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Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
An optical flat is an optical element in disk shape with a flat measurement surface, made of optical glass or silica glass, and is used for flatness measurement of an optically polished surface or precision finished surface, such as a block gauge, using light wave interference. Measurement surface of the optical flat is placed on the measurement object surface to generate interference fringes. These fringes are referred to as Newton ring, and flatness is obtained from the number of these fringes considering that the interval of fringes is 1/2 of wavelength λ. The poorer the surface of the measurement object, the more fringes are generated, and if the surface is distorted, fringes are also distorted. With a desirable surface, interference fringes are in unicolor, and the flatness F is obtained from the ratio of the amount of bending a with regard to the center distance of interference fringes b, while one end of the optical flat is used as the contact and the other end is floated to generate parallel interference fringes, as shown in Figure 4.15. F=λ2×ba
RLG coatings – characterization and optimization for improving laser damage threshold, and losses
Published in Khaled Habib, Elfed Lewis, Frontier Research and Innovation in Optoelectronics Technology and Industry, 2018
An optical flat is an optical-grade piece of glass lapped and polished to be extremely flat on one or both sides, usually within a few millionths of an inch (about 25 nanometres). They are used with a monochromatic light to determine the flatness of other optical surfaces by interference.
General-Purpose Abrasive Machine Tools
Published in Helmi Youssef, Hassan El-Hofy, Traditional Machining Technology, 2020
This is the most effective lapping method for hard metals and other hard materials. It is used to produce optically flat surfaces and accurate surface plates. When both sides of a flat WP are lapped simultaneously, extreme parallelism is achieved.
Flatness measurement of large flat with two-station laser trackers
Published in International Journal of Optomechatronics, 2018
Jie Li, Jie Yang, Shibin Wu, Xuedong Cao
The flatness measurement of components for precision optomechanical systems has become increasingly challenging for the following reasons. The components, in addition to being larger, are tested in the workshop, and required accuracy is more stringent. For example, the flatness of optical flat is 10–20 µm (PV, Peak-to-Valley) during the fine grinding process. Another example is the flatness of contact surface of telescope’s turning table needs figuring to 20 µm (PV).
Development of a multipoint liquid film sensor using an optical waveguide film on simulated fuel rod of BWRs
Published in Journal of Nuclear Science and Technology, 2023
Hajime Furuichi, Kenichi Katono, Kiyoshi Fujimoto, Kenichi Yasuda, Kazuaki Kito
Our purpose in this study was to develop a measurement method for liquid film thickness on a simulated fuel rod by using an optical waveguide film (OWF). The OWF is a flexible polyimide film in which several optical paths (called cores) are included. As micro mirrors located in the core ends reflect propagated light vertically to the OWF, the micro mirrors can be applied to liquid film sensors. Thus, the OWF is easily installed on the curved wall as a wall-embedded sensor. Furthermore, multiple measuring points can be prepared by designing the core trajectories. In this study, we manufactured the OWF embedded in the simulated BWR fuel rod. First, we conducted a calibration test using an optical mirror instead of an air-water interface. Intensities of the output light from the OWF were evaluated at different static water thicknesses between the optical flat mirror and the sensor surface of the OWF. We confirmed the calibration method of the liquid film thickness by comparing test results with results obtained with a theoretical model. Second, we confirmed a signal processing method by conducting an application test of the liquid film measurement. Because calibration results of the OWF are applicable for the horizontal surface of the liquid film, influences of surface angle on the output signal should be extracted through signal processing. In the application test, output signals of the OWF were calculated from random waves simulating a time-series liquid film. We confirmed that peaks of the output signal indicated the liquid film passing through the sensor had a flat surface. Finally, we demonstrated measurement of the liquid film thickness in a vertical annular flow under atmospheric pressure conditions. The time-series thickness on the simulated fuel rod was measured by the OWF. Simultaneously, the liquid film flowing through a square acrylic channel on the OWF was visualized by a high-speed camera filming through a transparent wall of the channel. Measurement errors of the thickness measurement were discussed by comparing results from the OWF to those from the visualization. Furthermore, wave velocities of disturbance waves and ripples were measured by two sensors of the OWF and those results were also compared with the visualization results. Consequently, we confirmed applicability of the OWF for measurement of the liquid film thickness distribution.
Enhanced Dual Confocal Measurement System
Published in Fusion Science and Technology, 2018
K. Tomlinson, C. T. Seagle, H. Huang, G. E. Smith, J. L. Taylor, R. R. Paguio
All instrument motion as well as data acquisition and analysis are controlled through a custom Windows application (Fig. 3). The following are the operational steps for specimen measurement: Specify the measurement locations. To facilitate this, the user interface presents built-in strategies for simplified definition of uniformly distributed locations within user-defined circular and rectangular areas since these are very common specimen shapes. Alternatively, specific x-y coordinates may be input or read from a file to accommodate special tasks and geometries.Install and measure the optical flat (optional). The operator is prompted to install the optical flat which is semipermanently mounted in its own fixture. If only thickness is to be measured this step is omitted by first checking a thickness-only box in the user interface. Upon operator command, the optical flat is measured at the x-y coordinates just defined, automatically creating the flatness compensation map (see Sec. IV.B).Install and measure the specimen (with automatic thickness calibration and verification). The operator is prompted to remove the optical flat (if present) and replace it with the specimen which has been previously installed into its holding fixture off-line. The operator is also prompted to input the nominal specimen thickness. Upon operator command, the instrument automatically positions the calibration standard of nearest thickness between the sensors and performs the thickness calibration, then measures the specimen at the defined locations, and then, finally, automatically measures the standard of next-nearest thickness to provide verification. An option is also presented to remeasure the specimen so repeatability of thickness data can be assessed.Confirm flatness calibration (optional). The software prompts for remeasurement of the optical flat as a means of confirming accuracy of the flatness compensation map if desired.Output and store data. Upon completion of measurements, flatness and thickness results are automatically output in numerical and graphical form within the software’s user interface. Numerical data are stored in ASCII format suitable for export into Excel or other third-party data analysis/display applications.