Die Theorie der Beleuchtung

Michel, Kurt

doi:10.1007/978-3-7091-4023-9_4

Cited by 1 publication

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“…Stochastic phase contrast with incoherent superposition of uniform intensity U sing broad spectral response of an unfiltered tungsten incandescent lamp with a broadband photomultiplier, together with reduced spatial coherence and a highaperture imaging lens, we obtained a low contrast intensity structure in the defocused detector plane, DP (figure 3). This structure (figure 2), looks more like phase contrast by defocusing rather than a speckle pattern [7,8]. It was scanned with a detector pinhole roughly ten times larger than the corresponding speckle size of high-coherence illumination and will be called in this paper, stochastic phase contrast by defocusing.…”

Section: Introductionmentioning

confidence: 99%

Removing Ambiguities in Surface Roughness Measurement

Leonhardt

Tiziani

1982

Optica Acta: International Journal of Optics

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Abstract.A new method is presented for the measurement df surface roughness in the range R. ~ 0·05-1 0 /lm. The data from a strongly defocused lowcontrast image of a rough surface is scanned, and the contrast value, C = (JJ(I> , is processed. A relatively low degree of spatial and temporal coherence, combined with a relatively high-image aperture and a detector aperture (which is much wider than the nominal speckle width of the corresponding highly coherent speckle pattern) led to important instrumental advantages, e.g., illumination by an incandescent lamp, simple photodetectors, short measuring times and simple, inexpensive, compact construction. The superposition of uniform intensity to the phase contrast structure, which leads to a strictly monotonic dependence of the measured contrast over a very wide range of the roughness values R. is of great importance. Practical measurements of metallic surface standards are reported and discussed, and the theoretical aspects of the superposition of uniform intensity are pointed out with the help of a new analytic expression for the stochastic contrast.

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Section: Introductionmentioning

confidence: 99%