var imgWin=null;
        var uniqueWin=true;
        
        function open_img(urlImg, titlePopup, width, height) {
            var props = 'scrollBars=no,resizable=no,toolbar=no,menubar=no,location=no,directories=no,';
            props += 'width='+width+',';
            props += 'height='+height;
            //alert(props);

            if (uniqueWin) {//una sola finestra 

                if (imgWin != null) {
                    imgWin.close();
                    imgWin = null;
                }
            }

            imgWin = window.open(urlImg, '', props);
            imgWin.focus();
        }