Patent ID: 8170827

Claim:
A drop mass deviation measuring apparatus comprising: a drop moving force providing part to provide moving forces to each of a plurality of drops discharged from a plurality of drop discharge units, wherein the moving forces have moving directions different from discharge directions of each of the plurality of drops; a discharged drop position detection member to acquire drop position images individually reflecting a position of each of the plurality of drops; and a drop mass deviation measurement control part to calculate a drop discharge direction separation angle of each of the plurality of drops using the drop position images acquired by the discharged drop position detection member to measure mass deviations of each of the plurality of drops, wherein the drop mass deviation measurement control part subtracts a mean of the discharge direction separation angles of each of the plurality of drops from the discharge direction separation angles of each of the plurality of drops to acquire the discharge direction separation angle deviations of each of the plurality of drops and multiplies the discharge direction separation angle deviations of each of the plurality of drops by a predetermined negative number to acquire the mass deviations of each of the plurality of drops.