Advanced multi energy method HI-MAT

Introduction

By means of coding the material information, the HI-MATPlus feature allows a quasi real color representation unlike the pseudo color representation which simply changes gray values into colors.
HI-MATPlus offers the advantage of an improved detection of items inside a piece of luggage due to its ergonomic color representation as compared to other systems or to the black and white representation.

B/W image

HI-MATPlus image

 

Classification

In the multi-energy method for evaluation of material information of the X-ray signal, the high and low energy radiation fractions obtained after penetration of the object, are compared. By means of this method conclusions concerning material origins can be made.
The classification of materials is carried out according to the atomic numbers Z. Three main groups of elements are distinguished by colors of a continuous color scale:

0 < Z < 10 orange (low)
10 < Z < 18 green (medium)
18 < Z < 40 blue (high)

Color assignment

The scale comprises colors of orange for elements of low atomic number, i.e. elements which can be found in organic material, green for elements of medium atomic number and blue for elements of higher atomic number. The information concerning material thickness respectively absorption factor is furnished by means of the degree of brightness for the color signal. Therefore, items composed of the same material but which are different in thickness, show the same color while differing in brightness.

Ergonomic image display

Due to sophisticated real-time image processing and edge enhancement of the new HiTraX X-ray technology, the image focus of the HI-MAT Plus function is superior. Very fine structures and differences in density become visible so that thin wires or hidden items in manipulated luggage, can easily be recognized.

The sensitivity of the human eye varies with the wavelength (color) of light. The color representation has therefore been adapted to the human eye anatomy.

Given the HI-MAT Plus method, the coloring of the different materials in the image is chosen so that the brightness of color perceived by the human eye matches the luminance of the corresponding b/w image. The adaptation of the image representation to the physiognomy of the eye facilitates the focusing and object perceptibility.

Overlapping material

The advantage of a continuous color scale becomes evident when considering overlapping materials: In systems with abrupt color switch-over between organic and non-organic materials, even thin layers of overlapping materials, such as steel, copper or PVC, will lead to organic materials being classified as non-organic materials, which is wrong.


HI-MAT Plus, however, provides a mixed color representation depending on the degree of the mixture of materials which can be distinguished from the color of the overlapping materials.

Enhancements

The contrast enhancement functions known from the b/w image representation are also available for the HI-MAT Plus color representation feature.
These functions only have an effect on the image brightness, the colors and thus the material assignment are always kept.

VARI-MAT

VARI-MAT is the transfer of a scale of gray values, as known from the b/w image, into the HI-MAT color image. Via a window, which is variable in position and size. By means of VARI-MAT the information furnished by the detectors can be fully utilized up to the physical limits.

VARI-MAT is suitable for visualizing finest differences in contrast as well as details of items which are difficult to penetrate and suppresses any disturbing homogeneous background.

Typical suitcases, which are densely packed, will be represented with an all organic background which is represented in orange in the HI-MAT Plus image. The VARI-MAT image will then be positioned in a way that this background appears almost invisible. Suspect accumulations of organic material will clearly contrast with such background. On depression of a key, an arbitrary VARI-MAT presetting will be available in real time.