Negative filterAlso known as notch filter, band stop or band suppression filter, it is a type of interference filter whose core function is to pass through the majority of wavelengths of light while attenuating light within a specific wavelength range (stopband) to a low level.

　　Negative filterTypical application scenarios:

Laser protection

532nm green laser protection: In laser processing and medical beauty (such as freckle removal and vascular treatment), it protects the eyes of operators from high-intensity green laser damage.

1064nm infrared laser protection: used as an observation window for laser welding, cutting and other equipment to prevent visual damage caused by infrared laser reflection or scattering.

Spectral analysis instrument

Raman spectrometer: filters out stray light from the excitation light source, improves the signal-to-noise ratio, and ensures the accuracy of Raman peak detection.

Fluorescence microscope: blocks the excitation light band, allowing only fluorescence emission light to pass through, improving imaging contrast.

Biomedical Systems

Flow cytometry: Separate specific wavelength fluorescent signals to achieve multi parameter cell analysis.

Ophthalmic equipment: In laser therapy, it protects the patient's retina from harmful wavelengths of light damage.

Astronomy and Security

Astronomical filter: Filter out specific wavelengths in urban light pollution (such as 589nm of sodium lamps) to enhance deep space observation effectiveness.

Laser countermeasure eyepiece: In military or security fields, it protects against direct or scattered light from laser indicators or lasers.