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2400nm (2.4μm) IR Longpass Filter
2400nm IR longpass filter is an optical filter blocks wavelengths below 2400 nm and transmits longer wavelength. Coligh manufactures longpass filter up tp 30μm
- 50% Transmission Wavelength at 2400 nm
- >90% High Transmission
- Broadband Blocking and Transmission
- Insensitive to Angle of Incidence
- Hard First-Surface Dielectric Coating
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2400nm Infrared Longpass Optical Filter Description
2400 nm infrared longpass filter is designed for applications that require high-purity signals in the>2.4μm mid-infrared band
- Coligh’s 2400nm (2.4μm) IR Longpass Filter is strictly designed with a 50% transmittance cut on wavelength of 2400nm.
- The transmittance is greater than or equal to 90% in the target band of 2500nm-4000nm, achieving high transmittance. Maximize signal output and improve detection sensitivity.
- At the same time, it effectively blocks short-wave 400-2200nm stray light, with a cut-off depth of T<1%, that is, OD>=2.
- We use ion-assisted hard coating, the first surface dielectric film, the film layer is scratch-resistant and corrosion-resistant, and the service life is extended.
- It can be matched with anti-reflection film or spectroscopic film to further optimize system efficiency
2400nm Infrared Longpass Optical Filter Technical Datasheet
| Parameter | Specification |
| Cut‑on Wavelength (50% T) | 2400nm |
| High‑Transmission Band | ≥ 90% @ 2500nm-4000nm |
| Blocking Region | 400-2200nm |
| Optical Density (OD) | OD ≥ 2 (T < 1%) |
| Substrate Materials | White glass, Sapphire, Silicon, Fused Silica, Zinc Selenide |
| Coating Type | Hard first‑surface all‑dielectric |
| Surface Quality | 80-50, 60‑40, 40-20 scratch‑dig (MIL‑PRF‑13830B) |
| Clear Aperture | ≥ 90% of full aperture |
| Available Diameters | Ø12.7 mm, Ø25.4 mm, Ø50mm, Ø100 mm or custom |
| Thickness | 0.5mm, 1.0mm or custom |
2400nm Infrared Longpass Optical Filter Applications
- Gas detection
Gas molecules such as alkane 3.3μm, CO₂4.3μm, etc., their characteristic absorption peaks are located in the mid-infrared band of 2.5-5μm, but they are easily interfered by short-wave stray light during detection, resulting in signal distortion. The 2400nm longpass filter has a cutoff wavelength of 2400nm, transmits mid-infrared light above 2.4μm, and only allows gas absorption characteristic bands to pass through, shielding short-wave noise. It can avoid environmental stray light interference and improve the reliability of industrial safety monitoring. - Infrared thermal imaging
Thermal imaging relies on the object’s own thermal radiation of 3~14μm, but the short-wave infrared in the environment will interfere with the imaging contrast. The 2400nm infrared longpass filter cuts off stray light below 2400nm and only transmits thermal radiation signals. This can enhance the temperature distribution details and is suitable for overheating warning of power equipment and building energy consumption analysis. - Atmospheric pollution monitoring
The infrared characteristic spectra of atmospheric pollutants NOₓ and SO₂ are distributed in 2.5~15μm, but remote sensing equipment is easily affected by solar radiation background noise. This filter can filter out short-wave solar radiation below 2400nm and highlight the characteristic absorption signal of pollutants. - Security and Military
The thermal radiation signals of military targets are concentrated in 3~5μm and 8~14μm, and targets need to be quickly identified in complex environments. This filter can filter out short-wave interference in battlefield environments and enhance the contrast of target thermal signals.
