Optical Drop Servo Scheme
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-10
In a continuous stream ink jet printer some form of ink stream servo is required to compensate for the day to day (sometimes hour to hour) environmental changes. The servo chosen should include a sensor which is capable of detecting when the ink pump is at the correct pressure. The optical sensor which normally outputs a string of Pulses as drops past the sensor is described in the servo system of U.S. Patent 4,217,594. In this patent, a perturbation is imposed on the stream which creates a gap therein which may be detected at the detector. Inasmuch as the distance from the nozzle to the sensor is a constant, and since the time from perturbation to detection can be easily measured, the drop velocity may be determined. and the pump pressure adjusted to correct for incorrect. drop velocity.