FIELD: physics.
SUBSTANCE: apparatus has a beam diameter changing module (21) for changing the first beam diameter which is inherent to the measuring beam which is incident on the optical module to a second beam diameter larger than the first beam diameter. An adjustment stage adjusts the position of the optical condenser module (20) based on information on intensity of the return beam from the position of the analysed object (12) at the first beam diameter. The optical condenser module (20) can be adjusted in a relatively short period of time because a measuring beam with a small diameter is used, and a beam which merges the measuring beam with a reference beam can also be obtained with high resolution in the cross direction because a measuring beam with a large diameter is used.
EFFECT: invention cuts imaging time.
11 cl, 9 dwg
