10000nm Bandpass Filter

Situated in the mid-infrared spectral region (10μm), this wavelength exhibits strong thermal radiation characteristics, is readily absorbed by substances containing polar groups (e.g., H₂O, CO₂), and benefits from reduced water vapor interference during atmospheric transmission (falling within a partial atmospheric window).

  • Application 1: In infrared thermal imaging systems, the filter blocks stray light and isolates 10000nm band thermal radiation to enable precise non-contact temperature monitoring of high-temperature objects, such as industrial furnaces and power equipment.
  • Application 2: Used in gas spectral analysis instruments, it selects the 10000nm characteristic absorption wavelength to accurately measure concentrations of greenhouse gases like CO₂ and CH₄ in ambient air or industrial exhaust, supporting environmental monitoring and carbon emission management.
  • Application 3: In remote sensing and night vision devices, the 10000nm bandpass filter enhances target recognition in fog/smoke conditions by effectively detecting heat signatures from sources obscured by vegetation or camouflage materials, such as human bodies and vehicle engines.

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10000nm (10μm) Filter Application Selection Guide

I. Filter Configuration for Industrial Thermal Imaging Systems

In industrial equipment fault prediction and energy efficiency monitoring, long-wave infrared (LWIR) thermal imaging systems require precise capture of thermal radiation signals in the 8–14μm band. Key filter requirements for this application include:

  1. Spectral Characteristics
  • Bandpass Range: Strictly limited to 8–14μm to cover the peak region of blackbody radiation. For example, a filter using a silicon (Si) substrate with multilayer Ge/SiO₂ dielectric coatings can achieve high transmittance (T>70%) in 9–13μm, with out-of-band rejection (T<1%) across UV–20μm.
  • Anti-Interference Design: Integrates notch filters to suppress visible (400–700nm) and near-infrared (700–2500nm) interference, preventing detector saturation. Metal coating layers on germanium (Ge) substrates achieve OD3-level out-of-band suppression.
  1. Material and Process
  • Substrate Selection: Germanium single crystal (Ge) is preferred for its high transmittance (>90% in 8–14μm) and excellent mechanical/thermal conductivity, suitable for high-temperature environments. Cost-sensitive applications may use silicon (Si), requiring anti-reflective coatings to compensate for absorption losses near 10μm.
  • Coating Technology: Ion Beam Sputtering (IBS) deposits multilayer dielectric films with packing density >0.95, reducing moisture-induced wavelength drift (<1nm/℃). Diamond-like carbon (DLC) hard coatings (hardness >10GPa) protect against oil/dust abrasion.
  1. Selection Rationale
  • Background Noise Elimination: 8–14μm bandpass design avoids water vapor absorption peaks (e.g., 6.3μm) outside atmospheric windows, reducing environmental interference.
  • SNR Enhancement: High Ge transmittance combined with narrow bandpass (FWHM≈4μm) increases detected thermal signal strength by over 30%.
  • Environmental Adaptability: DLC coatings and sealed structures ensure stability from -40℃ to 85℃, meeting outdoor industrial requirements.

II. Filter Configuration for Methane Leak Detection

In petrochemical pipeline monitoring and environmental safety, methane (CH₄) exhibits a strong absorption peak at 7.66μm. Key filter requirements for this application include:

  1. Spectral Characteristics
  • Center Wavelength Precision: Requires precise matching to the methane absorption peak (7.669μm±0.02μm). "Split-layer" coating design with electron beam evaporation achieves wavelength error <0.3%.
  • Narrow Bandpass Design: Full Width at Half Maximum (FWHM) controlled between 59–120nm. For example, a sapphire (Al₂O₃) substrate with Ge/SiO₂ coatings provides 7.66μm center wavelength and 120nm bandwidth, with out-of-band rejection (T<0.5%) across 400–12,000nm.
  1. Material and Process
  • Substrate Selection: Sapphire (Al₂O₃) is preferred for high-temperature environments due to low thermal expansion (7.5×10⁻⁶/℃) and mechanical strength. Zinc selenide (ZnSe) offers higher transmittance but requires moisture resistance considerations.
  • Coating Technology: Ion-Assisted Deposition (IAD) controls film stress within ±50MPa, minimizing temperature-induced wavelength drift (<0.05nm/℃).
  1. Selection Rationale
  • Selective Absorption: Narrow bandpass design excludes interference from CO₂ (4.26μm) and H₂O (6.3μm), enabling ppm-level methane detection sensitivity.
  • SNR Enhancement: Optimized λ/4 stack coatings achieve peak transmittance >85% and OD3-level stray light suppression, doubling detector SNR.
  • Dynamic Tunability: Graphene-based tunable filters in portable devices allow ±50nm spectral tuning via electrostatic gating, adapting to varying methane concentrations.

III. Key Parameter Comparison for Selection

  • Center Wavelength
  • Industrial Thermal Imaging: 8–14μm (broadband, covering blackbody radiation peak)
  • Methane Detection: 7.66μm (narrowband, matching methane molecular vibration absorption)
  • Substrate Material
  • Industrial Thermal Imaging: Germanium (Ge, high transmittance >90% in 8–14μm); Silicon (Si, cost-effective with anti-reflective compensation for 10μm absorption)
  • Methane Detection: Sapphire (Al₂O₃, high-temperature resistance with low thermal expansion); Zinc Selenide (ZnSe, high transmittance but requires moisture protection)
  • Coating Process
  • Industrial Thermal Imaging: Ion Beam Sputtering (IBS), packing density >0.95, wavelength drift <1nm/℃
  • Methane Detection: Electron Beam Evaporation + Ion-Assisted Deposition (EAD-IAD), stress control ±50MPa, wavelength drift <0.05nm/℃
  • Out-of-Band Rejection
  • Industrial Thermal Imaging: UV–20μm, T<1% (OD3-level suppression of visible/NIR interference)
  • Methane Detection: 400–12,000nm, T<0.5% (excluding CO₂/H₂O absorption peaks)
  • Temperature Stability
  • Industrial Thermal Imaging: Operating range -40℃ to 85℃, wavelength drift <1nm/℃ (suitable for outdoor high-temperature monitoring)
  • Methane Detection: Operating range -20℃ to 60℃, wavelength drift <0.05nm/℃ (meeting portable device environmental requirements)
  • Typical Applications
  • Industrial Thermal Imaging: High-temperature equipment monitoring, power system efficiency analysis, industrial furnace thermal mapping
  • Methane Detection: Petrochemical pipeline leak inspection, landfill gas monitoring, coal mine gas concentration warning

IV. Selection Decision

  1. Determine Target Wavelength Band
  • Broadband (8–14μm) for general thermal radiation capture; Narrowband (e.g., 7.66μm) for specific gas absorption matching.
  1. Evaluate Environmental Conditions
  • High-temperature: Prioritize Ge substrates with DLC coatings; Moist environments: Avoid ZnSe, opt for sapphire or silicon substrates.
  1. Balance Performance and Cost
  • High-end applications (e.g., aerospace): Ge substrate + IBS coatings; Industrial applications: Si substrate + electron beam evaporation for cost reduction.
  1. Validate Anti-Interference Capability
  • Confirm out-of-band rejection (e.g., OD3-level) via spectral testing; Test background noise suppression in real-world scenarios.

These configurations enable filters to accurately extract target signals, solving background interference in thermal imaging and low-concentration identification in gas detection, ultimately enhancing system reliability and sensitivity.

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