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How can a pulsed laser make a fast-moving object appear still in a hologram?

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hologram graphic — holography Figure 1: Gabor's original method for creating holograms.

A pulsed laser enables the capture of fast-moving objects by utilizing an extremely short, high-intensity flash of light, which effectively "freezes" the motion during the exposure.12

The process works because the pulse duration is incredibly brief—often less than 1/10,000,000 of a second. As long as the object moves no more than 1/10 of a wavelength of light during this interval, the resulting hologram remains sharp and usable. This is in contrast to a continuous-wave laser, which requires long exposure times and is therefore unsuitable for subjects in motion.1

Additionally, for objects undergoing periodic motion, such as a rapidly rotating turbine blade, stroboscopic techniques can be used to interrupt the laser light at the same frequency as the object's rotation. This makes the object appear stationary, allowing for the production of a clear hologram that reveals vibrational stress patterns.3