JP2014126400A - Photoacoustic microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoacoustic microscope that is able to achieve high speed scanning and able to improve detection accuracy over a wide scanning range.SOLUTION: A photoacoustic microscope comprises; an objective lens 12 that emits excitation light L to a sample S; a light scanning part 11 that scans the sample S by deflecting the excitation light L; an acoustic lens 14 that converts the wave surface of a photoacoustic wave U generated from the sample S by the emission of the excitation light L; a photoacoustic wave detection part 15 that detects a photoacoustic wave U from the photoacoustic lens 14; a drive part 21 that displaces at least either the photoacoustic lens 14 or photoacoustic wave detection part 15; and a control part 20 that controls the drive part 21 in synchronization with the scan of the excitation light U by the optical scanning part 11 such that the photoacoustic wave U is made incident on the photoacoustic wave detection part 15 in perpendicular.

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, photoacoustic waves are a kind of ultrasonic waves and have a characteristic that they are less susceptible to scattering than light, and thus are applied as imaging means inside a living body.

  In photoacoustic microscopes that apply photoacoustic waves to imaging as detection signals, pulsed light that matches the absorption wavelength region of the observation object is used as excitation light, and the excitation light is collected by the objective lens and collected in the specimen. A method is used in which scanning is performed by a spot, and thereby a photoacoustic wave generated at each focused spot position is detected by a transducer or the like. According to such a photoacoustic microscope, when a specimen is scanned with a condensing spot, a photoacoustic wave is generated if an absorbing substance is present at the condensing spot position. Therefore, by detecting the photoacoustic wave, absorption within the specimen Characteristics can be imaged.

  As such a photoacoustic microscope, for example, the one disclosed in Patent Document 1 is known. FIG. 6 shows a photoacoustic microscope disclosed in Patent Document 1. In FIG. 6, excitation light L from a laser pulse light source (not shown) includes a condensing lens 101, a pinhole 102, a vibrating mirror 103, an objective lens 104, a correction lens 105, an isosceles prism 106, a silicon oil layer 107, and a rhombus prism 108. And it is condensed inside the sample S through the acoustic lens 109. In addition, the photoacoustic wave U generated from the condensing position in the sample S by the irradiation of the excitation light L is collected by the acoustic lens 109, wavefront converted, reflected in the rhomboid prism 108, and detected by the ultrasonic transducer 110. Is done.

  In FIG. 6, an isosceles prism 106 and a rhombus prism 108 are coupled via a silicon oil layer 107. The acoustic lens 109 has a rhombus prism 108 so that the sound axis corresponding to the optical axis of the optical lens coincides with the optical axis of the objective lens 104 and the focal position of the acoustic lens 109 coincides with the focal position of the objective lens 104. It is joined. The ultrasonic transducer 110 is joined to the rhomboid prism 108 so that the wavefront of the photoacoustic wave U from the focal point of the acoustic lens 109 is converted into a plane wave by the acoustic lens 109 and is perpendicularly incident on the detection surface of the ultrasonic transducer 110. Has been. The specimen S is immersed in the liquid.

Special table 2011-519281 gazette

  In the photoacoustic microscope having the configuration shown in FIG. 6, the excitation mirror L irradiated to the specimen S is deflected by vibrating the oscillating mirror 103, and the specimen S is scanned with a condensing spot of the excitation light L. However, when the excitation light L is deflected by the oscillating mirror 103, the photoacoustic wave U generated by the condensed spot irradiated with a deviation from the focal position of the acoustic lens 109 is subjected to wavefront conversion by the acoustic lens 109, and then an ultrasonic transducer. Incidently with respect to the detection surface 110.

  Here, the ultrasonic transducer 110 is set so that the detection sensitivity is highest when a plane wave is incident vertically. Therefore, if the scanning range of the sample S by the vibrating mirror 103 is to be widened, the maximum inclination of the photoacoustic wave U incident on the ultrasonic transducer 110 is increased, and the detection accuracy is lowered. In addition, in place of scanning by the vibrating mirror 103, the excitation light L incident system including the objective lens 104 and the acoustic lens 109 are included so that the photoacoustic wave U from the sample S is always perpendicularly incident on the ultrasonic transducer 110. It is assumed that the photoacoustic wave U detection system and the sample stage on which the sample S is placed are relatively moved. In this case, however, scanning takes time.

  The present invention has been made in view of such a viewpoint, and an object of the present invention is to provide a photoacoustic microscope capable of high-speed scanning and capable of improving detection accuracy over a wide scanning range.

The photoacoustic microscope according to the present invention for achieving the above object is
An objective lens for irradiating the specimen with excitation light;
An optical scanning unit that scans the specimen by deflecting the excitation light;
An acoustic lens that converts a wavefront of a photoacoustic wave generated from the sample by irradiation of the excitation light; and
A photoacoustic wave detector that detects the photoacoustic wave from the acoustic lens;
A drive unit that displaces at least one of the acoustic lens and the photoacoustic wave detection unit;
A control unit that controls the driving unit so that the photoacoustic wave is vertically incident on the photoacoustic wave detection unit in synchronization with scanning of the excitation light by the optical scanning unit;
It is characterized by providing.

  According to the present invention, it is possible to provide a photoacoustic microscope capable of performing high-speed scanning and improving detection accuracy over a wide scanning range.

It is a schematic diagram which shows the structure of the principal part of the photoacoustic microscope which concerns on 1st Embodiment. It is a partial enlarged view for demonstrating operation | movement of the photoacoustic microscope of FIG. It is a schematic diagram which shows the structure of the principal part of the photoacoustic microscope which concerns on 2nd Embodiment. It is a partial enlarged view for demonstrating operation | movement of the photoacoustic microscope of FIG. It is a schematic diagram which shows the structure of the principal part of the photoacoustic microscope which concerns on 3rd Embodiment. It is a schematic block diagram of the conventional photoacoustic microscope.

  Hereinafter, an embodiment according to an aspect of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a configuration of a main part of the photoacoustic microscope according to the first embodiment. In the photoacoustic microscope according to the present embodiment, the excitation light L emitted from the pulse light source 10 is deflected by the optical scanning unit 11, and the specimen S passes through the photoacoustic wave reflection unit 13 and the acoustic lens 14 by the objective lens 12. It is irradiated as a focused spot inside. The photoacoustic wave U generated from the specimen S is collected by the acoustic lens 14 and converted into a plane wave, and then reflected by the photoacoustic wave reflecting unit 13 in a direction different from the optical path of the excitation light L. It is detected by the acoustic wave detection unit 15.

  For example, when the specimen S is a living body and a blood vessel in the living body is imaged, the pulsed light source 10 emits excitation light L having an absorption wavelength of hemoglobin. 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, the excitation light L may be light in the absorption wavelength region of the target substance. It can also be applied to imaging of exogenous substances such as phosphors and metal nanoparticles. In this case, as the excitation light L, light in the absorption wavelength region of the target phosphor in the case of a phosphor is used, and light in the resonance wavelength region of the target metal nanoparticle in the case of a metal nanoparticle. Good. When there are a plurality of absorbers in the sample S, it is desirable to use light having a peak wavelength of the characteristic absorption spectrum of the observation object. In the pulse light source 10, the light emission timing of the pulsed light is controlled by the control unit 20.

  The optical scanning unit 11 includes, for example, two galvanometer mirrors, and is synchronized with the light emission timing of the pulsed light source 10 by the control unit 20 so that the inside of the sample S is two-dimensionally scanned by the condensed spot of the excitation light L. Drive controlled.

  The objective lens 12 having a different focal length is appropriately selected and mounted.

  The photoacoustic wave reflection unit 13 includes two right triangular prisms 13a and 13b, and their slopes are coupled by a photoacoustic wave reflection member 13c. The photoacoustic wave reflection member 13c is transparent to the excitation light L, and is made of a member having different acoustic impedance, such as silicon oil or air, for the right triangular prism 13b on the acoustic lens 14 side. Since the difference between the acoustic impedance of the right triangular prism 13b and the acoustic impedance of the photoacoustic wave reflection member 13c satisfies a predetermined relationship, the photoacoustic wave U is reflected by the photoacoustic wave reflection member 13c.

  The acoustic lens 14 is disposed so as to be joined to the exit surface of the excitation light L of the right triangular prism 13b so that the sound axis A corresponding to the optical axis of the optical lens is coaxial with the optical axis O of the objective lens 12. . The focal position of the acoustic lens 14 substantially coincides with the focal position of the objective lens 12. Thereby, the photoacoustic wave U generated from the condensing spot position of the excitation light L of the sample S is converted into a plane wave by the acoustic lens 14 and is incident on the right triangular prism 13b. Then, the photoacoustic wave U is reflected at a boundary surface between the right triangular prism 13b and the photoacoustic wave reflecting member 13c in a direction different from the optical path of the excitation light L and is emitted from the right triangular prism 13b. 15 is detected. Note that a photoacoustic wave transmission medium such as water or glycerin through which the photoacoustic wave U easily propagates is present at least between the objective lens 12 and the sample S and between the right triangular prism 13b and the photoacoustic wave detection unit 15. Filling is preferred.

  The photoacoustic wave detection part 15 consists of an ultrasonic transducer, for example. In the present embodiment, the photoacoustic wave detection unit 15 is configured to be displaceable by the drive unit 21. The drive unit 21 includes, for example, a gimbal actuator, and is synchronized with the scanning of the excitation light L by the optical scanning unit 11 so that the photoacoustic wave U enters the photoacoustic wave detection unit 15 vertically. Based on the control amount, the inclination of the detection surface 15a of the photoacoustic wave detection unit 15 with respect to the sound axis A of the acoustic lens 14 is controlled.

  The control unit 20 controls the overall operation of the photoacoustic microscope. A storage unit 22 is connected to the control unit 20. In the storage unit 22, the control amount of the driving unit 21 synchronized with the scanning of the excitation light L by the optical scanning unit 11 corresponding to the focal length of the objective lens that can be mounted on the photoacoustic microscope, that is, the photoacoustic wave detection unit The displacement amounts of the 15 detection surfaces 15a are stored in a database. Here, the displacement amount includes the inclination direction and the inclination amount of the detection surface 15a. Then, the control unit 20 reads a control amount (displacement amount) corresponding to the focal length of the mounted objective lens 12 from the storage unit 22, and synchronizes the driving unit 21 with the scanning of the excitation light L by the optical scanning unit 11. Control. The storage unit 22 stores an operation program or the like by the control unit 20 as necessary. The storage unit 22 may be a built-in memory of the control unit 20.

  In addition, a signal processing unit 23 is connected to the control unit 20. The signal processing unit 23 is synchronized with the driving of the optical scanning unit 11 by the control unit 20, that is, the irradiation timing of the excitation light L when the sample S is two-dimensionally scanned in a plane orthogonal to the optical axis O of the objective lens 12. The correspondence relationship between the irradiation position of the excitation light L and the output signal is converted into data based on the output signal obtained from the photoacoustic wave detection unit 15 in synchronization with. For example, the irradiation position of the excitation light L may be associated with the acquired signal intensity, or the irradiation position of the excitation light L may be associated with the acquired output waveform. Further, when the data of the scanning surface of the specimen S is imaged, it is imaged by the signal processing unit 23 and is stored in the image storage unit and displayed on the monitor, for example, although not shown. The signal processing unit 23 may be built in the control unit 20.

  According to the photoacoustic microscope according to the present embodiment, the plane wave of the photoacoustic wave U from the sample S is applied to the detection surface 15 a of the photoacoustic wave detection unit 15 in synchronization with the scanning of the excitation light L by the optical scanning unit 11. The inclination of the detection surface 15a is controlled so that the light enters perpendicularly. That is, the detection surface 15a of the photoacoustic wave detection unit 15 is partially enlarged in FIG. 2A at the drive position of the optical scanning unit 11 where the condensing spot of the excitation light L is formed almost at the focal position of the acoustic lens 14. As shown in the figure, control is performed so as to be orthogonal to the sound axis A of the acoustic lens 14. In addition, at the driving position of the optical scanning unit 11 where the condensing spot of the excitation light L is formed away from the focal position of the acoustic lens 14, the detection surface 15a of the photoacoustic wave detection unit 15 is shown in FIG. As shown in the partially enlarged view, the acoustic lens 14 is controlled to be inclined with respect to the sound axis A. Here, the displacement amount of the detection surface 15a with respect to the sound axis A, that is, the inclination amount and the inclination direction of the detection surface 15a are the separation distance and separation direction of the condensed spot from the focal position of the acoustic lens 14, that is, the focal point of the objective lens 12. It changes according to the separation distance and the separation direction of the focused spot from the position.

  Therefore, according to the photoacoustic microscope according to the present embodiment, the detection accuracy of the photoacoustic wave U from the specimen S can be improved over a wide scanning range of the specimen S. Further, since the sample S is scanned by deflecting the excitation light L by the optical scanning unit 11, high-speed scanning is possible. Further, since the control amount of the drive unit 21 corresponding to the focal length of the mountable objective lens is stored in the storage unit 22, it is possible to easily cope with the use of objective lenses having various focal lengths. .

(Second Embodiment)
FIG. 3 is a schematic diagram illustrating a configuration of a main part of the photoacoustic microscope according to the second embodiment. In the photoacoustic microscope according to the present embodiment, the photoacoustic wave detector 15 is fixedly arranged in the configuration of the photoacoustic microscope shown in FIG. The acoustic lens 14 is slidably joined to the emission surface of the photoacoustic wave U of the right triangular prism 13b, and is moved by the drive unit 31 within the emission surface, that is, within a plane orthogonal to the sound axis A. The drive unit 31 includes, for example, two piezo actuators or two stepping motors, and corresponds to the two-dimensional scanning direction of the sample S by the excitation light L based on the control amount from the control unit 20 (see FIG. 1). The acoustic lens 14 is moved in a two-dimensional direction. The photoacoustic wave detection unit 15 is arranged so that the detection surface 15 a is orthogonal to the sound axis of the acoustic lens 14. Since the other configuration is the same as that of the first embodiment, the same reference numerals are given to the components having the same functions as the components shown in FIG. In FIG. 3, the control unit 20, the storage unit 22, and the signal processing unit 23 illustrated in FIG. 1 are not illustrated for the sake of clarity.

  In the photoacoustic microscope according to the present embodiment, the plane wave of the photoacoustic wave U from the sample S is applied to the detection surface 15 a of the photoacoustic wave detection unit 15 in synchronization with the scanning of the excitation light L by the optical scanning unit 11. The acoustic lens 14 is moved in a plane orthogonal to the sound axis A by the drive unit 31 so as to enter vertically. That is, in the driving position of the optical scanning unit 11 where the condensing spot of the excitation light L is formed on the optical axis O of the objective lens 12, the focal position of the acoustic lens 14 is shown in a partially enlarged view in FIG. As described above, the acoustic lens 14 is controlled so as to coincide with the condensing spot position SP of the excitation light L. 4B is a partially enlarged view of the focal position of the acoustic lens 14 at the drive position of the optical scanning unit 11 where the condensing spot of the excitation light L is formed away from the optical axis O of the objective lens 12. In FIG. As shown, the acoustic lens 14 is controlled so as to coincide with the condensing spot position SP of the excitation light L separated from the optical axis O. That is, in the present embodiment, the acoustic lens 14 is synchronized with the scanning of the excitation light L by the optical scanning unit 11 so that the focal position of the acoustic lens 14 coincides with the condensing spot position SP of the excitation light L. Is moved in a two-dimensional direction within a plane orthogonal to the sound axis A by the drive unit 31.

  Therefore, also in the photoacoustic microscope according to the present embodiment, the same effect as the photoacoustic microscope according to the first embodiment can be obtained.

(Third embodiment)
FIG. 5 is a schematic diagram illustrating a configuration of a main part of the photoacoustic microscope according to the third embodiment. In the photoacoustic microscope according to the present embodiment, in the configuration of the photoacoustic microscope shown in FIG. 1, the photoacoustic wave detection unit 15 is a right triangle so that the sound axis A of the acoustic lens 14 and the detection surface 15a are orthogonal to each other. It is arranged so as to be bonded to the exit surface of the photoacoustic wave U of the prism 13b. The acoustic lens 14 is moved by the drive unit 32 in a plane orthogonal to the sound axis A together with the photoacoustic wave reflection unit 13 and the photoacoustic wave detection unit 15. As in the case of the second embodiment, the drive unit 32 includes, for example, two piezo actuators or two stepping motors, and the sample S is based on the control amount from the control unit 20 (see FIG. 1). The photoacoustic wave reflection unit 13, the acoustic lens 14, and the photoacoustic wave detection unit 15 are moved together in the two-dimensional scanning direction by the excitation light L. Since the other configuration is the same as that of the first embodiment, the same reference numerals are given to the components having the same functions as the components shown in FIG. In FIG. 5, the control unit 20, the storage unit 22, and the signal processing unit 23 illustrated in FIG. 1 are not illustrated for the sake of clarity.

  In the photoacoustic microscope according to the present embodiment, the plane wave of the photoacoustic wave U from the sample S is applied to the detection surface 15 a of the photoacoustic wave detection unit 15 in synchronization with the scanning of the excitation light L by the optical scanning unit 11. The photoacoustic wave reflection unit 13, the acoustic lens 14, and the photoacoustic wave detection unit 15 are integrally moved in a plane orthogonal to the sound axis A by the driving unit 32 so as to enter perpendicularly. That is, at the driving position of the optical scanning unit 11 where the condensed spot of the excitation light L is formed on the optical axis O of the objective lens 12, the focal position of the acoustic lens 14 is excited as shown in FIG. It is controlled so as to coincide with the condensing spot position of the light L. Further, at the driving position of the optical scanning unit 11 where the condensing spot of the excitation light L is formed away from the optical axis O of the objective lens 12, the focal position of the acoustic lens 14 is as shown in FIG. Control is performed so as to coincide with the condensing spot position of the excitation light L separated from the optical axis O. That is, in this embodiment, the acoustic lens 14 is synchronized with the scanning of the excitation light L by the optical scanning unit 11 so that the focal position of the acoustic lens 14 matches the condensing spot position of the excitation light L. The photoacoustic wave reflection unit 13 and the photoacoustic wave detection unit 15 are moved in a two-dimensional direction in a plane orthogonal to the sound axis A by the driving unit 32.

  Therefore, also in the photoacoustic microscope according to the present embodiment, the same effect as the photoacoustic microscope according to the first embodiment can be obtained.

  In addition, this invention is not limited to the said embodiment, Many deformation | transformation or a change is possible. For example, in the third embodiment, the photoacoustic wave detection unit 15 is arranged apart from the photoacoustic wave reflection unit 13 as in the second embodiment, and the photoacoustic wave reflection unit 13 and the acoustic lens 14 are arranged. You may make it move integrally by the drive part 32. FIG. In the above embodiment, the control amount of the drive unit does not necessarily need to be stored as a database in the storage unit, and the drive unit may be controlled based on the output of a hardware or software function generation circuit or the like. Is possible. Therefore, in the present invention, the storage unit is not necessarily an essential configuration. Further, the optical scanning unit has, for example, one galvanometer mirror, and performs the main scanning of the focused spot by the galvanometer mirror, and the sub scanning is performed by moving the sample stage on which the sample S is placed. May be. In this case, the drive unit can omit the displacement control corresponding to the sub-scanning direction.

DESCRIPTION OF SYMBOLS 10 Pulse light source 11 Optical scanning part 12 Objective lens 13 Photoacoustic wave reflection part 13a, 13b Right triangle prism 13c Photoacoustic wave reflection member 14 Acoustic lens 15 Photoacoustic wave detection part 15a Detection surface 20 Control part 21, 31, 32 Drive part 22 Storage Unit 23 Signal Processing Unit L Excitation Light U Photoacoustic Wave S Sample

Claims (6)

An objective lens for irradiating the specimen with excitation light;
An optical scanning unit that scans the specimen by deflecting the excitation light;
An acoustic lens that converts a wavefront of a photoacoustic wave generated from the sample by irradiation of the excitation light; and
A photoacoustic wave detector that detects the photoacoustic wave from the acoustic lens;
A drive unit that displaces at least one of the acoustic lens and the photoacoustic wave detection unit;
A control unit that controls the driving unit so that the photoacoustic wave is vertically incident on the photoacoustic wave detection unit in synchronization with scanning of the excitation light by the optical scanning unit;
A photoacoustic microscope comprising:   The photoacoustic microscope according to claim 1, wherein the driving unit displaces an inclination of a detection surface of the photoacoustic wave detection unit with respect to a sound axis of the acoustic lens.   The photoacoustic microscope according to claim 1, wherein the driving unit displaces at least the acoustic lens in a plane orthogonal to the sound axis of the acoustic lens.   The photoacoustic microscope according to any one of claims 1 to 3, further comprising a photoacoustic wave reflection unit between the objective lens and the sample. A storage unit that stores a control amount of the drive unit synchronized with the scanning of the excitation light by the optical scanning unit;
The control unit controls the drive unit based on a control amount stored in the storage unit.
The photoacoustic microscope as described in any one of Claims 1 thru | or 4. The objective lens can be mounted with different focal lengths,
The storage unit stores the control amount corresponding to the focal length of the mountable objective lens,
The control unit controls the driving unit based on the control amount stored in the storage unit corresponding to the focal length of the mounted objective lens.
The photoacoustic microscope according to claim 5.

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