Patent ID: 7457686

Claim:
A method for aligning the position of a movable arm comprising: providing an alignment element on the apparatus projecting a distance above the apparatus in the z-direction and having a surface lying in a plane formed by an x and y axis; providing a movable arm having a tool at the free end; positioning the object such that the surface of the element faces the tool; moving the tool in a direction towards the surface of the element; sensing when the tool reaches a predetermined point on or above the surface of the element, whereby the position of the tool in the z-direction is determined based on the relationship between the measured response of the tool and the height of the tool above the surface of the alignment element; placing the tool on or at a distance in the z-direction from the surface; moving the tool in the x-direction while sensing the surface of the element; moving the tool in the x-direction until an edge of the element is sensed; determining the center in the x-direction based on the known distance the tool has moved and the known dimensions of the element in the x-direction; placing the tool on or at a distance in the z-direction from the surface; moving the tool in the y-direction while sensing the surface of the element; moving the tool in the y-direction until an edge of the element is sensed; and determining the center in the y-direction based on the known distance the tool has moved and the known dimensions of the element in the y-direction.