JP2015116254A - Subject information acquisition device and acoustic wave receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for inhibiting deviation of measurement light in an acoustic wave reception using a Fabry-Perot probe.SOLUTION: A subject information acquisition device includes: a measurement light source 108 for applying measurement light from an outgoing end; a Fabry-Perot interferometer 106 including a first mirror in which an acoustic wave enters, and a second mirror in which the measurement light enters; a mask 107 provided with an array-like opening part; a photosensor 111 for detecting reflected light of the measurement light reflected by the Fabry-Perot interferometer; an excitation light source 101 for applying excitation light; and a processing part 112 that acquires characteristic information of the interior of the subject on the basis of a detection result of the photosensor that detects a change in the reflected light by a photoacoustic wave generated from the subject receiving the radiation of the excitation light and entering the first mirror. The mask is disposed at a side of the outgoing end of the first mirror with respect to a surface opposite to the surface where the acoustic wave enters, and the mask consists of a material absorbing the measurement light.

Description

  The present invention relates to an object information acquiring apparatus and an acoustic wave receiving apparatus.

  In general, imaging apparatuses using X-rays, ultrasound, and MRI (nuclear magnetic resonance method) are widely used in the medical field. On the other hand, research on optical imaging equipment that obtains in-vivo information by propagating light emitted from a light source such as a laser into a subject such as a living body and detecting the propagating light is actively promoted in the medical field. It has been. As one of such optical imaging techniques, a photoacoustic imaging technique has been proposed.

  In photoacoustic imaging, an object is irradiated with pulsed light generated from a light source, and an acoustic wave generated from a living tissue that absorbs the energy of light propagated and diffused in the object (hereinafter also referred to as photoacoustic wave). Detect at multiple locations. By analyzing the signals based on these acoustic waves, information related to the optical characteristic values inside the subject is visualized. As a result, it is possible to obtain an optical characteristic value distribution in the subject, particularly a light energy absorption density distribution.

  Examples of the acoustic wave detector include a transducer using a piezoelectric phenomenon and a transducer using a change in capacitance. In recent years, detectors using optical resonance have been developed (Non-Patent Document 1).

  A structure that resonates light between two parallel reflectors is called a Fabry-Perot interferometer. An acoustic wave detector using a Fabry-Perot interferometer is called a Fabry-Perot probe. The Fabry-Perot probe has a structure in which two mirrors (hereinafter referred to as resonance mirrors) sandwich a polymer film. When an elastic wave is incident, the mirror on the side on which the elastic wave is incident is deformed in the film thickness direction of the polymer film, and the distance between the two mirrors (hereinafter referred to as the cavity length) changes. By detecting a change in reflectance that occurs at this time, it is possible to detect an incident elastic wave.

  At this time, the area irradiated with the measurement light for measuring the reflectance is the reception area. That is, the reception area in the Fabry-Perot probe corresponds to one element size in the piezoelectric probe. Since the Fabry-Perot probe has a wide band and can suppress a decrease in sensitivity when the receiving area is further reduced, high-resolution imaging is possible.

By the way, when putting an imaging apparatus into practical use, it is important to perform imaging in a short time. In particular, when a living body is used as a subject at a medical site or the like, it is necessary for practical use to reduce the burden on the subject by performing imaging in a short time.
In order to perform imaging in a short time, it is necessary to acquire data in a short time. However, if a single probe is raster scanned in order to acquire two-dimensional distribution data of photoacoustic waves, it takes a lot of time to acquire the data.

  Therefore, in the detector using the resonance of light, in order to obtain the two-dimensional distribution of elastic waves in a lump, the sound of the ultrasonic wave irradiated to the Fabry-Perot interferometer using a CCD camera as a two-dimensional array type sensor. There is also a report example of detecting pressure (Non-Patent Document 2).

Here, a semiconductor laser called a vertical-cavity surface-emitting laser (VCSEL) will be described. A normal edge-emitting semiconductor laser emits light from the end face of its substrate, whereas a VCSEL emits light in a direction perpendicular to the substrate (Patent Document 1). There is also an example in which this is two-dimensionally arranged on a semiconductor substrate. Hereinafter, one laser (one light emission point) among the lasers arrayed two-dimensionally or one-dimensionally in this way is referred to as a light-emitting element.

Since the cavity length of the Fabry-Perot probe varies, it is necessary to change the wavelength of the measurement light according to the position on the Fabry-Perot probe in order to keep the sensitivity optimal.
Here, since the two-dimensionally arranged VCSEL can be driven independently for each light emitting element, the wavelength of the emitted light can be controlled for each light emitting element. That is, by using a VCSEL array and a two-dimensional array type sensor, it is possible to correct a variation in the cavity length and collectively acquire a two-dimensional elastic wave distribution.

US Patent Application Publication No. 2009/0135872

E. Zang, J. Laufer, and P21. Beard, “Backward-mode multiwavelength photoacoustic scanner using a planer Fabry-Perot polymer film ultrasound sensor for high-resolution three-dimensional imaging of biological tissue”, Applied Optics, 47, 4. (2008) M. Lamont, P. Beard, “2D imaging of ultrasound fields using CCD array to map output of Fabry-Perot polymer film sensor”, Electronics Letters, 42, 3, (2006)

  The Fabry-Perot probe uses a laser, a plurality of optical components, and an optical sensor to detect acoustic waves using light as a medium. Therefore, in order to obtain the acoustic wave distribution accurately, it is necessary that these optical systems are always arranged at optimum positions.

  However, when the Fabry-Perot probe is used in an ultrasonic diagnostic apparatus or the like used in a clinical field, mechanical vibration is generated when the probe is handled. In addition, when a drop impact occurs, a very strong mechanical vibration is generated. If the position of the optical component or the like is shifted due to mechanical vibration, an accurate acoustic wave distribution cannot be obtained and the image is deteriorated.

In particular, if the irradiation position of the measurement light on the Fabry-Perot probe is shifted, the relative positional relationship in the in-plane direction between the subject and the receiving element position is shifted, so that the image is deteriorated.
Further, if the interval between the light spots is shifted, the interval between the receiving elements changes, and the image quality deteriorates when an image is formed from the obtained signals.

  Furthermore, if the relative positional relationship in the vertical direction between the subject and the spot position of the measurement light shifts due to the shift of the optical system, the spot diameter on the Fabry-Perot probe cannot be fixed. As a result, the size of the receiving element changes and resolution reproducibility cannot be obtained. In addition, a change in the size of the receiving element also causes a change in the directivity of the element with respect to reception of acoustic waves.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for suppressing deviation of measurement light in acoustic wave reception using a Fabry-Perot probe.

The present invention employs the following configuration. That is,
A measurement light source that emits measurement light from the exit end; and
A Fabry-Perot interferometer composed of a first mirror on which an acoustic wave is incident and a second mirror on which the measurement light is incident;
A mask provided with openings in an array;
An optical sensor for detecting the reflected light reflected by the Fabry-Perot interferometer;
An excitation light source that emits excitation light;
Based on the detection result of the reflected light by the photoacoustic wave generated from the subject irradiated with the excitation light and incident on the first mirror, characteristic information in the subject is acquired. A processing unit to
Have
The mask is disposed closer to the emission end than the surface of the first mirror opposite to the surface on which the acoustic wave is incident,
The mask is an object information acquiring apparatus characterized in that the mask is made of a material that absorbs the measurement light.

The present invention also employs the following configuration. That is,
A measurement light source that emits measurement light from the exit end; and
A transducer for transmitting an acoustic wave to the subject;
A Fabry-Perot interferometer composed of a first mirror on which an acoustic wave is incident and a second mirror on which the measurement light is incident;
A mask provided with openings in an array;
An optical sensor for detecting the reflected light reflected by the Fabry-Perot interferometer;
Based on the detection result of the reflected light by the acoustic wave transmitted from the transducer and reflected in the subject and incident on the first mirror, the characteristic information in the subject is detected. A processing unit for acquiring
Have
The mask is disposed closer to the emission end than the surface of the first mirror opposite to the surface on which the acoustic wave is incident,
The mask is an object information acquiring apparatus characterized in that the mask is made of a material that absorbs the measurement light.

The present invention also employs the following configuration. That is,
A measurement light source that emits measurement light from the exit end; and
A Fabry-Perot interferometer composed of a first mirror on which an acoustic wave is incident and a second mirror on which the measurement light is incident;
A mask provided with openings in an array;
An optical sensor for detecting the reflected light reflected by the Fabry-Perot interferometer;
Have
The mask is disposed closer to the emission end than the surface of the first mirror opposite to the surface on which the acoustic wave is incident,
The mask is an acoustic wave receiving device characterized by comprising a material that absorbs the measurement light.

  ADVANTAGE OF THE INVENTION According to this invention, the technique for suppressing the shift | offset | difference of measurement light can be provided in the acoustic wave reception using a Fabry-Perot probe.

Diagram showing an example of the configuration of an imaging apparatus Diagram showing an example of the configuration of a Fabry-Perot probe and mask Diagram showing optical characteristics of mask The figure which showed the effect with respect to the optical shift of the in-plane direction by the mask The figure which showed the effect with respect to the optical shift of the perpendicular direction by the mask Diagram showing an example of the configuration of an imaging apparatus Diagram showing an example of the configuration of an imaging apparatus Diagram showing an example of the configuration of a Fabry-Perot probe and mask

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  The acoustic wave receiving apparatus of the present invention is an imaging using photoacoustic tomography technology that irradiates a subject with light (electromagnetic waves) and receives (detects) an acoustic wave generated and propagated in the subject according to the photoacoustic effect. Including equipment. The acoustic wave receiving apparatus of the present invention also transmits an acoustic wave such as an ultrasonic wave to the subject, and receives a reflected wave (echo wave) reflected and propagated inside the subject. including. The subject information acquiring apparatus of the present invention includes the acoustic wave receiving device described above, and acquires characteristic information in the subject using the acoustic wave.

In the case of a device using the former photoacoustic effect, the characteristic information is the distribution of the acoustic wave generated by light irradiation, the initial sound pressure distribution in the subject, or the optical energy absorption density derived from the initial sound pressure distribution. This shows the distribution, absorption coefficient distribution, and concentration distribution of substances constituting the tissue. The substance constituting the tissue is, for example, a blood component such as an oxygen saturation distribution or an oxidized / reduced hemoglobin concentration distribution, or fat, collagen, moisture, and the like.
In the case of an apparatus using the latter ultrasonic echo technique, the characteristic information is information reflecting a difference in acoustic impedance of the tissue inside the subject.

  In the acoustic wave receiving apparatus of the present invention, a device using a Fabry-Perot interferometer as a receiving element (probe, transducer) that receives photoacoustic waves can be suitably used. In the following description, an imaging apparatus that generates and displays image data based on acquired information will be described. However, the apparatus according to the present invention is not necessarily required to display the characteristic information, and may be stored as usable data.

  The acoustic wave referred to in the present invention is typically an ultrasonic wave and includes an elastic wave called a sound wave or an acoustic wave. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. An electric signal converted from an acoustic wave by the probe is also called an acoustic signal.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention can also be understood as an operation method and a control method of an acoustic wave receiving apparatus or an object information acquiring apparatus. The present invention can also be understood as a program for causing an information processing apparatus or the like to execute an operation method or a control method.

[Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.
The measurement light in the present invention includes incident light incident on the Fabry-Perot interferometer and reflected light guided to the photodiode by the Fabry-Perot interferometer. The measurement light is distinguished from the excitation light that irradiates the subject in order to generate an acoustic wave using the photoacoustic effect.

(Device configuration)
FIG. 1 is a diagram illustrating a configuration example of an imaging apparatus according to the present embodiment.
The imaging apparatus of this embodiment includes an excitation light source 101. The excitation light source 101 irradiates the subject 102 with excitation light 103. As a result, the photoacoustic wave 105 is generated by the light absorber 104 inside or on the surface of the subject absorbing part of the light energy. Examples of the light absorber inside the subject include tumors and blood vessels.

  The acoustic wave receiving apparatus of this embodiment includes a Fabry-Perot probe 106 for detecting the photoacoustic wave 105. A Fabry-Perot probe 106 is provided with a mask 107 having openings in an array. The Fabry-Perot probe 106 can detect the sound pressure of the photoacoustic wave 105 at the opening of the mask 107 by irradiating the measurement light 109 from the emission end of the array light source 108 as a measurement light source.

The acoustic wave receiving apparatus also includes a control unit 110 that controls the wavelength of the measurement light 109 emitted from the array light source 108 for each element or a plurality of elements.
The acoustic wave receiving apparatus also includes an optical sensor 111 for measuring the amount of reflected light of the measurement light 109 that has entered the resonant mirror of the Fabry-Perot probe 106 through the opening of the mask 107 and converts it into an electrical signal. .
The above is the basic component of the acoustic wave receiving apparatus.

An imaging device (subject information acquisition device) is configured by adding a processing unit 112 and a display unit 113 to the acoustic wave receiving device. The processing unit 112 performs signal processing such as analysis on the electrical signal obtained by the optical sensor 111. The display unit 113 displays object information such as an optical characteristic value distribution obtained by the processing unit.
The above is the basic configuration of the imaging apparatus including the acoustic wave receiving apparatus of the present embodiment.

(Light source and light emission)
As the array light source 108, a tunable laser that can control the wavelength for each element or a plurality of elements when emitting light is preferably used. Further, in order to increase the reflectance change when the acoustic wave enters the Fabry-Perot probe 106, it is desirable that the array light source 108 operates in a single mode. The array light source corresponds to the measurement light source of the present invention.

Further, it is desirable that the wavelength of the array light source 108 can be changed at least in a wavelength range equal to or larger than the FSR (Free Spectrum Range) of the Fabry-Perot probe 106. FSR is a wavelength interval between adjacent resonance wavelengths.
In addition, it is preferable that the array light source 108 can change the wavelength in a short time.
Further, using a one-dimensional array laser or a two-dimensional array laser as the array light source 108 is effective in shortening data acquisition.
As an array light source 108 suitable for the above requirements, there is a surface emitting laser (VCSEL) array.

The measurement light 109 generated by the array light source 108 is collected through the optical system 114 and enters the Fabry-Perot probe 106.
The spot size and irradiation interval of the measurement light 109 on the Fabry-Perot probe 106 are determined by the optical system 114. At that time, an optical system that irradiates the measurement light 109 to the position of the opening of the mask 107 is used. A telecentric lens can be used as such an optical system 114.

(Mask and probe)
FIG. 2A shows a Fabry-Perot probe 10 having a mask 107 according to this embodiment.
FIG. The mask 107 is provided with openings 201 arranged in an array. The mask 107 is disposed between the second mirror 203 and the substrate 205. The opening 201 corresponds to the opening of the present invention.

  In order to obtain the effect of the present invention, the formation position of the mask 107 in the Fabry-Perot interferometer is the surface on the inner side of the resonance mirror of the first mirror 202 on the side on which the acoustic wave is incident, or an array from the surface. It is preferable that the position be closer to the light source (that is, the emission end side). More preferably, the mask 107 is formed on any surface of the second mirror 203 on the measurement light incident side or on the surface opposite to the resonant mirror of the substrate.

  As a material of the first mirror 202 and the second mirror 203, a dielectric multilayer film or a metal film can be used. A spacer film 204 exists between the mirrors. The spacer film 204 is preferably one having a large distortion when an elastic wave is incident on a Fabry-Perot probe. For example, an organic polymer film is used. Parylene, SU8, polyethylene or the like can be used as the organic polymer film. However, as the spacer film 204, an inorganic film may be used as long as it is a film that deforms in the film thickness direction when a sound wave is received.

  However, when the organic polymer film is formed, the film thickness tends to vary. When there is variation in the cavity length, in order to keep the acoustic wave reception sensitivity within the probe plane constant, the wavelength of the measurement light is positioned with respect to the variation in the cavity length within the probe surface. It is necessary to adjust every time. In order to further increase the reception sensitivity, it is preferable to match the wavelength of the measurement light so that the reception sensitivity of the acoustic wave in the probe plane is maximized at each position.

The Fabry-Perot probe is preferably covered with a protective film except for the surface on which the measurement light is incident. As the protective film, an organic polymer film such as parylene or an inorganic film such as SiO ₂ formed into a thin film is used.
Glass or acrylic can be used for the substrate 205. At this time, in order to reduce the influence of light interference in the substrate 205, the substrate 205 is preferably wedge-shaped. Furthermore, in order to avoid reflection of light on the surface of the substrate 205, it is preferable to perform AR coating on the surface on which the measurement light is incident.

FIG. 2B is a diagram of the mask 107 viewed from the side on which the measurement light 109 is incident. Openings 201 are provided in an array.
In the present embodiment, a mask as shown in FIG. However, the number and arrangement of the openings may be arbitrarily formed according to the measurement object and the measurement range.

  The measurement light 109 is irradiated to the position of the opening 201 of the mask 107. The beam diameter of the measurement light 109 in the opening 201 is preferably larger than the size of the opening 201. At this time, since the spot diameter of the measurement light 109 irradiated to the resonant mirror of the Fabry-Perot probe 106 through the opening is determined by the size of the opening 201, one of the Fabry-Perot probes 106 depends on the size of the opening 201. The receiving area of one receiving element is determined. Therefore, it is necessary to determine the size of the opening 201 according to the necessary resolution.

  As shown in FIG. 3A, the measurement light 109 does not pass through portions other than the opening 201 of the mask 107. Further, if the measurement light 109 is reflected at a portion other than the opening 201 of the mask 107, detection of the measurement light 109 reflected by the Fabry-Perot probe 106 is hindered, so the material of the mask 107 absorbs the measurement light 109. Use what you want. The material of the mask 107 is preferably a material whose transmittance with respect to the measuring light 109 is 1.0% or less. More preferably, the mask 107 is made of a material having a transmittance with respect to the measuring light 109 of 0.5% or less. As such a material, pigments such as dyes and pigments can be used.

In the present embodiment, as shown in FIG. 3B, since the subject 102 is irradiated with the excitation light 103 from the Fabry-Perot probe 106 side, the mask 107 is made of a material that transmits the excitation light 103. Use. Note that the mask 107 is preferably made of a material having a transmittance of 90% or more for the excitation light 103. Further, as the material of the mask 107, it is more preferable to use a material having a transmittance with respect to the excitation light 103 of 95% or more.
However, unlike this embodiment, when the subject 102 is irradiated with the excitation light 103 from the opposite side of the Fabry-Perot probe 106, the excitation light 103 is not passed through the Fabry-Perot probe 106. It is also possible to irradiate the specimen 102. In that case, it is not necessary to use a material that transmits the excitation light 103 for the mask 107.

In order to provide the mask 107 between the second mirror 203 and the substrate 205, a method of forming a mask on the substrate 205 of the Fabry-Perot probe 106 can be used. As such a technique, a known display element color filter patterning technique can be used. For example, by forming a dye material having photosensitivity on a substrate by using a spin coating method or a printing method, and then irradiating ultraviolet rays using a photomask in which the opening is patterned, the opening is formed on the dye film. Can be produced.
In addition, a technique of patterning a dye on the Fabry-Perot probe 106 using an ink jet technique can also be used.

  After forming a mask on the substrate by these methods, the second mirror 203, the spacer film 204, the first mirror 202, and further a protective film (not shown) are formed in this order. As a result, a Fabry-Perot probe 106 having a mask 107 as shown in FIG.

(Operation and effect)
FIG. 4 is a diagram for explaining a technique for suppressing the optical positional deviation in the in-plane direction by using the mask of the present embodiment.

FIG. 4A shows a Fabry-Perot probe without a mask as a comparative example. It is assumed that the measurement light 401 indicated by the dotted line is shifted to the position of the measurement light 402 by applying mechanical vibration to the probe at the time of diagnosis. Reference numeral 403 represents the positional deviation in the in-plane direction of the light spot on the mirror 203 at this time.
Thus, the shift of the position of the light spot means that the position of the receiving element of the probe is shifted. As a result, the positional relationship between the subject and the probe is shifted during measurement, and problems such as blurring occur in the reconstructed image.

Further, if the interval between the light spots is shifted, the interval between the receiving elements changes, and the image quality deteriorates when an image is formed from the obtained signals.
Further, even if the optical system is distorted due to a drop impact or the like, a similar problem occurs, and a desired image cannot be obtained.

  On the other hand, FIG. 4B is a diagram showing the effect of this embodiment, and uses a Fabry-Perot probe having a mask 107. Even if the measuring beam 404 is shifted to the position of the measuring beam 405, no positional shift in the in-plane direction of the light spot on the mirror 203 occurs as indicated by reference numeral 406. Further, the interval between the light spots is also constant. As a result, it is possible to suppress the influence of mechanical vibration or the like on the acquired data, and to prevent image deterioration.

  FIG. 5 is a diagram for explaining a technique for well controlling the optical positional deviation in the incident direction of the measurement light (the deviation in the direction crossing the receiving surface) using the mask of this embodiment.

FIG. 5A shows a Fabry-Perot probe without a mask as a comparative example. Assume that the measurement light 501 indicated by the dotted line is shifted to the position of the measurement light 502. Reference numeral 503 indicates that the spot diameter of the light spot has changed on the mirror 203 at this time.
Thus, changing the spot diameter means changing the size of the receiving element of the probe. As a result, the resolution of the image changes during measurement. In addition, a change in the size of the receiving element also causes a change in the directivity of the element with respect to reception of acoustic waves.

On the other hand, FIG. 5B is a diagram showing the effect of this embodiment, and a Fabry-Perot probe having a mask 107 is used. Even if the measurement light 504 is shifted to the position of the measurement light 505, the spot diameter of the light spot on the mirror 203 does not change as indicated by 506. This suppresses changes in the spot diameter due to mechanical vibrations and improves the reproducibility of image resolution.
Further, since the change in spot diameter is suppressed and the size of the receiving element is kept constant, the change in element directivity can be suppressed.

  As described above, by providing the Fabry-Perot probe 106 with the mask 107, it is possible to suppress the deviation of the measurement light due to the optical system or the like. As a result, the reproducibility of resolution can be improved and image blurring can be reduced.

  In the present embodiment, as shown in FIG. 2A, the mask 107 is arranged between the second mirror 203 and the substrate 205. However, the mask 107 is not necessarily in this position. For example, as shown in FIG. 8, the same effect can be obtained even if a mask 107 is disposed on the surface of the substrate 205 opposite to the resonant mirror (the side on which the measurement light is incident). Also in this case, the mask 107 can be manufactured by utilizing the color filter patterning technique for display elements.

  When an acoustic wave enters the Fabry-Perot probe from the first mirror 202 side, the first mirror 202 is deformed, and the first mirror 202 and the second mirror 202 are deformed by deformation in the film thickness direction at this time. The cavity length with the mirror 203 changes.

(Example of preferred configuration)
As the array type photosensor 111, a two-dimensional array type, a one-dimensional array type photosensor, or a photodiode can be used. Examples of the array type optical sensor include a CCD sensor and a CMOS sensor. However, any other optical sensor may be used as long as it can measure the amount of reflected light of the measurement light 109 when the photoacoustic wave 105 enters the Fabry-Perot probe 106 and convert it into an electrical signal.

  A half mirror 115 is used as an optical system for guiding the measurement light 109 that has passed through the opening of the mask 107 and reflected by the resonance mirror to the optical sensor 111. These may be configured so that the amount of reflected light in the Fabry-Perot probe 106 can be measured. For example, a configuration using a polarizing mirror and a wave plate in place of the half mirror 115 can be adopted.

  As the excitation light 103 irradiated to the subject 102, light having a wavelength with a characteristic that is absorbed by a specific component among the components constituting the subject 102 is used. Pulse light can be used as the excitation light 103. The pulsed light is preferably on the order of several pico to several hundreds of nanoseconds, and when the subject is a living body, it is particularly preferable to use pulsed light of several nanometers to several tens of nanoseconds. The excitation light source 101 that generates the excitation light 103 is preferably a laser, but a light emitting diode, a flash lamp, or the like may be used instead of the laser.

  As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used. If a oscillating wavelength-convertable dye laser, OPO (Optical Parametric Oscillators) laser, titanium sapphire laser, alexandrite laser, or the like is used, the difference in optical characteristic value distribution depending on the wavelength can be measured.

  Regarding the wavelength of the light source to be used, a region of 700 nm to 1100 nm, which is less absorbed in the living body, is preferable. However, it is also possible to use a wavelength range wider than the above wavelength range, for example, a wavelength range from 200 nm to 1600 nm from ultraviolet to mid-infrared, and further terahertz waves, microwaves, and radio waves.

  In order to efficiently detect the photoacoustic wave 105 generated from the subject 102 with the Fabry-Perot probe 106, it is desirable to use an acoustic coupling medium between the subject 102 and the Fabry-Perot probe 106. . For example, an acoustic impedance matching gel is applied between the subject 102 and the Fabry-Perot probe 106. It is also possible to use water as the acoustic coupling medium. Moreover, the structure filled with the container which put the test object instead of apply | coating a matching gel and water can be employ | adopted.

  When the device is used for medical purposes, such as measurement using a part of the human body as a subject, an acoustic impedance matching gel is applied to the affected area, which is the subject, and the Fabry-Perot probe 106 is placed on the affected portion. And imaging. The acoustic coupling medium is not limited to the matching gel.

  The Fabry-Perot probe 106 detects the photoacoustic wave 105 as a change in the amount of reflected light of the measurement light 109 that has passed through the opening of the mask 107. The optical sensor 111 converts this light quantity change into an electrical signal.

The processing unit 112 preferably normalizes the obtained electrical signal using the light amount or the light amount change amount for each beam of the measurement light 109 emitted from the array light source 108. Thereby, the dispersion | variation in the receiving sensitivity in the surface of the Fabry-Perot probe 106 can be suppressed.
The processing unit 112 performs image reconstruction in order to obtain object information such as an optical characteristic value distribution from the obtained electrical signal distribution. As a reconstruction algorithm, universal back projection or phasing addition can be employed.

  When reconstruction is performed, information on the opening pattern of the mask 107 is used. For example, the calculation is performed using the position information of the opening as the reception position of the acoustic wave 105. By using the mask as in the present embodiment, parameters such as the receiving element interval and directivity required when performing image reconstruction are kept constant without changing. Therefore, it is possible to prevent image degradation that occurs when these parameters are different from the input values in reconstruction.

  The processing unit 112 obtains characteristic information such as an optical characteristic value distribution by calculation using a temporal change distribution of the electrical signal representing the intensity of the photoacoustic wave 105 and the amount of measurement light. Furthermore, it is preferable to generate image data to be displayed on the display unit. As the processing unit 112, an arbitrary one such as an information processing circuit or an arithmetic device that operates according to a program can be used.

  When light of a plurality of wavelengths is used as the excitation light 101, the optical coefficient in the living body is calculated for each wavelength, and those values and substances constituting the living tissue (glucose, collagen, oxidized / reduced hemoglobin, etc.) Compare the intrinsic wavelength dependence. Thereby, it is also possible to image the concentration distribution of the substance constituting the living body.

  Further, the subject information acquisition apparatus desirably includes a display unit 113 that displays image information obtained by signal processing. Any display such as a monitor can be used as the display unit.

  By using the imaging apparatus as described above, it is possible to suppress the deviation of the measurement light in the acoustic wave reception using the Fabry-Perot probe. Accordingly, in imaging using the Fabry-Perot probe 106, it is possible to improve the reproducibility of resolution and reduce image blurring.

[Embodiment 2]
FIG. 6 is a diagram illustrating a configuration example of the imaging apparatus according to the present embodiment.
The imaging apparatus according to the present embodiment receives acoustic waves using a light source that is not an array light source and a scanning mechanism that scans measurement light generated by the light source on a Fabry-Perot probe. Detailed description of the same configuration as that of the first embodiment will be omitted.

(Device configuration)
The imaging apparatus of this embodiment includes an excitation light source 601. The excitation light source 601 irradiates the subject 602 with excitation light 603. As a result, the photoacoustic wave 605 is generated by the light absorber 604 inside or on the surface of the subject absorbing part of the light energy. Examples of the light absorber inside the subject include tumors and blood vessels.

  The acoustic wave receiving apparatus of this embodiment includes a Fabry-Perot probe 606 for detecting the photoacoustic wave 605. A Fabry-Perot probe 606 is provided with a mask 607 having openings in an array. The Fabry-Perot probe 606 can detect the sound pressure of the photoacoustic wave 605 at the opening of the mask 607 by irradiating the measurement light 609 from the emission end of the light source 608 that is a measurement light source.

  The acoustic wave receiving apparatus also includes a scanning mechanism 610. The scanning mechanism 610 scans the measurement light 609 on the Fabry-Perot probe 606, so that the sound pressure of the photoacoustic wave 605 in each opening is detected. The scanning mechanism corresponds to the scanning means of the present invention.

The acoustic wave receiving apparatus also includes a control unit 611 that controls the wavelength of the measurement light 609 emitted from the light source 608.
The acoustic wave receiving apparatus also includes an optical sensor 612 for measuring the amount of reflected light of the measurement light 609 incident on the resonant mirror of the Fabry-Perot probe 606 through the opening of the mask 607 and converting it into an electrical signal.
The above is the basic component of the acoustic wave receiving apparatus.

An imaging device (subject information acquisition device) is configured by adding a processing unit 613 and a display unit 614 to the acoustic wave receiving device. The processing unit 613 performs signal processing such as analysis on the electrical signal obtained by the optical sensor 612. A display unit 614 displays object information such as an optical characteristic value distribution obtained by the processing unit.
The above is the basic configuration of the imaging apparatus including the acoustic wave receiving apparatus of the present embodiment.

(Light source and light emission)
As the light source 608, a wavelength tunable laser can be used. It is desirable that the wavelength of the light source 608 be changed at least in a wavelength range equal to or greater than the FSR (Free Spectrum Range) of the Fabry-Perot probe 606.
The light source 608 is preferably capable of changing the wavelength in a short time.

  Examples of the light source 608 suitable for the above requirements include an external cavity laser (ECL), a distributed feedback (DFB) laser, a distributed reflection (DBR) laser, and a surface emitting laser (VCSEL).

The measurement light 609 generated by the light source 608 enters the Fabry-Perot probe 606 through the scanning mechanism 610 and the optical system 615.
The scan mechanism 610 scans the measurement light 609 so that the measurement light 609 is irradiated onto the opening of the mask 607. As such a scanning mechanism 610, a galvanometer or a MEMS mirror can be used. The scanning mechanism 610 controls the scanning position by the control unit 611.

  The optical system 615 collects the measurement light 609 guided by the scanning mechanism 610 and irradiates the Fabry-Perot probe 606. At this time, the measurement light 609 is preferably irradiated perpendicularly to the mirror surface. As such an optical system 615, an achromatic lens can be used.

  As described above, in this embodiment, the irradiation position of the measurement light 609 is scanned by the scanning mechanism 610 and the optical system 615 and sequentially incident on each of the openings of the mask 607 arranged in an array. Thereby, the acoustic wave 605 incident on the Fabry-Perot probe 606 can be detected at each opening position.

  In the present embodiment, a Fabry-Perot probe and a mask as shown in FIG. However, the number and arrangement of the openings may be arbitrarily formed according to the measurement object and the measurement range. It is also possible to use a Fabry-Perot probe and a mask as shown in FIG.

  The measurement light 609 is irradiated to the position of the opening of the mask 607. The beam diameter of the measurement light 609 at the opening is preferably larger than the size of the opening. At this time, since the spot diameter of the measurement light 609 irradiated to the resonant mirror of the Fabry-Perot probe 606 through the opening is determined by the size of the opening, one reception of the Fabry-Perot probe 606 is received depending on the size of the opening. The receiving area of the element is determined. Therefore, it is necessary to determine the aperture size according to the required resolution.

  As the optical sensor 612, a photodiode can be used. However, any other optical sensor may be used as long as it can measure the amount of reflected light of the measurement light 609 when the photoacoustic wave 605 enters the Fabry-Perot probe 606 and convert it into an electrical signal. The electric signal obtained by the optical sensor 612 is preferably amplified by an amplifier.

  Note that a half mirror 616 is used as an optical system for guiding the measurement light 609 that has passed through the opening of the mask 607 and reflected by the resonant mirror of the Fabry-Perot probe 606 to the optical sensor 612. These may be configured so that the amount of reflected light in the Fabry-Perot probe 606 can be measured. For example, a configuration in which a polarizing mirror and a wave plate are used instead of the half mirror 616 can be adopted.

(Scan control)
The control unit 611 sets one of the openings of the mask 607 arranged in an array as a start position, and controls the scan mechanism 610 so that the measurement light 609 is first irradiated to the opening.

Next, the control unit 611 sets the wavelength of the light source 608 so that the reception sensitivity of the Fabry-Perot probe 606 is maximized. As a method of obtaining the optimum wavelength that maximizes the reception sensitivity at each aperture position, a method is conceivable in which the optimum wavelength is the wavelength at which the change in reflectance when the wavelength is swept is maximized. The optimum wavelength may be obtained in advance before measuring the acoustic wave, or may be obtained while measuring the acoustic wave.
In this state, light irradiation from the excitation light 603 to the subject 602 and reception of the generated acoustic wave 605 are performed.

  Thereafter, the control unit 611 controls the scanning mechanism 610 so that the measurement light 609 is irradiated to the position of the next opening, sets the optimum wavelength of the measurement light 609 at the position of the next opening, and similarly generates an acoustic wave. 605 is received. By repeating this, it is possible to obtain the distribution of acoustic waves incident on the Fabry-Perot probe at the positions of the openings arranged in an array.

  By using the imaging apparatus as described above, it is possible to suppress the deviation of the measurement light in the acoustic wave reception using the Fabry-Perot probe. Therefore, in imaging using the Fabry-Perot probe 606, it is possible to improve the reproducibility of resolution and reduce image blurring.

[Embodiment 3]
FIG. 7 is a diagram illustrating a configuration example of the imaging apparatus according to the present embodiment.
The imaging apparatus according to the present embodiment images an acoustic impedance distribution in a living body using an ultrasonic echo technique. Detailed description of the same configuration as that of the above embodiment is omitted.

(Device configuration)
The imaging apparatus of this embodiment includes a transducer 703 that irradiates a subject 701 with an elastic wave 702 and a pulsar 704 for driving the transducer 703.

  The acoustic wave receiving apparatus of this embodiment includes a Fabry-Perot probe 705. The Fabry-Perot probe 705 detects an elastic wave 706 reflected at the interface between tissues having different acoustic impedances, such as a tumor inside the subject 701.

  A Fabry-Perot probe 705 is provided with a mask 707 having openings in an array. The Fabry-Perot probe 705 can detect the sound pressure of the elastic wave 706 at the opening of the mask 707 by irradiating the measurement light 709 from the emission end of the array light source 708 as a measurement light source.

The acoustic wave receiving apparatus also includes a control unit 710 that controls the wavelength of the measurement light 709 emitted from the array light source 708 for each element or a plurality of elements.
The acoustic wave receiving apparatus also includes an optical sensor 711 for measuring the amount of reflected light of the measurement light 709 incident on the resonant mirror of the Fabry-Perot probe 705 through the opening of the mask 707 and converting it into an electrical signal. .
The above is the basic component of the acoustic wave receiving apparatus.

An imaging device (subject information acquisition device) is configured by adding a processing unit 712 and a display unit 713 to the acoustic wave receiving device. The processing unit 712 performs signal processing such as analysis on the electrical signal obtained by the optical sensor 711. The display unit 713 displays the acoustic impedance distribution information obtained by the processing unit.
The above is the basic configuration of the imaging apparatus including the acoustic wave receiving apparatus of the present embodiment.

The mask 705 is provided with openings arranged in an array.
Also in the present embodiment, the mask structure shown in FIG. 2 is used as in the first embodiment. However, the number and arrangement of the openings may be arbitrarily formed according to the measurement object and the measurement range. It is also possible to use a Fabry-Perot probe and a mask as shown in FIG.

  The measurement light 709 does not pass through portions other than the opening of the mask 707. In addition, if the measurement light 709 is reflected at a portion other than the opening of the mask 707, detection of the measurement light 709 reflected by the Fabry-Perot probe 705 is hindered, so the material of the mask 707 absorbs the measurement light 709. Use things. As such a material, pigments such as dyes and pigments can be used.

  By using the imaging apparatus as described above, it is possible to suppress the deviation of the measurement light in the acoustic wave reception using the Fabry-Perot probe. Therefore, in imaging using the Fabry-Perot probe 705, it is possible to improve the reproducibility of resolution and reduce image blurring.

  In order to efficiently detect the acoustic wave 706 reflected at the interface between tissues having different acoustic impedances in the subject 701 with the Fabry-Perot probe 705, the subject 701 and the Fabry-Perot probe 705 are interposed between them. It is desirable to use acoustic coupling media.

  In FIG. 7, water is used as the acoustic coupling medium, and acoustic matching is performed between the subject 701 disposed in the water tank 714 and the probe. However, the acoustic coupling medium is not limited to water. For example, an acoustic impedance matching gel may be applied between the subject 701 and the Fabry-Perot probe 705.

  Note that, when the apparatus is used for medical purposes such as measurement using a part of a human body as a subject, use of an acoustic impedance matching gel is preferable to using the water tank 714. In that case, an acoustic impedance matching gel is applied to the subject, that is, the affected part, and a Fabry-Perot probe 705 is disposed on the object to perform imaging. At this time, not only the matching gel but also any acoustic coupling medium can be used as long as acoustic matching can be achieved between the affected area and the Fabry-Perot probe 705.

  As signal processing for obtaining an acoustic impedance distribution from the obtained electrical signal distribution, phasing addition and the like can be considered. When performing signal processing, information on the opening pattern of the mask 707 is used. For example, the calculation is performed using the position information of the opening as the reception position of the elastic wave 705.

Any processing unit 712 may be used as long as it can store the distribution of the time change of the electrical signal representing the intensity of the elastic wave 706 and convert it into acoustic impedance distribution data by the arithmetic means. Good.
It is desirable to provide a display unit 713 that displays image information obtained by signal processing.

  By using the imaging apparatus as described above, it is possible to suppress the deviation of the measurement light in the acoustic wave reception using the Fabry-Perot probe. Therefore, in imaging using the Fabry-Perot probe 705, it is possible to improve the reproducibility of resolution and reduce image blurring.

[Example 1]
Next, an embodiment in which the present invention is applied to actual acoustic wave acquisition will be described. The imaging apparatus of the present example has the configuration described in the first embodiment.

In this embodiment, a sample in which an intralipid 1% aqueous solution is hardened with agar as a subject and a rubber wire having a diameter of 100 μm for absorbing light is disposed therein is used.

Dielectric multilayer films are used for the first mirror and the second mirror of the Fabry-Perot probe. This dielectric multilayer film is designed to have a reflectance of 95% or more in the light of 770-790 nm. The dielectric multilayer film is also designed to have a transmittance of 95% or higher at 1064 nm light.
The substrate of the Fabry-Perot probe is made of acrylic. Parylene C is used for the spacer film between the mirrors, and the film thickness is 30 μm. Further, Parylene C is used as a protective film for the probe.

A mask is formed between the substrate and the dielectric multilayer film. The mask is a color filter in which a dye is spin-coated on a substrate, and openings (parts where no dye is present) are provided in an array by photolithography. The size of the opening is 20 μm. A total of 400 openings, 20 rows in the vertical direction and 20 rows in the horizontal direction, are provided at intervals of 500 μm.
The filter used for the mask absorbs light of 700 nm to 800 nm and has a transmittance of 0.5% or less, while light having a transmittance of 90 nm to 1200 nm has a transmittance of 90% or more.

As a wavelength tunable light source that emits measurement light, a VCSEL array that is tunable in the vicinity of 780 nm is used. The number of arrays is 400 channels of 20 × 20, and the array pitch is 500 μm.
The outgoing light from each element of the VCSEL array passes through the telecentric lens and irradiates each aperture position of the mask. At this time, the beam diameter of the measurement light at the aperture is adjusted to be 40 μm. The measurement light (reflected light) reflected by the Fabry-Perot probe enters the CMOS camera by a half mirror and is measured.

In such an apparatus, the subject is irradiated with excitation light, and photoacoustic wave measurement is started. The excitation light source is an Nd: YAG laser, the repetition frequency of the emitted pulsed light is 10 Hz, the pulse width is 10 ns, and the wavelength is 1064 nm.
Thereafter, image reconstruction is performed by a universal back projection algorithm using the distribution of the electrical signal based on the detected photoacoustic wave. As a result, it is possible to image a rubber wire in Intralipid 1% agar which is a light diffusion medium.

[Example 2]
The imaging apparatus of the present example has the configuration described in the second embodiment.
Since the configuration of the Fabry-Perot probe and the mask of this embodiment are the same as those of the first embodiment, detailed description thereof is omitted.

  In this embodiment, a sample in which an intralipid 1% aqueous solution is hardened with agar as a subject and a rubber wire having a diameter of 100 μm for absorbing light is disposed therein is used.

As a wavelength tunable light source that emits measurement light, an ECL (External Cavity Laser) that is tunable in the vicinity of 780 nm is used.
A biaxial galvano scanner is used for scanning the measurement light.
Light emitted from the ECL passes through an achromatic lens and is irradiated to each opening position of the mask while scanning with a galvano scanner. At this time, the beam diameter of the measurement light at the aperture is adjusted to be 40 μm. The measurement light (reflected light) reflected by the Fabry-Perot probe is incident on the photodiode by the half mirror and measured.

In such an apparatus, the subject is irradiated with excitation light, and photoacoustic wave measurement is started. The excitation light source is an Nd: YAG laser, the repetition frequency of the emitted pulsed light is 10 Hz, the pulse width is 10 ns, and the wavelength is 1064 nm.
Thereafter, image reconstruction is performed by a universal back projection algorithm using the distribution of the electrical signal based on the detected photoacoustic wave. As a result, it is possible to image a rubber wire in Intralipid 1% agar which is a light diffusion medium.

[Example 3]
The imaging apparatus of the present example has the configuration described in the third embodiment.
Since the configuration of the optical system and the optical sensor of the present embodiment is the same as that of the first embodiment, detailed description thereof is omitted.

  In this example, the present invention is used to image a polyethylene wire having a diameter of 300 μm in which a 1% aqueous solution of intralipid is solidified with agar as a subject. Place the phantom underwater.

  Gold films are used for the first mirror and the second mirror of the Fabry-Perot probe. The substrate of the Fabry-Perot probe is made of acrylic. Parylene C is used for the spacer film between the mirrors, and the film thickness is 30 μm. Further, Parylene C is used as a protective film for the probe.

A mask is formed between the substrate and the dielectric multilayer film. The mask is a color filter in which a dye is spin-coated on a substrate, and openings are provided in an array by a photolithography method. The size of the opening is 20 μm. A total of 400 openings, 20 rows in the vertical direction and 20 rows in the horizontal direction, are provided at intervals of 500 μm.
The color filter used for the mask absorbs light of 700 nm to 800 nm and has a transmittance of 0.5% or less.

  As a wavelength tunable light source that emits measurement light, a VCSEL array that is tunable in the vicinity of 780 nm is used. The number of arrays is 400 channels of 20 × 20, and the array pitch is 500 μm.

  In such an apparatus, a subject is irradiated with elastic waves using a transducer having a center frequency of 20 MHz. The transducer is of a piezoelectric type and is made of PZT. The elastic wave is emitted as a pulse wave using a pulsar, and the repetition frequency of the elastic wave is 1 KHz.

  After that, the echo wave reflected by the elastic wave in the subject is measured by the Fabry-Perot probe, and the acoustic signal in the subject is analyzed by the reconstruction algorithm using phasing addition using the obtained signal. The impedance distribution is imaged. Thereby, the polyethylene wire in agar is imaged.

  As described above, it is possible to acquire an acoustic wave by applying the present invention even in an imaging apparatus using the ultrasonic echo technique.

As described above, in this specification, the configuration example related to the biological information imaging apparatus using the living body as the subject has been mainly described. According to this, for the diagnosis of tumors and vascular diseases and the follow-up of chemical treatment, it is possible to image the distribution of optical characteristic values in the living body and the concentration distribution of the substances constituting the living tissue obtained from the information. Thus, it can be used as a medical diagnostic imaging device.
Furthermore, it is easy for those skilled in the art to apply to a non-destructive inspection for a non-biological substance as a subject. As described above, the present invention can be widely used as an inspection apparatus.

  108: Array light source (measurement light source), 106: Fabry-Perot probe (Fabry-Perot interferometer), 202: first mirror, 203: second mirror, 107: mask, 201: aperture, 111: Optical sensor, 101: excitation light source, 112: processing unit

Claims (16)

A measurement light source that emits measurement light from the exit end; and
A Fabry-Perot interferometer composed of a first mirror on which an acoustic wave is incident and a second mirror on which the measurement light is incident;
A mask provided with openings in an array;
An optical sensor for detecting the reflected light reflected by the Fabry-Perot interferometer;
An excitation light source that emits excitation light;
Based on the detection result of the reflected light by the photoacoustic wave generated from the subject irradiated with the excitation light and incident on the first mirror, characteristic information in the subject is acquired. A processing unit to
Have
The mask is disposed closer to the emission end than the surface of the first mirror opposite to the surface on which the acoustic wave is incident,
The object information acquiring apparatus according to claim 1, wherein the mask is made of a material that absorbs the measurement light. The object information acquiring apparatus according to claim 1, wherein the mask is made of a material that transmits the excitation light. A measurement light source that emits measurement light from the exit end; and
A transducer for transmitting an acoustic wave to the subject;
A Fabry-Perot interferometer composed of a first mirror on which an acoustic wave is incident and a second mirror on which the measurement light is incident;
A mask provided with openings in an array;
An optical sensor for detecting the reflected light reflected by the Fabry-Perot interferometer;
Based on the detection result of the reflected light by the acoustic wave transmitted from the transducer and reflected in the subject and incident on the first mirror, the characteristic information in the subject is detected. A processing unit for acquiring
Have
The mask is disposed closer to the emission end than the surface of the first mirror opposite to the surface on which the acoustic wave is incident,
The object information acquiring apparatus according to claim 1, wherein the mask is made of a material that absorbs the measurement light. 4. The Fabry-Perot interferometer has a configuration in which a resonant mirror including the first mirror and the second mirror is formed on a substrate. 5. Subject information acquisition apparatus. The object information acquiring apparatus according to claim 4, wherein the mask is formed between the substrate of the Fabry-Perot interferometer and the resonant mirror. The object information acquiring apparatus according to claim 4, wherein the mask is formed on a surface of the substrate of the Fabry-Perot interferometer on a side opposite to the resonance mirror. The object information acquiring apparatus according to claim 1, wherein the mask is formed on the Fabry-Perot interferometer by film formation. The object information acquiring apparatus according to claim 1, wherein the measurement light source is an array light source. The object information acquiring apparatus according to claim 8, wherein the measurement light emitted from each array of the array light sources is irradiated to a position of each opening of the mask. The object information acquiring apparatus according to claim 8, wherein the measurement light emitted from the array light source has a diameter larger than the size of the opening when irradiated to the opening. The object information acquiring apparatus according to claim 8, wherein the array light source is a VCSEL array. The object information acquiring apparatus according to claim 1, further comprising a scanning unit that scans the measurement light emitted from the measurement light source on the Fabry-Perot interferometer. The object information acquiring apparatus according to claim 12, wherein the scanning unit irradiates the position of each opening of the mask with the measurement light. The object information acquiring apparatus according to claim 1, wherein the optical sensor is an array type optical sensor that converts an amount of the reflected light into an electrical signal. 15. The subject information acquiring apparatus according to claim 1, further comprising a display unit that displays characteristic information in the subject. A measurement light source that emits measurement light from the exit end; and
A Fabry-Perot interferometer composed of a first mirror on which an acoustic wave is incident and a second mirror on which the measurement light is incident;
A mask provided with openings in an array;
An optical sensor for detecting the reflected light reflected by the Fabry-Perot interferometer;
Have
The mask is disposed closer to the emission end than the surface of the first mirror opposite to the surface on which the acoustic wave is incident,
The acoustic wave receiving apparatus according to claim 1, wherein the mask is made of a material that absorbs the measurement light.

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