Abstract: A method of calibrating a scanning carriage drop-on-demand ink jet ejector wherein the ejector is traversed past a droplet detection light beam while droplets are ejected. By knowing the position of the ejector and relating it to the amount of light blocked by droplets, horizontal errors in drop position can be detected. Similarly, by measuring the amount of time elapsing between droplet ejection and droplet detection, the velocity of the droplets can be determined. Corrections can be made by adjusting the time of ejection and/or the drive pulse amplitude and/or width.

Abstract: An optical position encoder system comprising a circuit for removing the electrical bias usually associated with the optical sensor outputs, and for generating a voltage output varying with the encoder position to produce an indication of angular or linear displacement between zero crossings is described. In one portion of the circuit, sensor output signals 180 degrees out of phase are subtracted to automatically cancel the bias. In another portion of the circuit, signals 90 degrees out of phase are used to generate a voltage, the amplitude of which is a function of the grid position between grid zero crossings. To accomplish these results, two or more angularly displaced grids are required.

Abstract: A drive circuit for a drop-on-demand ink jet printer utilizes the inherent capacitance of the driver electromechanical transducer to store at least a portion of the voltage required for droplet ejection. The drive circuit includes circuitry for sensing and terminating, for example, rapid discharge of the electrical potential difference across the electromechanical transducer during jet firing.

Abstract: In moving carriage ink jet printers, the motion of the carriage may be imparted to droplets expressed offsetting the droplets' position on the record surface from one another where bidirectional printing is utilized. To eliminate print distortion resulting therefrom, lines are printed two at a time, each line thus being printed by the carriage moving in only one direction.

Abstract: A scanning carriage ink jet printer is provided wth ink drying apparatus on the carriage. The dryer allows a greater variety of inks and paper to be utilized. Preferably, drying apparatus is provided on both sides of the printer, parallel to the scanning direction of the carriage, to provide for bidirectional printing.