An approach for laser marking surfaces using a liquid–crystal-based spatial light modulator (LC-SLM) for beam patterning and manipulation is presented, designed to avoid the speckle interference problem which is a typical drawback of current SLM-based laser marking processes. In our approach, the LC-SLM is used to generate complex two-dimensional micropatterns (e.g., 20 × 20 datamatrices) with overall dimensions of < 320 by 320 μm. The micropatterns are generated in a series of 16 steps, using a Fresnel zone lens (FZL) combined with a computer-generated hologram (CGH); for each step the whole kinoform (FZL + CGH) is spatially shifted off-axis by a different amount of pixels to build-up the required pattern. In comparison with other SLM-based laser marking approaches already reported in the literature, our method not only eliminates (or at least significantly reduces) unwanted speckle interference but also reduces the laser power required for marking.
|Journal||Applied Physics A: Materials Science and Processing|
|Early online date||12 Dec 2013|
|Publication status||Published - Jul 2014|