| 摘要 |
PURPOSE:To enable measurement of an electrostatic image quantitatively and in real time, by detecting an electric field based on a charge of the electrostatic image with a light modulation cell as intensity of light. CONSTITUTION:An opposed electrode 5 is provided above an object 1 to be measured and a light modulation cell 6 is arranged between the object and the electrode. Light from a light source 7 is divided with an optical fiber 8a and a beam splitter 23 and a part thereof is reflected with a reflection member 24 through an optical fiber 8b and the cell 6. The reflected light is divided with the splitter 23 again through the cell 6 and the optical fiber 8b and a part thereof enters a photodetector 9. Then, the intensity of light passing through the cell 6 varies with an electric field formed by an electrostatic image 4 by the electrode 5. The amount of the charge is converted into an optical signal. As this variation thereof corresponds to the amount of charge, light from the cell 6 is extracted from the photodetector 9, thereby enabling quantitative measurement of a charge of the electrostatic image. |
