoacoustic signals is 2-4 orders of magnitude lower. In addition, the size of biological particles in tissues is usually at the micron or even submicron level, and the corresponding photoacoustic waves have an ultra-wide spectral response that can reach hundreds of megahertz.

[0004] At present, there are usually two ways of photoacoustic detection technology. One of them is to use traditional piezoelectric ultrasonic transducers to detect photoacoustic signals. Although its acoustic detection sensitivity is high (tens of Pa level), it is limited by the inherent properties of piezoelectric ultrasonic detectors and the acoustic spectrum response bandwidth of piezoelectric materials. The acoustic response bandwidth is usually only ~30MHz. There is a common defect of narrow detection bandwidth, which leads to the measured photoacoustic signal being the frequency domain filtering result of the original photoacoustic signal of biological particles, and it is difficult to restore the real photoacoustic wave signal. Another way is to use phase-type optical evanescent wave sensors to detect photoacoustic signals. Phase-type optical evanescent wave sensors use their ultra-fast time response characteristics to increase the bandwidth of photoacoustic detection to more than 170MHz. However, its noise equivalent sound pressure (NEP) sensitivity can only be maintained at ~100Pa level, which is lower than the tens of Pa level of ultrasonic transducers. The sensitivity of ultrasonic detection is poor, so that some weaker photoacoustic signals are usually submerged in noise and cannot be accurately restored. Therefore, the existing photoacoustic detection technology has a technical bottleneck that cannot achieve high sensitivity and wide bandwidth photoacoustic detection at the same time, which easily causes the problem of 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] The 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 used 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 according to the optical evanescent wave and transmit it to the beam combining module; wherein the phase of the optical evanescent wave is disturbed 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 to interfere with each other, so as 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 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 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 generating 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; 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, comprising 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 according to 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 part of p-polarized detection laser to excite optical evanescent waves and couple photoacoustic waves. Since the optical evanescent waves have ultrafast time response characteristics and their phase changes have high refractive index sensitivity, they are combined with another part of a second p-polarized light beam that is not coupled with the photoacoustic waves, thereby converting the phase change of the optical evanescent wave disturbed by the photoacoustic 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0029] Wherein, the accompanying drawings are described as follows:

[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 tested; 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. Photoelectric detector; 17. Oscilloscope; 18. Photoacoustic wave. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

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

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

[0035] See also 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 generation 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 the pulsed laser and focus it 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 generation 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 with each other 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, and 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, so that the biological tissue 4 to be tested generates a broadband photoacoustic wave 18, wherein 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 emits the p-polarized detection laser beam to the beam splitting module 140. The beam splitting module 140 splits the p-polarized detection laser beam into a first p-polarized beam and a second p-polarized beam in a ratio of 1:1, wherein the first p-polarized beam and the second p-polarized beam have different propagation directions and equal energies, and the beam splitting module 140 outputs the first p-polarized beam to the direction of the optical evanescent wave generating module 150, and outputs the second p-polarized beam to the direction of the reference beam module 160. The optical evanescent wave generating module 150 receives the first p-polarized beam and performs total internal reflection, thereby generating an optical evanescent wave, which is used to couple the photoacoustic wave 18, so that the phase of the optical evanescent wave changes under the action of the photoacoustic wave 18, thereby changing the phase of the first p-polarized beam, and using the first p-polarized beam with the changed phase as a new first p-polarized beam, and transmitting the new first p-polarized beam 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 interfere with each other to form an interference light beam, and transmits the interference light beam to the photoacoustic signal acquisition module 180. When the photoacoustic signal acquisition module 180 receives the interference light beam, it converts the light intensity change information of the interference light beam into a photoacoustic signal and stores it.

[0037] The optical evanescent wave photoacoustic detection device provided by the embodiment of the present invention adopts a Mach-Zehnder interferometer structure, and the first p-polarized light beam is used to excite the optical evanescent wave and couple the photoacoustic wave 18, while the second p-polarized light beam is not coupled to the photoacoustic wave 18 (that is, a part of the p-polarized detection laser is used to excite the optical evanescent wave and couple the photoacoustic wave 18, and the other part is not coupled to the photoacoustic wave 18), so that the measured phase difference change is only the phase difference change of the p-polarized light, the phase difference change is large, and the introduction of the interference structure converts the phase information into intensity information, thereby greatly improving the sensitivity. It can be verified experimentally that compared with the method of realizing photoacoustic detection based on the phase change generated by s and p polarized light when disturbed by the same photoacoustic wave, the optical evanescent wave photoacoustic detection device of the present invention improves the sensitivity of photoacoustic detection by more than 5 times. The present invention uses a part of p-polarized detection laser to excite optical evanescent waves and couple photoacoustic waves. Since the optical evanescent waves have ultrafast time response characteristics and their phase changes have high refractive index sensitivity, they are combined with another part of a second p-polarized light beam that is not coupled with the photoacoustic waves, thereby converting the phase change of the optical evanescent waves disturbed by the photoacoustic into light intensity disturbance, which is detected by a high-speed photoacoustic signal acquisition module, and can simultaneously achieve high-sensitivity 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 emission module 100 can be specifically configured as a nanosecond pulse laser 1, which emits a pulse laser to excite the biological tissue 4 to generate a photoacoustic wave 18. The wavelength of the pulse laser can be any one of 1064nm, 532nm, and 266nm, or other wavelengths. Different wavelengths correspond to different samples of the exciting photoacoustic wave 18. For example, a wavelength of 532nm is usually used to excite the photoacoustic wave 18 of red blood cells, and 266nm is usually used to excite the photoacoustic wave 18 of the cell nucleus. The wavelength of the pulse 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 pulse laser to reflect the pulse laser to the objective lens 3; the objective lens 3 is used to focus the pulse 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, wherein the first reflector 2 receives the pulse laser emitted by the excitation laser emitting module 100 and returns the pulse laser to the objective lens 3. The objective lens 3 focuses the pulse 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 pulse 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 placement component 5 and a coupling medium 6. The coupling medium 6 is placed in the placement component 5. 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 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 helium-neon laser 7, a polarizer 8 and a half-wave plate 9. The detection laser beam is generated by the helium-neon laser 7 and emitted to the polarizer 8, wherein the wavelength of the detection laser beam can be 532nm, 633nm or 1064nm, etc., which is not specifically limited here. Then, the detection laser beam is modulated into a standard linear polarized light by the polarizer 8, and then the polarization direction of the linear polarized light is adjusted by the half-wave plate 9, so that the output beam of 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 generating 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 to generate an optical evanescent wave. Then, the phase of the optical evanescent wave is 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, thereby obtaining 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, the first prism 11 is arranged above the photoacoustic wave propagation module 120, and one side of the first prism 11 receives the parallel incident first p-polarized light beam, and refracts the first p-polarized light beam at a specific angle, so that the first p-polarized light beam is incident on the lower surface of the first prism 11. At this time, the lower surface of the first prism 11 is the coupling medium 6 in the photoacoustic wave propagation module 120, and the incident angle of the first p-polarized light beam incident on the lower surface of the first prism 11 is just the total internal reflection angle, so that the light beam reflected by the other side of the first prism 11 is just a parallel light beam. Among them, the specific angle is slightly larger than the critical angle, and the critical angle is determined according to the wavelength of the first p-polarized light beam, which can also be understood as the critical angle is determined according to the wavelength of the detection laser beam generated by the helium-neon laser 7 in the detection laser emission module 130. In addition, 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 will change, 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 4 to be tested 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 4 to be tested, thereby being able to detect or image very thick biological tissue 4 to be tested.

[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 beam to the second prism 14; the second prism 14 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 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, wherein the beam splitting module 140 outputs a second p-polarized beam to the third reflector 13, the second p-polarized beam is reflected to the second prism 14 through the third reflector 13, and then the second prism 14 receives the second p-polarized beam and performs total internal reflection, thereby transmitting the second p-polarized beam to the beam combining module 170. Preferably, the second prism 14 has the same angle as the first prism 11, and since the lower surface of the second prism 14 is air, the incident angle of the second p-polarized beam incident on the lower surface of the second prism 14 is greater than the critical angle, and total internal reflection can be achieved.

[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 and interferes 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 form an interference light beam, thereby converting the phase change of the optical evanescent wave generated by the disturbance of the photoacoustic wave 18 (i.e., 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 connected to the oscilloscope 17 in communication. The photodetector 16 is connected to the oscilloscope 17 via a BNC line to achieve signal transmission. The photodetector 16 converts the light intensity change information of the interference light beam into a photoacoustic signal, and transmits the photoacoustic signal to the oscilloscope 17. The oscilloscope 17 receives the photoacoustic signal transmitted by the photodetector 16, and then displays and stores the photoacoustic 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 in 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 the light intensity change information of the interference beam into a photoacoustic signal and stores it. The present invention uses a part of p-polarized detection laser to excite optical evanescent waves and couple photoacoustic waves 18. Since the optical evanescent waves have ultrafast time response characteristics and their phase changes have high refractive index sensitivity, they are combined with another part of the second p-polarized light beam that is not coupled with the photoacoustic waves, 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 only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope 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 used 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 according to the optical evanescent wave and transmit it to the beam combining module; wherein the phase of the optical evanescent wave is disturbed 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 to interfere with each other, so as 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 pulsed laser to reflect the pulsed laser to the objective lens; The objective lens is used to focus the pulse laser on the biological tissue to be tested.

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 comprises 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.

Images