Touch position to fit in screen

[Nexgea]

Hi,
I want to paint on touch screen with prefab, where I touch there will be a red sprite (prefab).

Here is my code :

var i : Vector2;
var prefab : Transform;



function FixedUpdate () {

 i = Input.GetTouch(0).position;
var touch : UnityEngine.Touch;


if(Input.touchCount >0)
{
	Instantiate (prefab, i ,transform.rotation);
	Debug.Log(i);
}
}

Here is screenshot when I click on 4 corners

The White thing is ortographic Camera.

[767_2]

function Update ()
{
if (Input.touchCount > 0)
{
var ray =Camera.main.ScreenPointToRay(Input.GetTouch(0).position);
var hit : RaycastHit;
if (Physics.Raycast (ray, hit))
{
Instantiate (prefab, hit.transform ,Quaternion.identity);
}
}
}