Method and apparatus for improving laser hole resolution

Abstract

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.

Description

BACKGROUND OF THE INVENTION

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 INVENTION

The 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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a prior art laser drilling system for operating on a moving product such as a web.

FIG. 2 is a diagram of a laser drilling system for operating on a moving web employing a rotating polygon scanner according to a first embodiment of the present invention.

FIG. 3 is a diagram of a laser drilling system for operation on a moving web employing an angularly adjustable refracting material according to a second embodiment of the present invention.

FIG. 4 is a diagram of a laser drilling system for operating on a moving web employing a linearly actuated lens according to a third embodiment of the present invention.

FIG. 5 is a diagram of a laser drilling system for operating on a moving web employing a rotating disk having a plurality of lenses mounted thereon according to a fourth embodiment of the present invention.

FIG. 6 is a top view of the rotating disk employed in the laser drilling system shown in FIG. 5.

FIG. 7 is a diagram of a laser drilling system for operating on a moving web employing an optical deflector according to a fifth embodiment of the present invention.

(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.