SCANPEDIA

Glossary

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Here you'll find explanations and definitions of key technical terms from the fields of optics, scanner technology, laser technology and laser processing.

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D

Dither

Dither is positioning noise of the scan mirrors in the time range of a few milliseconds.

Independently of their activated motion, scan mirrors oscillate irregularly across a broad frequency spectrum from roughly 200 Hz to 20 kHz. The excursion magnitude is specified as the standard deviation σ (or RMS) of the scanner's optical angle. The resulting maximal amplitude can be approximated as 3σ.

In high-speed vector applications, dither effects during laser marking can produce irregular waves and spikes. At lower vector speeds, oscillations get concealed by overlapping laser pulses, but a slight broadening of marking occurs. This same broadening is also visible when a line is rewritten. Likewise, jump-and-shoot applications with short single pulses are susceptible to dither-induced imprecision. For long or repetitive pulses, dither broadens the effective beam or working diameter.

Systems with low dither

Special tunings (micro-machining) are available for applications requiring low dither amplitudes. The lowest dither is achieved using systems with digital encoders (se and de systems).