Exactly this, in university one of my professors in first term rather than using slides, printed his slides onto paper and put them under one of these cameras,

Exactly this, in university one of my professors in first term rather than using slides, printed his slides onto paper and put them under one of these cameras, visualisers as they're called. I found it much more engaging since he could easily annotate things and just get a blank sheet of paper if anything needed further explanation.