Patent ID: 7378636

Claim:
A wavelength conversion method of laser beam by non-linear wavelength conversion using a non-linear optical crystal, comprising the step of: the non-linear optical crystal is moved along an X-axis and a Y-axis individually, said X-axis and said Y-axis are arranged to be severally orthogonal to an incident laser beam to said non-linear optical crystal and orthogonal to each other so as to constitute an X-Y plane, in order to change an incident position of said incident laser beam in said non-linear optical crystal, output of laser beam emitted from said non-linear optical crystal is detected for each incident position of said incident laser beam that is changed by movement of said non-linear optical crystal; and positions where said output of laser beam emitted from said non-linear optical crystal whose output shows a predetermined value or higher are selected from said incident positions of said incident laser beam in said non-linear optical crystal based on detection result and laser beam is made incident to the positions to perform non-linear wavelength conversion.