Speckle-free laser marking of metals using liquid-crystal-based spatial light modulator

Krystian Lukasz Wlodarczyk, Jarno J. J. Kaakkunen, Pasi Vahimaa, Duncan Paul Hand

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Abstract

A liquid-crystal-based spatial light modulator (LC-SLM) is used for laser beam patterning and manipulation in order to produce very small, speckle-free 2D marks on metal surfaces. To avoid speckles within the laser marked area, which is a typical drawback of current SLM-based laser marking processes, an array of “non-interfering” beamlets is produced by the LC-SLM and used for generating micro-patterns. The micro-patterns (e.g. 20×20 pixel datamatrices with overall dimen-sions of less than 320µm by 320µm) are generated in a series of 16 steps, using a Fresnel zone lens (FZL) which is written into a computer-generated hologram (CGH) that produces an array of beam-lets. By shifting off-axis the whole kinoform (FZL+CGH) for each step, the array of beamlets is spatially moved along the imaging plane, producing the required micro-pattern. In comparison to 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.
Original languageEnglish
Publication statusPublished - 2013
Event14th International Symposium on Laser Precision Manufacturing - Japan, Niigata, Japan
Duration: 23 Jul 201326 Jul 2013

Conference

Conference14th International Symposium on Laser Precision Manufacturing
CountryJapan
CityNiigata
Period23/07/1326/07/13

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    Wlodarczyk, K. L., Kaakkunen, J. J. J., Vahimaa, P., & Hand, D. P. (2013). Speckle-free laser marking of metals using liquid-crystal-based spatial light modulator. Paper presented at 14th International Symposium on Laser Precision Manufacturing, Niigata, Japan.