Optical Flats

24 Mar 2023

Knight Optical has been providing our customers with precision optical flats for decades, either from our stock catalogue as a quick solution, or custom optical flats manufactured to the customers’ requirements.

Optical Flats are primarily used as a reference surface to determine the flatness of an unknown work surface. With one, or two, surfaces that are precision polished with a high-quality surface finish, these optical components are typically manufactured from materials with a low coefficient of thermal expansion (CTE), which offer homogeneity and durability.

However, these precision polished optics have many uses in industries such as aerospace, research, and defence, not as reference flats but as optics with a highly polished surface which can then be coated, for example a mirror coating, to be used in applications such as telescopes.

Our vast stock catalogue of fused quartz and Zerodur components come in diameters ranging from 26mm to 303mm and are either single- or double-sided with precision flatness specifications of lambda/10 or lambda/20. Below are the manufacturing tolerances:

Diameter - < 10mm to 600mm+

Thickness - ± 1mm

Flatness @ 633nm - Over 90% aperture

Parallelism - < 5 arc minutes

Scratch/dig - < 60/40

Knight Optical can also provide custom optical flats which are manufactured to your own specifications, whether that is differing materials, dimensions (including square/rectangular flats), tolerances and flatness specifications. Below are our custom capabilities:

Diameter - < 10mm to 600mm+

Flatness @ 633nm - Up to λ/20 @ 633nm

Parallelism - < 5 arc minutes

Scratch/dig - < 60/40

Typical coatings - AR and Mirror types available

Coatings can be applied to an optical flat, including a mirror coating to enable it to be used a reference mirror. The rear surface can also be diffused if necessary.

Both our stock and custom optical flats come supplied with a wooden box to ensure the optics is protected against damage.

Knight Optical also stock monochromatic light units which can be used in conjunction with an optical flat, our two bench top units use a low pressure sodium light source working at 589nm.

With a metrology laboratory and dedicated QA department, Knight Optical test all optical components against their specification to ensure they are met. This includes using our Zygo Verifire XPZ Interferometer to verify the surface flatness of all optical flats before they are sent to our customers.  

For further information on how optical flats work and Knight Optical’s capabilities, please read our blog post where we put Optical Flats in the Spotlight.

Contact our UK and US sales team for further information and help with your enquiries.