The bat symbol on Batman's chest has changed through out the years and is one of the most recognizable of all. The most memorable one is the yellow oval with the classic spread winged bat which was used in the comic book series along with the 1960’s television series. But the first time we see it on the yellow ellipse was in 1964. And it was explained as being a target re-enforced with armor for gunmen to aim at and not his head in the mid '80s. In addition, it was used in the first two Batman movies.
Now in the third Batman movie, Batman Forever, it brought out a new Batman logo without the original yellow in the oval.
In the fourth movie, Batman and Robin, which introduced Robin, had a mixture logo of Batman and Robin symbol.