Advanced Imaging

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Advanced Imaging Magazine

Updated: January 12th, 2011 10:01 AM CDT

Taking the Guesswork Out of Choosing an IR Camera

Dual-band IR camera provides more information and better definition
Dual-band IR images of a highway at night
© IRCAM
Dual-band IR images of a highway at night. Upper left: MWIR, Upper right: LWIR, Bottom: overlay of MWIR and LWIR. The overlay image clearly reveals that the wind shields and the headlights exhibit higher intensity in the MWIR than in the LWIR.
The IRCAM Geminis® 110k ML
© IRCAM
The IRCAM Geminis® 110k ML delivers synchronous, pixel- registered images in two atmospheric windows (MWIR und LWIR).
Image of a starting airplane
© IRCAM
Image of a starting airplane. Left: MWIR image, middle: LWIR image, right: synchronous, pixel-registered overlay of MWIR and LWIR image. The dual-band IR camera identifies airplane exhaust gases by a greater MWIR intensity (blue) in the overlay.
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By Dr. Mónica López Sáenz, IRCAM GmbH

The infrared (IR) spectrum is nearly 1,000 times as large as the visible spectrum and is divided into near-infrared (NIR), short-wavelength infrared (SWIR), mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR). Only some parts of the atmosphere are transparent, the most important "atmospheric transmission windows" are in MWIR (3 µm to 5 µm) and in LWIR (8 µm to 12 µm).

The best infrared cameras work in these regions. Due to the high weather dependence of the atmospheric transmission and the spectral characteristics of the measured objects, users have to decide in which spectral region (which IR camera) they work. Because the decision always means a compromise, users asked for IR cameras working simultaneously in both spectral bands for many years.

The IRCAM Geminis® 110k ML is the first commercially available dual-band infrared camera with real-time overlay function. It records MWIR and LWIR images synchronously and pixel-registered. Its FPA detector is based on quantum well infrared photodetector (QWIP) technology and has 110,592 (384x288) pixels. The detector provides two synchronous and pixel-registered images: one in MWIR (peak wavelength: 4.8 µm) and one in LWIR (peak wavelength 8 µm). The image data are arranged electronically and formatted into two separate images. The fast read-out electronics delivers very fast data rates of more than 130 megabytes/s, which permits high-speed IR imaging. Depending on the integration time chosen, the frame rates range from 50 to 310 Hz.

The system uses special software to extract and visualize the often quite small differences between MWIR and LWIR images. The software corrects and processes the images and permits overlaying them with complementary colors making differences apparent and easily perceived. This permits the user to work with separate pictures of each wavelength as well as with a real-time overlay, which offers a far better-quality image.

As a special feature, the system has advanced software for real-time image processing of dynamic scenes. It has an image stabilization feature which compensates for the movement of the camera sensor relative to the scene observed. It also has a powerful image registration capability for automatic stitching of live images to create large mosaic images.

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