Timing is everything. Capturing extremely fast but inconsistent projectiles
Where an ultra high-speed camera is required to capture a ballistic event, the inherently short timescales and camera record durations can present a triggering challenge. This is particularly so if the projectile velocity is inconsistent, where even a 2% variation from the assumed velocity can mean the difference between capturing the event and missing it altogether.
To illustrate this, using an ultra high-speed camera such as Specialised Imaging’s KIRANA, operating at a moderate 2Million fps, the fixed number of 180 images provides a record duration of 90μS. Using a single trigger located 50cm from the target and assuming a nominal muzzle velocity of 350m/s, a 2% velocity variation could mean missing the first 28μs of the event, if travelling faster or capturing only the first 61μs of the event if 2% slower. Capturing at 7MHz reduces the record duration to 25.7μS where the whole event could be missed if the same 2% velocity variation occurred.
To accommodate potential velocity variations, the KIRANA camera has a built-in velocity measurement function as standard. This uses two external projectile detector inputs to calculate the projectile velocity in real time. The camera uses this calculation to adjust both camera and flash lamp triggering to coincide image capture and correct illumination at the time of interest. This feature significantly reduces the likelihood of missing unpredictable projectiles, which in turn reduces the potential number of repeated tests, inherent cost - and increased frustration.
Read the application note here: