Embodiments of mechanisms for measuring the distance between a robot blade and at least one measurement target are provided. A method for measuring the distance includes emitting a signal to the measurement target by a signal source assembly. The method also includes receiving the signal reflected from the measurement target by a signal reception assembly. The method further includes determining the distance between the robot blade and the measurement target. The distance is determined based on the time difference between the emission of the signal from the signal source assembly and the receipt of the signal by the signal reception assembly.