JPH0556967A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To enhance the sensitivity at the time of detecting vibration of the mirror surface, in the ultrasonic probe for fetching a reflected wave of an ultrasonic wave radiated into a living body as vibration of the mirror surface by an interference of a laser light. CONSTITUTION:By a reflected wave from an examining body 7, the thin film mirror surface 12 vibrates. A laser emitted from a projector 8 passes through an incident hole 11 of the upper face mirror 10 and is reflected by the thin film mirror surface 12 and subjected to multiple reflection, and thereafter, goes out of an emitting hole 13 and reaches a photodetector 14. In the photodetector 14, vibration of the thin film mirror surface 12 is detected by a phase difference caused by an interference of the transmitted laser and the photodetected laser. Since a multiple reflection of the laser is executed in a groove 9, the phase difference increases and the sensitivity is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave receiving circuit in an ultrasonic probe and a device for receiving a wave by a laser.

[0002]

2. Description of the Related Art In an ultrasonic probe of an ultrasonic diagnostic apparatus, a conventional wave receiver detects an ultrasonic wave by a piezoelectric element, and in principle, the mechanical energy of a sample is received by a piezoelectric element having a mass. Since the pressure due to vibration is converted into electric energy, energy loss cannot be avoided. On the other hand, a method of transmitting the vibration of the specimen to a thin mirror with a small mass, reflecting the laser on the mirror and detecting the vibration with the laser has been developed as a non-contact measurement technology in other departments. The detection method is to detect the phase of the interference wave generated by adding the laser used for projection to the reflected laser as an electric signal with an electronic circuit of homodyne detection, or change the frequency of the laser used for projection and change the reflected laser Ultrasonic vibrations are detected by an electronic circuit of heterodyne detection between and. Therefore, there is a limit to the detection sensitivity that the electronic circuit cannot detect unless the change in the luminous intensity of the interference wave of the wavelength of the two-wave laser input to the electronic circuit is large to some extent. This limit was the limit of the amplitude of the detected microvibration. In other words, the laser method has a limitation in detecting the amplitude of vibration due to the performance of the electronic circuit.

[0003]

However, in order to detect the vibration amplitude of ultrasonic waves to a smaller value, the phase difference for the same small vibration amplitude is increased by shortening the wavelength of the laser used. A method of doing so is also conceivable, but a mirror that is microscopically flat with respect to ultraviolet rays and short wavelengths shorter than that and has a reflectance similar to that of visible light becomes gradually difficult in terms of cost.

Therefore, in a conventional laser system, 2
It is desired to detect a highly sensitive phase difference between lasers of a wave.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to newly provide a higher sensitivity mechanism for a laser type receiving circuit of a probe.

[0006]

In order to achieve the above object, the present invention provides a reflection laser by projecting a laser at a slight inclination to a thin mirror in contact with a specimen or a portion where ultrasonic vibration of the specimen is best transmitted. By repeating the reflection with another mirror facing each other, progressively reflecting it, and taking it out,
The purpose is to detect with an electronic circuit after increasing the fluctuation of the phase due to the vibration of the specimen.

[0007]

According to the above construction, since the phase displacement increases in proportion to the number of multiple reflections, the detection limit of the phase amount is reduced in proportion to the number of multiple reflections even in the same electronic circuit. High sensitivity is possible.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an ultrasonic diagnostic apparatus 1 according to the present invention.
The specific configuration of the probe 2 in FIG.

A trigger signal is sent from the ultrasonic diagnostic apparatus 1 to the probe 2 via the cable 3, and although not shown in the drawing of the ultrasonic transmitter array 4, a single signal or a plurality of signals are synchronized with the trigger. A high-voltage pulse is supplied to the element 5 of the device 5, and one or a few waves of ultrasonic waves of 3.5 MHz are supplied from the device 5 to the specimen 7 through the acoustic lens 6, and at the same time, the plurality of elements are supplied. A laser beam whose projection direction and projection time are controlled in synchronization with the trigger is projected from the projector 8 toward the entrance hole 11 of the top mirror 10 forming the top surface of the adjacent groove 9 of 5.

One projection duration is such that the ultrasonic wave is continuously projected for the time required for one round trip through the deepest part of the sample.

The projected laser beam is first reflected by the thin film mirror surface 12 forming the bottom surface of the groove 9, then by the opposing top surface mirror 10, and is repeatedly reflected between the thin film mirror surface 12 and the upper surface. The laser beam guided to the emission hole 13 provided at an appropriate place of the mirror 10 and exiting the groove from the emission hole 13 is received by the light receiver 14 whose light receiving direction is controlled by a trigger.

The repetitive multiple reflections recited in claim 5, the optical amplification recited in claim 6, and the iterations recited in claim 7 cause the light to be received by the light receiver 14 by a trigger corresponding to a preset distance step. An amplifier is built in, and after being amplified there, the light is projected through the light projector 8 in the same manner as at the beginning.

In FIG. 2, the rows of the entrance holes 11 and the exit holes 13 in the groove 9 are formed as different rows, and the mirror structure is such that the reflection points of the top mirror 10 during multiple reflection do not overlap. ..

The section length between the entrance hole 11 and the exit hole 13 in the groove 9 is, for example, one vibration element array according to claim 1, the observation depth is D = 20 mm, and the frequency is 3.5 M.
The wavelength λ of the ultrasonic wave of Hz is 0.44 mm from the relationship of wavelength = propagation velocity / frequency, and the depth indicates the range of signal addition within half a wavelength in round trip propagation of transmission and reception. The radius r ₁ of the first Fresnel zone is in the order of r ₁ = 2.1 mm from the equation r ₁ = (Dλ / 2) ^1/2 , and is proportional to the square root of the depth D to be observed. From the viewpoint, the section length is determined so as to be sufficiently within the diameter of this Fresnel zone, 2r ₁ = 4.2 mm. Note that if a sufficient number of multiple reflections are obtained within this section length, this is a common basic signal for any distance, so it is not within the scope of the present invention. The signal can be thinned out as a signal common to the synthesis of signals for the observation depth in the specimen of millimeters to several tens of centimeters to facilitate selection.

On the other hand, since the signal becomes weaker as the depth of observation increases, the number of multiple reflections and the number of repetitions are increased in order to increase the sensitivity in consideration of the above. According to claims 2 and 3, a narrow groove 9 of about several microns is formed in the center of the strip-shaped array element, and the entrance hole 11 is formed.
And the exit hole 13 are opened at scanning intervals, and the entrance hole 11 of the groove 9 and the exit hole 13 which are located near the center of the group of plural elements when scanning the ultrasonic beam are both within the range of the first Fresnel zone. Make the intervals so that you can enter.

The laser wave received by the light receiver 14 is simply shown as the detector 16 in FIG. 1. In the detector 16, for example, the coherent light from the projector 8 is demultiplexed and mixed to perform homodyne detection. Ultrasonic vibrations of minute amplitude reflected from the inside of the specimen can be detected as electric signals with high sensitivity as phase fluctuations of the laser.

The detected signal is sent to the ultrasonic diagnostic apparatus 1 by the cable 17 as in the case of a normal transducer.

[0019]

As described above, according to the present invention,
Small vibration of ultrasonic waves in a small section limited by laser,
Since the phase difference between the two lasers can be expanded and supplied to the electronic circuit by performing multiple repetitions in the section length of a fraction to several times of the individual elements of the ultrasonic wave transmitter array. You can receive with high sensitivity. As a result, not only medical treatment but also ultrasonic measurement technology can be further improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an internal structure of an ultrasonic probe 2 according to the present invention.

FIG. 2 is an explanatory diagram showing multiple reflection of a laser.

[Explanation of symbols]

 1 Ultrasonic Diagnostic Device 2 Probe 4 Ultrasonic Vibration Element Array (Array Type Ultrasonic Transducer) 9 Groove 10 Top Mirror 11 Entrance Hole 12 Thin Film Mirror Surface 13 Exit Hole

Claims (7)

[Claims] 1. A probe for scanning an ultrasonic beam to a specific depth in a specimen by delay combination pulse driving to a plurality of elements in one vibrating element array, wherein an ultrasonic reflected wave from the specimen is used. Directly onto the surface of the specimen or onto a thin reflecting mirror in contact with an intervening acoustic matching material, scanning projection is performed on the groove of the drive element in synchronization with ultrasonic scanning, and the surface of the drive element in the groove is projected. Combined with the transmitted wave, within a distance limited to the first Fresnel zone, multiple reflection of the laser is carried out in the section of the laser waveguide composed of the thin reflection mirror on one surface, and then mixed interference with the transmitted laser is performed. An ultrasonic probe characterized by receiving ultrasonic waves by detecting a phase difference that vibrates. 2. A plurality of vibrating element arrays are formed into a single band, and the bands are simultaneously scanned with a plurality of concentric circles, and for each vibrating element that enters the same ring surrounded by the concentric circles, The ultrasonic probe having a structure in which ultrasonic output is concentrated at an observation point in a sample by pulse driving having a delay time proportional to the square of the radius, according to claim 1, wherein a groove of the central vibration element array is provided. An ultrasonic probe characterized by receiving ultrasonic waves by a laser device. 3. The ultrasonic probe according to claim 2, wherein a plurality of concentric circles are used as elements covered by an annulus of up to 5 Fresnel zones to generate an ultrasonic beam by positive and negative drive pulses. A characteristic ultrasonic probe. 4. An ultrasonic probe using an acoustic lens according to any one of claims 1 to 3, wherein a laser reflection is applied to a boundary surface of the acoustic lens on the vibrating element side. An ultrasonic probe having a thin mirror for use. 5. The ultrasonic probe according to any one of claims 1 to 4, wherein the laser after multiple reflection is taken out after reciprocating the multiple reflection path once or more again. An ultrasonic probe characterized by being provided with. 6. The ultrasonic probe according to claim 5, further comprising a circuit for optically amplifying attenuation due to multiple reflection during a round trip. 7. The ultrasonic probe according to any one of claims 1 to 6, wherein the number of multiple reflections or the number of repeated reflections is increased in accordance with the depth of the specimen to be observed. An ultrasonic probe characterized in that.