Effects of foreoptics clocking errors

Is spot size sensitive to foreoptics clocking errors?




With a clocking error of 0.05° (equivalent to 44μm along the circumference of the 4" diameter ellipsoid) the spot is still diffraction limited.
A clocking error of 0.25° (equivalent to 220μm along the circumference of the 4" diameter ellipsoid) generates a spot between 300 and 400μm in diameter.
A clocking error of 0.70° (equivalent to 616μm along the circumference of the 4" diameter ellipsoid) generates a spot that is about 900μm in diameter.
The spot size is about 10 times less sensitive to clocking errors of the hyperboloid. That is, a clocking error of 0.50° of the hyperboloid creates about the same spot size as a clocking error of 0.05° of the ellipsoid ... and so on for the larger angles. However, the hyperboloid is much smaller, such that the 0.50° clocking error is equivalent to 111μm along the circumference of the hyperboloid. Similarly, a 2.50° clocking error is equivalent to 554μm along the circumference of the hyperboloid, and a 7.00° clocking error is equivalent to 1,552μm along the circumference.


What if both the ellipse and the hyperbola are mis-clocked?





The second set of spot diagrams shows what can happen when the ellipse has a clocking error of +0.40° and the hyperbola has one of a range of clocking errors. In this case, the hyperbola can actually mitigate the effects of the ellipse clocking error somewhat. Or it can make things even worse.

What happens at the detector as the spot size at the foreoptics focus changes?

In the high-res mode, spot sizes at the detector are comparable to those at the foreoptics focus - about 10% smaller.