Laser scanning system with reflecting optics

Abstract

A laser beam scanning system which utilizes all reflective optics. The scanning system has a variable scan angle and focal length. The variable focal length in the reflecting optical system is achieved by simultaneously moving two perpendicular mirrors.

I claim:  
     
       1. A laser beam scanning system which includes at least one scanning mirror which angularly steers a predetermined portion of a laser beam, the improved features comprising: 
       said laser beam has a center line optical path which sequentially propagates to a first mirror, a second mirror, a third mirror, a fourth mirror, said at least one scanning mirror and then propagates to an external focal point;  
       said first mirror is a curved mirror;  
       said second and said third mirror are generally flat mirrors oriented approximately perpendicular to each other;  
       said fourth mirror is a concave curved mirror;  
       said second and said third mirror are mounted such that they can be simultaneously translated in a predetermined direction while retaining said orientation;  
       said center line optical path has a beam segment of length S which extends from said fourth mirror to said external focal point;  
       said simultaneous translation of said second and said third mirrors in said predetermined direction produces a change in said distance S while producing an angular steering of said laser beam of less than 3 milliraidans for a 10% change in said direction S for said beam segment.  
     
     
       2. An all- reflective high power laser beam scanning system with an adjustable focal length which includes at least one scanning mirror to angularly steer a predetermined portion of a laser beam along an optical path to a workpiece, comprising:    
       
         a first reflective surface in the optical path of the laser beam and curved sufficiently to focus the laser beam at a first focal point;  
       
       
         a pair of second reflective surfaces in the optical path spaced from said first focal point and translatable sufficiently in a predetermined direction to adjust the focus of the laser beam at a second focal point; and  
       
       
         a third reflective surface optically between said pair of second reflective surfaces and said second focal point and before the at least one scanning mirror to reflect the focused laser beam to be steered and to focus the second focal point;  
       
       
         said optical path having a beam segment of predetermined distance which extends from said third reflective surface to said second focal point;  
       
       
         said translation of said pair of second reflective surfaces in said predetermined direction changing the length of said optical path from said third reflective surface to said second focal point to change said predetermined distance whereby to adjust the focus of the beam being steered without producing significant angular deviation to the steered beam at the workpiece. 
       
     
     
       3. The all- reflective high power laser beam scanning system of    claim 2    wherein said pair of second reflective surfaces is simultaneously translatable in said predetermined direction.   
     
     
       4. The all- reflective high power laser beam scanning system of    claim 2    wherein said third reflective surface is curved sufficiently to focus the laser beam at said second focal point.   
     
     
       5. The all- reflective high power laser beam scanning system of    claim 2    wherein the curvature of said first and third reflective surface is off - axis.   
     
     
       6. The all- reflective high power laser beam scanning system of    claim 2    wherein said first, second and third reflective surfaces are mirrors.   
     
     
       7. The all- reflective high power laser beam scanning system of    claim 2    wherein said first focal point is internal and said second focal point is external.   
     
     
       8. An all- reflective high power laser beam scanning system with an adjustable focal length which includes at least one scanning mirror to angularly steer a predetermined portion of a laser beam along an optical path to a workpiece at an external focal point, the features comprising:    
         a first mirror in the optical path of the laser beam and curved sufficiently as an off - axis parabola to focus the laser beam at an internal focal point;    
       
         a pair of flat mirrors oriented approximately perpendicular to each other in the optical path spaced from said internal focal point and translatable sufficiently simultaneously in a predetermined direction to adjust the external focal point; and  
       
         a fourth mirror optically between one of said pair of mirrors and said external focal point to reflect the focused laser beam being steered, and curved sufficiently as an off - axis ellipse to focus the external focal point;    
       
         said optical path having a beam segment of predetermined distance which extends from said fourth mirror to said external focal point;  
       
       
         the translation of said pair of mirrors in said predetermined direction changing the length of said optical path from said fourth mirror to said external focal point to change said predetermined distance whereby to adjust the focus of the beam being steered without producing significant angular deviation to the steered beam at the workpiece.