Tham khảo tài liệu 'optical imaging and spectroscopy phần 2', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 38 GEOMETRIC IMAGING Cross correlation with decoding pattern Figure Base transmission pattern tiled mask and inversion deconvolution for p 5. MURA coded aperture pattern for p 5 Pinholes in code 12 Cross correlation with decoding pattern Figure Base transmission pattern tiled mask and inversion deconvolution for p 11. MURA coded aperture pattern for p 11 Pinholes in code 60 PINHOLE AND CODED APERTURE IMAGING 39 Tiled aperture pattern 20 40 60 80 100 20 40 60 80 100 Figure Base transmission pattern tiled mask and inversion deconvolution for p 59. MURA coded aperture pattern for p 59 Pinholes in code 1740 implemented under cyclic boundary conditions rather than using zero padding. In contrast with a pinhole system the number of pixels in the reconstructed coded aperture image is equal to the number of pixels in the base transmission pattern. Figures are simulations of coded aperture imaging with the 59 X 59-element MURA code. As illustrated in the figure the measured 59 X 59-element data are strongly positive. For this image the maximum noise-free measurement value is 100 and the minimum value is 58 for a measurement dynamic range of 2. We will discuss noise and entropic measures of sensor system performance at various points in this text in our first encounter with a multiplex measurement system we simply note that isomorphic measurement of the image would produce a much higher measurement dynamic range for this image. In practice noise sensitivity is a primary concern in coded aperture and other multiplex sensor systems. For the MURA-based coded aperture system Gottesman and Fenimore 102 argue that the pixel signal-to-noise ratio is SNRj Nfij _ pNfj N P fki Pki Bki where N is the number of holes in the coded aperture and Bkl is the noise in the kl th pixel. The form of the SNR in this case is determined by signal-dependent or shot noise. We discuss the noise sources in electronic optical detectors in Chapter 5 and 40 GEOMETRIC .
