| 摘要 |
PURPOSE:To enable invariably accurate focusing control without defocusing even if the surface of an object is finely uneven by driving an objective and the object relatively in the direction of the optical axis of the objective according to the representative position and size of a spot image which are detected by a detecting means. CONSTITUTION:A line sensor 20 is so arranged that when the object 18 to be observed is at the focusing position of the objective 16, the smallest spot image is formed on a nearly center element of the line sensor 20. The output of the line sensor 20 is supplied to an arithmetic and control unit 21, which finds the representative position X and size l of the spot image formed on the line sensor 20 and drives a sample base 17 in the optical axis direction of the objective 16 through a driving device 22 having a stepping motor, etc., according to those values X and l to perform the focusing control automatically. Consequently, even when the surface of the object 18 is finely uneven, the focusing control can accurately be performed at all times without causing any defocusing. |
