Image reading device for removing the background of a scanned original document

An image forming apparatus, comprising:

• an original document table on which an original document is placed;
• a line scanner for scanning, in a main scanning direction and a sub scanning direction different from the main scanning direction, said original document placed on said original document table, thereby to read out one line at a time in the main scanning direction image data corresponding to said original document;
• memory means for storing said image data scanned by said line scanner each time said line scanner performs a reading operation for one line;
• reading means for reading out said image data from said memory means in units of one line while a sequential line is being scanned by said line scanner;
• detecting means for detecting said image data which is read out by said reading means and which image data has a density lower than a predetermined destiny;
• first outputting means for outputting white image data from the time said reading means reads the first of said image data stored in said memory means until said detecting means detects the first image data which has a density lower than the predetermined density while image data corresponding to a subsequent line is scanned by said line scanner;
• and
• second outputting means for outputting white image data from the time said detecting means detects the last of the image data having a density lower than the predetermined density until said image data corresponding to the last image of one line is read out by said reading means while image data corresponding to a subsequent line is scanned by said line scanner.

An image forming apparatus, comprising:

• an original document table on which an original document is placed, the original document covering an area on the original document table corresponding to an original document area;
• means for scanning the original document table from a first edge to a second edge in a main scanning direction to produce image signals representative of a shade of darkness of a scanned area, the scanned area scanned by the scanning means including the original document area and areas outside of the original document area, the image signals having a plurality of levels, the scanning means moving in a sub-scanning direction different from the main scanning direction while scanning;
• means for comparing the image signals corresponding to the scanned area from the first edge to the second edge with a reference level signal;
• means for detecting the image signals corresponding to the areas outside of the original document area on the basis of the comparison performed by the comparing means;
• means for converting the image signals detected by the detecting means to predetermined image signals;
• means for controlling the comparing means, the detecting means, and the converting means so as to repeat each operation when the scanning means moves in the sub-scanning direction;
• and
• means for forming an image on the basis of the image signals except for the predetermined image signals.

An image forming apparatus comprising:

• an original document table on which an original document is placed, the original document covering an area on the original document table corresponding to an original document area;
• means for scanning the original document table from a first edge to a second edge in a main scanning direction to produce image signals representative of a shade of darkness of a scanned area, the scanned area scanned by the scanning means including the original document area and areas outside of the original document area, the original document having a front and a bottom edge defining interfaces between the original document area and the areas outside of the original document area, the image signals having a plurality of levels, the scanning means moving in a sub-scanning direction different from the main scanning direction while scanning;
• means for converting the image signals to digital image signals;
• means for storing the digital image signals;
• means for comparing the digital image signals corresponding to the scanned area from the first edge to the second edge with a reference level signal;
• front edge detecting means for detecting the image signal corresponding to the front edge of the document area on the basis of comparing of the comparing means to generate a front edge signal;
• means for converting the digital image signals which correspond to the area outside of the original document area to white image signals and allowing the digital image signals to pass therethrough in response to the front edge signal;
• bottom edge detecting means for detecting the image signal corresponding to the bottom edge of the document area on the basis of the comparing means to generate a bottom edge signal;
• means for judging the original document area from the front and bottom edge signals;
• means for converting the digital image signals which correspond to the area outside of the original document area and supplied from the storing means to white image signals and allowing the digital image signals to pass therethrough on the basis of the judging result from said judging means;
• means for controlling the comparing means, the detecting means, and the converting means so as to repeat each operation when the scanning means moves in the sub-scanning direction;
• and
• means for forming an image on the basis of the digital image signals except for the white image signals.

An image forming apparatus comprising:

• an original document table on which an original document is placed, the original document covering an area on the original document table corresponding to an original document area;
• means for scanning the original document table from a first edge to a second edge in a main scanning direction to produce a line image signal representative of a shade of darkness of a scanned area, the scanned area scanned by the scanning means having an original document area and areas outside of the original document area, the original document having a front and a bottom edge defining interfaces between the original document area and the areas outside of the original document area, the line image signal having a plurality of levels, the scanning means moving in a sub-scanning direction different from the main scanning direction while scanning, wherein the scanning means successively generates a plurality of the line image signals;
• means for converting each of the line image signals to respective digital line image signals which include pixel signals;
• comparing means for comparing each of the digital line image signals corresponding to the scanned area with a reference level signal to detect the front edge of the document area and to generate a front edge signal as a result thereof;
• first converting means, to which each of the digital line image signals are input in an order from a leading edge pixel signal to a tailing edge pixel signal, for converting the pixel signals of the digital line image signals corresponding to the areas outside of the original document area to white pixel signals, and allowing the pixel signals of the digital line image signals to pass therethrough in response to the front edge signal;
• storing means for storing the converted digital line image signals from the first converting means;
• bottom edge detecting means for detecting the line image signal corresponding to the bottom edge of the document area on the basis of the front edge signal output from the comparing means to generate a bottom edge signal as a result thereof;
• second converting means, to which the digital line image signals are input in a order from the tailing edge pixel signal to the leading edge pixel signal, for converting the pixel signals of the digital image signal corresponding to the area outside of the original document area to white pixel signals and allowing the pixel signals of the digital line image signals to pass therethrough in response to the bottom edge signal;
• means for controlling the comparing means, the detecting means, and the converting means so as to repeat each operation when the scanning means moves in the sub-scanning direction;
• and
• means for forming an image on the basis of the image signals except for the white pixel signals.

A method of forming an image, comprising steps of:

• placing an original document on an original document table, the original document covering on area on the original document table corresponding to an original document area;
• scanning the original document table from a first edge to a second edge in a main scanning direction to produce image signal representative of a shade of darkness of a scanned area, the scanned area including the original document area and areas outside of the original document area, the image signals having a plurality of levels, the scanning area being moved in a sub-scanning direction different from the main scanning direction while scanning;
• comparing the image signals corresponding to the scanned area from the first edge to the second edge with a reference level signal;
• detecting the image signals corresponding to the areas outside of the original document area on the basis of comparing results in the comparing step;
• converting the image signals detected by the detecting step to reference image signals;
• controlling the comparing step, the detecting step, and the converting step so as to repeat each operation with the scanning area being moved in the sub-scanning direction;
• and
• forming an image on the basis of the image signals except for the reference image signals.