Innovative full-field chromatic confocal microscopy using multispectral sensors

TL;DR

This paper presents a novel full-field chromatic confocal microscopy system that uses multispectral sensors and a digital micromirror device to achieve rapid 3D surface measurement with high accuracy and a large field of view.

Contribution

It introduces an innovative optical configuration with a specially designed chromatic dispersive objective for full-field 3D imaging using multispectral sensors.

Findings

Achieved a measurement field of view of 1.8mm x 1.3mm in one shot.

Measurement repeatability is less than 0.6 micrometers.

Developed a normalized cross-correlation algorithm for accurate surface profile reconstruction.

Abstract

A full-field chromatic confocal microscopy using a multispectral sensor was developed for quasi-one-shot microscopic 3D surface measurement. An innovative optical configuration employs a digital micromirror device (DMD) and a multispectral sensor is used to realize chromatic confocal microscopy with full-field area scanning. In the optical design, an area-scan type chromatic dispersive objective is specially designed to achieve measuring specification. Based on an 8x chromatic dispersive objective, the FOV for one shot measurement can be reached to 1.8mm*1.3mm which is immersive to microscopic profilometry. The spectral image captured by the multispectral sensor at each pinhole position has a unique spectrum pattern corresponding to its conjugate measured depth. A normalized cross-correlation (NCC) algorithm is developed to establish a spectrum-depth response curve with its corresponding spectrum pattern sets for accurate reconstruction of the tested 3D surface profile. With real test on standard targets, the measurement repeatability for a single surface depth is less than 0.6 micrometer.