In a scanning microscope, the reflected light from the sample surface when a light beam is scanned on the sample surface, is detected through a pinhole (or a slit) set at the imaging surface in the optical system of the microscope.
This is called confocal optics.
Focusing occurs both on sample surface and imaging surface, and only the light in focus is detected selectively and this is called confocal.
In confocal optics, the out of focus light from the sample surface barely goes through a pinhole (or a slit) and only the part in focus on the surface is very clearly observed , accordingly.
Also, the image becomes of a very shallow focal depth.
A confocal microscope can evaluate spatial structure of sample surface by taking in images while moving the sample in focal direction, taking advantage of focal depth shallowness.
The Lasertec confocal optics has very high resolution in focal direction and is applied to bump/step evaluation in the semiconductor field and roughness measurement of mechanically processed surfaces. |
