Efficient 3D measurement method based on an array chromatic confocal technique.

Abstract

Chromatic confocal measurement (CCM) is an extensive technique of confocal microscopy, where the inherent relation between the focused wavelength and the axial position enables depth sensing. Most CCM works by single-point, resulting in inevitable lateral scans for 3D measurement. To facilitate the process, a 3D measurement method was developed, characterized by combining depth obtained by chromatic confocal technique and lateral information obtained by DMD. To realize the field extension, an objective with hyper-chromatism and wide field was custom-designed to form a 16 × 16 × 5.2 mm³ measurement range. Chromatism was decoded to depth by creating a spectral bar for each measurement point. As depth varied, the peak intensity was observed to shift linearly on a pixelized bar. An effective range of 10 × 10 × 3.35 mm³ was obtained from calibration. To validate the 3D measurement ability, a planar mirror, a three-step height sample of a 10 × 8 mm² field of view (FOV) with 0.1 mm and 2.0 mm height and a letter "V" structure were tested. Current work proves the array-based chromatic confocal technique can be a promising 3D measurement approach of practical significance.