The removal of light from outside the 'focal plane' can be achieved by selecting specific rows of pixels on the CCD array detector and closing the vertical slit within the instrument to ~ 10 µm. This coupled to an accurately controlled sample stage allows non-destructive depth profiling with a resolution of 2 µm using a x100 microscope objective.

• the solid line shows the path of light in the focal plane
• the dotted lines show paths of light outside the focal plane
• the Renishaw Ramascope uses slits rather than a pinhole as this improves the ease of alignment