JPS6336255B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to an ultrasonic scanning device for medical use, and more particularly, to an ultrasonic scanning device for medical use, which generates a beam that scans at a relatively acute angle within an inspection plane and performs an inspection using a coupling liquid in a chamber. The present invention relates to an ultrasonic scanning device having an ultrasonic transducer for transmitting ultrasonic waves to a target specimen.

More specifically, it first includes a housing, in which a coupling liquid in which a disc-shaped piezoelectric element is immersed is provided, and a window through which the ultrasonic beam passes, an electric drive unit and an ultrasonic scanning probe, including mechanical means for producing an angular deviation of the beam in response to the rotational angle of a motor rotor; and second, a device for continuously displaying the beam angular position. It is related to.

Background Art Such a probe is for real-time ultrasound scanning used in cardiology, obstetrics, etc.
In such fields, the number of images that the device must display per second is, for example, on the order of 25 to 50, and it is important that the probe be extremely lightweight, compact, easy to use, low cost, and highly reliable. . In some of these applications it is useful to be able to operate the device using either the so-called "B-scan" or "TM" or "time movement" modes.
In the former, the position of the ultrasonic beam in the specimen is displayed instantaneously as a trajectory on the display CRT, while in the latter, the probe is stationary and temporal changes in the tissue to be examined are displayed. is displayed.

The "B-scan" mode requires a probe that can continuously display the angular position of the ultrasound beam. In this case, the ultrasonic beam scanning device must be equipped with equipment suitable for controlling the deviation of the electron beam based on the position information, and such equipment is well known and is not related to the present invention. .

The "TM mode" generally includes equipment that displays bright lines on a CRT screen that can be moved across the screen according to a portion of the image movement required for observation. Once this mode has been selected, the ultrasound beam is brought to a corresponding angular position and is fixed in that position; means are required to effect the appropriate angular movement of the beam.

SUMMARY OF THE INVENTION The purpose of the invention is to provide mechanical means that are particularly simple and effective in producing angular deviations of ultrasound beams.

Another object of the invention is to provide a system for indicating the angular position of an ultrasound beam, particularly suitable for use with said means for deflection.

Yet another object of the invention is a system for use with a probe to produce such an angular deflection of the beam suitable for changing the inspection device into TM mode, the system cooperating with means for said deflection. The goal is to provide a system that works.

In the device according to the invention, there is provided a disk-shaped piezoelectric transducer (hereinafter simply referred to as transducer) and a transducer drive unit having a shaft perpendicular to said window along a first axis. and the mechanical means includes a connecting rod capable of conical movement about the first axis;
means for an axis of rotation fixed at an axis passing through the diameter of the transducer and pivoting about an axis passing through the diameter of the transducer and perpendicular to said axis of rotation; The yoke is a member consisting of a bracket extending perpendicular to the axis of rotation of the transducer and parallel to the axis passing through the diameter, and L-shaped legs located at opposite ends of the bracket. The connecting rod is arranged to rotate about itself without translational movement along its own direction and is driven in a conical motion by a mechanical linkage connecting the rod to the shaft; The shaft and the axis of rotation are arranged integrally and in the same plane and even perpendicularly to each other, and the yoke is arranged on its bracket at the end of the connecting rod which is not connected to the mechanical linkage. It is fixed to the part.

The above-mentioned type of probe of the invention has, in addition to the main chamber, an auxiliary chamber in which a transducer is housed and which transmits an ultrasonic wave at a propagation velocity different from that in water. The auxiliary chamber is filled with a coupling fluid having a structure and is closed by a flexible membrane in the direction of propagation of the ultrasound waves, and the auxiliary chamber is surrounded by the main membrane and the flexible auxiliary membrane and contains water. , these two membranes and the coupling liquid have an acoustic impedance substantially similar to that of water, and at least a portion of the surface of the main membrane is arranged to ensure equilibrium between the liquid pressures in the two chambers. It is characterized by being made of a sufficiently flexible material.

Such a configuration prevents distortion of the auxiliary film from being transmitted to the main film when applied to the patient's skin, and the main film forms an interface between the two liquids, thereby preventing ultrasonic waves from being transmitted to the main film. It is possible to eliminate refraction caused by distortion.

Example Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a partial cross-sectional view through an axial plane of a probe according to an embodiment of the present invention, and FIG. 2 is a perspective view of a transducer drive mechanism. Both figures show a transducer 1 consisting of a disc-shaped piezoceramic pellet placed in the vicinity of a membrane 21 transparent to ultrasonic waves, the housing 2 being filled with a coupling fluid. This liquid is preferably of a type such as fluoride, in which the propagation speed of ultrasonic waves is lower than the propagation speed in water.

Since such liquids are inert, they can be used to submerge the motor. The housing 2 has a cylindrical shape terminated by a conical section, the end of which is closed by a membrane 21 . 22 is a cable,
It provides an electrical connection between the probe and the circuit of the testing device. In the present invention, it is possible to use a single cable as described below. Note that the cable up to the transducer 1 and the electrodes of the transducer 1 are not shown because they are connected by a known method.

The motor 3 is fixed to the housing by a sleeve 340 pierced by a channel 341 provided to allow liquid circulation.

The transducer 1 is swingable about an axis 100 perpendicular to the plane of FIG.
is on a diametrical axis extending in the transducer 1 in its diametrical direction. Motor shaft 31
is provided along the first axis of the housing 2, that is, the axis perpendicular to the thin film 21, and is rotatable, for example, by ±20° about a reference position determined by an electromagnetic or elastic system, as will be described later. It is. Disk 3 which is part of the linkage means
2 is attached to the shaft 31 at its center. The connecting rod 33 connects the disk 32 at a point 330 on the circumference of the disk 32, as will be described later.
2, it cooperates with a yoke 34 attached to the transducer 1, also in a manner described below.

FIG. 3 shows the linkage means forming the connection between the disk 32 and the connecting rod 33.
The head portion 331, which is the first end of the rod 33, is
The linkage means is such that the only possible movement of the rod 33 with respect to the disk 32 is rotation about the central longitudinal axis or axis of rotation of the connecting rod to the exclusion of any movement parallel to its own axis. It can be seen that it is engaged with a part of the bearing rig 332.

FIG. 4 shows the rod 3 at a position where the center line of the rod passes through the center O of the transducer 1.
3 and the yoke 34 are shown fixed. The yoke 34 is a member consisting of a bracket extending perpendicular to the rotation axis of the transducer 1 and parallel to an axis passing through the diameter, and L-shaped legs located at both ends of the bracket. Therefore, this rod is
It makes a conical movement about an axis that passes through O and coincides with the axis of the shaft 31. For example, half of the apex angle of this cone is 45°.

The transducer 1 is mounted on the bottom of a bush 101 which is fixed to a carrying cap 102. The members 101 and 102 are preferably made of plastic and the gap 103 between the side wall of the cap and the pusher 101 is filled with adhesive. The shaft 10 on the side wall of the cap
At opposite ends of the diametrically extending shaft 104 of the transducer 1 perpendicular to
Two trunnions 105-106 are installed (FIGS. 2 and 4) that work together with transducer 1
are fixed to the housing 2 at both ends of the shaft 100 by means of piezoelectric element support means (not shown), and as shown in FIG.
It is connected to bearings 107 and 108 fixed to the leg portions.

The motion that transducer 1 can draw is axis 100
It is clear that there is only oscillation around .
This shaft is attached to a cap 102 and has two cylindrical ears 10 that operate together with bearings that are piezoelectric element support means (not shown) attached to the housing 2.
01 and 1002.
The shaft 104 is located in the transducer 1 and vibrates itself in a plane passing through the center O and orthogonal to the shaft 100, and the yoke 34 is connected to the movable shaft 10.
It only vibrates around 4 and 33. In practice, a oscillation of the transducer 1, for example of the order of ±20° to 50°, can be obtained from rotational movement alone if play-free and slip-free members are used. It is clear that the disk 32 can be replaced by a crank. The present invention employs a structure similar to that of the well-known Cardan joint, and has two parts of the Cardan joint.
The shaft of the book corresponds to the yoke 34 and the housing 2 in the present invention, and the shaft of the book corresponds to the yoke 34 and the housing 2 in the present invention.
The cross member that connects the book shafts corresponds to the transducer 1 of the present invention. In a cardan joint, if one shaft is fixed and the other shaft makes a conical movement relative to the cardan joint, the intermediate cross member swings about the one shaft. Therefore, the transducer 1 of the present invention using such a cardan joint configuration swings about the axis 100 due to the conical movement of the yoke 34, causing an angular displacement of the ultrasonic beam.

In addition to reliability, this system is characterized by a unique relationship between the angular position of the shaft 31 and the angular position of the transducer 1, which provides an indication of the angular displacement of the radiation beam. It becomes convenient. This system allows the construction of coaxial probes, as the components, such as the disk 32 and the transducer 1 itself, are arranged symmetrically around the first axis of the motor shaft, and is especially suitable for use in psychrology. suitable.

Figure 5 shows the top surface of the disk 32 and the housing 2.
shows a cross section of Two small magnets 201 and 202 are mounted radially on the inner surface of the housing 2, covering a portion of the surface of the disk. A radially oriented magnet 320 is attached to the disk surface. These three magnets are magnetized in the tangential direction of the outer circumference of the disk, and the magnet 320
The magnetic poles of the magnets 201 and 202 are opposite to each other, and the opposing magnetic poles have the same polarity. As a result, the repulsive force acts as a return torque, and when the magnet 320 is not driven by the motor, both the magnets 201 and 2
It will come to rest at an equilibrium position between 02 and
If both magnets are under exactly the same conditions, they will be located at the same distance from both magnets. It is clear that the angle formed by the radius passing through magnets 201 and 202 needs to be slightly larger than the rotation angle of shaft 31. In this way, the reference angular position of the shaft 31 is determined.

These return torque means magnetic braking systems (not shown for simplicity in FIG. 2) can be mounted on other rotating members fixed to the motor shaft, as well as on springs or other It can be replaced by an elastic damping system using suitable means. Similarly, the motor can be replaced by a galvanometer system.

Membrane 21 may be flexible if the liquid in the housing is of the type described above, and may be a second flexible membrane bounding the first membrane of the auxiliary chamber containing water. Also good. However, in some cases, the thin film 21 may be used together with a material that absorbs ultrasonic waves in order to reduce unnecessary reflection by the film.

FIG. 6 shows a circuit as an excitation means for driving the motor. For example, an oscillator 35 that generates a sawtooth wave or a square wave with a repetition frequency of 100 Hz is shown, which is connected to an amplifier 84 and a resistor. 350 and an inductance element 351 with a high inductance value connected to each other by a cable 6,
352 (for example, 100 mH) serves as an exciting current for the motor 3. This motor has a resistance of 3
00 and the inductance element 301, and a back electromotive force (proportional to speed).
EMF).

4 is a pulse transmitter (having a predetermined frequency, for example between 2 and 5 MHz), and 5 is a receiver in the inspection device. Each of these elements is connected to an inductance element 351 and a capacitor 353, and the inductance element 352 is connected to the transducer 1 via a capacitor 354.

The output of the oscillator 35 is grounded via a potentiometer 355 connected in series with a resistor 356. Differential amplifier 357 has an output connected to the negative phase input of operational amplifier 359 via resistor 358, and the positive phase input of this amplifier 359 is grounded. The output of amplifier 359 is connected to its own negative phase input via a capacitor 360 connected in parallel with a resistor 361. The output of the amplifier 359 is connected to the control electrode of the CRT via a circuit that will be described later.

One input of amplifier 357 is potentiometer 35
The other inputs are connected to the common connection point of the resistor 350 and the inductance element 351, respectively.

Resistance 350, inductance elements 351 and 3
52. The low frequency current flowing in the armature winding of the motor is blocked by the capacitor 353.
There is no flow into the transmitter and receiver units 4 and 5, nor (by capacitor 354) into the transducer 1. Similarly, the respective transmission high frequency currents by the transmitter 4 to the transducer 1 and from the transducer to the receiver 5 due to the capacitors 353 and 354 are (inductance element 351
-352) without interfering with the low frequency current path mentioned above. In such a circuit configuration, connection between the transducer 1 and an external circuit can be made using only a single coaxial cable.

At the output of the operational amplifier 359 having an integral function, a voltage proportional to the angular deviation θ of the motor (and thus the transducer) with respect to the reference position is obtained, as described below.

The series connection configuration of series resistors 355 and 356, resistor 350, and motor impedance forms a bridge circuit, and amplifier 357 is connected to one of the bridges.
It is inserted and connected to two diagonal parts. (The inductance elements 351 and 352 are 100
At Hz, the impedance is negligible. )
If the potentiometer 355 is adjusted appropriately, the motor is stopped, and the bridge is balanced, no potential difference will occur between the two inputs of the amplifier 357. In the operating state, the voltage developed between both inputs is the back emf E
which is also proportional to the motor speed. Therefore, the amplifier 35 which is an integrator
At the output of 9, a voltage proportional to the angular deviation can be obtained.

To obtain an absolute indication of the angular position, it is first necessary to determine the mechanical reference position of the vibrating assembly, and secondly the output of the integrator 359 when there is no input signal (i.e. when the motor is stopped). It is necessary to reduce the voltage to zero.

The first condition is obtained by the magnet system described above, and the motor shaft is set in a predetermined position when there is no excitation current.

The second condition is obtained by capacitor 360 and resistor 361. Capacitor 360 is charged when a predetermined voltage is present at the amplifier input. If there is no input voltage, it is gradually discharged through the resistor 361, and the amplifier output returns to zero after a predetermined time.

The angular deviation information is applied to a well-known system 7 (terminal 4 of transmitter 4).
Input the transmission synchronization signal (from 0)7
00, and supplies sawtooth wave voltages with instantaneous amplitudes proportional to tsinθ and tcosθ to the control electrodes X and Y of the CRT, respectively. Here, t indicates time. The two switches 70 and 71 connect the two scanning generators 72-
These voltages are switched on and off according to the voltages supplied by 73, respectively. Generator 72 is for slow scanning on the screen, and generator 73 is for normal scanning (the sawtooth wave is synchronized with the transmission, so terminal 73
0 is connected to terminal 40).

The output of the integrator 359 is supplied to the differential amplifier 8 as a comparator, and its output is
It is connected via a capacitor 80 to an amplifier 81 connected to the brightness adjustment electrode Z of the display. Amplifier 8
The output 50 of the receiver 5 is supplied to the other input of the amplifier 8 via a resistor 51, and the slider of a potentiometer 82 is connected to the other input of the amplifier 8 to supply a DC voltage. This slider is also grounded via a potentiometer 83, and one input of an amplifier 84 is connected via a switch 85 to the slider of this potentiometer. amplifier 84
Other inputs include generator 3 via switch 86.
5 is connected, and this amplifier output is supplied to the windings of the motor 3.

When switch 86 is closed and switch 85 is open,
The motor supply voltage is the voltage from the generator 35, and the motor performs the rotational movement described above. At this time,
Switches 70 and 71 are at the positions indicated by "B" in the figure, so that the CRT is in the B mode scanning state.

Comparator 8 is the output voltage Kθ of integrator 359
and a reference voltage Kθ ₀ of the potentiometer 82, and when Kθ=Kθ ₀ , a rectangular wave signal is supplied to the electrode Z and superimposed on the video information. As a result, an emission line is displayed on the screen as a given angular position of the ultrasound beam.

When a specific tissue in motion is displayed on a screen for observation in accordance with the TM mode, the potentiometer 82 is adjusted to bring a bright line onto the tissue.

At the same time, operate switches 70-71-85-86. As a result, first the screen is scanned in a known manner according to the TM mode, and then the motor is no longer excited by anything other than the DC voltage KK ₁ θ ₀ .
Here, K ₁ is a proportionality constant that depends on the setting of potentiometer 83. This voltage causes the motor to generate a driving torque, and the motor rotates to a predetermined angle until it balances with the return torque determined by the above-described magnet structure. The potentiometer 83 is set at the factory so that its equilibrium position corresponds exactly to the one defined by the bright line described above.

Since the transducer drive mechanism has a return torque to the reference position, it is possible to switch from B mode to TM.
Switching between modes is easy.

FIG. 7 shows another modification of the bridge for measuring the rotational speed of a motor, which is part of the circuit of FIG. 6. In this example, resistor 355 in FIG. 6 is replaced by a gain control amplifier connected in series with resistor 356, and this gain control is performed by a synchronous demodulator.
365 output to resistor 366 and capacitor 367
This is done by applying a voltage through a filter. This demodulator 365 is connected to the bridge differential amplifier 357.
For example, 1000Hz supplied to the output and terminal 362 of
It is driven by the voltage of This latter voltage, preferably at a sufficiently high frequency so as not to rotate the motor, is also supplied via capacitor 363 to the common connection between resistor 350 and the input of amplifier 364. Inductance elements 351 and 352, which do not contribute to bridge balance in any way, have been omitted for simplicity. At 1000Hz, the motor does not generate a back emf, so it is clear that the bridge will remain balanced even if the motor is rotating.

The demodulator 365 is of a construction known per se, and if the bridge becomes unbalanced at 1000 Hz (for example, if the probe is converted),
It generates a DC voltage whose magnitude and polarity are proportional to the 1000 Hz error signal output from the amplifier 357. This DC voltage makes the gain of amplifier 364 variable to automatically balance the bridge.

FIG. 8 is a cross-sectional view of two thin-film probes according to another embodiment of the present invention, FIG. 9 is a perspective view of the terminal end of the probe with the outer thin film removed, and FIG. FIG. 8 is a sectional view taken along the - line in FIG. 8;

In FIG. 8, only the piezoelectric transducer 10 is shown for simplicity, which is driven by a motor indicated by dotted line 102 and a linkage indicated by dotted line 103 to It vibrates around an axis 101 that is perpendicular to .
These components are housed in a metal or plastic case, which has a removable conical portion 111 at its bottom and a cylindrical portion 110 extending therefrom. The conical part is adhesively surrounded near its bottom by a strip 112, which is a very thin and very flexible film made of, for example, natural rubber.
1 is provided with windows 1110 to 1113 (see FIGS. 9 and 10).

The bottom of the part 111 of the case is closed off by a membrane 113, which is fixed by an annular member and fitted tightly with pressure. This membrane is made of a relatively flexible material with the same acoustic impedance as water, such as natural rubber, silicone elastomer, polyethylene or
A plastic material (polyethylene-
propylene) etc.

If the latter is used, instead of elongating flat, the membrane is strong enough to be formed and strong enough to maintain its shape without stress. It is also possible to provide a predetermined curvature in advance.

A part 111 of the case part 110 near the connection part
A threaded bush 12 fixed to the sleeve 12 engages with a threaded portion provided on the upper part of a sleeve 13 made of a strong material. A thin film 14 made of a flexible material having an acoustic impedance equivalent to that of water, such as natural rubber, silicone elastomer, or polyurethane, is attached to the lower part of the sleeve by adhesive or the like.

Cases 110, 111, windows 1110 to 1113
The portion of the strip 112 and the thin film 11 corresponding to
The main closed chamber defined by 3 is filled with, for example, a fluorinated liquid having a density approximately twice that of water, and the ultrasonic propagation speed inside this chamber is half that of water, for example. As a result, the acoustic impedance of such a liquid is substantially equal to that of water.

The auxiliary closed chamber defined by the bush 12, sleeve 13 and membrane 14 is filled with water.

The portions of the strip 112 corresponding to the highly flexible windows 1110-1113 are distorted to provide a balanced permanent pressure between the two chambers. As a result, when this is applied to a patient's skin, the thin film 113 is not deformed due to the distortion of the thin film 14.

Air-filled cavity 114 closed by a flexible membrane in a special liquid in the main chamber
If the liquid is immersed, the volume change due to temperature will compensate for the resulting pressure change.

As described above, the thin film 113 may be given a predetermined curvature, and a converging lens for converging the ultrasonic beam may be used together with the liquid. In addition, a well-known type of acoustic lens can be used as a thin film 11.
Of course, it may also be used by adhering it to 3.

Obviously, various modifications may be made without departing from the spirit of the invention.

[Brief explanation of the drawing]

Fig. 1 is a view partially including a cross section passing through the axial plane of the probe according to the embodiment of the present invention, Fig. 2 is a perspective view of the transducer drive mechanism, and Fig. 3 is a state of connection and coupling between the drive units. Figure 4 is a diagram showing details of the transducer and the yoke that vibrates it, Figure 5 is a diagram showing the magnet mechanism for returning the motor to its reference position, and Figure 6 is a diagram showing the beam position angle. Figure 7 is a diagram showing the circuit of the display system and the circuit of the system that generates the angular displacement of the beam suitable for switching to TM mode; Figure 7 is a circuit diagram showing a modification of the bridge circuit for measuring the angular velocity of the motor; Figure 8 9 is a cross-sectional view of a probe having two thin films according to another embodiment of the present invention, FIG. 9 is a perspective view of the terminal end of the probe with the outer membrane removed, and FIG. 10 is a cross-sectional view taken along the - line in FIG. 8. It is a diagram. Explanation of symbols of main parts, 1...Transducer, 2...Housing, 3...Motor, 31...
Shaft, 33... Connection rod, 34... Yoke, 100... Vibration shaft.

Claims (1)

[Scope of Claims] 1. A longitudinal housing having a substantially flat planar portion at one end and having a window through which ultrasonic waves can pass, and containing a coupling liquid therein; a disc-shaped piezoelectric transducer having a center thereof; a motor means having a shaft disposed on a first axis perpendicular to the flat portion; and a mechanical coupling connecting the shaft and the piezoelectric transducer. excitation means for energizing said motor means with an excitation signal at a first frequency so as to obtain reciprocating rotational motion of said shaft; and excitation means for energizing said motor means at a reference angular position when said motor means is not energized at said first frequency. and means for generating a return torque for returning the rod to its own longitudinal direction, the mechanical coupling means comprising a connecting rod having first and second ends, and a rotation of the connecting rod only about its own longitudinal axis. linkage means coupled to a first end of the connecting rod for conical movement of the connecting rod about the first axis to prevent sliding thereof; and a linkage means fixedly positioned relative to the housing. The piezoelectric transducer is rotatably supported around a diametrical axis extending in the diametrical direction of the piezoelectric transducer, and the first axis and the diametrical axis are located on the same plane and arranged at right angles to each other. a yoke member comprising a bracket extending across the diameter of the piezoelectric transducer; yoke support means rotatably supports the yoke member around an axis passing through the center of the piezoelectric transducer, the yoke member supporting the second end of the connecting rod at a point on the bracket. 2. A probe according to claim 1, characterized in that the connecting rod is coupled to the piezoelectric transducer and is arranged such that the longitudinal axis of the connecting rod passes through the center of the piezoelectric transducer. 2. The linkage means comprises: a disk having a center perpendicular to and connected to the shaft; and a disk located at a distance from the center of the disk and rotatably supporting a first end of the connecting rod. the restoring torque generating means comprises a first magnet fixed to the disk, and a bearing attached to the housing at a position magnetically cooperating with the first magnet so as to exert a restoring torque on the first magnet. 2. The probe according to claim 1, comprising fixed second and third magnets. 3 comprising detection means for continuously detecting the angular position of said shaft, said detection means being connected to generate a first output signal and to sequentially measure a back electromotive force generated by said motor means; bridging means connected to the bridging means for integrating the first output signal to generate a second output signal; and integrating means connected to the integrator for integrating the first output signal to generate a second output signal; 2. The probe according to claim 1, further comprising erasing means for erasing the second output signal. 4. The bridge means has a variable gain amplifier having a control input, and the probe further includes a synchronous demodulator having first and second inputs and outputs, and an output of the synchronous demodulator to the control input of the variable gain amplifier. a first applying means for applying the first output signal to a first input of the synchronous demodulator; and synchronous demodulating an AC periodic voltage having a frequency substantially higher than the frequency of the first frequency. 4. The probe according to claim 3, further comprising a second input of the device and a second application means for applying the voltage to the bridge means. 5 deriving means connected to said integrating means and deriving a further voltage proportional to said second output signal;
comparing means for comparing the further voltage with an adjustable DC reference voltage; generating means for generating a square wave when the further voltage and the reference voltage are equal;
4. A probe according to claim 3, further comprising means for applying a DC voltage to said motor means proportional to a DC reference voltage and for canceling said excitation signal at a first frequency. 6. the window comprises a flexible membrane, the coupling fluid is selected such that the velocity of propagation of the ultrasound in the coupling fluid is substantially different from the velocity of propagation in water, and the probe further comprises: an auxiliary chamber consisting of a sleeve placed around the end and covering the end and the membrane and containing water; and a further flexible membrane placed on the sleeve opposite the membrane. the membrane, the further membrane and the coupling fluid have substantially the same acoustic impedance as water, and at least a portion of the surface of the membrane ensures parallelism between the two membranes and the further membrane. 4. The probe according to claim 3, having sufficient flexibility to 7. A probe according to claim 6, characterized in that the surface portion of the housing is provided with a flexible strip fixed to the rigid strip forming the window. 8 said sleeve comprises a longitudinal tube having first and second ends, said further membrane being attached to said second end and having a wall movable relative to said housing at said first end; 7. The probe according to claim 6, wherein the probe is attached to an end. 9. The probe according to claim 6, wherein a flexible closed container filled with air is immersed in the coupling liquid.