Quality Control Security

MM-wave/THz imaging for security & non-destructive quality control

Due to property of mm-waves/THz-waves to penetrate through insulating materials, they are employed for various imaging approaches for identification of concealed weapons or dangerous objects for security applications but also for non-destructive inspection of product quality in-situ industrial production processes.

A so-called “active Imaging” approach requires a transmitter (Tx) or a source of mm-waves/sub mm-waves to “illuminate” the target, and a receiver (Rx), which can spatially resolving detect the incoming signal.

There are incoherent and coherent imaging systems

Incoherent imaging systems are the simplest. They just need a THz light source and a single envelope detector or an array of envelope detectors as a receiver. This works just like a flashlight for a photography camera or like a simple illumination to see the scene in the night. The difference is that THz light can be used not only in reflection mode but also in transmission mode, just like X-Ray approach, with the advantage that THz radiation is not ionizing and is compatible with live bodies.
ACST Sources and Detectors are well suited as THz illumination sources and receivers for incoherent imaging systems. ACST passive WG components are well suited to accomplish any system assembly.

Some applications may require different products. ACST experts can consult you on best available products from partner companies.

Picture resolution of incoherent imaging strongly depends on wavelength (frequency) of illumination.

Comparative pictures at two different frequencies: about 300GHz and about 500GHz of a cell phone and of scissors demonstrating the THz incoherent active imaging in reflection mode.

An example of transmission mode incoherent imaging can be seen here.

Figure 1: An example of setup for incoherent active imaging.

Picture resolution of incoherent imaging strongly depends on wavelength (frequency) of illumination. Figure 2 shows comparative pictures recorded by a multipixel THz camera at two different frequencies: 300GHz and 500GHz. Obviously, at 500GHz more details of the target can be distinguished.

Figure 2: THz incoherent active imaging in reflection mode.

Comparative pictures at two different frequencies: about 300GHz and about 500GHz of a cell phone (a), and of scissors (b

Coherent imaging systems are typically based on radar approaches, where the receiver provides not only amplitude but also phase information. This approach requires more system complexity, better purity of THz signal, more complex data processing approaches for reconstruction of video picture but offers opportunity to reconstruct 3-D images of the target from a single shot.
Most of applications employ approaches based on FMCW-radars. Spatial resolution of a FMCW-radar based imaging systems relies on output power of the Transmitter (Tx) and frequency bandwidth of the system.
ACST high-power AMC-s are best suited for FMCW-radar applications because they combine state-of-the-art output power at mm-/sub-mm-waves and frequency bandwidth. MixAMC systems are best suited for operating as receivers (Rx) in mm-wave/THz coherent imaging systems. For customization reasons are often required passive waveguide (WG) components like are Horn antennas, WG bends, WG tapers, Couplers, Attenuators, etc. ACST offers a variety of WG components for satisfaction of customer requirements.

Results of one of successfully finished R&D projects in this area with other academic and industrial partners can be seen here:

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