title: Prefocused objective-pinhole unit for beam expanding and spatial filtering.
abstract: A beam-expanding and spatial-filtering device, the prefocused objective-pinhole unit (POP unit), is presented. The design is primarily aimed at greater simplicity in handling and construction than the commercially available lens-pinhole spatial filters (LPSF), for once the pinhole is fixed in the correct position with respect to the objective, the alignment of the whole unit can be made an easy matter.
authors.forename: G P
authors.initials: GP
authors.lastname: Antes