Locally adaptive thresholding centroid localization in confocal microscopy

Measurement of thickness and refractive index of transparent material synchronously based on chromatic confocal sensor

A defined refractive index is essential to measure the thickness of transparent materials with a chromatic confocal sensor (CCS). To overcome this limitation, a new measuring model is proposed by configuring a motor to drive the CCS for movement and placing a reflector behind the sample. This innovative approach enables the measurement of thickness and refractive index of transparent material synchronously through geometric calculations based on peak signals from different surfaces. Experimental results show that the model can achieve an average thickness measurement deviation of ±0.4µm and an average refractive index measurement deviation of ±0.005, making it highly suitable for industrial applications in thin film manufacturing sectors such as new energy vehicles, flexible displays, biomedicine, and more.

An Enhanced DV-Hop Localization Scheme Based on Weighted Iteration and Optimal Beacon Set

Node localization technology has become a research hotspot for wireless sensor networks (WSN) in recent years. The standard distance vector hop (DV-Hop) is a remarkable range-free positioning algorithm, but the low positioning accuracy limits its application in certain scenarios. To improve the positioning performance of the standard DV-Hop, an enhanced DV-Hop based on weighted iteration and optimal beacon set is presented in this paper. Firstly, different weights are assigned to beacons based on the per-hop error, and the weighted minimum mean square error (MMSE) is performed iteratively to find the optimal average hop size (AHS) of beacon nodes. After that, the approach of estimating the distance between unknown nodes and beacons is redefined. Finally, considering the influence of beacon nodes with different distances to the unknown node, the nearest beacon nodes are given priority to compute the node position. The optimal coordinates of the unknown nodes are determined by the best beacon set derived from a grouping strategy, rather than all beacons directly participating in localization. Simulation results demonstrate that the average localization error of our proposed DV-Hop reaches about 3.96 m, which is significantly lower than the 9.05 m, 7.25 m, and 5.62 m of the standard DV-Hop, PSO DV-Hop, and Selective 3-Anchor DV-Hop.

Asymmetry robust centroid localization in confocal microscopy

We present a centroid algorithm with asymmetry-robust error compensation for the peak position localization of asymmetrical axial response signals in confocal microscopy. Compared with the state-of-the-art algorithms, which are usually developed for symmetrical signals, our asymmetry robust centroid algorithm is found to have much smaller localization bias and higher precision for an asymmetrical confocal signal in numerical simulations and experiments.

Embedded nanometer position tracking based on enhanced phasor analysis

We present an embedded real-time 1D position tracking device at a nanometer precision. The embedded algorithm extracts the most appropriate region of the signal without manual intervention and estimates the position based on the phase shift from the signal's first Fourier harmonic. Using simulated datasets, we demonstrate that the proposed approach can achieve a similar precision to the state-of-the-art maximum likelihood fitting-based method while executing over four orders of magnitude faster. We further implemented this algorithm on a low-power microprocessor and developed a simple, compact, and low-cost embedded position tracking device. We demonstrate nanometer tracking precision in real-time drift tracking experiments.