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Length and Size
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
The basic principle of length measurement by interferometry is the comparison of a mechanical length (or a distance in space) against a known wavelength of light. Commonly, the optics is arranged such that the light beam double-passes the required length. Therefore, the measurement units are half-wavelengths, and the length being measured is expressed as l=(i+q)λ2,
Introduction to Optics
Published in Rajpal S. Sirohi, Introduction to OPTICAL METROLOGY, 2017
Metrology is the science and technology of making measurements and drawing significant conclusions from a set of data. Optical metrology uses light-based techniques for measurement. The majority of measurements involve length in one form or other and hence most of the techniques reported in this book will relate to length measurement. Besides, there are some physical parameters of direct relevance in optics and hence the techniques of measurement of these parameters will also be included in the text.
Differences in creep response of GBM cells migrating in confinement
Published in International Biomechanics, 2020
Ishan Khan, Loan Bui, Robert Bachoo, Young-Tae Kim, Cheng-Jen Chuong
Simultaneous recording of the front and posterior-end displacements from actively migrating cells showed near-zero displacement at the posterior-end, confirming that recorded front-end displacements arose from the creep response of the migrating GBMs at the application of aspiration pressure load, excluding the likely sliding movement of the cell in the channel (Figure 6A). Corresponding recording from GBMs in stationary group showed movement of the posterior-end due to lamellipodium shrank as shown in Figure 6B when p = −20 cmH2O. To look into its effect on the apparent measurement of aspiration length, we found an effective radii of R = 12 and Rshrink = 11.56 from digitized video images before and after pressure load application (see Figures 7A–8C). Using an average height of Havg= 1.5 for the lamellipodium adhering to the reservoir substrate (Bottier et al. 2011), we obtained an estimated volume loss of 16.5 due to lamellipodium shrink on 2D substrate, from which we calculated an effective aspiration length of 0.66 . It was subtracted from the apparent aspiration length measurement. Similar treatment was done for all cells in the stationary group as presented in Figure 4.
Highly sensitive optical length measurement by using a microwave photonic filter with multi-passband
Published in Journal of Modern Optics, 2019
Jianghai Wo, Jin Zhang, Tao Wang, Pengfei Du, Anle Wang, Sishi Li, Xiang Li, Haida Yang, Yalan Wang
In this paper, we propose and experimentally demonstrate a tunable multi-passband MPF for optical length measurement. By slicing the spectrum of a broadband source (BBS) with cascaded Mach–Zehnder interferometers (MZIs), optical taps with different wavelength spacing can be obtained. Then an optical finite impulse response (FIR) filter is simply constructed by modulating the interfered optical signal with a phase modulator and delaying the signal with a dispersion medium. In the experiment, at most eight passbands have been obtained and the frequency response of the MPF is investigated, as well as the optical length measurement. The variation of optical length of the MZI will change the wavelength spacing of the interference spectrum, which will lead the frequency change of the passbands. Thus the length measurement is simply converted into frequency measurement. By recording the frequency difference change between two passbands, a length measuring sensitivity as high as −2.420 GHz/mm is achieved. Moreover, the stability of the proposed MPF is investigated as well. According to the measuring results, the sensor is able to overcome the cross-sensitivity and may find the application in multi-parameter sensing.
Modelling Thermal Performance of Unloaded Spiral Strand and Locked Coil Cables Subject to Pool Fires
Published in Structural Engineering International, 2022
Scott Watson, Ben Nicoletta, Panagiotis Kotsovinos, Rwayda Al Hamd, John Gales
An analytical approach is used to identify the pitch angle. By taking manual measurements of experimental results,15 the angle of the strand relative to the horizontal is identified and used as the pitch angle. Since the cable elongates as the experiment progresses,15 only the first few frames are used to get an accurate length measurement. The pitch angle is verified to be the same for all underlying cable-layers. An example length measurement is shown (see Fig. 8). The length measurements and calculated pitch angles for each specimen are tabulated (see Table 2). Refer also to Supplemental Material A—Pitch Angle Measurements for measurements taken for each sample.