JPH02126177

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DESCRIPTION JPH02126177
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic transducer used for a fish finder or the like, and more particularly to a transducer
using an optical fiber. [Prior Art] FIG. 4 shows a schematic configuration of a generally used fish
finder. The electrical signal of the ultrasonic wave output from the ultrasonic transmitter /
receiver 41 is converted into an ultrasonic wave by the ultrasonic transducer 43 and emitted into
water. The emitted ultrasonic waves are reflected by the object 44 in the water, and the reflected
waves are converted by the ultrasonic transducer 43 into electric signals and processed into
predetermined signals by the ultrasonic transmitter-receiver 41. Ru. In such a device, since the
weak signal received by the ultrasonic transducer 43 is transmitted through the relatively long
cable 42, electromagnetic noise is easily received during that time, and the S / N ratio is descend.
[Problems to be Solved by the Invention] FIG. 5 shows a system using an optical fiber to prevent
the reduction of the S / N ratio due to the above-mentioned cable transmission. Laser light from
the laser light source 51 (frequency [. Is modulated by the signal (frequency fb) from the
oscillator 53 in the ultrasonic light modulator 52. The transmitted light (frequency r0) from the
ultrasonic light modulator 52 enters the light receiving element 56 as an object light through an
optical fiber cable (referred to as an optical fiber sensor) 54 and an optical fiber coupler 55
wound in a coil. Ru. Then, the modulated light (frequency (r, + fb)) from the ultrasonic light
modulator 52 is directly incident on the front fiber coupler 55 via the optical fiber cable 57.
When the ultrasonic wave (frequency fs) from the ultrasonic wave transmitter 58 reflected by the
object 44 is made incident on the front fiber sensor 54, the object light is modulated in the
optical fiber sensor 54, so in the optical fiber coupler 55, The modulated object light interferes
with the reference light to obtain an interference signal of frequency (fb−rs). The interference
signal is converted into an electric signal by the light receiving element 56 and processed into a
predetermined signal by the signal processing circuit 59, and the depth information of the object
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44 is displayed on the display 60. In such a system, since the signal detected by the optical fiber
sensor 54 is incident on the light receiving element 56 as an optical signal, there is no risk of
receiving electromagnetic noise, but from this optical fiber sensor 54, an ultrasonic wave is
generated. Can not be emitted, and it is necessary to provide an ultrasonic wave transmitter 58
separately. The present invention has been made to eliminate the above-mentioned problems,
and it is an object of the present invention to provide an ultrasonic transducer capable of
transmitting and receiving ultrasonic waves with a transducer using an optical fiber sensor. .
[Means for Solving the Problems 1 The ultrasonic transducer according to the present invention
is an ultrasonic transducer for transmitting and receiving ultrasonic waves, and is a receiver on
the surface of a transducer as a transmitter. A tip fiber cable of a predetermined length is
provided, and a reflection signal of the ultrasonic wave emitted by the vibrator is detected from
the modulation amount generated in the light transmitted through the optical fiber cable. FIG. 1
shows a system diagram of a fish finder to which an embodiment of the ultrasonic transducer
according to the present invention is applied. The same reference numerals as in the
conventional example of FIG. 5 denote the same parts. An l shows an example of a transducer
according to the present invention. A tip fiber sensor IB in which the optical fiber cable Z is
wound is loaded around a bobbin vibrator IA, which is a cylindrical vibrator whose inner and
outer surfaces are excitation electrodes. The number of turns of the optical fiber cable Z is
several thousand to several thousand turns. The lead wire 2 is electrically connected to the inner
peripheral surface and the outer peripheral surface of the bobbin vibrator IA via a suitable
bubbled Q made of copper thin film or the like, and the other end of the lead wire 2 is connected
to the changeover switch 3 It is connected to the transmitter 4 or the receiver 5 via this. Both
ends of the optical fiber sensor IB are connected to the light receiving element 56 through the
modulator 52 and the optical fiber coupler 55, respectively, as in the prior art. Also, optical fiber
sensor! Since B has a large drift due to temperature, the detection signal from the signal
processing circuit 59 is calibrated in the calibration circuit 6 by the transmission signal from the
transmitter 4. Next, the operation of the apparatus with the above configuration will be
described. At the time of transmission, the changeover switch 3 is switched to the transmitter 4
side, and the ultrasonic signal (frequency fs) output from the transmitter 4 is applied to the
bobbin vibrator IA, and the ultrasonic wave is emitted from the bobbin vibrator IA. Ru. After this
ultrasonic wave output, the switch 3 is switched to the receiving side, and the reflected wave
from the object 44 by the ultrasonic wave is received by the bobbin vibrator IA, and the received
signal obtained is transmitted through the switch 3. It is input to the receiver 5. The signal input
to the receiver 5 is processed into a predetermined signal as in the apparatus shown in FIG. On
the other hand, since the reflected wave also enters the optical fiber sensor IB, the object light
(frequency ro) from the modulator 52 is modulated by the ultrasonic signal (frequency fs), and
the modulation signal is transmitted through the optical fiber cable 57. Since the reference light
(frequency (f, + fb)) from the modulator 52 is incident on the optical fiber coupler 55, the
interference signal (frequency (fb S) ) of the light receiving element 56 is incident.
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The signal incident on the light receiving element 56 is processed into a predetermined signal by
the signal processing circuit 59, and is input to the calibration circuit 6. If it is at the time of
calibration, the received signal is calibrated by the transmission signal inputted from the
transmitter 4 in the calibration circuit 6, and in the subsequent detection operation, the
calibrated received signal is detected and displayed by the display 60. Depth information of the
object 44 is displayed. In the above-described apparatus, since the optical fiber sensor 1B is used
as a wave receiver, the receiver 5 is not particularly required. FIG. 2 shows another embodiment
of the transducer of the present invention. A front fiber cable Z is placed in a zigzag shape as an
optical fiber sensor on one surface of a square plate-like vibrator 21 having a square pattern, and
as shown by a black circle in the figure, bonding is performed at an appropriate position. It is
fixed to the plate-like vibrator 21 with an agent S or the like. Further, in order to excite the platelike vibrator 21, the lead wires 2 are electrically connected to the respective faces of the platelike vibrator 21 through pads Q made of copper thin film or the like. FIG. 3 shows another
embodiment of the present invention. An optical fiber cable Z is mounted in a high winding
manner at an appropriate pitch as an optical fiber sensor on one surface of a semi-square platelike vibrator 31 and a plate with an adhesive S or the like at an appropriate location. It is fixed to
the vibrator 31. Further, as in the previous embodiment, the lead wire 2 is connected to both
surfaces of the plate-like vibrator 31 via the pad Q. The ultrasonic transducer shown in FIGS. 2
and 3 is used with the surface provided with the optical fiber cable Z as the optical fiber sensor
directed in the direction to be measured. [Effects of the Invention] As described above, according
to the present invention, an optical fiber sensor consisting of an optical fiber cable acting as a
receiver is provided on a transducer that emits ultrasonic waves, and Since the reflected wave is
detected as an optical signal by the optical fiber sensor, there is no risk of receiving
electromagnetic noise as in the conventional system, and the S / N ratio is improved. Further,
since the transmitter and the receiver are integrally configured, the system can be miniaturized.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a control block diagram showing an example of a fish finder to which an embodiment of
the ultrasonic transducer according to the present invention is applied, and FIGS. 2 and 3 show
an ultrasonic transducer and an ultrasonic transducer according to the present invention
respectively. Another embodiment is shown in perspective and plan views, and FIGS. 4 and 5 are
block diagrams of a conventional fish finder.
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Reference Signs List 1: transmitter / receiver, IA: bobbin vibrator, eye 3: optical fiber sensor, 2:
lead wire, 3: changeover switch, 4: transmitter, 5. Receiver, 6: Calibration circuit, 21.31: Plate-like
vibrator, 51: laser light source, 52: ultrasonic light modulator, 53: oscillator, 55: tip fiber Coupler
56: light receiving element 57: optical fiber cable 59 signal processing circuit 60: indicator Z:
point fiber cable S: adhesive. Patent Assignee Furuno Electric Co., Ltd. Attorney Attorney
Attorneys Foreword Outside 18 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5
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