Two parameters are crucial to compute a good reconstruction: the number of projections and the angular coverage. Through several examples, we'll see their impact on the reconstructed image.
1- How many projections do we need?
In the previous posts, 180 1D-projections were used for computing a reconstruction corresponding to data collected with a step of 1° over an angular range of [0-180[. Is it enough? Do we need more or less projections?
Modify the number of projections used to compute a sinogram by changing the line 'var nbProj=180;' of the script sinogram.js.
- Compute different sinograms from Lena (or what you want) by choosing 36, 90, 180, and 360 projections (corresponding respectively to an angular increment of 5°, 2°, 1°, and 0.5°).
- For each sinogram, compute the weighted back-projection reconstruction (ramp filtration and reconstruction).
A moire pattern is clearly visible when the number of projections is decreasing.
>>> In a next post: The impact of the angular coverage [Link]
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