JP2013113804A - Photoacoustic microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoacoustic microscope having high longitudinal resolution, capable of detecting a photoacoustic wave having a high S/N in a short time, allowing for a reduced processing time and improved picture quality for imaging.SOLUTION: A photoacoustic microscope comprises: an object lens 11 which applies excitation light L to a sample 21 in an absorption wavelength range of an observation object; a scanning part 20 which scans the application position of the excitation light L to be applied to the sample 21; a photoacoustic wave detecting part 19 which detects a photoacoustic wave; and an ultrasonic wave guide system which guides a photoacoustic wave U generated from the sample 21 due to the application of the excitation light L to the photoacoustic wave detecting part 19. The ultrasonic wave guide system includes an ultrasonic lens 16 having a focal position nearly identical to the focal position of the object lens 11, and a confocal aperture 17 which is disposed at a nearly confocal position to the focal position of the object lens 11, on the image side of the ultrasonic lens 16. The photoacoustic wave U from the sample 21 passes through the confocal aperture 17 so as to be guided to the photoacoustic wave detecting part 19.

Description

  The present invention relates to a photoacoustic microscope.

  A photoacoustic wave is a type of elastic wave generated in a thermoelastic process that occurs when a substance is irradiated with light in the absorption wavelength range. Therefore, photoacoustic waves are attracting attention as a technique for imaging absorption characteristics. In addition, elastic waves are a kind of ultrasonic waves, and are characterized by being less susceptible to scattering than light, and are therefore applied as imaging means inside living bodies.

  A photoacoustic microscope that applies photoacoustic waves to imaging as a detection signal uses pulsed light matched to the absorption wavelength region of the observation object as excitation light, scans the spot collected by the objective lens within the sample, A technique of detecting photoacoustic waves generated at each spot with a transducer or the like is used. According to such a photoacoustic microscope, when a spot is scanned, if an absorbing substance is present at the condensing position, a photoacoustic wave is generated. By detecting the photoacoustic wave, the absorption characteristics in the specimen are imaged. can do.

  As such a photoacoustic microscope, one having improved spatial resolution is known (for example, see Patent Document 1 and Non-Patent Document 1). In this photoacoustic microscope, excitation light L from a laser pulse light source (not shown) is converted into a condensing lens 101, a pinhole 102, an objective lens 103, and a correction lens, as shown in FIG. 104, the triangular prism 105, the silicone oil 106, the triangular prism 107, and the ultrasonic lens 108, and the light is condensed inside the sample (not shown). The triangular prisms 105 and 107 are coupled via silicon oil 106. Then, the photoacoustic wave U generated from the specimen is collected by the ultrasonic lens 108 and incident on the triangular prism 107, reflected by the joint surface between the triangular prism 107 and the silicon oil 106, and detected by the ultrasonic transducer 109. Is done.

  That is, in the photoacoustic microscope shown in FIG. 6, using the triangular prisms 105 and 107, the excitation optical system and the ultrasonic wave guide system are coaxially arranged, and the excitation light condensing spot and the ultrasonic detection spot are further arranged. And the focusing objective lens 103 and the ultrasonic detecting ultrasonic lens 108 are arranged so that their focal positions are in a conjugate relationship. As a result, a sub-micron lateral resolution determined by the focused spot of the objective lens 103 is realized.

  Therefore, according to such a configuration, for example, when laser pulse light having a wavelength of 630 nm is used as excitation light, and an objective lens 103 having NA (numerical aperture): 0.1 and diffraction limit: 3.7 μm is used, A lateral resolution of about 5 μm can be realized.

  However, in the photoacoustic microscope having the configuration shown in FIG. 6, the longitudinal resolution is determined by the frequency band of the ultrasonic transducer 109 used for detecting the photoacoustic wave U regardless of the spot size of the excitation light. For example, when the detection frequency of the ultrasonic transducer 109 is 100 MHz and the specimen 110 is a living body (ultrasonic speed: 1.5 mm / μs), the vertical resolution of the imaging image is 15 μm, and sufficient resolution cannot be obtained.

  On the other hand, as a technique for improving the vertical resolution of the photoacoustic microscope, a photoacoustic microscope using a pump-probe method as an excitation method has been proposed (for example, see Non-Patent Document 2). In this photoacoustic microscope, the excitation light L from the laser pulse light source 201 is separated into two light beams by the beam splitter 202 as shown in a schematic configuration of the main part in FIG. One light beam is incident on the beam splitter 203 as pump light Pu. The other light beam is sequentially reflected by the mirrors 204 and 205 and is incident on the beam splitter 203 as the probe light Pr. The beam splitter 203 combines the incident pump light Pu and probe light Pr coaxially and emits them. Thereby, the optical path of the probe light Pr is delayed to form a pulse train shifted in time.

  The pump light Pu and the probe light Pr emitted from the beam splitter 203 are condensed on the sample 212 by the objective lens system 211 via the lenses 206 and 207 and the mirrors 208, 209 and 210. The photoacoustic wave U generated from the specimen 212 is detected by a photoacoustic wave detection system having an ultrasonic transducer 213. A photoacoustic wave transmission medium 214 such as water is filled between the specimen 212 and the photoacoustic wave detection system.

  In this case, a photoacoustic wave is generated from the specimen 211 by a two-photon absorption process using the pump light Pu and the probe light Pr. Since this photoacoustic wave is generated only in a high energy density region, a high sectioning effect can be obtained and the longitudinal resolution can be improved.

  However, since the photoacoustic wave generated in the two-photon absorption process has the same frequency as the photoacoustic wave generated in the normal one-photon absorption process, it cannot be distinguished and detected as it is. Therefore, in the photoacoustic microscope shown in FIG. 7, choppers 215 and 216 are arranged in the optical path of the pump light Pu and the optical path of the probe light Pr between the beam splitters 202 and 203, respectively, and the pump light Pu and the probe light Pr Are modulated at different frequencies (each modulation frequency: ωpu, ωpr). Then, by extracting only the component of the photoacoustic wave subjected to frequency modulation (± (ωpu ± ωpr)) due to the interaction between the pump light and the probe light from the output signal of the ultrasonic transducer 212, in the two-photon absorption process Only the generated photoacoustic wave is separated and detected.

  FIG. 8 is a diagram showing the frequency characteristics of each modulated wave in this case, where the horizontal axis indicates the frequency and the vertical axis indicates the relative value of the intensity. Here, the repetition frequency ω1 = 10 kHz of the excitation light, the modulation frequency ωpu = 1 kHz of the pump light, and the modulation frequency ωpr = 0.7 kHz of the probe light. As shown in FIG. 8, by using the pump-probe method, ω1 ± ωpu (= 10 ± 1 [kHz]), ωl ± ωpr (= 10 ± 0. Peaks (Pu, Pr) having a frequency of 7 [kHz]) appear. Further, when the interaction between the pump light and the probe light occurs, the peaks of the frequencies ωl ± (ωpu ± ωpr) (10+ (1 ± 0.7) [kHz], 10− (1 ± 0.7) [kHz]) (PPd, PPs) will appear.

  Therefore, if the output signal of the ultrasonic transducer 212 is subjected to frequency analysis and only the component (ωl ± (ωpu ± ωpr)) generated by the interaction between the pump light and the probe light is extracted, the high energy density region is obtained by the two-photon absorption process. Since only the photoacoustic wave generated in the above can be detected, the vertical resolution can be improved.

Special table 2011-519281 gazette

Konstantin Maslov, Hao F. Zhang, Song Hu and Lihong V. Wang, Opt. Lett., 33 (9), 929 (2008) Ryan L. Shelton and Brian E. Applegate, Biomed.Opt. Express, 1 (2), 676 (2010)

  However, in the photoacoustic microscope having the configuration shown in FIG. 7, it is necessary to frequency-analyze the detected photoacoustic wave signal. Therefore, since it is necessary to detect the signal in a sufficient time, it takes time especially in the case of imaging. Further, the photoacoustic wave generated in the two-photon absorption process is weaker than the photoacoustic wave generated in the one-photon absorption process, and the signal S / N is reduced. Therefore, particularly in the case of imaging, the image quality is degraded.

  Therefore, an object of the present invention made in view of such a viewpoint is to detect a photoacoustic wave having a high vertical resolution and a high S / N in a short time, and in the case of imaging, the processing time can be shortened and the image quality can be improved. It is to provide a photoacoustic microscope.

The gist configuration of the photoacoustic microscope according to the present invention that achieves the above object is as follows.
(1) an objective lens that irradiates the specimen with excitation light in the absorption wavelength region of the observation object;
A scanning unit for scanning the irradiation position of the excitation light on the specimen;
A photoacoustic wave detector for detecting photoacoustic waves;
An ultrasonic wave guide system that guides the photoacoustic wave generated from the specimen to the photoacoustic wave detection unit by irradiation of the excitation light, and
The ultrasonic wave guide system is disposed at an ultrasonic lens having a focal position substantially coincident with the focal position of the objective lens, and at a position substantially conjugate with the focal position of the objective lens on the image side of the ultrasonic lens. And a photoacoustic wave from the sample that has passed through the confocal diaphragm is guided to the photoacoustic wave detection unit.

(2) an objective lens that irradiates the specimen with excitation light in the absorption wavelength region of the observation object;
A scanning unit for scanning the irradiation position of the excitation light on the specimen;
A photoacoustic wave detector for detecting photoacoustic waves;
An ultrasonic wave guide system that guides the photoacoustic wave generated from the specimen to the photoacoustic wave detection unit by irradiation of the excitation light, and
The ultrasonic wave guide system forms a first ultrasonic lens having a focal position substantially coincident with a focal position of the objective lens, and a second that forms a photoacoustic wave that has passed through the first ultrasonic lens. And a confocal stop arranged at a position substantially conjugate with the focal position of the objective lens on the image side of the second ultrasonic lens, and passed through the confocal stop A photoacoustic wave from a specimen is guided to the photoacoustic wave detection unit.

(3) In the photoacoustic microscope according to (1) above,
The confocal stop has substantially the same size as the diffraction limit of the ultrasonic lens.

(4) In the photoacoustic microscope according to (2) above,
The confocal stop has a size substantially the same as a diffraction limit of the second ultrasonic lens.

(5) In the photoacoustic microscope according to (1) or (2) above,
The confocal stop includes a variable stop.

  According to the present invention, a photoacoustic wave having a high vertical resolution and a high S / N can be detected in a short time. Thereby, for example, in the case of imaging, the processing time can be shortened and the image quality can be improved.

It is a figure which shows typically the structure of the principal part of the photoacoustic microscope which concerns on 1st Embodiment of this invention. It is a figure which shows typically the structure of the principal part of the photoacoustic microscope which concerns on 2nd Embodiment of this invention. It is a figure which shows typically the structure of the principal part of the photoacoustic microscope which concerns on 3rd Embodiment of this invention. It is a figure which shows typically the structure of the principal part of the photoacoustic microscope which concerns on 4th Embodiment of this invention. It is a figure which shows typically the structure of the principal part of the photoacoustic microscope which concerns on 5th Embodiment of this invention. It is a figure which shows the typical structure of the principal part of the conventional photoacoustic microscope. It is a figure which shows the typical structure of the principal part of the other conventional photoacoustic microscope. FIG. 8 is a frequency characteristic diagram of a modulated wave for explaining the operation of the photoacoustic microscope of FIG. 7.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically showing a configuration of a main part of the photoacoustic microscope according to the first embodiment of the present invention. This photoacoustic microscope includes an objective lens 11, a correction lens 12, a triangular prism 13, a photoacoustic wave reflecting member 14, a triangular prism 15, an ultrasonic lens 16, a pinhole 17, an ultrasonic lens 18, an ultrasonic transducer 19, and a scanning unit. 20.

  The triangular prisms 13 and 15 are disposed between the objective lens 11 and the sample 21. In FIG. 1, the triangular prisms 13 and 15 are right-angled triangular prisms, and the slopes of each other are coupled via a photoacoustic wave reflecting member 14. The photoacoustic wave reflection member 14 is transparent with respect to excitation light, and is made of a member having different acoustic impedance with respect to the triangular prism 15, for example, silicon oil.

  The ultrasonic lens 16 is disposed so as to be coaxial with the optical axis of the objective lens 11 and is bonded to the excitation light exit surface of the triangular prism 15. Further, the focal position of the ultrasonic lens 16 substantially coincides with the focal position of the objective lens 11. The correction lens 12 corrects aberrations caused by the triangular prisms 13 and 15, the photoacoustic wave reflection member 14, the ultrasonic lens 16, and the like. For example, the correction lens 12 is disposed to be joined to the excitation light incident surface of the triangular prism 13.

  The pinhole 17 is disposed at the image side focal position of the ultrasonic lens 16 so as to face a surface different from the surface to which the ultrasonic lens 16 of the triangular prism 15 is bonded. Therefore, the pinhole 17 constitutes a confocal stop arranged at a position conjugate with the focal position of the objective lens 11. The ultrasonic lens 18 is disposed so that the pinhole 17 is positioned at the object-side focal position. The ultrasonic transducer 19 constitutes a photoacoustic wave detection unit, and is arranged so as to detect a photoacoustic wave incident through the ultrasonic lens 18.

  The scanning unit 20 scans the irradiation position of the excitation light with respect to the specimen 21, and moves the excitation light with respect to the specimen 21 by a known configuration such as a galvanometer mirror or the specimen on which the specimen 21 is placed. A stage (not shown) is moved, or both the excitation light and the sample stage are moved. The moving direction is a two-dimensional direction in a plane orthogonal to the optical axis direction of the objective lens 11, a one-dimensional direction only in the optical axis direction of the objective lens 11, or a three-dimensional direction including both moving directions. Also good.

  In the above configuration, the excitation light (pulse light) L from the laser pulse light source (not shown) is the objective lens 11, the correction lens 12, the triangular prism 13, the photoacoustic wave reflecting member 14, the triangular prism 15, and the ultrasonic lens 16. Then, the sample 21 is irradiated and condensed inside the sample 21. Note that a space between the objective lens 11 and the specimen 21 is filled with a photoacoustic wave transmission medium 22 such as water through which a photoacoustic wave easily propagates.

  Here, for example, when the specimen 21 is a living body and a blood vessel in the living body is imaged, light having an absorption wavelength of hemoglobin is used as the excitation light L. Note that the observation target is not limited to blood vessels, and can be applied to imaging of endogenous substances such as melanin. At this time, light in the absorption wavelength region of the target substance may be used as the excitation light. It can also be applied to imaging of exogenous substances such as phosphors and metal nanoparticles. In this case, as the excitation light, light in the absorption wavelength range of the target phosphor in the case of a phosphor may be used, and light in the resonance wavelength range of the target metal nanoparticle in the case of metal nanoparticles. . When there are a plurality of absorbers in the specimen 21, it is desirable to use light having a peak wavelength of the characteristic absorption spectrum of the observation object.

  The excitation light L irradiated on the specimen 21 is absorbed by the observation object if there is an observation object that absorbs the excitation light L at the irradiation site of the excitation light L including the condensing position of the objective lens 11. Thereby, the photoacoustic wave U which is an elastic wave is generated from the sample 21. The generated photoacoustic wave U is detected by the ultrasonic transducer 19 through the ultrasonic lens 16, the triangular prism 15 and the pinhole 17.

  That is, the photoacoustic wave U generated from the specimen 21 is collected by the ultrasonic lens 16 and is incident on the triangular prism 15 as a focused wave, and is reflected by the acoustic impedance of the photoacoustic wave reflecting member 14 on the inclined surface. . The photoacoustic wave reflecting member 14 preferably has the refractive index of the excitation light L substantially equal to the refractive index of the triangular prisms 13 and 15 and is made as thin as possible. Thereby, undesired refraction and light absorption by the photoacoustic wave reflecting member 14 can be prevented, and the utilization efficiency of the excitation light L can be increased.

  The photoacoustic wave U reflected by the inclined surface of the triangular prism 15 is emitted from the triangular prism 15 and enters the pinhole 17. Here, the pinhole 17 is disposed at a position conjugate with the focal position of the objective lens 11 and acts as a confocal stop. Therefore, only the photoacoustic wave generated at the focal position of the objective lens 11 passes through the pinhole 17, and the photoacoustic wave generated outside the focal position is cut by the pinhole 17. It is desirable that the size of the pinhole 17 is about the diffraction limit of the photoacoustic wave determined by the numerical aperture of the ultrasonic lens 16.

  The photoacoustic wave that has passed through the pinhole 17 is converted into a parallel wave by the ultrasonic lens 18 and detected by the ultrasonic transducer 19. Therefore, in the present embodiment, the ultrasonic lens 16, the triangular prism 15, the pinhole 17, and the ultrasonic lens 18 constitute an ultrasonic waveguide system.

  When acquiring a tomographic image of the specimen 21, the excitation light L is two-dimensionally scanned with respect to the specimen 21 by the scanning unit 20 in a plane orthogonal to the optical axis of the objective lens 11. Then, an output signal from the ultrasonic transducer 19 is processed in synchronization with the irradiation timing of the excitation light L by a processor (not shown), and a tomographic image is formed. When detecting the distribution of the observation object in the depth direction of the specimen 21, the scanning unit 20 scans the specimen 21 with the excitation light L in the optical axis direction of the objective lens 11. Then, an output signal from the ultrasonic transducer 19 is processed by a processor (not shown) in synchronization with the irradiation timing of the excitation light L, and the distribution of the observation object in the depth direction of the specimen 21 is imaged.

  In the photoacoustic microscope according to the present embodiment, an ultrasonic wave is guided to an ultrasonic wave guide system that guides the photoacoustic wave U generated from the specimen 21 to the ultrasonic transducer 19 at a position substantially conjugate with the focal position of the objective lens 11. A pinhole 17 having the same size as the diffraction limit of the photoacoustic wave by the lens 16 is arranged. Therefore, only the photoacoustic wave generated at the focal position of the objective lens 11 can be detected by the ultrasonic transducer 19 after passing through the pinhole 17, and the photoacoustic wave generated outside the focal position can be cut by the pinhole 17. it can. Thereby, the longitudinal resolution which is the depth direction of the sample 21 can be improved, and the photoacoustic wave at the focal position can be detected with high S / N. Moreover, since it is not necessary to employ the pump-probe method, the photoacoustic wave at the focal position can be detected in a short time. Therefore, for example, in the case of imaging, the processing time can be shortened and the image quality can be improved.

  In the photoacoustic microscope according to the present embodiment, the ultrasonic wave guide system is configured, and the ultrasonic lens system that collects the photoacoustic wave U generated from the specimen 21 has one ultrasonic lens 16. It is a finite correction system. Therefore, compared with the case where the ultrasonic lens system is configured with an infinite correction system, the number of ultrasonic lenses can be reduced, and accordingly, the reflection component of the photoacoustic wave U at the boundary of the ultrasonic lens can be suppressed. The loss of the photoacoustic wave U can be suppressed.

(Second Embodiment)
FIG. 2 is a diagram schematically showing the configuration of the main part of the photoacoustic microscope according to the second embodiment of the present invention. The photoacoustic microscope according to the present embodiment includes an ultrasonic lens system that collects the photoacoustic wave U generated from the specimen 21 in the photoacoustic microscope shown in FIG. This is an infinite correction system. Therefore, in FIG. 2, the first ultrasonic lens 31 is bonded to the emission surface of the excitation light L of the triangular prism 15, and the second ultrasonic lens 32 is connected to the photoacoustic wave emission surface of the triangular prism 15. It is joined. The pinhole 17 is arranged at the image side focal position of the second ultrasonic lens 32 that is substantially conjugate with the focal position of the objective lens 11. Since other configurations are the same as those in FIG. 1, the same reference numerals are assigned to elements having the same functions, and the description thereof is omitted.

  According to the present embodiment, the photoacoustic wave U generated from the specimen 21 by the irradiation of the excitation light L is collected by the first ultrasonic lens 31 and incident as a parallel wave into the triangular prism 15, and its slope Reflected by. In addition, the parallel photoacoustic wave U reflected by the inclined surface of the triangular prism 15 is emitted from the triangular prism 15, converged by the second ultrasonic lens 32, and enters the pinhole 17. Here, as in the case of the first embodiment, the pinhole 17 is arranged at a position conjugate with the focal position of the objective lens 11 and acts as a confocal stop.

  Accordingly, also in the present embodiment, only the photoacoustic wave generated at the focal position of the objective lens 11 passes through the pinhole 17, and the photoacoustic wave generated at other than the focal position is cut by the pinhole 17, The same effect as in the case of the one embodiment can be obtained. In the present embodiment, since the ultrasonic lens system that collects the photoacoustic wave U generated from the specimen 21 is composed of an infinite correction system, it is generated from the specimen 21 compared to the case where it is composed of a finite correction system. It is possible to efficiently capture the photoacoustic wave U.

(Third embodiment)
FIG. 3 is a diagram schematically showing the configuration of the main part of the photoacoustic microscope according to the third embodiment of the present invention. The photoacoustic microscope according to the present embodiment is the same as the photoacoustic microscope shown in FIG. Separated from the wave system. Hereinafter, elements having the same functions as those in FIG.

  That is, in FIG. 3, excitation light (pulse light) L from a laser pulse light source (not shown) is condensed inside the sample 21 by the objective lens 11. Further, the photoacoustic wave U generated from the specimen 21 by the irradiation of the excitation light L is focused by the ultrasonic lens 16 constituting the finite correction system. Then, the photoacoustic wave that has passed through the pinhole 17 disposed at a position conjugate to the focal position of the objective lens 11 at the image side focal position of the ultrasonic lens 16 is detected by the ultrasonic transducer 19 via the ultrasonic lens 18. Is done.

  Accordingly, also in the present embodiment, only the photoacoustic wave generated at the focal position of the objective lens 11 passes through the pinhole 17, and the photoacoustic wave generated at other than the focal position is cut by the pinhole 17, The same effect as in the case of the one embodiment can be obtained. Further, by disposing the excitation light optical system and the ultrasonic wave guide system separately, the correction lens 12, the triangular prism 13, the photoacoustic wave reflecting member 14, and the triangular prism 15 of FIG. The working distance of the lens 11 can be shortened. As a result, it is possible to generate a high-intensity photoacoustic wave U with the objective lens 11 having a high numerical aperture, and an image with high contrast can be acquired.

(Fourth embodiment)
FIG. 4 is a diagram schematically showing a configuration of a main part of a photoacoustic microscope according to the fourth embodiment of the present invention. The photoacoustic microscope according to the present embodiment is the same as the objective lens 11 in the photoacoustic microscope shown in FIG. 2 except that the first ultrasonic lens 31 and the second ultrasonic lens 32 are the same as in the third embodiment. The excitation light optical system and the ultrasonic wave guide system are separated from each other by being inclined with respect to the optical axis. Hereinafter, elements having the same functions as those in FIG.

  That is, in FIG. 4, excitation light (pulse light) L from a laser pulse light source (not shown) is condensed inside the sample 21 by the objective lens 11. The photoacoustic wave U generated from the specimen 21 by the irradiation of the excitation light L is converted into a parallel wave by the first ultrasonic lens 31 constituting the infinite correction system, and then focused by the second ultrasonic lens 32. Is done. Then, the photoacoustic wave that has passed through the pinhole 17 disposed at a position conjugate with the focal position of the objective lens 11 at the image-side focal position of the second ultrasonic lens 32 passes through the ultrasonic lens 18 and becomes an ultrasonic transducer. 19 is detected.

  Accordingly, also in the present embodiment, only the photoacoustic wave generated at the focal position of the objective lens 11 passes through the pinhole 17, and the photoacoustic wave generated at other than the focal position is cut by the pinhole 17, The same effect as in the second embodiment can be obtained. Further, by separating the excitation light optical system and the ultrasonic wave guide system, the same effect as in the third embodiment can be obtained.

(Fifth embodiment)
FIG. 5 is a diagram schematically showing a configuration of a main part of a photoacoustic microscope according to the fifth embodiment of the present invention. In the photoacoustic microscope according to the present embodiment, the pinhole 17 in FIG. 2 is a variable pinhole (variable aperture) 41. Hereinafter, elements having the same functions as those in FIG.

  In the photoacoustic microscope, since the photoacoustic wave U generated by the irradiation of the excitation light L is an elastic wave, the transmittance varies depending on the frequency characteristic of the elastic modulus of the specimen 21. In general, the transmittance of the high frequency component is lower than that of the low frequency component. Therefore, the transmittance varies depending on the frequency according to the depth of the excitation light L collected inside the specimen 21, and the shape of the spectrum of the generated photoacoustic wave U changes. As a result, the spot size of the photoacoustic wave U when condensed by the second ultrasonic lens 32 changes. In general, as the observation position becomes deeper, high-frequency components are rapidly attenuated, so that the spot size increases.

  According to the photoacoustic microscope according to the present embodiment, as shown in FIG. 5, the variable pinhole 41 is arranged at the image side focal position of the second ultrasonic lens 32 conjugate with the focal position of the objective lens 11. . Thereby, the aperture diameter (the size of the pinhole) of the variable pinhole 41 can be changed in accordance with the depth of the excitation light L condensed inside the sample 21. Therefore, in addition to the effect of the second embodiment, it is possible to improve the S / N of photoacoustic wave detection while improving the resolution in the depth direction of the specimen 21.

  In addition, this invention is not limited only to the said embodiment, Many deformation | transformation or a change is possible. For example, in the configuration shown in FIG. 1, FIG. 3, or FIG. 4, the same effect can be obtained by using the pinhole 17 as a variable pinhole similarly to FIG. As described above, when a variable pinhole is used, it is possible to automatically adjust the aperture diameter of the variable pinhole according to the depth position of the specimen 21 on which the excitation light L is collected. It is.

DESCRIPTION OF SYMBOLS 11 Objective lens 12 Correction lens 13, 15 Triangular prism 14 Photoacoustic wave reflection member 16 Ultrasonic lens 17 Pinhole (confocal stop)
DESCRIPTION OF SYMBOLS 18 Ultrasonic lens 19 Ultrasonic transducer 20 Scanning part 21 Specimen 22 Photoacoustic wave transmission medium 31 First ultrasonic lens 32 Second ultrasonic lens 41 Variable pinhole (variable aperture)
L Excitation light U Photoacoustic wave

Claims (5)

An objective lens that irradiates the specimen with excitation light in the absorption wavelength range of the observation object;
A scanning unit for scanning the irradiation position of the excitation light on the specimen;
A photoacoustic wave detector for detecting photoacoustic waves;
An ultrasonic wave guide system that guides the photoacoustic wave generated from the specimen to the photoacoustic wave detection unit by irradiation of the excitation light, and
The ultrasonic wave guide system is disposed at an ultrasonic lens having a focal position substantially coincident with the focal position of the objective lens, and at a position substantially conjugate with the focal position of the objective lens on the image side of the ultrasonic lens. A photoacoustic microscope, wherein the photoacoustic wave from the sample that has passed through the confocal aperture is guided to the photoacoustic wave detection unit. An objective lens that irradiates the specimen with excitation light in the absorption wavelength range of the observation object;
A scanning unit for scanning the irradiation position of the excitation light on the specimen;
A photoacoustic wave detector for detecting photoacoustic waves;
An ultrasonic wave guide system that guides the photoacoustic wave generated from the specimen to the photoacoustic wave detection unit by irradiation of the excitation light, and
The ultrasonic wave guide system forms a first ultrasonic lens having a focal position substantially coincident with a focal position of the objective lens, and a second that forms a photoacoustic wave that has passed through the first ultrasonic lens. And a confocal stop arranged at a position substantially conjugate with the focal position of the objective lens on the image side of the second ultrasonic lens, and passed through the confocal stop A photoacoustic microscope characterized by guiding a photoacoustic wave from a specimen to the photoacoustic wave detection unit.   The photoacoustic microscope according to claim 1, wherein the confocal stop has a size substantially equal to a diffraction limit of the ultrasonic lens.   The photoacoustic microscope according to claim 2, wherein the confocal stop has a size substantially equal to a diffraction limit of the second ultrasonic lens. The photoacoustic microscope according to claim 1, wherein the confocal stop includes a variable stop.

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