JSP :: Making A Request To A Servlet More Than Once

I have a jsp with an img tag whose src is set to request a servlet to display a chart. This is called from another jsp form where user can select various filters. The first time the request is made all works great. but if the user changes the filter settings and and makes the servlet request a second time the chart stays the same. I have verified the new filter values are being set but the servlet is only being called on the initial request.at the head or called servlet I have(I also call a jquery empty on the div that holds the chart between requests. at the moment it just displays the former chart). It is like it is using cache:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setHeader( "Pragma", "no-cache" );
response.setHeader( "Cache-Control", "no-cache" );
response.setDateHeader( "Expires", 0 );