TETX, TETY, TETZ: Tolerance on Element Tilts
TETX, TETY, and TETZ are used to analyze tilts of either a surface or a lens group about the X, Y, or Z axes, respectively. The two surface numbers defined by Int1 and Int2 indicate the beginning and ending surfaces of a lens group. The min and max values are the tipping angles in degrees.
These tolerances require OpticStudio to insert a coordinate break surface before and after the lens group, and to use a dummy surface at the end of the group to return to the front vertex. The entire group may then be pivoted about a point as a unit. For this reason, TETX/Y/Z should not be used when the range of surfaces defined includes a coordinate break which is related to a following coordinate break outside the surface range controlled by the TETX/Y/Z by pickup solves. The hazard is if the two resulting tilt ranges overlap, then the position of the elements may not be what is intended. If you require this capability, search the help files for the discussion on TUTX, TUTY, and TUTZ.
TETX and TETY may also be used to model tilt of single surfaces, sometimes called "wedge", like TSTX and TSTY. TETX and TETY will work for surfaces of any type, including Standard surfaces and non-Standard surfaces, while TSTX and TSTY only work for Standard surfaces. To tilt a single surface using TETX or TETY, set Int1 and Int2 to the same surface number.
TETX and TETY by default pivot about the front vertex of a lens group, however it is often advantageous to pivot about some other point. This can be easily accomplished with the MPVT operand for the available types (front and rear vertex, front and rear mechanical edge, geometric center). Any other case is easily modeled by OpticStudio through the use of a dummy surface at the desired location. Change the starting surf (Int1) to be at the defined dummy surface, and the pivoting will be about that point. The first surface may be located anywhere with respect to the rest of the lens group; and so the tilt may be about any point. For example, well-designed lens mounts will pivot about the nodal point of a lens to maintain focus during alignment.
TETX, TETY, and TETZ operands may be nested. For example it is possible to analyze the tilt of one surface group defined by surfaces 5 through 20; while simultaneously analyzing tilts of elements defined by surfaces 5-8, 8-12, 14-20, etc. This capability can simulate the alignment errors of elements within an assembly, as well as the alignment error of the assembly as a whole. The nesting rules are fully described in the section "Nesting rules for Monte Carlo analysis".
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