Disclosed in a movement direction determination system comprising a first detection region, a second detection region and a processing circuit. The first detection region and the second detection region respectively comprises an optical sensor. The processing circuit determines a movement direction of an object according to the optical data generated by the first detection region and the second detection region. The present invention also discloses a movement direction determination system using a single detection region. The present invention also discloses an object volume computation system which can compute an object volume according to sensed optical data. The disclosed movement direction determination system can be used for various applications and the object volume computation system can assist product confirmation.