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Flow Visualization
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2020
The synchronizer acts as an external trigger for both the camera(s) and the laser. While analogue systems in the form of a photosensor, rotating aperture, and a light source have been used in the past, most systems in use today are digital. The synchronizer, controlled by a computer, can dictate the timing of each frame of the CCD camera’s sequence in conjunction with the firing of the laser to within 1 ns (nanosecond) precision. Thus the time between each pulse of the laser and the placement of the laser shot in reference to the camera’s timing can be accurately controlled. Knowledge of this timing is critical as it is needed to determine the velocity of the fluid in the PIV analysis. Standalone electronic synchronizers, called digital delay generators, offer variable resolution timing from as low as 250 ps (picosecond, i.e., 10−12 second) to as high as several ms (millisecond). With up to eight channels of synchronized timing, they offer the means to control several flash lamps and Q-switches1 as well as provide for multiple camera exposures.
Flow Visualization
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2016
The synchronizer acts as an external trigger for both the camera(s) and the laser. While analogue systems in the form of a photosensor, rotating aperture, and a light source have been used in the past, most systems in use today are digital. The synchronizer, controlled by a computer, can dictate the timing of each frame of the CCD camera’s sequence in conjunction with the firing of the laser to within 1 ns (nanosecond) precision. Thus the time between each pulse of the laser and the placement of the laser shot in reference to the camera’s timing can be accurately controlled. Knowledge of this timing is critical as it is needed to determine the velocity of the fluid in the PIV analysis. Standalone electronic synchronizers, called digital delay generators, offer variable resolution timing from as low as 250 ps (picosecond, i.e., 10−12 second) to as high as several ms (millisecond). With up to eight channels of synchronized timing, they offer the means to control several flash lamps and Q-switches1 as well as provide for multiple camera exposures.
A four-channel ICCD framing camera with nanosecond temporal resolution and high spatial resolution
Published in Journal of Modern Optics, 2021
Yuman Fang, Minrui Zhang, Junfeng Wang, Lehui Guo, Xueling Liu, Yu Lu, Jinshou Tian
The schematic of the camera is depicted in Figure 1. The entire instrument is assembled in a unique setup that includes a mirror-based image splitter, four ultrafast time-gated intensified cameras, and all the electronic control units. The customized image splitter divides the incoming light homogeneously into the individual channels without compromising resolution and imaging quality. The very core of the intensified camera system is the image intensifier tube and its associated electrical high voltage pulse generator. The photocathode of the image intensifier is gated by high voltage pulses with a large adjusting range from 3 ns to D.C. operation. The phosphor screen of the image intensifier is coupled to a commercial Lt665R camera based on a monochrome Sony ICX694 CCD sensor. The output bit depth and the physical interfaces are 14-bit and USB 3.0, respectively. The optical coupling device is a designed coupling lens, which increases both the spatial resolution and transmission compare with the fiber-optic taper. The pulse width and delay time of the pulse modules are controlled by the digital delay generator (DDG), an FPGA based module. When triggering occurs, the DDG generates the pulse sequence for the CCD camera trigger and, after precisely programmable delays, for the image intensifier photocathode gating. The intensified CCD (ICCD) channels are fully remote controllable by electronics. This allows highly accurate timing control to capture ultra high speed phenomena. The working sequence diagram is shown in Figure 2.