Wow, amazing persistence. 20 years between first proof of concept to release of a xerox machine as we know today. 10 years later he's dead.
Because of the work he put into supporting his family, Carlson had to take a postgraduate year at his alma mater San Bernardino High School to fill in missed courses.
What a fascinating read.
There is a nice book about Carlson and his invention - 'Copies in Seconds.'