3.3μm Bandpass Filter

3.3μm bandpass filters are designed to transmit a selected mid-wave infrared (MWIR) wavelength band centered near 3.3μm while reducing unwanted out-of-band light and thermal background noise.

Applications:

  • NDIR (Non-Dispersive Infrared) gas sensing for hydrocarbons, methane (CH4), and volatile organic compounds (VOCs)
  • Environmental monitoring and industrial leak detection instruments
  • Detector-side 3.3μm signal isolation before thermopiles, pyroelectric detectors, or PbSe/HgCdTe sensors
  • Broadband IR source filtering for optical measurement and spectroscopy setups

Bandwidth options:

  • 136nm FWHM for tighter 3.3μm hydrocarbon absorption band isolation and maximum out-of-band thermal noise reduction
  • 196nm FWHM for balanced MWIR signal transmission and accommodating broader VOC absorption lines

Select the bandwidth based on the target gas absorption profile, IR source spectrum, detector sensitivity, blocking range, and required signal level.
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Filters

5 items

Filter

US8653461B1 - Thermography camera tuned to detect absorption of infrared radiation in a selected spectral bandwidth

US8653461B1 - Thermography camera tuned to detect absorption of infrared radiation in a selected spectral bandwidth

Context: A thermography camera system modified to detect the specific infrared absorption signatures of gases.

Usage of Filter: The filter is positioned in the optical path between the lens and the Focal Plane Array (FPA), often cooled to minimize self-emission.

Function: It acts as a spectral gate, transmitting only the radiation wavelengths that correspond to the C-H bond vibrational modes of alkane gases.

Result: It transforms a standard thermal imager into a gas-specific radiometer, enabling the operator to see gas leaks that would otherwise be indistinguishable from thermal noise.

US20250258089 (Publication) - Correlated interference polarization spectrometer

US20250258089 (Publication) - Correlated interference polarization spectrometer

Context: A Correlated Interference Polarization Spectrometer (CIPS) used for remote sensing and quantitative analysis of gas concentrations.

Usage of Filter: The filter is used as a broadband pre-filter placed before the interference polarization assembly.

Function: It isolates the broader 3.3 $\mu$m window to select the target spectral order, preventing out-of-band light from creating aliasing or noise in the fine interference pattern.

Result: It ensures high-fidelity spectral data, allowing the system to distinguish and quantify specific hydrocarbon molecules with high precision.

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