JP2002336244A - Ultrasonic receiver and ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a change of ultrasonic reception sensitivity caused by a temperature change and to miniaturize an ultrasonic receiver, in the receiver using an optical detection method. SOLUTION: This ultrasonic receiver has a plurality of fiber Bragg gratings 52(1) , 52(2) ,..., 52( N) extracting a plurality of prescribed light beams having different wavelengths from light generated from an ASE light source 40; light guides 31(1) , 31(2) ,..., 31( N) having tip parts respectively formed with a plurality of Bragg grating parts 35(1) , 35(2) ,..., 35( N) respectively having optical reflection wavelength characteristics different from each other and modulating and reflecting incident light when receiving an ultrasonic wave, and terminal parts connected to a single optical fiber 71; and a plurality of Bragg grating parts 84(1) , 84(2) ,..., 84( N) operating as optical reflection elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ultrasonic receiving apparatus for receiving an ultrasonic wave. Further, the present invention relates to an ultrasonic diagnostic apparatus used for performing medical diagnosis by receiving ultrasonic waves propagated in a subject using such an ultrasonic receiving apparatus.

[0002]

2. Description of the Related Art Conventionally, when acquiring a three-dimensional image using ultrasonic waves, a one-dimensional sensor array with a position sensor is scanned to acquire a two-dimensional image relating to a cross section in the depth direction. Thus, a three-dimensional image is realized by synthesizing a plurality of two-dimensional images acquired.

However, according to this method, 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 synthesized,
The composite image is blurred. Therefore, it is not suitable for imaging a moving subject such as a living body.

In order to obtain a three-dimensional image in real time, it is desired to develop a two-dimensional sensor array capable of obtaining a two-dimensional image without scanning the sensor array.

In an ultrasonic diagnostic apparatus, an element (vibrator or probe) for transmitting and receiving ultrasonic waves includes piezoelectric ceramics represented by PZT (lead zirconate titanate),
In general, a piezoelectric element such as PVDF (polymer piezoelectric element) is used, and a method of manufacturing a two-dimensional array using these elements is being studied. However, when the above-mentioned PZT or PVDF is used, fine processing of the element and wiring to a large number of fine elements are required, and it is difficult to achieve further miniaturization and element integration. Even if these problems are solved, there are problems such as an increase in crosstalk between elements, an increase in electrical impedance due to fine wiring, deteriorating the SN ratio, and easily breaking the electrode portion of the fine element. Therefore, it is difficult to realize a two-dimensional sensor array using PZT or PVDF.

Also, by using an ultrasonic detecting element that modulates and reflects incident light based on the received ultrasonic wave,
It is also conceivable to receive an ultrasonic wave (hereinafter, referred to as a “light detection method”). However, among such ultrasonic detecting elements, there are those such as Bragg gratings whose reflection wavelength characteristics change with a change in temperature. For this reason, in the ultrasonic receiving apparatus using the light detection method, a change in the ultrasonic receiving sensitivity due to a temperature change is a serious problem in practical use. It is also desired to reduce the size of the device.

[0007]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an ultrasonic receiving apparatus using a photodetection system, in which a change in the ultrasonic receiving sensitivity due to a temperature change is reduced and the apparatus is miniaturized. The purpose is to achieve the conversion. A further object of the present invention is to provide an ultrasonic diagnostic apparatus for performing medical diagnosis by detecting ultrasonic waves propagated in a subject using such an ultrasonic receiving apparatus.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, an ultrasonic receiving apparatus according to the present invention comprises a light source for generating light having a continuous spectrum and a predetermined light from light generated from the light source. A first plurality of optical filter elements for selectively extracting a plurality of lights having wavelengths, a multiplexer for multiplexing the plurality of lights extracted by the first plurality of optical filter elements, and a multiplexer The combined light is incident from the first end, the incident light is split and supplied to the plurality of second ends, and the reflected light reflected from the plurality of second ends is multiplexed. The optical waveguide is formed at each of a plurality of second ends of the optical waveguide such that light reflection wavelength characteristics of the optical waveguide are different from each other, and modulates incident light by receiving ultrasonic waves. A plurality of ultrasonic detecting elements each having an ultrasonic sensitive portion that reflects A second plurality of optical filter elements for selectively extracting the light emitted from the second plurality of optical filter elements in accordance with a wavelength, and a plurality of second light filter elements detecting light emitted from the second plurality of optical filter elements and outputting a plurality of detection signals. A photodetector.

[0009] An ultrasonic diagnostic apparatus according to the present invention includes the above-described ultrasonic receiving apparatus, and an image processing and display unit that performs image processing on an output signal of the ultrasonic receiving apparatus and displays the processed signal.

According to the present invention, a plurality of lights having a predetermined wavelength extracted by the first plurality of optical filter elements are multiplexed and sent to the optical waveguide, and a plurality of lights having different reflection wavelength characteristics formed on the optical waveguide are formed. The ultrasonic wave is received by the ultrasonic wave detecting element. The light modulated by the received ultrasonic wave is multiplexed again, returned to the second plurality of optical filter elements, and detected. As a result, the size of the device can be reduced,
Further, the first optical filter element, the ultrasonic detection element and the second
If the temperature dependence of the optical characteristics of the optical filter element is uniform, it is possible to reduce the change in the ultrasonic reception sensitivity due to the temperature change. Therefore, a complicated operation such as accurately adjusting the reflection wavelength characteristics of the plurality of ultrasonic detection elements is not required, and a system resistant to temperature change can be realized.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The same components are denoted by the same reference numerals, and description thereof will be omitted. FIG. 1 is a diagram showing an ultrasonic receiving apparatus according to one embodiment of the present invention.
As shown in FIG. 1, the ultrasonic receiving apparatus 10 includes a one-dimensional receiving array unit 30 that receives ultrasonic waves propagated in a subject,
An optical transmission / reception unit 20 for transmitting / receiving light containing a plurality of wavelength components to / from the one-dimensional reception array unit 30 is provided.

The optical transmitting and receiving unit 20 is configured as shown in FIG.
L having a simple continuous spectrum _BROAS that generates
E (Amplified Spontaneous Emission: amplified nature)
Emission) light source 40. The ASE light source 40
For example, Broadband Optical Fiber Amplif
ier) can be changed to output ASE light.
And is realized by For details of the broadband optical amplifier
For example, "Broadband optical amplifier" by Haruki Ogoshi
(IEICE Vol. 82 No. 7 pp. 718-724 19
July 1999). FIG. 3 shows the ASE light source 40.
FIG. 3 is a diagram showing a configuration example, in which one end of an optical fiber 41
Has a lens 42 attached and the other end has an excitation
The Bragg grating 43 for light reflection is formed
I have. Below, the Bragg grating formed on the optical fiber
And FBG (Fiber Bragg Grating)
Abbreviate. For more information on Bragg gratings,
It will be described later. Further, on the left side of the lens 42, an excitation light source
In addition, a laser oscillator 44 is disposed. Laser oscillator
The light generated from the optical fiber 44
41, which is amplified and a part of the amplified light is ASE
The light passes through the FBG 43 as light.

Referring again to FIG. 1, the ASE light source 40 receives, via an optical fiber 45, a predetermined plurality of lights L _{BRO having} different wavelengths from among the light L _BRO generated from the ASE light source 40.
₁ (center wavelength: λ ₁ ), L ₂ (center wavelength: λ ₂ ), ..., L _N
A cut-out unit 50 for cutting out (center wavelength: λ _N ) (N is an integer of 2 or more) is connected. The cutout portion 50 transmits a plurality of optical circulators 5 that transmit light incident from the left side in the figure to the right side in the figure and reflect light incident from the right side in the figure to the lower side in the figure.
1 (1), 51 (2),..., 51 (N).
The ASE light source 40 and the optical circulator 51 (1) are connected by an optical fiber 45. Further, two adjacent optical circulators 51 (1) and 51 (2)
Are connected by an optical fiber 53 (1) formed in the middle. Hereinafter, two adjacent optical circulators are connected by an optical fiber having an FBG formed in an intermediate portion.

Here, the Bragg grating will be described. A Bragg grating is formed by alternately stacking several thousands of material layers (light propagation media) having different refractive indices so that the refractive index periodically changes at a pitch (interval) satisfying the Bragg reflection condition. Things. Assuming that m is an arbitrary natural number, d is the pitch of the periodic structure of each layer, λ is the wavelength of incident light, and θ is the glancing angle (the complementary angle of the incident angle), the Bragg reflection condition is given by the following equation (1). expressed. 2d sin θ = mλ (1) In particular, when the glancing angle is 90 °, the equation (1) is further rewritten into the following equation (2). 2d = mλ (2) The Bragg grating selectively reflects only light having a wavelength (Bragg wavelength) satisfying the condition of Expression (2) and transmits light having a wavelength other than the Bragg wavelength by the action of Bragg reflection. .

In this embodiment, FIG.
As described above, the FBG 52 (1) has the wavelength λ. ₁Extremely centered on
FBG to reflect light contained in a narrow wavelength band
The pitch of the periodic structure of each layer constituting 52 (1) is given by the formula
It is set based on (2). Remaining FBG52
The same applies to (2), 52 (3), ..., 52 (N).
is there. As a result, as shown in FIG.
Light L that has passed through the filter 51 (1) to the right in the figure._BROLight L within₁
(Wavelength: λ₁) Is only the left in the figure due to FBG52 (1).
The FBG52 (1) is reflected on the right side in the figure.
To Penetrate. Reflected from FBG 52 (1) to the left in the figure
Light L₁Is further provided by an optical circulator 51 (1).
The light is reflected downward in the figure. Hereinafter, similarly, the remaining light L
_Two, L_Three, ..., L _NBut the corresponding optical circulator 51
(2), 51 (3),..., 51 (N)
Fired. The cutout section 50 is thus provided with the ASE light source.
Light L generated from 40_BROLight L₁, L_Two,
…, L_NJust cut out.

A plurality of optical circulators 51
, 51 (N) are combined with a plurality of lights having different wavelengths through the corresponding optical fibers 54 (1), 54 (2), ..., 54 (N). Arrayed-Wavelength Grating (AWG) multiplexer 60 that oscillates
Is connected. As a result, the AWG multiplexer 60 emits a light L _{MUL obtained} by multiplexing a plurality of lights L ₁ , L ₂ ,..., L _N and multiplexing them.

Here, an arrayed waveguide grating (AWG) multiplexer will be described with reference to FIG. The AWG multiplexer includes a planar lightwave circuit (PLC: Planar Lightwave).
Generally, an arrayed waveguide grating included in a circuit is used. As shown in FIG. 4, the arrayed waveguide grating includes a plurality of input waveguides 61 (1), 61 (2),.
1 (N) is connected to the input side slab waveguide 62, and one output waveguide 63 is connected to the output side slab waveguide 64.
Are connected by a plurality of arrayed waveguides 65 (1), 65 (2),..., 65 (N) having a constant waveguide length difference.

The input-side slab waveguide 62 has a fan shape with the ends of the plurality of input waveguides 61 (1), 61 (2),... Wave path 6
Reference numeral 4 denotes a fan shape having the end of the output waveguide 63 as the center of curvature. A plurality of arrayed waveguides 65 (1), 65 (2),
, 65 (N) are arranged radially so that their optical axes pass through the centers of curvature of both the input side slab waveguide 62 and the output side slab waveguide 64. Thereby, the input side slab waveguide 62 and the output side slab waveguide 64 realize the same function as a lens.

A plurality of lights having different wavelengths (λ ₁ , λ ₂ ,..., Λ
_N ) are the corresponding input waveguides 61 (1), 61 (2),
, 61 (N) and a plurality of arrayed waveguides 65 (1), 65 (2),... In the input side slab waveguide 62.
65 (N) are excited in the same phase. Each excitation light is
Corresponding array waveguides 65 (1), 65 (2), ..., 6
When passing through 5 (N), a phase difference corresponding to the waveguide length difference is given, and reaches the output side slab waveguide 64. The plurality of lights incident on the output side slab waveguide 64 are condensed and combined on the output waveguide 63 by a lens action.

Referring again to FIG. 1, AWG multiplexer 60
Is connected via an optical fiber 66 to an optical circulator 70 that switches the traveling direction of light according to the incident direction. Note that a half mirror may be used instead of the optical circulator. Further, the optical circulator 70
The one-dimensional receiving array unit 30 via the optical fiber 71
And a demultiplexer 80 that demultiplexes incident light into a plurality of predetermined lights having different wavelengths via an optical fiber 72. The optical circulator 70 _converts the light L _MUL incident from the optical fiber 61 through the optical fiber 71 into one light.
The light L _MUL ′ supplied to the three-dimensional receiving array unit 30 and returned from the optical fiber 71 is passed through the optical fiber 72 to the splitter 8.
Supply 0.

The one-dimensional receiving array unit 30 is configured as shown in FIG.
As shown most clearly in (b), a plurality of inverted L-shaped optical waveguides 31 (1), 31 (2), having different waveguide lengths.
.., 31 (N). Multiple optical waveguides 31
(1), 31 (2),..., 31 (N) are formed on the silicon substrate 32 so that their cross sections are arranged in one line. The end of the optical waveguide 31 (1) is connected to an optical circulator 70 (see FIG. 1) via an optical fiber 71.
On the other hand, the end of the optical waveguide 31 (2) is connected to the optical waveguide 31 (1) via a gap 33 (1) serving as a beam splitter.
It is connected to the end of (1). Hereinafter, the ends of two adjacent optical waveguides are connected to each other via a gap that functions as a beam splitter. As a result, FIG.
As shown in (b), the light L _MUL supplied from the optical fiber 71 to the one-dimensional receiving array unit 30 is _divided into a plurality of gaps 33.
Each time the light passes through (1), 33 (2),..., 33 (N−1), it is demultiplexed.

As shown in FIG. 5 (a), the plurality of optical waveguides 31 (1), 31 (2),..., 31 (N) are protected by being covered with a cover 34 except for the respective ends. I have. FIG. 5B shows a state in which the cover 34 has been removed from the one-dimensional receiving array unit 30. The tip of each of the plurality of optical waveguides 31 (1), 31 (2),..., 31 (N) has a Bragg grating structure as an ultrasonic sensitive part, which modulates and reflects incident light when receiving ultrasonic waves. A plurality of Bragg grating portions 35 (1), 35
(2),..., 35 (N) are formed, and these function as ultrasonic detecting elements. Alternatively, a Fabry-Perot resonator structure may be used as the ultrasonic sensitive part. In the present embodiment, a plurality of Bragg grating portions 35 (1), 35 (2),.
The plurality of FBGs 52 (1), 52 included in the cutout unit 50
(2),..., 52 (N).

In this embodiment, FIG.
As shown in, configure in a predetermined wavelength band including the wavelength lambda _1, to have a reflectance slope region Bragg grating section 35 (1) changes sharply in reflectance Bragg grating portion 35 (1) The pitch of the periodic structure of each layer is set based on equation (2). Specifically, the pitch of the periodic structure of each layer constituting the Bragg grating section 35 (1) is set based on the equation (2) so as to satisfy the following two equations (3) and (4). Λ ₁ (L) <λ ₁ <Λ ₁ (H) (3) Δλ ₁ <| Λ ₁ (H) −Λ ₁ (L) | (4) where Δλ ₁ : from FBG 52 (1) Half-width of the spectrum of the reflected light Λ ₁ (L): wavelength that gives the lower limit of the reflectance in the reflectance gradient region of the Bragg grating unit 35 (1) Λ ₁ (H): reflectance in the same reflectance gradient region Is the wavelength that gives the upper limit of. Hereinafter, the remaining Bragg grating section 35
The same applies to (2), 35 (3), ..., 35 (N).

As described above, the Bragg grating section 35 (1) has a wavelength band showing a steep reflection wavelength characteristic including the wavelength λ1 as shown in FIG. As shown in the figure, the optical waveguide 31 (1)
The light L ₁ (wavelength: λ ₁ ) of the light that has entered the Bragg grating section 35 (1) from the optical waveguide is reflected toward the optical waveguide 31 (1). At this time, the Bragg grating unit 3
Since 5 (1) of the reflectance slope region receives ultrasonic waves is shifted in the direction of the wavelength axis, depending on the shift amount, the light L ₁ which the light L ₁ is different in strength '(wavelength: lambda ₁₎ to Modulated. In the same manner, a plurality of Bragg grating section 35 (2), 35 (3), ..., 35 a plurality of light L ₂ incident on the (N), L _3, ..., the light L ₂ having different L _N is strength ', L
₃ ', ..., L _N' are modulated respectively, corresponding optical waveguides 31 (2), 31 (3), ..., is reflected toward the 31 (N). A plurality of Bragg grating sections 35 (1),
35 (2),..., 35 (N) reflected light L ₁ ′,
_{L 2 ', ..., L N} ' is the corresponding gaps 33 (1), 33
(2),..., 33 (N−1) are sequentially multiplexed and supplied to the optical circulator 70 (see FIG. 1) through the optical fiber 71.

Next, referring to FIG. 6, FIG.
The manufacturing process of the one-dimensional receiving array unit shown in FIG. First, as shown in FIG. 6A, the flame deposition method (Fl
Silicon substrate 3 by ame Hydrolysis Deposition)
An SiO ₂ lower cladding layer 100 containing SiO ₂ glass fine particles as a component and a SiO ₂ —GeO ₂ core layer 101 containing SiO ₂ —GeO ₂ glass fine particles as a component are sequentially formed on 2. Further, by heating the silicon substrate 32 to melt the SiO ₂ lower cladding layer 100 and the SiO ₂ —GeO ₂ core layer 101, as shown in FIG. Core layer 10
Form 3

Next, as shown in FIG. 6C, a resist film 104 is formed on the core layer 103 corresponding to the core positions of the plurality of optical waveguides included in the one-dimensional receiving array section.
Further, by performing reactive ion etching (Reactive Ion Etching) on the core layer 103 via the resist film 104, as shown in FIG.
Is formed on the cladding layer 102.

Next, as shown in FIG. 6E, the cladding layer 102 and the plurality of cores 10 are formed by a flame deposition method.
On top of this, an SiO ₂ upper cladding layer 106 containing SiO ₂ glass fine particles as a component is formed. Furthermore, the silicon substrate 3
2 is heated to melt the SiO ₂ upper cladding layer 106, thereby making it transparent to form a cladding layer 107, as shown in FIG.

Next, as shown in FIG. 6 (g), a resist film 108 is formed on the cladding layer 107 corresponding to the clad positions of the plurality of optical waveguides included in the one-dimensional receiving array section.
Form on top. Further, by performing reactive ion etching on the cladding layer 107 through the resist film 108, as shown in FIG.
1 (1), 31 (2),... Are completed.

Next, a plurality of optical waveguides 31 (1), 31
(2) The core 105 included at the tip of FIG.
As shown in (i), Bragg grating portions 35 (1), 35 (2),... Having different reflection wavelength characteristics are formed, respectively. For details of the method of forming the Bragg grating portion, see, for example, “Fiber Grating” by Hiroo Kanamori (IEICE Vol. 82 N
o. 7 pp. 731-739 July 1999). Then, as shown in FIG. 6 (j), the plurality of Bragg grating portions 35 (1), 35
(2),... Are removed by etching, and the other portions of the plurality of optical waveguides 31 (1), 31 (2),. Then, the one-dimensional receiving array unit shown in FIG. 5 is completed.

Here, the Bragg grating portion is generally high in sensitivity and easy to make. However, in order to use the sensor as a highly sensitive sensor as in ultrasonic diagnosis, structural conditions of the Bragg grating part are required. For example, it has been confirmed that the sensitivity to ultrasonic waves incident from the axial direction is reduced in a frequency band higher than 20 kHz when a Bragg grating unit used in a normal market is used. Also,
The length of the ultrasonic sensitive part (length of the Bragg grating part) is expressed by the following formula (ultrasonic wavelength) = (sound speed in the Bragg grating part) / (ultrasonic frequency) If the sound wave wavelength is larger than approximately ／, the detected waveform is distorted to the lower frequency side as compared with the waveform of the actually received ultrasonic wave, and the sensitivity of the sensor is lowered. This is because when the length of the Bragg grating part is larger than half the ultrasonic wavelength in the Bragg grating part, a part where the phase of expansion and contraction is inverted in the Bragg grating part in the process of transmitting the ultrasonic wave through the Bragg grating part occurs Therefore, it is considered that the displacement of these portions is offset.

In order to avoid such a phenomenon, the length of the Bragg grating portion should be approximately 概略 or less, preferably about half, of the ultrasonic wavelength in the Bragg grating portion. For example, when the frequency of the ultrasonic wave to be detected is 3.5 MHz and the sound speed in the material of the Bragg grating portion is 5500 m / s, the wavelength λ _S of the ultrasonic wave propagating through the Bragg grating portion is calculated as follows. Is done. λ _S = 5500 / (3.5 × 10 ⁶ ) = 1571.4 (μm) Accordingly, the upper limit of the length of the Bragg grating portion is calculated as follows. 1571 × (3/4) = 1178.5 (μm) From this, the length of the Bragg grating portion is set to 117
When the thickness is 8.5 μm or less, the influence of the reversal of the expansion / contraction phase in the Bragg grating portion can be suppressed, and the sensitivity required for ultrasonic detection can be obtained.

For the same reason, when a Fabry-Perot resonator or the like is used as the ultrasonic sensitive part,
It is desirable that the length of the ultrasonic sensitive part be approximately ／ or less of the wavelength of the ultrasonic wave propagating through the ultrasonic sensitive part.

Referring again to FIG. 1, the duplexer 80 includes a Bragg grating 84 having a different periodic structure pitch.
(1), 84 (2),..., 84 (N), and light L ₁ ′ reflected from the respective Bragg gratings,
_{L 2 ', ···, L N} ' light detection section 91 (1), 91
(2),..., And 91 (N), respectively, and optical circulators 81 (1), 81 (2),. As a result, the splitter 8 can be
The light L _MUL 'supplied to 0 is light L ₁ ', L ₂ ',.
, L _N '. In the present embodiment, a plurality of Bragg grating portions 84 (1), 84 (2),
, 84 (N) are a plurality of Bragg grating sections 35 (1), 35 included in the one-dimensional receiving array section 30.
(2),..., 35 (N).

Further, in the present embodiment, FIG.
As shown in (1), the Bragg grating unit 84 (1) as an optical filter element sets a flat reflectance region where the reflectance is substantially constant in the wavelength band where the corresponding Bragg grating unit 35 (1) performs the ultrasonic detection operation. The pitch of the periodic structure of each layer constituting the Bragg grating portion 84 (1) is set based on the equation (2) so as to have. In detail, the pitch of the periodic structure of each layer constituting the Bragg grating portion 84 (1) is set based on the expression (2) so as to satisfy the following two expressions (5) and (6). Γ ₁ (L) <λ ₁ <Γ ₁ (H) (5) ΔΓ ₁ ≦ | Λ ₁ (H) −Λ ₁ (L) | (6) where Γ ₁ (L): Bragg grating section The lower limit wavelength of the wavelength band providing the flat reflectance region of 84 (1) 領域₁ (H): the upper limit wavelength of the wavelength band providing the same flat reflectance region ΔΓ ₁ : the width of the same reflectance gradient region. Hereinafter, the remaining Bragg grating section 84
The same applies to (2), 84 (3),..., 84 (N).

As described above, since the Bragg grating 84 (1) has a wavelength band showing a substantially flat reflection wavelength characteristic including the wavelength λ1 as shown in FIG. 2D, as shown in FIG. As described above, the light L ₁ ′ (wavelength:
Only λ ₁ ) reflects the Bragg grating 84 (1). Hereinafter, similarly, the remaining light L ₂ ′, L ₃ ′,.
.., L _N ′ is the corresponding Bragg grating section 8
4 (2), 84 (3),..., 84 (N). Plural Bragg gratings 84 (1), 8
4 (2),..., 84 (N), reflected light L ₁ ′,
_{L 2 ', ···, L N} ' is, the optical circulator 81
(1), 81 (2),..., 81 (N).

The light detecting section 90 includes a plurality of Bragg grating sections 84 (1), 84 included in the duplexer 80.
(2),..., 84 (N) reflected light L ₁ ′, L ₂ ′,
, A plurality of photodetectors (photodiodes: PD) 91 (1), 9 which respectively receive L _N 'and output detection signals.
1 (2),..., 91 (N). Multiple PD9
1 (1), 91 (2),..., 91 (N) are the corresponding Bragg grating portions 84 (1), 84 (2),.
84 (N) light L ₁ reflected by the ', L _2', ..., are arranged in a row so as to receive separately L _N '. It should be noted that, as the light detection unit, a CCD (Charge C
Oupled Device) may be used. When the plurality of Bragg grating units 35 (1), 35 (2),..., 35 (N) included in the one-dimensional receiving array unit 30 receive ultrasonic waves, the plurality of Bragg grating units 84
The reflected light amounts of (1), 84 (2),..., 84 (N) change accordingly. Thereby, a plurality of PD91 (1),
, 91 (N) change.

[0037] Thus, according to this embodiment, a plurality of light L _1, L ₂ of different wavelengths, ..., the light L is multiplexed L _{N
The MUL transmits} a plurality of optical waveguides 31 through an optical fiber 71.
(1), 31 (2),..., 31 (N), and a plurality of Bragg grating portions 35 (1), 35 (N).
(2),..., 35 (N). A plurality of Bragg grating sections 35 (1), 35 (2), ..., 35
(N), upon receiving the ultrasonic wave propagated through the subject, modulates and reflects only light having a predetermined wavelength from the incident light, and transmits the rest. Further, the light reflected from the plurality of Bragg grating portions 35 (1), 35 (2),..., 35 (N) is reflected by the corresponding optical waveguides 31 (1), 31 (2),
.., 31 (N) are multiplexed with the optical fiber 71. In this way, the input and output lights of the one-dimensional receiving array unit 30 are multiplexed. Accordingly, it is possible to reduce the number of optical fibers for transmitting such input / output light, thereby increasing the number of Bragg grating units used as ultrasonic detecting elements while suppressing an increase in the size of the device. Improvement can be achieved.

According to this embodiment, a plurality of FBGs 52 (1), 52 (2),.
2 (N) and a plurality of Bragg grating sections 35 (1), 35 (2) included in the one-dimensional receiving array section 30,
, 35 (N) and a plurality of Bragg grating sections 84 (1), 84 (2), ..., 84 included in the duplexer 80.
(N) are made of the same material. They are,
Usually, they are used at the same temperature environment, so that they have almost the same temperature. Therefore, even if the temperature changes, the FBG 52
(1) Reflection wavelength and Bragg grating section 35
(1) Reflection wavelength and Bragg grating section 84
The reflection wavelength of (1) shifts similarly. The same applies to other sets of Bragg grating sections. This makes it possible to realize an ultrasonic receiver that is resistant to temperature changes without performing complicated operations such as accurately adjusting the reflection wavelength characteristics of the Bragg grating section.

Further, a plurality of FBs included in the cutout 50
It is desirable to achieve thermal coupling between G, a plurality of Bragg grating units included in the one-dimensional reception array unit 30, and a plurality of Bragg grating units included in the duplexer 80. The thermal coupling is performed, for example, by connecting the cutout unit 50, the one-dimensional reception array unit 30, and the duplexer 80 with a material having a high thermal conductivity, or by connecting the cutout unit 50, the one-dimensional reception array unit 30, and the branching device. This is realized by bringing the device 80 into physical proximity. Alternatively, the extracting unit 50, the one-dimensional receiving array unit 30, and the duplexer 80
The thermal coupling can also be realized by arranging a heat pipe around the heat pipe. When using a heat pipe,
A fluid that conducts heat by convection is enclosed in a heat pipe.

By combining a plurality of the one-dimensional receiving array units 30 and the optical transmitting / receiving units 20 configured as described above, a small two-dimensional sensor array can be realized.

Next, an ultrasonic diagnostic apparatus according to one embodiment of the present invention will be described. FIG. 7 is a block diagram illustrating a configuration of the ultrasonic diagnostic apparatus according to the present embodiment. As shown in FIG. 7, the ultrasonic diagnostic apparatus includes an ultrasonic probe 110 used in contact with a subject. The ultrasonic probe 110 includes a plurality of one-dimensional receiving array units 30 and a plurality of piezoelectric elements 121 (1), 1
21 (2),..., 121 (N) arranged in one row
Dimensional transmission array section 120. In the ultrasonic probe 110, a two-dimensional sensor array is realized by alternately arranging a plurality of one-dimensional receiving array units 30 and a plurality of one-dimensional transmitting array units 120.

Further, the ultrasonic diagnostic apparatus includes a plurality of drive signal generating circuits 140 for generating drive signals under the control of the timing control section 130. A plurality of one-dimensional transmission array units 12 included in the ultrasonic probe 110
0 indicates a plurality of piezoelectric elements 121 (1), 121 based on the drive signal generated from the corresponding drive signal generation circuit 140.
(2),..., 121 (N) generate ultrasonic waves and transmit these ultrasonic waves to the subject. The plurality of ultrasonic waves reflected from the subject are received by the one-dimensional receiving array units 30 included in the ultrasonic probe 110.

The plurality of one-dimensional receiving array units 30 included in the ultrasonic probe 110 are connected to the plurality of optical transmitting / receiving units 20, respectively. The plurality of detection signals output from the photodetector 90 (see FIG. 1) included in the plurality of optical transmission / reception units 20 are output to the signal processing unit 151 included in the signal processing unit 150.
Is input to The signal processing unit 151 includes a plurality of drive signal generation circuits 1 under the control of the timing control unit 130.
After a lapse of a predetermined time from the generation of the drive signal by the 40, a plurality of detection signals output from the plurality of optical transmission / reception units 20 are fetched. Based on these detection signals, the signal processing unit 151 includes a plurality of Bragg grating units 35 (1), 35 (2) included in the plurality of one-dimensional reception array units 30,
.., 35 (N) obtains the sound pressure information of the ultrasonic waves received.

The output signal of the signal processing section 151 is A
The signal is converted into a digital signal in the / D converter 152.
The primary storage unit 160 is connected to the A / D converter 152, and stores the acquired plurality of two-dimensional data (data relating to a plurality of tomographic planes). Then, based on these data, the image processing unit 170 reconstructs two-dimensional data or three-dimensional data. The reconstructed data is interpolated,
The image is subjected to processes such as a response modulation process and a gradation process and displayed on the image display unit 180. Further, the data processed by the image processing unit 170 is stored in the secondary storage unit 190.

FIG. 8A is a perspective view showing an example of the configuration of an ultrasonic probe included in the ultrasonic diagnostic apparatus shown in FIG. 7, and FIG. It is a diagram showing an example of the arrangement of the piezoelectric element and the Bragg grating portion,
FIG. 8C is a diagram showing another arrangement example. FIG. 8 (a)
As shown in FIG. 1, in the ultrasonic probe 110, the plurality of one-dimensional reception array units 30 and the plurality of one-dimensional transmission array units 1
20 are alternately arranged. In addition, a plurality of 1
A probe for transmitting ultrasonic waves may be configured using the one-dimensional transmission array unit, and a probe for receiving ultrasonic waves may be configured using a plurality of one-dimensional reception array units. The plurality of one-dimensional transmission array units 120 include the plurality of piezoelectric elements 1 arranged in one row.
21 (1), 121 (2),..., 121 (N). A plurality of piezoelectric elements 121 (1), 121 (2),
..., 121 (N) is PZT (lead zirconate titanate)
Ultrasonic waves are generated based on a drive signal supplied from a corresponding drive signal generation circuit 140 (see FIG. 1), using a ceramic piezoelectric material such as, or a polymer piezoelectric material such as PVDF (polyvinylidene fluoride).

In the present embodiment, as shown in FIG. 8A, a plurality of one-dimensional receiving array units 30 and a plurality of one-dimensional transmitting array units 120 are arranged at a right angle to the ultrasonic transmission direction. Are alternately arranged in one direction. Therefore, when the ultrasonic probe 110 is viewed from the transmitting / receiving side of the ultrasonic wave, as shown in FIG. 8B, a plurality of Bragg grating portions (white squares) and a plurality of piezoelectric elements (black squares) A two-dimensional sensor array for transmitting and receiving ultrasonic waves is formed. Note that, as shown in FIG. 8C, the number of piezoelectric elements may be smaller than the number of Bragg grating sections, and a plurality of piezoelectric elements may be arranged on a cloth.

[0047]

As described above, according to the present invention,
In addition to suppressing an increase in the size of the apparatus, a complicated adjustment due to a temperature change is not required, and a system resistant to a temperature change can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an ultrasonic receiving apparatus according to an embodiment of the present invention.

FIGS. 2A to 2D are diagrams for explaining setting conditions of each optical element used in the ultrasonic receiving apparatus shown in FIG.

FIG. 3 is a diagram illustrating a configuration example of an ASE light source included in the ultrasonic receiving device illustrated in FIG. 1;

FIG. 4 is a diagram illustrating a configuration example of an AWG multiplexer included in the ultrasonic receiving device illustrated in FIG. 1;

FIG. 5A is a perspective view illustrating a configuration example of a one-dimensional receiving array unit included in the ultrasonic receiving device illustrated in FIG. 1,
(B) is a plan view showing a state in which a cover has been removed from the one-dimensional reception array unit.

FIGS. 6A to 6J are diagrams illustrating an example of a manufacturing process of the one-dimensional receiving array unit illustrated in FIGS. 1 and 5;

FIG. 7 is a block diagram illustrating a configuration example of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

FIG. 8A is a perspective view showing a configuration example of an ultrasonic probe included in the ultrasonic diagnostic apparatus shown in FIG. 7, and FIG.
FIG. 3C is a diagram showing an example of the arrangement of a piezoelectric element and a Bragg grating used in the ultrasonic probe, and FIG.
FIG. 9 is a diagram showing another arrangement example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Ultrasonic receiver 20 Optical transmission / reception part 30 One-dimensional reception array part 31 (1), 31 (2), ..., 31 (N) Optical waveguide 35 (1), 35 (2), ..., 35 (N) Bragg Grating section 40 ASE light source 41 Optical fiber 42 Lens 43 Bragg grating section (FBG) 50 Cutout section 52 (1), 52 (2), ..., 52 (N) Bragg grating section (FBG) 60 AWG multiplexer 70 Light Circulator 80 demultiplexer 81 (1), 81 (2), ..., 81 (N) Optical circulator 84 (1), 84 (2), ..., 84 (N) Bragg grating unit 90 photodetector 91 (1) , 91 (2),..., 91 (N) Photodetection unit (photodiode) 110 Ultrasonic probe 120 One-dimensional transmission array unit 121 (1), 121 (2),. (N) Piezoelectric element 150 Signal processing means 170 Image processing unit 180 Image display unit

Claims (15)

[Claims] A light source for generating light having a continuous spectrum; a first plurality of optical filter elements for selectively extracting a plurality of lights having a predetermined wavelength from the light generated from the light source; A multiplexer that multiplexes a plurality of lights extracted by the first plurality of optical filter elements; and a light that is combined by the multiplexer is input from a first end to generate a plurality of incident lights. An optical waveguide that splits and supplies the light to the second end of the optical waveguide, multiplexes the reflected lights reflected from the plurality of second ends, and emits the light from the first end; A plurality of ultrasonic detecting elements respectively formed at a plurality of second ends of the optical waveguide so as to be different from each other, and each having an ultrasonic sensitive portion which modulates and reflects incident light by receiving ultrasonic waves. And selectively extracting light emitted from the optical waveguide according to a wavelength. 2 of a plurality of optical filter elements, said second plurality of plurality of ultrasonic receiving apparatus comprising a light detector, the outputs of the plurality of detection signals by detecting the light emitted from the light filter element. 2. The ultrasonic receiving apparatus according to claim 1, wherein said ultrasonic sensitive section includes a Bragg grating structure or a Fabry-Perot resonator structure. 3. The ultrasonic wave according to claim 1, wherein the length of the ultrasonic sensitive part has a length of 以下 or less of the wavelength of the ultrasonic wave propagating through the ultrasonic sensitive part. Probe. 4. The first plurality of optical filter elements, the plurality of ultrasonic detection elements, and the second plurality of optical filter elements are made of a material having substantially the same temperature dependence of optical characteristics. The ultrasonic receiving apparatus according to any one of claims 1 to 3, wherein the ultrasonic receiving apparatus includes: 5. When the wavelength of light extracted by each of the first plurality of optical filter elements and the half-value width of its spectrum are λ and Δλ, respectively, the ultrasonic detecting element corresponding to each optical filter element is The lower limit wavelength Λ (L) and the upper limit wavelength Λ (H) in the reflectance gradient region have the following relationship: Λ (L) <λ <Λ (H) Δλ <| Λ (H) −Λ (L) | And the lower limit wavelength Γ (L) and the upper limit wavelength Γ (H) in the transmittance or reflectance flat region of the second optical filter element corresponding to each ultrasonic detection element, and the transmittance or reflection. The width ΔΓ of the rate flat region is set so as to satisfy the following condition: Γ (L) <λ <Γ (H) ΔΓ ≦ | Λ (H) −Λ (L) | 2. The ultrasonic receiving apparatus according to claim 1. 6. The first plurality of optical filter elements, the plurality of ultrasonic detection elements, and the second plurality of optical filter elements are thermally coupled. The ultrasonic receiver according to any one of claims 1 to 7. 7. The ultrasonic receiving apparatus according to claim 1, wherein the light source includes an ASE (amplified spontaneous emission) light source. 8. The ultrasonic receiving apparatus according to claim 1, wherein said multiplexer includes an AWG (arrayed waveguide grating) multiplexer. 9. The ultrasonic receiver according to claim 1, wherein each of the second plurality of optical filter elements has a Bragg grating structure or an AWG (arrayed waveguide grating) demultiplexing structure. apparatus. 10. A switching unit that supplies light combined by the multiplexer to the optical waveguide and emits light returned from the optical waveguide in a direction different from that of the multiplexer. The ultrasonic receiving apparatus according to any one of claims 1 to 9, further comprising: a duplexer that supplies light emitted from the unit to the second plurality of optical filter elements. 11. The ultrasonic receiving apparatus according to claim 10, wherein said switching unit includes an optical circulator or a half mirror. 12. The photodiode array or the photodiode array, wherein the light detection unit is configured by a plurality of photodiodes.
The ultrasonic receiving apparatus according to any one of claims 1 to 11, further comprising D (charge-coupled device). 13. The apparatus according to claim 1, further comprising a plurality of optical waveguides, wherein said plurality of ultrasonic detecting elements are two-dimensionally arranged.
The ultrasonic receiving apparatus according to any one of claims 12 to 12. 14. An ultrasonic diagnostic apparatus comprising: the ultrasonic receiving apparatus according to claim 1; and an image processing display unit that performs image processing and displays an output signal of the ultrasonic receiving apparatus. apparatus. 15. The ultrasonic diagnostic apparatus according to claim 14, further comprising an ultrasonic transmission unit that transmits an ultrasonic wave to the subject.