What are the advantages of colored glass longpass filters?
1. Excellent environmental stability, weather resistance, corrosion resistance, aging resistance.
2. Extremely high laser damage thresholds.
3. Excellent optical homogeneity.
Refractive index deviation <5×10-⁶ (over full aperture range).
Wavefront aberration <λ/8@633nm (for high-precision imaging). 
No stress birefringence caused by coating.
4. Wide spectral adaptability: full UV to MIR coverage.
5. Significant cost advantages.
6. Zero angle sensitivity.
At angle of incidence of 0-60°: Cut-off wavelength shift <2nm (up to 50nm for coated filters) , transmittance fluctuation <1%.
7. Extensibility of special functions.