Method and apparatus for producing an acoustic field
The present invention concerns a method and apparatus for the modulation of an acoustic field for providing tactile sensations. A method of creating haptic feedback using ultrasound is provided. The method comprises the steps of generating a plurality of ultrasound waves with a common focal point using a phased array of ultrasound transducers, the common focal point being a haptic feedback point, and modulating the generation of the ultrasound waves using a waveform selected to produce little or no audible sound at the haptic feedback point.
1. A method comprising:
defining a three-dimensional virtual shape in a volume occupied by an acoustic field by:
i) producing the acoustic field from a transducer array having known relative positions and orientations;
ii) defining a plurality of control points wherein each of the plurality of control points have a known spatial relationship relative to the transducer array;
iii) assigning an amplitude to each of the plurality of control points;
iv) computing a matrix containing elements which represent, for each of the plurality of control points, the effect that producing a modeled acoustic field having the assigned amplitude with a particular phase at that control point has on the consequential amplitude and phase of the modeled acoustic field at the other control points;
v) calculating a plurality of eigenvectors of the matrix, each of the plurality of eigenvectors representing a set of relative phases and relative amplitudes of the modeled acoustic field at each of the plurality of control points; and
vi) selecting one of the set of phases and relative amplitudes of the modeled acoustic field and operating the transducer array to cause at least one transducer to output an acoustic wave having an initial amplitude and phase such that the phases and amplitudes of the resultant acoustic field at the control points correspond to the phases and relative amplitudes of the selected set of phases and relative amplitudes of the modeled acoustic field.
2. The method as in claim 1 , wherein a user defines the three-dimensional virtual shape.
3. The method as in claim 1 , wherein an automated process defines the three-dimensional virtual shape.
4. The method of claim 1 wherein each of the plurality of eigenvectors represents scaling factors and comprise a first set of the plurality of eigenvectors and a second set of the plurality of eigenvectors,
wherein the first set of the plurality of eigenvectors represent relatively high scaling factors when compared with the second set of the plurality of eigenvectors,
wherein the second set of the of the plurality of eigenvectors represent relatively low scaling factors when compared with the first set of the plurality of eigenvectors,
and further comprising selecting a set of phases and relative amplitudes with an eigenvalue corresponding to the first set of the plurality of eigenvectors.
5. The method of claim 1 , wherein the effect of producing the assigned amplitude at one of the control points based on the amplitude and phases at each of the other control points is computed using a look-up function which defines how the amplitude and phase of the acoustic waves varies spatially due to attenuation and propagation.
6. The method of claim 1 further comprising;
a regularization step in which errors are introduced into an initial amplitude and phase output.
7. The method of claim 6 wherein the regularization step uses a weighted Tikhonov regularization.
8. The method of claim 1 , wherein the power output by the transducer array is scaled such that the transducer outputting the highest of the initial amplitudes operates at substantially full power.
9. The method of claim 1 , wherein the acoustic waves comprise ultrasound waves.
10. The method of claim 1 , wherein the acoustic waves are modulated at a frequency between 0.1 Hz to 500 Hz.
11. The method of claim 1 , wherein the plurality of control points comprise a first group of control points and a second group of control points, wherein the acoustic field has a relatively high amplitude relative to the amplitude of the acoustic field at the second group of control points, wherein the acoustic field has a relatively low amplitude relative to the amplitude of the acoustic field at the first group of control points, and wherein the first group of control points are adjacent to the second group of control points so that a gradient in amplitude of the acoustic field is produced.
12. The method of claim 9 , wherein the plurality of control points comprise a group of at least one low amplitude control points may be supported by at least one high amplitude control point to define a pocket that can hold an object at the group of at least one low amplitude control points.
13. The method of claim 9 , wherein the positions of at least one of the control points are chosen to define parts of the virtual three-dimensional shape within the volume to be occupied by the acoustic field.
14. The method of claim 11 , wherein the at least one of the control points are positioned in the region of points where an object intersects the virtual shape.
15. A method comprising:
selecting a plurality of control points to define at least one part of a three-dimensional virtual shape in a volume occupied by an acoustic field by:
i) producing the acoustic field from a transducer array having known relative positions and orientations;
ii) defining the plurality of control points wherein each of the plurality of control points have a known spatial relationship relative to the transducer array;
iii) assigning an amplitude to each of the plurality of control points;
iv) computing a matrix containing elements which represent, for each of the plurality of control points, the effect that producing a modeled acoustic field having the assigned amplitude with a particular phase at that control point has on the consequential amplitude and phase of the modeled acoustic field at the other control points;
v) calculating a plurality of eigenvectors of the matrix, each of the plurality of eigenvectors representing a set of relative phases and relative amplitudes of the modeled acoustic field at each of the plurality of control points; and
vi) selecting one of the set of phases and relative amplitudes of the modeled acoustic field and operating the transducer array to cause at least one transducer to output an acoustic wave having an initial amplitude and phase such that the phases and amplitudes of the resultant acoustic field at the control points correspond to the phases and relative amplitudes of the selected set of phases and relative amplitudes of the modeled acoustic field.
16. The method of claim 15 , wherein the plurality of control points lie on an edge of the three-dimensional virtual shape.
17. The method of claim 15 , wherein the plurality of control points lie adjacent to an edge of the three-dimensional virtual shape.
18. The method of claim 15 , wherein the plurality of control points lie adjacent to an edge of the three-dimensional virtual shape.
19. The method of claim 15 , wherein the plurality of control points are defined at parts of the three-dimensional virtual shape when the plurality of control points are intersected by a hand.
20. The method of claim 15 wherein each of the plurality of eigenvectors represents scaling factors and comprise a first set of the plurality of eigenvectors and a second set of the plurality of eigenvectors;
wherein the first set of the plurality of eigenvectors represent relatively high scaling factors when compared with the second set of the plurality of eigenvectors;
wherein the second set of the of the plurality of eigenvectors represent relatively low scaling factors when compared with the first set of the plurality of eigenvectors;
and further comprising selecting a set of phases and relative amplitudes with an eigenvalue corresponding to the first set of the plurality of eigenvectors.
21. The method of claim 15 , wherein the effect of producing the assigned amplitude at one of the control points based on the amplitude and phases at each of the other control points is computed using a look-up function which defines how the amplitude and phase of the acoustic waves varies spatially due to attenuation and propagation.
22. The method of claim 15 , further comprising:
a regularization step in which errors are introduced into an initial amplitude and phase output.
23. The method of claim 22 , wherein the regularization step uses a weighted Tikhonov regularization.
24. The method of claim 15 , wherein the power output by the transducer array is scaled such that the transducer outputting the highest of the initial amplitudes operates at substantially full power.
25. The method of claim 15 , wherein the acoustic waves comprise ultrasound waves.
26. The method of claim 15 , wherein the acoustic waves are modulated at a frequency between 0.1 Hz to 500 Hz.
27. The method of claim 15 , wherein the plurality of control points comprise a first group of control points and a second group of control points, wherein the acoustic field has a relatively high amplitude relative to the amplitude of the acoustic field at the second group of control points, wherein the acoustic field has a relatively low amplitude relative to the amplitude of the acoustic field at the first group of control points, and wherein the first group of control points are adjacent to the second group of control points so that a gradient in amplitude of the acoustic field is produced.
28. The method of claim 15 , wherein the plurality of control points comprise a group of at least one low amplitude control points may be supported by at least one high amplitude control point to define a pocket that can hold an object at the group of at least one low amplitude control points.
29. The method of claim 15 , wherein the positions of at least one of the control points are chosen to define parts of the virtual three-dimensional shape within the volume to be occupied by the acoustic field.
30. The method of claim 15 , wherein the at least one of the control points are positioned in the region of points where an object intersects the virtual shape.