Search results for "Focal shift"

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Focal shift in optical waves with off-axis focus

2003

We present a formulation for a suitable description of the focal shift in optical waves that have an off-axis focus. This shift that is primarily produced along the chief axis is given in terms of the focal distance and depends only on a parameter that is named as the generalized Fresnel number. Any non-uniform, either truncated and non-apertured optical beam with off-axis focus may be considered.

DiffractionPhysicsWave propagationbusiness.industryOptical beamAstrophysics::Instrumentation and Methods for AstrophysicsPhysics::OpticsAtomic and Molecular Physics and OpticsElectronic Optical and Magnetic MaterialsOpticsBessel beamFocal lengthFresnel numberElectrical and Electronic EngineeringPhysical and Theoretical ChemistryFocus (optics)businessFocal shiftOptics Communications
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Inverse focal shift: A new effect in truncated cylindrical waves

1999

We report on a general analytical procedure to analyse the axial focusing properties of uniform cylindrical waves truncated by a rectangular window. The resulting on-axis diffraction pattern explicitly depends on the square of the window height-to-width ratio. Depending on the value of this parameter, different kinds of axial behaviour are observed. In particular, it is found that for low values of this parameter and low Fresnel number, instead of the expected focal-shift effect, an inverse focal-shift phenomenon can appear, i.e. the maximum of the axial-irradiance distribution is displaced further away from the window.

PhysicsDiffractionDistribution (mathematics)Opticsbusiness.industryMathematical analysisWindow (computing)InverseFresnel numberbusinessAtomic and Molecular Physics and OpticsFocal shiftSquare (algebra)Journal of Modern Optics
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