نوافذ دائرية عالية الجودة تجارية، زجاج بصري N-BK7*

I needed a few clear windows for a laser project, and the surface accuracy at ≤2λ per inch for the 6mm thick ones is spot on for my needs. They arrived well-packed and the edges are clean, no chips or scratches.

Ordered the 4.76mm version and the 2λ surface accuracy is genuinely impressive for the price. Interferometer showed a clean figure right out of the packaging, no edge chips or scratches. Using it as a replacement window in a laser setup and it's holding up perfectly.

I checked the diameter on a few of these and they all landed within the 0.125 mm spec, which is reassuring. Under a knife edge test the surface accuracy looks like it's holding to the 2λ per inch claim, nice and flat.