RESUMO
This paper presents a method for directly estimating slope values in a noisy piecewise linear function. By imposing a Markov structure on the sequence of slopes, piecewise linear fitting is posed as a maximum a posteriori estimation problem. A dynamic program efficiently solves this by traversing a linearly growing trellis. The alternating maximization algorithm (a kind of pseudo-EM method) is used to estimate the model parameters from data and its convergence behavior is analyzed. Ultrasound shear wave imaging is presented as a primary application. The algorithm is general enough for applicability in other fields, as suggested by an application to the estimation of shifts in financial interest rate data.
RESUMO
An expression for the required special bandwidth of a computer generated hologram is desired using results from the theory of frequency modulation. The expression is the same as a rule of thumb first presented by Lee. A simple quantization error model is presented for one type of nondetour phase class. It is shown that this hologram may be used to achieve a near optimum simulation of the quantization problem for random phase images.
RESUMO
An expression for the required special bandwidth of a computer generated hologram is desired using result from the theory of frequency modulation. The expression is the same as a rule of thumb first presented by Lee. A simple quantization error model is presented for one type of nondetour phase class. It is shown that this hologram may be used to achieve a near optimum simulation of the quantization problem for random phase images.
RESUMO
An analysis of the errors present in the Lohmann hologram of a random phase image is undertaken. A Lohmann hologram in which the magnitude information and the phase information are modulated across the same direction is derived. This structure is used for detailed 1-D computer simulations of image reconstruction for Lohmann-type holograms. Qualitative and quantitative observations are made about the mean square error across the reconstructed image. These observations are then shown to compare well with theoretical predictions from a statistical error model.
RESUMO
A general fidelity criterion and a procedure are developed to evaluate the performance of different detourphase-type computer-generated holograms. Three types of detour-phase hologram are evaluated and compared using both the aforementioned procedure and experimental data.
