get image caption from meta box query

Question

I would like to pull the image caption for each image into a carousel. I can successfully pull the alt tag, but I cannot get the caption.

This is what I have so far, but it is breaking.

    <?php $args = array(
    'post_type' => 'homepageslider',
    'posts_per_page' => 1
    ); 
    $query = new WP_Query($args); 
        while ($query->have_posts()):
        $query->the_post();
        $meta = get_post_meta( get_the_ID(  ), 'homepage_media_gallery', false );

        if ( !is_array( $meta ) )
            $meta = ( array ) $meta;

            if ( !empty( $meta ) ) {
            $meta = implode( ',', $meta );
                $images = $wpdb->get_col( "
                SELECT ID FROM $wpdb->posts
                WHERE post_type = 'attachment'
                AND ID IN ( $meta )
                ORDER BY menu_order ASC
                " );
            foreach ( $images as $att ) {
            // Get image's source based on size, can be 'thumbnail', 'medium', 'large', 'full' or registed post thumbnails sizes
            $attachment_meta = wp_get_attachment($att);
            $link = $attachment_meta['caption'];
            $src = wp_get_attachment_image_src( $att, 'full' );
            $alt = get_post_meta($att, '_wp_attachment_image_alt', true);
            $src = $src[0];
            // show caption                         
            echo $link;
            // Show image
            echo "<div><img src='{$src}' class='project-images' />"; ?>
            <?php if ($alt) : ?>
            <div class='homepage-caption'>
                <?php echo $alt; ?>
            </div>
        <?php endif ?>
     <?php echo "</div>"; 
         }
    } 
endwhile 
?>

How do you get the caption of each image in the query? I am using the WP Meta Boxes plugin to pull the images.

UPDATE

Obmerk had it correct. There was no need for an SQL Query. This is what I have now that pulls alt, caption and description for each image.

<?php 
    $args = array( 'post_type' => 'attachment', 
       'orderby' => 'menu_order', 
        'order' => 'ASC', 
        'post_mime_type' => 'image' ,
         'post_status' => null, 
         'numberposts' => null, 
          'post_parent' => $post->ID,
         'exclude'     => get_post_thumbnail_id()
    );
$attachments = get_posts($args); ?>
 <?php if ($attachments) : ?>
     <?php foreach ( $attachments as $attachment ): ?>
    <?php 
    $alt = get_post_meta($attachment->ID, '_wp_attachment_image_alt', true);
                                $image_title = $attachment->post_title;
                                $caption = $attachment->post_excerpt;
                                $description = $attachment->post_content;
                                $src = wp_get_attachment_image_src( $attachment->ID, 'full' ); 
                                list($width, $height, $type, $attr) = getimagesize($src[0]); ?>

    <div class="projectBlock">
    <div class="projectCopy">

        <h2><?php echo $alt ?></h2>

        <h3><?php echo $caption ?></h3> 
        <p class='projectDescription'><?php echo $description ?></p>
        </div>
    <div class="projectImage">
        <img src="<?php echo $src[0]; ?>" class="project-images 
    </div>
    </div>

Answer 1

I am not sure how you use your metabox (and why??) , nor why would you do a direct SQL query in the code , but normally, this is how you would pull image (attachment) data :

$alt = get_post_meta($attachment->ID, '_wp_attachment_image_alt', true);
$image_title = $attachment->post_title;
$caption = $attachment->post_excerpt;
$description = $image->post_content;

Since atatchments in wp are actually a built in CPT ( actually a post) :

The attachment caption is actually the post excerpt The attachment title is the post title The attachment description is the post content .

so a full code woule be more along the lines of :

$args = array( 'post_type' => 'attachment', 
                    'orderby' => 'menu_order', 
                    'order' => 'ASC', 
                    'post_mime_type' => 'image' ,
                    'post_status' => null, 
                    'numberposts' => null, 
                    'post_parent' => $post->ID );

        $attachments = get_posts($args);
        if ($attachments) {
            foreach ( $attachments as $attachment ) {
                $alt = get_post_meta($attachment->ID, '_wp_attachment_image_alt', true);
                $image_title = $attachment->post_title;
                $caption = $attachment->post_excerpt;
                $description = $attachment->post_content;
                } 
             }