Exploring the hidden depth by confocal Raman experiments with variable objective aperture and magnification

The article analyzes experimentally and theoretically the influence of microscope parameters on the pinhole-assisted Raman depth profiles in uniform and composite refractive media. The main objective is the reliable mapping of deep sample regions. The easiest to interpret results are found with low magnification, low aperture, and small pinholes. Here, the intensities and shapes of the Raman signals are independent of the location of the emitter relative to the sample surface. Theoretically, the results can be well described with a simple analytical equation containing the axial depth resolution of the microscope and the position of the emitter. The lower determinable object size is limited to 2–4 μm. If sub-micrometer resolution is desired, high magnification, mostly combined with high aperture, becomes necessary. The signal intensities and shapes depend now in refractive media on the position relative to the sample surface. This aspect is investigated on a number of uniform and stacked polymer layers, 2–160 μm thick, with the best available transparency. The experimental depth profiles are numerically fitted with excellent accuracy by inserting a Gaussian excitation beam of variable waist and fill fraction through the focusing lens area, and by treating the Raman emission with geometric optics as spontaneous isotropic process through the lens and the variable pinhole, respectively. The intersectional area of these two solid angles yields the leading factor in understanding confocal (pinhole-assisted) Raman depth profiles. Graphical abstract

STUDY OF THE ELECTRONIC TOTAL STATION TRAVEL FOCUSING LENS MOVEMENT INFLUENCE ON THE SIGHTING AXIS POSITION

When carrying out geodetic work inside production shops or on a construction site, it is necessary to significantly change the focusing of the telescope. Refocusing the telescope can lead to a shift in the sighting axis, and, accordingly, to a decrease in the accuracy of angular measurements. The article presents the results of laboratory studies to determine the horizontal error of collimation and vertical index error of the Leica total station for distances from 2 to 84 m. Therefore, after checking the collimation and vertical index error and automatically taking into account their influence, it is allowed performing geodetic measurements at one position of the vertical circle. In particular, this makes it possible to speed up the execution of fan-shaped trigonometric leveling with short sights, which is performed when observing the settlements of the foundations of industrial buildings and structures.