Abstract Nondestructive quality inspection with terahertz waves has become an emerging technology, especially in the automotive and aviation industries. Depending on specific application, different systems—either fully electronic or based optical laser pulses—cover frequency region from 0.1 THz up to nearly 10 provide high-speed volume inspections one hand high-resolution thickness determination other hand. In this paper, we present industrial applications, which have addressed our systems...

This paper presents a survey of the status five active THz imaging modalities which we have developed and investigated during last few years with goal to explore their potential for real-time imaging. We start out by introducing novel waveguide-based all-electronic system operates at 812 GHz. Its salient feature is 32-pixel linear detector array heterodyne-operated eighth subharmonic. in combination telescope optics object distances 2-6 m reaches data acquisition speed suited The second...

The sub-terahertz (THz) frequency band has proved to be a noteworthy option for nondestructive testing (NDT) of nonmetal aeronautics materials. Composite structures or laminates can inspected foreign objects (water debris), delaminations, debonds, etc., using sub-THz sensors during the manufacturing process maintenance. Given harmless radiation human body this band, no special security measures are needed operation. Moreover, frequency-modulated continuous-wave sensor used in study offers...

Radomes protecting sensitive radar, navigational, and communications equipment of, e.g., aircraft, are strongly exposed to the environment have withstand harsh weather conditions potential impacts. Besides their significance structural integrity of radomes, it is often crucial optimize composite structures for best possible radio performance. Hence, there exists a significant interest in non-destructive testing techniques, which can be used defect inspection radomes field use as well quality...

Many established terahertz imaging modalities are on one side restricted by the tradeoff between resolution and field of view such as in case focal plane arrays other suffer from a limited depth quasi-optical configurations. Furthermore, typical scanning solutions require time-consuming measurement procedures restrict significant potential industrial deployments technology. Imaging with sparse multistatic line combination digital beam forming (DBF) techniques enables us to overcome these...

We present thickness measurements with millimeter and terahertz waves using frequency-modulated continuous-wave (FMCW) sensors. In contrast to time-domain spectroscopy (TDS), our FMCW systems provide a higher penetration depth measurement rates of several kilohertz at frequency modulation bandwidths up 175 GHz. order resolve thicknesses below the Rayleigh resolution limit given by bandwidth, we employed model-based signal processing technique. Within this contribution, analyzed influence...

We present a rotational terahertz imaging system for inline nondestructive testing (NDT) of press sleeves the paper industry during fabrication. Press often consist polyurethane (PU) which is deposited by molding on metal barrels and its outer surface mechanically processed in several milling steps afterwards. Due to stabilizing polyester fiber mesh inlay, small defects can form sleeve’s backside already initial molding, however, they cannot be visually inspected until whole production...

We present difference-frequency stabilization of free-running distributed-feedback (DFB) diode lasers, maintaining a stable phase-lock to local oscillator (LO) signal. The technique has been applied coherent hybrid THz imaging which employs high-power electronic radiation source emitting at 0.62 and electro-optic detectors. the narrow-band emitter is mixed with difference frequency DFB laser pair. resulting intermediate phase-locked LO signal from radio-frequency generator using fast...

Abstract A novel photonic terahertz measurement system based on a frequency‐modulated continuous‐wave (FMCW) radar approach is presented. In previous works, fast frequency modulation has been demonstrated in connection with continuous wave spectroscopy setup the photomixing principle. this paper, both transmitter and receiver, contrast to rigid approach, reported. Hereby, bandwidths of more than 1.65 THz operation achieved. This corresponds an order magnitude what previously achieved by...

Abstract We present observations of parasitic frequency components in the emission spectrum typical photomixer sources for continuous wave (CW) terahertz generation. Broadband tunable systems are often used combination with direct power detectors, e.g., source and/or detector characterization. Here, spectral besides intended at difference two excitation lasers can significantly distort measurement results. In this work, appearance mixing signals is observed broadband measurements a...

Terahertz tomography is a promising method among non-destructive inspection techniques to detect faults and defects in dielectric samples. Recently, image quality was improved significantly through the incorporation of priori information off-axis data. However, this improvement has come at cost increased measurement time. To aim toward industrial applications, it therefore necessary speed up by parallelizing data acquisition employing multi-channel setups. In work, we present two tomographic...

A millimeter-wave (mmW) classifier system applied to images synthesized from a coded-aperture based computational imaging (CI) radar is presented. developed physical model of CI used generate the image dataset for classification algorithm. convolutional neural network (CNN) integrated with and trained using comprising mmW obtained directly model. k-fold cross validation technique during training process validate The concept enables reconstruction significantly reduced number back-scattered...

We present a hand-guided mobile terahertz imaging platform for non-destructive testing (NDT). The scanner acquires volumetric 3D image data using an integrated FMCW radar module in combination with line scanning optics and position encoder. Consisting of galvanometer mirror aspherical telecentric f-theta lens, the optical system enables B-scans perpendicular to manual motion over width 2 cm. guiding wheel allows precise movement along cracks welds, example, enabling inspection corresponding...

Imaging systems operating in the sub-terahertz frequency range have proven to be highly attractive devices for non-destructive testing applications. Especially modulated system concepts shown a great potential volume inspection industrial process and quality control, but often lack fast image acquisition times. We report on development of line array imaging The realized employs sparse consisting 12 emitters heterodyne receivers operates W band between 75 GHz 110 GHz. applied...

In recent years, many terahertz and millimeter wave technologies have evolved from a scientific background into very specific industrial contexts. One field of such "real-world" applications is non-destructive testing (NDT) for sub-surface defects in quality control product maintenance environments. this contribution, we present system combining an all-electronic 100 GHz transceiver with dielectric waveguide antenna sub-wavelength NDT imaging. We employ frequency-modulated continuous (FMCW)...

Abstract Terahertz technologies for non-destructive testing (NDT) are continuing to find their way into the industrial sector in context of very specific inspection tasks. Part this development is capability adapt terahertz systems such a that they can meet sometimes harsh challenges and requirements real-world scenarios. One scenario components with limited available measurement space. In particular, we show here NDT mica insulation generator bars turbogenerators at power plants, where an...

An active handheld millimeter wave imaging device for non-destructive testing has been developed. The system operates from 70 to 80 GHz and provides real-time capabilities with depth information. concept is based on the effective aperture approach in combination a sparse two-dimensional array of transmit receive antennas. designed contain antenna array, signal-multiplexing-unit, FPGA-data-acquisition signal synthesizers as well display visualization single enclosure. A USB 3.0 connection...

Terahertz tomography allows for non-contact tomographic inspection of dielectric materials without the need radiation protection measures. offers opportunity to inspect such objects from multiple angles not only by measuring absorption but also acquiring time-of-flight radiation. Hence, this technique facilitates reconstruction complete complex refractive index a sample under test. Even complicated surface structures can be imaged, provided feature size is above diffraction limit roughly...

The increasing industrial application of fiber reinforced plastics demands developments new techniques for non-destructive testing. sub-terahertz frequency band has proved to be a noteworthy option this task. Composite structures or laminates can inspected foreign inclusions, delaminations, debonds, etc., using sensors during the manufacturing process maintenance. In contribution we present our results modulated continuous wave terahertz imaging system in comparison with conventional NDT...

Objective: Pregnancy and childbirth require several medical examinations which can awaken feelings of modesty in women. Although little research has been done on this specific question, previous indicates that embarrassment could surface during examinations, particularly those requiring patient nudity. The aim the present study was to explore women's pregnancy, postnatal care. Method: Qualitative with phenomenological approach. Data were collected by tape-recorded open-ended interviews early...

Terahertz tomography is a non-contact inspection technique to image objects from multiple angles and reconstruct their 3D volume intensity time-of-flight transmission data, without the need for radiation protection measures. Unlike X-rays, terahertz subject strong diffraction refraction when propagating through dielectric materials, which often deteriorate reconstruction quality. Our solution this problem applies ray tracing, considering beam shape an <inline-formula...

The 3D range-migration algorithm (RMA) and its 2D equivalent, the omega-k algorithm, are employed in a wide range of applications where reconstruction synthetic aperture data is required, from satellite radar imaging planets over seismic earth crust, down to phased-array ultrasound ultrasonic application, recently in-line for non-destructive testing. These algorithms based on Fourier transforms share their time-complexity. This limits highly-resolved measurement be processed at high speeds...