| 摘要 |
PURPOSE:To detect a focal position with respect to many kinds of objects to be irradiated whose reflection characteristics are different by providing a means for selecting that which has the maximum value from each output corresponding to plural detection use laser beams, and calculating the focal position. CONSTITUTION:A Z table 6 is set to an initial position, an optical image 10a by a first detection use laser beam 8a is formed on an XY plane 7 of a working surface 5, and its reflected light is detected by a photoelectric converting means 11. Subsequently, an optical image 10b by a second detection use laser beam 8b is formed, and its reflected is detected by the photoelectric converting means 11. Next, a larger one of outputs of the photoelectric converting means 11 corresponding to both the detection use laser beams 8a, 8b whose wavelengths are different from each other is selected by a laser beam selecting means 16, and its output is set to a binarizing circuit 12. From the data, a binarized image is derived, and a focal position is detected from a position of the working surface 5 on which its maximum width becomes minimum. |
