Positioning skew compensation for imaging system using photoconductive material

A method for constructing an accurate digital representation of a latent image formed on a photoconductive structure of the type having a plurality of elongate readout electrodes, where the photoconductive structure may be skewed from a predetermined position with respect to the system, comprising the steps of:

• collecting data by scanning the photoconductive structure in a pattern of scan spots and receiving data from the readout electrodes;
• measuring skew in the positioning of the photoconductive structure with respect to the scan pattern;
• and
• assembling a digital representation of the image, by
• determining from said skew measurement which electrode and which adjacent electrode correspond to said scan spots, and
• combining the data collected from the electrodes in accordance with said determination, to thereby assemble a digital representation of the latent image.

A reader for readout and construction of an accurate digital representation of a latent image formed on a photoconductive structure of the type having a plurality of elongate electrodes, comprising:

• a scanner for scanning a photoconductive structure positioned with respect thereto in a pattern of scan spots thereacross;
• holder apparatus for holding a photoconductive structure and translating it through the scan pattern during a scanning operation;
• charge signal receivers operatively connected to said electrodes for receiving charge signals therefrom caused by said scanning operation;
• a memory connected for storing said charge signals received by said electrodes;
• a skew measurement system for measuring skew in the positioning of the photoconductive structure in said holder apparatus with respect to the scan pattern produced by said scanner;
• means for calculating from said skew measurement which electrodes and which adjacent electrodes are closest to individual scan spots of said pattern;
• and
• means for combining selected ones of the stored charge signals received by said electrodes in accordance with said electrode calculation, so as to assemble an accurate digital representation of the latent image.

A system for compensating for positioning skew errors in the scanning of images formed on photoconductive structures, comprising:

• a photoconductive structure capable of holding a charge distribution of a latent image to be scanned and read out, said photoconductive structure having a plurality of electrodes for collecting charge movements caused by the scanning;
• a scanner for applying readout radiation in patterns of scan spots to the photoconductive structure to cause the charge movements which are collected by the electrodes;
• a support for receiving the photoconductive structure and holding the photoconductive structure in relation to the scanner;
• a skew measurement system for measuring errors in positioning of the electrodes with respect to the patterns of scan spots;
• and
• a skew compensation system responsive to said skew measurement system and operative to provide an indication of which electrode and which adjacent electrodes correspond with the scan spots, so that the charge movements collected by the electrodes can be combined to form the correct charge value for the image area represented by the spot.

A system for compensating for positioning skew in the scanning of a digital representation of an image formed on a photoconductive structure, comprising:

• a photoconductive structure, capable of holding an imagewise charge distribution of a latent image to be scanned and converted to a digital image representation;
• said photoconductive structure having a plurality of electrodes for collecting charge movements caused by the scanning;
• said photoconductive structure having a reference mark indicating a start of the scanning;
• a scanner for scanning across the photoconductive structure in scan patterns of successive pulsed spots of radiation, the pulsed spots of radiation corresponding to pixels of the latent image;
• a support for receiving the photoconductive structure and holding the photoconductive structure in relation to the scan patterns of the scanner;
• circuitry coupled to said electrodes for receiving and storing signals representing the charge collected by the electrodes due to the pulsed spots of the scanning, said circuitry including multiple amplifier channels synchronized with the scanner so that the amplifier channels associated with a respective one of the electrodes under an expected position of one of the pulsed spots and at least one of the electrodes adjacent to the respective one of the electrodes are operative for receiving charge movements caused by a scan spot;
• a skew measurement system for measuring the distance between the start of one of the scan patterns of successive pulsed spots and said reference mark for a plurality of said scan patterns along the photoconductive structure as a measure of errors in the positioning of the photoconductive structure in said support and displacement of the scan patterns of pulsed spots from expected positions with respect to said electrodes;
• and
• a skew compensation system responsive to said skew measurement system and operative to provide an indication of which electrode and which adjacent electrodes correspond with individual scan spots, so that the charge movements received thereby can be combined to form the correct charge value for the image pixel represented by the spot.

A method for compensating for skew or offset positioning errors in the scanning and digital readout of charge distribution images from photoconductive structures of the type having a plurality of elongate strip readout electrodes, comprising the steps of:

• positioning the photoconductive structure in a holder within an area for scanning by a scanning assembly;
• scanning across the photoconductive structure with patterns of radiation spots corresponding to pixels to be read out;
• for each scan pattern, receiving and storing charge signals caused by each spot, from the readout electrode expected to be positioned under the spot and at least one adjacent readout electrode;
• measuring the distance from a reference start-of-scan position to a position where the scan reaches a reference having a known relation to the positions of the electrodes on the photoconductive structure, for a plurality of scan patterns along the photoconductive structure;
• determining from the measured distance the amount of skew error from the expected positioning of the photoconductive structure with respect to the scanned pattern of radiation spots, and
• determining from said skew error, which readout electrodes were closest to each scan spot, so that their corresponding received charge signals can be combined to obtain the correct charge value for the pixel represented by the spot.