The Video Spectral Device (VSR) is an imaging device that
uses lights, cameras, and filters to help in the analysis of questioned
documents; it can do this by assisting the examiner in visualising concealed
security features, uncover alterations on a document, as well as analyse inks.
It is made up of two components, which includes a computer,
and also an imaging device that contain different radiant light sources, such
as halogen and fluorescent lamps, filter devices, and also two charge couple
devices (CCD), a black and white CCD video camera, and also a colour CCD video
camera. A CCD is a circuit that can save and display data for an image, this is
possible because of the devices ability to convert each pixel into an
electrical charge, and the intensity of this charge corresponds with a colour
in the spectrum, this is due to the devices sensitivity to light.
The VSR can aid an investigator in identifying different
inks used, and also writing that has been changed or taken away – this can be
done by using different light wavelengths to observe how the different inks
respond to the light. For instance, a light source paired with an infrared
filter can enhance ink that has faded over time, therefore making an old
document more legible in a court of law. In order to expose the indentations
under a signature, investigators could use an incident light and a long pass
filter; this can help detect differences in signatures, which can relate to an
act of forgery.
Multi light sources include ‘Infrared Radiant Energy’ which is
used in to help an investigator reveal objects, that cannot be seen by the
naked eye, by looking through inks. This feature along with other lighting
options can be used to visualise other elements, such as watermarks. ‘Coaxial
Light’, which is used for security features such as the retro reflective
feature that reacts with a coaxial light in order to reveal the security
pattern, this is because when the light hits the retro reflective feature on
the same axis as the light that produces the image.