After capturing the image, the vision sensor compares it with a reference image stored in memory to make an analysis. For example, if the vision sensor is set to identify machine parts correctly inserted with eight bolts, then the sensor knows to reject parts with only seven bolts or parts where the bolts are misaligned. Moreover, regardless of where the machine part is located in the field of view or whether the part has rotated within a 360-degree range, the vision sensor can still make a judgment.