Browse Prior Art Database

Lens Alignment in a Laser Microwelding Apparatus

IP.com Disclosure Number: IPCOM000078871D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Kuhn, L: AUTHOR [+3]

Abstract

In laser microwelding applications, very accurate positioning of a pulsed laser beam focus is required to achieve reasonable process reproducibility. A technique for achieving such alignment, which depends on the existence of a well-defined energy threshold for damage of a reflecting metal surface is described herein.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Lens Alignment in a Laser Microwelding Apparatus

In laser microwelding applications, very accurate positioning of a pulsed laser beam focus is required to achieve reasonable process reproducibility. A technique for achieving such alignment, which depends on the existence of a well-defined energy threshold for damage of a reflecting metal surface is described herein.

A laser microwelding apparatus 1 is shown schematically in Fig. 1. The requirement for the present application is that the laser beam be focused accurately with respect to a work piece 2. The process described herein establishes the laser focus in the image plane (IP) 3 of a microscope 4, by adjusting the position of lens 5. Work piece 2 is then positioned in apparatus 1 by first bringing it into focus in image plane 3, and then adjusting its position with respect to image plane 3, if defocusing is desired.

It has been observed that a rather sharp threshold for damage to the surface of work piece 2 exists. For instance, with a highly focused three nanosecond laser pulse, a 10% change in energy is sufficient to bring one from a condition of no observable surface damage to easily observable surface damage. The present alignment procedure utilizes this effect as follows:

First, the intensity of the pulsed laser beam is reduced as closely as possible to the threshold. In the focus of the beam, a small hole is formed which is smaller than the optical beam size. A small increment out of focus, the peak intensity is reduced, closer to or below the threshold, resulting in considerably reduced damage or no damage at all. Thus,...