Abstract: A thrust converter has a connection pipe 30 for outputting reciprocating motion of first rotation/reciprocation conversion means 115 and a joint nut 28. The joint nut 28 is interposed between the first rotation/reciprocation conversion means 115 and the connection pipe 30, connected to the first rotation/reciprocation conversion means 115, and coupled to the connection pipe 30 with a screw. The thrust converter is constructed such that connection pipe 30 is driven by a second servo motor 31, thereby setting an arbitrary position where the joint nut 28 and the connection pipe 30 are to be coupled together. As a result, there is obtained a thrust converter which can shorten the axial length of the thrust converter in comparison with a required stroke, which obviates a necessity for operating two motors synchronously when a workpiece is fed to a gripping position or the like, and which facilitates motor control.

Abstract: An electrode for adsorption (17) is provided in the vicinity of the laser processing position, and an electrode (18) for detecting capacitance is provided on the outer periphery of the electrode for adsorption (17), so that the capacitance (C) between the electrode (18) for detecting capacitance and the workpiece (15) is detected, with a voltage being applied to between the electrode for adsorption (17) and the workpiece (15), to thereby control the focal position (12a) of the laser beam (12) based on the detected capacitance (C).