Patent ID: 6362847
Filing Date: 2002-03-26
Classification: H04N

Abstract:
A color laser printer including:a plurality of photoconductors; a plurality of scanning means equal in number to the number of said photoconductors; each of said scanning means including a laser beam to scan simultaneously a different one of said photoconductors; electronic control means for electronically changing the length of at least one of a plurality of write lines scanned on each of said photoconductors during printing operation to make the write lines substantially equal when the initial lengths of the write lines produced by each of said scanning means are not substantially equal; each of said photoconductors producing a different selected color selectively along the write line after being scanned by said laser beam of one of said scanning means to produce the different selected color at any PEL along the write line; means for depositing each of color images of said photoconductors on a medium in an overlying relation to form a resulting color line on the medium substantially equal to the length of each of the write lines; said electronic control means including: a clock operating at a fixed frequency to produce equal clock timing pulses of the same frequency for supply to each of said scanning means; separate selective changing means for electronically selectively changing the number of clock timing pulses for selected PELs in at least one of the write lines on at least one of said photoconductors to make the lengths of the write lines on all of said photoconductors substantially equal; and periodically determining means for periodically determining the length of at least one of the write lines on each of said photoconductors; each of said separate selective changing means including means for changing the number of clock timing pulses for the selected PELs for the at least one write line on at least one of said photoconductors to change the length of the write line on said at least one photoconductor to make the lengths of the write lines on all of said photoconductors substantially equal; separate beam sensing means for each of said laser beams and equal in number to the number of said laser beams; each of said separate beam sensing means including: two sensing means spaced a predetermined distance apart to provide a measuring line therebetween; and said two sensing means being passed over by one of said laser beams; said periodically determining means including measuring means for measuring the number of clock timing pulses required for each of said laser beams to move between said two sensing means of one of said separate beam sensing means to obtain the length of the measuring line relative to the lengths of the measuring lines on the other of said photoconductors; and means for utilizing the product of a stored value of the ratio of the length of a write line to the length of the measuring line and the number of clock timing pulses measured by said measuring means to change the length of the write lines on at least one of said photoconductors to make the lengths of the write lines substantially equal on all of said photoconductors.