Device and method for frequency-domain thermoacoustic sensing

A method for thermoacoustic sensing, the method comprising:

• a) continuously emitting electromagnetic or particle radiation, respectively, exhibiting a first modulation simultaneously comprising at least two modulation components, wherein each modulation component is a periodic modulation at a distinct frequency, towards a target so that the at least two modulation components at the distinct frequencies impinge upon the target at the same time, wherein the first modulation corresponds to a superposition of the at least two modulation components such that the at least two modulation components of the first modulation are concurrently emitted, whereby acoustic waves are continuously generated in the target, the acoustic waves exhibiting a second modulation, the second modulation simultaneously comprising acoustic wave components at the distinct frequencies of the at least two modulation components or at harmonic frequencies of the distinct frequencies of the at least two modulation components,
• b) simultaneously detecting the acoustic waves exhibiting the second modulation while the electromagnetic or particle radiation exhibiting the first modulation is continuously emitted towards the target, and
• c) determining thermoacoustic values of at least one of an amplitude and a phase of each of the acoustic wave components at the distinct frequencies of the at least two modulation components or at the harmonic frequencies of the distinct frequencies of the at least two modulation components.

A device for thermoacoustic sensing, the device comprising:

• a) an irradiation unit comprising an electromagnetic radiation source or a particle beam source, the irradiation unit being configured to:
• generate electromagnetic or particle radiation, respectively,
• modulate an intensity or frequency of the electromagnetic or particle radiation, respectively, with a first modulation, the first modulation simultaneously comprising at least two modulation components at distinct frequencies, and
• continuously emit the modulated electromagnetic or particle radiation, respectively, towards a target so that the at least two modulation components at the distinct frequencies impinge upon the target at the same time, wherein each modulation component is a periodic modulation at a distinct frequency, wherein the at least two modulation components of the first modulation are concurrently emitted and the first modulation corresponds to a superimposition of the at least two modulation components, whereby acoustic waves are continuously generated in the target, the acoustic waves exhibiting a second modulation, the second modulation simultaneously comprising acoustic wave components at the distinct frequencies of the at least two modulation components or at harmonic frequencies of the distinct frequencies of the at least two modulation components,
• b) a detection unit comprising one or more sensors, the detection unit configured to simultaneously detect the acoustic waves exhibiting the second modulation while the modulated electromagnetic or particle radiation, respectively, is being continuously emitted towards the target, whereby the acoustic wave components at the distinct frequencies of the at least two modulation components or at harmonic frequencies of the distinct frequencies of the at least two modulation components are detected at the same time, and
• c) a processing device configured to determine at least one thermoacoustic value of at least one of an amplitude and a phase of each of the acoustic wave components at each of the distinct frequencies of the at least two modulation components or at each of the harmonic frequencies of the distinct frequencies of the at least two modulation components.