Based on the propagation theory of partially coherent light in the space-frequency domain, the anomalous spectral behavior and spectral switches in the far field of partially coherent and polychromatic light diffracte...Based on the propagation theory of partially coherent light in the space-frequency domain, the anomalous spectral behavior and spectral switches in the far field of partially coherent and polychromatic light diffracted at an aperture are studied. It is shown that, as compared with spatially fully coherent and polychromatic light whose spectral anomalies are induced only by aperture diffraction, the spectral anomalies and spectral switches of partially coherent and polychromatic light depend on the aperture diffraction, spatial correlationβ and bandwidth of the original spectrum. Detailed numerical calculations are made to illustrate the behavior of spectral switches of partially coherent and polychromatic light, and the results for spatially fully coherent and polychromatic light are treated as a special case ofβ=1 and included in our theory.展开更多
Surface light scattering enables contactless and fast measurements of surface roughness.A surface inclination alters the direction of the scattering beam and thus the measured surface roughness is calculated from the ...Surface light scattering enables contactless and fast measurements of surface roughness.A surface inclination alters the direction of the scattering beam and thus the measured surface roughness is calculated from the detected intensity distribution.Hence,an accurate sensor-surface alignment is necessary.In order to achieve tilt-independent roughness measurements,a model-based evaluation approach for polychromatic speckle patterns is presented.By evaluating the shape of the superposed speckles,which occur for polychromatic illumination,with regard to the distance to the scattering centre,surfaces with an Sa roughness value in the range of 0.8-3.2μm are measurable.Experimental investigations demonstrate that the influence of a surface tilt up to±1.25°on the roughness measurement is reduced by 90%.As a result,the robustness of the polychromatic speckle roughness measurement is improved,which allows to speed up the adjustment of the measurement system or the surface sample,respectively.展开更多
文摘Based on the propagation theory of partially coherent light in the space-frequency domain, the anomalous spectral behavior and spectral switches in the far field of partially coherent and polychromatic light diffracted at an aperture are studied. It is shown that, as compared with spatially fully coherent and polychromatic light whose spectral anomalies are induced only by aperture diffraction, the spectral anomalies and spectral switches of partially coherent and polychromatic light depend on the aperture diffraction, spatial correlationβ and bandwidth of the original spectrum. Detailed numerical calculations are made to illustrate the behavior of spectral switches of partially coherent and polychromatic light, and the results for spatially fully coherent and polychromatic light are treated as a special case ofβ=1 and included in our theory.
基金The project on which this article is based was funded by the Federal Ministry of Education and Research under the AiF CORNET promotion plan with the Number 232 EBG.
文摘Surface light scattering enables contactless and fast measurements of surface roughness.A surface inclination alters the direction of the scattering beam and thus the measured surface roughness is calculated from the detected intensity distribution.Hence,an accurate sensor-surface alignment is necessary.In order to achieve tilt-independent roughness measurements,a model-based evaluation approach for polychromatic speckle patterns is presented.By evaluating the shape of the superposed speckles,which occur for polychromatic illumination,with regard to the distance to the scattering centre,surfaces with an Sa roughness value in the range of 0.8-3.2μm are measurable.Experimental investigations demonstrate that the influence of a surface tilt up to±1.25°on the roughness measurement is reduced by 90%.As a result,the robustness of the polychromatic speckle roughness measurement is improved,which allows to speed up the adjustment of the measurement system or the surface sample,respectively.
