Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Electric Vector Rotator for an Inspection Tool

IP.com Disclosure Number: IPCOM000045251D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Thorp, LD: AUTHOR

Abstract

One problem that may arise in the substrate inspection system of U.S. Patent 4,065,212 involving the optical alignment of the system, is the non-equal amplitude division at the 60-degree beam-splitter. The mirror is coated for "S" incident polarization (perpendicular to the plane of incidence), and some of the mirrors may differ in the split ratio by as much as 3-5 percent. This can complicate the threshold setting on the system.

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 100% of the total text.

Page 1 of 2

Electric Vector Rotator for an Inspection Tool

One problem that may arise in the substrate inspection system of U.S. Patent 4,065,212 involving the optical alignment of the system, is the non-equal amplitude division at the 60-degree beam-splitter. The mirror is coated for "S" incident polarization (perpendicular to the plane of incidence), and some of the mirrors may differ in the split ratio by as much as 3-5 percent. This can complicate the threshold setting on the system.

The addition of a mounted rotatable half-wave plate at the laser output will enable one to rotate the laser output vector selectively and tune the beam splitting ratio to compensate for any inequalities.

This results, in effect, in tuning the vector by rotation so that the amplitudes will change. Less will be reflected at the 60-degree mirror and more will be transmitted, thus balancing the light amplitudes A40 and A60, as shown in Fig. 1.

The wave-plate used will have to possess 10-5 polish and 10/1 Lambda transmission quality. It should have a wedge angle of less than 1 arc-minute. This will minimize misalignment effects due to rotation of the plate.

The action of Lambda/2 plate as a simple rotator is shown in Fig. 2. A linearly polarized beam incident on the plate at an angle +0 to the fast axis will emerge at an angle -0, having been rotated through an angle of 20.

1

Page 2 of 2

2

[This page contains 5 pictures or other non-text objects]