Witness samples are exactly as their name implies — samples of optical materials and/or coatings. Companies use witness samples as “witnesses” to a coating run in the thin film coating process. Witness samples allow testing without handling the actual part, to ensure the coating process is accurate before moving forward with the optical component.
When testing, witness samples are often used to measure reflectivity, transmission, and polarization, as well as humidity, temperature, durability, and salt fog tests. Often the material is the same as the substrate material and is almost always the industry standard of roughly 1” (25 mm) in diameter. Tooling for the spectrophotometers is made to accommodate the standard size of witness samples.
At United Lens Company (ULC), we understand the importance of testing products before making considerable investments. That is why we offer reasonably priced witness samples in more than 180 different materials.
Why Order Witness Samples?
To make our customers’ shopping experience as simple and efficient as possible, ULC offers witness samples in every substrate material we use to manufacture our optical components: from fused silica and fused quartz, to Borofloat® and Pyrex, and every material in between – common and uncommon alike.
Cut from live production runs to ensure that they are of the same quality as our actual glass, witness samples from ULC are 25 mm in diameter and 3 mm thick — the industry standard size. Additionally, every witness sample comes with the material number laser etched on the side for easy identification.
When testing witness samples from ULC, you can expect flatness of less than 1 wave at 632.8 nanometers, surface quality in the area of 60/40, and clear aperture of 80% or greater.
Witness Samples from ULC
ULC turns 100 this year and, in an effort to improve for our customers, we have redesigned our online catalog with state of the art, fully integrated software to simplify the online ordering process. Visit our updated product catalog today to order the witness samples you need and learn more about our other diverse product offerings.