foster + freeman

Viewed with the VSC concealed information is made visible by differences in the infrared absorbtion or fluorescence of inks. If the masking ink is transparent to IR and the underlying ink is opaque, the underlying information will be revealed using either incident or transmitted infra red light and a suitable infrared high pass filter.

If the masking ink is slightly transparent to visible light  the masked information may be revealed by illuminating the document with intense visible light, some of which will penetrate the masking ink to make the underlying ink fluoresce.

If the masking ink is fluorescent and the underlying ink absorbs the fluorescence the underlying information may be similarly revealed.

Above Image: Infrared fluorescence emitted by the concealed ink is sufficient to penetrate the masking ink when illuminated by intense visible light. The weak emission is integrated until visible

This is normally a straightforward process of examining a document with transmitted light but examinations may be made easier with a variety of additional techniques.

For example, it is possible to eliminate printing or handwriting on the surface of the document that is masking the watermark by examining the document in the infra red rather than the visible. Alternative display modes, in which original and counterfeit images are superimposed or displayed side by side, also make comparisons easier.

Special features which are invisible to the eye but which fluoresce brightly under ultraviolet light are often printed on or incorporated into security documents to deter counterfeiting.

The VSC 400 features the following UV sources:

• long wave incident UV, 365nm
• medium wave incident UV, 312nm
• short wave incident UV, 254nm
• long wave transmitted UV, 365nm

Printed bank note viewed under visible illumination (1.) and intense infrared lighting (2.) to reveal anti-Stokes fluorescence.

Retro-reflective features are elaborate graphic designs that are incorporated into security documents to prevent counterfeiting. They are printed with special coatings that render them invisible under normal light and can only be seen with illumination that is precisely coaxial to the angle of view.

The VSC 400 incorporates an intense 800-1000nm IR lamp for the examination of documents and identity cards printed with anti-Stokes security inks. These inks are exposed in the visible region of the spectrum when illuminated with infrared light.

An OVD on a 500 euro banknote viewed with angled illumination and a series of different OVD images on a 5 euro banknote viewed using sequential, multi-angled illumination.

OVDs on security documents commonly exhibit different images when illuminated at different angles. The VSC 400 is fitted with 13 white LEDs in horizontal and vertical arrays to provide sequential illumination at varying angles of incidence. The multiple images comprising the OVD may be stored and displayed without tilting the document.

Inks on a document that are identical in colour but have different chemical compositions may provide evidence of an alteration when examined in the near infrared region of the spectrum. Although undetectable with the naked eye, a IR image is easily viewed  using the VSC 400. Two techniques may be used.

The first is to look for differences in the IR light reflected or transmitted by the two inks. The document is illuminated with either incident or transmitted broadband IR and examined through a range of long wave pass filters with increasing thresholds between 650nm and 1000nm. Any difference in the spectrum of the transmitted or reflected light will become evident under at least one of the filters.

The second is to look for differences in the  fluorescence emitted by inks and, again, this is normally observed in the red to near infrared region of the spectrum. This fluorescence may be generated by illumination with intense visible light that has been filtered to be free of near infrared. As before, an examination of the document is conducted through a range of long wave pass filters.  Any difference in the spectrum of the fluorescence will become evident under at least one of the filters.

The VSC 400 provides the document examiner with the sensitive IR imaging system and the light sources and filters to perform both types of examination. Image integration is also provided to enhance the fluorescent images which are often of very low intensity.

The VSC 400 features orthoganol oblique lighting, illumination from two light sources at different angles, that provide the examiner with a clearer image of indented writing or embossed stamps.

However, not all such examinations are straightforward, as the presence of printing or handwriting on the document may interfere with the image and mask the surface detail. If the ink causing interference is transparent to near infrared light, it can be eliminated by selecting one of the integral camera filters, so that the ink becomes invisible while the infrared shadow remains.

Although the shadow casting technique is useful for examining deep indentations and embossing, shallow indentations or those not visible at all, are more effectively examined using an electrostatic imaging technique.

See details of the company's product ESDA².

One of the simplest ways to detect a counterfeit document is by visual comparison with a genuine one. With the VSC 400's wide display screen, high resolution and zoom magnification up to x55, discrepancies in fine detail are easy to detect when documents are displayed side by side. Both images can be annotated with text or symbols and each have notepads attached for added script.

To check previous work or library images up to 28 thumbnail images can be displayed on a single screen .

Graphic designs and logos on original documents and product labels are often inaccurately reproduced on counterfeits. These inaccuracies are easier to detect by examining original and counterfeit either side-by-side or by superimposition at high magnification.

A range of comparative display modes are available on the VSC 400 as standard. 

Measuring specific features of a document often provides valuable evidence of a counterfeit. The VSC 400 enables the radius, length, angle and area of a feature to be measured using an on screen cursor. Calibration provides absolute measurements and high magnification allows the smallest features to be examined.

'Quick Check'  enables an operator to make a sequence of document examinations under a variety of fixed, pre-programmed instrument settings. The facility is designed to standardise the repetitive examination of large numbers of similar documents such as passports, ID cards or cheques, suspected of being altered or counterfeited.

Once programmed under Quick Check, the VSC 400 automatically adopts the mode of illumination, lamp filter, imaging filter and lens magnification appropriate to the examination task selected, minimising operator performance errors.

Each stage of a multi-task examination sequence can be initiated either manually or automatically. Under automatic operation, each instrument setting is maintained for a predetermined period of time to allow the operator to carry out the examination before moving on to the next stage. Reports may be filed for future appraisal by a supervisor or expert examiner.

The technique can save time, ensure consistency in procedure and is particularly suitable for use by technician operatives.

The VSC 400 features an optical character reader that allows the operator to examine the ICAO coded data in the machine readable zone of passports and ID cards.

After selecting  any  country from the menu, the OCR deciphers, checks and displays the information held in the machine readable zone of the document.

Personal information invisibly embedded in photographs has become a valuable technique for protecting passports and ID cards against forgery. To visualise the information the operator simply selects a country to automatically apply the appropriate decoder. The system covers most systems currently in use and new ones can be added by the operator as they arise.

The VSC 400 enables the operator to create comprehensive casework files, in which images and notes may be stored. Images have associated instrument settings, i.e. type of illumination used, camera filter, integration time and magnification, which enable the operator to recreate identical conditions when making subsequent examinations.

Images may be annotated with text and symbols and each is provided with an on-screen working notepad.  All stored images and associated notepads may be interfaced with Microsoft Word for report writing.

Image search facilities allow the operator to retrieve stored images by name, file type (i.e. Tiff, BITMAP, JPEG, etc), keyword,or date of entry.  A thumbnail gallery of up to 28 recently stored images allows quick browsing of results stored in a casework folder.