Achieved High-Sensitivity Single-Band Ratiometric Optical Thermometry by Manipulating the Intervalence Charge-Transfer Band Position.

Currently, optical thermometry has received widespread attention because of its noncontact and wide temperature range, but most of them are based on the application of dual-band optical ratiometric thermometry, so the development of a single-band ratiometric (SBR) optical thermometry, which is easier to analyze and use, is particularly important. In this work, the position of the intervalence charge-transfer (IVCT) band for Na2Gd2-xLaxTi3O10:Pr3+ (x = 0, 0.5, 1.0, 1.5, 2.0) was modulated using Gd/La substitution, enhancing the thermal response difference of Pr3+ 1D2 → 3H4 under charge-transfer band (CTB) and IVCT band excitation, thereby achieving high-sensitivity SBR optical thermometry, and the maximum relative sensitivity (Sr-max) reached 2.95% (at 298 K). In addition, this series of phosphors has high-color-purity red emission, indicating that it has potential for multifield applications.

Conic tangents based high precision extraction method of concentric circle centers and its application in camera parameters calibration.

A high-precision camera intrinsic parameters calibration method based on concentric circles was proposed. Different from Zhang's method, its feature points are the centers of concentric circles. First, the collinearity of the projection of the center of concentric circles and the centers of two ellipses which are imaged from the concentric circles was proved. Subsequently, a straight line passing through the center of concentric circles was determined with four tangent lines of concentric circles. Finally, the projection of the center of concentric circles was extracted with the intersection of the straight line and the line determined by the two ellipse centers. Simulation and physical experiments are carried out to analyze the factors affecting the accuracy of circle center coordinate extraction and the results show that the accuracy of the proposed method is higher. On this basis, several key parameters of the calibration target design are determined through simulation experiments and then the calibration target is printed to calibrate a binocular system. The results show that the total reprojection error of the left camera is reduced by 17.66% and that of the right camera is reduced by 21.58% compared with those of Zhang's method. Therefore, the proposed calibration method has higher accuracy.