Figure 1.

Multispectral photoacoustic image. (a) The signals are acquired at several wavelengths. Two pixels are identified: ${\mathbf{x}}_1$ in green, and ${\mathbf{x}}_2$ in purple. (b) Spectra of the pixels ${\mathbf{x}}_1$ and ${\mathbf{x}}_2$: A${}_1$ (in green) is a background pixel with low and flat photoacoustic amplitudes at all wavelengths, and A${}_2$ (in purple) is a pixel with significant photoacoustic amplitudes (a.u., arbitrary units).