Method and apparatus for improving laser hole resolution
A high resolution, high speed laser drilling system for operating on an advancing product operates to advances the product in a predetermined product advancement path at a product advancement speed. A laser-generating source provides a pulsed laser beam having a laser-on time and a laser-off time. The laser beam is reflected to direct a focal point of the laser beam onto the advancing product. The focal point of the laser beam is moved in a direction of the product advancement path during the laser-on time and is moved in a direction opposite to the direction of the product advancement path during the laser-off time. The system is therefore able to improve laser drilling resolution for a given product advancement speed.
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The present invention relates to a high speed laser drilling system, and more particularly to a method of operating a laser drilling system to achieve improved laser hole resolution without sacrificing product advancement speed.
Laser systems are often employed to create uniformly spaced holes in a product material such as an advancing web, and such systems are advantageous because of the high product advancement speed and laser hole resolution that can be achieved. Similarly configured systems are used to create holes in continuously fed sheets and in products advanced on a conveyor. However, there are particular hole size and spacing configurations that limit the product advancement speed and/or laser hole resolution because of the constraint of laser turn-on and turn-off times. Specifically, where holes are spaced a relatively large distance apart in comparison to the size of the holes, laser turn-on and turn-off times can limit the speed of product advancement or the resolution of the laser holes. For example, if the product advances at too high of a speed, the laser may remain on for too long and therefore create too large of a hole. Therefore, a method of operating a laser drilling system that enables high laser hole resolution without sacrificing product advancement speed would be a significant improvement in the art.
BRIEF SUMMARY OF THE INVENTIONThe present invention is a method and apparatus for high resolution, high speed laser drilling of an advancing product. A product is advanced in a predetermined product advancement path at a web advancement speed. A laser-generating source provides a pulsed laser beam having a laser-on time and a laser-off time. The laser beam is reflected to direct a focal point of the laser beam onto the web. The focal point of the laser beam is moved in a direction of the product advancement path during the laser-on time and is moved in a direction opposite to the direction of the product advancement path during the laser-off time. The present invention is therefore able to improve laser drilling resolution for a given product advancement speed.
FIG. 8 is a diagram of a laser drilling system for operating on a moving web employing a galvo scanner.
The present invention addresses this problem associated with prior art laser drilling systems by providing a system for moving the focused laser beam spot at the point where it impinges on the advancing web/product in the same direction as the web/product is moving. The “effective speed” of the web/product in relation to the focused laser beam spot is therefore reduced by the speed of the spot. As a result, higher laser hole resolution may be achieved for a particular absolute web/product advancement speed, since the effective speed of the web/product with respect to the spot is reduced. Several exemplary embodiments are described below with respect to
As a result of the present invention, the advancement of a web material may be performed at quite high speeds without concern for low hole resolution due to a minimum laser-on time, since the “effective speed” of the web during laser-on time is the difference between the advancement speed of the web and the speed of movement of the focal point of the laser due to implementation of a mechanism for moving the focused laser beam spot in the same direction as movement of the web. For particularly widely spaced patterns of small laser holes, the present invention can improve web advancement speed by as much as twenty times, utilizing the full pulsing capability of the laser at maximum web speed. For example, in an exemplary embodiment the achievable laser hole resolution improved from sixty thousandths of an inch diameter holes to three thousandths of an inch laser holes. It should be understood from the above description of the present invention that configurations shown for moving the focused laser beam spot are merely examples of suitable mechanisms for performing the function of the invention. Other scanning devices such as a galvo scanner (e.g., galvo scanner 76, shown in FIG. 8), a resonant scanner, a holographic scanner, or other mechanisms known in the art may also be used to implement the present invention.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
Claims
1. A method of high resolution, high speed laser drilling of an advancing product, the method comprising:
- advancing the product in a predetermined product advancement path at a product advancement speed;
- generating a pulsed laser beam having a laser-on time and a laser-off time; and
- reflecting the laser beam to direct a focal point of the laser beam onto the advancing product;
- drilling a high resolution hole in the product by moving the focal point of the laser beam in a direction of the product advancement path during the laser-on time to reduce the effective speed of product with respect to the laser beam; and
- moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path during the laser-off time.
2. The method of claim 1, wherein the focal point of the laser beam is moved at a speed no greater than the product advancement speed in the direction of the product advancement path during the laser-on time.
3. The method of claim 1, wherein reflecting the laser beam to direct the focal point of the laser beam onto the advancing product, moving the focal point of the laser beam in the direction of the product advancement path during the laser-on time and moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path during the laser-off time comprises:
- providing a reflecting polygon having a plurality reflecting sides for directing the laser beam onto the advancing product; and
- rotating the reflecting polygon so that rotation of a reflecting side causes movement of the focal point of the laser beam in the direction of the product advancement path during laser-on time and rotation between reflecting sides causes movement of the focal point of the laser beam in the direction opposite to the direction of the product advancement path during laser-off time.
4. The method of claim 1, wherein moving the focal point of the laser beam in the direction of the product advancement path and moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path comprises:
- providing a refracting element in a path of the laser beam;
- gradually adjusting an angular orientation of the refracting element during the laser-on time to move the focal point of the laser beam in the direction of the product advancement path; and
- adjusting the angular orientation of the refracting element during the laser-off time to move the focal point of the laser beam opposite to the direction of the product advancement path.
5. The method of claim 1, wherein moving the focal point of the laser beam in the direction of the product advancement path and moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path comprises:
- providing a focusing lens in a path of the laser beam;
- gradually adjusting a linear position of the focusing lens during the laser-on time to move the focal point of the laser beam in the direction of the product advancement path; and
- adjusting the linear position of the focusing lens during the laser-off time to move the focal point of the laser beam opposite to the direction of the product advancement path.
6. The method of claim 1, wherein moving the focal point of the laser beam in the direction of the product advancement path and moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path comprises:
- providing a disk carrying a plurality of focusing lenses in a path of the laser beam; and
- continually rotating the disk so that a selected one of the plurality of focusing lenses is positioned in the path of the laser beam during the laser-on time to move the focal point of the laser beam in the direction of the product advancement path, and so that a portion of the rotating disk between adjacent ones of the plurality of focusing lenses is positioned in the path of the laser beam during the laser-off time to move the focal point of the laser beam opposite to the direction of the product advancement path.
7. The method of claim 1, wherein moving the focal point of the laser beam in the direction of the product advancement path and moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path comprises:
- providing an electro-optic modulator in a path of the laser beam;
- gradually adjusting a signal applied to the electro-optic modulator during the laser-on time to move the focal point of the laser beam in the direction of the product advancement path; and
- adjusting a signal applied to the electro-optic modulator during the laser-off time to move the focal point of the laser beam opposite to the direction of the product advancement path.
8. Apparatus for high resolution, high speed laser drilling of an advancing product, comprising:
- means for advancing the product in a predetermined product advancement path at a product advancement speed;
- a laser-generating source providing a pulsed laser beam having a laser-on time and a laser-off time;
- means for reflecting the laser beam to direct a focal point of the laser beam onto the advancing product;
- means for drilling a high resolution hole in the product by moving the focal point of the laser beam in a direction of the product advancement path during the laser-on time and for moving the focal point of the laser beam in a direction opposite to the direction of the product advancement path during the laser-off time.
9. The apparatus of claim 8, wherein the means for moving the focal point of the laser beam is operable to move the focal point of the laser beam at a speed no greater than the product advancement speed in the direction of the product advancement path during the laser-on time.
10. The apparatus of claim 8, wherein the means for moving the focal point of the laser beam comprises an angularly adjustable refracting element in a path of the laser beam.
11. The apparatus of claim 8, wherein the means for moving the focal point of the laser beam comprises an actuator operable to linearly move a focusing lens in a path of the laser beam.
12. The apparatus of claim 8, wherein the means for moving the focal point of the laser beam comprises a rotatable disk carrying a plurality of focusing lenses in a path of the laser beam.
13. The apparatus of claim 8, wherein the means for moving the focal point of the laser beam comprises an electro-optic modulator in a path of the laser beam.
14. Apparatus for high resolution, high speed laser drilling of an advancing product, comprising:
- means for advancing the product in a predetermined product advancement path at a product advancement speed;
- a laser-generating source providing a pulsed laser beam having a laser-on time and a laser-off time; and
- a rotatable reflecting polygon scanner for directing a focal point of the laser beam onto the advancing product, the rotating reflecting polygon scanner being operable to drill a high resolution hole in the product by moving the focal point of the laser beam in a direction of the product advancement path at a speed no greater than the product advancement speed during the laser-on time and to move the focal point of the laser beam in a direction opposite to the direction of the product advancement path during the laser-off time.
15. A method of high resolution, high speed laser drilling of an advancing web, the method comprising:
- advancing the web in a predetermined web advancement path at a web advancement speed;
- generating a pulsed laser beam having a laser-on time and a laser-off time;
- reflecting the laser beam to direct a focal point of the laser beam onto the advancing web;
- drilling a high resolution hole in the web by gradually adjusting an angular orientation of a refracting element in a first angular direction during the laser-on time to move the focal point of the laser beam in a direction of the web advancement path to reduce the effective speed of the web with respect to the laser beam; and
- adjusting the angular orientation of the refracting element in a second angular direction that is opposite of the first angular direction during the laser-off time by moving the focal point of the laser beam in a direction opposite to the direction of web advancement path to position a focal point of the laser beam during a subsequent laser-on time at a location that is upstream along the web advancement path.
16. A method of high resolution, high speed laser drilling of an advancing web, the method comprising:
- advancing the web in a predetermined web advancement path at a web advancement speed;
- generating a pulsed laser beam having a laser-on time and a laser-off time;
- reflecting the laser beam to direct a focal point of the laser beam onto the advancing web; and
- drilling a high resolution hole in the web by continually rotating a disk carrying a plurality of focusing lenses in a path of the laser beam so that a selected one of the plurality of focusing lenses is positioned in a path of the laser beam during the laser-on time to move the focal point of the laser beam in the direction of the web advancement path to reduce the effective speed of the web with respect to the laser beam, and so that a portion of the rotating disk between adjacent ones of the plurality of focusing lenses is positioned in the path of the laser beam during the laser-off time to move the focal point of the laser beam in a direction opposite of the web advancement path to position a focal point of the laser beam during a subsequent laser-on time at a location that is upstream along the web advancement path.
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Type: Grant
Filed: Jul 21, 2010
Date of Patent: May 13, 2014
Assignee: Preco, Inc. (Somerset, WI)
Inventor: William E. Lawson (Somerset, WI)
Primary Examiner: Geoffrey S Evans
Application Number: 12/840,534
International Classification: B23K 26/00 (20060101); B23K 26/06 (20060101); B23K 26/38 (20060101);