Table 1
Encoder positions of the HWP.
Encoder steps | Angle |
[deg] | |
|
|
Manual: | |
x | α = (x + 205) ∗ 0.08789 |
−205 ~ 3891 | 0 |
51 | 22.5° |
0 | 205 ∗ 0.08789 = 18.02 |
|
|
Revision: | |
0 | (11.4 ± 0.2) |
|
|
Difference: | |
(−6.6 ± 0.2) |
Notes. The table shows that the actual reference system for the HWP is offset by (−6.6 ± 0.2)° with respect to the reference system assumed in the manual. This results in a positive angle offset of 13.2° for the polarization channels (in the instrumental sense of rotation). One turn of the plate corresponds to 4096 encoder steps. An angle of 0° actually corresponds to an encoder position of 3966.
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