#$%^&*AU2014253457A120141113.pdf#####METHOD AND APPARATUS FOR DETERMINING PARAMETERS OF LINEAR MOTION IN A SURGICAL INSTRUMENT ABSTRACT A surgical instrument (10) comprising a housing (110) an elongated shaft (140) extending distally from the housing (10) and defining a first longitudinal axis (A-A) a firing rod (220) disposed within the elongated shaft (140) a drive mechanism disposed at least partially within the housing (10), the drive mechanism in mechanical cooperation with the firing rod (220) a light emitter that generates and emits light that is directed towards a surface of the firing rod (220) and a detector unit (460) that senses a parameter of light reflected from the surface of the firing rod.
