|
|
| Defocus |
|
Defocus is measured with respect to the focal plane of the Shack
Hartmann wavefront sensor. Our wavefront sensor analysis software Sensoft gives
precise indications for correcting the defocus.
|
|
| Tilt |
|
Tilt is measured with respect to the center of the reference frame.
|
|
| Coma |
|
This is the on-axis coma, and includes the coma due to the shape of the optical elements as well as due to their misalignment.
The correction achieved using the diagnostics from Sensoft will correct
the coma due to both effects. See how coma
originates due to the misalignment of optical elements.
|
|
| Spherical aberration |
|
Can arise due to the use of the wrong focal plane (or, equivalently, the wrong spacing between the elements). It can also be due to
the wrong shapes of the optical elements (conic coefficients). Sensoft suggests by
how much the focal plane should be shifted to correct the observed SA. Temperature effects can also play a role.
|
|
| Astigmatism |
|
Astigmatism can be inherent in the optics. It can also be due to support problems, as any imbalance in the forces applied by
the supports will result in astigmatism. To be used in conjunction with the wavefront (or mirror surface) plot to identify which supports are
not correctly adjusted. The orientation of the optical elements can be changed relative to each other to minimize this aberration.
|
|
| Triangular
Coma |
|
If this has a high value, look for problems with the 3 fixed points.
|
|
| Quadratic
Astigmatism |
|
A high value indicates the presence of support problems with 4-fold symmetry (like the 4 lateral fixed points).
|
Zernikes and