how to make a raycast have a wider range of hit

i dont know if this makes sense or not but its like this, when you create a raycast it hits the object that's in front of it. is it possible to make the raycast hit any object on the screen no matter where it is on the screen. ![alt text][1] [1]: http://answers.unity3d.com/storage/temp/1105-new+raycast.png