JP2003265473A - Ultrasonic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain multi-reflection of ultrasonic waves and to improve image quality of an ultrasonic image in an ultrasonic imaging apparatus having a photo detection type ultrasonic sensor and an ultrasonic transmitting function. <P>SOLUTION: This ultrasonic imaging apparatus includes an ultrasonic wave detecting part 20 for modulating light according to the applied ultrasonic wave, an optical transmission path 13 for guiding light to an ultrasonic detecting part, a driving signal generating circuit 71 for generating a driving signal, a vibrator 72 for generating an ultrasonic wave according to a driving signal generated by the driving signal generating circuit, and an ultrasonic wave transmission path 74 having a first end and a second end, which propagates ultrasonic waves generated by the vibrator from the first end to the second end, and transmits ultrasonic waves from the second end. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging apparatus used for medical diagnosis and nondestructive inspection by transmitting ultrasonic waves to a subject and receiving echo waves reflected from the subject. Regarding

[0002]

2. Description of the Related Art Conventionally, in an ultrasonic imaging apparatus, a PZT is used as an element (vibrator) for transmitting and receiving ultrasonic waves.
Piezoelectric ceramics represented by (lead zirconate titanate) and PVDF (polyvinylidene fluoride: polyvin)
A one-dimensional sensor array using a piezoelectric element including a polymer piezoelectric element such as yl difluoride has been generally used. A two-dimensional image is acquired by scanning a subject using such a one-dimensional sensor array, and a three-dimensional image is obtained by combining a plurality of two-dimensional images.

However, according to this method, since there is a time lag in the scanning direction of the one-dimensional sensor array,
Since the cross-sectional images at different times will be combined,
The composite image becomes blurry. Therefore, it is not suitable for a subject that targets a living body, such as when performing ultrasonic echo observation using an ultrasonic imaging device.

In order to obtain a high-quality three-dimensional image using ultrasonic waves, a two-dimensional sensor capable of obtaining a two-dimensional image without scanning the sensor array is required. However, in the case of manufacturing a two-dimensional sensor array using the above PZT or PVDF, it is necessary to perform fine processing of elements and wiring to a large number of fine elements, and it is difficult to further miniaturize and integrate the elements. . Even if these problems are solved, there are problems that crosstalk between elements is increased, the SN ratio is deteriorated due to increase in electrical impedance due to fine wiring, and the electrode portion of the fine element is easily broken. Therefore, it is difficult to realize a two-dimensional sensor array using PZT or PVDF.

On the other hand, there is also known a sensor of a type which converts a received ultrasonic signal into an optical signal and detects it. A fiber Bragg grating (abbreviated as FBG) is used as such a photo-detection type ultrasonic sensor
"Underwater Acoustic Sensor with TAKAHASHI
Fiber Bragg Grating "OPTICAL REVIEW Vol. 4, No.
6 (1997) P. 691-694), or using a Fabry-Perot resonator (abbreviated as FPR) structure (Tokyo Institute of Technology UNO et al., “Fabrication and Performance of a Fiber Opt”).
ic Micro-Probe for Megahertz Ultrasonic Field Meas
urement ”T. IEE Japan, Vol. 118-E, No. 11, '98). When a two-dimensional sensor array is manufactured using such an ultrasonic sensor, there is an advantage that electrical wiring to a large number of fine elements is unnecessary and good sensitivity can be obtained.

A photodetection type ultrasonic sensor having a two-dimensional detection surface is also known. For example, University C
"Transduction Mechani" by Beard et al.
smsof the Fabry-Perot Polymer Film Sensing Concept
for Wideband Ultrasound Detection "(IEEE Transac
tions on Ultrasonics, Ferroelectrics, and Frequenc
y control, Vol. 46, No. 6, November 1999) describes the use of a polymer film having a Fabry-Perot structure for ultrasonic detection. Since such a film-shaped ultrasonic sensor does not require processing for many fine elements, the cost can be suppressed.

By the way, since the photo-detection type ultrasonic sensor does not have an ultrasonic wave transmitting function, when an ultrasonic image pickup apparatus is manufactured using such an ultrasonic sensor, an ultrasonic wave transmitting function is added separately. I have to do it.

Japanese Patent Application Publication 2002-17723
Japanese Patent Laid-Open Publication No. 2004-242242 discloses a two-dimensional ultrasonic probe that does not require electrical wiring to a large number of microelements, does not cause an increase in crosstalk or electrical impedance, and has an ultrasonic wave transmitting function. There is disclosed an ultrasonic probe including a transmitting unit that transmits an ultrasonic signal and a receiving unit that receives the ultrasonic signal and that uses a method different from that of the transmitting unit. In this document, an ultrasonic probe having an ultrasonic wave transmitting / receiving function is realized by combining a light detecting ultrasonic sensor with a piezoelectric transmitting element.

Further, in such a photodetection type ultrasonic sensor, there is a problem that multiple reflection of ultrasonic waves occurs on the back side of the ultrasonic wave receiving surface. Here, the multiple reflection of ultrasonic waves will be described by taking a two-dimensional surface sensor by a light detection method as an example. As shown in FIG. 15A, the ultrasonic detecting element 100 includes a base material 101 and an ultrasonic sensitive section 102. In this example, the ultrasonic sensitive section 102 includes a total reflection mirror 103 and a half mirror 10.
4 and a Fabry-Perot resonator structure including a cavity 105 formed between the total reflection mirror 103 and the half mirror 104. The member forming the cavity 105 undergoes geometrical displacement when ultrasonic waves are applied.

The receiving surface 102 of this ultrasonic detecting element 100
Ultrasonic waves are applied to a while light is incident from the half mirror 104 side. Then, due to the change in the sound pressure of the ultrasonic waves, the optical path length L of the cavity 105 changes according to the position of the receiving surface 102a, and the intensity of the light reflected from the ultrasonic sensitive section 102 changes according to the position. By converting the intensity of the reflected light into the intensity of the ultrasonic wave, the intensity of the ultrasonic wave corresponding to the position of the receiving surface 102a can be detected.

Here, referring to FIG. 16 and FIG. 17A, an ultrasonic wave propagating from the medium and containing information about the object generates vibration at the position A, and also inside the ultrasonic detecting element 100. Propagate (ultrasonic wave US1). Subsequently, the ultrasonic wave US1 is reflected at the boundary surface (position B) opposite to the receiving surface 102a to generate vibration, and then returns to the receiving surface 102a again (ultrasonic wave US2). Further, the ultrasonic wave US2 is reflected by the receiving surface 102a to generate vibration, and propagates to the back surface of the receiving surface 102a again (ultrasonic wave US3). In this way, the ultrasonic detection element 100
In, the reflection is repeated until the propagated ultrasonic wave is attenuated. Due to this phenomenon, as shown in (b) of FIG. 17, from the ultrasonic detecting element 100, in addition to the signal related to the object to be originally detected (detection signal at the position A), a signal generated by multiple reflection ( The detection signals at the positions C and E are mixed.

[0012]

Such multiple reflection of ultrasonic waves is one of the causes for lowering the SN ratio in an ultrasonic image and deteriorating the image quality. For example, in an ultrasonic imaging apparatus that uses a piezoelectric element for transmitting and receiving ultrasonic waves, the ultrasonic wave is attenuated by connecting a backing material including a ferrite core or the like to the piezoelectric element. However,
In the photo-detection type ultrasonic wave receiving device, since it is necessary to consider the light transmittance, it is not possible to use a backing material similar to the conventional one.

Further, in the photo-detection type ultrasonic imaging apparatus, when the vibrator is arranged near the ultrasonic detecting section for transmitting the ultrasonic wave, the following problems occur. That is, in order to transmit ultrasonic waves, it is necessary to wire up to the position of the vibrator, and when combined with the ultrasonic detecting element of the photodetection method, the connection becomes complicated. Also, when power is supplied to the vibrator, heat is generated from the vibrator and wiring,
The detection sensitivity of the photodetection type ultrasonic detection element varies. Further, the vibration generated when the ultrasonic wave is transmitted from the vibrator propagates to the ultrasonic wave detection element, and the detection sensitivity of the ultrasonic wave detection element also fluctuates.

Therefore, in view of the above points, the present invention is an ultrasonic imaging apparatus that uses a photo-detection type ultrasonic sensor and has an ultrasonic wave transmission function, while suppressing multiple reflections of ultrasonic waves. The purpose is to simplify the structure of.

[0015]

In order to solve the above problems, an ultrasonic imaging apparatus according to the present invention includes an ultrasonic detecting section for modulating light based on an applied ultrasonic wave and an ultrasonic detecting section. An optical transmission line that guides light, a drive signal generation circuit that generates a drive signal, a vibrator that generates ultrasonic waves according to the drive signal generated by the drive signal generation circuit, and a first end and a second end are provided. And an ultrasonic wave transmission path that transmits the ultrasonic wave generated by the vibrator from the first end to the second end and transmits the ultrasonic wave from the second end.

According to the present invention, since the vibrator can be arranged on the main body side of the ultrasonic imaging apparatus by using the ultrasonic transmission path, it is not necessary to provide wiring near the ultrasonic detecting element, The structure of the probe can be simplified and downsized. Further, since the heat generated from the vibrator or the wiring is not conducted to the ultrasonic wave detecting element and the vibration during the ultrasonic wave transmission is not transmitted, the fluctuation of the detection sensitivity can be prevented. Furthermore, by attenuating the ultrasonic waves in the optical transmission path, it is possible to suppress multiple reflection of the ultrasonic waves.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same reference numerals are given to the same components, and the description thereof will be omitted.
FIG. 1 is a block diagram showing an ultrasonic imaging apparatus according to the first embodiment of the present invention. This ultrasonic imaging apparatus includes a drive signal generating circuit 71, a vibrator 72, and an ultrasonic wave transmitting end 73.
Includes and. The vibrator 72 is composed of a piezoelectric element or the like, and generates ultrasonic waves based on the drive signal generated by the drive signal generation circuit 71. This ultrasonic wave is transmitted from the ultrasonic wave transmitting end 73 toward the subject.

Further, this ultrasonic imaging apparatus has an ultrasonic detecting section 60, a light source 11, a demultiplexer 12, and a photodetector 15.
And imaging systems 16-18. Ultrasonic detector 6
0 includes an ultrasonic detecting element that converts the received ultrasonic signal into an optical signal.

As shown in FIG. 1, the ultrasonic probe (probe) 1 includes an ultrasonic wave transmitting end 73 and an ultrasonic wave detecting section 60. The ultrasonic probe 1 is directly applied to a subject to transmit and receive ultrasonic waves. The configurations and operations of these transmission system and reception system will be described later in detail.

Further, this ultrasonic imaging apparatus includes a signal processing section 81 and an A / D converter 82. The signal processing unit 81 processes the detection signal output from the photodetector 15, and the A / D converter 82 converts this into a digital signal. By such signal processing operation, a plurality of pieces of surface data based on the detection signal are formed.

The ultrasonic imaging apparatus also includes a primary storage section 83, an image processing section 84, an image display section 85, a secondary storage section 86, and a timing control section 80. The primary storage unit 83 stores a plurality of surface data. The image processing unit 84 calculates the
The dimensional data or the three-dimensional data is reconstructed, and processing such as interpolation, response modulation processing, and gradation processing is performed. The image display unit 85 is, for example, a display device such as a CRT or LCD, and displays an image based on the image data subjected to these processes. Further, the secondary storage unit 86 is
The data processed by the image processing unit 84 is stored.

The timing control unit 80 controls the drive signal generation circuit 71 so as to generate a drive signal at a predetermined timing, and also takes in the detection signal output from the photodetector 15 after a lapse of a fixed time from the transmission time. Then, the signal processing unit 81 is controlled. As described above, by controlling the drive signal and the detection signal, it is possible to limit the time period in which the detection signal is read and to optically detect the reflection of ultrasonic waves from a specific depth of the subject.

FIG. 2 is a schematic diagram showing the configuration of the transmission system and the reception system in this embodiment. As shown in FIG. 2, the ultrasonic detecting element 20 and a part of the plurality of ultrasonic transmission paths 74 arranged around the ultrasonic detecting element 20 are integrated to form the ultrasonic probe 1.

The vibrator 72 includes the piezoelectric element 7 and the electrode 8, and is connected to the drive signal generating circuit 71 by the wiring 9. One end of an ultrasonic transmission path 74 is connected to the vibrator 72. The other end of this ultrasonic transmission path constitutes an ultrasonic transmission end 73. The other end of the ultrasonic transmission path 74 is arranged on the same plane as the receiving surface of the ultrasonic detecting element 20 in the ultrasonic probe 1.

The piezoelectric element 7 is a piezoelectric ceramic typified by PZT (lead zirconate titanate), or PVDF (polyvinyl difluoride).
Ride) and the like, which are made of a material having piezoelectricity such as a polymer piezoelectric element.

When a voltage is applied to the electrode 8 of the vibrator 72 by sending a pulsed electric signal or a continuous wave electric signal from the drive signal generation circuit 71, the piezoelectric element 7 causes a slight mechanical vibration. Such mechanical vibrations generate ultrasonic pulses or continuous wave ultrasonic waves. The ultrasonic transmission path 74 is
The ultrasonic wave generated by the vibrator 72 is introduced from one end, transmitted, and transmitted from the ultrasonic wave transmitting end 73 toward the subject. Here, in order to acoustically apply braking to the surface of the vibrator 72 to which the ultrasonic transmission path 74 is not connected,
A backing material such as a ferrite core may be provided. As a result, the vibrations remaining after transmitting the ultrasonic waves are quickly attenuated, and the influence of crosstalk or the like can be suppressed.

As the ultrasonic wave transmission path 74, a member which is a medium for propagating ultrasonic waves and which can maintain flexibility as a cable is suitable, and for example, a member such as an optical fiber or a quartz rod is applicable. Further, in order to suppress the propagation loss of ultrasonic waves, it is desirable to cover the ultrasonic transmission path 74 with a member having high viscosity such as metal. Ultrasonic transmission line 74
May have a length of about 2 m according to the length of the optical transmission path 13.

In FIG. 2, for simplicity, 1
Only the set of transducers, wirings and drive signal generation circuits are shown. Further, the ultrasonic transmission path arranged in front of the ultrasonic detection element 20 is omitted.

On the other hand, as the light source 11, a tunable LD (laser diode) having a predetermined band (for example, 1.55 μm) is used. The demultiplexer 12 is composed of a half mirror, an optical circulator, a polarization beam splitter, or the like, and reflects the incident light incident from the first direction in the second direction and the reflection returning from the second direction. Light is passed in a third direction, which is different from the first direction. In this embodiment, a half mirror is used as the demultiplexer 12. The half mirror reflects incident light in a direction that forms an angle of approximately 90 ° with the incident direction, and transmits light that returns from a direction that forms an angle of approximately 90 ° with the incident direction. In this embodiment, lenses are provided as the imaging systems 16 to 18 in the front and rear stages of the half mirror.

The optical transmission line 13 guides the light passing through the demultiplexer 12 to the ultrasonic detecting element 20. As the optical transmission line 13,
A bundle fiber in which a large number (for example, 1024) of optical fibers are bundled is used. In the present embodiment, a large number of fibers are bundled according to the shape (for example, circular shape) of the receiving surface of the ultrasonic detecting element.

The tip of the optical transmission line 13 has a collimator 1
The optical axis is connected to the ultrasonic detecting element 20 via the optical axis 4. As the collimating unit 14, for example, a collimating lens array in which collimating lenses are arrayed is used.

The ultrasonic detecting element 20 has a two-dimensional receiving surface 20a which is distorted by the propagating ultrasonic wave, and the light incident on the ultrasonic detecting element 20 through the optical transmission line 13 and the collimating portion 14 is incident on the ultrasonic detecting element 20. Are modulated and reflected based on the ultrasonic waves applied to the receiving surface 20a. The light reflected from the ultrasonic detection element 20 passes through the collimator section 14 and the optical transmission path 13 again, passes through the demultiplexer 12, and enters the photodetector 15 having a plurality of pixels.

The photodetector 15 is a two-dimensional array photoelectric converter including a PDA (photodiode array), a MOS type sensor and the like. The photodetector 15 detects the light that has entered through the demultiplexer 12 from the corresponding position of the ultrasonic detection element 20 for each of a plurality of pixels, and outputs a detection signal according to the light intensity of each pixel. Here, the reflected light may be incident on the photodetector 15 directly or through an optical fiber or the like, or an imaging system 18 may be provided in the subsequent stage of the demultiplexer 12 and connected to the photodetector 15 via this. You may make it a statue.

Next, the structure of the ultrasonic detecting element 20 and the principle of ultrasonic detection will be described in detail with reference to FIG. The ultrasonic detection element 20 is a multilayer film sensor including a substrate 21 and a multilayer film 22 laminated on the substrate 21.

The substrate 21 is a film-shaped substrate that is distorted by receiving ultrasonic waves, and has a diameter of 2 cm, for example.
It has an area of a circle or more. A multilayer film 22 having a Bragg grating structure is formed on the substrate 21 by alternately stacking two types of material layers having different refractive indexes. FIG. 3 shows a material layer A having a refractive index n ₁ and a material layer B having a refractive index n ₂ .

When the pitch (interval) of the periodic structure of the multilayer film 22 is d and the wavelength of incident light is λ, the Bragg reflection condition is expressed by the following equation. However, m is an arbitrary integer. 2d · sin θ = mλ (1) where θ is the incident angle measured from the incident surface, and θ = π /
When it is set to 2, the following equation is obtained. 2d = mλ (2) The Bragg grating selectively reflects light of a specific wavelength that satisfies the Bragg reflection condition and transmits light of other wavelengths.

When the ultrasonic wave is propagated to the ultrasonic wave detecting element 20, the ultrasonic wave detecting element 20 is distorted along with the propagation of the ultrasonic wave, and the pitch d of the periodic structure changes at each position of the multilayer film 22. Along with this, the wavelength λ of the light that is selectively reflected changes. Regarding the reflection characteristics of Bragg grating,
Before and after the center wavelength having the highest reflectance (low transmittance), there is a tilted band in which the reflectance changes, and ultrasonic waves are applied while light having a center wavelength in the range of this tilted band is incident on the multilayer film 22. Then, the intensity change of the reflected light (or transmitted light) according to the intensity of the ultrasonic wave at each position on the receiving surface can be observed. By converting this intensity change of light into the intensity of the ultrasonic wave, the two-dimensional intensity distribution information of the ultrasonic wave can be acquired.

The material of the substrate 21 is quartz glass (S
Optical glass such as iO ₂ ) or BK7 (product of Schott) is used. Further, as the substances used for the material layers A and B, it is desirable to use a combination of substances having different refractive indexes of 10% or more. Examples of this include a combination of SiO ₂ and titanium oxide (Ti ₂ O ₃ ), a combination of SiO ₂ and tantalum oxide (Ta ₂ O ₅ ), and the like. The material layers A and B are formed on the substrate 21 by a method such as vacuum deposition or sputtering.

By the way, in order to suppress the multiple reflection of ultrasonic waves, it is effective to lengthen the propagation distance of ultrasonic waves. The ultrasonic wave is attenuated not a little when it propagates, and the amount of attenuation increases as the propagation distance increases. Therefore, if a sufficient propagation distance is taken, the ultrasonic wave propagated at one end can be sufficiently attenuated while being reflected and returned at the other end. Therefore, in the present embodiment, an optical fiber is used as the optical transmission line and the received ultrasonic wave is propagated to the optical fiber. That is, the optical transmission line is provided with a function as a backing portion for attenuating ultrasonic waves as well as a function of transmitting light.

FIG. 4 is an enlarged sectional view showing a part of the optical transmission line 13, the collimating portion 14 and the ultrasonic detecting element 20 shown in FIG. As shown in FIG. 4, the optical fibers 13a, 1 included in the optical transmission line (bundle fiber) 13
3b, ..., and collimating section (collimating lens array)
The collimator lenses 14a, 14b, ... Included in 14 are connected so that their optical axes are aligned with each other, and are further arranged two-dimensionally and connected to the ultrasonic detecting element 20.
The optical fibers 13a, 13b, ... Are bundled with an adhesive 25.

The optical fiber 13a is, for example, a single mode or multimode fiber having a length of about 2 m, and has a low viscosity member (coating material 23) containing a resin material.
Covered with a). By covering the optical fiber with the above-mentioned member in order to attenuate the ultrasonic wave while propagating through the optical fiber, it is possible to further increase the propagation energy loss of the ultrasonic wave and accelerate the ultrasonic wave attenuation.

The light transmitted through the optical fiber 13a is diffracted when it is emitted from the optical fiber. Therefore, if the optical fiber 13a is directly connected to the ultrasonic detecting element 20, the light is diffused and the light reflection characteristic of the ultrasonic detecting element is significantly disturbed, and sufficient interference does not occur in the ultrasonic detecting element. For this reason, the detection sensitivity of the ultrasonic detecting element is significantly deteriorated. In order to avoid this phenomenon, the optical fiber 13
A collimator lens 14a is connected to one end of a in order to prevent diffusion of emitted light.

As the collimating lens 14a, a gradient index lens (gradient in
dex length, hereinafter abbreviated as GRIN lens) is used. The GRIN lens is, for example, a Selfoc (S
elfoc: a registered trademark of Nippon Sheet Glass Co., Ltd.), known as the product name. The GRIN lens is a gradient index lens having a different refractive index depending on the position, and its optical characteristics are changed by changing its length. For example, when the GRIN lens has a length of ¼ of the object image plane distance (pitch at which light is erectly imaged), incident light is emitted as parallel light.

In the present embodiment, the Selfoc lens array NA0.
46 (a product of Nippon Sheet Glass Co., Ltd.) is used with a length of 0.25 L (L is a distance between object image planes), and the respective Selfoc lenses are collimating lenses 14a, 14b ,.
As an optical fiber.

As shown in FIG. 4, the collimating lens 14
You may cover a with the coating material 23a. Optical fiber 1
This is because the ultrasonic waves are attenuated quickly as in the case of 3a.

The optical fiber and the collimator lens, or the collimator lens and the ultrasonic detecting element are connected by fusion or adhesive. When using an adhesive, it is desirable to use a resin adhesive containing an epoxy. In such an adhesive, since the acoustic impedance is similar to that of the members of the optical fiber and the collimating lens and the substrate of the ultrasonic detecting element, it is possible to suppress the reflection at the boundary of each member when the ultrasonic wave propagates. Because you can. Also, an adhesive 25 for bundling a plurality of optical fibers
Also, it is desirable to use a resin adhesive containing an epoxy. This is because it is possible to attenuate ultrasonic waves, prevent crosstalk of ultrasonic waves between adjacent optical fibers, and maintain flexibility as a cable. In this embodiment, as such an adhesive, STYCA
ST (a product of Emerson & Cuming) is used.

Next, the structure of the ultrasonic probe will be described with reference to FIG. FIG. 5 shows an ultrasonic probe 1.
3 is a front view of the inside of the housing of FIG. In the housing 35 of the ultrasonic probe 1, a part of the ultrasonic transmission path 74 and the ultrasonic detection element 20 connected to the optical transmission section 13 via the collimator section 14 are housed. .

The ultrasonic transmission path 74 and the ultrasonic detecting element 20.
It is desirable to provide an acoustic matching layer 36 between the housing and the housing 35 in order to achieve matching of acoustic impedance. The acoustic matching layer 36 can be made of Pyrex glass (registered trademark of Pyrex Co., Ltd.) or an epoxy resin containing metal powder, which easily transmits ultrasonic waves. In addition, it is desirable to provide an acoustic lens material 37 such as silicon rubber on the surface of the housing 35 so as to protect the ultrasonic transmission path 74 and the ultrasonic detecting element 20. In addition, inside the housing 35, the ultrasonic transmission path 74 and the ultrasonic detection element 20 are provided.
The resin 38 is solidified except in the vicinity of the portion where is provided.

FIG. 6 shows a plan view of the ultrasonic probe 1. In the present embodiment, as shown in FIG. 6A, a plurality of ultrasonic wave transmitting ends 73 are arranged around the ultrasonic wave detecting element 20, but in FIG. 6B or 6C. As shown, the receiving surface of the ultrasonic detecting element 20 may be arranged so as to surround one or a plurality of ultrasonic transmitting ends 73. As shown in FIG. 6B, when one ultrasonic wave transmitting end 73 is arranged at the center of the ultrasonic wave detecting element 20, beam scanning of the transmitted wave cannot be performed. On the other hand, FIG.
Alternatively, as shown in (c), when a plurality of ultrasonic wave transmitting ends 73 are arranged in the ultrasonic wave detecting element 20 one-dimensionally or two-dimensionally, one-dimensional or two-dimensional beam scanning transmission becomes possible. . In addition, in FIGS. 6A to 6C, it is desirable to fill the periphery of the ultrasonic wave transmitting end 73 and the ultrasonic wave detecting element 20 with the sound absorbing material 39 in order to reduce the crosstalk of the ultrasonic wave. As the sound absorbing material 39, epoxy resin containing metal powder, rubber containing ferrite powder, or the like is suitable.

When the ultrasonic wave transmitting end 73 and the ultrasonic wave detecting element 20 are arranged as shown in FIG. 6C, for example, an ultrasonic wave probe can be manufactured as follows. . FIG. 7 is a diagram for explaining an example of a method for manufacturing an ultrasonic probe.

FIGS. 7A to 7C show cross sections taken along the line AA 'in FIG. 6C. First, as shown in FIG. 7A, a substrate 2 made of optical glass or the like is used.
1, a plurality of openings are formed. Next, as shown in FIG. 7B, two kinds of material layers having different refractive indexes are alternately laminated on the lower surface of the substrate 21 in the drawing,
A multilayer film 22 having a Bragg grating structure is formed. Next, as shown in (c) of FIG. 7, the ultrasonic transmission path 74 is inserted into the opening of the substrate 21, and the ultrasonic detection element 2 is inserted.
The collimator 14 and the optical transmission line 13 are connected to 0. Thereby, the receiving surface of the ultrasonic detecting element 20 is formed so as to surround the ultrasonic transmitting end 73. At this time, the sound absorbing material 3 is placed in the gap between the ultrasonic transmission path 74 and the ultrasonic detecting element 20.
9 or an epoxy adhesive or the like may be filled.

A modified example of this embodiment will be described with reference to FIG. In this example, an ultrasonic wave detecting element (etalon sensor) 30 shown in FIG. 8 is used instead of the ultrasonic wave detecting element 20 in FIG. Other configurations are similar to those described with reference to FIGS. 2 and 4.

As shown in FIG. 8, the substrate 31 is a film-shaped substrate which is deformed by ultrasonic waves. A substrate 32 is arranged so as to face the substrate 31, and these have the same structure as the etalon.

When the reflectance of the substrates 31 and 32 is R, the distance between these substrates is d, and the wavelength of the incident light is λ, the transmittance of the etalon is expressed as follows. However, n is an arbitrary integer. T = {1 + 4R / (1-R) ² · sin ² (φ / 2)} ⁻¹ (3) φ = 2π / λ · 2nd · cos θ (4) where θ is measured from the perpendicular of the exit surface. The exit angle is θ
When = 0, the following formula is obtained. φ = 4πnd / λ (5) The etalon transmits the light of wavelength λ with the transmittance T and the reflectance R
= (1-T) is reflected.

When an ultrasonic wave is propagated to the ultrasonic detecting element 30, the substrate 31 is distorted, and the substrate 31 is deformed at each position on the receiving surface.
Since the distance d between 32 and 32 changes, the reflectance of light of wavelength λ changes. The reflection characteristic of the etalon changes periodically with a change in wavelength. When the ultrasonic wave is applied while the light having the central wavelength is incident on the substrate 31 in the region where the rate of change of the reflection characteristic is large, the intensity change of the reflected light according to the intensity of the ultrasonic wave at each position on the receiving surface can be observed. The intensity of the ultrasonic wave can be two-dimensionally measured by converting the intensity change of the reflected light into the intensity of the ultrasonic wave.

Next, an ultrasonic imaging apparatus according to the second embodiment of the present invention will be described with reference to FIG. In the ultrasonic imaging apparatus according to this embodiment, the transducer and the ultrasonic transmission path in the first embodiment are also used for transmitting and receiving ultrasonic waves. As shown in FIG. 9, a detection signal processing circuit 75 is connected to the transducer 72 of this ultrasonic imaging apparatus. In addition, the ultrasonic probe 2 is formed by the ultrasonic detecting unit 60 and the ultrasonic transmitting / receiving end 76.
Other configurations are similar to those of the first embodiment.

The vibrator 72 vibrates based on the signal generated from the drive signal generating circuit 71 and generates ultrasonic waves. This ultrasonic wave is transmitted toward the ultrasonic wave transmitting / receiving end 76 via the ultrasonic wave transmission path 74. Further, this ultrasonic wave is transmitted from the ultrasonic wave transmitting / receiving end 76 toward the subject. The echo wave reflected from the subject is received by the ultrasonic wave detecting section 60 and also received by the ultrasonic wave transmitting / receiving end 76. The echo wave received by the ultrasonic wave transmitting / receiving end 76 is transmitted to the transducer 72 via the ultrasonic wave transmission path 74.
The vibrator 72 vibrates by the ultrasonic waves transmitted by the ultrasonic transmission path 74 and generates an electric signal.

The detection signal processing circuit 75 performs processing such as amplification on the detection signal input from the vibrator 72, and outputs it to the signal processing unit 81. Under the control of the timing control unit 80, the signal processing unit 81 takes in the detection signal output from the detection signal processing circuit 75 after a lapse of a certain time from the transmission of ultrasonic waves. This detection signal is processed by the signal processing system subsequent to the signal processing unit 81 in the same manner as the signal detected by the light detection method.

According to this embodiment, the ultrasonic wave is received from the ultrasonic wave transmitting / receiving end in addition to the ultrasonic wave detecting portion, so that the ultrasonic wave receiving area in the ultrasonic probe is expanded and the amount of information is increased.

Next, an ultrasonic imaging apparatus according to the third embodiment of the present invention will be described with reference to FIG.
FIG. 10 is a diagram showing the configurations of the transmission system and the reception system in this embodiment. In this embodiment, a backing section 50 is used instead of the optical transmission line 13 and the collimating section 14 in FIG. Other configurations are similar to those of the first embodiment.

The backing section 50 includes an optical transmission section 51 that transmits light used for detection and a coating section 52 for attenuating ultrasonic waves. A member such as optical glass is used for the optical transmission unit 51. Further, for the covering portion 52, a member having low viscosity such as resin, rubber or liquid is used. The backing section 50 and the ultrasonic detecting element 20 as described above are
They are connected by a resin adhesive such as epoxy.

In the receiving system shown in FIG. 10, the light emitted from the light source 11 passes through the lens 16, is redirected by the demultiplexer 12, and then passes through the lens 17 to enter the optical transmission section 51. . This light is reflected from the ultrasonic detecting element 20 and is modulated based on the applied ultrasonic wave. The reflected light passes through the lens 17, the demultiplexer 12, and the imaging system 18, enters the photodetector 15, and is detected.

On the other hand, the ultrasonic waves applied to the ultrasonic detecting element 20 are transferred to the inside of the ultrasonic detecting element 20 and the backing portion 5.
Propagate to 0. In the backing section 50, the ultrasonic waves are
Energy is lost when propagating through the optical transmission section 51, and the energy is absorbed by the coating section 52 and rapidly attenuated. This can reduce the effect of multiple reflection of ultrasonic waves.

According to the present embodiment, unlike the case where light is guided to the ultrasonic detecting element by a plurality of optical fibers corresponding to respective pixels, a predetermined thickness (irradiation area) is applied to the reflecting surface of the ultrasonic detecting element. ) Is guided, the structure of the receiving system can be simplified. In the present embodiment, the light passing through the lens 17 shown in FIG. 10 is directly incident on the optical transmission section, but it is incident on the optical transmission section via the optical fiber or the collimating section as shown in FIG. May be. Further, a collimator section may be inserted between the optical transmission section 51 and the ultrasonic detection element 20. Further, in the present embodiment, the multilayer film sensor shown in FIG. 3 is used as the ultrasonic detecting element, but the etalon sensor shown in FIG. 8 may be used.

Next, an ultrasonic imaging apparatus according to the fourth embodiment of the present invention will be described with reference to FIG.
In the present embodiment, the ultrasonic detection element 2 shown in FIG.
0, the optical transmission path 13, and the collimating section 14, a bundle fiber 40 having an ultrasonic sensitive section shown in FIG. 11A is used, and a plurality of ultrasonic transmission paths 74 are arranged around the bundle fiber 40. ing. Other configurations are the same as those in the first embodiment.

FIG. 11B shows the bundle fiber 40.
The structure of the fiber 40a included in FIG. Fiber 40
A includes an optical fiber 41a and a collimator lens 42a. In the present embodiment, as in the first embodiment, as the collimating lens 42a,
A SELFOC lens having a length of 0.25L is used. Further, the both are connected by fusion or a resin-based adhesive containing an epoxy.

At one end of the collimator lens 42a, a multilayer film 43a in which two kinds of material layers are alternately laminated is formed. This multilayer film 43a constitutes a Bragg grating structure and acts as an ultrasonic sensitive section. Multilayer film 4
As the material of 3a, for example, a combination of SiO ₂ and titanium oxide (Ti ₂ O ₃ ) or a combination of SiO ₂ and tantalum oxide (Ta ₂ O ₅ ) is used. Such a material layer is formed on the collimator lens 42a by vapor deposition.

The fiber 40a has a low-viscosity member (coating material 44) so that the ultrasonic wave propagated to one end of the fiber 40a is attenuated before being reflected at the other end.
covered by a). Further, as shown in FIG. 11B, the covering material 44a may cover the collimator lens 42a. Thereby, the fiber 40a
Since it is possible to increase the energy loss of the ultrasonic waves propagated to, it is possible to quickly attenuate the ultrasonic waves and improve the effect as a backing material.

Such fibers 40a, 40b, ...
Are bundled together using an epoxy-based resin adhesive or the like to form a bundle fiber 40 having an ultrasonic sensitive section.
Is created. Bundle fiber 40 and ultrasonic transmission path 7
When making an ultrasonic probe by combining 4 and
As shown in FIG. 11A, a plurality of ultrasonic transmission paths 74 may be arranged around the bundle fiber 40. Further, as shown in FIG. 11C, one or a plurality of ultrasonic transmission paths 74 may be arranged between the fibers 40a, 40b, .... In this case, the ultrasonic transmission path can be arranged at a desired position of the bundle fiber.

According to this embodiment, since the multilayer film is formed directly on the collimator lens, the strength at the connecting portion between the collimator lens and the ultrasonic detecting element is increased. Further, since the reflection of the ultrasonic wave at the connecting portion is suppressed, the ultrasonic wave is easily released to the fiber portion, and the multiple reflection can be effectively suppressed. Further, since the ultrasonic probe is composed of the optical transmission line to which the collimator lens is connected and the ultrasonic transmission line, the size of the probe can be further reduced.

In the first to fourth embodiments described above, the ultrasonic wave detection performance can be improved by adding an optical amplifier. This modified example is shown in FIG.
This will be described with reference to 2. The ultrasonic imaging apparatus shown in FIG. 12 is obtained by adding at least one of an optical amplifier 91 and an optical amplifier 92 to the ultrasonic imaging apparatus shown in FIG. The optical amplifier 91 is arranged between the light source 11 and the demultiplexer 12 or between the lens 16 and the demultiplexer 12, and the light source 1
The light incident from 1 is amplified and emitted to the demultiplexer 12. On the other hand, the optical amplifier 92 is arranged between the demultiplexer 12 and the image forming system 18, and amplifies the light incident from the demultiplexer 12 to form the image forming system 1.
Emit to 8. When the image forming system 18 is not used, the optical amplifier 92 is arranged between the demultiplexer 12 and the photodetector 15, and amplifies the light incident from the demultiplexer 12 to amplify the light.
Emit to.

As the optical amplifier, for example, an optical fiber amplifier EDFA (Er) doped with erbium (Er) is used.
-Doped Optical Fiber Ampl
ifer) is used. This EDFA can increase the light intensity by about one to two digits.

When such an optical amplifier is arranged between the light source 11 and the ultrasonic detecting element 20, the intensity of the incident light incident on the ultrasonic detecting element 20 is amplified. Further, when the optical amplifier is arranged between the ultrasonic detecting element 20 and the photodetector 15, the intensity of the incident light incident on the ultrasonic detecting element 20 does not change, but the reflection incident on the photodetector 15 does not change. The intensity of light is amplified. In this case, the intensity change of the reflected light modulated by the received ultrasonic wave is also amplified.

In any case, since the amount of reflected light entering the photodetector 15 increases by amplifying the intensity in the light state, the influence of electrical noise on the photodetector 15 is reduced, and It is possible to improve the SN ratio of the sound wave imaging device. Furthermore, when both are used in combination, it is possible to further improve the SN ratio.

In the first to fourth embodiments,
As a light source, a broadband light source can be used instead of the tunable LD. This modification will be described with reference to FIGS. 13 and 14.

In FIG. 13, the light generated from the broadband light source is used by narrowing the band with a band narrowing filter. As a broadband light source, for example, an ASE (Amplify) that emits amplified spontaneous emission light is used.
An ed Spontaneous Emission) light source or a broadband fiber light source can be used. In FIG. 13, as the broadband light source, A
The SE light source 93 is used. The ASE light source 93 is a broadband optical amplifier (Broadband Optical F).
This is a modification of the structure of the iber Amplifer) so that amplified spontaneous emission light can be generated. For details of the broadband optical amplifier, see, for example, "Broadband Optical Amplifier" by Haruki Ogoshi (Journal of the Institute of Electronics, Information and Communication Engineers, Vol.
2, No. 7, p. 718-724, July 1999)
Please refer to.

Referring now to FIG. 14, FIG.
The ASE light source 93 of FIG. 13 is shown in principle. ASE
The light source 93 includes an optical fiber 96 for optical amplification.
A lens 97 is attached to one end of the optical fiber 96, and a Bragg grating portion 98 for reflecting excitation light is formed on the other end. A laser oscillator 99 is arranged as an excitation light source on the left side of the lens 97 in the figure. The light generated in the laser oscillator 99 enters the optical fiber 96 via the lens 97 and is amplified, and a part of the amplified light is transmitted through the Bragg grating 98 as spontaneous emission light.

Referring again to FIG. 13, the ASE light source 93
The light generated by is incident on the demultiplexer 94. Duplexer 94
Allows the light incident from the first direction to pass in the second direction, and allows the reflected light returning from the second direction to pass in the third direction different from the first direction. In FIG. 13,
Although a half mirror is used as the demultiplexer 94, an optical circulator or a polarization beam splitter may be used instead.

In the direction in which the light emitted from the ASE light source 93 passes through the demultiplexer 94 (the lower side of the figure), a narrow band filter 95 made of the same material as the ultrasonic detecting element 20 is provided. The light that has entered the narrow band filter 95 is reflected by the multilayer film having the Bragg grating structure included in the narrow band filter 95, and then enters the demultiplexer 94 again.
The spontaneous emission light generated from the ASE light source 93 is narrowed in band by passing through the narrowband filter 95.

The light reflected by the narrow band filter 95 again enters the demultiplexer 94, the course of which is changed, and enters the demultiplexer 12. The light that has passed through the demultiplexer 12 enters the ultrasonic detection element 20 and is modulated by the applied ultrasonic waves.

Here, in the Bragg grating part, the center wavelength of the reflected light is 0.01 nm / ° C. due to a change in temperature.
Changes at a rate of. Therefore, if a light source that emits a laser beam of a single wavelength is used, there is a problem that the sensitivity of the ultrasonic detection element 20 that is configured by the Bragg grating portion greatly changes due to the temperature change.

However, as shown in FIG.
The spontaneous emission light generated from the E light source 93 is used as the narrow band filter 9
When the band is narrowed by 5, it is possible to secure a band close to that of a laser beam having a single wavelength and reduce a change in sensitivity of the ultrasonic detection element due to a change in temperature.

That is, the narrow band filter 95 and the ultrasonic detecting element 20 are formed of the same material, and, for example, the narrow band filter 95 and the ultrasonic detecting element 20 are connected by a material having high thermal conductivity, Bandpass filter 95 and ultrasonic detection element 20
By physically bringing the and into close proximity to each other, thermal coupling is achieved. Alternatively, the narrow band filter 95 and the ultrasonic detection element 20
A heat pipe may be arranged around and.

As a result, the Bragg grating portion of the narrow band filter 95 and the Bragg grating portion of the ultrasonic detecting element 20 have almost the same temperature, so that even if the reflection characteristic of the ultrasonic detecting element 20 is shifted by the temperature,
Similarly, the wavelength of the light incident on the ultrasonic detecting element 20 can be shifted to reduce the change in the sensitivity of the ultrasonic detecting element.

[0085]

As described above, according to the present invention, by using the ultrasonic transmission path, the vibrator can be arranged on the main body side of the ultrasonic imaging apparatus, so that it is necessary to wire up to the vibrator. Is eliminated, and the structure of the probe can be simplified and downsized. Further, since it is not necessary to supply electric power to the probe, it is not necessary to be affected by heat generated in the vibrator and wiring. As a result, the detection error due to the temperature change of the ultrasonic detection element can be reduced. Therefore, particularly in medical diagnosis, it is possible to improve electrical safety and thermal safety for the subject (patient). Furthermore, since it is possible to reduce the influence of vibration of the vibrator on the ultrasonic detecting element during ultrasonic wave transmission, it is possible to prevent fluctuations in detection sensitivity. Further, by attenuating the ultrasonic wave in the optical transmission line, it is possible to suppress the multiple reflection of the ultrasonic wave. This makes it possible to obtain a detection signal with a high SN ratio and obtain an ultrasonic image with good image quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an ultrasonic imaging apparatus according to a first embodiment of the present invention.

2 is a schematic diagram showing a configuration of a transmission system and a reception system included in the ultrasonic imaging apparatus of FIG.

FIG. 3 is a diagram for explaining an ultrasonic wave detection principle of the ultrasonic wave detection element shown in FIG.

FIG. 4 is an enlarged cross-sectional view showing a connection portion of the ultrasonic wave detection element, the collimator portion, and the optical transmission line shown in FIG.

5 is a plan view showing the structure of the ultrasonic probe shown in FIG. 2. FIG.

6A to 6C are diagrams showing an arrangement example of an ultrasonic detection element and an ultrasonic transmission path.

FIG. 7 is a diagram showing an example of a method of manufacturing an ultrasonic probe when the receiving surface of the ultrasonic detecting element is arranged so as to surround the ultrasonic transmitting end.

8 is a diagram showing a modification of the ultrasonic imaging apparatus shown in FIG.

FIG. 9 is a block diagram showing a configuration of an ultrasonic imaging apparatus according to a second embodiment of the present invention.

FIG. 10 is a schematic diagram showing a part of an ultrasonic imaging apparatus according to a third embodiment of the present invention.

FIG. 11 is a schematic diagram showing a part of an ultrasonic imaging apparatus according to a fourth embodiment of the present invention.

FIG. 12 is a diagram showing a modification of the ultrasonic imaging apparatus according to the first to fourth embodiments of the present invention.

FIG. 13 is a diagram showing another modification of the ultrasonic imaging apparatus according to the first to fourth embodiments of the present invention.

14 is a diagram showing a configuration of the ASE light source shown in FIG.

FIG. 15 is a diagram for explaining multiple reflection of ultrasonic waves in a photo-detection type ultrasonic detection element.

FIG. 16 is a waveform diagram showing vibrations generated at positions A to E in the ultrasonic detection element.

FIG. 17 is a position A detected by an ultrasonic detecting element,
It is a wave form diagram which shows the detection signal in C and E.

[Explanation of symbols]

1 and 2 ultrasonic probe 7 Piezoelectric element 8 electrodes 9 wiring 11 light source 12,94 duplexer 13 Optical transmission line 13a, 13b, ..., 96, optical fiber 14 Collimating part 14a, 14b, ... Collimating lens 15 Photodetector 16, 17, 97 lenses 18 Imaging system 20, 30, 100 Ultrasonic detector 20a, 102a Receiving surface 21, 31, 32 substrates 22, 43a, 43b, ... Multilayer film 23a, 23b, ... Coating material 25 adhesive 35 housing 36 Acoustic matching layer 37 Acoustic lens 38 resin 39 Sound absorbing material 40 Bundled fiber with ultrasonic sensitive section 40a, 40b, ... Fiber 41a, 41b, ... Optical fiber 42a, 42b, ... Collimating lens 44a, 44b, ... Coating material 50 Backing part 51 Optical transmission unit 52 Cover 60 Ultrasonic detector 71 Drive signal generation circuit 72 oscillator 73 Ultrasonic transmitter 74 Ultrasonic transmission line 75 Detection signal processing circuit 76 Ultrasonic transmitter / receiver 80 Timing control section 81 Signal processing unit 82 A / D converter 83 Primary storage 84 Image processing unit 85 Image display section 86 secondary storage 91,92 Optical amplifier 93 ASE light source 95 Narrow band filter 98 Bragg grating part 99 laser oscillator 101 base material 102 Ultrasonic sensitive area 103 Total reflection mirror 104 half mirror 105 cavity

Continued front page    F-term (reference) 2G047 BA03 CA01 CA04 CA07 DB02                       DB12 EA14 GA02 GA03 GB02                       GB17 GB33 GD00 GF25                 4C301 AA03 BB22 EE15 GA02 GA03                       GB10 GB20 GB34 GB40 JA03                       LL20                 4C601 BB05 BB06 EE12 GA01 GA02                       GA03 GB01 GB02 GB03 GB06                       GB20 GB42 GB50 GD01 GD02                       GD03 LL40

Claims (5)

[Claims] 1. An ultrasonic wave detection unit that modulates light based on an applied ultrasonic wave, an optical transmission line that guides light to the ultrasonic wave detection unit, a drive signal generation circuit that generates a drive signal, and the drive. A transducer that generates an ultrasonic wave according to a drive signal generated by the signal generation circuit, a first end, and a second end. The ultrasonic wave generated by the vibrator is transmitted from the first end to the second end. And an ultrasonic transmission path that transmits ultrasonic waves from the second end while propagating to the end of the ultrasonic imaging device. 2. The ultrasonic transmission path propagates the ultrasonic wave applied to the second end to the first end, and the transducer receives the ultrasonic wave propagated by the ultrasonic transmission path. The ultrasonic imaging apparatus according to claim 1, wherein the ultrasonic imaging apparatus generates a detection signal. 3. The ultrasonic imaging apparatus according to claim 1, wherein the ultrasonic transmission path is integrated with the ultrasonic detection unit to form a probe. 4. The ultrasonic imaging apparatus according to claim 1, further comprising a collimating unit that collimates the light guided by the optical transmission path with respect to the ultrasonic detecting unit. 5. The optical transmission line or the collimator section,
The ultrasonic imaging apparatus according to any one of claims 1 to 4, further comprising a member that has optical transparency and attenuates ultrasonic waves.