Fast confocal image processing for inspection

Abstract

The measurement of surface topography is an important inspection task as it provides useful information for process and quality control. A candidate technique for such an application is confocal imaging. The advantages of confocal imaging are that it is a noncontact measurement, can be operated at high speed (greater than 10 megapixels/sec) and submicron resolution, and provides height information in multilayered semitransparent materials. In this paper, we present a scheme for the fast processing of confocal images. The scheme consists of measuring the response function of the confocal system and deriving a deconvolution filter based on this response. The input signal is deconvolved in order to improve the depth resolution and then processed to identify significant peaks. These peaks represent the position of different surfaces in the object being inspected. For semitransparent materials, our scheme is capable of detecting up to two surfaces at a given location.