A 820nm longpass filter is an optical component that selectively transmits near-infrared light with wavelengths longer than 820nm, while effectively blocking or cutting off shorter wavelengths below 820nm. 820nm longpass filters are widely used in Raman spectroscopy, fluorescence measurements, machine vision, IPL devices, biometric recognition, and specialty lighting. Their core function is to isolate near-infrared light from visible interference, improving detection accuracy, imaging quality, and treatment safety across these fields.
4.What is key parameter when choose for right Longpass Filter?
When selecting a Longpass Filter, normally the following factors need to be taken into consideration：
- Cut-Off Wavelength: it is one of the most important parameters, typically defined as the wavelength transmittance at 50% .
- Average or Peak transmittance: usually average transmittance ≥90%, higher transmittance e.g. 92% or 95% on average or specific single point need to definite and communicate with manufacturer, higher transmittance need to additional AR coating.
- Blocking rate: usually expressed in terms of optical density(OD), OD2-OD3 for standard and higher will be OD4-OD6 per requirement
- Angle of Incidence (AOI): AOI need to be consider as Interference Filter is angle sensitive, 0° AOI by default, other AOI e.g. 30/45° need to be specified.
- Physical and environmental requirement: Substrate type, dimensions and thickness, surface quality, and environmental durability.
Shenzhen Hengda Liyuan Optoelectronics introduced advanced optical technology that apply depositing nano materials through ion-assisted evaporation onto a multilayer hard film in a high vacuum environment which coating layer is firm and has good tightness, and small bandwidth drift. Liyuan optoelectronics have been focus on optical coating for more than 17 years and offer one-stop optical filters solution including Narrow Bandpass Filters, IR cut-off Filters, Longpass & Short Filters, Notch Filters, ND filters, Star filters and Optical sapphire block.
other Longpass filters in stock from Liyuan Optoelectronics: LP430 LP500 LP560 LP600 LP650 LP800, etc.
