Accurate filter positioning is essential to eliminate imaging errors that can affect the optical performance of the micrsocope and add uneccessary variations to measurement results. The LEP filter wheel is driven by a DC servo motor specifically selected for smooth, quiet, damped wheel motion. Flexibility and expandability is assures with the MAC 5000/6000 controller system. The modular controller provides high performance and flexibility. Furthermore it is widely supported by almost any available imaging software application.