| 摘要 |
An autofocus mechanism includes a light source 11 emitting light through an objective lens 14 at a work piece W; a first detector 16b detecting a portion of light reflected by the work piece W and generating a first signal A; a second detector 16a detecting a portion of the reflected light and generating a second signal B; a first amplifier 21 amplifying the first signal A and generating a first amplified signal A'; a second amplifier 22 amplifying the second signal B and generating a second amplified signal B'; an amplification rate definer 30 defining an amplification rate of each of the first amplifier 21 and the second amplifier 22 based on the first amplified signal A' and the second amplified signal B', respectively; and a calculator 51 identifying a focal position of the objective lens 14 based on the first amplified signal A' and the second amplified signal B'. |
