Led Handheld Stroboscope

In electronic versions, the perforated disc is replaced by a lamp capable of emitting brief and rapid flashes of light. Typically a gas-discharge or solid-state lamp is used, because they are capable of emitting light nearly instantly when power is applied, and extinguishing just as fast when the power is removed. By comparison, incandescent lamps have a brief warm-up when energized, followed by a cool-down period when power is removed. These delays result in smearing and blurring of detail of objects partially illuminated during the warm-up and cool-down periods. For most applications, incandescent lamps are too slow for clear stroboscopic effects. Yet when operated from an AC source they are mostly fast enough to cause audible hum (at double mains frequency) on optical audio playback such as on film projection. The frequency of the flash is adjusted so that it is an equal to, or a unit fraction of the object's cyclic speed, at which point the object is seen to be either stationary or moving slowly backward or forward, depending on the flash frequency