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4000nm (4.0μm) IR Shortpass Filter
4000nm (4.0μm) IR Shortpass Filter is designed to transmit wavelength shorter than 4000nm and block longer infrared light. Coligh specialized in manufacturing shortpass filter.
It has features below:
- Cut off wavelength 4000nm (4.0μm)
- High short wavelength transmission and deep long wavelength blocking depth
- IAD dielectric hard coating
- Silicon substrate
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IR Shortpass Filter 4.0 Micron Cutoff Wavelength Description
The 4000nm (4.0μm) IR Shortpass Filter is a key infrared optical component used in infrared systems. It exhibits excellent transmission for infrared light below 4000nm, with an average transmission of ≥92%, ensuring minimal light loss in the target shortwave infrared range of 3.0μm to 4.0μm. Additionally, it offers deep blocking in the 4200–5000nm range with Tave <1%, significantly reducing background noise.
- We use high-quality infrared optical-grade silicon as the substrate. Silicon features low thermal expansion, high hardness, and strong thermal shock resistance, making it suitable for applications with rapid temperature changes.
- The filter is coated using ion-assisted hard coating technology, ensuring a durable, dense, and strongly adherent coating. The hard coating provides excellent resistance to abrasion, wiping, and solvent cleaning, making it ideal for use in industrial or laboratory environments requiring regular maintenance.
4000nm (4.0μm) IR Shortpass Filter Technical Datasheet
| Parameter | Specification |
| Cut‑off Wavelength (50% T) | 40000nm+/-100nm |
| High‑Transmission Band | ≥ 92% @ 3000-4000nm |
| Blocking Region | 4200-5000nm |
| Optical Density (OD) | OD >2 (T < 1%) |
| Substrate Materials | Silicon |
| 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 | Ø25 mm, Ø20mm, or custom |
| Thickness | 0.5mm or 1.0mm or custom |
4000nm (4.0μm) IR Shortpass Filter Applications
- Mid-Wave Infrared Thermal Imaging Systems
Thermal imaging systems focus on the 3–5μm atmospheric window, but ambient thermal noise can severely affect image contrast. The 4000nm (4.0μm) IR Shortpass Filter transmits target radiation below 4μm while blocking background thermal noise in the 4–5μm range. This enhances image signal-to-noise ratio, highlights subtle temperature differences in high-temperature targets, and enables clear imaging even in smoky or dusty environments. - Gas Detection and Analysis
Gas absorption spectra are highly specific, such as CH₄ at 3.3μm and CO₂ at 4.26μm, but long-wave infrared background radiation must be isolated. The 4000nm (4.0μm) IR Shortpass Filter transmits only sub-4μm narrowband light while blocking stray light in the 4–5μm range, improving detection accuracy. The silicon substrate is corrosion-resistant, making it suitable for use in high-pollution environments such as industrial exhaust monitoring. - Medical Diagnostics
The emissivity differences of human tissue in the 3–4μm range can indicate pathological changes. The 4000nm (4.0μm) IR Shortpass Filter can be integrated into medical thermal imaging lenses to transmit physiological thermal radiation in the 3.5–4μm band while blocking surface radiation above 4.5μm. This helps to emphasize temperature differences in deeper tissues.
