Patent ID: 7795560

Claim:
An apparatus for processing a work-piece, comprising: a laser source configured for emitting laser beams, a lens module configured for adjustably focusing the laser beams onto the work-piece, the lens module comprising a first lens assembly disposed in optical alignment with the laser source, the first lens assembly comprising a first lens set having a positive refractive power and a second lens set having a negative refractive power, wherein a distance between the first lens set of the first lens assembly and the second lens set of the first lens assembly satisfies the following equation: d 12 =( k 1 +k 2 −k 12 )/( k 1 ×k 2 ) wherein k 1 represents an index of refraction of the first lens set, k 2 represents an index of refraction of the second lens set, k 12 represents an index of refraction of the first lens assembly, and an effective focal length f 1 of the first lens assembly satisfies the following equation: f 1 =1 /k 12 and a back focal length f 2 of the first lens assembly satisfies the following equation: f 2 =(1− d 12 ×k 1)/ k 12 =f 1 ×(1 −d 12 ×k 1 ), and a feedback module configured for receiving the laser beams reflected from the work-piece and generating a feedback signal based on the reflected laser beams.