JP2002044773A - Acoustic lens and ultrasonic transmitter - Google Patents

Abstract

(57) [Summary] [Problem] To focus an ultrasonic wave with almost no attenuation. SOLUTION: An ultrasonic transmitter 20 includes an ultrasonic radiator 22.
And an acoustic lens 24. The acoustic lens 24 is
It comprises a first reflector 26 and a second reflector 28 arranged concentrically. The first reflector 26 has a reflection surface 32 formed as a conical surface, and the ultrasonic wave 3
0 is reflected laterally. The second reflector 28 converts the ultrasonic waves 30 a reflected by the first reflector 26 on the reflection surface 38 into the ultrasonic waves 30.
The light is reflected in the forward direction of the ultrasonic wave radiating section 22 as shown in FIG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic lens for radiating ultrasonic waves into a gas or a liquid, and more particularly to an acoustic lens suitable for focusing ultrasonic waves radiated from an ultrasonic radiating portion and an acoustic lens. The present invention relates to an ultrasonic transducer.

[0002]

2. Description of the Related Art Ultrasonic waves have a high frequency and a short wavelength,
It has excellent directivity and can easily detect reflected waves. For this reason, ultrasonic waves are widely used in nondestructive inspection devices, measurement of fluid flow rates and flow rates, and the like. When using ultrasonic waves, the ultrasonic waves are generally radiated into the air or liquid, and are detected by detecting reflected waves from the object to be inspected or ultrasonic waves transmitted through the object to be inspected. Also, although ultrasonic waves are superior in directivity, they are much easier to diffuse than light, so in the case of precise flaw detection or the like, an ultrasonic probe called an ultrasonic probe as shown in FIG. There is a case where an ultrasonic wave emitted into the air is focused on one point and irradiated to an object to be inspected by using a wave device.

[0003] The conventional ultrasonic probe 10 shown in FIG.
An acoustic lens 14 is provided on the ultrasonic vibrator 12 serving as an ultrasonic radiating section.
Is attached. The acoustic lens 14 is formed of a material that is designed to reduce the acoustic impedance difference between the ultrasonic transducer 12 that generates an ultrasonic wave and the air through which the ultrasonic wave propagates, and the distal end surface 16 has a concave curved surface. Then, the ultrasonic waves 18 radiated from the distal end face 16 of the acoustic lens 14 are focused at the focal point O, and are radiated to the inspection object (not shown). The position of the focal point O of the ultrasonic wave 18 can be changed by changing the material of the acoustic lens 14 and the curved shape (curvature) of the distal end surface 16 of the acoustic lens 14. In order to focus the ultrasonic wave at one point, a method of installing a reflector having a concave surface in front of the ultrasonic generator and reflecting the ultrasonic wave by the reflector to focus the ultrasonic wave is also performed.

[0004]

However, the conventional ultrasonic probe 10 provided with the acoustic lens 14 is not suitable for the ultrasonic transducer 1.
Since the radiated ultrasonic waves 18 pass through the acoustic lens 14, the ultrasonic waves 18 are attenuated by the acoustic lens 14. Therefore, in order to detect the reflected wave of the ultrasonic wave 18 and the ultrasonic wave transmitted through the object to be inspected (not shown), it is necessary to generate the strong ultrasonic wave 18 having a large amplitude. In addition, the acoustic lens 14 is formed so that the thickness t is thinner at the center and gradually increases toward the periphery. For this reason, the ultrasonic waves 18 generated by the ultrasonic transducer 12 are
4, the sound beam passing through the center of the acoustic lens 14 and the sound beam passing through the peripheral edge of the acoustic lens 14 have different propagation distances, causing a phase shift in the ultrasonic signal. There is a drawback that interference occurs when the light is focused on O, which causes a decrease in sensitivity at the focal point O, and a disturbance or reduction in frequency.

On the other hand, in the method of installing a concave reflector in front of the ultrasonic wave generator, the focal position is different from the traveling direction of the ultrasonic wave emitted from the ultrasonic wave generator. For this reason, the structure of the ultrasonic probe becomes complicated or large. In addition, it becomes difficult to detect a reflected wave.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object to focus ultrasonic waves with almost no attenuation. Another object of the present invention is to focus ultrasonic waves while maintaining the broadband characteristics of the ultrasonic transducer.

[0007]

In order to achieve the above object, an acoustic lens according to the present invention is arranged in front of an ultrasonic radiating section and transmits an ultrasonic wave radiated from the ultrasonic radiating section to a side. It has a first reflector that reflects, and a second reflector that is provided on a side of the first reflector and reflects the ultrasonic wave reflected by the first reflector in a forward direction of the ultrasonic wave radiating unit. It is characterized by:

The first reflector and the second reflector are desirably formed of a substance having a large acoustic impedance, such as a metal or a ceramic, so as to reflect ultrasonic waves well. And the 1st reflector can form a reflective surface in a conical surface, and can make the vertex of a conical surface oppose an ultrasonic wave radiation part. The angle of the vertex of the conical surface can be set arbitrarily. The second reflector is formed on a concave curved surface that focuses the ultrasonic waves reflected by the first reflector on one point. Second
By changing the shape (curvature) of the curved surface of the reflector, the focus position (focal position) of the ultrasonic wave can be changed. Further, the reflection surface of the second reflector may reflect the ultrasonic wave reflected by the first reflector so as to be parallel to the axis of the second reflector. An ultrasonic transmitter according to the present invention includes an ultrasonic radiator including the above-described acoustic lens.

[0009]

According to the present invention constructed as described above, the ultrasonic waves emitted from the ultrasonic wave radiating section are reflected and focused by the first reflector and the second reflector, and the ultrasonic waves pass through the acoustic lens. Since the beam is focused by so-called total reflection without passing through, it is possible to minimize the attenuation of the ultrasonic wave. Moreover, it is possible to make the propagation distance of the sound flux of the ultrasonic wave radiated from each position of the ultrasonic wave radiating portion to the focal point constant, so that the ultrasonic waves having the same phase can be focused at the focal position. The ultrasonic waves that have been interfered,
Frequency disturbance and reduction can be prevented. For this reason, it is possible to focus the ultrasonic waves while maintaining the broadband characteristics of the ultrasonic transducer.

By making the reflecting surface of the first reflector a conical surface, the shape of the reflecting surface of the second reflector for focusing the ultrasonic wave can be easily obtained, and a desired shape can be obtained from the ultrasonic wave radiating section. An acoustic lens having a focal point at a distance can be easily designed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an acoustic lens and an ultrasonic transmitter according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view schematically showing an ultrasonic transmitter according to an embodiment of the present invention. In FIG. 1, the ultrasonic wave transmitter 20 includes an ultrasonic wave radiating unit 22 and an acoustic lens 24. The ultrasonic wave radiating section 22 has a built-in ultrasonic vibrator, and radiates (transmits) the ultrasonic waves 30 from a central portion on the right side of FIG. Further, the ultrasonic radiating unit 22 is a terminal unit (not shown) for applying a voltage to the ultrasonic vibrator or extracting an ultrasonic wave received by the ultrasonic radiating unit 22 as an electric signal, as described later. Is provided on the rear side.

The acoustic lens 24 includes a first reflector 26 and a second reflector 28 disposed around the first reflector 26. In the case of the embodiment, the first reflector 26 and the second reflector 28 are formed of a metal having a large acoustic impedance such as aluminum or brass.
Can be almost totally reflected. The first reflector 26 has a reflection surface 32 formed in a conical surface, and a vertex 34 faces the front surface of the ultrasonic radiation section 22. Also,
In the case of the embodiment, the first reflector 26 has an angle θ of the vertex 34.
Is 90 degrees, and as shown in FIG. 1, the ultrasonic wave 30 emitted by the ultrasonic wave radiating section 22 is reflected in a direction orthogonal to the axis 36 like the ultrasonic wave 30a.

The second reflector 28 is arranged concentrically with the first reflector 26, has an opening 37 in the center, and converts the ultrasonic waves 30 generated by the ultrasonic radiation section 22 into ultrasonic waves. The radiating portion 22 can be radiated forward. Also, the second
The reflector 28 has a concave reflecting surface 38 facing the first reflector 26, and the ultrasonic waves 30 a reflected by the first reflector 26 are further reflected by the ultrasonic waves 30 b by the reflecting surface 38.
As described above, the ultrasonic wave 30 is reflected in the forward direction of the ultrasonic wave radiating section 22 so that the ultrasonic wave 30 is focused on the focal point O. That is,
The reflecting surface 38 has a bisector of an angle α formed by the ultrasonic wave 30a reflected by the first reflector 26 and the ultrasonic wave 30b reflected by the second reflecting member 28, where the normal 40 enters the reflecting surface 38. Has become.

FIG. 2 shows details of the acoustic lens 24 in the case of the embodiment. That is, the acoustic lens 2
In the first reflector 26 of No. 4, a ring portion 44 is provided around a reflective main body 42 having a conical reflective surface 32. The reflection main body 42 includes a conical portion and a cylindrical portion, and the cylindrical portion is integrated with the ring portion 44 by a plurality of (three in the case of the embodiment) ribs 46. And the ring part 44
An external thread is formed on the outer peripheral surface, and this external thread is
The second reflector 28 is detachably screwed to the second reflector 28 by being screwed with a female screw portion provided on the inner peripheral surface of the distal end portion of the second reflector 28.

The second reflector 28 is provided with a mounting hole 48 on the rear end side.
2 can be detachably attached. The second reflector 28 has an inward flange-shaped stopper portion 50 formed at the tip of the mounting hole 48 so that the insertion amount of the ultrasonic wave radiating portion 22 can be made constant. Further, a holding member 52 formed of, for example, a rubber O-ring is provided on the distal end side of the mounting hole 48, and the acoustic lens 24 is mounted on the ultrasonic wave radiating section 22 via the second reflector 28. At times, the acoustic lens 24 is prevented from easily detaching from the ultrasonic wave radiating section 22.

When transmitting ultrasonic waves in the ultrasonic transmitter 20 according to the embodiment formed as described above, the operation is as follows. The ultrasonic wave transmitter 20 arranged in a gas such as the air transmits the ultrasonic wave 30 radiated from each position on the front surface of the ultrasonic wave radiating section 22 to the reflecting surface 32 of the first reflector 26 of the acoustic lens 24. Incident on. Reflection surface 32 of first reflector 26
Has a vertex 34 having a conical surface with an angle of 90 degrees, and the reflection surface 32 is inclined 45 degrees with respect to the axis 36. For this reason, as shown in the ultrasonic wave 30a, the ultrasonic wave 30 emitted by the ultrasonic wave radiating section 22
Then, the light is reflected in a direction (side) perpendicular to the plane and enters the reflection surface 38 of the second reflector 28. Then, the reflection surface 38 of the second reflector 28 converts the incident ultrasonic wave 30a into the ultrasonic wave 30b.
Reflected in the forward direction of the ultrasonic radiating section 22 as shown in FIG.
Focus on

As described above, in the acoustic lens 24 according to the embodiment, the ultrasonic wave 3
0 is reflected by the first reflector 26 and the second reflector 28 having a large acoustic impedance and is focused on the focal point O, so that the ultrasonic waves 30 can be substantially totally reflected and not attenuated. Can be focused. For this reason, when transmitting an ultrasonic wave having the same intensity as that of the related art, the driving voltage applied to the ultrasonic wave radiating unit 22 can be significantly reduced as compared with the related art. Moreover, it is possible to make the propagation distances of the ultrasonic waves 30 radiated from the respective positions of the ultrasonic wave radiating section 22 to the focal point O equal, and to eliminate the phase shift of the focused ultrasonic waves. It is possible to prevent phenomena such as interference of the focused ultrasonic waves and disturbance or reduction in frequency. Therefore, the ultrasonic radiation section 22
The ultrasonic waves 30 can be focused while maintaining the broadband characteristics possessed by.

In the above-described embodiment, the case where the acoustic lens 24 is mounted on the ultrasonic wave radiating section 22 serving as the ultrasonic wave transmitting section has been described. However, the acoustic lens 24 may be mounted on the ultrasonic wave receiving section. In the embodiment, the ultrasonic transmitter 20 has been described. However, as is well known, the ultrasonic transmitter 20 can be used as it is as an ultrasonic receiver. Then, when the ultrasonic transmitter 20 according to the embodiment is used as an ultrasonic transmitter / receiver and a non-destructive inspection is performed by an ultrasonic wave to determine whether or not the inspection target has a pore or a crack,
As shown in FIG. 1, the inspection target 60 is
At the focal point O of.

Thereafter, the ultrasonic wave transmitter 20 and the inspection target 6
While scanning the ultrasonic wave 30 by relatively moving 0,
The pulse-like ultrasonic wave 30 generated by the ultrasonic wave radiating unit 22 is irradiated to the inspection target 60, and the reflected wave is irradiated to the ultrasonic wave radiating unit 2.
2 to receive (receive). That is, the inspection target 6
The reflected wave from 0 propagates in the reverse direction on the propagation path of the ultrasonic wave 30 radiated by the ultrasonic wave radiating unit 22, is sequentially reflected by the second reflector 28 and the first reflector 26, and is reflected on the surface of the ultrasonic wave radiating unit 22. And vibrates the ultrasonic vibrator incorporated in the ultrasonic radiation section 22. The vibration of the ultrasonic vibrator is extracted as an electric signal from a terminal provided on the rear surface of the ultrasonic radiating section 22.

In the above embodiment, the first reflector 2
Although the case where the angle θ of the vertex 34 of No. 6 is 90 degrees has been described, the angle θ of the vertex 34 can be arbitrarily formed. Further, by changing the shape (curvature) of the concave curved surface of the reflecting surface 38 of the second reflector 28, the distance L between the front surface of the ultrasonic wave radiating section 22 and the focal point O can be set arbitrarily. And in the said embodiment, the 2nd radiator 2
Although the case where the ultrasonic wave 30 is focused on the focal point O by the reflecting surface 38 of FIG. 8 has been described, the ultrasonic wave 30 may be reflected so as to be parallel to the axis 36. Further, in the above embodiment, the case where the ultrasonic waves 30 are emitted into the air has been described, but the ultrasonic waves 30 may be emitted into a liquid such as water. Further, in the above-described embodiment, the case where the first reflector 26 has three ribs 46 has been described, but the number of ribs 46 may be two or more. However, if the number of ribs 46 is too large or too large, the ultrasonic waves 3
It should be noted that the amount of zeros increases and the amount of focused ultrasonic waves 30 decreases. In the above-described embodiment, the case where the acoustic lens 24 is formed of metal has been described. However, the material for forming the acoustic lens may be another material such as ceramic as long as it has a large acoustic impedance. In the above embodiment,
Although the case where the first reflector 26 and the second reflector 28 are formed separately has been described, these may be formed integrally.

Further, in the above embodiment, the ultrasonic wave transmitter 20 is arranged on one side of the inspection target 60, and the reflected wave from the inspection target 60 is transmitted by the ultrasonic transmission The case of detection by the detector 20 has been described,
A pair of ultrasonic wave transmitters 20 (20a, 20b) are arranged on both sides of the inspection object 60 in line symmetry with respect to the focal point 30, and the ultrasonic wave is emitted by one ultrasonic wave transmitter 20a to focus the ultrasonic wave. O is focused and irradiated, and the other ultrasonic wave transmitter 20b
The ultrasonic wave transmitted through the inspection target 60 may be detected.

[0022]

As described above, according to the present invention,
The ultrasonic wave emitted from the ultrasonic wave radiating unit is reflected and focused by the first reflector and the second reflector, and the ultrasonic wave is focused by so-called total reflection without passing through the acoustic lens. Therefore, it is possible to minimize the attenuation of the ultrasonic wave. Moreover, it is possible to make the propagation distance of the sound flux radiated from each position of the ultrasonic wave radiating portion to the focal point constant, and to focus the ultrasonic waves having the same phase at the focal position. It is possible to prevent interference and disturbance or reduction in frequency. For this reason, it is possible to focus the ultrasonic waves while maintaining the broadband characteristics of the ultrasonic transducer.

Further, according to the present invention, since the reflecting surface of the first reflector is formed in a conical shape, the shape of the reflecting surface of the second reflector for focusing the ultrasonic wave can be easily obtained, and the ultrasonic wave can be easily obtained. An acoustic lens having a focal point at a desired position from the radiating section can be easily designed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating an ultrasonic transmitter according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing details of the acoustic lens according to the embodiment, wherein FIG. 2A is a front view, and FIG. 2B is a cross-sectional view taken along line AA of FIG.

FIG. 3 is an explanatory diagram of a conventional ultrasonic wave transmitter.

[Explanation of symbols]

20 ultrasonic transmitter, 22 ultrasonic radiation part, 2
4 ... Acoustic lens, 26 ... First reflector, 28 ...
... second reflector, 30, 30a, 30b ... ultrasonic wave, 3
2, 38... Reflective surface.

Claims (3)

[Claims] A first member disposed in front of the ultrasonic radiating portion for reflecting ultrasonic waves radiated from the ultrasonic radiating portion to the side;
A reflector provided on a side of the first reflector and reflecting the ultrasonic wave reflected by the first reflector in a forward direction of the ultrasonic radiation section; Acoustic lens. 2. The first reflector has a reflection surface formed as a conical surface having a vertex opposed to the ultrasonic wave radiating portion, and the second reflector has the ultrasonic wave reflected by the first reflector. The acoustic lens according to claim 1, wherein the acoustic lens is formed on a concave curved surface that converges at one point. 3. An ultrasonic transmitter comprising an ultrasonic radiating section provided with the acoustic lens according to claim 1.