Improved method for three-dimensional imaging in photoacoustic microscope

The proposed new method partially solves the problem of low signal-to-noise -ratio (SNR) when modulation frequency increases. In this paper; we suggest to keep constant the amplitude of the detected photoacoustic (PA) signal b y linearly increasing the modulation voltage versus frequency. The PA signa l of the sample can be easily estimated by fast Fourier transform. It is al so demonstrated that the presented method is able to detect a subsurface fl aw in a graphite in the 10-100 Hz frequency range.