Holographically encoded elements for microarray and other tagging labeling applications, and method and apparatus for making and reading the same

An optical arrangement for writing a different code on or in each of a plurality of optical elements, comprising:

• a light source for providing a reference beam;
• and
• a spatial light modulation device having an n-dimensional code configured thereon that responds to a signal beam for providing a spatial light modulation signal containing the n-dimensional code;
• the spatial light modulation device and the light source being arranged in relation to the optical element so that an interference pattern generated between the spatial light modulation signal and the reference beam is written on or in the optical element as a holographic image of the n-dimensional code, wherein the optical elements comprise microbeads or a substrate that is processed to produce microbeads.