Patent ID: 7512452

Claim:
A mechanism for determining a position of a point relative to a coordinate system having one or more coordinate axis, comprising: a coordinate reference plane, a coordinate read plane generally parallel to and adjacent to the coordinate reference plane; a coordinate system defined by one or more coordinate scales for determining a relative position of a point on the coordinate read plane with respect to the coordinate system, each coordinate scale being aligned along a coordinate axis, and a read mechanism corresponding to and associated with each coordinate scale, wherein each read mechanism is coupled to the coordinate reference plane and to the coordinate read plane such that the read mechanism is responsive to motion of the coordinate read plane along a corresponding coordinate axis to indicate a position of the point on the coordinate read plane along the corresponding coordinate scale, allows transverse motion of the coordinate read plane with respect to the corresponding coordinate axis and includes a guide mechanism for retaining the read mechanism within a predetermined region along an axis transverse to the corresponding coordinate axis with motion of the coordinate read plane transverse to the axis of the coordinate scale wherein a coordinate scale of the coordinate system is fixed to the coordinate reference plane and has a coordinate axis extending generally along an axis of movement of the coordinate read plane, and each read mechanism is mechanically associated with the coordinate read plane and includes a coordinate read head movable along the coordinate scale with movement of the coordinate read plane with the read head reading a coordinate position from the coordinate scale, and a head track extending generally orthogonally to the axis of the coordinate scale with the read head being mechanically engaged with and moveable along the head track in a direction orthogonal to the axis of the coordinate scale, and the guide mechanism is mechanically and movably engaged with the read head and the coordinate scale to move the read head along the head track so that the read head is maintained in a predetermined region adjacent to the axis of the coordinate scale with motion of the coordinate read plane transverse to the axis of the coordinate scale.