Method and system for measuring the relief of an object

USRE42899E1 · kind E1 · reissue

Assignee

• Zygo Corporation · US

Inventors

• Alain Coulombe · Brossard, CA
• Michel Cantin · Brossard, CA
• Alexandre Nikitine · Thurso, CA

Key dates

• Filing date: Jul 14, 2000
• Grant date: Nov 8, 2011
• Expiry date: Jul 14, 2020

Classification

• Technology area (CPC —): General

Abstract

A method and a system for measuring the relief of an object are described herein. The system includes a grid projecting for projecting a grid, an image acquisition apparatus that includes a camera, and a computer. Providing a reference object having common elements with the object to measure, the method includes the steps of a) positioning the grid at three different known positions relative to the camera and the common elements; b) for each position of the grid, projecting the grid unto the reference object and, with the camera, taking an image of the reference object to yield three images having values for each pixel of the camera and c) computing the reference object phase for each pixel using the three reference object intensity values for the corresponding pixel. Steps a), b) and c) are repeated by replacing the reference object by the object to be measured. The difference of height between the object to be measured and the reference object for each pixel are then computed by subtracting the reference object phase and the object phase for the corresponding pixel.