Many of the more capable AOI systems use LED lighting to illuminate the inspection area's field of view (FOV). LEDs however are subject to manufacturing tolerances and this can cause variable levels of lighting in operation.
One way of dealing with this is to ensure careful selection of LEDs to ensure consistent performance. This method is costly and does not in itself guarantee consistency. It can be effective to some extent but does not yield consistent performance from one machine to another, making it virtually impossible to transfer inspection programs between machines without major adjustments.

A smarter solution is to ensure that the inspection algorithm is designed take into account possible variations and to compensate for the variability of LED characteristics. This facilitates easy transfer of programs from one machine to another and also offers the possibility of providing replacement lighting systems with optimal performance when required.
Tolerant algorithms coupled with fast and easy optical calibration routines ensure homogeneity in the field of view (FOV) and consistent machine-to-machine performance.
This paper describes how to achieve this consistent performance.