SEM-EDX (Scanning Electron Microscopy with Energy-Dispersive X-Ray Analysis)
Definition
A technique combining high-resolution surface imaging with elemental composition analysis; used to compare metallic-flake elemental ratios in OVI ink and to measure surface topography of intaglio ink ridges.
- Full name
- Scanning electron microscopy with energy-dispersive X-ray analysis
- Application 1
- Comparing metallic-flake elemental ratios in OVI ink
- Application 2
- Measuring surface topography of intaglio ink ridges
- Data type
- Combined high-resolution image plus elemental spectrum
- Field
- Counterfeit currency and questioned document examination
Common questions
What is OVI ink and why does its elemental ratio matter?+
Optically variable ink contains metallic flakes, often aluminium or other alloys, that shift colour with viewing angle on genuine banknotes. Genuine and counterfeit inks differ in the precise elemental ratios of these flakes, so SEM-EDX comparison can flag a counterfeit that visually mimics the colour-shift effect.
How does SEM-EDX help distinguish genuine intaglio printing from a scanned or printed forgery?+
Genuine intaglio printing raises ink in a distinctive ridge profile from the pressure of engraved plates, which SEM imaging can measure directly. A photocopy or inkjet forgery lays ink flat or in a different ridge pattern, so the surface topography itself becomes discriminating evidence.
Is SEM-EDX destructive to the banknote or document being examined?+
It is generally non-destructive to minimally invasive; small samples or the note itself can often be examined directly, though non-conductive substrates may need a light conductive coating or use of variable-pressure SEM to avoid altering the evidence.
Related terms
- 365 Nm UV Lamp
- A long-wave ultraviolet lamp used to examine substrate fluorescence, security thread UV response, and UV-reactive features on banknotes; genuine cotton-linen substrate appears...
- 3D Surface Profilometry
- A non-contact optical measurement technique used to quantify the topographic height (Z-height) of intaglio ink ridges; genuine MGNS intaglio measures 15-40 micrometres;...
- Bleached-Genuine Counterfeit
- A counterfeit produced by chemically removing the printed design from a genuine lower-denomination note and reprinting it as a higher denomination; passes...
- Counterfeit Currency Database (CCD)
- The US Secret Service's classification registry of counterfeit production signatures, assigning class codes to each distinct printing-process and denomination combination detected in...
- CVPC (Currency Verification Processing Centre)
- An RBI-designated facility in India where banks submit suspect notes for initial authentication and classification before forensic referral.
- FTIR Spectroscopy (Fourier Transform Infrared)
- A non-destructive analytical technique that measures infrared absorption as a function of wavenumber, producing a spectrum diagnostic of the chemical functional groups...
- Iodine-Starch Test
- The chemical basis of the counterfeit-detector pen: iodine reacts with starch in wood-pulp paper to form a dark blue-black complex, while genuine...
- Raman Spectroscopy
- A non-destructive laser-based technique sensitive to molecular vibration modes in pigments; complements FTIR by characterising pigment molecular structure rather than bulk ink...
- Supernote
- A high-quality counterfeit capable of passing casual field examination; originally applied to US $100 counterfeits attributed to state-sponsored production with genuine cotton-linen...