It's
fabricated by special blue glass (BG39 from Schott or equivalent).
The glass will absorb IR wavelength and let visible light
pass. It widely used for digital camara.
Specifications:
Material: blue glass (BG39 or equivalent)
Dimension: 2mm ~ 200mm
Square or round shape
Flatness: L/4
Surface Quality: 60-40
Parallelism: 3'
Volume production capability
Short delivery time
AR/AR
Coating Ravg<0.5%@visible wavelength is available.