Apparatus and method for characterization of a ductile membrane, surface and sub-surface properties
An ultrasound signal processor uses an excitation generator to cause displacement of a membrane or surface while a series of ultrasound pulses are applied to the membrane or surface. Phase differences between a transmitted signal and received signal are examined to determine the movement of the membrane or surface in response to the applied excitation. An examination of the phase response of the membrane or surface provides a determination as to whether the fluid type behind the membrane or surface is one of: no fluid, serum fluid, or purulent fluid.
1 . A method for non-contact measurement of an elastic surface, the method comprising:
(a) providing a non-contact force to a surface or a volume of material adjacent to the surface to be characterized using an excitation generator, wherein the non-contact force comprises a step or impulse pressure; and
(b) in response to the non-contact force, forming a displacement measurement, the displacement measurement comprising:
(i) directing a transmit burst of ultrasound energy from a transducer to the surface or the volume of material adjacent to the surface;
(ii) receiving a reflected ultrasound energy from the surface or the volume of material adjacent to the surface with the transducer;
(iii) setting a range gate for a first region of the reflected ultrasound energy; and
(iv) distinguishing a movement or displacement of the first region from a movement or displacement of a second region based at least in part on the range gate.
2 . The method of claim 1 , wherein the transmit burst has a spatial extent which matches a region of the surface or the volume of material adjacent to the surface which is moving in a same direction as the transmit burst.
3 . The method of claim 1 , wherein the transmit burst comprises a transmitted ultrasound energy; and wherein setting the range gate is based at least in part on at least one of: a frequency of the transmitted ultrasound energy, a propagation velocity of the transmitted ultrasound energy, or a number of cycles of the transmitted ultrasound energy.
4 . The method of claim 1 , further comprising, when the surface or the volume of material adjacent to the surface moves out of a range of a first range gate associated with a first depth to a second depth, adaptively forming a displacement measurement based at least in part on a second displacement measurement comprising a second range gate associated with the second depth.
5 . The method of claim 1 , wherein the method further comprises: comparing a phase of a transmitted ultrasound energy of the transmit burst to the reflected ultrasound energy to form a displacement estimate for the surface or the volume of material adjacent to the surface; and forming an estimate of an elasticity of the surface or a viscosity of the volume of material adjacent to the surface based at least in part on a series of displacement measurements.
6 . The method of claim 1 , wherein providing the non-contact force comprises directing a puff of air to the surface or to the volume of material adjacent to the surface.
7 . The method of claim 1 , wherein the transducer comprises a capacitive micromachined ultrasonic transducer (cMUT) or a piezoelectric transducer.
8 . The method of claim 1 , wherein the surface comprises a membrane over a fluid.
9 . The method of claim 1 , wherein the surface comprises a solid or semi-solid food item.
10 . The method of claim 4 , wherein the displacement measurement for the surface or the volume of material adjacent to the surface is based at least in part on a reflected Doppler ultrasound signal.
11 . A method for non-contact measurement of an elastic surface, the method comprising:
(a) providing a non-contact force to a surface or a volume of material adjacent to the surface to be characterized using an excitation generator, wherein the non-contact force comprises a step or impulse pressure;
(b) in response to the non-contact force, forming a displacement measurement;
(c) forming an estimate of elasticity based at least in part on the displacement measurement; and
(d) characterizing the surface or the volume of material adjacent to the surface based at least in part on the estimate of elasticity, wherein the characterizing is based at least in part on a hysteresis response of the surface or the volume of material adjacent to the surface.
12 . The method of claim 11 , wherein (b) further comprises
(i) directing a transmitted ultrasound energy from a transducer to the surface or the volume of material adjacent to the surface;
(ii) receiving a reflected ultrasound energy from the surface or the volume of material adjacent to the surface with the transducer; and
(iii) comparing a phase of the transmitted ultrasound energy to the reflected ultrasound energy to form a displacement estimate for the surface or the volume of material adjacent to the surface.
13 . The method of claim 11 , wherein characterizing the surface or the volume of material adjacent to the surface based at least in part on the hysteresis response is based at least in part on an offset in the displacement measurement from another displacement measurement.
14 . The method of claim 13 , wherein the offset comprises a first displacement response in a first direction and a second displacement response in a second direction, wherein the first direction is opposite to the second direction, and wherein the first displacement response is similar to the second displacement response after the first displacement response travels a displacement distance.
15 . The method of claim 11 , further comprising characterizing the surface or the volume of material adjacent to the surface based at least in part on a series of hysteresis responses of a series of displacement estimates.
16 . The method of claim 15 , further comprising forming the series of hysteresis responses based at least in part on a linear behavior of each hysteresis response of the series of hysteresis responses.
17 . The method of claim 11 , wherein the volume of material adjacent to the surface comprises a fluid having an elasticity.
18 . The method of claim 11 , wherein providing the non-contact force to the surface or to the volume of material adjacent to the surface comprises directing a puff of air to the surface or to the volume of material adjacent to the surface.
19 . The method of claim 12 , wherein the transducer comprises a capacitive micromachined ultrasonic transducer (cMUT) or a piezoelectric transducer.
20 . The method of claim 11 , wherein the surface comprises a solid or semi-solid food item.
21 . The method of claim 12 , wherein the displacement estimate for the surface or the volume of material adjacent to the surface is based at least in part on a reflected Doppler ultrasound signal.