繁體 简体

Q&A: Changing units for tilt tolerances

Question
“I am trying to figure out why ” ttun set deg” and “ttun set min” seem to have no effect. In my lens file, I clicked ” Lens >> Show Tolerance Data >> Surface”, and OSLO rd ” Tilt tolerances are specified in degrees” in the text window. Then I typed “ttun set sec” and clicked “Lens >> Show Tolerance Data >> Surface” again, and OSLO rd ” Tilt tolerances are specified in seconds of arc” in the text window. The first listing claims that “Tilt tolerances are specified in degrees.” The second listing claims that “Tilt tolerances are specified in seconds of arc.” In both cases, though, the values in the rightmost column are unchanged. There is a huge difference between degrees and seconds of arc! Is either display correct?”

Synopsis
Changing units for tilt tolerances

Symptoms
Solution
“Yes, when you type “ttun set deg” and “ttun set min”, you are changing tilt tolerance units and reporting the new values. But note the following excerpt from the OSLO on-line help:

“Tilt tolerance units (ttun)
By default, tilt tolerances are specified in degrees (as are all coordinate tilt angles in OSLO). You can, however, change the units used for all surface, component, and group tilt tolerances. The available units are degrees, radians, minutes of arc, and seconds of arc.
Changing the units does not cause any scaling of previously entered tolerance values. For example, if the tilt tolerance units are degrees and a surface has a tilt tolerance specified as “0.1”, changing the tilt tolerance units to radians means that the surface now has a tilt tolerance of 0.1 radians. The integer read-only global variable ttun indicates the current specification of the tilt tolerance units. The values are ttun – Tilt Tolerance Units
0 – degrees
1 – radians
2 – minutes of arc
3 – seconds of arc “”

Especially note the excerpt in bold. To really see a difference between the “degrees” and ” arc-minutes” tolerance units, you actually should do some analyses. Try typing
tt all
on the command line. You will definitely see a difference between the “degrees” and ” arc-minutes” tolerance units.”

30051 新竹市經國路二段160號9F-8
Tel : 03-5359299  Fax: 03-5358908
統編: 28521213

光學軟體設計領導者

© 2018 All rights reserved. Setup by Eidea