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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method and apparatus for measuring or observing an object by ultrasonic waves.
2. Description of the Related Art Such a device is described in the Journal of the Acoustical
Society of Japan, Vol. 31, No. 12 pp. The device described in 716-724 (1975) is known.
SUMMARY OF THE INVENTION According to the conventional configuration, the viewing angle is
narrowly limited.
An object of the present invention is to double the viewing angle with a simple configuration,
paying attention to the characteristics of the reverse polarization array sound source.
SUMMARY OF THE INVENTION In order to observe two directions simultaneously, this is
achieved by providing an ultrasonic transducer in which the transmission or reception direction
changes according to the signal frequency.
The structure shown in FIG. 1 is an example of a transmitter in which the transmission direction
of the ultrasonic wave changes according to the signal frequency.
In this transmitter 1, since the polarization axes of the piezoelectric elements are sequentially
reversed and arranged, the signal of wavelength λ travels in the direction of the arrow, and this
direction changes depending on the wavelength.
However, when transmitting by this method, an ultrasonic wave front is transmitted not only in
the solid line direction but also in the reverse dotted line direction.
By using the transmission signals in the reverse direction, a double field of view can be realized.
For example, as shown in FIG. 2, the sound absorbing material 2 is disposed on the front surface,
and this can be moved to the left and right to select the field of view.
Further, as shown in FIG. 3, by making the distance to the lens different, the reflected signal from
the blood vessel wall 3 at a short distance is displayed in front of the object 4 and therefore the
situation in two directions is simultaneously separated on the same screen. It can be displayed.
On the other hand, as shown in FIG. 4, it is possible to form a wave front on only one side by
using a signal shifted in phase by 90 degrees (Japanese Patent Laid-Open No. 47-26160), and by
changing the application method of this signal. Selective observation of each direction is possible.
An embodiment of the scheme according to the invention is shown in FIG. Here, 5 is a transmitter
shown in FIG. 4 in which the transmission direction of the ultrasonic wave changes according to
the signal frequency, and the signal by the transmission unit shown in 7 is partially phase shifted
by ± 90 degrees phase shifter 6 and applied. Be done. Control of this phase shifter is performed
by the direction selection unit 8. The transmission carried out in this way is transmitted in only
one direction, and a reflected signal is likewise obtained by 5. The signals of the signal lines a
and b are subjected to phase shift processing in order to similarly receive in the direction
corresponding to the transmission direction, and after being added, they are imaged by the
reception processing unit and the corresponding screen position of the display unit 10 Display
on Here, A and B correspond to the left and right images.
A field where such a configuration with a small number of signal lines is used particularly
effectively is, for example, observation from the inside of a blood vessel or insertion into the
rectum, etc., in these narrow cases. It becomes very effective by setting the outer diameter to 20
mm or less in diameter and further 5 mm or less in the blood vessel. Of course, application to
two-dimensional, three-dimensional or Doppler measurement is also possible. Furthermore, all
combinations with known techniques for ordinary reverse polarization array sound sources such
as curved surface arrays are also possible.
According to the present invention, such a method makes it possible to form a doubled field of
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