Microscopic shape-from-focus (SFF) provides a practical noncontact approach for 3-D measurement of industrial micro-holes. However, specular reflections from reflective entrances and inner walls can distort axial focus responses and degrade depth localization. This paper presents a reliability-aware SFF framework that treats residual reflection disturbance as a source of observation error rather than only an image artifact. An optional photometric preconditioner is first used to attenuate severe reflection. Local focus peaks are then fitted in physical axial coordinates, and each valid observation is assigned a reflection-conditioned peak-localization error scale. During depth recovery, the original SFF observation is retained and compared with a structure-supported surrogate according to their estimated error scales. The surrogate is introduced only when sufficient neighborhood support is available and its estimated error scale is lower. Experiments on reflective micro-hole samples were conducted using Alicona InfiniteFocus G5 measurements as reference. On 32 evaluation holes, the proposed method achieved mean absolute diameter and axis-angle deviations of 21.5 μm and 1.277°, respectively, together with a point-cloud MAE of 12.3 μm, giving the lowest values of these three metrics among the compared SFF methods. The proposed error scale maintained a Spearman correlation of 0.57–0.65 with the reference-based peak-localization error over axial sampling intervals of 10–30 μm. For a single complete measurement result, the expanded uncertainties were 12.7 μm for diameter and 0.516° for axis angle (k = 2), while repeated-acquisition and illumination-variation tests further showed improved measurement stability under reflective conditions. These results demonstrate that the proposed framework improves the accuracy and robustness of microscopic SFF measurement for reflective micro-holes.
We propose a triaxial optically-pumped magnetometer (OPM) suitable for measurements in a geomagnetic environment. This magnetometer adopts a dual-beam pump-probe configuration and exploits self-oscillation to adjust the frequency of applied magnetic field near the Larmor frequency. Subsequently, it detects the free-induction-decay(FID) signal from spin-polarized 87Rb atoms to accurately measure the magnitude of the ambient magnetic field. By applying alternating magnetic fields and precisely controlling the trigger timing for each axis, vector information of the ambient magnetic field can be derived. Notably, the magnetometer enables free switching between scalar and vector measurement modes. Triaxial measurements were conducted in a geomagnetic field environment, achieving noise floors of 24.6 pT/Hz1/2, 9.4 pT/Hz1/2, and 5.5 pT/Hz1/2 for the three axes, respectively. The proposed magnetometer demonstrates promising applicability in geomagnetic environments with high dynamic performance requirements.
The widespread transmission of respiratory diseases such as COVID-19 and influenza poses a significant threat to public health. As respiratory droplets are a primary transmission vector, real-time monitoring of their spatial dispersion is critical for effective exposure control. Here, we developed a droplet sensor by self-assembling black phosphorus quantum dots (BPQDs) onto silica (SiO2) microspheres, enabling the detection of droplets transmitted up to 2.2 meters. Multiple sensors with similar response waveforms were strategically deployed on a mannequin to capture the droplet splashes. By varying the cough target locations, we evaluated the relationship between droplet deposition and transmission distance. This analysis revealed a decreasing droplet deposition gradient with downward shifts in the cough target location and increasing transmission distance. A correlation was also observed between the signals near the chest and those near the mouth and nose, providing preliminary insights into the placement of wearable droplet sensors on the human body. This study provides a droplet spatial spread monitoring method that could help prevent and control respiratory infectious diseases, thereby protecting public health.
