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JPS6236557

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DESCRIPTION JPS6236557
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
optical hydrophone capable of detecting two-dimensional image information represented by
ultrasonic waves with high sensitivity and correcting the information disturbed in water at high
speed. . The present invention is used as an ultrasonic sensor used in water. [Summary] The
present invention relates to an optical hydrophone for measuring information represented by
ultrasonic waves using an optical interferometer, comprising a plurality of such optical
interferometers, and a portion to be observed of each optical interferometer is an ultrasonic
wave. By arranging in an array in parallel to the wave arrival surface, and providing a shielding
plate having an elongated observation window crossing the array direction on the wave arrival
surface of the ultrasonic wave of the observation portion, the observation window is in the
longitudinal direction By taking out the light output of the optical interferometer and performing
correction processing for underwater disturbance in the light region, the two-dimensional image
information represented by the ultrasonic wave is detected with high sensitivity, And, it is
possible to correct the information which has been disturbed in water at high speed. [Prior Art]
FIG. 3 is a block diagram showing a conventional photohydrophone. In FIG. 3, the output light of
the single frequency semiconductor laser 101 is incident on the first optical directional coupler
103 through the optical input terminal 102, branched into two, and propagates to the optical
fiber waveguides 104 and 105, respectively. Do. The ultrasonic sensing unit 10 is inserted into
the optical fiber waveguide 105, and the fiber coil type optical phase shifter 106 is inserted into
the optical fiber waveguide 104. The optical fiber waveguides 104 and 105 are connected to the
optical output terminals 108 and 109 via the second optical directional coupler 107,
respectively. Light receiving elements 112 and 113 are disposed at the light output terminals
108 and 109, respectively, and a signal detection circuit 114 is connected to the light receiving
elements 112 and 113. The optical phase shifter control output line 115 of the signal detection
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circuit 114 is connected to the fiber coil type optical phase shifter 106, and the detection signal
output 120 is connected to the optical hydrophone signal processing unit 200. A Mannha
Zehnder interferometer is constituted by the optical directional couplers 103 and 107, the
optical fiber waveguides 104 and 105, the ultrasonic sensing unit 10, and the fiber coil type
optical phase shifter 106. The optical hydrophone sensor unit 100 is configured of the single
frequency semiconductor laser 101 through the optical phase thick control output cotton 115,
and the optical hydrophone signal processing circuit 20 is configured of the optical hydrophone
sensor unit 100 and the optical hydrophone signal processing unit 200. Be done.
Ultrasonic wave information is obtained from the light hydrophone signal processing unit 200 to
the ultrasonic image information signal line 30 as an output of the light hydrophone signal
processing unit i20. The ultrasonic sensing unit 10 is a part that detects the pressure of the
ultrasonic wave to be measured, and the phase of the optical signal propagating through the
optical fiber waveguide 105 is the pressure of the ultrasonic wave applied to it when passing
through the ultrasonic sensing unit 10 It changes according to. The optical signal of the optical
fiber waveguide 105 phase-modulated by ultrasonic waves interferes with the reference light of
the optical fiber waveguide 104 at the optical directional coupler 107. The optical signals
obtained by the light receiving elements 112 and 113 include an intensity fluctuation
corresponding to the amount of phase fluctuation received by the ultrasonic sensing unit 10.
Therefore, this phase fluctuation can be detected in the signal detection circuit 114, and the
intensity of the ultrasonic wave applied to the ultrasonic sensing unit 10 can be measured. The
detection signal output 120 is processed by the optical hydrophone signal processing unit 200 to
obtain ultrasound information. The fiber coil type optical phase shifter 106 is obtained by
winding an optical fiber (optical fiber waveguide 104) around a cylindrical piezoelectric element,
and the refractive index of the optical fiber is photoelastic according to the applied voltage
(optical phase shifter control output line 115). The optical length (propagation phase difference)
changes due to the effect. This changes the optical length of the optical fiber waveguide 104 by
the fiber coil type optical phase thick 106 because the state of the optical fiber waveguide
104.105 changes with respect to thermal or mechanical disturbance, and the optical fiber
waveguide 105 And the phase delay difference between the FIG. 4 is a diagram showing output
characteristics of the light output terminals 108 and 109. The bias voltage of the fiber coil type
optical phase thick 106 is adjusted to an optimal value by the optical phase thick control output
line 115 so that the output of the optical output terminal 108 and the output of the optical
output terminal 109 can be made close by the signal detection circuit 114. [Problems to be
Solved by the Invention] However, in the ultrasonic sensor using such a conventional
photohydrophone, when converted to the pressure of vibration of water excited by the ultrasonic
wave, it is about 10 "" dyn / cm Z You can only get an angry degree. Moreover, in the
conventional configuration, only information of a specific point can be obtained, and it is difficult
to obtain dimensional or two-dimensional information. Furthermore, the implementation of the
correction due to the disturbance in water requires a huge amount of processing, which causes
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problems such as an increase in the information processing apparatus and time. The present
invention solves such conventional problems, detects image information represented by
ultrasound as one-dimensional or two-dimensional ultrasound image information with high
sensitivity, and corrects the information at high speed It aims to provide a light hydrophone that
can.
[Means for Solving the Problems] The first invention of the present invention is provided with a
plurality of optical interferometers, and the portion to be observed (ultrasonic sensing portion) of
each of the optical interferometers is directed to the wave arrival surface of ultrasonic waves
They are arranged in an array in parallel to obtain one-dimensional ultrasound image
information. According to the second aspect of the present invention, a shield plate having an
elongated observation window crossing the array direction is provided on the wave arrival
surface of the ultrasonic wave of the observed portion (ultrasonic sensing portion), and the
observation window is moved in the longitudinal direction And means for obtaining twodimensional ultrasound image information. A third invention of the present invention is
characterized in that the optical hydrophone signal processing circuit is provided with a
correction means for correcting in the light area the disturbance to which the sound wave is
received by propagation in water. That is, according to the first invention of the present
invention, a light source, means for branching the output light of this light source into two
optical paths, optical path length variable means disposed in each of the two optical paths, and
pressure of incoming ultrasonic waves The optical interferometer includes an observed portion
for changing the phase of the output light, and a means for comparing and observing the optical
signal passing through the optical path length changing means and the observed portion, and
calculating an output signal of the optical interferometer An optical hydrophone provided with a
signal processing unit for obtaining ultrasonic information by processing the optical
interferometer includes several of the above optical interferometers, and the observed portions of
the respective optical interferometers are arrayed in parallel to the wave arrival surface of
ultrasonic waves. It is characterized in that it is a structure arranged in a shape. According to a
second aspect of the present invention, there is provided an optical hydrophone having a similar
optical interferometer and a signal processing unit, wherein the optical interferometer comprises
several of the above optical interferometers, and the portion to be observed of each optical
interferometer has a wave arrival surface of ultrasonic waves. And a shield plate having an
elongated observation window which crosses the array direction on the wave arrival surface of
the ultrasonic wave of the observation portion. Preferably, the observation window is movable
substantially perpendicular to the longitudinal direction of the observation window. A third
invention of the present invention is an optical hydrophone having the same optical interference
needle and signal processing section, comprising several of the above optical interferometers,
and the observed portion of each optical interferometer has an ultrasonic wave arrival surface A
shield plate is arranged in parallel to the array in the form of an array, and the wave arrival
surface of the ultrasonic wave of the observation portion has a long observation window crossing
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the array direction, and the optical interferometer A light branching means for branching is
provided, and the signal processing circuit includes means for performing light intensity
modulation on the light output branched by the light branching means with an image correction
signal, and ultrasonic waves of the light signal subjected to the light intensity modulation. And
means for integrating frequency components. [Operation] According to the first aspect of the
present invention, the observed portion (ultrasonic sensing portion) that changes the phase of
the optical signal according to the pressure of the incoming ultrasonic wave, and the intensity
fluctuation of the ultrasonic wave corresponding to the phase fluctuation amount And several
optical interferometers including an optical hydrophone sensor unit for detecting the object, and
the observation units (ultrasonic sensing units) are arranged in an array in parallel to the wave
arrival surface of the ultrasonic wave, By processing the output signal of the meter, it is possible
to obtain one-dimensional ultrasound image information by ultrasound.
According to the second aspect of the present invention, a one-dimensional ultrasonic image by
ultrasonic waves is provided by providing a shielding plate having an elongated observation
window crossing the array direction on the wave incoming surface of ultrasonic waves of the
observed portion (ultrasonic sensing portion) The information can be measured with high
sensitivity, and the observation window is moved in a direction substantially perpendicular to the
longitudinal direction of the observation window, and the one-dimensional ultrasonic image
information is accumulated sequentially to sensitize the two-dimensional ultrasonic image
information. It can be easily obtained well. According to a third aspect of the present invention,
high-speed and accurate two-dimensional ultrasound image information is obtained by providing
the optical hydrophone signal processing circuit with correction means for performing correction
in the light region of the disturbance to which ultrasonic waves are propagated in water. Can.
That is, the optical hydrophone signal processing circuit takes out a part of the output light of
each optical interferometer, performs intensity modulation with the image correction signal, and
corrects by integrating the ultrasonic frequency component of the intensity-modulated optical
signal. It can be performed. Embodiments of the present invention will now be described with
reference to the drawings. FIG. 1 is a view showing a schematic configuration of an embodiment
of the first invention and the second invention of the present invention. In FIG. 1, reference
numerals 11 to 18 denote ultrasonic sensing units arranged in an array, reference numerals 21
to 28 denote photohydrophone signal processing circuits accommodating the respective
ultrasonic sensing units 11 to 18, reference numerals 31 to 18. Reference numeral 38 is an
ultrasonic image information signal line, reference numeral 40 is a one-dimensional information
memory, reference numeral 50 is a coaxial code, reference numeral 60 is a CRT display device,
and reference numeral 80 is an ultrasonic wave of ultrasonic sensing unit 11-1 day. The shield
plate 80 is provided on the incoming surface, and the shield plate 80 has an elongated scan
observation window 81 which crosses in the array direction of the ultrasonic sensing units 1118. The photohydrophone signal processing circuits 21 to 28 each include a photohydrophone
sensor unit 100 and a photohydrophone signal processing unit 200 that constitute a Matsuha-
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ENDA interferometer including a conventional ultrasonic sensing unit. The ultrasonic sensing
units 11 to 18 are portions that observe the waves of ultrasonic waves passing through the
scanning observation window 81, and the pressure of the ultrasonic waves to which the phase of
the optical signal propagating in the optical fibers of the ultrasonic sensing units 11 to 18 is
added. It changes according to. In the optical hydrophone signal processing circuits 21 to 28, the
intensity fluctuation corresponding to the phase fluctuation amount obtained by the ultrasonic
sensing units 11 to 18 is detected by the optical hydrophone sensor unit 10 (), and each optical
hydrophone signal is detected. One-dimensional ultrasound image information is obtained by
performing arithmetic processing of the intensity in the processing unit 200.
This -dimensional ultrasound image information is stored in the one-dimensional information
memory 40 via the ultrasound image information signal lines 31 to 38, and is further sent out
and displayed on the CR7 display device 60 via the coaxial code 50. The second invention of the
present invention is to obtain one-dimensional ultrasonic image information of sequentially
arranged positions by moving the position of the scanning observation window 81 in a direction
substantially perpendicular to the longitudinal direction of the scanning observation window 81.
By storing one-dimensional ultrasonic image information in the one-dimensional information
memory 40, the CR7 display 60 can be displayed as a two-dimensional ultrasonic image. Here,
the correction of the deterioration of the ultrasonic image due to the disturbance in water will be
described. In the case of ultrasonically searching for the condition in water, the disturbance in
the water generally causes distortion in the information. The image information transmitted by
the linear system is received as information represented by the equation g = (h) .f + n...-(1). r is
the original image vector (NXI), g is the received image vector (NXI), [h] is the transfer matrix of
the system (N X N) and includes the effects of disturbances in water, n is mixed into the receiver
Additive noise vector (NXI). It is necessary to estimate the original information Igf from the
information g observed on the ultrasonic sensing unit 11 to 1 day. A commonly used estimation
method is the least mean square error estimation method, and E (1 (h) · f′−g 1 2)
−−−−−−− (estimated image vector f minimizing 21) Ask for '. Here, 112 represents the
square of the magnitude of the vector ((h) · f'-g) and EC represents the mean value thereof.
Furthermore, if the additive noise n is small enough to ignore, (the original information vector f is
obtained from (11) as f = (h) 柑 g − (3). Here, [h)-'is the inverse of matrix (h). Therefore, it is
possible to obtain an estimated image by performing the operation of the equation (2) or (3) on
discrete ultrasound image information obtained by the optical hydrophone in which the
ultrasound sensing units 11 to 18 are arranged in an array. it can. FIG. 2 is a block diagram
showing an embodiment of the photohydrophone of the third invention of the present invention,
and shows the constitution of the photohydrophon which obtains an estimated image by using
the above equation (3). In this embodiment, one of the ultrasonic sensing unit 11 and the
photohydrophone sensor unit 100 in the array arrayed in parallel, and one photohydrophone for
performing optical arithmetic processing of the output of each photohydrophone sensor unit 100
An example configured by the signal processing unit 200 is shown.
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Although the case where eight ultrasonic sensing parts 11 and eight optical hydrophone sensor
parts are arranged is shown in this embodiment, they are omitted. The ultrasonic sensing unit 11
and the optical hydrophone sensor unit 100 basically have the same configuration as the
conventional optical hydrophone, but conventionally, the information detected by the optical
hydrophone sensor unit 100 is from the signal detection circuit 114 The signal is sent to the
photohydrophone signal processing unit 200 through the detection signal output line 120 and
processed. In the embodiment of the present invention, the light signal is output as it is, and the
photohydrophone signal processing unit 200 collectively performs light arithmetic processing.
But it is different. That is, the output light of the single frequency semiconductor laser 101 enters
the first optical directional coupler 103 through the optical input terminal 102, is branched into
two, and propagates to the optical fiber waveguides 104 and 105, respectively. The ultrasonic
sensing unit 11 is inserted into the optical fiber waveguide 105, and the fiber coil type optical
phase shifter 106 is inserted into the optical fiber waveguide 104. The optical fiber waveguides
104. 105 are connected to the two optical splitters 110. 111 via the second optical directional
coupler 107. One output of each of the light branching devices 110 and 111 is connected to the
light output terminals 10B and 109. Light receiving elements 112 and 113 are disposed at the
light output terminals 10B and 109, respectively, and a signal detection circuit 114 is connected
to the light receiving elements 112 and 113. The optical phase thick control output line 115 of
the signal detection circuit 114 is connected to the fiber coil type optical phase shifter 106. The
other light output 108 ′ of the light splitter 110 is connected to the first input terminal of the
light intensity modulator 201. An optical signal (optical output 108 ′) input to the first input
terminal of the optical intensity modulator 201 is denoted by xl. Elements (hIl, hI □, hl3, h15%
h16% hIT, h18) of the image correction matrix (h)-'are input to the second input terminal of the
light intensity modulator 201. The light output of the light intensity modulator 201 (hllx1%
h12xl, h + ax +, h14XI, h + s x 1% h16 x +, hIT x 1%) 118 X I is input to the integrator 221
through the light receiving element 211. And integrated. A light receiving element 231 is
disposed at the other light output 109 ′ of the light branching device 111. The output signal of
the light receiving element 231 is connected to the monitor input of the integrator 221.
Similarly, the ultrasonic wave information observed by the other ultrasonic wave sensing units
12 to 18 (not shown) also includes the first input terminals of the light intensity modulators 202
to 208 and the light receiving elements via the respective optical hydrophone sensor units 100.
It is manpowered to 212-218 and integrators 222-228.
At the second input terminals of the light intensity modulators 202 to 208, the elements (hzl, ...,
h2B-, h3 ..., h3a, h41, ...) of the image correction matrices (h) to 1 respectively , H4! l、h!
+1、”’、hs8、h61.””、hi、a、h7い・・・、hfe、h85、・・・、
hI! s) is input. Each output of the integrators 221 to 228 (ZhBx, 1, ΣhZJXt, "'2. Σha = Xa) is
sent out to the ultrasonic image information signal lines 31 to 38. The ultrasonic sensing unit 11
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is a part that observes the wave of the ultrasonic wave, and changes according to the pressure of
the ultrasonic wave to which the phase of the optical signal propagating in the optical fiber of the
ultrasonic sensing unit 11 is applied. An intensity variation corresponding to the phase variation
obtained by the ultrasonic sensing unit 11 is detected by the photohydrophone sensor unit 100,
and the photohydrophone signal processing unit 200 performs an arithmetic processing of the
intensity to achieve one-dimensional excess. Sound wave image information is obtained. This dimensional ultrasound image information is stored in the one-dimensional information memory
40 via the ultrasound image information signal lines 31 to 38, and is further sent out and
displayed on the CRT display device 60 via the coaxial code 50. In the optical hydrophone signal
processing unit 200, the light output 108 'of the optical hydrophone sensor unit 100 and the
elements of the image correction matrix Ch)-' are input to the light intensity modulators 201 to
208, and the intensity modulation is performed By integrating the ultrasonic frequency
components of the output signal, a corrected one-dimensional image component is obtained. In
addition, as shown in FIG. 1, the two-dimensional correction corrected by moving the scanning
observation window 81 and sequentially storing the corrected one-dimensional ultrasonic image
information at each position in the one-dimensional information memory 40. Ultrasonic image
information can be obtained. [Effects of the Invention] As described above, according to the
present invention, the observed portions of the optical interferometer are arranged in an array
parallel to the wave arrival surface of the ultrasonic wave, and observation of the ultrasonic wave
through the movable scanning observation window By moving the scanning observation window
in a direction substantially perpendicular to the array direction, one-dimensional or twodimensional ultrasonic image information can be easily obtained with high sensitivity.
Furthermore, by correcting the output of the optical interferometer in the light region, correction
of two-dimensional ultrasound image information can be performed at high speed. Further, the
matching property with the optical fiber transmission system and the optical integrated circuit
system is also very good, and there is an effect that a stable measurement system can be
configured.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a view showing a schematic configuration of an embodiment of the first invention and
the second invention of the present invention.
FIG. 2 is a block diagram showing an embodiment of the third invention of the present invention.
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FIG. 3 is a block diagram showing a conventional photohydrophone. FIG. 4 is a diagram showing
output characteristics of the light output terminals 108 and 109. l0111 to 18 ... ultrasonic
sensing unit, 20.21 to 28 ... photohydrophone signal processing circuit, 30.31 to 38 ... ultrasonic
image information signal line, 40 ...-dimensional information memory, 50: Coaxial code, 60: CRT
display, 80: Shielding plate, 81: Scanning observation window, 100: Photohydrophone sensor,
101: Single frequency semiconductor laser, 102: optical input terminal 103. 107: directional
optical coupler, 104. 105: optical fiber waveguide, 106: fiber coil type optical phase shifter, 108.
109: optical output Terminals 110, 111: light splitters 112. 113: light receiving elements 114:
signal detection circuits 115: light phase shifter control output lines 120: detection signal
outputs 200: ··light Idorofon signal processing unit, 201-208 ... optical intensity modulator, 211218 ... light-receiving element, 221-228 ... integrator, 231 ... light-receiving element.
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