问如何使灯箱在打开时具有滚动到顶部的效果？

EN

$(function () {
    function launch() {
        $('#sign_up').lightbox_me({
            centered: true,
            onLoad: function () {
                $('#sign_up').find('input:first').focus()
            }
        });
    }

    $('#try-1').click(function (e) {
        $("#sign_up").lightbox_me({
            centered: true,
            preventScroll: true,
            onLoad: function () {
                $("#sign_up").find("input:first").focus();
            }
        });

        e.preventDefault();
    });


    $('table tr:nth-child(even)').addClass('stripe');
});


<div style="width:965px; height:1400px; background:#fff">
    <p>Scroll down the page to find the  lightbox link</p>
</div>
<a class="try sprited" id="try-1" href="#">Click to open lightbox</a>
<div style="display:none; height:350px; width:400px; background:#ccc;" id="sign_up">
    <h3 id="see_id" class="sprited" >Can I see some ID?</h3>
    <span>Please sign in using the form below</span>
    <div id="sign_up_form">
        <label><strong>Username:</strong> <input class="sprited"/></label>
        <label><strong>Password:</strong> <input class="sprited"/></label>
        <div id="actions">
            <a class="close form_button sprited" id="cancel" href="#">Cancel</a>
            <a class="form_button sprited" id="log_in" href="#">Sign in</a>
        </div>
    </div>
    <h3 id="left_out" class="sprited">Feeling left out?</h3>
    <span>Don't be sad, just <a href="#">click here</a> to sign up!</span>
    <a id="close_x" class="close sprited" href="#">close</a>
</div>