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Measuring MEMS in Motion by Laser Doppler Vibrometry
Published in Wolfgang Osten, Optical Inspection of Microsystems, 2019
Christian Rembe, Georg Siegmund, Heinrich Steger, Michael Wörtge
A stroboscopic video microscope measures in-plane motions of periodically moving structures with stroboscopic machine vision and can measure frequencies as high as 1 MHz [29]. The camera used in these kinds of detection systems usually has a CCD sensor for video frame rates and not a high-speed detector and, therefore, the stroboscopic principle has to be applied to visualize rapid motions. An LED has been proven to be a reliable solution for the light source that ensures constant illumination power of the strobe pulses. The pulse width of the strobe flash defines the time resolution because the camera is not rapid enough to capture very short events. The CCD sensor collects no light when the strobe light is off. Therefore, events can be recorded with a period time even shorter as the shortest possible exposure time of the camera.
Flow Phenomena in Post-Dryout Heat Transfer
Published in G. F. Hewitt, J. M. Delhaye, N. Zuber, Post-Dryout Heat Transfer, 2017
Photographic observation of the hydrodynamic behavior within the test section can be accomplished with both still photography and high speed motion pictures. Still photographs are taken with a 35 mm camera. Lighting comes from a 3 μs strobe light. This short exposure time allows small (~0.1 mm) droplets traveling at high speeds (about 10 m/s) to be observed. The strobe light is bounced off a white background, to provide backlighting of the test section, and the strobe/background unit can traverse the length of the test section. The still camera is mounted in front of the Lucite view port, on a mount which is tied to the motion of the strobe/background. Motion pictures are taken on a variable speed (100–10,000 fps) Photec IV camera, using VNX 430 film and four 450 W flood lights. The flood lights are directed onto the same background used for still photography, to again backlight the test section.
Lights
Published in David Wyatt, Mike Tooley, Aircraft Electrical and Electronic Systems, 2018
A high-intensity white flash is produced from a: (a) strobe light(b) fluorescent tube(c) landing light.
Assessment of the degree of damage in structural materials using the parameters of structural acoustic noise
Published in Nondestructive Testing and Evaluation, 2023
A. A. Khlybov, A. L. Uglov, T. A. Bakiev, D. A. Ryabov
When a command to start work is received from the processor module, the control device starts a strobe light (2), which, according to the stable time stamps of the quartz oscillator (1), generates a series of pulses to start the analog-to-digital converter (8). At the same time, the probing pulse generator is started. The probing pulse formed with a given duration after the power amplifier is fed through the external connector of the measuring module to the converter. The converter converts an electrical pulse into mechanical vibrations that excite elastic pulses in the object of control (IV). Elastic pulses that have passed through the object of control due to the piezoelectric effect create electrical impulses that arrive at the pre-amplifier. From the pre-amplifier through an adjustable amplifier, the signals are transmitted to the analog-to-digital converter. Through the input/output device, the digital code is transmitted to the processor module. The processor module receives the digital code, converts it and displays visual information about the shape of reflected pulses on the screen. The calculation of the time intervals and the values of the pulse spans is performed programmatically.
Custom-made 3D printed masks for children using non-invasive ventilation: a comparison of 3D scanning technologies and specifications for future clinical service use, guided by patient and professional experience
Published in Journal of Medical Engineering & Technology, 2021
Matt Willox, Peter Metherall, Avril D. McCarthy, Katherine Jeays-Ward, Nicki Barker, Heath Reed, Heather E. Elphick
The two scanning systems selected following the searches and laboratory testing for consideration by the user groups were the static photogrammetry system (3dMD Body) and the best-performing hand-held scanner (Artec Spider). There was mixed opinion about whether the fixed frame of the 3dMD scanner would be a problem. Some felt that it would be frightening as it looked similar to other equipment they had experienced whilst others thought its familiarity was a positive. The 3dMD Body was selected on the basis if cost and availability and it was explained to participants that the 3dMD Head system, if used, would have been smaller and therefore require less space. It was felt that the flashing strobe-light effect of the Artec scanner may be a problem for children with epilepsy or autism (due to level of sensory stimulation) and the movement around the head of the scanner may result in them turning their heads to either avoid or track it. A constant light source may be more acceptable but still may result in movement.
Online droplet monitoring in inkjet 3D printing using catadioptric stereo system
Published in IISE Transactions, 2019
Tianjiao Wang, Chi Zhou, Wenyao Xu
Based on the droplet location detection results, the droplet’s velocity can be readily detected. As discussed in Section 3.1, the strobing system is used to capture the droplet image at a certain location determined by the synchronized control signal. Images at different locations can be captured by adjusting the delay time between the synchronized signals for the strobing LED and piezo printhead (Wang, Kwok & Zhou, 2017c). The droplet’s velocity can be derived based on the distance between the two different locations and the corresponding delay time as follows:where the V is the velocity of the droplet, is the elapsed time between two different detected droplet-locations at t1 and t2, is the detected droplet location at t1 and is the detected droplet location at t2. In our experiment, after the first droplet location was detected, the delay time of the strobe light was increased from 400 µs to 700 µs. The droplet speed can be calculated as the difference of the droplet locations during the 300 µs period. To show the speed changes, we varied the drive voltage applied to the piezo printhead, from 40 V to 44 V, the relation between the droplet speed and the applied voltage is shown in Figure 12.