this example uses one javascript. Its easier to just link to the image though, as you see n the href.
<html>
<head>
<title>pop-up</title>
<script language ="javascript">
function pop_up(){
win = window.open("http://www.volcanic-design.com/volc_photo.jpg", "", "height=345,width=300", hotkeys="no", toolbar="no", copyhistory="no", resizeable="no");
}
</script>
</head>
<h3>pop-up</h3>
<body>
<form name="form1" action="" method="">
<input type="button" name="button2" value="pop-up" onclick="pop_up()">
</form>
<a href="http://www.volcanic-design.com/volc_photo.jpg" target="_blank">Full size pic</a>
</body>
</html>