A Fast Spatial-domain Terahertz Imaging Using Block-based Compressed Sensing
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A Fast Spatial-domain Terahertz Imaging Using Block-based Compressed Sensing Byung-Min Hwang & Sang Hun Lee & Woo-Taek Lim & Chang-Beom Ahn & Joo-Hiuk Son & Hochong Park
Received: 28 January 2011 / Accepted: 10 August 2011 / Published online: 2 September 2011 # Springer Science+Business Media, LLC 2011
Abstract A fast imaging method for a spatial-domain terahertz imaging system based on compressed sensing is proposed. Observing that the correlation between image pixels is localized, the image reconstruction in compressed sensing is performed on a block basis, resulting in a reduced computational load with no degradation in image quality. By applying the proposed method to a conventional spatial-domain terahertz imaging system, it was verified that a 128×128 image reconstructed using 30% measurements has the equivalent quality to that done using full measurements. The proposed method requires no additional hardware, and provides a general solution to fast spatial-domain terahertz imaging. Keywords Block reconstruction . Compressed sensing . Fast imaging . T-ray imaging
1 Introduction Imaging systems using terahertz wave (T-ray) have been widely used in the security, defect detection, and medical imaging fields [1–5]. The simplest imaging method acquires a signal for each pixel of the object using a raster scanning mode, which provides a high-quality image of the object by virtue of the high spatial resolution. This method, however, has the drawback of a slow image acquisition rate due to the sequential signal measurement done
Byung-Min Hwang, Sang Hun Lee and Woo-Taek Lim contributed equally to the study. B.-M. Hwang : W.-T. Lim : H. Park (*) Department of Electronics Engineering, Kwangwoon University, Seoul 139-701, Korea e-mail: [email protected] S. H. Lee : J.-H. Son (*) Department of Physics, University of Seoul, Seoul 130-743, Korea e-mail: [email protected] C.-B. Ahn Department of Electrical Engineering, Kwangwoon University, Seoul 139-701, Korea
J Infrared Milli Terahz Waves (2011) 32:1328–1336
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for each pixel [6, 7]. Therefore, a new technology for fast T-ray imaging is desirable for applications demanding fast imaging. Many researchers have developed methods for fast T-ray imaging in various ways. T-ray imaging methods that use detector or source arrays have been developed in order to solve the inherent speed limitations of sequential data acquisition [8, 9]. These methods, however, have the drawback of expensive and complex equipment. A fast T-ray imaging method based on compressed sensing (CS) was proposed in [6]; it acquires data at a subset of pixels and reconstructs an image using CS technology. This method, however, has a speed limitation because the detector in the Fourier plane is still moving in the raster scanning mode. A T-ray imaging method using a single detector without raster scanning was proposed in [7]. The T-ray beam passing the object is spatially modulated by a random pattern mask, and the resulting beam is transmitted to a single fixed detector. By sequentially changing the rand
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