Optical flats are single precision flat surfaces. They are used as reference surfaces to compare flatness of a substrate where flatness is unknown. When a high quality optical flat is placed on top of a polished substrate and used in conjunction with a monochromatic light source light bands are formed. The monochromatic light has a helium filled tube source which eliminates all colours except a “yellowish” orange. The light bands that are present are known as interference fringes and their shape represents how flat the part being tested measures. Dependent on how many rings are formed or how straight the presented lines are is an indication of how flat the tested part is. The rings present are called "Newton's rings" they are an interference pattern created by the reflection of light between two optical surfaces.
Optical flats are used for testing gauge blocks. Optical flats are also used in interferometers and high quality flat optical mirror and window sub-straights for laser applications.
Knight Optical offers a range of stock optical flats in single-sided Zerodur and Quartz, offering different stability and surface quality. Zerodur and quartz optical flats are also available in lambda/10 and lambda/20 from stock. Lamba/4, lambda/8 and lambda/16 flats are also available on short lead times.
All optical flats are tested on our Zygo Verifire XPZ interferometer system fitted with the latest Mx® software. Optical flats are supplied certified in a quality wooden box.
Knight Optical also offer a rework and calibration service for optical flats, please enquire.