Delta DT
Optical system for detecting indented images Delta - DT
Is an optoelectronic device for detection, visualization and registration of both indented and partially destroyed impressions on various paper documents submitted for forensic examination.
DESCRIPTION
The analyzer of indentations is designed for detection, visualization and registration of both indented and partially destroyed impressions on various paper documents submitted for forensic examination.
During examination of indented impressions the following operations are performed: a shadowgraph is created using oblique light, then the shadowgraph is photographed at various light azimuth angles with set discreteness, and finally received images are combined with a shift along the light direction.
When damaged or partially destroyed impressions are analyzed, an object is lighted by a diffuse light source and photographed.
Delta-DT analyzer provides:
- Detection, visualization and registration of indented impressions on objects measuring up to 210x297 mm;
- Brightness reduction or elimination of fragments obstructive to detection of indented impressions and visible images;
- Detection, visualization and registration of damaged and partially destroyed images measuring up to 210x297 mm.
These are main advantages of Delta-DT analyzer of indentations:
- The analyzer does not require any additional consumables to operate;
- The analyzer does not require any preprocessing of the examined objects;
- The method of relief examination is non-contact and non-destructive for documents;
- The optical method is not inferior in its sensitivity to the electrostatics powder method.
There are two models of the analyzer available: the collimated light source analyzer and the point light source analyzer.
The system includes the following basic equipment: an optical-mechanical system, a diffuse illuminant, a vacuum pump, a PC, a photo printer, a desktop scanner, an operator’s worktable, an operator’s work chair.
Optical Scheme of The Analyzer of Indentations
1- digital camera, 2 – vacuum bed with an examined object on it, 3 – light, 4 – light rotation path about the bed.
Scheme of Image Registration Under Diffused (Shadowless) Light
1 – camera, 2 – light-protective cover, 3 – fluorescent lamps, 4 - light-diffusing screen, 5 – vacuum bed with an examined object on it.
TECHNICAL SPECIFICATIONS
| Vacuum Bed Size | 210 х 297 mm |
| Illumination For Photographed Objects |
Not less than 50 lx – for a point light source analyzer; Not less than 100 lx – for a collimated light source analyzer; 500 lx – for a diffuse light |
| Tilt Angle of Light |
0 – 10 degrees with 0.1 degree step |
| Rotation Angle of Light |
0 – 360 degrees with 1 – 180 degree step |
| Size | 1000 х 1000 х 1300 mm |
| An examined object is fixed by the vacuum hold-down | |
| The analyzer is equipped with a digital reflex camera using a matrix of at least 10.0 pixels | |
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The analyzer is operated by a PC with a system control and images processing software application, which operates under MS Windows (Windows XP and later versions) |
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SOFTWARE
The GELIOS software package operates the indentation analyzer and a camera; it also controls photographing procedure and received images processing. The package includes two programs:
1. The Gelios 1 Program enables photographing of an examined object under oblique light at various azimuth angles evenly distributed around the object. The program allows receiving various data sets automatically.
Data Reading Window
2. The Gelios 2 Program provides detection, visualization and registration of both indented and partially destroyed impressions.
Experiment Data Display Window
Images of one set are combined with each other with each image shifted to a specified number of pixels along the incident light beam direction; in other words, shadowgraphs obtained at different light angles are summed up. Besides the program allows subtracting one resultant image from another to increase contrast and to remove unwanted background.
Data Processing Window