Fast weighted centroid algorithm for single particle localization near the information limit

Optical vortex tracking algorithm based on the Laguerre-Gaussian transform

Optical vortices are stable phase singularities, revealing a zero-point in the intensity distribution. The localization of this singular point is of significant importance for any application that relies on vortices and their behavior. However, there is still a need for an adaptable, fast, and precise method of singular point localization. Here we show, that the Laguerre-Gaussian transform method can meet those criteria. We compared the performance of this method with two other tracking methods (phase retrieval and weighted centroid) in various conditions. We found out that not only Laguerre-Gaussian transform offers high accuracy, but also does not lose its advantages in the low-contrast regime. The versatility of this algorithm is examined in the optical vortex aberrometry, where we sense two artificially introduced aberrations.

Locally adaptive thresholding centroid localization in confocal microscopy

We introduce an iteration-free approach, based on a centroid algorithm with a locally adaptive threshold, for nanometer-level peak position localization of the axial response signal in confocal microscopy. This approach has localization accuracies that are near theoretical limits, especially when there is a small number of sampling points within the discrete signal. The algorithm is also orders of magnitude faster compared to fitting schemes based on maximum likelihood estimation. Simulations and experiments demonstrate the localization performance of the approach.

Quantum 3D thermal imaging at the micro-nanoscale

Real-time and accurate measurement of three-dimensional (3D) temperature field gradient maps of cells and tissues would provide an effective experimental method for analyzing the coupled correlation between metabolism and heat, as well as exploring the thermodynamic properties of nanoparticles under complex environments. In this work, a new principle of quantum 3D thermal imaging is proposed. The photoluminescence principle of quantum dots is expounded and CdTe QDs are prepared by aqueous phase synthesis. Fluorescence spectral characteristics of QDs at different temperatures are studied. The optimized algorithm of the optical spot double helix point spread function is proposed to improve the imaging, where optimized light energy increased by 27.36%. The design scheme of a quantum 3D thermal imaging system is presented. The measurement range is (-8 mm, +8 mm). The temperature is calculated according to the temperature-heat curve of quantum dots. The double helix point spread function has converted the defocus distance of QDs into the rotation angle of the double optical spot, thereby determining its position. The experimental results reveal that real-time 3D tracking and temperature measurements of quantum dots at the micro-nanoscale are achieved. Overall, the proposed nano-scale 3D quantum thermal imaging system with high-resolution may provide a new research direction and exploration of many frontier fields.

A new tracking algorithm for multiple colloidal particles close to contact

In this paper, we propose a new algorithm based on radial symmetry center method to track colloidal particles close to contact, where the optical images of the particles start to overlap in digital video microscopy. This overlapping effect is important to observe the pair interaction potential in colloidal studies and it appears as additional interaction in the measurement of the interaction with conventional tracking analysis. The proposed algorithm in this work is simple, fast and applicable for not only two particles but also three and more particles without any modification. The algorithm uses gradient vectors of the particle intensity distribution, which allows us to use a part of the symmetric intensity distribution in the calculation of the actual particle position. In this study, simulations are performed to see the performance of the proposed algorithm for two and three particles, where the simulation images are generated by using fitted curve to experimental particle image for different sized particles. As a result, the algorithm yields the maximum error smaller than 2 nm for [Formula: see text] μm silica particles in contact condition.

Optical tweezer calibration by using a part of the intensity distribution of a trapped particle

In this paper, we demonstrated that an optical tweezer setup can be calibrated by using a part of the symmetric intensity distribution of the trapped particle in digital video microscopy. First, we modified the radial symmetry center method, which was a recently proposed position detection algorithm. This algorithm uses gradient vectors of the particle intensity distribution, which allows us to use a part of the symmetric intensity distribution in the calculation of the particle center. We applied the modified algorithm to different camera image configurations, which are obtained by cutting the same experimental video frames. We further calibrated the trap stiffness for each camera configuration. Then we compared the trap stiffness values and the position distributions. As a result, we can conclude that optical tweezer setups can be calibrated by using a part of the intensity distribution of the trapped particle.

Research of optical rotation measurement system based on centroid algorithm

An optical rotation measurement system based on digital signal processor, modulated laser, and step motor rotating stage is established. Centroid algorithm featured fast and simple calculation is introduced to process light signals with or without sample to obtain the optical rotating angle through the step difference between two centroids. The system performance is proved experimentally with standard quartz tubes and glucose solutions. After various measurements, the relative error and precision of the system are determined to 0.4% and 0.004°, which demonstrates the reliable repeatability and high accuracy of whole measurement system.