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.
|
1. #3# 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.
0. #3# 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.
0. #3# 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.
0. #3# 3. The all-reflective high power laser beam scanning system of
0. #3# 4. The all-reflective high power laser beam scanning system of
0. #3# 5. The all-reflective high power laser beam scanning system of
0. #3# 6. The all-reflective high power laser beam scanning system of
0. #3# 7. The all-reflective high power laser beam scanning system of
|
1. Field of the Invention
This invention relates to laser equipment which can both scan a laser beam and adjust the optical path to achieve a variable focal length of the laser beam.
2. Description of Prior Art
Laser scanning systems typically utilize galvanometer motors to change the angle of scanning mirrors. Usually the X and Y direction is scanned by separate motors. In many applications a laser beam is scanned on a work piece. To achieve a high power density, the laser beam is usually focused on this work piece. Specialized lens have been developed to achieve a good focus on a flat surface work piece even at a high transmission angle. However, some applications require that the laser beam can be independently focused to accommodate a contoured surface. Normally this focusing is accomplished by translating one or more lenses in an optical system to achieve a variable focal length. Unfortunately, high powered CO2 lasers can cause a thermal distortion in lenses which degrades the quality of the laser beam. Furthermore, lenses are not as durable as metal mirrors for high power laser beam applications. Therefore, it is desirable to utilize all reflective optic components for high power CO2 laser applications. Here a problem arises when making a scanning system with a variable focal length. A change in the focal length requires a change in the optical path length. With reflective optics, a path length change usually also produces an undesirable steering of the beam. The invention presented here is an all reflective laser scanning system where a focus adjustment can be made with a minimum of translationable motion and also without introducing any steering or translation of the laser beam.
The present invention is a laser scanning system with reflective optics. To achieve an adjustable focal length on the scanned laser beam it is necessary to produce an optical path length change between two mirrors which exhibit optical power (curved mirror surfaces). To achieve this, two additional flat mirrors oriented perpendicular to each other, are placed in the optical path between the curved mirrors. A displacement of the two perpendicular mirrors in a predetermined direction will change the optical path length between the curved mirrors and in turn produce an adjustable force in the scanned beam without producing additional deviation to the scanned beam.
In
The center line optical path length between focus 21 and point 23 will be referred to as "s". Therefore, s=B+C+D when mirrors 12 and 13 are in locations depicted in
Distance S is defined as the optical path length to the external focal point 22 from the point 23. That is the predetermined portion of the laser beam which is scanned by scanning mirrors 15 and 16. The object of this invention is to prevent the focus adjustment from introducing a substantial scanning of this predetermined portion of the laser beam. For CO2 laser applications, the angle steering introduced by a change in the external focus should be kept less than 3 milliradians for each 10% change in distance S. Properly translating mirrors 12 and 13 in direction 27 (
In
While there has been shown and described a preferred embodiment it is to be understood that other modifications may be made without departing from the spirit and scope of the invention.
Patent | Priority | Assignee | Title |
7570407, | Feb 19 2007 | Fujitsu Limited | Scanning mechanism, method of machining workpiece, and machine tool |
9182595, | Jun 02 2011 | NEC Corporation | Image display devices |
Patent | Priority | Assignee | Title |
4160939, | Sep 13 1977 | Xerox Corporation | Motor speed control system |
4232960, | Feb 21 1979 | Xerox Corporation | Scanning system |
4388651, | May 28 1981 | GSI Group Corporation | Method and apparatus for generating a scanned optical output signal |
4461947, | Aug 24 1982 | Allied Corporation | Rotating laser beam with coincident gas jet |
4469931, | Sep 13 1982 | MACKEN LASER, INC A CA CORPORATION | Laser assisted saw device |
4755999, | Mar 25 1985 | MACKEN LASER, INC A CA CORPORATION | Laser apparatus utilizing a magnetically enhanced electrical discharge |
4921338, | May 09 1989 | MACKEN LASER, INC A CA CORPORATION | Corrective optics for rectangular laser beams |
4941731, | Jul 01 1987 | MACKEN LASER, INC A CA CORPORATION | Corner cube utilizing generally spherical surfaces |
5142119, | Mar 14 1991 | Saturn Corporation | Laser welding of galvanized steel |
5155323, | May 16 1991 | MACKEN LASER, INC A CA CORPORATION | Dual focus laser welding |
5206763, | May 09 1989 | OPTICAL ENGINEERING, INC | Corrective optics for rectangular laser beams |
5237149, | Mar 26 1992 | Laser machining utilizing a spacial filter | |
5274492, | Jul 02 1992 | Light spot size and shape control for laser projector | |
5276546, | May 20 1991 | Scanner Technologies Corporation | Three dimensional scanning system |
5528613, | Apr 12 1993 | OPTICAL ENGINEERING, INC | Laser apparatus utilizing a magnetically enhanced electrical discharge with transverse AC stabilization |
5539180, | Feb 28 1991 | Fanuc, Ltd. | Method of laser beam welding galvanized steel sheets with an auxiliary gas containing oxygen |
5618452, | Jul 14 1992 | Mitsubishi Denki Kabushiki Kaisha | Method and apparatus for laser welding with an assist gas including dried air and the assist gas composition |
DE94072884, | |||
EP476965, | |||
FR199650, |
Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Aug 19 1998 | Optical Engineering, Inc. | (assignment on the face of the patent) | / | |||
Feb 21 2013 | OPTICAL ENGINEERING, INC | UTICA ENTERPRISES, INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 030059 | /0753 |
Date | Maintenance Fee Events |
Mar 02 2004 | M1552: Payment of Maintenance Fee, 8th Year, Large Entity. |
Mar 13 2008 | M1553: Payment of Maintenance Fee, 12th Year, Large Entity. |
Date | Maintenance Schedule |
Jul 01 2006 | 4 years fee payment window open |
Jan 01 2007 | 6 months grace period start (w surcharge) |
Jul 01 2007 | patent expiry (for year 4) |
Jul 01 2009 | 2 years to revive unintentionally abandoned end. (for year 4) |
Jul 01 2010 | 8 years fee payment window open |
Jan 01 2011 | 6 months grace period start (w surcharge) |
Jul 01 2011 | patent expiry (for year 8) |
Jul 01 2013 | 2 years to revive unintentionally abandoned end. (for year 8) |
Jul 01 2014 | 12 years fee payment window open |
Jan 01 2015 | 6 months grace period start (w surcharge) |
Jul 01 2015 | patent expiry (for year 12) |
Jul 01 2017 | 2 years to revive unintentionally abandoned end. (for year 12) |