US3611200A

US3611200A - Ultrasonic delay line

Info

Publication number: US3611200A
Application number: US872913A
Authority: US
Inventors: Theodorus Bartholo Sliepenbeek; Manfred Franz Karl Gammel
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1968-11-09
Filing date: 1969-10-31
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05
Also published as: CH516260A; YU36248B; DE1953412A1; FR2022975A1; SE376522B; DE6941263U; GB1230036A; NL153046B; YU267569A; AT294918B; DE1953412B2; NL6816005A; BE741467A

Abstract

A thin flat ultrasonic delay line comprising a solid glass body in the shape of a parallelepiped with pentagonal top and bottom boundary surfaces extending perpendicular to the thickness dimension of the body and substantially parallel to the desired propagation path in the body for the ultrasonic wave energy. An input and an output transducer are mounted on first and second side surfaces of the body that extend perpendicular to said boundary surfaces. The body thickness is less than five times the wavelength of the wave energy. The transducers are polarized parallel to both the boundary surfaces and the first and second contact surfaces. Parts of the aforesaid boundary surfaces outside of the desired energy propagation path are arranged to attenuate wave energy impinging thereon.

Description

United States Patent [72] inventors Theodorus Bartholomeus Antonius Maria Sliepenbeelt; Manfred Franz Kari Gm'nmel, both of Emmasingel, Eindhoven, Netherlands [21] Appl. No. 872,913 [22] Filed Oct. 31, 1969 [45] Patented Oct. 5, 1971 [73] Assignee US. Philips Corporation New Yon-lit, NY. [32] Priority Nov. 9, 1968 3 3 Netherlands [31 l 681 6005 [54] ULTRASONIC DELAY LiNE 6 Ciaims, 2 Drawing Figs.

[52] ILLS. Cl 333/30 [51] int. C1 110311 9/30 [501 Fieid 01 Search 333/30 M, 30, 71

[5 6] References Cited UNITED STATES PATENTS 3,173,100 3/1965 White 333/30X 3,307,120 2/1967 Denton et a1. 333/30 Primary ExaminerHerman Karl Saalbach Assistant Examiner-Saxfield Chatson, ilr. Attorney-Frank R. Trifari ABSTRACT: A thin flat ultrasonic delay line comprising a solid glass body in the shape of a parallelepiped with pentagonal top and bottom boundary surfaces extending perpendicular to the thickness dimension of the body and substantially parallel to the desired propagation path in the body for the ultrasonic wave energy. An input and an output transducer are mounted on first and second side surfaces of the body that extend perpendicular to said boundary surfaces. The body thickness is less than five times the wavelength of the wave energy. The transducers are polarized parallel to both the boundary surfaces and the first and second contact surfaces. Parts of the aforesaid boundary surfaces outside of the desired energy propagation path are arranged to attenuate wave energy impinging thereon.

PATENTEDHBI 5m 3,611,200

1| III INVENTORS THEODORUS 8. AM. SLIEPENBEEK MANFRED F. .GAMMEL iwwa z ULTRASONIC DELAY LINE The present invention relates to an ultrasonic delay line comprising a solid body on which are provided one or more transducers for converting electrical energy into ultrasonic mechanical vibration energy, and vice versa, part of the body outside of the desired propagation path of the ultrasonic wave being designed as areas of attenuation for this wave. Generally, the material of the body is glass or another substance of slight temperature dependence so that the time interval between the reception of an electric input signal and the transmission of a corresponding electric output signal, during which time interval the input signal is converted into a mechanical vibration which in turn is reconverted into an electric signal, is virtually independent of the temperature. As a rule, the solid body is made comparatively thick in order to ensure that it has sufficient mechanical strength and to enable the contact surfaces for the provision of the transducers to be of sufficient size.

According to recent developments it has proved possible to simultaneously manufacture a large number of ultrasonic delay lines by starting from, for example, a prismatic glass body on one or two sides of which transducers are provided. Another side of the glass body is ground flat to enable it to serve as a reflecting surface for the mechanical vibration. The body is subsequently cut into thin slices by sawcuts extending at right angles to the said sides. The resulting parts can each be used as an ultrasonic delay line.

According to the invention this method of manufacturing ultrasonic delay lines permits of cheap large-scale manufacture, for which, however, several additional conditions have to be satisfied. The invention is characterized in that the body has a thickness which is less than five times the wavelength of the mechanical vibration, that the transducers are polarized in a direction parallel to the boundary surfaces of the body which extend at right angles to the direction of thickness, and in a direction parallel to their surfaces of contact with the solid, which surfaces are at right angles to the said boundary surfaces, and that suitably selected portions of these boundary surfaces which consequently extend substantially parallel to the direction of propagation of the ultrasonic wave propagating through the body, are designed as the said areas of attenuation for this wave.

The invention is based on the discovery that by described choice of the direction of polarization of the transducers, the said boundary surfaces act as mirrors for the ultrasonic vibration and hence give rise to comparatively little damping. However, owing to the natural spreading of the ultrasonic wave, for example, by diffraction phenomena, without further expedients it will be extremely difficult to obtain a reliably operating delay line since various undesirable reflections may occur. In addition, the ultrasonic wave may follow various undesirable paths so that no exactly defined delay time is obtained. It is known to provide damping material at the undesirable reflecting faces for the ultrasonic wave outside the desired path of this wave so that the wave is constrained within the desired path. Furthermore it has been proposed to attenuate the undesirable stray radiation by roughening the wall by means of a grinding or etching process, or to press corrugations in the delay-line body during the moulding process of the hot and still ductile glass. lf, now, according to a further discovery on which the invention is based, the thickness of the body is made smaller than five times the wavelength, it will be possible, although the said boundary surfaces extend substantially parallel to the direction of propagation of the ultrasonic wave, either to provide on the said boundary surfaces material which damps the ultrasonic wave or attenuates it in another manner or, for example, to etch parts of these boundary surfaces so as to ensure effective attenuation of the undesirable ultrasonic wave passing these parts. lf the body thickness is made greater this manner of damping is insufficiently effective. in practice, a thickness of, for example, 1 mm. is chosen. A smaller thickness also is permissible so long as sufficient mechanical strength is provided. For color television receivers in which a delay time of 64 us is desired, the wavelength is about 0.6 mm. Thus the thickness is smaller than twice the wavelength. The invention will be described more fully with reference to the accompanying drawing, in which:

FIG. 1 is a plan view of an ultrasonic delay line according to the invention, and

FIG. 2 is a side elevation thereof.

The delay line shown in Fig. l comprises a body ll composed of a suitably chosen material, for example, glass. The body 1 has the shape of a parallelopipedum with pentagonal base having

parallel sides

2 and 3, a side 4 at right angles thereto and

sides

5 and 6 at angles of about C. to the

sides

2 and 3 Transducers 7 and 8 are provided on

sides

5 and 6, respectively, so that the mechanical vibration produced by the transducer 7 is successively reflected at the

faces

2, 3, 4, 2 and 3 before striking the transducer 8. The thickness d of the body l is made smaller than five times, preferably smaller than twice, the wavelength of the ultrasonic mechanical vibration. The transducers 7 and 8 are polarized parallel to their

surfaces

5 and 6 of contact with the body 1, respectively, and also parallel to the upper and

lower boundary surfaces

9 and 10, respectively, of the body l, which latter surfaces may beformed by cutting the body from a larger body of glass. Further, damping material 1111, for example, silicone rubber, is provided in the form of a layer 1% mm. thick on the surfaces 9 and/or 10 in the areas shown by hatching in Fig. l. The said choice of the direction of polarization ensures that the surfaces 9 and 110, which in themselves have little damping power, act as mirrors for the ultrasonic mechanical vibration owing to the small thickness d used, so that the damping material lll effectively contributes to the fact that the ultrasonic wave emitted by the transducer 7 is compelled to follow the path shown towards the transducer 3. As a result, undesirable stray radiation and consequent undesirable blurring of the delay time to be produced are avoided.

What is claimed is:

ll. An ultrasonic delay line comprising, a solid body for transmitting ultrasonic wave energy along a desired path in the body, one or more transducers in contact with the body for converting electrical energy into ultrasonic mechanical vibration energy and vice versa, said body comprising first and second boundary surfaces which extend at right angles to the thickness dimension and substantially parallel to the desired direction of propagation of the ultrasonic wave in the body, said thickness dimension of the body being less than five times the wavelength of the mechanical vibration, said transducers being polarized parallel to the first and second boundary surfaces of the body and also parallel to their surfaces of contact with the body, said contact surfaces being at right angles to said boundary surfaces, and wave energy attenuation means located on suitably chosen parts of the boundary surfaces that lie outside of the desired path of the ultrasonic wave thereby to attenuate wave energy impinging thereon.

7. An ultrasonic delay device comprising a thin flat solid body for transmitting ultrasonic wave energy along a desired propagation path within the body, said body comprising first and second boundary surfaces extending normal to the thickness dimension of the body and substantially parallel to said desired energy propagation path and third and fourth side surfaces which extend normal to said boundary surfaces, said thickness dimension being less than five times the wavelength of the ultrasonic wave energy, an electromechanical input transducer in contact with said third surface and an electromechanical output transducer in contact with the fourth surface, said transducers being polarized parallel to the boundary surfaces and parallel to their respective contact surfaces. and wave energy attenuation means located on at least one of said boundary surfaces at given areas that lie outside of the desired energy propagation path thereby to effectively confine the wave energy to said desired path by dissipating the wave energy impinging thereon.

3. A delay device as claimed in claim 2 wherein said given areas of the boundary surface are roughened to constitute said wave energy attenuation means.

the seventh surface.

6. A delay device as claimed in claim 2 wherein said thickness dimension is chosen to be less than twice the wavelength of the ultrasonic wave energy.

Claims

1. An ultrasonic delay line comprising a solid body for transmitting ultrasonic wave energy along a desired path in the body, one or more transducers in contact with the body for converting electrical energy into ultrasonic mechanical vibration energy and vice versa, said body comprising first and second boundary surfaces which extend at right angles to the thickness dimension and substantially parallel to the desired direction of propagation of the ultrasonic wave in the body, said thickness dimension of the body being less than five times the wavelength of the mechanical vibration, said transducers being polarized parallel to the first and second boundary surfaces of the body and also parallel to their surfaces of contact with the body, said contact surfaces being at right angles to said boundary surfaces, and wave energy attenuation means located on suitably chosen parts of the boundary surfaces that lie outside of the desired path of the ultrasonic wave thereby to attenuate wave energy impinging thereon.

4. A delay device as claimed in claim 2 wherein said body further comprises fifth, sixth, and seventh side surfaces arranged normal to said boundary surfaces to reflect wave energy propagating along the desired path.

5. A delay device as claimed in claim 4 wherein said fifth and sixth surfaces are approximately parallel and normal to the seventh surface.

6. A delay device as claimed in claim 2 wherein said thickness dimension is chosen to be less than twice the wave-length of the ultrasonic wave energy.

7. An ultrasonic delay device comprising a thin flat solid body for transmitting ultrasonic wave energy along a desired propagation path within the body, said body comprising first and second boundary surfaces extending normal to the thickness dimension of the body and substantially parallel to said desired energy propagation path and third and fourth side surfaces which extend normal to said boundary surfaces, said thickness dimension being less than five times the wavelength of the ultrasonic wave energy, an electromechanical input transducer in contact with said third surface and an electromechanical output transducer in contact with the fourth surface, said transducers being polarized parallel to the boundary surfaces and parallel to their respective contact surfaces, and wave energy attenuation means located on at least one of said boundary surfaces at given areas that lie outside of the desired energy propagation path thereby to effectively confine the wave energy to said desired path by dissipating the wave energy impinging thereon.