Getting post images and captions only!?

Hi!
I’m trying to get only my post images and their captions to display both on my index and on my single pages. The images are working fine, but no-matter what I try, I’m not getting captions. Please help!!!!

This is what I have that works for the images:

<?php
   $attachments = get_children( array('post_parent' => get_the_ID(), 'post_type' => 'attachment', 'post_mime_type' => 'image','caption' => $attachment->post_excerpt) );
      foreach ( $attachments as $attachment_id => $attachment ) {
         echo wp_get_attachment_image($attachment_id, 'full' );
      }
?>