var imageUrl = document.camimage_big.src;
var random = new Date().getTime();
var delay = 5; // update delay in seconds
var counter = 0;
var buffer = new Image;
var param = ((0 > imageUrl.indexOf('?')) ?  '?' : '&');
function DisplayImage() { 
   document.camimage_big.src = buffer.src; 
   LoadNextImage(); 
}
function LoadBuffer () {
   var trickname = imageUrl;
   ++counter;
   trickname += param + 'counter=' + (random + counter);
   buffer.src = trickname;
   buffer.onload = DisplayImage;
}
function LoadNextImage() {
   setTimeout('LoadBuffer()', 100*delay);
}
LoadNextImage();