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
) of the scanner's
. 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).