These sights are optical or computing sights that reflect a reticle image
on a combining glass for superimposition on the target; they are most commonly available as non-magnifying sights.
With Numerical's Virtual Stepper technology, Etec's ARIS100i systems can analyze a reticle image
under simulated lithographic conditions, allowing customers to predict whether a defect is likely to be reproduced on a wafer, thus saving both time and wafer costs.
The reticle image
must be extremely precise and defect-free, because the pattern on the reticle is critical to the performance of the IC product.