Optical Devices Comprising Microlenses and Laser-Fabricated Patterns or Structures, Their Manufacture and Use

Disclosed are optical devices suitable as security devices for document authentication, which comprise at least one array of patterns such as laser-fabricated patterns, or other structures, optionally formed for example from elongate laser-modified tracks extending within a document substrate. The patterns are combined with at least one array of microlenses to cause certain optical effects. Also disclosed are the use of such devices for document authentication, and methods for their production.