ISSN:0950-0340    

DOI:10.1080/09500348714550231

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new strategy for signal and image reconstruction with incomplete information and partial constraints is defined. The main purpose of the first paper (part I) is to specify the conditions under which it is possible to extrapolate or to interpolate, in some regionW, the Fourier transform of a function having its support in some bounded regionV. With the aid of some very simple geometrical concepts it is shown, in particular, why spectral interpolation is possible to some extent, whereas infinite extrapolation is forbidden. At the cost of a less full representation of the object, it is therefore natural to formulate the deconvolution problems in terms of (weighted) spectral interpolation with partial extrapolation. The corresponding regularization principle, which is compared with that of Tikhonov, proves to be intimately related to the notion of resolution limit of the reconstruction process. In this context, the smallest eigenvalue of the operator to be inverted can be estimated analytically before setting the reconstruction process in motion. The corresponding analysis is developed by stressing the essential results directly involved in the interactive numerical implementation presented in part II: stability conditions, number of degrees of freedom of the reconstruction process, etc. All the related technical aspects are presented in closed form.

ISSN:0950-0340    

DOI:10.1080/09500348714550241

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The quantum limits on measurements of small changes in the length of a Fabry-Perot cavity are calculated. The cavity is modelled by a pair of dissimilar mirrors oriented perpendicular to a one-dimensional axis of infinite extent. The continuous spectrum of spatial modes of the system is derived, and the electromagnetic field is quantized in terms of a continuous set of mode creation and destruction operators. Coherent state and squeezed vacuum-state excitations of the field are characterized by energy flow, or intensity, variables. The determination of small changes in the cavity length by observations of fringe intensity is considered for schemes in which the cavity is simultaneously excited by coherent and squeezed vacuum-state inputs. The contributions to the limiting resolution from photocount and radiation-pressure length uncertainties are evaluated. These properties of the Fabry-Perot cavity are compared with the corresponding results for the Michelson interferometer.

ISSN:0950-0340    

DOI:10.1080/09500348714550251

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Blood flow measurement is important in the diagnosis of circulatory disorders and the control of patient therapy. In clinical practice, a true non-contact method of measurement is advantageous because no sterilization is required and blood flow is not affected by the presence of a probe on the skin.

ISSN:0950-0340    

DOI:10.1080/09500348714550261

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Arrays of motifs, such as are found in half-tone images, may exhibit unwanted moiré fringes when they are generated by a scanning system which introduces a periodic displacement defect. It is shown that the fringes may be eliminated in the continued presence of the defect when it is in the direction of the scan lines, but cannot be suppressed when the displacement is perpendicular to this direction. The appropriate Fourier theory is presented and suppression of the moiré fringes for one particular defect is illustrated.

ISSN:0950-0340    

DOI:10.1080/09500348714550271

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The optical frequency response of a perfect lens partially masked by a retarder has been studied. The optical transfer function (OTF) of such a system depends upon the relative orientation of the analyser, placed at the output, relative to the slow and fast axes of the mask, and also on the relative aportioning of the lens aperture by the mask. The OTF of the system also depends upon the retardation introduced by the mask. In the present paper, we have computed the OTF of the masked lens for different values of the relevant parameters with and without the analyser at the output.

ISSN:0950-0340    

DOI:10.1080/09500348714550281

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A detailed analysis is provided of a non-Markov model of cavity population in which each emission gives rise to a random dead-time during which no further emissions can take place. Differential equations are derived for the generating functions governing the cavity population size. The moment structure of the population size is examined and explicit expressions for the first two moments are provided. The photon population statistics are shown to be antibunched for a wide choice of the population parameters. The detection process is analysed and an explicit expression is provided for the Hanbury Brown-Twiss type of correlation. It is further shown that an appropriate choice of the population parameters can produce a thermal stream with Lorentzian profile.

ISSN:0950-0340    

DOI:10.1080/09500348714550291

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

By means of both partial coherence theory and diffraction theory, the Lau effect with a sinusoidal phase grating in a double-grating configuration is analysed. The optical intensity distribution at the observation plane is obtained. This distribution is related to the modulation of the phase grating and the separation of the two gratings. The results are somewhat different from the case of double amplitude gratings.

ISSN:0950-0340    

DOI:10.1080/09500348714550301

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor