Optical Filter Quick Reference Guide 707-573-6747 • www.depsci.com Bandpass Filter Transmission 100 Peak transmittance First peak 5 Antireflection 100 Bandpass 100Dichroic Beamsplitter Blocking transmission Blocking Region First peak Region transmission Broadband • Laser Line • Ball Lenses • Domes Narrow Bandpass • Wide Bandpass Cold Mirror • Edge Filter • Hot Mirror 80 4 80 Single & Dual Bandpass 80 Long/Shortwave Pass 80% of first peak transmission 80% of first peak transmission %) Passband 60 Key Specifications Cost Drivers Key Specifications Cost Drivers Key Specifications Cost Drivers 3 60 60 Half-power point 40 (50% of peak transmittance) • Wavelength range • Broad wavelength • Center wavelength • Tight CWL placement • High reflectance region • Short transition Transmittance ( Transmittance Full Width at Half Maximum (FWHM) or angle range and level between reflecting and = λ2 – λ1 2• Maximum average 40• Bandwidth • Steep slopes 40 20 5% absolute transmission 5% absolute transmission transmitting regions or absolute reflectance • Absolute vs. average • Edge slopes • Low in-band ripple • High transmittance 0 λ λ reflectance 20 region and level • Maintaining flatness 1 2 1• Angle of incidence 20 Wavelength (μm) • Blocking range/level • Peak vs. average OOB • Angle of incidence after coating 0 0• Angle of incidence 0 Filter Definitions 400 450 500 550 600 650 700 7.0 8.0 9.0 10.0 11.0 6.5 7.0 7.5 8.0 8.5 9.0 Bandpass: A filter that transmits a discrete band of wavelengths. Center Wavelength (CWL): For a narrow band- 100 Plate Beamsplitter 5 Dark Mirror 100 Notch pass or notch, 2 λ 1 λ 2 (where λ & λ are the HPPs). Non-polarizing • Polarizing External • Internal • Bidirectional Narrowband • Broadband • Multiband λ1 + λ 1 2 2 λ λ For a wide bandpass, 1 + 2 . 80 4 80 2 Cutoff: The wavelength at which a filter transitions Key Specifications Cost Drivers Key Specifications Cost Drivers Key Specifications Cost Drivers 60 from transmitting to blocking. 60• Wavelength range • Broad wavelength 3• Wavelength range • Broad wavelength • Blocking region • Tightly toleranced or Cuton: The wavelength at which a filter transitions range or angular range and level narrow blocking region 40• Angle of incidence 2• Reflectance 40 from blocking to transmitting. • R/T (non-polarizing) • Tightly toleranced • Transmittance • Absolute vs. average • Transmissive region • High OD Full Width at Half Maximum : The R & T reflectance and level (FWHM) 20• Extinction ratio 1• Angle of incidence 20 • Broad transmission separation between HPP in wavelength or per- • High extinction ratio • Angle of incidence region centage of CWL. (polarizing) 0 0 0 4 6 8 10 12 14 350 450 550 650 750 850 650 700 750 800 850 900 950 Half-Power Point (HPP): The wavelength at which transmission is half of the maximum value. Longwave Pass: A filter that transmits wavelengths longer than the cuton, and blocks those below. Patterned Coatings 100 High Reflector 100 Spectral Metal 20µm line width • ±5µm Feature placement Out-of-Band (OOB) or Blocking Region: Broadband • Laser Line • Dielectric • Metal Broadband • Wavelength Selective 8" diameter substrates The spectral region in which a filter strongly 80 80 Steel • Aluminum reflects or absorbs. Key Specifications Cost Drivers Key Specifications Cost Drivers Key Specifications Cost Drivers 60 Passband: The spectral region in which a filter is 60• Reflectance • Broad wavelength • Reflectance • High reflectance over • Spectral performance • Thick coatings highly transmitting. range a broad wavelength 40• Wavelength range 40• Wavelength range • Pattern geometry – • Small feature sizes Shortwave Pass: A filter that transmits wavelengths • Broad angular range range single or double sided shorter than the cutoff, and blocks those above. • Angle of incidence • Angle of incidence • Multiple complex • Broad angular range 20 • Absolute vs. average 20 coatings Slope: The rate of change of transmission at the reflectance cuton or cutoff, λ80% of first peak – λ5% absolute transmittance . λ5% absolute transmittance 0 0 3.0 3.5 4.0 4.5 5.0 5.5 350 450 550 650 ©2018 Lockheed Martin Corporation. All Rights Reserved. .