US 8,619,494 B2 · Imaging apparatus and method

Abstract

A system (100) uses a pyroelectric membrane (122) and an ultrasound absorber (123) to measure the amount of ultrasonic energy received from a transmitter (105) through a sample (110). The thermal response of the pyroelectric membrane (122) is sensitive to ultrasound time-averaged intensity but is insensitive to the phase of the ultrasound. A waveform (200) shows rising (210), peak (220) and decaying (230) portions of a signal from the pyroelectric membrane (122) in response to on/off transitions of the transmitter (105). A system (300) uses a peak detector (333) to automatically turn the transmitter (105) on/off. A system (400) has background removal circuitry (444) to remove unwanted accelerometer-induced noise or electrical noise. A multi-element ultrasonic sensor (520) has cavities (555) so that a dummy sensor (521 b) can be used to compensate for unwanted accelerometer sensitivity of a sensor element (521 a). A sensor (620) has ultrasound absorbing (or reflective) regions (660) to compensate for unwanted accelerometer sensitivity. A system (900) has a low frequency path (909) sensitive to the pyroelectric effect, and a high frequency path (919) sensitive to the acoustic pressure amplitude, of a signal from a sensor (920). A sensor (1020) uses a pyroelectric material (1022) with poled regions (1099) separated by a non-poled region (1098).

Claims48

Dependent claims

Imaging apparatus for imaging the spatial distribution of the acoustic properties of a sample, the apparatus comprising:

at least one ultrasonic transmitter operable to generate an ultrasonic beam across an imaging area;
at least one ultrasonic receiver sensitive to intensity of an ultrasonic field generated by the transmitter or transmitters, the at least one ultrasonic receiver comprising:
an ultrasonic absorber;
and
a film which is divided into a plurality of separate elements comprising:
at least one pyroelectric ultrasonic sensing element in thermal communication with the ultrasonic absorber, which is sensitive to heating caused by the ultrasonic field and which has an accelerometer response;
and
at least one pyroelectric compensation element which is substantially insensitive to heating caused by the ultrasonic field and which has an accelerometer response substantially similar to that of the at least one pyroelectric ultrasonic sensing element;
wherein the at least one ultrasonic receiver is arranged to sense the ultrasonic field in a part of the imaging area;
and
signal processing circuitry operable to process a signal from the at least one ultrasonic receiver to derive therefrom an intensity measure across said imaging area, and thus to derive a spatial distribution of the acoustic properties of a sample in the field across said imaging area, wherein the signal processing circuitry is further operable to remove the signal from the at least one pyroelectric compensation element from the signal from the at least one pyroelectric ultrasonic sensing element so as to compensate for the accelerometer response of the at least one pyroelectric ultrasonic sensing element.

8 more elements

Dependencies are inferred from the claim text.

Imaging apparatus and method

Life of this patent

Imaging apparatus and method

Life of this patent

Abstract

Claims48