An Air Carrier Captain cleared to cross SFO Runway 1R on Taxiway G turned onto a 45 high speed and entered the runway instead of proceeding straight ahead to Taxiway L.

Narrative

Taxied via A; G; L; and F for Runway 28L departure. I taxied A to G crossing 1L. As I approached 1R I noticed the lighted 'G' sign with an arrow that seemed to point at a 45 degree angle. I confused the sign to mean taxi at a 45 angle down 1R to pick up the taxiway on the other side. Not long after making the left as we realized our error; the Ground Controller contacted us and informed us of our error. New instructions were to taxi down 1R and join 'F'. The combination of being late and not as alert caused me to assume that I had done this type of taxi before. After looking at the airport page; I realized that I had confused it with Taxiway H. The combination of being late and a not as alert as I could have been along with not referencing my airport diagram contributed to this error. Neither runway was being used and we had clearance to enter/cross the runway; but not to taxi down the runway. I could have done a 180 on the runway; but the Controller gave us new taxi instructions. Taxi lights that continue across the runway would be nice. For some reason the taxiway didn't appear to cross at a 90 degree angle; adding a little more confusion to the situation.