Patent ID: 8430059

Claim:
An apparatus for precision pen height control, the apparatus comprising: a dispensing member, a portion of the dispensing member defining an opening; a fluid dispensing system, the fluid dispensing system being in fluid communication with the opening by a tubular member; a vertical position sensing system fixedly engaged to the tubular member, the vertical position sensing system comprising a diffraction grating and a sensor, the sensor being positioned adjacent the diffraction grating, the sensor being constructed and arranged to sense the diffraction grating, a vertical support being engaged to the tubular member, the sensor being further constructed and arranged to produce a vertical position signal based upon the position of the vertical support; and a vertical position controller fixedly engaged to the tubular member by the vertical support of the vertical position sensing system, the vertical position controller being enraged to the vertical position sensing system, the vertical position controller constructed and arranged to receive a control signal generated at least partially from the vertical position signal, the vertical position controller further constructed and arranged to produce and apply vertical forces to the vertical support in response to the control signal.