Alternative Light Sources
The use of spectral ranges other than the visible to probe materials can provide a great deal of insight into a problem. Looking for visible fluorescence in samples by long and short wave ultraviolet (UV) light macroscopically, or by a variety of ultraviolet wavelengths microscopically can permit visualization of contaminants, indicators of forgeries, even specific compounds. In addition to fluorescence, Microtrace has the capability to microscopically image samples in the ultraviolet range with a camera sensitive to ultraviolet photons or materials that absorb in the near- to mid-infrared (NIR, IR).
The visual spectral comparator (VSC), shown above, utilizes a variety of light sources (UV, Visible and NIR), illumination positions (coaxial, oblique, transmitted), and filters (excitation and barrier) to macroscopically probe the absorption and reflectance characteristics of various substances. While this is typically most applicable to writing and documents, we have found VSC useful in the examination and documentation in a variety of situations.