[PIPE2D-422] Check our intuition about the illumination of the fibers at LAM Created: 09/May/19  Updated: 24/Jul/19  Resolved: 24/Jul/19

Status: Done
Project: DRP 2-D Pipeline
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Task Priority: Normal
Reporter: ncaplar Assignee: ncaplar
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: PNG File 1s_difference.png     PNG File att_0_and_att_220.png     PNG File difference_att_0_and_att_220.png     PNG File summary_of_difference.png     PNG File time_15_and_time_1.png    
Story Points: 5
Reviewers: hassan

 Description   

Our two assumptions that we use when analyzing the LAM data are:

1. Changing the attenuator value does not change the illumination of the pupil. This makes sense given that attenuator is positioned before the illuminating sphere, which should fix any potential problems here. LAM took some defocused data with very different attenuator values (att_value=0 and att_value=220) so that this hypothesis could be tested. If needed we will ask for more data (perhaps even higher att_value).

2. Changing the exposure time changes the illumination of the pupil, due to shutter movement. LAM took some data for us with exp_time=15,12,9,6,3 and 1 second where we can test if we see this difference.

 Comments   
Comment by ncaplar [ 24/Jul/19 ]

1. a) att_0_and_att_220 shows the comparison on images with attenuator=0 and attenuator=220
b) difference_att_0_and_att_220 shows the residuals of subtracting these two images. Left hand side shows the residual, right hand side shows the ratio of the residuals.

We see the there is no structure in the residuals and the first assumption is satisfied.

2. a) time_15_and_time_1 shows the comparison of the images with exptime=15 sec and exptime=1.
b) difference_time_15_and_time_1 shows the residuals of subtracting these two images. Left hand side shows the residual, right hand side shows the ratio of the residuals.

It is clear that there is a difference! This confirm that there is effect as a function of exposure time.
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summary_of_difference.png shows the ratio of residuals as a function of y-coordinate. Different lines show difference from 15 sec exposures as a function of exposure times. You can see that we difference reduced very quickly (nonlinearly) as we approach 15 seconds exposures. As such I do not expect larger changes as we increase exposures times. This behavior is exactly as expected.

As such both assumptions are satisfied.

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