| Subject | English | German |
| opt. | optical relay system | Lichtübertragungssystem |
| opt. | optical relay system | optisches Bildübertragungssystem (optical system for transferring an image from one point to another for the purpose of magnifying it, changing its orientation or merely moving it to a more convenient location) |
| opt. | relay optical system | optisches Übertragungssystem |