In fast particle-tracking systems, camera selection is critical because of the fast framing AND short exposure conditions. The frame rate of the camera is important and relatively easy to understand. The duration of a frame (essentially the reciprocal of the frame rate) determines the distance (in pixels) moved by the particle from one acquired frame to the next. If the frame rate of the camera is too slow, the inter-frame displacement may be larger than the field-of-view. In this case, a particle may be visible in one frame but it may be outside the Field of View (FOV) in the next frame.
Intra-frame motion blur
Another area of concern in particle-tracking is the intra-frame motion blur. In a camera, the duration of exposure determines how long photoelectrons are collected in pixels. If the object that is being imaged moves during the exposure, the reflected or scattered light from the particle moves spatially during exposure. This results in motion blur – for example, the particle may not appear at one location but as a blur.
One way to reduce motion-blur is to use a short exposure duration (implemented via electronic shuttering). This will be described in the next post.