'this' And SetInterval

If I have some code that's a bit like this

Con = function() {
this.op = 1;
this.count = 0;
}
Con.prototype.loop = function() {
this.doNext = setInterval(this.next, 100);
}
Con.prototype.next = function() {
this.count++;
if (this.count > 10) clearInterval(this.doNext);
}

obj = new Con();

when I call obj.loop(); 'this' in obj.next refers to setInterval
and not obj . I realise I can add var ref = this; and send it with
setInterval but is there something I can do to get 'this' to refer to
obj when in obj.next?