JPS6348100A - Ultrasonic wave generating method - Google Patents

Abstract

PURPOSE:To generate a desired ultrasonic wave at the inside of a substrate or on its surface by generating intensity-modulated electron beams in the respective electron beam sources of an electron generating means by separately controlling them, and radiating the beams on the substrate. CONSTITUTION:The titled method is formed with an electron beam generating means EBH in which the plural electron beam source EBS separately controllable are arrayed two-dimensionally, and the substrate SUB, and the intensity- modulated electron beams are generated and controlled by the electron beam sources of the electron beam generating means. The substrate is radiated with thus thus generated electron beams, and generates a ultrasonic wave. To the electron beam sources EBSs, common electrodes X1, X2,... Y1, Y2,... in matrix form in vertical and horizontal directions are connected. The other ends of the electrodes X1, X2,... are connected to a control circuit CONT 1 and those of the electrodes Y1, Y2,... are connected to a control circuit CONT 2. For instance, if the control circuit CONT 1 selects the electrode X3 and the control circuit CONT 2 selects the electrode Y4, the electron beam source EBS 34 in a third column and in a fourth row is selected to be driven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic generation method using a plurality of independently driveable electron beam generation sources in the case of generating ultrasonic waves. It is something.

[Conventional technology] Volume wave (
Methods using ultrasonic waves generated inside or on the surface of solids, such as bulk waves) and surface acoustic waves, have been researched and put into practical use. 7 and 8 are schematic configuration diagrams showing an example of a conventionally used method for generating volume waves and surface acoustic waves,
The general functions will be explained below based on these.

As a volume wave generation method, a neck attachment and method as shown in FIG. 7 are commonly used. That is, the piezoelectric material P is sandwiched between the electrodes on the substrate S on which ultrasonic waves are to be generated;
2 is installed, and a high frequency signal source SG is installed between the electrodes D1 and D2.
is connected. The high frequency signal generated by this high frequency signal source SG is applied between the electrodes D1 and 02, and the piezoelectric body P
According to its piezoelectricity, electrical signals are converted into mechanical vibrations to generate ultrasonic waves. Then, this ultrasonic wave is transmitted to the substrate S and becomes a plane wave APW of the volume wave to the substrate S.
The light propagates through the substrate S in a direction DP perpendicular to the surface thereof.

To generate surface acoustic waves, a device is usually used in which a comb-shaped electrode IDT is provided on a piezoelectric substrate PS and a high-frequency signal source SG is connected to the comb-shaped electrode IDT, as shown in FIG. The high frequency signal applied from the high frequency signal source SG to the comb-shaped electrode IDT is converted into a surface acoustic wave SAW by the piezoelectricity of the substrate PS, and propagates in two directions DPI and DP2.

However, such conventional methods for generating volume waves and surface acoustic waves have the following drawbacks.

(2) Piezoelectric materials are essential because piezoelectricity is used to convert electrical signals into ultrasonic waves. Particularly in surface acoustic waves, it is difficult to propagate surface acoustic waves to other substrates without energy loss, so it is almost impossible to efficiently excite surface acoustic waves on a non-piezoelectric substrate.

■The frequency band of the signal that can pass through a transducer that converts electrical I3 into ultrasonic waves is determined by its shape, so it is difficult to obtain a wide bandwidth of ultrasonic waves that can be excited by one transducer. do not have.

(2) Since the propagation direction of the ultrasonic wave is uniquely determined by the shape of the transducer, it is impossible to excite it in any direction.

(8) Volume wave and surface acoustic wave transducers have completely different shapes, so it is impossible to create a structure that can excite both with a single transducer.

Therefore, it is desired to realize an ultrasonic generation method that eliminates the above-mentioned drawbacks.

[Objective of the Invention] An object of the present invention is to individually generate a plurality of intensity-modulated electron beams from an electron beam generating means and irradiate them onto an arbitrary solid substrate, thereby producing a desired superposition inside or on the surface of the substrate. An object of the present invention is to provide an ultrasonic generation method for generating sound waves.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide an electron beam generating means comprising a substrate and an electron beam generating means in which a plurality of independently driven electron beam sources are two-dimensionally arranged; This is an ultrasonic generation method characterized in that intensity-modulated electron beams are individually controlled and generated from each electron beam source, and ultrasonic waves are generated by irradiating the substrate with the electron beams.

[Embodiments of the Invention] The present invention will be described in detail below based on the embodiments illustrated in FIGS. 1 to 6.

FIG. 1 is a schematic configuration diagram for realizing the method according to the present invention, in which electron beam sources EBS are two-dimensionally arranged at equal intervals on the lower surface of solid-state electron beam generating means EBH. A substrate SOB is arranged below the generating means EBH, and an electrode MAC for applying an accelerating voltage is formed on the surface of the electron beam generating means EBH facing the substrate SOB. On the other hand, the substrate SUB is any solid body, and a direct acceleration voltage VAC is applied between it and the electrode MAC. Note that if the substrate SUB is Trf or a generous insulator, a metal electrode may be formed on the surface and the accelerating voltage VAC may be applied.

As an electron beam source EBS, for example, Japanese Patent Publication No. 54-3027
No. 4, JP 54-111272, JP 56-155
29, Japanese Unexamined Patent Publication No. 57-38528, and the like can be used. this is,
By supplying a reverse voltage to the pn+m junction to cause electron avalanche multiplication, electrons are generated within the semiconductor substrate, and the electrons are emitted from the semiconductor substrate. According to it,
The electron beam source EBS arranged two-dimensionally on the electron beam generating means EB)I is configured to apply a reverse voltage to the electron beam source EB.
By appropriately controlling each S, it is possible to drive each S independently.

FIG. 2 is a sectional view for explaining the operation of the embodiment shown in FIG. 1. The two-dimensionally arranged electron beam sources EBS can be individually controlled to generate electron beams.

In the example shown in Fig. 2, electron beams CE in the range of several kHz to several 100 MH2 are simultaneously interrupted from all electron beam sources EBS.
B is generated. The intermittently generated electron beam CEB is accelerated by the accelerating voltage VAC and collides with the surface of the substrate SUB, generating ultrasonic waves having a frequency equal to the intermittent frequency of the electron beam CEB on the substrate SOB.

The generation of ultrasonic waves in a substrate by the collision of a single intermittent electron beam is described, for example, in ``Ikoma, Morizuka, ``Electron Beam Ultrasonic Microscope,'' Applied Physics No. 51, No. 2 (1982), 2.
05 (page 95)”. According to this, most of the energy of an electron beam that is accelerated and collides with the substrate surface becomes heat, and heat waves are generated within the substrate. This heat wave becomes an ultrasonic wave and propagates through the substrate due to the thermoelastic effect, and the frequency of the ultrasonic wave at this time is equal to the intermittent frequency of the electron beam.

When such an electron beam is used, the source of the ultrasonic wave is one point, and the ultrasonic wave generated from that point becomes a substantially spherical wave.

Now, in FIG. 2, since the electron beams CEB are two-dimensionally arranged and collide with the surface of the substrate SOB, the heat waves TW are also two-dimensionally arranged and serve as sources of ultrasonic waves. As previously mentioned,
In this example, all electrons! Since the i-source EBS is interrupted at the same time, the thermal waves TW and the ultrasonic waves generated by it all have the same phase.In this way, the ultrasonic waves generated with the same phase from the two-dimensionally arranged ultrasonic sources are , are superimposed to form a plane wave APW, which propagates through the substrate SO3 in the direction DP perpendicular to the surface of the substrate SUB.

FIG. 3 is a sectional view illustrating another example of the operation of the embodiment shown in FIG. As described above, the electron beam sources EBS can be driven independently. Therefore, by utilizing such features, the electron beam sources EBS I, EBS2, . These electron beams CEB collide with the substrate SUB as described above and become an ultrasonic generation source, but since there is a delay in the electron beam CEB generated from each electron beam rXEBs1, EBS2,..., the corresponding ultrasonic waves A phase delay occurs in the spherical waves of ultrasound generated from the source. Therefore, according to the principle of wave field synthesis, the phases of these spherical waves are superimposed to form a plane wave APW that propagates in the direction DS determined by the delay time.

In this case, the propagation direction OS of the ultrasonic wave APW generated within the substrate 5tlB is determined by the delay time of the intermittent electron beam CEB generated from the electron beam source EBS as described above. FIGS. 4(a) and 4(b) are explanatory diagrams of the relationship between such delay time and the propagation direction O5. Figure 4 (
In a), CEB 1 and CEB2 are intermittent electron beams, and Pl and P2 are electron beams CEB 1 on the surface of the substrate SUB.
, CEB2 is the irradiated point. The distance between points P1 and P2 is d, the angle between the Mi sound wave propagation direction I]S and the perpendicular to the surface of the substrate SO8 is θ, the speed of the ultrasonic wave APW is Va,
The wavelength is expressed as "in". FIG. 4(b) shows an electron beam CEB1. whose intermittent frequency is f. Points P1 and P2 of CEB2
This shows the case where the electron beams CEBI and CEB2 are interrupted at point P2 with a time delay behind PI.

Also, when the electron beam CEB2 reaches point P2, one point P
After 0 time τ, where the position in the substrate SUB where the ultrasonic wave APW generated at I reaches is 21', and the distance between points P1 and P1' is h, the ultrasonic wave APW is
)・The condition that the interruption of the electron beams CEBI and CEB2 at points P1 and P2 has the same effect on the ultrasonic wave APW in the substrate SUP is as follows.

τ/ (1/f)・Input=h Therefore, τ/(1/f) = h/In; d/(Input/sinθ), so using f・Input=Va, sinθ= ? Fist Va/d...
- (1) gives the propagation direction DS of the ultrasonic wave APW. To generate the ultrasonic wave APW in a desired direction within the substrate SUE, by modifying equation (1) and using the delay time τ obtained from τ=dasinθ/va...(2), the electron beam CEH It is sufficient to delay the occurrence of

FIG. 4 is a cross-sectional view taken along a plane defined by a perpendicular line drawn from the propagation direction OS of the ultrasonic wave APW to the surface of the substrate SUB.
It is not necessary that one axis of the two-dimensionally arranged electron beam source EBS lies within this plane. FIG. 5 is a plan view of the electron beam generating means EBH for explaining such a situation. In this Fig. 5, the white circle symbol is the two-dimensionally arranged electron beam source EBS.
represents. Substrate SO in propagation direction O3 of ultrasonic APW
The oblique shadow on B is taken as the X axis, and the direction orthogonal to it is taken as ym,
At this time, the origin of any electron beam source EBS i is assumed to be one arbitrarily selected electron beam source EBSO. Electron beam source EB
If the position of S i is expressed as (xi, yi), then the electron beam source E
The delay time of the electron beam source EBSi with respect to the BSO is 1, τi = xi* sinθ/Va
By setting (3), the ultrasonic wave APW generated in the substrate SOB has an oblique shadow on the surface of the substrate SOB in the traveling direction that coincides with the X-axis direction, and an angle formed with the perpendicular to the surface. becomes θ. Therefore, select the X axis appropriately, and
By setting the relative delay of so as to satisfy equation (3), it is possible to generate ultrasonic waves APW in any direction within the substrate SOB. Since such generation of ultrasonic APW does not use the piezoelectricity of the substrate SUB, it is possible to generate ultrasonic APW on any substrate such as a non-piezoelectric material.

In the above-mentioned embodiment, the generated ultrasonic wave APW was explained as a volume wave, but it is also possible to generate a surface acoustic wave by appropriately setting conditions.

That is, in equation (2) or equation (3), by setting the delay of each electron beam source EBS so that θ=90°, the spherical waves generated from each ultrasonic source are superimposed,
This can be used as a boundary condition for the generation of γ surface waves. In this case, as is clear from the description of FIG. 5, the surface acoustic waves can be propagated in any direction, and an unprecedented surface acoustic wave generating means can be provided.

In addition, in the explanation of the embodiment, a method of generating ultrasonic waves APW by intermittent electron beam CEB was exemplified, but ultrasonic waves APW
To generate W, it is sufficient that the electron beam CEB is intensity modulated, and for example, sinusoidal intensity modulation or pulse modulation with a duty ratio other than 1:1 can be used.

The two-dimensionally arranged electron beam sources EBS can be driven independently, and the examples have been described based on such conditions. However, by forming driving electrodes in a matrix and connecting them in common to each electron beam source EBS,
It is also possible to independently drive any one of the two-dimensionally arranged electron beam sources EBS, and such a driving method reduces the complexity of wiring and driving when there are a large number of electron beam sources EBS. Effective for reducing

FIG. 6 is a plan view illustrating such a driving method.

Common electrodes Xi, X2,..., Yl, Y2,... are connected to the electron beam source EBS in a matrix in the vertical and horizontal directions, and the electrodes x1, x2,... The control circuit C0NTl has electrodes Y1. Y2,... are connected to the control circuit C0NT2, for example, the control circuit C0
By selecting electrode x3 with NTl and selecting electrode Y4 with control circuit C0NT2, the electron beam source EBS34 in the third column and fourth row can be selected and driven.

It is also possible to apply such a driving method and duty ratio to the present invention by aiming at the generation of ultrasonic waves by appropriately selected pulse modulation of an electron beam. That is, the delay time τ between the electron beam sources EB and EB in the embodiment
By narrowing the pulse width for driving S, only one electron beam source EBS can be driven at the same time.

In the above-mentioned embodiments, the electron beam generator disclosed in the aforementioned Japanese Patent Publication No. 54-30274 was used; however, in the ultrasonic generation method of the present invention, the electron beam generator is independent. It is not an essential matter as long as it can be driven.

Therefore, the present invention has similar effects even when other known solid-state electron beam sources such as a pn junction negative work function type or a field emission type are used. Further, in the embodiment, the electron beam sources are arranged two-dimensionally at equal intervals, but it is clear that the present invention can be applied even if the electron beam sources are not evenly spaced.

[Effects of the Invention] As explained above, the ultrasonic generation method according to the present invention generates ultrasonic waves by irradiating a substrate with an electron beam generated from an electron beam source that is arranged two-dimensionally and can be individually controlled. Therefore, it is possible to generate ultrasonic waves using a non-piezoelectric substrate, and it is possible to generate volume waves or surface acoustic waves from the same generation source. Furthermore, since such sources do not have frequency characteristics depending on their shape, the frequency range from several KHz to several 100 M
) lz can be generated from the same source in an extremely wide frequency range, and one ultrasonic generating means can perform a wide variety of functions.

[Brief explanation of drawings]

The drawings show an embodiment of the ultrasonic generation method according to the present invention, and FIG. 1 is a schematic configuration diagram thereof, FIGS. 2 and 3 are sectional views for explaining the operation, and FIGS. 4 and 5. The figure is an explanatory diagram for generating ultrasonic waves in any direction, FIG. 6 is a drive circuit diagram of an electron beam source, and FIGS. 7 and 8 are schematic configuration diagrams of a conventional ultrasonic generation method. . The code EBH is a solid-state electron beam generator, EBS is an electron beam source,
S and SOB are substrates, MAC is an accelerating electrode, VAC+i accelerating voltage, C0NT is a control circuit, TW is a heat wave, AP is an ultrasonic wave, and CEB is an electron beam. Figure 1 Figure 2 Figure 3 Figure 4 <a) (b) Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Scope of Claims] 1. Consisting of an electron beam generating means in which a plurality of independently driven electron beam sources are two-dimensionally arranged and a substrate, intensity-modulated electrons are generated from each electron beam source of the electron beam generating means. An ultrasonic generation method characterized in that ultrasonic waves are generated by individually controlling and generating lines and irradiating the substrate with the ultrasonic waves. 2. The electron beam generating means has at least one xy orthogonal coordinate system on the same plane as the two-dimensional array of the electron beam sources, and the position of any electron beam source is (x, y) in the coordinate system. When expressed by The ultrasonic wave generation method according to claim 1, wherein the ultrasonic wave generation method is driven with a delay of approximately τ=x·sin θ/Va when the speed is set to .