Adding Link to Image within Post

I am using the following to produce an image gallery, and would like to link the original file to the caption. The output on the post is generated by timthumb… any help?

if ( !empty($attachments) ) :
	$counter = 0;
	$photo_output = '';
	$thumb_output = '';
	foreach ( $attachments as $att_id => $attachment ) {
		$counter++;

		# Caption
		$caption = "";
		if ($attachment->post_excerpt)
			$caption = '<p class="sliderCaption">'.$attachment->post_excerpt.''.$caption.' </p>';	

		# Large photo
		$src = wp_get_attachment_image_src($att_id, $photo_size, true);

			 $photo_output .= '<div><img style="width:'.$photo_width.'px;display:block;" src="' . esc_url($themeurl) . '/timthumb.php?src='.urlencode($src[0]).'&q=90&w='.$photo_width.'&zc=1" width="'.$photo_width.'" alt="" />'.$caption.'</div>';
		# Thumbnail
		$src = wp_get_attachment_image_src($att_id, $thumb_size, true);

		$thumb_output .= '';
	}
endif; ?>