Principles and Applications of SWIR Imaging

In a wide range of application areas, encompassing myriad different techniques and technologies, high-resolution imaging is the key to success.

A number of the most trusted and oldest imaging tools are based on optics, like photography and cinematography, which record light/electromagnetic radiation to reproduce visual representations of objects.

These can be subdivided further via their optical sensitivity. For example, SWIR imaging is sensitive to short-wave Infrared wavelengths between 900 – 1700 nanometers (nm).

All objects characteristically reflect or absorb light. Based on the spectral wavelengths of light that they reflect, the human eye perceives the color of objects relative to ambient conditions (i.e. luminance).

By utilizing image sensors sensitive to the visible portion of the electromagnetic spectrum (~380 – 750 nm), conventional cameras are able to emulate this process. Thus, the insights that process engineers, facility managers, and researchers can acquire from conventional visible light-based optics are limited.

As discussed, SWIR imaging is sensitive to a certain portion of the electromagnetic spectrum’s infrared region; between near-infrared (NIR) and mid-wave infrared (MWIR).

Based on IR radiation, it is unique to both visible imaging and other forms of photography, in that it is neither reliant on thermal emissivity nor influenced by poor ambient conditions. This article explores how this benefits a range of applications, from hyperspectral imaging to product inspection.

Hyperspectral Imaging

SWIR hyperspectral is a powerful tool for non-contact molecular analysis, imaging can establish the chemical composition of objects down the molecular scale. This gives a three-dimensional data set that can be separated to gain an understanding of how spectra differ in different spatial areas of the image.

Astronomy

SWIR imaging is employed in astronomy studies associated with the photometric passbands J, H, and K; with effective wavelength midpoints of 1220 – 2190 nm. They excel because of their high frame rates, non-sensitivity to atmospheric phenomena, and low noise levels.

Active Imaging and Enhanced Vision Assistance

Active SWIR imaging is ideal for surveillance and long-range reconnaissance because of the employment of invisible laser illumination and gated viewing. This is perfect for imaging through severe obscurants (fog, smoke, etc.) or night vision applications.

Subsequently, SWIR cameras are employed for active imaging and enhanced vision assistance in aerospace, automotive, security, and surveillance applications.

Industrial Sorting

SWIR imaging is becoming more commonplace in industrial quality assurance and control (QA/QC), giving insights into a number of material qualities that cannot be detected by conventional optics, like opaque container fill levels or bulk dryness.

Biological Imaging

SWIR imaging has proven a powerful tool for deep photon penetration of biological tissues, especially as a replacement to ionizing radiation sources (i.e. X-rays) which can cause harm.

Currently, it is utilized as an optical diagnostic tool for preclinical studies in large and small animals, with the potential to support/supplant high-energy medical imaging tools in certain clinical settings in the future.

Free Space Optical Communication

Free space optical (FSO) communications can transmit data wirelessly at high speeds via line of sight IR signals. SWIR cameras are proving instrumental in FSO communications because of their low noise and high frame rates irrespective of atmospheric or ambient conditions.

Product Inspection

SWIR cameras are ideal for on-line electronics inspection, especially for quality assurance and control (QA/QC) of semiconductors like silicon (Si) ingots, wafers, and boules.

Poly-crystalline Silicon (Si) Wafer Inspection.

Poly-crystalline Silicon (Si) Wafer Inspection.

Short-wave IR signals can highlight the small scale and extremely fine defects in intermediary semiconductor goods, like misalignment of surface etchings or microcracks, which could influence the performance of products downstream, from integrated circuits (ICs) intended for consumer electronics to solar cells.

This information has been sourced, reviewed and adapted from materials provided by Photonic Science.

For more information on this source, please visit Photonic Science.

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