Patent ID: 7367646

Claim:
A method of determining a velocity of a drop of ink ejected by an ink jet print head having a plurality of nozzles, comprising: providing a card having a first print medium layer having a first height and a first length along a longitudinal axis of said card, and a second print medium layer having a second height and a second length along said longitudinal axis of said card, said first length being different than said second length; printing a line on said card using said ink jet print head along said longitudinal axis during relative movement between said ink jet print head and said card in a print direction generally perpendicular to said longitudinal axis at a print velocity, said line comprising a plurality of dots, each dot being produced by ink ejected from one of said nozzles, a first one of said dots being located on a top surface of said first print medium layer and a second one of said dots being located on a top surface of said second print medium layer, said first one of said dots resulting from said drop of ink; determining a first relative distance between said first one of said dots and said second one of said dots along said print direction; determining a second relative distance between the top surface of said first print medium layer and the top surface of said second print medium layer in a direction generally perpendicular to said print direction; and calculating said velocity of said drop of ink ejected by said ink jet print head based on said print velocity, said first relative distance and said second relative distance.