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Fix edge cases of hwp offcenter correction #1386

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Fix edge cases of hwp offcenter correction #1386

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7e944ec
fix offcenter
ykyohei Sep 17, 2025
ad989a6
debug
ykyohei Sep 19, 2025
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46 changes: 35 additions & 11 deletions sotodlib/hwp/g3thwp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -642,22 +642,46 @@ def eval_offcentering(self, solved):
"""

logger.info('Remove offcentering effect from hwp angle and overwrite')
# Calculate offcentering from where the first reference slot was detected by the 2nd encoder.
if solved["ref_indexes_1"][0] > self._num_edges/2-1:
offcenter_idx1_start = int(solved["ref_indexes_1"][0]-self._num_edges/2)
offcenter_idx2_start = int(solved["ref_indexes_2"][0])
# Find the first point where two encoder data are available
# and offcentering is calculable
t1_0 = solved['fast_time_1'][solved['ref_indexes_1']][0]
t2_0 = solved['fast_time_2'][solved['ref_indexes_2']][0]
for i1_start in solved["ref_indexes_1"]:
if solved['fast_time_1'][i1_start] > t2_0:
break
else:
raise ValueError('Cannot correct offcentering because '
'two encoder data do not overlap')
for i2_start in solved["ref_indexes_2"]:
if solved['fast_time_2'][i2_start] > t1_0:
break
else:
offcenter_idx1_start = int(solved["ref_indexes_1"][1]-self._num_edges/2)
offcenter_idx2_start = int(solved["ref_indexes_2"][0])
raise ValueError('Cannot correct offcentering because '
'two encoder data do not overlap')
t1_start = solved['fast_time_1'][i1_start]
t2_start = solved['fast_time_2'][i2_start]
if t1_start <= t2_start:
if i1_start >= int(self._num_edges/2):
i1_start -= int(self._num_edges/2)
i2_start -= self._num_edges
else:
i2_start -= int(self._num_edges/2)
else:
if i2_start >= int(self._num_edges/2):
i1_start -= self._num_edges
i2_start -= int(self._num_edges/2)
else:
i1_start -= int(self._num_edges/2)

# Calculate offcentering to the end of the shorter encoder data.
if len(solved["fast_time_1"][offcenter_idx1_start:]) > len(solved["fast_time_2"][offcenter_idx2_start:]):
idx_length = len(solved["fast_time_2"][offcenter_idx2_start:])
if len(solved["fast_time_1"][i1_start:]) > len(solved["fast_time_2"][i2_start:]):
idx_length = len(solved["fast_time_2"][i2_start:])
else:
idx_length = len(solved["fast_time_1"][offcenter_idx1_start:])
idx_length = len(solved["fast_time_1"][i1_start:])
offcenter_idx1 = np.arange(
offcenter_idx1_start, offcenter_idx1_start+idx_length-1)
i1_start, i1_start+idx_length-1)
offcenter_idx2 = np.arange(
offcenter_idx2_start, offcenter_idx2_start+idx_length-1)
i2_start, i2_start+idx_length-1)
# Calculate the offset time of the encoders induced by the offcentering.
offset_time = (solved["fast_time_1"][offcenter_idx1] -
solved["fast_time_2"][offcenter_idx2])/2
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