Heath Ledger has read the TDK script once in Chris Nolan's house, but Nolan wouldn't let him leave with it. That's what Ledger talks about on his interview posted at LatinoReview. Here's the complete story:

What motivated you to take on the role? Were you familiar or a fan with the character?

Ledger: I guess if I was a fan of a comic book character it would be the Joker. The offer motivated me to take it, the opportunity to play this guy. Somewhere inside I kind of knew instantly what to do with it. I didn't feel like I had to search for it, I feel like I have a plan of attack already and that usually dictates whether I want to do something or not, if I have an understanding of it straight away.

Have you met with Chris or Christian or have you just formulated what you want to do independently?

Ledger: At this point it's solo. Chris Nolan's still busy, or he was, with "The Prestige" and they're still writing the script. They're so guarded, even with me. I don't have a script. I've read it once, at Chris Nolan's house, but he wouldn't let me leave with it.

Meanwhile, Ledger also talks about his portrayal of the Joker in Newsrama. He has his own version of the Joker, he still dislikes comic books and its movies and he don't want to copycat how Nicholson did with the Joker. Good move.

He also has done a so called "3d image scanning", as he told the interviewer here:

Have you done screen tests with The Joker makeup yet?

No, but I did do 3-D image scanning. I don’t know what they’re doing with it. This Bat truck turned up at my place in L.A.. It had these gadgets and cameras that zoom around you and up and down you. It instantly projects a three dimensional image of you. I’ve never used anything that high tech before in a film. I felt like I was in the truck from Knight Rider.

Click here for the complete interview.