コレクション: バンドパスフィルタ

The transmittance of UV bandpass filters generally falls between 15-30%.This relatively low transmission is inherent to UV filter design and materials.

Limiting Factors

Several factors contribute to the lower transmission rates:

Material Limitations

• Most materials used in UV filters have inherent absorption in the UV range
• The absorption of UV light by materials makes it difficult to achieve high transmission while maintaining deep blocking over wide wavelength ranges

Design Challenges

• The refractive index difference of dielectric materials decreases at shorter wavelengths, requiring more layers to achieve desired spectral control.
• Complex designs with multiple layers are needed for effective UV filtering, which can increase optical scatter and reduce transmission.

Cost Factors

IR bandpass filters are indeed typically more expensive than visible and NIR counterparts due to:

• Limited material choices suitable for IR wavelengths
• More complex fabrication processes

Substrate Materials for IR range

Germanium (Ge)

• Excellent transmission properties in MWIR to FIR ranges
• Particularly effective for wavelengths from 1.7 µm and longer
• Features high refractive index and high Knoop hardness
• Ideal for thermal imaging and rugged IR imaging applications

Silicon (Si)

• Cost-effective solution for IR applications
• Transmission starts from approximately 1.2 µm
• Lightweight material with good performance
• Commonly used in spectroscopy, MWIR laser systems, and THz imaging

Sapphire (Al₂O₃)

• Known for exceptional durability and scratch resistance
• Provides broad transmission capabilities
• Particularly effective in NIR applications
• Used in IR laser systems, spectroscopy, and rugged environmental equipment