Patent ID: 9581930
Date: 2017-02-28
CPC Classifications: G03G

Claim:
1. A print head apparatus for use with a xerographic printing device having a rotating photoreceptor, the photoreceptor having a curved conductive surface, the apparatus comprising: an LED bar print head configured for locating adjacent the curved conductive surface of the photoreceptor; a first distance sensor, the first distance sensor being located on the LED bar print head at a first location, the first distance sensor being configured for measuring a first gap between the LED bar print head and the photoreceptor at the first location; a second distance sensor located on the LED bar print head at a second location, the second location being different from the first location, the second distance sensor being configured for measuring a second gap between the LED bar print head and the photoreceptor at the second location, wherein the LED bar print head is configured such that the first distance sensor and the second distance sensor are arranged on the LED bar print head such that the first distance sensor and second distance sensor are configured to enable a measurement of angular position of the LED print bar head relative to the curved conductive surface of the photoreceptor, the measurement being based on the first gap and the second gap; wherein the first gap is measured by determining a first capacitance using the first distance sensor and the curved conductive surface of the photoreceptor; wherein the second gap is measured by determining a second capacitance using the second distance sensor and the curved conductive surface of the photoreceptor; and a piezo actuating system to produce fine adjustments to the first gap and the second gap by moving the LED bar print head towards or away from the photoreceptor, the piezo actuating system including a piezo driver and at least one piezo stack; wherein the at least one piezo stack enables bidirectional motion of the LED bar print head as the at least one piezo stack expands and contracts under a changing applied actuation signal, the signal being based on a determined position of the LED bar print head, the position of the LED bar print head being determined based on the first capacitance and the second capacitance.