107 research outputs found
220GHz wideband 3D imaging radar for concealed object detection technology development and phenomenology studies
Part of the research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 312745.We present a 220 GHz 3D imaging ‘Pathfinder’ radar developed within the EU FP7 project CONSORTIS (Concealed Object Stand-Off Real-Time Imaging for Security) which has been built to address two objectives: (i) to de-risk the radar hardware development and (ii) to enable the collection of phenomenology data with ~1 cm3 volumetric resolution. The radar combines a DDS-based chirp generator and self-mixing multiplier technology to achieve a 30 GHz bandwidth chirp with such high linearity that the raw point response is close to ideal and only requires minor nonlinearity compensation. The single transceiver is focused with a 30 cm lens mounted on a gimbal to acquire 3D volumetric images of static test targets & materials.Publisher PD
Multiplexed readout of kinetic inductance bolometer arrays
Kinetic inductance bolometer (KIB) technology is a candidate for passive
sub-millimeter wave and terahertz imaging systems. Its benefits include
scalability into large 2D arrays and operation with intermediate cryogenics in
the temperature range of 5 -- 10 K. We have previously demonstrated the
scalability in terms of device fabrication, optics integration, and cryogenics.
In this article, we address the last missing ingredient, the readout. The
concept, serial addressed frequency excitation (SAFE), is an alternative to
full frequency-division multiplexing at microwave frequencies conventionally
used to read out kinetic inductance detectors. We introduce the concept, and
analyze the criteria of the multiplexed readout avoiding the degradation of the
signal-to-noise ratio in the presence of a thermal anti-alias filter inherent
to thermal detectors. We present a practical scalable realization of a readout
system integrated into a prototype imager with 8712 detectors. This is used for
demonstrating the noise properties of the readout. Furthermore, we present
practical detection experiments with a stand-off laboratory-scale imager.Comment: 7 pages, 6 figure
SAM Fails to Segment Anything? -- SAM-Adapter: Adapting SAM in Underperformed Scenes: Camouflage, Shadow, and More
The emergence of large models, also known as foundation models, has brought
significant advancements to AI research. One such model is Segment Anything
(SAM), which is designed for image segmentation tasks. However, as with other
foundation models, our experimental findings suggest that SAM may fail or
perform poorly in certain segmentation tasks, such as shadow detection and
camouflaged object detection (concealed object detection). This study first
paves the way for applying the large pre-trained image segmentation model SAM
to these downstream tasks, even in situations where SAM performs poorly. Rather
than fine-tuning the SAM network, we propose \textbf{SAM-Adapter}, which
incorporates domain-specific information or visual prompts into the
segmentation network by using simple yet effective adapters. Our extensive
experiments show that SAM-Adapter can significantly elevate the performance of
SAM in challenging tasks and we can even outperform task-specific network
models and achieve state-of-the-art performance in the task we tested:
camouflaged object detection and shadow detection. We believe our work opens up
opportunities for utilizing SAM in downstream tasks, with potential
applications in various fields, including medical image processing,
agriculture, remote sensing, and more
Learning to Detect Open Carry and Concealed Object with 77GHz Radar
Detecting harmful carried objects plays a key role in intelligent
surveillance systems and has widespread applications, for example, in airport
security. In this paper, we focus on the relatively unexplored area of using
low-cost 77GHz mmWave radar for the carried objects detection problem. The
proposed system is capable of real-time detecting three classes of objects -
laptop, phone, and knife - under open carry and concealed cases where objects
are hidden with clothes or bags. This capability is achieved by the initial
signal processing for localization and generating range-azimuth-elevation image
cubes, followed by a deep learning-based prediction network and a multi-shot
post-processing module for detecting objects. Extensive experiments for
validating the system performance on detecting open carry and concealed objects
have been presented with a self-built radar-camera testbed and collected
dataset. Additionally, the influence of different input formats, factors, and
parameters on system performance is analyzed, providing an intuitive
understanding of the system. This system would be the very first baseline for
other future works aiming to detect carried objects using 77GHz radar.Comment: 12 page
CamoDiffusion: Camouflaged Object Detection via Conditional Diffusion Models
Camouflaged Object Detection (COD) is a challenging task in computer vision
due to the high similarity between camouflaged objects and their surroundings.
Existing COD methods primarily employ semantic segmentation, which suffers from
overconfident incorrect predictions. In this paper, we propose a new paradigm
that treats COD as a conditional mask-generation task leveraging diffusion
models. Our method, dubbed CamoDiffusion, employs the denoising process of
diffusion models to iteratively reduce the noise of the mask. Due to the
stochastic sampling process of diffusion, our model is capable of sampling
multiple possible predictions from the mask distribution, avoiding the problem
of overconfident point estimation. Moreover, we develop specialized learning
strategies that include an innovative ensemble approach for generating robust
predictions and tailored forward diffusion methods for efficient training,
specifically for the COD task. Extensive experiments on three COD datasets
attest the superior performance of our model compared to existing
state-of-the-art methods, particularly on the most challenging COD10K dataset,
where our approach achieves 0.019 in terms of MAE
Fast high-resolution terahertz radar imaging at 25 meters
We report improvements in the scanning speed and standoff range of an ultra-wide bandwidth terahertz (THz) imaging radar for person-borne concealed object detection. Fast beam scanning of the single-transceiver radar is accomplished by rapidly deflecting a flat, light-weight subreflector in a confocal Gregorian optical geometry. With RF back-end improvements also implemented, the radar imaging rate has increased by a factor of about 30 compared to that achieved previously in a 4 m standoff prototype instrument. In addition, a new 100 cm diameter ellipsoidal aluminum reflector yields beam spot diameters of approximately 1 cm over a 50×50 cm field of view at a range of 25 m, although some aberrations are observed that probably arise from misaligned optics. Through-clothes images of concealed pipes at 25 m range, acquired in 5 seconds, are presented, and the impact of reduced signal-to-noise from an even faster frame rate is analyzed. These results inform the requirements for eventually achieving sub-second or video-rate THz radar imaging
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