Coded Aperture Imaging (CAI) plays a high performance in remote radiation measurement, an imaging method using high-energy radiation with a spectrum raging from x ray to γ ray has found many applications, including high-energy astronomy and environment monitoring. The kernel of CAI is the coded mask (encoding array) with the relevant decoding array which are usually designed jointly to reconstruct a perfect or near-perfect original image. In this paper, we've developed a novel square-hole based CAI system which is predicted to have good properties and sensitivity. The coded aperture (CA) is designed to be a (4N+1)×(4N+1) area mask with a (2N+1)×(2N+1) area square hole transparent for gamma-ray(N is a natural number, implying the size of coding scale). In this method, a decoding function is structured to ensure the point spread function being a δ function. Unlike conventional pinhole imaging, by sampling the projection of a large square hole as a coded arrays, a high resolution imaging can be reconstructed, meanwhile a highly detection efficiency is obtained. Compared to the widely used Modified Uniformly Redundant Array (MURA) coding pattern, the square-hole has its remarkable characteristics. The square-hole is more alterable meaning that the coding numbers of a certain square-hole mask is decided by the sampling precision of detector, thus providing the user with a wider selection of coded aperture patterns to match his particular needs.
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