Multispectral illumination and image processing techniques for active millimeter-wave concealed object detection

Zhang, Lixiao; Stiens, Johan; Elhawil, Amna; Vounckx, Roger

doi:10.1364/ao.47.006357

Cited by 11 publications

(13 citation statements)

References 16 publications

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“…The NETD associated with this noise can be calculated by [21] NETD thermal 4T sys B RF τ p K; (9) where the factor of 4 comes from the losses of Dicke switching and polarization splitting, T sys is the total system noise, and τ is the integration time. Using the values from Table 2 gives a thermal noise limited NETD of 0.3 and 0.9 K (for a 1 s integration time) for the V and H channels, respectively.…”

Section: B Thermal Noisementioning

confidence: 99%

“…Combining Eqs. (8), (9), and (10) gives a total NETD of The thermal noise from the front end is not dependent on the optical power; however, the shot noise and TIA thermal noise terms decrease with increasing optical power. The optical power can be increased by using higher-power lasers, in which case the frontend thermal noise becomes the dominant term.…”

Section: B Thermal Noisementioning

confidence: 99%

“…1) [7], which can result in large radiometric temperature contrasts within a scene of interest between reflective objects and emissive objects at ambient temperatures. Indoor applications typically require either an active source or highly sensitive passive mmW sensors [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Passive 77 GHz millimeter-wave sensor based on optical upconversion

et al. 2012

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A passive millimeter-wave (mmW) sensor operating at a frequency of 77 GHz is built and characterized. The sensor is a single pixel sensor that raster scans to create an image. Optical upconversion is used to convert the incident mmW signal into an optical signal for detection. Components were picked to be representative of a single element in a distributed aperture system. The performance of the system is analyzed, and the noise equivalent temperature difference is found to be 0.5 K (for a 1 s integration time) with a diffraction limited resolution of ~8 mrad. Representative images are shown that demonstrate the phenomenology associated with this spectrum.

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Section: B Thermal Noisementioning

confidence: 99%

Section: B Thermal Noisementioning

confidence: 99%

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Passive 77 GHz millimeter-wave sensor based on optical upconversion

et al. 2012

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“…Millimeter-wave imaging is a subject of both long and increasing interest [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. This interest is driven by the capabilities of radiation in this spectral region to penetrate covering obstructions and to do so with enough angular resolution for useful imaging.…”

Section: Introductionmentioning

confidence: 99%

Range resolved mode mixing in a large volume for the mitigation of speckle and strategic target orientation requirements in active millimeter-wave imaging

et al. 2015

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In spite of many reports of active millimeter-wave imaging in the literature, speckle and requirements for cooperative target orientation significantly reduce its practical usefulness. Here we report a new technique, range resolved mode mixing (RRMM), which significantly mitigates both of these issues. It also provides a three-dimensional (3D) image. RRMM accomplishes this by combining multimode illumination (which eliminates the requirement for cooperative target orientation) with range resolution (which provides statistical independence of speckle patterns for averaging and the 3D image). The use of a 5W extended interaction klystron amplifier results in large signal margins in the 50 m scale atrium of the Physics Department at Ohio State University. It appears that there are a number of scenarios out to a range of 1 km for which this approach is useful to provide 3D images, with minimal speckle, and no requirement for cooperative target orientation.

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“…It means that the indoor PMMW image shows the low temperature contrast between the target and the background which is insufficient to recognize the target [4,5]. In general, active systems are used to improve the image contrast and they usually exploit coherent illumination which causes the source of significant interference effects or speckle [6,7]. Polarimetric imaging is also one of the methods used to enhance the target discriminability because using polarization diversity allows one to obtain additional information on the shape and material of the surface and can be an additional parameter for the recognition of objects on the basis of their radio images in the millimeter-wave range [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Linear Polarization Sum Imaging in Passive Millimeter-Wave Imaging System for Target Recognition

Kim¹,

Moon²,

Kim³

et al. 2013

PIER

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Abstract-In passive millimeter-wave imaging systems used indoors, the radiometric temperature contrast is barely enough for coarse object detection, being usually insufficient for recognition due to the absence of cold sky. The image contrast results from a combination of emissivity and reflectivity which are dependent on the dielectric constant of objects, the angle of incidence, and the polarization direction. To improve the capability of target recognition, we proposed the linear polarization sum imaging method which is based on the combination of the different polarization images for increasing the intensity contrast between the target area and the background area. In order to capture the linear polarization sum images of a metal sphere, a metal and a ceramic cup, we designed W-band quasi-optical imaging system which can generate the polarization dependent images by manually changing the linear polarization direction of its radiometer receiver from 0 to π/2 by the step size of π/8. The theoretical and experimental results of the linear polarization sum imaging show that it is capable for achieving good image quality enough to recognize the target.

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Multispectral illumination and image processing techniques for active millimeter-wave concealed object detection

Cited by 11 publications

References 16 publications

Passive 77 GHz millimeter-wave sensor based on optical upconversion

Passive 77 GHz millimeter-wave sensor based on optical upconversion

Range resolved mode mixing in a large volume for the mitigation of speckle and strategic target orientation requirements in active millimeter-wave imaging

Linear Polarization Sum Imaging in Passive Millimeter-Wave Imaging System for Target Recognition

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