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Chronos User Discussion / Frame straddling for PIV
« on: October 02, 2023, 09:33:46 PM »
Hi, everyone,
I think this question has already been asked but nobody has answered it previously with an actual number (from my research). For a particle image velocimetry application, we typically use a double-pulse laser to capture two consecutive frames at an arbitrary interval to measure velocity of a cloud of particles. These lasers typically have two individually-controlled heads that each can send a short (20-200ns long) pulse of light. In these applications, we typically expose the camera frame for as long as possible and control the illumination timing to get velocity measurements. But all cameras have a finite time required to download the frame from the sensor to a buffer before starting exposing the next frame. This information is not provided anywhere I can find for the Chronos camera (both versions).
As an example, if you sample at 1000fps the time between frames is 1ms but the exposure has to be (1ms - download time) at most. Therefore, the time between laser 1 and laser 2 has to be at least (download time + pulse length). This technique is called frame straddling in the field and enables the use of "low speed" cameras for high speed flows where the inter-laser time can be as low as 1us for some flows (depending on speed and magnification).
Anyone that has this experience with the Chronos, could you inform what is the minimum "download time" possible? Have you done any tests? I just wanted to know that info before committing to purchasing it.
Thanks!
I think this question has already been asked but nobody has answered it previously with an actual number (from my research). For a particle image velocimetry application, we typically use a double-pulse laser to capture two consecutive frames at an arbitrary interval to measure velocity of a cloud of particles. These lasers typically have two individually-controlled heads that each can send a short (20-200ns long) pulse of light. In these applications, we typically expose the camera frame for as long as possible and control the illumination timing to get velocity measurements. But all cameras have a finite time required to download the frame from the sensor to a buffer before starting exposing the next frame. This information is not provided anywhere I can find for the Chronos camera (both versions).
As an example, if you sample at 1000fps the time between frames is 1ms but the exposure has to be (1ms - download time) at most. Therefore, the time between laser 1 and laser 2 has to be at least (download time + pulse length). This technique is called frame straddling in the field and enables the use of "low speed" cameras for high speed flows where the inter-laser time can be as low as 1us for some flows (depending on speed and magnification).
Anyone that has this experience with the Chronos, could you inform what is the minimum "download time" possible? Have you done any tests? I just wanted to know that info before committing to purchasing it.
Thanks!