Summary

I needed to be able to view the two nozzles on a dual-head 3D printer in order to measure the offset between the two. Readily available borescope cameras have a close focus and adequate resolution to allow good accuracy. With the dental mirror omitted, it was possible to view and record the operation of the head swap mechanism. The use of this camera can be seen in this video. https://www.youtube.com/watch?v=waXIr_ytukw

The first iteration suffered from delamination where the body was clamped to the build stage (bed). A new body was designed so that the weak point was eliminated. The new lower part is held to the main body with two "Plastek" screws.

This design is not presented with the expectation that it will be directly useful to anybody as the dimensions are specific to my printer. If it is close enough to modify for your requirement I have uploaded a STEP file of the parts so that it can be modified to suit.