Vester Ahmed (toytime65)

In fringe projection profilometry, errors related to projectors are not easy to compensate for, as a projector is much more difficult to calibrate than a camera. Immune to projector errors, the depth recovering method based on pixel cross-ratio invariance enables circumventing this issue by calculating the depth of a point from the shift of its camera pixel instead of from its fringe phase. With this existing technique, however, one has to search three reference phase maps along epipolar lines for pixels having the same phases. Doing so increases the measurement time significantly. To improve measurement efficiency, this paper derives, from the pixel cross-ratio invariance, a generic function representing the relationship between the depths and the corresponding pixel shifts and suggests a calibration method for determining its coefficient matrices. Using this function allows us to recover object depths just by searching a single reference phase map, thus reducing the time duration for data processing to about one-third. Besides, different from the previous method, which depends on exactly three reference phase maps, the proposed method calculates the function coefficients from more reference phase maps in the least-squares sense and denoises the benchmark reference phases by use of averaging technique, thus improving measurement accuracy. Experimental results demonstrate this method to be effective in improving measurement accuracy and efficiency.To solve the issue of external magnetic fields interfering with magneto-optical glass current sensors (MOCS), this paper proposes a strip-like splicing structure. First, a mathematical model for integrating the magnetic field strength along the optical path is constructed, and the relationship between the gap size $a$a, the interference source distance $d$d, the angle of the interference source $\theta $θ, and the relative error $\varepsilon $ε is analyzed. selleck Then, an optical-electromagnetic COMSOL Multiphysics simulation model is constructed. The simulation results are in good agreement with the theoretical results. Finally, the strip-like splicing MOCS structure is optimized by combining two different MOCSs with a tilt angle of 45°. Thus, their output signals are summed and the adjacent interference phase signals nearly compensate mutually. This new structure facilitates real-world installation, avoiding the angle being limited to a fixed value, and meeting a 0.2 accuracy of the anti-electromagnetic interference properties.An advanced optical design has been proposed for an astigmatism-free Offner imaging spectrometer with high resolution in the broadband spectrum. The anastigmatic theory is thoroughly analyzed. Astigmatism is corrected by two pairs of lens-mirror combinations. On the basis of the concentric structure, the lens is used to make the meridional image distance equal to sagittal image distance. An example of the design has been presented with f-number of 3 working in 400-1000 nm according to the optimized theory. By the ray-tracing results, the spectral sampling is 0.6nm/pixel, and the RMS spots radii in all fields of view are less than 5 µm. The spectral keystone distortion and smile distortion are less than 0.1%. The prototype is manufactured based on theory and tolerance analysis. The achieved prototype has advantages of high spectral resolution (3 nm) and compact configuration.Here, we investigate effects of the size of pores in porous alumina powders on the broadening of the oxygen gas absorption line. The line broadening is caused by collisions of oxygen molecules with the pore walls and is extracted using gas in scattering media absorption spectroscopy (GASMAS), while the average pore size is determined using the gas adsorption technique. The average pore size of the samples studied lies within the range 10-40 nm. In this range, the contribution of the wall collision broadening is found to be approximately inversely related to the average pore diameter.