VIDEO : Mel Gibson, Oksana Grigorieva in New Court Battle Over Lucia

Mel Gibson and baby mama Oksana Grigorieva are about to square off in court this morning ... and it's all about their 5-year-old daughter Lucia . TMZ has learned, Mel is about to go to Australia to do a movie and wants to take his daughter with him for the summer. We're told Oksana objects, so they'll be making their respective cases before the family law judge.