The effect of edges on photothermal imaging

The photothermal edge effect was theoretically investigated under the realistic assumption of a Gaussian distributed heating beam, which is not only absorbed at the upper surface of the sample, but because of scattered light also in the vertical plane. The photothermal signal scanned over an edge strongly depends on the detector aperture and in the case of a narrow point-like detector aperture it depends also on the radius R. An explanation of elevations in the signal near the edge is given.