Abstract: An electrostatic type voltmeter for measuring the potential on a surface, the voltmeter including a probe; a support for supporting the probe in spaced relationship with the surface, the probe having a plurality of spacing element sites thereon for measuring a distance between each of the plurality of spacing element sites and a corresponding area on the surface opposite of each of the plurality of spacing element sites; a plurality of electrostatic element sites, intermixed and adjacent to the plurality of spacing element sites on the probe, for measuring a voltage between each of the plurality of spacing element sites and an area on the surface adjacent to the corresponding area opposite of each of the plurality of spacing element sites. A processor for compensating an output signal of the probe in response to the measurements received from the plurality of spacing element sites and the plurality of electrostatic element sites.

Abstract: An improved modulator assembly of an electrostatic voltmeter for an electrophotographic process. A modulator base of the modulator assembly is provided having accurate configuration and built in design features which simplify manufacture and assembly of the modulator assembly and electrostatic voltmeter. The modulator base includes reference mounting surfaces which provide accurate orientation and alignment of the modulator assembly during assembly, air purge grooves which provide enhanced air purging of contaminants from the modulator assembly, and shielding areas which maximize the signal to noise. The modulator base provides simplified construction of a modulator assembly for an electrostatic voltmeter having enhanced performance and robust functionality.

Abstract: A system for enhancing air purging of a modulator assembly of an electrostatic voltmeter for an electrophotographic process. A vane connected to a chopper element is located at one end of a vibratory beam so as to move when the vibratory beam oscillates. Movement of the vane generates air turbulence and currents in the vicinity of the modulator and sensor electrode thereby improving purging of toner particles and other contaminants and preventing such contaminants, which tend to cause drift errors, from settling in the vicinity of the modulator and sensor electrode.

Abstract: An electrostatic voltmeter (ESV) and a method thereof provides an electrical signal proportional to an electrostatic potential. The ESV includes a high voltage input section that receives a high voltage signal representative of an electrostatic potential. The high voltage signal input section then generates a current signal representative of the electrostatic potential. The current signal is applied to a control and sensing circuit. A high voltage current source is connected between the high voltage input section and a high voltage potential. The high voltage current source acts as an active load for the control and sensing circuit. A voltage level determining section is connected to a node between the high voltage input section and the high voltage current source for providing an electrical signal proportional to the electrostatic potential. The EVS disclosed herein is particularly useful in measuring electrostatic potential of a photoreceptor to control imaging in an electrophotographic imaging system.

Abstract: Method and apparatus for modulating the vibrations of an object with a constant amplitude has a sensor, e.g., a piezoelectric transducer, for sensing the vibrations. A light source, e.g., an LED, receives the sensed signal and illuminates a light dependent resistor (LRD). In turn, a control circuit controls the vibration amplitude in accordance with the LDR resistance. A full wave bridge rectifier can be used between the sensor and the LED.

Abstract: A flash exposure photocopier provides a mechanism for automatically controlling photoreceptor exposure levels to compensate for the effects of documents having backgrounds of different densities. A photosensor and lens assembly is located within a flash housing in a position whereby a large portion of the document is imaged by the lens onto the surface of a chip having a plurality of individual photosensors contained thereon. The outputs of each photosensor are integrated and applied to a comparator set at a particular reference level. The comparator output controls the duration of the flash source so as to quench lamp operation when an input level is reached corresponding to the particular reference level set. The integrated photosensor outputs are also summed and a signal representing their average value is compared to the signal which triggers the comparator. The ratio of these signals is used to identify documents with high area coverage and hence high toner usage.