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APS-2BM-MIC / ipython-user2bmb

ipython configurations for the tomography instrument
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scanDelta seems too small #40

Closed prjemian closed 6 years ago

prjemian commented 6 years ago

When using this calculation: theta = startPos + scanDelta * frameNumber to calculate the theta corresponding to tomography image projections, the starting position matches the actual starting theta value but the ending theta value is exactly one scanDelta short of endPosition.

For example:

this is computer and reported by EPICS

from the formula above, we calculate:

We are missing the image projection at endPosition (180 degrees in this case).

We are acquiring exactly 1500 image projections (that's in the HDF5 file). Seems as if scanDelta should be slightly larger. Or, are we getting an image at endPosition?

@timmmooney: Which is actually correct?

timmmooney commented 6 years ago

Hi Pete,

The last image is at theta = EndPos - scanDelta. I think you would not want an image at 180 degrees in the data set, because it contains no new information. Also, this choice would allow you to get two tomographs with exactly the same theta angles by rotating 360 degrees, etc.

Tim Mooney (mooney@aps.anl.gov) (630)252-5417 Beamline Controls Group (www.aps.anl.gov) Advanced Photon Source, Argonne National Lab

From: Pete R Jemian notifications@github.com Sent: Saturday, August 18, 2018 4:48:00 PM To: APS-2BM-MIC/ipython-user2bmb Cc: Mooney, Tim M.; Mention Subject: [APS-2BM-MIC/ipython-user2bmb] scanDelta seems too small (#40)

When using this calculation: theta = startPos + scanDelta * frameNumber to calculate the theta corresponding to tomography image projections, the starting position matches the actual starting theta value but the ending theta value is exactly one scanDelta short of endPosition.

For example:

this is computer and reported by EPICS

from the formula above, we calculate:

We are missing the image projection at endPosition (180 degrees in this case).

We are acquiring exactly 1500 image projections (that's in the HDF5 file). Seems as if scanDelta should be slightly larger. Or, are we getting an image at endPosition?

@timmmooneyhttps://github.com/timmmooney: Which is actually correct?

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHubhttps://github.com/APS-2BM-MIC/ipython-user2bmb/issues/40, or mute the threadhttps://github.com/notifications/unsubscribe-auth/AGfnl0P0WFL6uTooB2dXnnwyCUbW7g9Mks5uSIuQgaJpZM4WCvGu.

prjemian commented 6 years ago

@timmmooney: Thanks for confirming this. I now understand.