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

Abstract

We propose a multipoint scanning dual-detection confocal microscopy (MS-DDCM) system for fast 3D volumetric measurements. Unlike conventional confocal microscopy, MS-DDCM can accomplish surface profiling without axial scanning. Also, to rapidly obtain 2D images, the MS-DDCM employs a multipoint scanning technique, with a digital micromirror device used to produce arrays of effective pinholes, which are then scanned. The MS-DDCM is composed of two CCDs: one collects the conjugate images and the other collects nonconjugate images. The ratio of the axial response curves, measured by the two detectors, provides a linear relationship between the height of the sample surface and the ratio of the intensity signals. Furthermore, the difference between the two images results in enhanced contrast. The normalising effect of the MS-DDCM provides accurate sample heights, even when the reflectance distribution of the surface varies. Experimental results confirmed that the MS-DDCM achieved high-speed surface profiling with improved image contrast capability.

Three-dimensional confocal reflectance microscopy for surface metrology

“…The light beam from a laser is expanded and collimated. In order to effectively illuminate a sample and detect the reflected light, a polarizer and a polarized beam splitter (PBS) can be used instead of a non-PBS, which results in three quarters of light lost [38][39][40]. The beam is polarized by the linear polarizer and reflected by the PBS.…”

“…The transverse scanning can be replaced by a MEMS device that covers a 2D area with millions of individually controlled pixels, such as a digital micromirror device (DMD) [39,[83][84][85] and a spatial light modulator (SLM) [86][87][88]. When the DMD is applied to the direct-view confocal microscopy setup, a programmable pinhole array can be obtained [84,85], that is, the sampling points can be adjusted.…”

“…While the height of a sample can be directly measured from the intensity ratio without axial scanning, the DDCM still needs transverse scanning to cover the 3D volume. The transverse scanning can be replaced by a DMD, which covers a 2D area with up to several million individually controlled micromirrors [39]. Two CCDs, which are conjugated with the DMD, act as virtual multiple pinholes with different sizes, and generate multiple intensity ratios simultaneously at lateral positions, as shown in figure 9(a).…”

Annular-beam dual-detection confocal reflectance microscopy for high-speed three-dimensional surface profiling with an extended volume

“…To achieve accurate and fast 3D volumetric imaging with a simple optical setup, we presented a dual-detection confocal reflectance microscopy (DDCRM) method that uses two different-sized pinholes in front of detectors to obtain different widths of axial response curves and their ratio curve [25][26][27]. Although each detected signal is proportional to the reflectance of the specimen and the laser power, the intensity ratio removes the proportional factor by dividing each signal.…”