WO2001057482A1 - Measuring device for ultrasound sources - Google Patents
Measuring device for ultrasound sources Download PDFInfo
- Publication number
- WO2001057482A1 WO2001057482A1 PCT/US2000/002549 US0002549W WO0157482A1 WO 2001057482 A1 WO2001057482 A1 WO 2001057482A1 US 0002549 W US0002549 W US 0002549W WO 0157482 A1 WO0157482 A1 WO 0157482A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- acousto
- ultrasound
- subsystem
- enclosure
- liquid crystal
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/002—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means for representing acoustic field distribution
Definitions
- the device for measuring the intensity of an ultrasound beam disclosed
- the device is used with a source of ultrasound energy radiations, and one
- the device comprises an acousto-optic subsystem with a liquid crystal
- acousto-optic subsystem is illuminated by unpolarized light and traversed by
- optic subsystem is illuminated by unpolarized light and not traversed by
- ultrasound energy radiations An imaging subsystem which provides images
- FIG. 1 shows the device above an ultrasound source.
- FIG. 2 shows a cross section of the device coupled to the ultrasound
- FIG. 3 shows a cross section of the acousto-optic subsystem and shows
- the device 10 is shown in FIG. 1 above an ultrasound source 50.
- ultrasound source comprises a container 51 with an ultrasound transducer 52
- transducer traverse a coupling medium 54 and exit the container via the exit
- Ultrasound sources are produced independently and can have many forms
- the acousto-optic subsystem 20 comprises an ultrasound transparent
- the liquid crystal medium provides measurable contrast between bright
- the acousto-optic subsystem is illuminated by unpolarized light and traversed by ultrasound energy radiations.
- the dark areas occur where the
- acousto-optic subsystem is illuminated by unpolarized light and not traversed
- the liquid crystal medium was unexpected and the causes are not yet clear.
- this coating also serves as proximal the liquid crystal medium.
- this coating also serves as proximal the liquid crystal medium.
- this coating also makes the input plate, light reflecting, and
- Electrical leads 41 are connected to the opposing plate where it is
- the leads 41 are also connected to a source of electric potential 42 to comprise
- the opposing plate are glass 110 micrometers thick and 5 centimeters by 5 centimeters in long dimensions.
- the input plate has a ⁇ 500 Angstrom vacuum-
- the opposing plate has a ⁇ 500
- An imaging subsystem comprises a light source 31 - preferably a ring
- an imaging device 32 - preferably a charge coupled device - which views the
- the imaging subsystem records images which have measurable contrast
- intensity of light from the liquid crystal medium depends on the angle of
- the viewing angle could not be optimized.
- acousto-optic subsystem were illuminated by light via a first polarizer. Contrast between the bright areas and dark areas could also be imaged if the imaging
- ultrasound energy radiations traversing the acousto-optic subsystem is equal to
- V which returns a bright area to the same brightness as a dark area
- the enclosure 11 is filled with a coupling medium 14 which prevents
- Ultrasound sources are produced independently of the device and can
- the device enclosure can have various forms in order to
- the ultra sound transducer can be variable in order to obtain a series of images at
- the imaging device could be directly coupled to the acousto-optic subsystem - so long as the imaging
- subsystem can record the contrast between bright areas and dark areas of the
- the acousto-optic subsystem can be viewed by an imaging subsystem via
- An acousto-optic subsystem can have various forms so long as a
- liquid crystal medium provides contrast between bright areas and dark areas
Abstract
A measuring device for ultrasound sources (10) comprising enclosure (11) filled with coupling medium (14) which prevents reflections of ultrasound energy radiations at the interface of an opposing plate, light source (31) and ultrasound source (50) further comprising container (51), ultrasound transducer (52), ultrasound transparent exit window (53), and coupling medium (54), wherein ultrasound energy radiations are changed by varying the properties of transducer (52).
Description
TITLE OF THE INVENTION
Measuring Device for Ultrasound Sources
BACKGROUND OF THE INVENTION
The device uses a new acousto-optic effect to provide three dimensional
profiles of acoustic beams from ultrasound sources and to measure the
intensities of the beams in planes along the beams.
As ultrasound devices come to be used more frequently in various
therapies, the outstanding need to find means for measuring ultrasound sources
becomes more critical. This problem is solved by the discovery of a new
acousto-optic effect disclosed here, which can be used to obtain a three
dimensional profile of a beam from an ultrasound source and obtain a measure
of the intensity of the beam in planes along the beam.
The device for measuring the intensity of an ultrasound beam disclosed
by Sandhu in U. S. Patent 4,492,107, which uses crossed polarizers to detect a
birefringence effect, is not useful for profiling an ultrasound beam. The device
shown here uses a new effect to measure the intensity of an ultrasound beam
and provides a three dimensional profile of the beam.
SUMMARY OF THE INVENTION
The device is used with a source of ultrasound energy radiations, and one
form of the device comprises an acousto-optic subsystem with a liquid crystal
medium which provides measurable contrast between bright areas and dark
areas of the acousto-optic subsystem, the bright areas occuring where the
acousto-optic subsystem is illuminated by unpolarized light and traversed by
ultrasound energy radiations, and the dark areas occuring where the acousto-
optic subsystem is illuminated by unpolarized light and not traversed by
ultrasound energy radiations; an imaging subsystem which provides images
showing the contrast between the bright and dark areas.
Other forms and objects of the invention will be comprehended in the
drawings and detailed description, which will make further equivalent forms
and objects obvious hereafter to persons skilled in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the device above an ultrasound source.
FIG. 2 shows a cross section of the device coupled to the ultrasound
source.
FIG. 3 shows a cross section of the acousto-optic subsystem and shows
schematically an electric field subsystem coupled to the acousto-optic
subsystem.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The device 10 is shown in FIG. 1 above an ultrasound source 50. The
ultrasound source comprises a container 51 with an ultrasound transducer 52
within the container and with an ultrasound transparent exit window 53 through
the container. Ultrasound energy radiations produced by the ultrasound
transducer traverse a coupling medium 54 and exit the container via the exit
window. The position of the focus of the ultrasound energy radiations is
changed by varying properties of the transducer 52.
Ultrasound sources are produced independently and can have many forms
so long as ultrasound energy radiations exiting an exit window traverse an
enclosure coupling medium 25 and enter the acousto-optic subsystem 20 of the
device.
The acousto-optic subsystem 20 comprises an ultrasound transparent
input plate 22 which is a window into an enclosure 11, a light transparent
opposing plate 21 within the enclosure, perimeter spacers 24 between the input
plate and the opposing plate forming a closed volume between the input plate
and the opposing plate, and a liquid crystal medium 23 filling the sealed
volume.
The liquid crystal medium provides measurable contrast between bright
areas and dark areas of the acousto-optic subsystem. The bright areas occur
where the acousto-optic subsystem is illuminated by unpolarized light and
traversed by ultrasound energy radiations. The dark areas occur where the
acousto-optic subsystem is illuminated by unpolarized light and not traversed
by ultrasound energy radiations. The discovery by the inventors of this effect in
the liquid crystal medium was unexpected and the causes are not yet clear.
On the opposing plate 21 proximal the liquid crystal medium 23 there is a
viewing coating 26 which makes the opposing plate electrically conducting
proximal the liquid crystal medium. In the preferred form this coating also
makes the opposing plate light transparent, and ultrasound transparent.
On the input plate 22 there is an input coating 27 which makes the input
plate electrically conducting proximal the liquid crystal medium. In the
preferred form this coating also makes the input plate, light reflecting, and
ultrasound transparent.
Electrical leads 41 are connected to the opposing plate where it is
electrically conducting and to the input plate where it is electrically conducting.
The leads 41 are also connected to a source of electric potential 42 to comprise
an electric field subsystem coupled to the liquid crystal medium.
The choice of parameters for the acousto-optic subsystem depends on the
parameters of the ultrasound source, which can vary. For a 40 watt, 1.65
megahertz ultrasound source focused to a 3 millimeter diameter spot the
following acousto-optic subsystem parameters work well. The input plate and
the opposing plate are glass 110 micrometers thick and 5 centimeters by 5
centimeters in long dimensions. The input plate has a <500 Angstrom vacuum-
deposited aluminum input coating, and the opposing plate has a < 500
Angstrom indium-tin oxide viewing coating. The gap between the plates is 1.78
millimeters and is filled with a conventional liquid crystal medium: 4-cyano-40
n-pentyl biphenyl. Other dimensions, coatings, and liquid crystal media also
work well. As the effect is new, the range of dimensions, coatings, and liquid
crystal media which can be used has not been deteπnined, and there is no reason
to suspect that the range of parameters is different than the range known in the
art of acousto-optic imaging.
An imaging subsystem comprises a light source 31 - preferably a ring
light around the enclosure - which illuminates the acousto-optic subsystem, and
an imaging device 32 - preferably a charge coupled device - which views the
acousto-optic subsystem via a light transparent viewing window 12 through the
enclosure and via the opposing plate, and outputs a signal via leads 33 to an
information processing system and display device, not shown.
The imaging subsystem records images which have measurable contrast
between the bright areas and the dark areas of the acousto-optic subsystem. In
the preferred form, using a charge coupled device outputting a signal to a
computer, there are ways well known in the art to measure the contrast between
the bright areas and the dark areas.
Contrast boundaries in images recorded by the imaging subsystem show
boundaries of the ultrasound energy radiations traversing the acousto-optic
subsystem. A three dimensional profile of the ultrasound energy radiations
along the normal axis 101 can be obtained from a series of images of the
radiations taken for various positions of the focus of the radiations along the
normal axis.
The phenomenon relied on here is not the normal birefringence
phenomena which is imaged using crossed polarizers. In that phenomenon the
intensity of light from the liquid crystal medium depends on the angle of
viewing and could not be used to see the boundaries of the ultrasound energy
radiations because there would be no image seen along the normal axis 101, and
the viewing angle could not be optimized.
The phenomenon relied on here has not been reported previously.
Crossed polarizers are not used. When the acousto-optic subsystem is
illuminated with unpolarized light and viewed by the imaging subsystem along
the axis normal to the acousto-optic subsystem, there is measurable contrast
between bright areas of the acousto-optic subsystem through which ultrasound
energy radiations pass and dark areas are not traversed by ultrasound energy
radiations.
There would also be contrast between bright areas and dark areas if
acousto-optic subsystem were illuminated by light via a first polarizer. Contrast
between the bright areas and dark areas could also be imaged if the imaging
subsystem viewed the acousto-optic subsystem via a second polarizer.
However, if the planes of polarization of the first and second polarizers
were perpendicular, then a bright area would not be imaged along the axis 101
when the acousto-optic subsystem is illuminated and ultrasound energy
radiations traverse the acousto-optic subsystem along that axis; and the imaged
contrast between bright areas and dark areas would depend on the angles light
from the acousto-optic subsystem is incident on the imaging subsystem.
The distmguishing feature of the new phenomenon disclosed here is that
bright areas do occur where the acousto-optic subsystem is illuminated by
unpolarized light and traversed by ultrasound energy radiations, and dark areas
do occur where the acousto-optic subsystem is illuminated by unpolarized light
and is not traversed by ultrasound energy radiations.
Also, in the phenomenon relied on here a bright area can be returned to
the same brightness as a dark area by an electric potential applied by the electric
field subsystem. It has been empirically determined that the intensity, I, of the
ultrasound energy radiations traversing the acousto-optic subsystem is equal to
a first constant, 1(0), plus a second constant, C, times the square of the electric
potential, V, which returns a bright area to the same brightness as a dark area: I
= 1(0) + C V . An alternating current potential is preferred to avoid flow of the
liquid crystal molecules in the liquid crystal medium.
The enclosure 11 is filled with a coupling medium 14 which prevents
reflection of ultrasound energy radiations at the interface of the opposing plate
and the coupling medium. In order to minimize reverberations from the
enclosure by which ultrasound energy could reenter the acousto-optic
subsystem, ultrasound energy radiations traversing the acousto-optic subsystem
along paths about an axis 101 normal to the input plate - which would
reverberate from the viewing window - are reflected by an ultrasound reflector
13 to flow about an axis 101' to an ultrasound absorbing inside surface 15 of the
enclosure. To the same end, ultrasound energy radiations along other paths -
such as axis 102 at one extreme of the ultrasound energy radiations and axis 103
at the other extreme - are incident on the ultrasound absorbing inside surface 15
of the enclosure.
Ultrasound sources are produced independently of the device and can
have many forms. The device enclosure can have various forms in order to
match the forms of ultrasound sources and to match the form of the imaging
subsystem. For example, the distance between the acousto-optic subsystem and
the ultra sound transducer can be variable in order to obtain a series of images at
points along the beam of ultrasound energy without changing properties of the
ultrasound source.
The source of illumination and the image recording device in the imaging
subsystem can have various forms - for example, the imaging device could be
directly coupled to the acousto-optic subsystem - so long as the imaging
subsystem can record the contrast between bright areas and dark areas of the
acousto-optic subsystem.
The acousto-optic subsystem can be viewed by an imaging subsystem via
the input plate using a mirror and with appropriate changes in the coatings on
the plates. An acousto-optic subsystem can have various forms so long as a
liquid crystal medium provides contrast between bright areas and dark areas
when the bright areas are illuminated by unpolarized light and traversed by
ultrasound energy radiations and dark areas are illuminated by unpolarized light
and not traversed by ultrasound energy radiations.
Other equivalent forms for the enclosure, the acousto-optic subsystem,
the imaging subsystem, and the electric field subsystem and other equivalent
ways to couple the acousto-optic subsystem to an ultrasound source and to
configure the electric field subsystem and the imaging subsystem relative to the
acousto-optic subsystem will be obvious hereafter to persons skilled in the art.
Therefore this invention is not limited to the particular examples shown and
described here.
Claims
1. A measuring device used in combination with an ultrasound source,
the device comprising:
an acousto-optic subsystem, the acousto-optic subsystem comprising a
liquid crystal medium, the liquid crystal medium providing
measurable contrast between bright areas and dark areas of the
acousto-optic subsystem, the bright areas occurring where the
acousto-optic subsystem is illuminated by unpolarized light and
traversed by the ultrasound energy radiations, and the dark areas
occurring where the acousto-optic subsystem is illuminated by the
unpolarized light and not traversed by the ultrasound energy
radiations; and
an imaging subsystem comprising:
a light source illuminating the acousto-optic subsystem;
an imaging device imaging the bright areas and the dark areas of
the acousto-optic subsystem;
2. The device of claim 1 further comprising an electric field subsystem
coupling an electric field to the liquid crystal medium to null the contrast
between the bright areas and the dark areas.
3. The device of claim 1 further comprising:
an input plate traversed by ultrasound energy radiations produced by the
ultrasound source; and
an opposing plate with perimeter spacers between the opposing plate and
the input plate forming an enclosed volume between the input plate
and the opposing plate; the enclosed volume containing the liquid
crystal medium.
4. The device of claim 3 further comprising an electric field subsystem
coupling an electric field to the liquid crystal medium to null the contrast
between the bright areas and the dark areas.
5. The device of claim 4 wherein the opposing plate is electrically
conducting proximal the liquid crystal medium, the input plate is electrically
conducting proximal the liquid crystal medium, and the electric field is coupled
to the liquid crystal medium via electric leads attached to the opposing plate
where it is electrically conducting and attached to the input plate where it is
electrically conducting.
6. The device of claim 5 wherein the input plate is a window into an
enclosure, the enclosure being filled with an ultrasound coupling medium, the
enclosure having an ultrasound absorbing inner surface, and the enclosure
having a viewing window into the enclosure with the imaging device imaging
the acousto-optic subsystem via the viewing window and the coupling medium.
7 The device of claim 6 further comprising an ultrasound reflector
reflecting ultrasound which would be incident on the viewing window toward
the ultrasound absorbing inner surface.
8. A method for measuring an ultrasound source, the method comprising:
coupling the ultrasound source to an acousto-optic subsystem, the
acousto-optic subsystem comprising a liquid crystal medium, the
liquid crystal medium providing measurable contrast between
bright areas and dark areas of the acousto-optic subsystem, the
bright areas occurring where the acousto-optic subsystem is
illuminated by unpolarized light and traversed by the ultrasound
energy radiations, and the dark areas occurring where the acousto-
optic subsystem is illuminated by the unpolarized light and not
traversed by the ultrasound energy radiations;
illuminating the acousto-optic subsystem; and
imaging the acousto-optic subsystem.
9 The method of claim 8 further comprising the step of nulling the
contrast between the bright areas and the dark areas by applying an electric field
coupled to the liquid crystal medium.
10. A measuring device used in combination with an ultrasound source,
the ultrasound device comprising:
an acousto-optic subsystem, the acousto-optic subsystem comprising:
an input plate proximal the ultrasound source, the input plate being
a window into an enclosure, the input plate being traversed
by ultrasound energy radiations produced by the ultrasound
source via an enclosure coupling medium, the input plate
being electrically conducting proximal the enclosure;
a opposing plate, the opposing plate being connected to the input
plate by perimeter spacers between the opposing plate and
the input plate to forms an enclosed volume between the
input plate and the opposing plate, the opposing plate being
electrically conducting proximal the enclosed volume, the
opposing plate being within the enclosure, the enclosure
having an ultrasound absorbing inner surface, and the
enclosure having an ultrasound reflector reflecting to the
inner surface ulfrasound energy radiations which exit the
opposing plate along a normal axis;
a liquid crystal medium contained in the enclosed volume, the
liquid crystal medium providing measurable contrast
between bright areas and dark areas of the acousto-optic subsystem, the bright areas occurring where the acousto-
optic subsystem is illuminated by unpolarized light and
traversed by the ultrasound energy radiations, and the dark
areas occurring where the acousto-optic subsystem is
illuminated by the unpolarized light and not traversed by the
ultrasound energy radiations;
an imaging subsystem comprising:
a light source illuminating the acousto-optic subsystem, the light
source being a ring light outside the enclosure;
an imaging device imaging the bright areas and the dark areas of
the acousto-optic subsystem, the imaging device being a
charge coupled device outputting a signal to a computer; the
imaging device viewing the opposing plate along the normal
axis via a viewing window through the enclosure, and via a
coupling medium in the enclosure;
an electric field subsystem comprising a variable potential, alternating
current source of electric potential with the electric potential being
applied across the liquid crystal medium via electric leads attached
to the input plate where the input plate is electrically conducting
and attached to the opposing plate where the opposing plate is electrically conducting, the contrast between the bright areas and
the dark areas being nulled by a value of the electric potential.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2000/002549 WO2001057482A1 (en) | 2000-02-01 | 2000-02-01 | Measuring device for ultrasound sources |
| AU2000227499A AU2000227499A1 (en) | 2000-02-01 | 2000-02-01 | Measuring device for ultrasound sources |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US2000/002549 WO2001057482A1 (en) | 2000-02-01 | 2000-02-01 | Measuring device for ultrasound sources |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2001057482A1 true WO2001057482A1 (en) | 2001-08-09 |
Family
ID=21741024
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US2000/002549 WO2001057482A1 (en) | 2000-02-01 | 2000-02-01 | Measuring device for ultrasound sources |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU2000227499A1 (en) |
| WO (1) | WO2001057482A1 (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5886265A (en) * | 1996-02-22 | 1999-03-23 | Gec Alsthom T & D Balteau | Optical vibration sensor |
| US5912997A (en) * | 1994-09-09 | 1999-06-15 | Gemfire Corporation | Frequency converter optical source for switched waveguide |
-
2000
- 2000-02-01 AU AU2000227499A patent/AU2000227499A1/en not_active Abandoned
- 2000-02-01 WO PCT/US2000/002549 patent/WO2001057482A1/en active Application Filing
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5912997A (en) * | 1994-09-09 | 1999-06-15 | Gemfire Corporation | Frequency converter optical source for switched waveguide |
| US5886265A (en) * | 1996-02-22 | 1999-03-23 | Gec Alsthom T & D Balteau | Optical vibration sensor |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2000227499A1 (en) | 2001-08-14 |
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