Patent ID: 8581144

Claim:
A laser processing apparatus for processing a workpiece by using a laser beam, comprising: holding means for holding said workpiece; processing means for applying said laser beam to said workpiece held by said holding means, said processing means having an oscillator for oscillating said laser beam and a focusing lens for focusing said laser beam toward said workpiece; surface displacement detecting means for detecting a surface displacement of said workpiece in a thickness direction of said workpiece relative to said holding means; and focal position adjusting means for adjusting the position of said focusing lens according to the result of detection by said surface displacement detecting means; said surface displacement detecting means including: a detecting light source outputting oscillating light having a plurality of wavelengths different from the wavelength of said laser beam to the workpiece; a wavelength selecting section for selecting one of said plurality of wavelengths output to the workpiece by the detecting light source; a detecting light applying section configured to transmit to said focusing lens said detecting light oscillated from said detecting light source and having the wavelength selected by said wavelength selecting section; and a detecting section configured to detect reflected light reflected on said workpiece by the application of said detecting light to said workpiece.