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Absolute calibration #2

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raacampbell opened this issue Jun 4, 2019 · 5 comments
Open

Absolute calibration #2

raacampbell opened this issue Jun 4, 2019 · 5 comments
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enhancement New feature or request

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@raacampbell
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raacampbell commented Jun 4, 2019

Need to make calibration files which contain an image derived from a single-mode fibre at a known distance. We need a way of implementing that. We can then use this to get an absolute measure of wavefront.

@raacampbell raacampbell added the enhancement New feature or request label Jun 4, 2019
@raacampbell
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raacampbell commented Jun 4, 2019

Add dws.fibrephase which calculates the phase change over the pupil created by a point source a known distance away. 027a59a

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To confirm this works: Mount camera on a translation stage. Obtain two measurements a known small distance apart (e.g. 200μm apart) and measure the phase change. Check that dws.fibrephase returns the same answer. If it's off by a small amount, can this be explained by the sensor/diffuser distance being a little off? If so, correct it and try again.

If all looks good, then it should be possible to use the above rig to derive a precise value for the sensor/diffuser distance.

Once this is all nailed, then it should be possible to use a reference image that is associated with a known wavefront curvature.

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raacampbell commented Jun 6, 2019

Not analysed carefully, but looks good so far. A good analysis would be to fit the recorded wavefronts and use that to estimate distance moved by the camera.

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Based on theoretical wavefronts we can determine distance sensor has moved to great accuracy: 9ddb5f6

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The real differences in curvature are similar, but I've not turned these into distances from the sensor yet.

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