Portable Spectral Video Comparator VSC-4C..

Portable spectral video comparator VSC-4C..

Vadim Antoninovich Shelkov

PORTABLE SPECTRAL VIDEO COMPARATOR VSC-4c FOR FORENSIC EXAMINATION OF DOCUMENTS

Determining the authenticity and integrity of various documents has always made up a significant share of the total volume of forensic investigations. Such work is usually carried out on special installations — spectral video comparators. In Russia, such equipment is produced by the Moscow MNPO SPEKTR, the Novgorod Research Institute of Industrial Television RASTR and the St. Petersburg company EVS. In the West, DOCUBOX comparators from the Swiss company PROJECTINA are quite common. If, of course, we can say this about rather expensive equipment, manufactured practically «to order». But the true «trendsetter» in the development and production of such equipment, without a doubt, is the English company Foster + Freeman. For more than twenty years, this company has been creating various devices for forensic investigations and, above all, spectral video comparators.Not long ago, the company released an extra-class device with the pretentious name VSC-2000. It replaced the VSC-1 spectral video comparator, which had been produced for many years. The appearance of the new device was not unexpected. The fact is that the technology of obtaining and processing video images has reached such perfection in recent years that the famous VSC-1 began to be perceived as another example of English conservatism, like Rolls-Royce and Bentley, especially if you consider that its cost in full configuration exceeds 40 thousand pounds.

The laboratory «monster» has been replaced by a real desktop workstation. First of all, the coordinated design of the entire installation attracts attention: instead of a pile of disparate devices, connected together only by the color of the front panels and company emblems, a rather elegant monoblock design with a computer monitor and keyboard has appeared. The combination of modern digital technologies with new software has made it possible to implement the most advanced document examination methodology to date. I described this remarkable device in detail in the magazine «Peace and Security» No. 3, 1998, pp. 36-40.

But life does not stand still. In one of the latest issues of the Foster+Freeman newsletter, there was a report about the VSC-4c portable comparator. As the name suggests, the new device has replaced the good old horse, the VSC-4. And although their names differ by only one letter “c”, apparently denoting a compact design, the real differences are much more significant. The new VSC-4c workstations use advanced document examination technology. According to Bob Dartnell, General Manager of Foster+Freeman, the VSC-4c is an ideal portable system for examining suspicious documents, checking the authenticity of passports and visas.

Photo 1. VSC-4c Comparator

VSC-4c – color and IR video system for rapid identification of passports and visa marks, as well as general examination of suspicious documents.

• Detects erasures and changes, as well as differences in IR absorption, visible and IR luminescence, watermarks, and paper opacity;
• displays fluorescence of security marks in natural colors;
• detects painted over/filled in and erased image fragments;
• improves the visibility of embossed (depressed) seals for easier study and comparison;
• facilitates comparison of documents by placing them side by side on the screen at the same level or even superimposing one on top of the other.

Lighter and more compact than its predecessor, the VSC-4c is easy to transport. The ability to operate from both the mains and a 12 V battery allows it to be used even in field conditions.

The comparator is equipped with a high-resolution CCD video camera for work both in the visible region and in the infrared range up to 1000 nm. A powerful 18x “zoom” lens of the video camera allows the expert not only to scrupulously examine the smallest details of the image, but also even compare individual fragments located in different places of the document at a considerable distance. The total linear magnification on the monitor screen reaches 25. The high sensitivity of the video camera allows studying a weak image caused by the IR luminescence effect. This property is supplemented by the ability to amplify the image in the integration mode (accumulation). As a result, the possibilities for identifying erasures, corrections and other counterfeits are significantly expanded. The accumulation (integration) mode in combination with the adjustable amplification of the video camera allows for a significant increase in sensitivity when detecting weak luminescence. Automatic diaphragm, motorized carousel with light filters, activated by simply pressing the control buttons, make working with the device much easier.

• a high-power ultraviolet light source that allows you to confidently detect protective fluorescent marks, as well as the remains of erased inscriptions that are invisible under normal lighting;
• a powerful halogen lamp with six filters to initiate IR luminescence;
• a source of transmitted light in the visible and IR ranges for examining watermarks and filled/painted over inscriptions;
• a source of incident light in the visible and IR ranges to detect differences in reflection and absorption coefficients;
• a source of coaxial light to detect special security marks;
• a source of oblique light of a new design to detect indented inscriptions and identify relief seals.

The well-thought-out design ensures maximum efficiency when working with each light source. The power of a 100-watt halogen lamp is quite sufficient to excite IR luminescence. Additional optics allow you to focus the beam and further increase its intensity, and a system of light filters helps to significantly reduce parasitic background luminescence. This allows you to detect even such changes made to documents that under other conditions might remain undetected.

All light sources are equipped with intensity regulators and can be used together.

But the VSC-4c comparator's capabilities are especially fully realized when connected to a personal computer equipped with a video card and the proprietary QDOS NT software package:

• an extended accumulation mode range of up to 20 seconds, equivalent to a 500-fold increase in sensitivity;
• contrast and contour sharpness enhancement, image inversion (positive-negative), as well as the ability to virtually clean a dirty document background;
• the ability to measure geometric dimensions and angles in the image field, facilitating the establishment of document authenticity;
• the ability to save images as standard BMP files, 24-bit color or 8-bit monochrome images;
• the ability to copy images for subsequent use in other applications, as well as their archiving.

• comparison of two fragments located next to each other on the screen — the reference and the studied one, one or both of which can be extracted from the computer memory;
• superposition mode, when a reference image stored in memory is superimposed on the image being examined to identify any differences that may exist. For greater efficiency, this technique can be supplemented by the inversion mode, when one image is subtracted from the other.

• CCD matrix sensitive to visible and IR images, adjustable gain.

• up to 0.25 sec, to extend the range it is recommended to connect to a personal computer with the QDOS NT software package

• motorized 18x optical zoom” with a total magnification of 25 times on the built-in monitor with a diagonal of 23 cm.

• 10 red and infrared filters with cut-off wavelengths of 610, 630, 645, 665, 695, 715, 735, 780, 850, 1000 nm, as well as a broadband visible light filter, mounted on a motorized turret.

• built-in flat color TFT LCD with a diagonal of 23 cm.

• powerful visible light source with 100 W halogen lamp, dichroic reflector and built-in filters with bandwidths of 400-540, 440-580,480-620, 530-660, 580-700 and 630-740 nm;
• incident white and infrared light source: 4 12.8 W incandescent lamps;
• transmitted white and infrared light source: 4 12.8 W incandescent lamps;
• oblique light source: one 12.8 W incandescent lamp;
• coaxial light source: one 12.8 W incandescent lamp;
• source of incident ultraviolet light: 4 fluorescent lamps of 8 W with a maximum radiation wavelength of 365 nm

• a charger for the battery;
• a shockproof case for carrying as hand luggage.

When ordering equipment, please specify the television standard used in the country: PAL or NTSC.

Well, we can only envy the lucky ones who will be lucky enough to work with this wonderful device. Let us just add that from the same Foster+Freeman News 1999/2000 newsletter it follows that recently the company has received a good package of orders for spectral video comparators, including the latest models, literally from all over the world. Here are some examples: Japan ordered 20 (!) VSC-2000 systems, the Bulgarian Immigration Service — 2 VSC-2000 complexes and 25 “old” VSC-4s comparators. China has already purchased several VSC-2000, VSC-1s and VSC-4s units. As it became known, Mr. Leslie Hock, the company's development manager, spent two weeks there demonstrating the latest developments of Foster+Freeman, including the Foram 685 Raman spectrometer, which we wrote about in No. 4-5 of the «Special Equipment» magazine for 1998.

And, finally, several top models of the VSC-2000 comparator were delivered to Switzerland, including to the police laboratories of Zurich and Lausanne. And this is already funny. I wonder what the specialists of the local comparator manufacturer, PROJECTINA, said about this?