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Speckle phenomena in optics12/10/2023 In fact, the contrast of the speckle pattern may actually increase. The Detector Rectangle will still calculate a coherent superposition of all the rays landing on any given pixel, and the speckle pattern will remain. ![]() If you then apply a non-zero Coherence Length to the source, all you will be doing is creating more randomness to the phase of the rays. ![]() Duplicating this with rays in non-sequential OpticStudio requires a random phase surface (say using a custom Grid Sag Surface). In this case, each point on the scattering surface can be thought of as a randomly-phased point source. First, speckle is created via a superposition of randomly phased waves, e.g., when reflecting a collimated laser beam from a scattering surface, and viewing the light on an observation screen placed some distance away from the scattering surface. 8.8 which essentially shows how the speckle contrast falls off as a function of the product of source bandwidth and modal delay time for a step-index think you have the right idea conceptually, but unfortunately I don’t think your approach will work in non-sequential OpticsStudio. See Goodman, Speckle Phenomena in Optics, 2nd ed., Fig. For your problem, I think if you calculate the modal time dispersion of your fiber (i.e., the temporal width of the impulse response) and make sure that it exceeds one over the bandwidth of your source (i.e., the coherence time of your source) by at least of factor of 2 or more, then you may be able to mitigate speckle. In reality, the speckle should only diminish as the temporal coherence goes down. The contrast of the speckle pattern therefore increases as the coherence length decreases - again, this is simply a result of the non-physical way that OpticStudio implements coherence. However, upon reducing the coherence length, speckle arises simply because the random phasing that OpticStudio applies is becoming more significant. With a coherence length set to a value that is larger than the propagation distance, the coherent irradiance is uniform as expected: It’s just a collimated beam falling on a Detector Rectangle. ![]() Here is a very simple example to illustrate. The way OpticStudio implements temporal coherence is based on a very simple (non-physical) approach that only provides a crude approximation in certain cases, such as a reduction in fringe pattern visibility that is accompanied by the presence of a speckle pattern. To model temporal coherence correctly, the rays would have to be combined differently, in a much more complicated fashion that transitions from fully coherent to fully incoherent as the relative path differences between rays increases. [Mod note: moved to more appropriate forum for OS-related think you have the right idea conceptually, but unfortunately I don’t think your approach will work in non-sequential OpticStudio. If you have any ideas, please let me know. Next, I checked 'coherent iradiance' by placing the detector in Illumination stop position, but there was no difference. I change this design to non-sequential, set the coherence length of the source to 8mm, and change the z-position of each source (for example, -10mm.). How can I simulate the speckle image in this situation? The fiber I use is 200um core size, and the total core size of the bundle is about 6mm. ![]() (Specle image simulation when sampling at least two cores) My purpose is to remove Speckle by making each core length of Multi-mode fiber bundle longer than Coherence length, and to know the minimum core length, I would like to perform Speckle Image simulation at Illumination STOP according to the each core length. The laser I use is 266nm DPSS Laser, and the C.L. Hello everyone, I have difficulty doing Speckle Image simulation of Laser Source.
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