Who invented a laser pen?

Question: Who invented a laser pen?
- Keywords:
  invention,
  pen
Asked by lottieelizabethmk to Mike, Pip, Tianfu, Tim, Tom on 28 Jun 2012.
- Tom Lister answered on 28 Jun 2012:
  
  Google tells me: ‘Robert Hall patented the miniaturized semiconductor laser that is the basis of modern light pens’
- Tim Stephens answered on 28 Jun 2012:
  
  Yay for google.

Question: Who invented a laser pen?