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Optical Flats

Full Range Optical Flat Solutions

For more than 50 years, Advanced Optics has taken great pride in manufacturing high quality optical flats. Our extensive inventory of optical flats is available in a wide variety of accuracies (λ/4, λ/10 and λ/20) Our vast array of in stock materials, paired with our years of experience allows us to meet the most challenging and exacting applications.

In addition to our large selection of in stock optical flats, Advanced Optics offers custom optical flats, as well as free engineering services. Our capabilities include custom shapes, apply bevels and even drill holes. We are here to meet your needs.

The term optical flat is also commonly referred to as “test plates” or “reference flats”. An optical flat is a piece of glass that has been precision polished to a specific flatness on one or both sides. Optical flats may be used as a reference (test plate) against which the flatness of an unknown surface can be compared. The term “Optical Flat” is often used interchangeably with other optical components such as optical windows and as a substrate for optical mirrors.


  • In stock optical flats precision polished up to 8 inches in diameter.
  • Ability to polish up to 12 inches in diameter.
  • Accuracy of λ/4, λ/10 or λ/20 available, many in stock for immediate shipment.
  • Every optical flat comes with a Certificate of Calibration traceable to the NIST.
  • Extensive stock of raw materials available in-house for fast turnaround.
  • In stock optical flats uncoated with the option of adding an anti-reflective coating.
  • Custom fabrication available including custom sizes, shapes, holes, bevels and coatings.
  • Optical flat resurfacing with a fast turnaround.
  • Each optical flat may be ordered with it's own finely crafted storage case.

Optical Matericals Available

Advanced Optics carries an extensive stock of raw materials including:

View our in stock single and double sided fused silica optical flats below:

Surface Accuracy: Single or Double Sided Flat Diameter Fused Silica (Thickness)
λ/20 (0.000001") 25.4 (1") 12.7 (1/2")
λ/10 (0.000002") 25.4 (1") 12.7 (1/2")
λ/20 (0.000001") 50.8 (2") 15.9 (5/8")
λ/10 (0.000002") 50.8 (2") 15.9 (5/8")
λ/20 (0.000001") 76.2 (3") 15.9 (5/8")
λ/10 (0.000002") 76.2 (3") 15.9 (5/8")
λ/20 (0.000001") 101.6 (4") 19.1 (3/4")
λ/10 (0.000002") 101.6 (4") 19.1 (3/4")
λ/20 (0.000001") 127 (5") 19.1 (3/4")
λ/10 (0.000002") 127 (5") 19.1 (3/4")
λ/20 (0.000001") 152.4 (6") 25.4 (1")
λ/10 (0.000002") 152.4 (6") 25.4 (1")
λ/20 (0.000001") 203.2 (8") 33.8 (1.33")
λ/10 (0.000002") 203.2 (8") 33.8 (1.33")

The accuracy of each optical flat is traceable to the National Institute of Standards and Technology.

Corning Incorporated Data SheetFused Silica Technical Data Sheet from Corning Incorporated (pdf)

Optical Flat Interpretation

Optical Flats, stock or custom

Double Surface Optical Flat/Optical Windows

Advanced Optics offers in stock fused silica double sided optical flats that may also be used as optical windows. Fused silica offers superior transmission characteristics, a high degree of purity, exceptional environmental durability and a low coefficient of thermal expansion.

Dual Surface Optical Flats/Optical Windows are an excellent choice when an optical system requires separation between two environments while passing a specific wavelength(s) of light or for demanding interferometry requirements.

Whether you require custom optical fabrication or one of our many off-the-shelf flats, call today for a competitive quote!

Flatness Error of One Fringe
(1/2 wave)
(top view of optical flat)
optical flat top view a
Test Piece
Perfectly Flat
(top view of optical flat)
optical flat top view b

Optical flat interpretation and additional information, including how to select the best optical flat for your application can be on our Optical Flat Technical page.

Have a question? Give us call and tell us about your project. (262) 548-1155