POTENTIAL MEASUREMENT APPARATUS AND IMAGE FORMING APPARATUS

• US 20100019779A1
• Filed: 01/28/2008
• Published: 01/28/2010
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ushijima, Takashi, Kato, Kazuhiko, Ogawa, Toshiyuki, Kandori, Atsushi, Hirose, Futoshi, Zaitsu, Yoshitaka, Noguchi, Kaoru
• Granted Patent: US 7,990,159 B2
• Time in Patent Office: Days
• US Class Current: 324/660
• CPC Class Codes: G01R 29/12 Measuring electrostatic fields or voltage-potential
• CPC Class Codes: G03G 15/0266 Arrangements for controlling the amount of charge
• CPC Class Codes: G03G 15/5037 the characteristics being an electrical parameter, e.g. voltage

Abstract

A potential measurement apparatus for measuring a surface potential of an object of measurement detects a change in electric charge induced at a detection electrode due to electrostatic induction by changing a distance between the detection electrode and the object of measurement in accordance with a predetermined period, using a neutral distance as reference, as a signal representing a change in electric current. The potential measurement apparatus includes a first detection unit for detecting a signal representing a fundamental period of the change in electric current and a signal representing a second harmonic period, a second detection unit for detecting information representing a capacitance between the detection electrode at the neutral distance and the object of measurement and an arithmetic unit for computationally obtaining information on the surface potential of the object of measurement, with eliminating an influence of the neutral distance and the capacitance, according to an outcome of detection of the first detection unit and an outcome of detection of the second detection unit.

Claims

1. A potential measurement apparatus for measuring a surface potential of an object of measurement, which is capable of detecting a change in electric charge induced at an detection electrode due to electrostatic induction by changing a distance between the detection electrode and the object of measurement in accordance with a predetermined period, using a neutral distance as reference, as a signal representing a change in electric current, comprising:

a first detection unit for detecting a signal representing a fundamental period of the change in electric current and a signal representing a second harmonic period;

a second detection unit for detecting information representing a capacitance between the detection electrode at the neutral distance and the object of measurement; and

an arithmetic unit for making calculations according to a detection outcome of the first detection unit and a detection outcome of the second detection unit,

the arithmetic unit computationally obtaining information on the surface potential of the object of measurement, with suppressing an component attributable to an influence of the neutral distance and the capacitance.

2. The potential measurement apparatus according to claim 1, wherein the second detection unit includes a power source for applying a voltage to the detection electrode, the voltage being different from a voltage applied to the detection electrode at a time of detection by the first detection unit.

3. The potential measurement apparatus according to claim 1, wherein the second detection unit includes an oscillation circuit including a resonance circuit having a capacitance formed between the detection electrode at the neutral distance and the object of measurement, a known inductance and a frequency variable power source.