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Optical Flats
Advanced Optics has taken great pride in manufacturing the highest quality optical flats available for over 50 years. We maintain an extensive inventory of optical flats 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.
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.
SINGLE AND DOUBLE SIDED OPTICAL FLAT SPECIFICATIONS:
- 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.
Fused Silica Technical Data Sheet from Corning Incorporated (pdf)
Optical Flat Interpretation

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!
(1/2 wave)
(top view of optical flat)

Perfectly Flat
(top view of optical flat)

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
- Optical Mirrors
- AlSiO Economy Optical Mirror
- Bare Al Optical Mirror
- Borosilicate Optical Mirror
- Custom Optical Mirror
- Front Surface Optical Mirrors
- Fused Silica Optical Mirror
- Precision Grade Optical Mirror
- ZERODUR® Optical Mirror
- Precision Round Optical Mirrors
- Precision Rectangle Optical Mirrors
- Precision Square Optical Mirrors
- λ/4 Optical Mirrors
- Standard 1" x 1", λ/4 Optical Mirror
- λ/10 Optical Mirrors
- λ/20 Optical Mirrors
- Optical Flats
- Single Sided Optical Flat
- Double Sided Optical Flat
- Custom Optical Flats
- Optical Flat Resurfacing
- Optical Windows
- Custom Optical Window
- Commercial Grade Optical Window
- Precision Grade Optical Window
- Fused Silica Optical Window
- N-BK7 Optical Window
- λ/20 Optical Window
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P.O. Box 117, Pewaukee, WI 53072-0117, USA
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(262) 548-1155
Fax (262) 548-1153