JP3027495B2 - Ultrasonic probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe suitable for use in, for example, an ultrasonic microscope or an ultrasonic flaw detector.

[0002]

2. Description of the Related Art FIGS. 6 to 10 show an ultrasonic microscope as an example using an ultrasonic probe according to the prior art.

[0003] In the figure, reference numeral 1 denotes an ultrasonic probe, which is generally constituted by an acoustic lens 2 and a piezoelectric element 3 described later.

[0004] Reference numeral 2 denotes an acoustic lens. The acoustic lens 2 is made of, for example, sapphire single crystal and has a piezoelectric element 3 to be described later attached to an upper end surface, and a lens surface 2A having a concave spherical surface at a lower end side.
The acoustic lens 2 propagates the ultrasonic wave incident from the piezoelectric element 3 in the axial direction and focuses the ultrasonic wave out of the lens surface 2A in the form of a beam.

[0005] Reference numeral 3 denotes a piezoelectric element as an ultrasonic vibrator. The piezoelectric element 3 has a lower electrode 3A formed on the upper end surface of the acoustic lens 2 and a means such as sputtering on the lower electrode 3A. Formed zinc oxide (Zn
O) It is composed of a piezoelectric body 3B such as a thin film and an upper electrode 3C formed on the piezoelectric body 3B. here,
When a pulse voltage is applied from a high-frequency pulse oscillator 4 described later, the piezoelectric element 3 generates a pulsed ultrasonic wave, and makes the ultrasonic wave incident on the acoustic lens 2 from the upper end surface.
The piezoelectric element 3 generates a reception signal (voltage) as shown in FIG. 8 between the upper electrode 3C and the lower electrode 3A when the piezoelectric element 3 vibrates due to a reflected wave incident from the lens surface 2A of the acoustic lens 2. Has become.

Reference numeral 4 denotes a high-frequency pulse oscillator for applying a high-frequency pulse voltage to the piezoelectric element 3 for excitation, 5 a receiver for processing a received signal of the piezoelectric element 3, and 6 according to the received signal processed by the receiver 5. This is a display device that displays an image (ultrasonic microscope image).

The ultrasonic microscope according to the prior art is configured as described above. In order to examine the surface shape of the sample 7, a liquid as an ultrasonic propagation medium is placed between the lens surface 2A of the ultrasonic probe 1 and the sample 7. For example, with the water 8 interposed, the ultrasonic wave made incident from the piezoelectric element 3 into the acoustic lens 2 is radiated from the lens surface 2A into the water 8, and the ultrasonic wave is focused on a focal point (not shown) on the sample 7. . After being reflected by the surface of the sample 7, the reflected wave (hereinafter, referred to as sample echo Es) is again incident on the acoustic lens 2 from the lens surface 2 </ b> A, and the piezoelectric element 3 is vibrated, as shown in FIG. The received signal of the echo Es is output from the piezoelectric element 3 to the receiver 5, the received signal is processed by the receiver 5, and the display device 6 visualizes an image corresponding to the received signal. .

[0008] Further, using the ultrasonic microscope shown in FIG.
When performing internal measurement or measuring the Young's modulus from the surface wave velocity of the sample 7 using an ultrasonic microscope, the ultrasonic probe 1 is brought close to the sample 7 as shown in FIG. The focus is moved (defocused) from the surface to the inside.

[0009]

In the prior art described above, a part of the ultrasonic wave incident on the acoustic lens 2 from the piezoelectric element 3 is internally reflected by the lens surface 2A, and the sample echo E
Returning to the piezoelectric element 3 before s, the reverberation shown in FIG. 8 (hereinafter referred to as an internal echo Ei) is detected.

Here, the internal echo Ei is internally reflected again at the upper end surface of the acoustic lens 2, reciprocates between the lens surface 2A, and decreases while decreasing the secondary internal echo 2Ei, the tertiary internal echo 3Ei, .. Are detected on the time axis at equal intervals.

Since the sound velocity in the water 8 is reduced to about 1/7 as compared with that in the acoustic lens 2, the ultrasonic probe 1 is moved slightly closer to the sample 7 from the state shown in FIG. However, the sample echo Es moves largely to the left as shown in FIG. For this reason, when the ultrasonic probe 1 is brought close to the sample 7 to be defocused, the sample echo Es tends to overlap with the secondary internal echo 2Ei,
There is a problem that the sample echo Es cannot be distinguished from the secondary internal echo 2Ei.

The present invention has been made in view of the above-mentioned problems of the prior art. Even if an ultrasonic probe is used so as to be close to a sample, the present invention does not provide any reverberation due to internal reflection of an acoustic lens and reflection from the sample. It is an object of the present invention to provide an ultrasonic probe capable of reliably discriminating a wave and greatly improving detection performance, reliability, and the like.

[0013]

In order to solve the above-mentioned problems, the present invention is directed to a method of transmitting ultrasonic waves between an ultrasonic transducer for transmitting ultrasonic waves and receiving a reflected wave and a sample. In an ultrasonic probe comprising a medium and an acoustic lens that focuses ultrasonic waves from the ultrasonic transducer toward the sample, the acoustic lens has a focal point on the sample.
At a certain time, it is formed with a predetermined lens length so that the propagation time of the ultrasonic wave propagating in the acoustic lens is longer than the propagation time in the propagation medium, and is reflected from the sample before
The reflected wave returned to the acoustic lens is the primary wave of the acoustic lens.
Between the reverberation due to the internal reflection and the reverberation due to the second order internal reflection
It is characterized in that it is configured to arrive at the ultrasonic transducer between them.

In this case, the acoustic lens has a focal length f, an aperture diameter D, an aperture angle θ, and a sound velocity in the acoustic lens C.
L, when the sound velocity in the propagation medium is represented by CM, the lens length L of the acoustic lens is It is preferable to set the relationship as follows.

[0015]

According to the above arrangement, the reflected wave from the sample can reach the ultrasonic transducer between the reverberation caused by the primary internal reflection of the acoustic lens and the reverberation caused by the secondary internal reflection of the acoustic lens. Even when moving toward the side, reverberation in the acoustic lens and reflected waves from the sample can be prevented from overlapping.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. In this embodiment, the same components as those of the above-described conventional technology are denoted by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 21 denotes an ultrasonic probe according to the present embodiment. The ultrasonic probe 21 is generally constituted by an acoustic lens 22 and a piezoelectric element 3 described later.

Reference numeral 22 denotes an acoustic lens.
Reference numeral 2 denotes a substantially cylindrical shape made of sapphire single crystal or the like having a piezoelectric element 3 attached to the upper end surface and a lens surface 22A having a concave spherical surface formed at the lower end side, substantially in the same manner as the acoustic lens 2 described in the prior art. However, the acoustic lens 22 is formed with a lens length L that satisfies a condition expressed by the following equation (4) so that the propagation time of the ultrasonic wave propagating in the acoustic lens 22 is longer than the propagation time in the water 8. ing.

Here, conditions that the lens length L of the acoustic lens 22 must satisfy in order to make the propagation time of the ultrasonic wave propagating in the acoustic lens 22 longer than the propagation time in the water 8 will be described.

First, as shown in FIG. 1, the distance from the upper end surface of the acoustic lens 22 provided with the piezoelectric element 3 to the lens surface 22A is A, and the distance from the lens surface 22A to the focal point P is f.
Then, the path for the internal echo Ei to reciprocate in the acoustic lens 22 is 2A, and the path for the ultrasonic wave to reciprocate between the lens surface 22A and the focal point P on the sample 7 (see FIG. 2) is 2f. The sound speed in the acoustic lens 22 is CL, and the sound speed in the water 8 is CM.
Then, the propagation time until the ultrasonic wave emitted from the piezoelectric element 3 is internally reflected by the lens surface 22A, returns to the piezoelectric element 3 and is detected as the internal echo Ei is (2A / CL).
The propagation time required for the ultrasonic wave emitted from the lens surface 22A to be reflected at the focal point P on the sample 7 and returned to the lens surface 22A is (2f / CM).

Therefore, the ultrasonic probe 2 according to the present embodiment
1 is that the time (2A / CL + 2f / CM) until the ultrasonic wave emitted from the piezoelectric element 3 is reflected on the sample 7 and detected as the sample echo Es by the piezoelectric element 3 is the primary time of the acoustic lens 22. Time of internal echo Ei (2A / CL)
And the time of the second internal echo 2Ei (2 × 2A / CL),

[0022]

## EQU1 ## The relationship of 2A / CL <2A / CL + 2f / CM <2.times.2A / CL is satisfied. Then, from this equation (1),

[0023]

## EQU2 ## The relationship of A / CL> f / CM> 0 holds.

On the other hand, if the aperture diameter of the acoustic lens 22 is D and the aperture angle is θ, the distance A from FIG.

[0025]

(Equation 3) Is required. The lens length L is given by the equations (2) and (3) with respect to the sound speeds CL and CM, the focal length f, the aperture diameter D and the aperture angle θ.

[0026]

(Equation 4) Are set to satisfy the following relationship.

For this reason, the ultrasonic probe 21 is brought closer to the sample 7 from the state of FIG. 2 as shown in FIG. 4, and the sample echo Es is changed from the side of the secondary internal echo 2Ei to the first order as shown in FIGS. Even when moving to the internal echo Ei side, it is possible to reliably prevent the sample echo Es from overlapping with the internal echoes Ei and 2Ei.

Therefore, according to this embodiment, the acoustic lens 2
2 and the sample echo Es arrive at the piezoelectric element 3 at the same time, and it is possible to prevent the sample echo Es from overlapping with the internal echoes Ei and 2Ei to become undetectable. Detection performance and operability can be greatly improved.

In the above-described embodiment, the case where the piezoelectric element 3 is used as the ultrasonic vibrator has been described as an example. Instead, for example, a magnetostrictive ultrasonic vibrator may be used. Is also good.

In the above embodiment, the ultrasonic microscope has been described as an example. However, the present invention is not limited to this, and may be applied to, for example, an ultrasonic flaw detector.

[0031]

As detailed above, according to the present invention, according to the calling <br/> light according to claim 1, before the time the focus of the acoustic lens is on the specimen
An acoustic lens having a predetermined lens length is formed so that the propagation time of the ultrasonic wave propagating through the acoustic lens is longer than the propagation time through the propagation medium, and the acoustic lens is reflected from the sample to produce the sound.
The reflected wave returning to the acoustic lens is the primary wave of the acoustic lens.
Between the reverberation due to surface reflection and the reverberation due to second order internal reflection
Since it is configured to arrive at the ultrasonic transducer, it can be set so that the reflected wave from the sample arrives at the ultrasonic transducer during reverberation due to primary and secondary internal reflection of the acoustic lens,
Even if the acoustic lens is moved closer to the sample side, the reverberation due to the internal reflection of the acoustic lens and the reflected wave from the sample can be reliably prevented from overlapping, greatly improving the detection performance and reliability of the ultrasonic probe. Can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an ultrasonic probe according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a use state of the ultrasonic probe shown in FIG. 1 in a state where a focus is formed on a sample.

FIG. 3 is a characteristic diagram showing a reception signal of the ultrasonic probe in the use state shown in FIG. 2;

FIG. 4 is a view similar to FIG. 2, illustrating a state in which the ultrasonic probe is used after being defocused.

FIG. 5 is a characteristic diagram showing a reception signal of the ultrasonic probe in the use state shown in FIG. 4;

FIG. 6 is an overall configuration diagram showing an ultrasonic microscope provided with an ultrasonic probe according to a conventional technique.

FIG. 7 is an explanatory diagram of a use state of the ultrasonic probe shown in FIG. 6 in a state where a focus is formed on a sample.

8 is a characteristic diagram showing a reception signal of the ultrasonic probe in the use state shown in FIG.

9 is an explanatory view similar to FIG. 7, illustrating a state in which the ultrasonic probe in FIG. 6 is used after being defocused.

FIG. 10 is a characteristic diagram showing a reception signal of the ultrasonic probe in the use state shown in FIG. 9;

[Explanation of symbols]

 Reference Signs List 3 piezoelectric element (ultrasonic transducer) 3A lower electrode 3B piezoelectric body 3C upper electrode 7 sample 8 water (propagation medium) 21 ultrasonic probe 22 acoustic lens 22A lens surface CM sound velocity in water (sound velocity in propagation medium) CL acoustic lens Medium speed of sound D Aperture diameter f Focal length L Lens length θ Aperture angle

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 29/00-29/28

Claims (2)

(57) [Claims] An ultrasonic wave transmitting medium for transmitting an ultrasonic wave and receiving a reflected wave is interposed between the ultrasonic wave transmitting medium and a sample, and the ultrasonic wave from the ultrasonic vibrator is directed to the sample. in the ultrasonic probe comprising an acoustic lens for focusing Te, before Symbol acoustic lens, when its focus is on the sample
The ultrasonic propagation time propagating in the acoustic lens is formed at a predetermined lens length to be longer than the propagation time in the propagation medium, the reflected wave returns to the acoustic lens and reflected from the sample
Is the reverberation due to the primary internal reflection of the acoustic lens and the secondary
Arrives at the ultrasonic transducer with the reverberation due to internal reflection of
An ultrasonic probe characterized in that the ultrasonic probe is configured to: 2. The acoustic lens according to claim 1, wherein the focal length is f, the aperture diameter is D, the aperture angle is θ, the sound velocity in the acoustic lens is CL, and the sound velocity in the propagation medium is CM. Length L, The ultrasonic probe according to claim 1, wherein the ultrasonic probe is set in the following relationship.