Multipoint scanning dual-detection confocal microscopy for fast 3D volumetric measurement

Programmable high-speed confocal reflectance microscopy enabled by a digital micromirror device

The digital micromirror device (DMD) has been used to achieve parallel scanning in confocal microscopy significantly increasing acquisition speed. However, for confocal reflectance imaging, such an approach is limited to mostly surface imaging due to strong backreflections coming from the DMD that can dominate the signal recorded on a camera. Here, we report on an optical configuration that uses separate areas of DMD to generate multiple spots and pinholes and thereby prevents backreflections from the DMD from reaching the camera. We thus demonstrate confocal imaging of weakly reflecting objects, such as a pollen grain sample.

DMD-based three-dimensional chromatic confocal microscopy

In this paper, a digital mirror device (DMD)-based chromatic confocal microscopy is proposed and demonstrated for three-dimensional (3D) surface profiling without any mechanical scanning. In this method, the DMD works as the multipoint source and multi-pinhole at the same time to achieve the lateral scanning. Moreover, axial scanning is realized through the chromatic aberration of the confocal optics. Since the micromirror array of the DMD is not perpendicular to the confocal imaging axis, a corresponding calibration is needed to eliminate the tilt effects and perform accurate 3D imaging. The measurement range with the current optical system is 45 µm over 505-650 nm working spectrum and can be increased by using a custom objective with large chromatic aberration. The system performance has been demonstrated with a multistep sample.