To shorten acting time taken till focusing by fetching luminance in accordance with reflected light from a sample surface in a specified sampling cycle while relatively consecutively moving a sample and an objective lens.
Spot light from a light source 1 is radiated to the sample 4 through the objective lens 3 and the reflected light from the sample 4 is detected as a luminance signal by a photodetector 11. The lens 3 is consecutively moved at constant speed along a Z-axis in a direction where it is separated from the sample 4 or a direction where it approaches to the sample 4 by a moving and driving part 8. The luminance detected by the photodetector 11 is increased with the movement of the lens 3 and decreased from the point of time when it exceeds a maximum luminance value, and fetched in a luminance detection means 701 in the fixed sampling cycle. The means 701 outputs a signal for stopping the movement of the lens 3 when luminance change at this time, that means, the number of times that the luminance is consecutively decreased and the decreased luminance value coincide with a previously set condition.
KITAHARA AKIHIRO
TAKAMIZAWA NOBUHIRO
OBA MASAHIRO
