CN205826515U - Acoustical signal detector based on surface wave and reflecting light sonomicroscope - Google Patents

Abstract

The utility model is applicable to the technical field of photoacoustic imaging and sound pressure detection, and provides an acoustic signal detector based on surface waves and a reflective photoacoustic microscope. The acoustic signal detector includes a prism with two parallel planes, so One of the two parallel planes is coated with a thin film, and the thin film is used to detect photoacoustic signals transmitted through the medium. Because the acoustic signal detector adopts the method of optically sensing the refractive index, the object to be measured has the characteristics of marking-free and non-contact sensing detection, and can realize the advantages of detection bandwidth and detection sensitivity. Applying this surface wave-based acoustic signal detector to a reflective photoacoustic microscope can realize the imaging detection of living organisms.

Description

Surface wave based acoustic signal detector and reflective photoacoustic microscope

technical field

The utility model belongs to the technical field of photoacoustic imaging sound pressure detection, in particular to a surface wave-based acoustic signal detector and a reflective photoacoustic microscope.

Background technique

It is the current mainstream to use the piezoelectric method (the instrument is called an ultrasonic transducer) to extract the sound pressure signal. Many research groups use piezoelectric detectors for photoacoustic imaging research and have achieved fruitful research results. Although the technology is relatively mature and has a wide range of applications, it also has some shortcomings that are difficult to overcome. For example, this technology cannot achieve high sensitivity and high frequency detection at the same time. Using piezoelectric crystals to receive ultrasonic signals, the sensitivity and the receiving frequency are contradictory. The smaller the area of the piezoelectric crystal, the higher the receiving frequency, and the correspondingly lower sensitivity. Piezoelectric detectors cannot achieve point detection, and the detected signal is the average effect of the piezoelectric crystal area. The use of piezoelectric crystals to pick up photoacoustic signals must be between the sample and the probe. Restricted by the properties of piezoelectric materials, ultrasonic transducers generally have narrow detection bandwidth (about 40-60MHz) and low sensitivity (noise equivalent Sound pressure: hundreds to thousands of Pa) shortcomings.

Utility model content

The technical problem to be solved by the utility model is to provide a surface wave-based acoustic signal detector and a reflective photoacoustic microscope, aiming at solving the problem of narrow detection bandwidth of existing detectors.

The utility model is achieved in that a surface wave based acoustic signal detector comprises a prism with two parallel planes, one of the two parallel planes is coated with a thin film, and the thin film is It is used to detect the photoacoustic signal transmitted through the medium.

Further, the film is a metal film or a graphene film.

The utility model also provides an acoustic signal detector based on surface waves, which includes a multimode optical fiber, the multimode optical fiber includes a cladding and a core placed in the cladding, and the core of the multimode optical fiber has a The cross-section parallel to the extending direction of the multimode optical fiber, the cladding has a gap that exposes the cross-section outside the cladding, the cross-section is located at the gap, and the cross-section is coated with a thin film, so The film is used to detect the photoacoustic signal transmitted through the medium.

Further, the film is a metal film or a graphene film.

The utility model also provides a reflective photoacoustic microscope based on a surface wave sound pressure detector, including a reflective microscopic objective lens and an acoustic signal detector;

The reflective microscope objective lens is placed above the acoustic signal detector, and is used to focus and irradiate the laser light emitted by the laser source onto the object to be measured, so that the object to be measured absorbs the laser light and generates a photoacoustic signal, The photoacoustic signal enters the acoustic signal detector after reverse transmission through the medium above the object to be measured for refraction;

The acoustic signal detector is placed above the object to be measured and below the reflective microscope objective lens, and is used to detect a photoacoustic signal transmitted through a medium, and generate a signal of the object to be measured according to the photoacoustic signal. The detection spectrum used to image the object to be measured.

Further, the acoustic signal detector is a prism whose upper and lower planes are parallel and the lower plane is coated with a thin film or a multimode optical fiber coated with a thin film, and the thin film is used to detect photoacoustic signals transmitted through a medium;

The multimode optical fiber includes a cladding and a core placed in the cladding, the core of the multimode optical fiber has a cross-section parallel to the extending direction of the multimode optical fiber, and the cladding has a The cross section is exposed in the gap outside the cladding, the cross section is located at the gap, and the thin film is plated on the cross section.

Further, the reflective photoacoustic microscope also includes an excitation optical path component and a detection optical path component;

The excitation optical path component is used to emit pulsed laser light to focus on the object to be measured, so as to excite the object to be measured to generate a photoacoustic signal;

The detection optical path assembly is used to emit continuous laser light incident on the acoustic signal detector for total internal reflection, and detect the change of the refractive index of the reflected light signal after total internal reflection.

Further, the excitation optical path assembly includes a tunable laser, an aperture, a beam expander, a focusing coupling lens, and a first single-mode optical fiber;

The tunable laser is used to generate pulsed laser light;

The aperture is placed in front of the tunable laser for adjusting the beam size of the pulsed laser;

The beam expander is used to expand the beam of the pulsed laser coming out from the aperture;

The focus coupling lens is placed in front of the beam expander, and is used to focus and couple the expanded pulsed laser light;

The first single-mode optical fiber is placed in front of the focusing coupling lens for transmitting the focused and coupled pulsed laser light to the reflective microscope objective lens.

Further, the excitation optical path assembly also includes a planar light device and a planar mirror;

The planar light device is placed in front of the single-mode optical fiber, and is used to expand the laser source output by the first single-mode optical fiber into quasi-planar light;

The plane mirror is placed in front of the plane light device, and is used to change the direction of the pulsed laser so that the pulsed laser can enter the reflective microscope objective lens.

Further, the detection optical path assembly includes a laser, a wave plate, a first focusing coupling lens, a second single-mode fiber, a first collimating coupler, a second collimating coupler, a third single-mode fiber, a second focusing coupling A lens, a polarization beam splitter and a balance detector; a water tank is placed under the acoustic signal detector, and the object to be measured is placed under the water tank;

The laser is used to generate continuous laser light;

The wave plate is placed in front of the laser for adjusting the continuous laser light into circularly polarized light;

The first focusing and coupling lens is placed in front of the wave plate for focusing and coupling circularly polarized light;

The second single-mode optical fiber is placed in front of the first focusing coupling lens for transmitting the focused and coupled continuous laser light;

The first and second collimating couplers are placed on both sides of the acoustic signal detector, and the first collimating coupler is used for collimating and coupling the light coming out of the second single-mode fiber, so The second collimating coupler is used to collimate and couple the light coming out of the acoustic signal detector and output it to the third single-mode optical fiber;

The third single-mode optical fiber is used to transmit the reflected light from the second collimating coupler;

The second focus coupling lens is used to focus and couple the reflected light;

The polarization beam splitter is used to split the reflected light after focusing and coupling into P polarized light and S polarized light;

The balance detector is placed behind the polarization beam splitter, and is used to detect the refractive index variation of the P-polarized light and the S-polarized light.

Further, the detection optical path assembly includes a plane mirror, and the plane mirror is placed on one side of the polarization beam splitter for adjusting the direction of the S-polarized light coming out of the polarization beam splitter.

Further, the sound pressure detector further includes an imaging device, and the imaging device generates a photoacoustic imaging stereogram of the object to be measured according to the refractive index variation detected by the balance detector.

Further, the reflective photoacoustic microscope also includes a three-dimensional motorized platform, and the reflective microscope objective lens and the acoustic signal detector are fixed on the three-dimensional motorized platform.

Compared with the prior art, the utility model has the beneficial effect that: the acoustic signal detector based on the surface wave coats the thin film on one of the two parallel planes on the prism, so that the thin film can detect the acoustic signal transmitted through the medium. The change of the photoacoustic signal reflects the change of the refractive index, so that point detection can be realized. Since the acoustic signal detector adopts the method of optically sensing the refractive index, the object to be measured has the characteristics of marking-free and non-contact sensing detection, and can realize the advantages of detection bandwidth and detection sensitivity. Applying this surface wave-based acoustic signal detector to a reflective photoacoustic microscope can realize the imaging detection of living organisms.

Description of drawings

Fig. 1 is a kind of structure diagram of the acoustic signal detector based on the surface wave provided by the utility model embodiment;

Fig. 2 is a schematic structural view of a reflective photoacoustic microscope based on a surface wave acoustic signal detector provided by an embodiment of the present invention;

Fig. 3 is another kind of structural representation of the acoustic signal detector based on surface wave;

Fig. 4 is a schematic diagram of a photoacoustic signal measured by the surface wave-based acoustic signal detector of the present invention;

Fig. 5 is a schematic diagram of the spectrum range of the photoacoustic signal detected by the surface wave-based acoustic signal detector of the present invention;

6 is a schematic diagram of photoacoustic imaging of a human hair sample detected by a reflective photoacoustic microscope based on a surface wave acoustic signal detector of the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

An acoustic signal detector based on surface waves includes a prism with two parallel planes, one of the two parallel planes is coated with a thin film, and the thin film is used to detect photoacoustic signals transmitted through a medium.

The acoustic signal detector based on the surface wave is based on the principle of total internal reflection, using the high-sensitivity sensing principle of the surface wave, and the photoacoustic signal transmitted through the medium can be detected by using a thin film coated on one of the two planes parallel to each other. .

In this embodiment, the film is a metal film or a graphene film. The prism is a trapezoidal prism, the cross section of the trapezoidal prism is circular or rectangular, and the longitudinal section is trapezoidal. The metal film or graphene film is used as the base material for surface wave generation, the thickness of the surface metal film and the graphene film can be replaced, and the thickness of different film layers will affect the highest detection sensitivity. The metal thin film can be a gold film, a silver film, etc., preferably, the thickness of the plated metal film is about 45nm. The graphene film can be divided into multiple layers for vapor deposition. Preferably, the graphene film has 5 layers of graphene with a thickness of 1.7 nm.

As shown in Figure 3, a kind of acoustic signal detector based on surface wave comprises multimode fiber 301, and multimode fiber 301 comprises cladding 302 and the fiber core 303 that places cladding 302, and the fiber core of multimode fiber 301 303 has a section 304 parallel to the extending direction of the length of the multimode optical fiber 301. The cladding 302 has a notch 305. The section 304 is located at the notch 305. The notch 305 exposes the section 304 to the outside. The section 304 is coated with a thin film, which is used for Detection of photoacoustic signals transmitted through a medium.

In this embodiment, the film is a metal film or a graphene film. The metal film or graphene film is used as the base material for surface wave generation. The thickness of the surface metal film and the graphene film can be set to different values according to the actual application. Different film thicknesses will affect the highest detection sensitivity. The metal thin film can be a gold film, a silver film, etc., preferably, the thickness of the plated metal film is about 45nm. The graphene film can be divided into multiple layers for vapor deposition. Preferably, the graphene film has 5 layers of graphene with a thickness of 1.7 nm.

Please refer to Fig. 1. Fig. 1 is a structural schematic diagram of a reflective photoacoustic microscope based on a surface wave sound pressure detector provided by one of the embodiments of the present invention. The surface wave based sound pressure detector includes a reflective display Micro objective lens 101 and acoustic signal detector 102. The reflective microscope objective lens 101 is placed above the acoustic signal detector 102 and is used to focus and irradiate the laser light emitted by the laser source onto the object 103 to be measured. The object to be measured 103 absorbs the laser light and generates a photoacoustic signal, and the photoacoustic signal is reversely transmitted through the medium above the object to be measured, refracted, and then enters the acoustic signal detector 102 . The object to be tested 103 in FIG. 1 is a mouse as an illustration, but not limited to a mouse. The object to be tested can be a biological thick sample, a living sample, such as various cells, various animals, and the like. The acoustic signal detector 102 is placed above the object to be measured 103, and is used to detect the photoacoustic signal transmitted through the medium, and generate a detection spectrum of the object to be measured 103 according to the photoacoustic signal, and the detection spectrum can be used to image the object to be measured . The excitation and receiving photoacoustic signals of the overall structure of the reflective photoacoustic microscope of the surface wave-based sound pressure detector do not interfere with each other.

The acoustic signal detector 102 may be a prism whose upper and lower planes are parallel and one of the planes is coated with a thin film, or may be a multimode optical fiber coated with a thin film. The prism can be a trapezoidal prism, and the thin film can be coated on the lower plane of the trapezoidal prism, or the thin film can be coated on the core section of the multimode optical fiber. The film is a metal film or a graphene film.

The metal film or graphene film is used as the base material for surface wave generation, the thickness of the surface metal film and the graphene film can be replaced, and the thickness of different film layers will affect the highest detection sensitivity. The metal thin film can be a gold film, a silver film, etc., preferably, the thickness of the plated metal film is about 45nm. The graphene film can be divided into multiple layers for vapor deposition. Preferably, the graphene film has 5 layers of graphene with a thickness of 1.7 nm.

Using metal thin film as the base material for generating surface waves, that is, coating the metal thin film on the surface of a table-shaped prism or a single-mode optical fiber, can make the theoretical detection sensitivity of SPR differential photoacoustic detection reach 10 ^-8 RIU, which corresponds to 0.07Pa in water The sound pressure change is much higher than the detection sensitivity of existing ultrasonic transducers. At the same time, the response time for stimulating SPR is on the order of nanoseconds, and the corresponding ideal frequency bandwidth can reach 1000MHz, which is also much higher than the frequency bandwidth response width of existing ultrasonic transducers.

Graphene films have better thermal conductivity and greater thermal damage threshold than metal films, and are more suitable for high-power pulsed lasers as excitation sources for photoacoustic signals. Moreover, graphene film has a higher free electron density than metal film, so graphene has a faster response to light absorption time, which can reach picosecond or even femtosecond level, and its corresponding ideal frequency bandwidth is wider.

As shown in Figure 3, the multimode optical fiber 301 comprises a cladding 302 and a core 303 placed in the cladding, the core 303 of the multimode optical fiber 301 has a section 304 parallel to the extending direction of the length of the multimode optical fiber 301, and the cladding 302 has a notch 305, the section 304 is located at the notch 305, the notch 305 exposes the section 304 outside the cladding 302, and the thin film is plated on the section 304. Specifically, the cladding 302 of the multimode optical fiber 301 is cut off for a section along the direction perpendicular to the length, so that the outer surface of the fiber core 302 is exposed, and the outer surface of the exposed fiber core 302 can be a cut section of the cladding 302 corresponds to one-half of the outer surface of the fiber core 303, one-third of the outer surface, and the like. Then the exposed fiber core 302 is cut along the length direction of the multimode fiber 301, and the section 304 obtained is parallel to the extension direction of the length of the multimode fiber 301, and then coated with a metal film or a graphene film on the section 304 .

The acoustic signal detector based on the surface wave uses a reflective microscope objective lens to concentrate and irradiate the laser light on the object 103 to be measured, so that the object 103 to be measured absorbs the laser light and generates a photoacoustic signal, and then uses the acoustic signal detector to detect the transmission through the medium. A refracted photoacoustic signal is generated, and a detection spectrum of the object to be measured is generated according to the refracted photoacoustic signal. Since the acoustic signal detector adopts the method of optically sensing the refractive index, the object to be measured has the characteristics of marking-free and non-contact sensing detection, and can realize the advantages of detection bandwidth and detection sensitivity.

Please refer to Fig. 2. Fig. 2 is a schematic structural diagram of a reflective photoacoustic microscope based on a surface wave sound pressure detector of the present invention. Components and Probing Optical Path Components.

The reflective microscope objective lens 101 is placed above the acoustic signal detector 102 for focusing and irradiating the laser light onto the object 103 to be measured. The object 103 to be measured absorbs the laser light and generates a photoacoustic signal, and the photoacoustic signal is reversely transmitted through the medium for refraction and then enters the acoustic signal detector 102 .

The acoustic signal detector 102 is placed above the object to be measured 103 for detecting the photoacoustic signal transmitted through the medium, and generating a detection spectrum of the object to be measured 103 according to the photoacoustic signal. The detection optical device 102 is a trapezoidal prism coated with a thin film or a single-mode optical fiber 301 coated with a thin film. The film is a metal film or a graphene film. For details about the metal thin film or the graphene thin film, please refer to the previous embodiment, which will not be repeated here.

The excitation light path component is used to emit pulsed laser light and focus it on the object 103 to be measured, so as to excite the object 103 to be measured to generate a photoacoustic signal.

The excitation light path components include a tunable laser 104 , an aperture 105 , a beam expander 106 , a focusing coupling lens 107 and a first single-mode fiber 108 .

The tunable laser 104 is used to generate pulsed laser, which is used for photoacoustic imaging. As an example, the pulsed laser has a wavelength of 532 nm and a pulse width of 1.8 ns. Pulsed lasers with other wavelengths and pulse widths can also realize photoacoustic imaging. Width to adjust parameters of other optics.

The aperture 105 is placed in front of the tunable laser 104 for adjusting the beam size of the pulsed laser.

The beam expander 106 is used to expand the beam of the pulsed laser light coming out of the aperture 105 . The beam expander 106 includes a lens 1061 , a pinhole lens 1062 and a lens 1063 .

The focus coupling lens 107 is placed in front of the beam expander 106 for focusing and coupling the pulsed laser beam expanded.

The first single-mode optical fiber 108 is placed in front of the focusing coupling lens 107 for transmitting the focused and coupled pulsed laser light to the reflective microscope objective lens 101 . The laser light of the first single-mode fiber 108 is output from the fiber port 111 . The use of optical fiber to couple and transmit the pulsed laser is to use the stability of optical fiber transmission to ensure that the optical signal does not change in the core part of the system including the reflective microscope objective lens 101 and the mesa prism during the scanning and imaging process of the platform, so that it can Ensure photoacoustic imaging under homogeneous conditions.

The excitation light path assembly also includes a plane light device 109 and a plane mirror 110 . The planar light device 109 is placed in front of the single-mode optical fiber 108, and is used to expand the beam of the laser source output by the first single-mode optical fiber 108 into quasi-planar light. The plane mirror 110 is placed in front of the plane light device 109 for changing the direction of the pulsed laser light so that it can enter the reflective microscope objective lens 101 .

After the pulsed laser passes through the diaphragm 105, the beam expander 106 and the focusing coupling lens 107, it enters the reflective microscopic objective lens 101 with high numerical aperture as an excitation source to generate a sound pressure signal. The sound pressure signal is generated because the pulsed laser is focused on the object 103 to be measured through the reflective microscope objective lens 101 with high numerical aperture, and the sample passes through absorption, resulting in a broadband super wave (ie photoacoustic signal) generated by the instantaneous thermoelastic effect. The generated photoacoustic signal is transmitted to the surface of the acoustic signal detector 102 through the medium, causing a change in the refractive index. The medium may be air, a liquid, such as water, oil, a solution, or the like. The change of the refractive index is due to the small change of the density of the medium caused by the acoustic signal, such as water or air. One of the manifestations of the change of the material density is the change of the refractive index.

The detection optical path assembly is used to emit continuous laser light incident on the acoustic signal detector 102 for total internal reflection, and detect the change of the refractive index of the reflected light signal after total internal reflection.

The detection optical path assembly includes a laser 201, a wave plate 202, a first focusing coupling lens 203, a second single-mode fiber 204, a first collimating coupler 205, a second collimating coupler 206, a third single-mode fiber 207, a second Focus coupling lens 208 , polarizing beam splitter 210 and balanced detector 211 . A water tank 213 is placed under the acoustic signal detector 102 , and the object 103 to be tested is placed under the water tank 213 .

Laser 201 is used to generate continuous laser light.

The wave plate 202 is placed in front of the laser 201 for adjusting the continuous laser light into circularly polarized light, and the wave plate 202 may be a quarter wave plate.

The first focusing and coupling lens 203 is placed in front of the wave plate 202 for focusing and coupling the circularly polarized light.

The second single-mode optical fiber 204 is placed in front of the first focusing coupling lens 203 for transmitting the focused and coupled continuous laser light. The laser light of the second single-mode fiber 204 is output from the fiber port 217 . That is, the continuous laser light is coupled into the optical fiber to realize optical fiber transmission and focus on the surface of the acoustic signal detector 102 .

The first and second collimating couplers 205 and 206 are placed on both sides of the acoustic signal detector 102 . The first collimating coupler 205 is used for collimating and coupling the light emitted from the second single-mode fiber 204 . The second collimating coupler 206 is used for collimating and coupling the light emitted from the acoustic signal detector 102 and outputting it to the third single-mode optical fiber 207 .

The third single-mode fiber 207 is used to transmit the reflected light from the second collimating coupler 206 . The laser light of the third single-mode fiber 207 is output from the fiber port 216 . In the detection optical path, the second single-mode fiber 204, the third single-mode fiber 207, and the first and second collimation couplers 205, 206 are used for coupling transmission, and the fiber transmission makes the continuous laser stable, thus ensuring the platform scanning During the imaging process, the optical signal does not change in the core part of the system including the reflective microscopic objective lens 101 and the acoustic signal detector 102, thereby ensuring photoacoustic imaging under uniform conditions.

The second focus coupling lens 208 is used to focus and couple the reflected light.

The polarization beam splitter 210 is used to split the focused and coupled reflected light into P-polarized light and S-polarized light.

The balance detector 211 is placed behind the polarization beam splitter 210 and is used to detect the variation of the refractive index of the P-polarized light and the S-polarized light.

The detection optical path assembly may also include a plane mirror 209 placed on one side of the polarization beam splitter for adjusting the direction of the S-polarized light coming out of the polarization beam splitter 210 .

The continuous laser light is modulated into circularly polarized light by the quarter-wave plate 202, focused and coupled by the first focusing coupling lens 203, transmitted by the second single-mode optical fiber 204, incident on the surface of the table-shaped prism, and detected by total internal reflection. The reflected light signal of the light, the reflected light is transmitted through the third single-mode optical fiber 207, the second focusing coupling lens 208 is focused and coupled, the polarization beam splitter 210 is divided into two parts of P polarization and S polarization, and the balance detector 211 is used to detect the circular The intensity difference between the P polarization component and the S polarization component in the polarized light realizes the measurement of the refractive index change on the surface of the mesa prism, and realizes differential detection by detecting the intensity of the P and S polarization components in the common optical path, which can effectively reduce environmental interference , including the influence of factors such as laser instability, environmental vibration, and temperature changes, to improve the detection sensitivity of the system.

The sound pressure detector also includes an imaging device 212, a control data card 215 and a three-dimensional platform. The imaging device 212 generates a photoacoustic imaging stereogram of the object to be measured according to the refractive index variation detected by the balance detector 211. The imaging device can be a desktop computer , laptop, etc. The three-dimensional platform may be a three-dimensional electric platform or a three-dimensional manual platform. Components such as the reflective microscope objective lens 101 and the acoustic signal detector 102 are fixed on the three-dimensional electric platform. The optical device reflective microscopic objective lens 101, acoustic signal detector 102, planar light device 109, planar mirror 110, first collimating coupler 205, second collimating coupler 206 and water tank 213 of dotted line frame 214 part among the figure all can be Fixed on the three-dimensional electric platform. The control data card 215 is connected with the imaging device 212, and is used to control the high-precision movement of the three-dimensional platform, and to control the tunable laser 104 and the balance detector 211, so as to ensure the synchronization between the three-dimensional platform, the tunable laser 104 and the balance detector 211 . The imaging device 212 is also used for storage and analysis of control data. The photoacoustic imaging is realized through the three-dimensional scanning of the three-dimensional electric platform. The three-dimensional electric platform has the advantage of a large scanning range and is suitable for photoacoustic imaging of biological thick samples and living samples.

During the photoacoustic imaging process, the object to be measured 103 is placed under the scanning platform, and the object to be measured 103 may be a living tissue sample. The three-dimensional electric platform is used to scan to realize focused light irradiation on different parts of the object 103 to be measured. When the pulsed laser is focused and excited by the reflective microscopic objective lens 101 to excite the object 103 to be measured, a photoacoustic signal is generated due to the absorption of the object 103 to be measured. Reverse transmission enters the water tank 213 and conducts to the surface of the acoustic signal detector 102 through the water, causing a weak change in the surface refractive index, because the pulsed light signal does not cause the change in the surface refractive index, so the exact change can be obtained by detecting the change in the surface refractive index. photoacoustic signal. Since different parts of the acoustic signal detector 102 absorb light differently, photoacoustic signals with different intensities of acoustic spectra will be generated. Photoacoustic signals of different intensities cause changes in the refractive index of the surface, and photoacoustic signals of different acoustic spectra also cause different time responses of refractive index changes. By using the acoustic signal detector 102 to detect the variation of the refractive index and the time response characteristic, the material composition of the object 103 to be measured can be analyzed. Using the three-dimensional platform, the vertical scanning can realize the detection of the object 103 to be measured at different depths, and the horizontal scanning can realize the detection of the object 103 to be measured in the same depth plane. The imaging resolution is determined by the precision of the three-dimensional platform and the detection spectral width of the photoacoustic signal. Combining the scanning information of different parts of the object 103 can realize a complete photoacoustic imaging stereogram. As shown in Figure 4, it is a schematic diagram of the photoacoustic signal measured by the acoustic signal detector based on the surface wave, and as shown in Figure 5, it is a photoacoustic signal spectrum detected by the acoustic signal detector based on the surface wave of the present utility model Range diagram.

The reflective photoacoustic microscope based on the surface wave acoustic pressure detector can be divided into an excitation optical path assembly and a detection optical path assembly. The excitation optical path is mainly composed of a tunable laser 104, an aperture 105, a beam expander 106, a focusing coupling lens 107 and A single-mode optical fiber 108 and other optical devices, the detection optical path is mainly composed of a laser 201, a wave plate 202, a first focusing coupling lens 203, a second single-mode optical fiber 204, a first collimating coupler 205, a second collimating coupler 206, a third single-mode optical fiber 207, a second focusing coupling lens 208, a polarization beam splitter 210, a balance detector 211 and other optical components.

The pulsed laser light in the excitation optical path comes out of the tunable laser 104 , passes through an aperture, expands the beam, couples with an optical fiber, transmits with a single-mode optical fiber, and is reflected by a plane mirror and enters the reflective microscope objective lens 101 . The pulsed laser is focused and excited by the reflective microscopic objective lens 101 with high numerical aperture to excite the object 103 to be measured, and the broadband ultrasonic wave (that is, the photoacoustic signal) generated by the instantaneous thermoelastic effect is used to excite with pulsed light, because the acoustic signal is a wide-spectrum signal , the entire wide-spectrum information of the photoacoustic signal can be obtained by detecting the time response of the photoacoustic signal and using time-frequency domain variation analysis. A large part of the incident laser light will be absorbed or transmitted through the object 103 to be measured. If the object 103 to be measured is a thin layer or a transparent body, the laser light will be able to pass through, and its reflection ratio is small, and the generated photoacoustic signals basically belong to each Transmitting in the same direction and detecting the photoacoustic signal transmitted backward through the detection optical path, the biggest advantage is that it can avoid the interference of the laser in the excitation optical path, and can realize the detection of thick samples in vivo. In the detection optical path, the continuous laser light is modulated into circularly polarized light by a 1/4 wave plate 202. After focusing and coupling, it is transmitted by a single-mode optical fiber and incident on the surface of a desktop prism. Using total internal reflection, the reflected light signal of red light is detected. The reflected light passes through Focusing coupling, transmission by the third single-mode optical fiber 207, polarization beam splitter 210 is divided into two parts of P polarization and S polarization, and the balance detector 211 is used to detect the intensity difference between the P polarization component and the S polarization component in the circularly polarized light to realize the The measurement of the refractive index change on the surface of the type prism realizes differential detection by detecting the intensity of P and S polarized light components in the common optical path, which can effectively reduce environmental interference and improve the detection sensitivity of the system. Because the surface of the trapezoidal prism or the core 303 section of the single-mode optical fiber 301 is coated with a metal film or a graphene film, the reflection intensity difference of the two polarized light components caused by the weak refractive index change on the surface can be further increased to amplify the signal. function to improve the detection sensitivity. As shown in FIG. 6 , it is a schematic diagram of photoacoustic imaging of a human hair sample detected by a reflective photoacoustic microscope based on a surface wave acoustic signal detector.

The reflective photoacoustic microscope of the acoustic signal detector based on the surface wave of the utility model uses a reflective microscopic objective lens to gather and irradiate the laser light onto the object 103 to be measured, so that the object 103 to be measured absorbs the laser light and generates a photoacoustic signal, and then The acoustic signal detector 102 is used to detect the refracted photoacoustic signal transmitted through the medium, and a detection spectrum of the object to be measured is generated according to the refracted photoacoustic signal. The optical surface wave sensing technology in the utility model is realized by the method of optical sensing refractive index, which has the characteristics of label-free and non-contact sensing and detection, and can be widely used in the detection of cells and molecules. Since any small change and action can easily cause the change of the refractive index, the slight change of the solution's refractive index caused by the acoustic vibration can also be detected by the optical surface wave. Surface waves have advantages in acoustic wave detection bandwidth, sensitivity, etc.: surface wave propagation distance is short, time response is fast, generally within 1ns, and higher detection bandwidth can be achieved; surface waves are super sensitive to small changes in refractive index , can achieve a detection sensitivity of 10Pa level; at the same time, due to the response characteristics of surface waves to different polarizations, the signal contrast can be greatly improved by using the polarization difference method.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (13)

1. an acoustical signal detector based on surface wave, it is characterised in that include the rib with two planes being parallel to each other Mirror, described in a plane in two planes being parallel to each other be coated with thin film, described thin film for detection through the light of medium transmission Acoustical signal.

Acoustical signal detector the most according to claim 1, it is characterised in that described thin film be metallic film or Graphene thin Film.

3. an acoustical signal detector based on surface wave, including multimode fibre, it is characterised in that described multimode fibre includes bag Layer and the fibre core being placed in covering, it is parallel with described multimode fibre length bearing of trend that the fibre core of described multimode fibre has one Cross section, described covering has a breach making described cross section be exposed to outside described covering, and described cross section is positioned at described indentation, there, institute Stating and be coated with thin film on cross section, described thin film is for detecting the photoacoustic signal through medium transmission.

Acoustical signal detector the most according to claim 3, it is characterised in that described thin film be metallic film or Graphene thin Film.

5. the reflecting light sonomicroscope of an acoustic pressure detector based on surface wave, it is characterised in that include reflective micro- Object lens harmony signal sensor；

Described catoptric micro objective is placed in the top of described acoustical signal detector, shines for the laser focusing launched by lasing light emitter It is mapped on object under test so that described object under test absorbs described laser and produces photoacoustic signal, and described photoacoustic signal reversely passes Defeated after the medium above object under test reflects, enter described acoustical signal detector；

Described acoustical signal detector is placed in the top of described object under test and is positioned at the lower section of described catoptric micro objective, is used for Detect through the photoacoustic signal of medium transmission, and according to described photoacoustic signal generate object under test for making object under test imaging Detection spectrum.

Reflecting light sonomicroscope the most according to claim 5, it is characterised in that described acoustical signal detector is for put down up and down Face is parallel and lower plane is coated with the prism of thin film or is coated with the multimode fibre of thin film, and described thin film is for detecting through medium transmission Photoacoustic signal；

Described multimode fibre include covering and the fibre core being placed in covering, the fibre core of described multimode fibre have one with described multimode The cross section that fiber lengths bearing of trend is parallel, described covering has a breach making described cross section be exposed to outside described covering, institute Stating cross section and be positioned at described indentation, there, described thin film is plated on described cross section.

Reflecting light sonomicroscope the most according to claim 5, it is characterised in that described reflecting light sonomicroscope also wraps Include excitation light path assembly and detection optical path component；

Described excitation light path assembly focuses on described object under test for emission pulse laser, to excite object under test to produce light Acoustical signal；

Described detection optical path component is used for sending continuous laser and incides to carry out total internal reflection on described acoustical signal detector, and The variations in refractive index of detection reflected light signal after total internal reflection.

Reflecting light sonomicroscope the most according to claim 7, it is characterised in that described excitation light path assembly includes adjustable Humorous laser instrument, diaphragm, expand device, focus on coupled lens and the first single-mode fiber；

Described tunable laser is used for producing pulse laser；

Described diaphragm is placed in the front of described tunable laser, for adjusting the beam size of pulse laser；

The described device that expands is for being enlarged from the light beam of described diaphragm pulse laser out；

Described focusing coupled lens expands the front of device described in being placed in, for being gathered by the pulse laser expanded through light beam Burnt coupling；

Described first single-mode fiber is placed in the front of described focusing coupled lens, and the pulse laser after focusing on coupling transmits On described catoptric micro objective.

Reflecting light sonomicroscope the most according to claim 8, it is characterised in that described excitation light path assembly also includes putting down Face electro-optical device and plane mirror；

Described planar light device is placed in the front of described single-mode fiber, for being expanded by the lasing light emitter of described first single-mode fiber output Restraint into directrix plane light；

Described plane mirror is placed in the front of described planar light device, makes pulse laser to enter for changing the direction of pulse laser On described catoptric micro objective.

Reflecting light sonomicroscope the most according to claim 7, it is characterised in that described detection optical path component includes swashing Light device, wave plate, the first focusing coupled lens, the second single-mode fiber, the first collimation bonder, the second collimation bonder, the 3rd list Mode fiber, the second focusing coupled lens, polarization beam apparatus and balanced detector；A water is placed in the lower section of described acoustical signal detector Groove, described object under test is placed in the lower section of described tank；

Described laser instrument is used for producing continuous laser；

Described wave plate is placed in the front of described laser instrument, for by described continuous laser furnishing rotatory polarization；

Described first focuses on coupled lens is placed in the front of described wave plate, for rotatory polarization is focused coupling；

Described second single-mode fiber is placed in the described first front focusing on coupled lens, for focusing on the continuous laser after coupling It is transmitted；

Described first, second collimation bonder is placed in the both sides of described acoustical signal detector, and described first collimation bonder is used for To carry out collimation coupling from described second single-mode fiber light out, described second collimation bonder is for will be from described acoustical signal After in detector, light out carries out collimation coupling, output is to described 3rd single-mode fiber；

Described 3rd single-mode fiber collimates bonder reflection light out for transmission from described second；

Described second focuses on coupled lens for described reflection light is focused coupling；

Described polarization beam apparatus reflection light after being focused coupling is split, and is divided into P polarization light and S-polarization light；

After described balanced detector is placed in described polarization beam apparatus, for detecting described P polarization light and the refraction of described S-polarization light Rate variable quantity.

11. reflecting light sonomicroscopes according to claim 10, it is characterised in that described detection optical path component includes putting down Face mirror, described plane mirror is placed in the side of polarization beam apparatus, for adjusting the side from described polarization beam apparatus S-polarization light out To.

12. reflecting light sonomicroscope according to claim 10, it is characterised in that described acoustic pressure detector also includes into As device, the optoacoustic that described imaging device generates object under test according to the refractive index variable quantity that described balanced detector detects becomes As axonometric chart.

13. reflecting light sonomicroscopes according to claim 5, it is characterised in that described reflecting light sonomicroscope is also It is fixedly arranged on three-D electric platform including three-D electric platform, described catoptric micro objective and described acoustical signal detector.