US 6,362,847 B1 · Electronic control arrangement for a laser printer

Abstract

The write lines of a color laser printer are maintained substantially equal throughout the printer's operation by an electronic control arrangement. At the factory, the write lines on all photoconductors of the color laser printer are calibrated to be substantially equal, and the ratio of each write line to a measuring line for each photoconductor is ascertained. During operation of the printer, the length of each of the measuring lines is periodically determined through counting the number of PELslice clock timing pulses produced from a PELslice clock operating at a fixed frequency determined during factory calibration. The length of the write line is determined by the product of the length of the measuring line and the factory calibrated ratio of the length of the write line to the length of the measuring line. After each periodic determination, PELslice clock timing pulses are selectively inserted into or removed from the PELslice clock timing pulses for all of the write lines but the write line, which is closest to the desired length, to increase or decrease their lengths to be substantially equal to the write line, which is closest to the desired length. The time for insertion or removal of each of the PEL slices into the train of PELslice clock timing pulses produced by the PELslice clock is determined with each preferably inserted at a non-active portion of a PEL. Each insertion or removal of a PEL slice also may be offset from its determined position.

Claims48

Dependent claims

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.

14 more elements

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;
and 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 offset producing means for producing an offset at locations in each of the write lines on each of said photoconductors at which the number of the clock timing pulses for each of the selected PELs is changed.

7 more elements

A method or controlling the length of a write line on each of a plurality of photoconductors produced by a different laser beam simultaneously scanning each of the photoconductors of printheads in a color laser printer during printing operation to maintain substantially equal lengths of the write lines produced on the photoconductors by the laser beams including:

determining the length of the write line on each of the photoconductors by determining the number of PEI-slice clock timing pulses of a PELslice clock comprising the length of each of the write lines on each of the photoconductors;
changing the length of the write line on at least one of the photoconductors so that the lengths of the write lines on all of the photoconductors are substantially equal by changing the number of the PELslice clock timing pulses for the write line on the at least one photoconductor so that the lengths of the write lines on all of the photoconductors are substantially equal;,
periodically determining the number of the PELslice clock timing pulses comprising the length of a separate measuring line on the printhead for each of the photoconductors by the laser beam scanning the measuring line;
using the product of a previously determined ratio of the length of the write line on each of the photoconductors to the length of the corresponding measuring line for use with the same photoconductor and the periodically determined number of the PELslice clock timing pulses for the same photoconductor to determine the number of the PELslice clock timing pulses correlated to the actual length of the write line on the same photoconductor;
and changing the number of the PELslice clock timing pulses for the lengths of the write lines on at least one of the photoconductors so that the write lines on all of the photoconductors are substantially equal.

2 more elements

A method for controlling the length of a write line on each of a plurality of photoconductors produced by a different laser beam simultaneously scanning each of the photoconductors of printheads in a color laser printer to maintain substantially equal lengths of the write lines produced on the photoconductors by the laser beams including:

selecting a fixed frequency of a clock producing equal clock timing pulses for each of the laser beams so that the write lines on each of the photoconductors are substantially equal;.
determining a ratio of the length of the write line on each of the photoconductors to the length of a measuring line on the same photoconductor at the selected fixed frequency of the clock producing equal clock timing pulses for each of the laser beams so that the lengths of the write lines on all of the photoconductors are substantially equal;
periodically determining the length of each of the measuring lines by the number of clock timing pulses produced for each of the laser beams during scanning of the write line on each of the photoconductors by its corresponding laser beam;
using the product of the ratio of the length of the write line on each of the photoconductors to the length of the measuring line on the same photoconductor for each of the photoconductors and the periodically determined number of clock timing pulses during scanning of each of the photoconductors by its corresponding laser beam to ascertain if the length of the write line on at least one of the photoconductors has changed and the amount of change;
and changing the selected number of the clock timing pulses without changing the selected fixed frequency of the clock at selected PELs for each of the laser beams having the length of a write line not substantially equal to a selected value to change the length of each of the write lines not substantially equal to the selected value so that the lengths of the write lines on all of the photoconductors are substantially equal.

2 more elements

A method for controlling the length of a write line on a photoconductor produced by a laser beam scanning the photoconductor in a laser printer to maintain the lengths of the write lines produced on the photoconductor by the laser beam substantially constant including:

selecting a fixed frequency of a clock producing equal clock timing pulses for the laser beam so that the write line has a desired length;
determining a ratio of the length of the write line on the photoconductor to the length of a measuring line at the selected fixed frequency of the clock producing equal clock timing pulses for the laser beam so that the write line has a desired length;
periodically determining the length of the measuring line by the number of clock timing pulses produced during scanning of the measuring line on the photoconductor by the laser beam;
using the product of the ratio of the length of the write line on the photoconductor to the length of the measuring line on the photoconductor and the periodically determined number of clock timing pulses during scanning of the photoconductor by the laser beam to ascertain if the length of the write line has changed and the amount of change;
and changing the selected number of the clock timing pulses for the write line without changing the selected fixed frequency of the clock at selected PELs along the write line to change the length of the write line to the desired length if the length of the write line has changed.

2 more elements

A laser printer including:

a plurality of light receiving elements;
a plurality of scanning means;
each of said scanning means including a laser beam to scan simultaneously a different one of said light receiving elements;
electronic control means for electronically changing the lengths of a plurality of write lines scanned on at least one of said light receiving elements during printing operation to make the write lines on all of said light receiving elements substantially equal when the lengths of the write lines produced by each of said scanning means are not substantially equal;
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 the write line on at least one of said light receiving elements to make the lengths of the write lines on all of said light receiving elements substantially equal;
and periodically determining means for periodically determining the length of each of the write lines;
each of said separate selective changing means including means for changing the number of clock timing pulses for the selected PELs for the write line on at least one of said light receiving elements to change the length of the write line on said at least one light receiving element to make the lengths of the write lines 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 light receiving elements;
and means for utilizing the product of a stored value of a ratio of the length of the 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 at least one of the write lines on said at least one light receiving element to make the lengths of the write lines substantially equal on all of said light receiving elements.

12 more elements

A laser printer including:

a plurality of light receiving elements;
a plurality of scanning means;
each of said scanning means including a laser beam to scan simultaneously a different one of said light receiving elements;
electronic control means for electronically changing the lengths of a plurality of write lines scanned on at least one of said light receiving elements during printing operation to make the write lines on all of said light receiving elements substantially equal when the lengths of the write lines produced by each of said scanning means are not substantially equal;
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 the write line on at least one of said light receiving elements to make the lengths of the write lines on all of said light receiving elements substantially equal;
and periodically determining means for periodically determining the length of each of the write lines;
each of said separate selective changing means including means for changing the number of clock timing pulses for the selected PELs for the write line on at least one of said light receiving elements to change the length of the write line on said at least one light receiving element to make the lengths of the write lines substantially equal;
offset producing means for producing an offset at locations in each of the write lines on each of said light receiving elements at which the number of the clock timing pulses for each of the selected PELs is changed;
and said offset producing means including means for producing a constant offset for each of the write lines on each of said light receiving elements but beginning the first offset for each of the write lines at a different PEL than adjacent write lines.

8 more elements

A method for controlling the length of a write line on each of a plurality of light receiving elements produced by a different laser beam simultaneously scanning each of the light receiving elements of printheads in a color laser printer to maintain substantially equal lengths of the write lines produced on the light receiving elements by the laser beams during printing operation including:

periodically determining the length of the write line on each of the light receiving elements by
determining the number of PELslice clock timing pulses of a PELslice clock comprising the
length of each of the write lines on each of the light receiving elements during printing operation;
and changing the length of the write line on at least one of the light receiving elements so that the lengths of the write lines on all of the light receiving elements are substantially equal by changing the number of the PELslice clock timing pulses for the write line on the at least one light receiving element so that the lengths of the write lines on all of the light receiving elements are substantially equal.

1 more element

A method for controlling the length of a write line on each of a plurality of light receiving elements produced by a different laser beam simultaneously scanning each of the light receiving elements of printheads in a color laser printer to maintain substantially equal lengths of the write lines, produced on the light receiving elements by the laser beams including:

selecting a fixed frequency of a clock producing equal clock timing pulses for each of the laser beams so that the write lines on each of the light receiving elements are substantially equal;
determining a ratio of the length of the write line on each of the light receiving elements to the length of a measuring line on the same light receiving element at the selected fixed frequency of the clock producing equal clock timing pulses for each of the laser beams so that the lengths of the write lines on all of the light receiving elements are substantially equal;
periodically determining the length of each of the measuring lines by the number of clock timing pulses produced for each of the laser beams during scanning of the write line on each of the light receiving elements by its corresponding laser beam;
using the product of the ratio of the length of the write line on each of the light receiving elements to the length of the measuring line on the same light receiving element for each of the light receiving elements and the periodically determined number of clock timing pulses during scanning of each of the light receiving elements by its corresponding laser beam to ascertain if the length of the write line on at least one of the light receiving elements has changed and the amount of change;
and changing the selected number of the clock timing pulses without changing the selected fixed frequency of the clock at selected PELs for each of the laser beams having the length of a write line not substantially equal to a selected value to change the length of each of the write lines not substantially equal to the selected value so that the lengths of the write lines on all of the light receiving elements are substantially equal.

2 more elements

A method for controlling the length of a write line on a light receiving element produced by a laser beam scanning the light receiving element in a laser printer to maintain the lengths of the write lines produced on the light receiving element by the laser beam substantially constant including:

selecting a fixed frequency of a clock producing equal clock timing pulses for the laser beam so that the write line has a desired length;
determining a ratio of the length of the write line on the light receiving element to the length of a measuring line at the selected fixed frequency of the clock producing equal clock timing pulses for the laser beam so that the write line has a desired length;
periodically determining the length of the measuring line by the number of clock timing pulses produced during scanning of the measuring line on the light receiving element by the laser beam;
using the product of the ratio of the length of the write line on the light receiving element to the length of the measuring line on the light receiving element and the periodically determined number of clock timing pulses during scanning of the light receiving element by the laser beam to ascertain if the length of the write line has changed and the amount of change;
and changing the selected number of the clock timing pulses for the write line without changing the selected fixed frequency of the clock at selected PELs along the write line to change the length of the write line to the desired length if the length of the write line has changed.

2 more elements

Dependencies are inferred from the claim text.

Electronic control arrangement for a laser printer

Life of this patent

Electronic control arrangement for a laser printer

Life of this patent

Abstract

Claims48