The 850nm filter is a narrow bandpass optical device whose core function is to allow efficient transmission of near-infrared light with a central wavelength around 850nm while blocking interfering light from other bands. It achieves selective filtering of specific spectra through special coating processes and is widely used in scenarios requiring precise optical signal extraction.

Key Optical Specifications of 850nm Filters

• Central Wavelength (CWL): Mainstream specifications are 850±2nm or 850±5nm, determining the core transmission band of the filter, which must match the main peak of the light source.
• Full Width at Half Maximum (FWHM): Common ranges are from 30nm±2nm to 40±5nm, with some high-precision applications customizable down to 10nm. The smaller the bandwidth, the stronger the spectral selectivity.
• Transmittance: Peak transmittance generally reaches 85% or higher, with some products achieving up to 91%. High transmittance ensures efficient utilization of signals.
• Blocking Performance:
  • Blocking Range: Typically covers 200-810nm (front blocking) and 880-1200nm (rear blocking), with some products extendable to 200-1100nm.
  • Blocking Depth: Expressed as OD value (OD = -lgT). General applications require OD2 (transmittance ≤1%), while high-precision scenarios like fluorescence analysis demand OD4 (transmittance ≤0.01%).