Measuring and testing – Vibration – Sensing apparatus
Reexamination Certificate
2002-05-20
2003-11-04
Moller, Richard A. (Department: 2856)
Measuring and testing
Vibration
Sensing apparatus
C367S155000, C310S31300R, C310S31300R, C333S154000, C333S193000
Reexamination Certificate
active
06640636
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for radiating an ultrasound into a material and receiving a reflected ultrasound by means of using a piezoelectric substrate, an interdigital arrangement of two comb-shaped electrodes formed on an upper end surface of the piezoelectric substrate, a counter electrode formed on a lower end surface of the piezoelectric substrate.
2. Description of the Prior Art
A thickness mode piezoelectric transducer with parallel plate-like electrodes is commonly used for radiating an ultrasound into a liquid. When receiving a reflected ultrasound from the liquid, such a conventional type of transducer needs, for example, a circulator in order to separate a delayed electric signal from an input electric signal, because the conventional type of transducer is used both as input- and output electrodes. Accordingly, such the conventional type of transducer has a difficulty in quick response measurement, and a complicated circuit-construction. In addition, such the conventional type of transducer has a difficulty in scanning operation.
On the other hand, an interdigital transducer on the piezoelectric substrate operates at a liquid-solid boundary as a leaky wave transducer for bulk wave radiation into the liquid. The leaky SAW traveling on a sufficiently thick substrate compared with the wavelength has only one mode without velocity dispersion. Such the interdigital transducer for the leaky SAW has a difficulty in making the radiation angle vertical.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an ultrasound radiating and receiving device capable of making an interdigital transducer act as a thickness mode transducer.
Another object of the present invention is to provide an ultrasound radiating and receiving device operating with a quick response.
Another object of the present invention is to provide an ultrasound radiating and receiving device need not a circulator, and so on.
Another object of the present invention is to provide an ultrasound radiating and receiving device capable of scanning operation.
Another object of the present invention is to provide an ultrasound radiating and receiving device capable of imaging of an object in a material.
Another object of the present invention is to provide an ultrasound radiating and receiving device capable of making the radiation angle vertical.
Another object of the present invention is to provide an ultrasound radiating and receiving device capable of low electric power consumption.
Another object of the present invention is to provide an ultrasound radiating and receiving device capable of radiating an ultrasound into a cellular tissue and receiving a reflected signal.
Another object of the present invention is to provide an ultrasound radiating and receiving device excellent in durability and manufacturing.
A still other object of the present invention is to provide an ultrasound radiating and receiving device easy in use and having a small size which is very light in weight and has a simple structure.
According to one aspect of the present invention there is provided an ultrasound radiating and receiving device comprising a piezoelectric substrate, first and second comb-shaped electrodes formed on an upper end surface of the piezoelectric substrate, and a counter electrode formed on a lower end surface of the piezoelectric substrate. The counter electrode is in contact with a surface-part of a material through the lower end surface of the counter electrode. The first- and second comb-shaped electrodes form an interdigital arrangement.
If an input electric signal is applied between the first comb-shaped electrode and the counter electrode, a longitudinal wave is radiated into the material through the surface-part of the material along the direction vertical to the lower end surface of the piezoelectric substrate. The, longitudinal wave is reflected at an object located inside the material. And then, a reflected longitudinal wave is detected between the second comb-shaped electrode and the counter electrode as a delayed electric signal.
According to another aspect of the present invention there is provided an amplifier between the first- and second comb-shaped electrodes. Thus, the delayed electric signal is amplified via the amplifier, and supplied to the first comb-shaped electrode as the input electric signal again.
According to another aspect of the present invention there is provided an ultrasound radiating and receiving device, wherein the opposite surface-part of the material acts as the object.
According to another aspect of the present invention there is provided an ultrasound radiating and receiving device, wherein the ratio of the interdigital periodicity of the interdigital arrangement to the thickness of the piezoelectric substrate is smaller than four times the ratio of the longitudinal wave velocity in the material to the longitudinal wave velocity in the piezoelectric substrate.
According to another aspect of the present invention there is provided an ultrasound radiating and receiving device, wherein increasing the number of electrode-finger pairs in the interdigital arrangement makes the directionality of the longitudinal wave sharper under a condition that the total amount of all the finger-areas of the first comb-shaped electrode is constant.
According to another aspect of the present invention there is provided an ultrasound radiating and receiving device, wherein the material is a liquid matter.
According to another aspect of the present invention there is provided an ultrasound radiating and receiving device, wherein the material is a cellular tissue.
According to another aspect of the present invention there is provided a polymer film, with which the lower end surface of the counter electrode is coated.
According to another aspect of the present invention there is provided a scanning unit composed of groups X
i
(i=1, 2, . . . , n) of switches, which correspond to the electrode-fingers of the first comb-shaped electrode, respectively. One and the next of the groups X
i
have common switches each other except the first switch of the one of the groups X
i
and the last switch of the next of the groups X
i
.
If input electric signals are applied between the first comb-shaped electrode and the counter electrode via the groups X
i
in turn, longitudinal waves are radiated along the direction vertical to the lower end surface of the piezoelectric substrate into the material in the form of a scanned ultrasound beam as a whole. The scanned ultrasound beam is reflected at the object, and detected between the second comb-shaped electrode and the counter electrode detecting as a scanned electric signal.
According to another aspect of the present invention there are provided a first scanning unit composed of groups X
i
(i=1, 2, . . . , n) of switches corresponding to the electrode-fingers of the first comb-shaped electrode, respectively, and a second scanning unit composed of groups Y
i
(i=1, 2, . . . , n) of switches corresponding to the electrode-fingers of the second comb-shaped electrode, respectively. One and the next of the groups X
i
have common switches each other except the first switch of the one of the groups X
i
and the last switch of the next of the groups X
i
. In the same way, one and the next of the groups Y
i
have common switches each other except the first switch of the one of the groups Y
i
and the last switch of the next of the groups Y
i
.
If input electric signals are applied between the first comb-shaped electrode and the counter electrode via the groups X
i
in turn, longitudinal waves are radiated along the direction vertical to the lower end surface of the piezoelectric substrate into the material in the form of a scanned ultrasound beam as a whole. The longitudinal waves are reflected at the object, and detected between the second comb-shaped electrode and the counter electrode by means of the groups Y
i
in turn in the form of a scanned electric signal as a w
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