Related Field of the I nvention

The present invention generally relates to detection of concealed objects under the clothes of humans using passive MMW (millimeter wave) and THz (terahertz) imaging technique with variable focal length feature.

Background of the I nvention ( Prior Art)

I n the state of the art, there are imaging systems used in millimeter wave and terahertz bands can operate at different distances, and these systems cannot offer resolution improvement at different distances with the zoom function or, in other words, with variable focal length feature.

Exemplary inventions for such systems are disclosed in US patent 6746642 (B2) to Chinese patents CN101788665 (B) and CN102809745 (B) .

The invention of the Chinese Utility Model CN204156099(U) is a reflective antenna of an imaging system that can be used in millimeter wave and terahertz bands. On the said reflective antenna, there is provided a mechanism for performing the step-by-step variable focal length feature, in other words, the function of the zoom lens. However, this mechanism does not offer a reliable performance in imaging the concealed objects.

The systems using active MMW/THz at low power levels are harmful to human health and they do not offer a reliable performance at long distances. On the other hand, the systems using X-Ray are also harmful to human health, especially for children and pregnant women.

Brief Description of the I nvention

The aim of the present invention is to use passive millimeter wave/terahertz imaging with variable focal length configuration for detecting the concealed objects under the humans’ clothes. Existing products and studies do not use the variable focal length feature. These systems can operate at different distances but do not offer resolution improvement according to distance. I t is an innovation of the invention that the zoom lens function in optical cameras is adapted to the millimeter wave and terahertz bands. Thus, resolution improvements can be made at different distances when using the system. As a result, concealed objects under the clothes of humans who are approaching from long distances can be visualized. Due to this feature, it provides a significant advantage over other systems.

Since the system consists of known standard elements, it provides cost advantage. I n this invention, the conventional Cassegrain telescope optical assembly is adapted to millimeter wave and terahertz bands. When the distance increases, a fixed-focus system reduces resolution. The reduced resolution is increased by the variable focal length while providing mobility between the optical elements. With the increasing resolution, long distance imaging property is added using optical system with variable focal length at millimeter wave and terahertz bands.

The variable-focal length property subjected to this invention is to improve the resolution while taking images at different distances. I n this way, objects that are hidden under the human clothes at different distances can be displayed. This feature is not available in the current imaging systems used for this purpose.

Definition of The Figures

FI G. 1 . is an illustration of a block diagram of the system’s components.

Description of The Components And Parts Of The I nvention

The components shown in the figures prepared for a better explanation of the is numbered separately and explanation of each number is given below.

1 . Secondary mirror

2. Primary mirror

3. Central aperture of primary mirror

4. Antenna

5. Receiver

6. Pan-Tilt

7. Scene/ Object Detailed Description of The I nvention

The scene/ object (7) is the thing that is desired to be detected. The primary mirror(2) is used to collect the electromagnetic wave radiation in millimeter wave and terahertz bands. The secondary mirror(1 ) is used to focus this electromagnetic wave on the antenna(4) . The central aperture(3) on the primary mirror is used to collect electromagnetic wave reflected from the secondary mirror(1 ) on the antenna(4) . The antenna(4) converts the electromagnetic wave radiation in the millimeter wave and terahertz bands to electrical current and receiver(5) is used to convert the millimeter waves and terahertz to voltage. This is standard working principle of a scanning system .

I n a possible embodiment of the invention, in order to provide the variable-focal length feature to the optical system, the antenna(4) and the secondary mirror(1 ) can be fixed and the primary mirror(2) can be moved towards the secondary mirror(1 ) .

I n an another embodiment of the invention, in order to provide the variable-focal length feature to the optical system , the distance between the secondary mirror(1 ) and the antenna(4) may be fixed, then fixing the primary mirror’s(2) position, secondary mirror(1 ) and the antenna(4) can be moved as they have a constant distance between them.