Browse Prior Art Database

Latent Charge Visualization Technique

IP.com Disclosure Number: IPCOM000038524D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Imaino, W: AUTHOR [+2]

Abstract

In the electrophotographic printing process, the print quality depends on the uniformity of the latent image which relies on the charge distribution on the photoconductor drum (PC). Hence, it is essential to sense the PC's electrical defects, which are manifested as missing pixels in copy mode and spots in print mode. Optical detection of photoconductor defects correlates poorly with electrical defects, so direct detection of the latent charge is necessary. Fig. 1 illustrates a PC inspection system using dynamic scattering or pleochroic liquid crystal flat panel. The panel is flood illuminated by a light source emitting at the wavelength where the PC is not sensitive.

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Latent Charge Visualization Technique

In the electrophotographic printing process, the print quality depends on the uniformity of the latent image which relies on the charge distribution on the photoconductor drum (PC). Hence, it is essential to sense the PC's electrical defects, which are manifested as missing pixels in copy mode and spots in print mode. Optical detection of photoconductor defects correlates poorly with electrical defects, so direct detection of the latent charge is necessary. Fig. 1 illustrates a PC inspection system using dynamic scattering or pleochroic liquid crystal flat panel. The panel is flood illuminated by a light source emitting at the wavelength where the PC is not sensitive. Then, the amount of light scattered at a certain pixel location on the display panel depends on the charge density of the PC at the corresponding pixel location. The sensitivity of this device can be controlled by the spacing between the PC and the LC panel which, in turn, control the voltage across the liquid crystal. The image is captured by an imaging sensor, and the inspection can be accomplished by either an operator or image processing scheme. In view of the fact that the PC's sensitivity lies in the visible region (up to 900 nm for organic PC), this technique is only executable in the infrared region. Fortunately, all silicon-based image sensors, such as CCD or vidicon tube, have the sensitivity down to 1.1 micron; consequently, no exotic imaging device i...