The demand for sub-nanometer resolution of surface roughness measurement is highly increasing in many fields as this property has a significant impact for the characteristic of a material. Besides having sub-nanometer resolution, other preferable traits for the instruments are being non-contact and high-speed measurement. Ellipsometry is an instrument with high sensitivity to material’s characteristics through the measurement of polarization of light. In this paper, an ellipsometry based on the spin Hall effect of light is proposed for sub-nanometer surface area measurement. A modified weak measurement is incorporated in the measurement model to achieve better accuracy. Performance comparison of the modified weak measurement is carried through 2D surface measurement of an optical flat which shows how it improves the measurement result of the SHEL ellipsometry and demonstrates its potential for precision measurement.
Phase shifting profilometry (PSP) has been widely used in many fields of application due to its accuracy and precision in obtaining depth information of a surface. One of the many applications that can take advantage of phase shifting profilometry is skin imaging, where PSP can be beneficial in efficacy testing of a certain cosmetic product, scar healing monitoring, etc. The simplicity of digital phase shifting profilometry hardware configuration further support the use of this technology for skin imaging application. Even though PSP and other interferogram based measurement is well known of its insensitivity to background lighting—because of its utilization of structured light pattern as light modulator—in practice, light interaction with surface finish still contributes to error to some extent. In this paper, the combination of frequency filter and spatial filtering is used to compensate that problem as preprocessing step prior to phase analysis. A simple Butterworth bandpass filter is used to isolate the first order harmonic containing modulation information, followed by Mean Curvature Diffusion to eliminate illuminance noise due to reflection from skin surface. Validation of this method was carried out by testing samples of leather having different textures.
One of standard measuring device used in legal metrology is a vertical storage tank (also known as cylindrical tank) which is a standard measuring tank having a circular cross section and stands on a solid and fixed foundation. To maintain the truth value of a vertical storage tank, a calibrating and re-calibrating process must be carried out. Measuring instruments used in the calibrating and recalibrating process currently have several drawbacks, such as unaffordable prices and impractical use. In this study a cylinder tank volume measurement system was made by utilizing a laser distance gauge. The system using the travel time measurement principle in measuring the radius and height of the vertical storage tank to obtain the value of tank volume. To validate the system a miniature prototype of a vertical storage tank with an actual radius of 2.021 m and a height of 6.083 m was used. The instrument is positioned close to the center point of the vertical storage tank to measure its radius and height. The measuring tool rotates 360° to take 200 measurement data. From the experiment the instrument obtained the average volume measurements with an error of 3.087% and 3.283%.
Profile measurement system based on optical method is becoming widely applied. Among many methods that has been developed, Digital Fringe Projection Profilometry (DFPP) technique provides high resolution results. In processing the 2D image to 3D image, DFPP goes through some steps, which are phase extraction, phase unwrapping, and baseline offset removal. The most important step is phase extraction because this part will extract the deformed fringe information that can determine the accuracy of the 3D reconstruction results. In this paper, there are two methods of phase extraction that is observed, which are phase shifting interferometry and spatial carrier interferometry. Experiments are done with a specific made object that has 3 depths and 2 types of indentations. The results of each phase extraction methods are compared on not only how they reconstruct the flat part and the indentation type, but also how they restore the depth information.
Load and age of rails can result in problems such as breakage, depletion, and expansion that can lead to accidents. Rail inspection has been done manually by operator tracing the rails by walking or riding a special inspection vehicle. These methods obviously are inefficient and inaccurate, as operators might be missing some of the defects. In this research depletion detection of rails are conducted by analyzing changes of the area as well as position shifting of laser spot on captured images by utilizing the triangulation principle. Accuracy and efficiency improvement of rail inspection are expected from this method. Prior calibration of the system was conducted using gauge blocks with thickness varying from 19 to 1 mm with 1 mm decrement. Area changes and position shifting of laser spot are later analyzed through image processing. The system was also implemented on R-54 rail type based on the calibration and later be compared to the manual measurement data. It was shown that the system can detect depletion in rail type R-54. The calibration result shows that the deviation percentage of the measurement of laser area are ranging from 11.41% to 13.48% while for the measurement of laser spot position shift is from 6.91% to 8.80%. Implementation on rail type R-54 shows the deviation percentages between proposed method and manual measurement are ranging from 1.52% to 10.04% for the area measurement, while for the position shifting ranged from 1.11% to 12.68%.
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