Understanding Infrared Spectrum Wavelengths: NIR, MIR, and FIR
The infrared spectrum is an essential part of the electromagnetic spectrum, located between visible light (VIS) and microwaves. Infrared (IR) wavelengths are broadly categorized into near-infrared (NIR), mid-infrared (MIR), and far-infrared (FIR) regions, each with unique characteristics and applications. Understanding these divisions – along with terms like MWIR (mid-wave IR) and LWIR (long-wave IR) – is vital for industries relying on spectroscopy, thermal imaging, and optical sensing.
In this guide, we’ll break down infrared wavelengths, compare regions, and explore their applications, with a focus on near- vs. mid-infrared spectroscopy.
Infrared Spectrum Wavelength Divisions
Infrared light spans wavelengths between 0.7 µm to 100 µm, divided into the following regions:
Additionally, within MIR, two sub-categories are often referenced:
- MWIR (Mid-Wave Infrared): 3 – 8 µm (thermal imaging, gas sensing)
- LWIR (Long-Wave Infrared): 8 – 12 µm (thermal and environmental monitoring)
Relationship to Visible Light (VIS)
The visible spectrum (VIS), which ranges from 400 – 700 nm (0.4 – 0.7 µm), marks the transition into NIR. Beyond this, the infrared spectrum begins, with NIR wavelengths closest to visible light and FIR approaching microwave regions.
Near-Infrared (NIR) vs. Mid-Infrared (MIR) Spectroscopy
1. Near-Infrared (NIR) Spectroscopy
Wavelength Range: 0.7 – 2.5 µm
NIR spectroscopy analyzes overtones and combinations of molecular vibrations, primarily focusing on bonds like C-H, O-H, and N-H. While less sensitive than MIR spectroscopy, NIR offers:
- Fast measurements
- Penetration depth – Ideal for bulk material analysis
- Non-destructive testing
Applications:
- Food and agriculture: moisture, protein, and sugar content analysis
- Pharmaceuticals: quality control for powders and tablets
- Textiles: fiber composition identification
2. Mid-Infrared (MIR) Spectroscopy
Wavelength Range: 2.5 – 12 µm
MIR spectroscopy targets fundamental vibrations of molecular bonds, providing highly specific “fingerprints” for chemical compounds. Its ability to directly probe bond vibrations makes MIR ideal for detailed molecular analysis.
Benefits:
High sensitivity and specificity: detects molecular structures with precision
Ideal for gas and liquid analysis: measures absorption in distinct MIR bands
Applications:
Industrial quality control: Coating thickness, polymer characterization
Gas sensing: Monitoring emissions like CO2_22 and CH4_44
Environmental monitoring: Detecting pollutants and contaminants
Discover more about mid-infrared spectroscopy solutions here.
MIR Sub-Categories: MWIR and LWIR in Thermal Applications
MWIR (Mid-Wave Infrared): 3.0 – 8.0 µm
- Sensitive to high-temperature sources (e.g., combustion).
- Used in military, aerospace, and gas detection systems.
LWIR (Long-Wave Infrared): 8.0 – 12.0 µm
Detects cooler objects through thermal emissions.
- Common in thermal cameras, building diagnostics, and medical imaging.
Both MWIR and LWIR complement each other, enabling thermal imaging systems to capture a broad range of temperatures across applications.
Comparing Infrared Spectrometers: NIR vs. MIR
Near-Infrared Spectrometers
Speed: faster spectral acquisition
Cost: generally lower cost compared to MIR spectrometers
Data: provides broad compositional analysis but lacks molecular specificity
Mid-Infrared Spectrometers
Sensitivity: superior molecular identification through fundamental vibrations
Applications: excels in chemical, gas, and coating analysis
Speed: conventionally low speed, but innovations like NLIR’s spectrometers now offer high-speed MIR measurements at up to 130 kHz read-out rates
NLIR’s mid-infrared spectrometers leverage patented upconversion technology to deliver unmatched speed and sensitivity in the MIR range. Learn more about NLIR’s spectrometers.
Infrared spectrum wavelengths, spanning NIR, MIR, and FIR, offer unmatched possiblities for diverse insights across industries. From near-infrared spectroscopy for rapid material analysis to mid-infrared solutions for precise molecular identification, IR technology continues to drive advancements in quality control, gas sensing, and environmental monitoring.
Take the Next Step with NLIR
Innovations in high-speed, mid-infrared spectrometers – like those developed by NLIR – are revolutionizing how industries measure, monitor, and optimize their processes. Whether you need near-infrared bulk analysis or mid-infrared precision, understanding the unique capabilities of each region ensures you select the best technology for your application. To explore cutting-edge infrared solutions, contact NLIR today.
