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Advanced Measurement Techniques in Surface Metrology
Published in Salah H. R. Ali, Automotive Engine Metrology, 2017
Interferometers and microscopes are combined in interferometric microscopy. Through this combination, very good resolution and significant vertical range can be obtained. Interferometry as a measurement tool is certainly not new but combining old interferometry techniques with modern electronics, computers, and software has produced extremely powerful measurement tools [56–62]. The interferometer is responsible for scanning on a nanoscale, and the microscopy head is displaced on a microscale giving a vertical range even 1 mm. Descriptions of the operation exceeding and construction of scientific interferometric microscopes can be found in [63,64]. Typically, there are two different techniques commonly used in phase shifting interferometry (PSI) and scanning WLI. WLI microscopy uses a broadband light source [65–67]. The optical system focuses the light through a microscope objective onto a surface. A principle schematic of a scanning white light system [68–71] is shown in Fig. 2.11. The upper beam splitter directs light from the light-source towards the objective lens. The lower beam splitter in the objective lens splits the light into two separate beams. One laser beam is directed to the surface of object and the other beam is reflected beam directed to a smooth reference mirror. When the reflected beams are recombined, interference fringes are produced around the equal path condition for the two beams. This equal path condition can be detected for each local area of the surface corresponding to each pixel of the camera detector. Scanning the surface vertically with respect to the microscope and detecting the optimum equal path condition at every pixel in the camera results in a topographic image.
Advanced Topics
Published in Araz Yacoubian, Optics Essentials, 2018
Interferometry. Interferometry is enabled by interfering two or more coherent light waves. When two light waves interfere, they generate fringes that can be detected by photodetectors or optical recording media. When one of the light paths is altered even slightly, then fringes move. Very small changes (much shorter than the optical wavelength) in distance produce detectable changes in the fringes. For example, a white light interferometric microscope can detect surface topography on the order of angstroms while using visible light with wavelength of hundreds of nanometers.
Digital Holography and Its Application in MEMS/MOEMS Inspection
Published in Wolfgang Osten, Optical Inspection of Microsystems, 2019
Wolfgang Osten, Pietro Ferraro
Wavefront distortion is a common problem in interferometric microscopy. It is solved by introducing the same curvature, using the necessary optical components, in both the interfering wavefronts. For example, the interferometer with Mirau configuration allows to compensate for the curvature.
Measurement Uncertainty in Manufacturing Metrology: Uncertainty Analysis on the Measurement of Single-Fiber, PC Endface Fiber-Optic Connectors
Published in NCSLI Measure, 2018
Mario O. Valdez, Edward P. Morse, Charles G. Stroup
There are a number of instruments that can provide information on the endface geometry within the required specifications, but only the interferometric instruments are considered. The interferometric microscope provides 3 D measurements of the surface through the use of light waves. This is the preferred measurement method as it provides immediate information on the entire surface of the fiber-optic endface. To ensure that the main focus of the research is on the measurement uncertainty of the fiber-optic endface, it is quickly noted that a phase shifting interferometer (PSI) was the instrument of choice. It is very important to know what type of instrument is used for the measurements, as each different type of interferometer has unique systematic error sources that contribute to the measurement uncertainty.
Improvement on thermal stability of TiAlSiN coatings deposited by IBAD
Published in Surface Engineering, 2018
Kang Su, Dameng Liu, Hua Pang, Tianmin Shao
A MicroXam surface-mapping interferometric microscope was used to examine the roughness (Ra) of the coatings in different annealing atmospheres. The Ra of the coating under nitrogen was 7.54 nm, which is much lower than that under argon (250 nm). As evident from the surface morphology in Figure 3(b), microcracks, which promoted oxygen entering the coating, occurred in the coating, leading to faster oxidation.