Patent ID: 8574158

Claim:
An acoustic tomography method to improve the time of flight estimation, the method being performed with a tomography set up which comprises transmitters and receivers located around a volume to be scanned, said method comprising the steps of: sequentially triggering a set of N transmitters so as to generate a sequence of N acoustic waves which are passed completely through a volume being scanned; receiving each of said acoustic waves after transmission through said volume with a set of M receivers, which are called received signals; delaying by varying delays the N different said received signals that each receiver receives from the N different transmitters, and adding them together to form a new received signal, which is called transmit-beamformed signal for one of the M receivers, such that the transmit-beamformed signal is focused onto a focal point located at said one receiver, wherein said varying delays used to generate said transmit-beamformed signal from a transmitter to a receiver are computed as: (i) selecting a set of close by transmitters around said transmitter, which is called set i transmitters (ii) passing a reference signal from the set i transmitters completely through a reference medium which does not reflect the reference signal, to the receiver; (iii) computing the delays that need to be applied on said received signals at receiver from said set i transmitters based on difference between the time of flights of reference received signals at said receiver from said set i transmitters, and (iv) repeating both aforementioned steps, the selecting step and the computing step, for all N times M pairs of N transmitters and M receivers; delaying by varying delays the M different said transmit-beamformed signals for each receiver and adding them together at each receiver to form a new signal, which is called transmit-receive-beamformed signal for one of the N transmitters, such that the transmit-receive-beamformed signal is focused onto a focal point located at said one transmitter, wherein said varying delays used to generate transmit-receive-beamformed signal from a transmitter to a receiver is computed as: (i) selecting a set of close by receivers around said receiver, which are called set i receivers; (ii) passing reference signal from transmitted completely through a reference medium which does not reflect the reference signal, to the set j receivers; (iii) computing the delays that need to be applied on said transmit-beamformed signals for set j receivers from said transmitter based on the difference between the time of flights of reference signals from said transmitter to set j receivers; and (iv) repeating both aforementioned steps, the selecting step and the computing step, for all N times M pairs of N transmitters and M receivers; calculating the time of flight by determining the time difference between the transmit-receive-beamformed signal and a reference signal.