= Fluorescent microsphere
= Fluorescent bead
{synonym}
A <fluorescent microsphere> is a small spherical particle containing or carrying fluorescent material. Excitation light produces a detectable emission signal, allowing the particle to serve as a tracer, positional marker or <calibration> object.
For imaging resolution <measurements>, the bead should be small relative to the instrument's <point spread function>; otherwise the recorded image includes the bead's finite size as well as the optical blur. In flow <experiments>, its motion tracks the fluid only when buoyancy, inertia and surface interactions do not materially bias the trajectory. The same bright signal can therefore support different <measurements> with different assumptions.
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