Image signal resolution changing system

An image signal resolution changing system, comprising:

• a two-level shift register that receives an integer number n of bits into a first register in parallel and shifts said n bits from the first register of said two-level shift register to a second register of said two-level shift register;
• and
• a digital adding unit that adds the bits in said first register with the bits in said second register to output a signal, a highest n bits of said signal being an output image signal.

An image reading device comprising:

• a plurality of photoelectric sensor means for converting light into output image signals having values based on an amount of light received by said photoelectric sensor means, said photoelectric sensor means arranged in at least one row, said plurality of photoelectric sensor means defining a scanner extending in a primary scanning direction parallel to said at least one row, relative movement between said scanner and an original document extending in a secondary scanning direction, said secondary scanning direction being substantially perpendicular to said primary scanning direction;
• and
• resolution changing means for changing a resolution of the image signals output by said scanner and comprising control means for controlling a duration of an integral time of said plurality of photoelectric sensor means during which said photoelectric sensor means collects light from said original document for a single scanline, in order to vary said resolution along said secondary scanning direction.

A method of changing a resolution of an image signal, said image signal having been output by a photoelectric sensor device having a plurality of photoelectric sensor elements that convert light from an original document, said image signal having a value based on an amount of light received by said photoelectric sensor elements, said photoelectric sensor device extending in a primary scanning direction and a secondary scanning direction, said secondary scanning direction being substantially perpendicular to said primary scanning direction, said method comprising:

• changing the resolution of the image signals output by said photoelectric sensor device by controlling a duration of an integral time of said plurality of photoelectric sensor elements during which said photoelectric sensor elements collect light from the original document for a single scanline, in order to vary said resolution along said secondary scanning direction.