Laser direct writing of micro-OVD with low frequency templates

A laser direct writing way of micro-optical variable device with low frequency templates is proposed. The template is composed of 6×6 unit figures. The unit structure on the template is inputted by the spatial light modulator (SLM), exposed on photo-resist plate through the projection optical system section by section. micro-OVD with various complicated design and characteristics can be made by controlling the direction of the unit structure on the template. In order to achieve the achromatic effect of micro-OVD, a directional random speckle structure template base on the low frequency template was designed. The SVG-LDW04 laser direct writing system, whose typical phase structure is (4～100) microns, is adopted to fabricate the micro-OVD. The mentioned method does not use mechanical rotation device to change the direction of unit template, provides a novel and convenient way to fabricate the micro-OVD′s.