I want to tilt and decenter a group of surfaces (or a component group) without affecting the surfaces after the group. When I try to do adjust the first surface of the component group,

all surfaces after that initial surface are affected. How do I restrict the tilts and decenters so that they just affect the surfaces within the component group of interest?

Synopsis

Restricting tilts and decenters to component groups

Symptoms

Surfaces in an OSLO model are typically entered as sequential surfaces.* Because of this, if you change the tilt and/or decenter of a particular surface, all surfaces after that surface are affected. This Knowledge Base item describes how you can move certain surfaces while keeping later surfaces unchanged. * OSLO Premium offers the option of entering non-sequential surfaces, but that is a different topic.

 

Solution

"There are 2 approaches outlined below that are easily implemented: For purposes of this discussion, let's assume that the component you would like to tilt and decenter occupies surfaces 3 and 4 in your system. This corresponds to the surfaces of the negative lens in a standard triplet: The first approach involves making the surface directly following the group (surface 5) a global coordinate surface:

1. Before you begin implementing the tilt or decenter, change surface 5 to a global coordinate surface by performing the steps:
   • In the "SPECIAL" column, choose "Coordinates(C)" from the pop-up list
   • Choose "Coordinates:" = "Global" from the resulting dialog window.
   • Accept the "global reference surface" as "1" in the pop-up window.
   • Accept the changes to the Coordinate Data window by closing it by clicking on the Green Check in the upper left corner of the window.
2. Now you can go to the first surface of your intended group and tilt and decenter it as you wish and only the surfaces in the intended group will be affected.

The second approach involves performing a coordinate return on the last surface of the component group (surface 4):

1. Perform the following steps on surface 4:
   • In the "SPECIAL" column, choose "Coordinates(C)" from the pop-up list
   • Choose "Coordinate return:" = "Yes" and
   • Choose "return to surface:" = "3" in the resulting dialog window.
   • Make sure you don't change any of the other default values in this window
   • Accept the changes to the Coordinate Data window by closing it by clicking on the Green Check in the upper left corner of the window.
2. Now go back to surface 3 (the surface we are referring to) and in the "SPECIAL" column, choose "Coordinates(C)" from the pop-up list, then
   • Choose "Use base coordinate system for r to this surface:" = "Yes"
   • Make other changes to this dialog window as you see fit to accomplish the tilts and decenters that you want to achieve on the component.
   • Accept the changes to the Coordinate Data window by closing it by clicking on the Green Check in the upper left corner of the window.

Note:
Depending on how your Ray Aiming Mode is set, the incoming rays may be aimed at the vertex of the Aperture Stop surface. In this case (and if the Aperture Stop surface is displaced), the appearance of a lens layout may be unexpected: the Aperture Stop surface may actually look centered while all the other surfaces may appear displaced."