Back reflections

Examples of back reflections from aligning optics.

Contents

Tube lens 20cm away

Back reflections from a Nikon 200mm tube lens (Thorlabs ITL200) viewed at 20cm. The result is similar in both directions (front vs back) and similar to the back reflection from an objective but with fewer rings (since it has less internal elements). It is well aligned:

tube_lens_20cm_away_aligned.jpg
Back reflections from a Nikon 200mm tube lens (ITL200) with a viewing screen ~20cm (aligned).