Central wavelength 809nm+/-2nm, precise control of central wavelength
Half bandwidth 40+/-4nm, covering the wavelength range of 789–829nm, allowing a wider range of optical signals to pass through, suitable for scenes with slight wavelength offsets of the light source or requiring multi-wavelength compatibility
The transmittance in the passband is greater than 90%, and the light energy loss in the passband is extremely low, suitable for weak light signal detectors
Outside the passband, the cut-off depth OD4 in the range of 200-1200nm, effectively blocking ultraviolet, visible light and long-wave infrared interference

809/40nm Bandpass Filter Optics Technical Datasheet

Parameter	Specification
Center Wavelength (CWL)	809 nm ± 2 nm
Full Width at Half Maximum (FWHM)	40 nm ± 4nm
Peak Transmission	≥ 90%
Blocking Range	200 – 1200nm
Optical Density (OD)	OD4
Angle of Incidence (AOI)	0°
Clear Aperture	>90% of the diameter
Substrate Material	UV Fused Silica, K9,sapphire, Other optical glass
Size	Ø12.7mm, Ø25.4mm,Ø50.8mmor customizable
Environmental Durability	Compliant with MIL-STD-810G
Other avaliable wavelength	809/10nm, 809/20nm
Custom Option	EUV to 30,000nm
Filter Type	Multilayer Interference Bandpass Filter
Coating Technology	Ion-Assisted Deposition (IAD), Hard coated
Surface Quality	80-50, 60-40, 40-20 (per MIL-PRF-13830B

809/40nm Bandpass Filter Optics Applications

Industrial Automation
Industrial production lines need to quickly identify surface defects of materials, but ambient light and stray light reflected by materials will interfere with detection accuracy, resulting in a high rate of misjudgment. The 809/40nm filter allows the 789–829nm band to pass through, shielding stray light in other bands to ensure that weak defect signals are transmitted to the detector without attenuation.
Biomedical
Blood oxygen detection relies on the difference in absorbance after near-infrared light penetrates the skin, but skin tissue and other biological molecules will reflect multi-band stray light, interfering with signal purity. The 809/40nm filter only allows the 789–829nm blood oxygen characteristic wavelength to pass through, shielding the reflection noise of other biological molecules. Reduce blood oxygen saturation measurement errors
Environmental monitoring
Water turbidity detection requires measuring the scattering intensity of suspended particles to 809nm laser, but natural light and impurities in water will introduce background noise, affecting data reliability. This filter can filter out non-target bands and retain only the 789-829nm scattered signal
Agricultural sorting
The difference in reflectance spectra between foreign matter mixed in grains, such as stones, moldy grains and healthy grains, is concentrated in the near-infrared band, but it is difficult to accurately distinguish them under natural light. This filter can focus on the 789-829nm band to amplify the difference in reflectance between foreign matter and grains, such as the absorption peak of moldy grains is around 809nm.