Purple optical colored glass is a type of optical filter material that exhibits high transmittance in the violet-blue region of the visible spectrum while demonstrating strong absorption/cutoff characteristics in the longer visible wavelengths and near-infrared bands. It is a short-wave-pass filter glass used in optical systems to extract the ultraviolet-to-violet-blue band while suppressing longer-wavelength stray light.
High transmittance in the UV-violet-blue region
Deep cutoff in longer wavelengths
Transmittance is highly dependent on thickness
| Color Category | Typical Spectral Characteristics | Peak Transmission Band | Cut-off / Attenuation Band | Typical Applications |
| Blue | Blue-green bandpass, red/NIR cutoff | 400–520 nm | ≥ 550 nm (cut-off) | Underwater photography filters, fluorescence excitation, color temperature correction, laser safety windows |
| Gold | Yellow-orange bandpass, blue/UV cutoff | 530–620 nm | ≤ 480 nm (cut-off) | Sodium line filtering, night vision protection, low-light imaging, fluorescence observation |
| Green | Green bandpass, dual cutoff (red & blue) | 500–560 nm | ≤ 480 nm & ≥ 610 nm | Traffic signal filters, machine vision contrast enhancement, reticle aiming |
| Purple | Violet-blue bandpass, mid-IR & visible cutoff | 350–450 nm | ≥ 480 nm (cut-off) | UV fluorescence excitation, black light filters, currency authentication, biochemical analysis |
| Red | Red bandpass, green/blue cutoff | 620–750 nm | ≤ 590 nm (cut-off) | Laser sight filters, traffic signals, IR temperature measurement windows, darkroom lighting |
| Neutral | Uniform attenuation across full visible spectrum, no wavelength selectivity | 400–700 nm (uniform transmission) | No cut-off peak; constant transmission | Light intensity adjustment/attenuation, laser power attenuation, exposure control, optical balancing |
