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BIG PHYSICS, BIG QUESTIONS –

Technology : Camera goes on smog patrol

By Peter Hadfield

Tokyo

JAPAN’s national broadcasting company, NHK, has developed a camera that
can display infrared and ultraviolet light in real time and in colour. The
camera could be used for pollution monitoring, health checks and detecting art
forgeries.

Prior to NHK’s research, infrared and ultraviolet could only be seen on the
same screen if a computer merged and enhanced black-and-white images caught on
separate cameras.

Yoshihiko Ogaki, a member of the development team at NHK’s Science and
Technical Research Laboratories in Tokyo, says the camera has many advantages.
“It requires only one camera to process both ultraviolet and infrared radiation
instead of two. And because the pictures are already in colour they don’t need
computer enhancement—saving time and money.”

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The camera can take in light between 250 and 1050 nanometres in wavelength.
Light entering the camera is split into three bands. Red to infrared waves,
which comprise one band, pass through a charge-coupled device that
compresses the electromagnetic radiation into visible light of wavelengths
toward the red end of the visible spectrum.

The band of ultraviolet to blue waves go to a device dubbed the High-Gain
Avalanche Rushing Amorphous Photoconductor (HARP) by NHK researchers. This
lengthens the wavelengths of ultraviolet radiation, bringing it into the blue
end of the spectrum.

After being converted into visible light, the two ends of the spectrum are
then sent through a colour encoder along with the visible light to form a
coherent image. To make the infrared and ultraviolet light stand out, the
researchers are representing them with shades rarely seen in real world objects.