| 摘要 |
PROBLEM TO BE SOLVED: To widen an automatic stage controlling range in automatic focusing. SOLUTION: This device is provided with 1st and 2nd detection means generating 1st and 2nd light quantity signals S29 and S30 changed at a level in a reverse direction to each other in accordance with the change of the distance in an optical axis direction between an image-forming optical system and a specimen. Furthermore, an automatic focusing control means performs the focusing of the image-forming optical system based on the relation of the levels of the 1st and the 2nd light quantity signals to which offset V0 equivalent to a difference between the 1st and the 2nd light quantity signals at a focusing position by the image-forming optical system is added in a 1st area L5 near the focusing position of the image-forming optical system, and performs the focusing of the image-forming optical system based on the relation of the levels of the 1st and the 2nd light quantity signlas to which the offset V0 is not added in 2nd areas L3 and L4 farther from the focusing position than the 1st area L5. |
