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Infrared-reflected (IRR) images record the reflected radiation in the
infrared region (700-1100 nm) from a subject when this is illuminated
with infrared radiation.
This image can be valuable in revealing under drawings and
concealed features. This is because infrared radiation is usually
highly penetrative and many materials, such as organic binders and
colorants, are generally transparent to infrared wavelengths.
Ultraviolet-reflected (UVR) images record the reflected radiation in
the ultraviolet region (200-400 nm) from a subject when this is
illuminated with ultraviolet radiation.
This image can be useful in characterising the superficial distribution
of material, such as varnishes and coatings, as ultraviolet
wavelengths are generally readily absorbed at the surface.
False-colour reflected images combine the infrared or ultraviolet¬
reflected image with components from the visible-reflected image of
the subject, to form a tri-chromatic false-colour image." The
combination can result in distinctive “false” colours that may aid the
characterisation or differentiation of materials.
Ultraviolet-reflected false-colour (UVRFC) images are produced
by splitting the visible image into its red, green and blue (RGB)
components and shifting the blue and green components into the
green and red channels respectively. The UVR image is inserted into
the blue channel. The reflective properties of the object in the UV
range are described by blue colour on the B channel.
Infrared-reflected false-colour (IRRFC) images are produced by
Splitting the visible image into its red, green and blue (RGB)
components and shifting the red and green components into the
green and blue channels respectively. The IRR image is inserted into
the red channel. The reflective properties of the object in the IR
range are described by red colour on the R channel. Note that Real
infrared false-colour (RIRRFC) images can also be produced by
recording three infrared images in the ranges: IRR1 (700-800 nm),
IRR2 (800-900 nm) and IRR3 (900-1000 nm) and by placing those in
the B, G and R channels of an RGB image, respectively. However,
the generation of such images is not considered further in this work.
Version No. 1.0
Date : 14/10/2013