How to make previous selected video (image frames) cleared from my axes?

Hi, my GUI has a button to select a video file, and then convert it into image frames. All the image frames will then be displayed in the axes. My problem is that: the function works well, but when i choose a second video (choose another video), the previous frames remains in the axes. Because i have a back and next button to see the images also, from that i can see previous video frames are still there. How do i solve it? I want all the data for previous selected video are cleared.

Thanks a lot.