Wide-passband filter transmitting a broad red window (372 – 711 nm) with steep edges and deep blocking on both sides for clean spectral isolation.
BH-A20 Bandpass Extended delivers Passband 372 – 711 nm, Bandwidth (FWHM) ~751 nm, and Centre wavelength ~724 nm (nominal).
The hard-oxide coating is built for repeated handling, heat, and cleaning.
Best suited for:
Near-infrared imaging and sensing applications — including silicon-sensor camera systems, LIDAR receivers, and night-vision optics — where the wide NIR passband maximises signal collection across the sensor's peak sensitivity range
The BH-A20 is a broadband absorptive black coating on optical glass, engineered to attenuate light across a wide spectral range while providing minimal spectral distortion. With peak transmission of 94.1 % at 470 nm and sustained >80 % transmission from 366-1200 nm (Blue: 94 %, Green: 93 %, Red: 88 %, NIR: 79 %, SWIR: 77 %), the BH-A20 functions as a neutral-density-like filter with gradual roll-off toward longer infrared wavelengths. The broadband absorption characteristics make the BH-A20 ideal for reducing stray light, eliminating internal reflections, and attenuating high-intensity beams without introducing spectral color shift. This specification provides an absorptive alternative to reflective coating approaches.
Integrate the BH-A20 Black Coating into your optical system for broadband stray light elimination with rapid prototyping and production capability.
BH-A20 is a Black Coating. The BH-A20 is a broadband absorptive black coating on optical glass, engineered to attenuate light across a wide spectral range while providing minimal spectral distortion. With peak transmission of 94.1 % at 470 nm and sustained >80 % transmission from 366-1200 nm (Blue: 94 %, Green: 93 %, Red: 88 %, NIR: 79 %, SWIR: 77 %), the BH-A20 functions as a neutral-density-like filter with gradual roll-off toward longer infrared wavelengths. Common uses include Stray Light Elimination, High-Intensity Beam Attenuation, Neutral Density Filtering, and Optical System Optimization.
Key published specs for BH-A20 include Passband: 372 – 711 nm; Bandwidth (FWHM): ~751 nm; Centre wavelength: ~724 nm (nominal); Passband transmittance: ≥ 84.8 % T (± 9.3 % ripple); Short-wave edge (T50): ≈ 349 nm, ~72 nm steepness.
BH-A20 is commonly used for Stray Light Elimination, High-Intensity Beam Attenuation, Neutral Density Filtering, and Optical System Optimization. Stray Light Elimination - Internal black coatings in optical instruments suppress scattered and reflected light that would reduce image contrast and detection sensitivity.
KUPO lists the construction for BH-A20 as Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick. Published custom options include Edge shifting, passband widening/narrowing, asymmetric blocking, rapid prototypes. Custom Format Flexibility - Round, square, and free-form geometries from 5-450 mm with Borofloat, soda-lime, Schott D263 T, and Corning Eagle XG substrate options.
The published angle of incidence for BH-A20 is 0° (normal incidence); custom angles available. The hard-oxide coating is built for repeated handling, heat, and cleaning.