Lexmark International, Inc.

Craig Palmer Bush

Martin Christopher Klement

Eric Wayne Westerfield

Roger Steven Cannon

Wilson Morgan Routt, Jr

Daniel Richard Klemer

David John Mickan

David Brian Langer

Daniel Eugene Pawley

Cyrus Bradford Clarke

Phillip Byron Wright

Philip Jerome Heink

Thomas Campbell Wade

Steven Jeffrey Harris

Johnny Ray Sears

Mark Edwin Kirtley Lund

Timothy A Green

David Kurt Klaffenbach

E Dawson Ward

Jeffrey Thomas Hines

Methods and apparatus include improving print quality of a bi-directionally scanning electrophotographic (EP) device, such as a laser printer or copy machine, according to ambient pressure in which operated. A moving galvanometer or oscillator reflects a laser beam to create scan lines of a latent image in opposite directions. A damping of the motion occurs per air density implicated by temperature and pressure, where the pressure changes occurring especially from altitude changes. During use, a drive signal, such as a pulse train, moves the galvanometer or oscillator at or near its resonant frequency. Based on a parameter of the drive signal, such as pulse width, the ambient pressure can be made known. In general, a high-pressure environment requires a relatively longer pulse width to resonate the galvanometer or oscillator in comparison to a shorter pulse width for a low-pressure environment. Corrections to print quality stem from the determined ambient pressure.

Obtaining pressure of an operating environment of a bi-directionally scanning electrophotographic device for implementing corrections per pressure

Obtaining pressure of an operating environment of a bi-directionally scanning electrographic device for implementing corrections per pressure

In a bi-directionally scanning electrophotographic (EP) device, methods and apparatus include storing alignment information. In one aspect, pre-characterization parameters of the EP device are stored in memory, such as NVRAM, resistant to the removal of power. In another, actual parameters of the EP device are learned during calibration and stored in the same memory. A controller has local or remote access to the memory and makes comparisons of the pre-characterized and learned parameters to implement corrections. Especially, scan alignment corrections are implemented to alter future scanning of scan lines of latent images on a photoconductor whereby the scan lines are formed in alternating directions. Certain contemplated parameters include, but are not limited to, a scan detect to print distance from a sensor to the start of imaging, temperature, pressure, a scanning mechanism drive signal parameter, such as pulse width, or sensor delay information.

Methods and apparatus for storing alignment information in a bi-directionally scanning electrophotographic device

Methods and apparatus include improving print quality of a bi-directionally scanning electrophotographic (EP) device, such as a laser printer or copy machine, according to temperature. A moving galvanometer or oscillator reflects a laser beam to create forward and reverse scan lines of a latent image. During use, the actual ambient temperature is obtained and used make corrections to improve print quality, such as by producing the latent image with a signal altered from an image data input signal to help ensure proper alignment of the forward and reverse scan lines.

Thermal compensation of bi-directional alignment in a bi-directional laser scanning unit

In bi-directional imaging, such as bi-directional printing, a driving mechanism scans a light beam through a scan path across an imaging window. A controller enables transmission of video data to a modulator when the light beam is positioned for imaging on the imaging window. Video data is transmitted to the modulator when the light beam is traveling in a forward direction or a reverse direction across the imaging window, whereby a modulated light beam is capable of producing an image when traveling in the forward or reverse directions. The controller adjusts scan durations or image rasterization rates to ensure that each scan is properly aligned with the prior and subsequent scan.

Bi-directional scanning and imaging with scanning compensation

A method for operating a torsion oscillator at its resonant frequency. The method performs an open-loop frequency sweep starting with nominal operation parameters saved from the factory or from a previous operation of the torsion oscillator. The sweep determines an open-loop resonant frequency and an open-loop drive level. A closed-loop resonant frequency sweep is performed and a closed-loop steady-state resonant frequency is determined. This frequency is used to calculate a closed-loop overshoot and a closed-loop steady-state drive level. The torsion oscillator is then operated in a closed-loop mode at the closed-loop steady-state resonant frequency and starting at the closed-loop steady-state drive level. Finally, the nominal operation parameters are updated and stored in non-volatile memory. The method minimizes the effects of ambient environmental conditions including air density on the steady-state operation of the torsion oscillator.

Method of determining resonant frequency

A circuit includes a switching device for controlling a power signal to be applied to a heating device. A control circuit is configured for comparing a temperature signal, indicative of the temperature of the heating device, to a temperature setpoint to generate a gate pulse signal that controls the duration of the power signal to be applied to the heating device. The control circuit is further configured for comparing the duration of the power signal to be applied to the heating device to a minimum pulse duration and, if the duration of the power signal to be applied to the heating device is at least equal to the minimum pulse duration, providing the gate pulse signal to the switching device.

Power control system and method for regulating power provided to a heating device

A bi-directional electrophotographic raster imaging system that sweeps a modulated light beam across an imaging region of a photosensitive surface to create both forward-going and reverse-going scanlines of dot data on the imaging region, and which compensates for image misalignment that may be caused by varying the power used to drive a laser light source that generates the modulated light beam. An SOS photosensor detects the beginning of each scanline in both forward and reverse directions, outputting an SOS signal used to create both forward and reverse margins. When the laser power is varied, compensating data is used to correct the forward and reverse margins to keep them aligned (straight), even though the beginning of the scanline locations for both forward and reverse scans are affected in opposite directions by an increase or decrease in laser power.

Method and apparatus for compensating for image misalignment due to variations in laser power in a bi-directional raster imaging system

An improved method and apparatus for controlling a scanning laser are provided by the present invention. In accordance with a preferred embodiment, a single feedback sensor is placed along the scan path of a scanning laser such that it senses the laser twice during each scan. The time intervals between the sensor sensing the laser are measured and examined to determine the position and direction of the scanning laser. These time intervals may also be used to ensure that the scanning device is operating at its resonant frequency. In systems that require detecting the laser as it enters and leaves the imaging window, a reflective device is used to create a beam path from the edge of the imaging window back to the single feedback sensor such that the sensor detects the laser four times during each scan. In such an embodiment, the drive signal used to scan the laser along its scan path can be compared to the pulses received from the sensor to determine whether or not a detected time interval corresponds to a particular physical portion of the scan path.

Device for determining position and movement of scanning laser beam

An imaging system in which a modulated light beam is reflected by a reflection surface oscillated by a torsion oscillator, such imaging system being capable of operating dynamically to adjust to the change in resonant frequency of the torsion oscillator. The resonant frequency of the torsion oscillator varies with ambient temperature and with other factors, such as amount of use. Sensors sense the sweep of the light beam to determine a currently existing resonant frequency of the torsion oscillator. The rate of modulation of the beam by a laser is adjusted to conform the modulation in the sweep direction to the desired resolution of the image. Similarly, the speed of movement of a surface being imaged is adjusted to conform the modulation to the desired resolution in the direction perpendicular to the sweep direction. Optionally, the electrical drive frequency of the torsion oscillator may also be adjusted to correspond with the currently existing resonant frequency during physical operation. The resulting image is improved in visual quality.

Oscillator imaging with control of media speed and modulation frequency

A method and device for managing and controlling a scanning system that incorporates multiple oscillating scanners is provided by the present invention. In accordance with the preferred embodiment, a resonant frequency is determined for each of the scanners. A drive signal for driving the oscillating scanners is generated based upon the determined resonant frequencies. An amplitude adjustment circuit determines the difference between the drive signal frequency and the resonant frequency of each oscillating scanner and adjusts the amplitude of the drive signal provided to that particular oscillating scanner such that scan amplitude of each oscillating scanner is approximately equal. The offset from the resonant frequency is also used to calculate a phase adjustment for the drive signal to insure that the oscillating scanners are operating in tandem.

Scanning with multiple oscillating scanners

In bi-directional imaging, such as bi-directional printing, a galvanometric oscillator scans a light beam through a scan path across an imaging window. A controller enables transmission of video data to a modulator when the light beam is positioned for imaging on the imaging window. Video data is transmitted to the modulator when the light beam is traveling in a forward direction or a reverse direction across the imaging window, whereby a modulated light beam is capable of producing an image when traveling in the forward or reverse directions.

Bi-directional galvonometric scanning and imaging

Laser printers are designed assuming the actual laser operates at nominal values which are the average or central values of a large batch of such lasers. The nominal values are determined and stored in permanent memory. Similarly, the values of the laser actually in the printer are determined during manufacture and also stored in permanent memory. Data to the laser is adjusted to correlate the output called for by the data with the differences in response of the laser of the printer by determining the optical output called for by the data using the nominal values stored and then finding the power needed to achieve the same output using the actual values stored. This is particularly useful with extreme duty cycles.

Laser drive compensation by duty cycle and power

Compensation for beam separation of multiple laser beams of a laser printer simultaneously scanning a photoconductor drum is automatically made. The time for the lead beam to travel a predetermined distance is ascertained and then the separation time between the lead beam and one of the remaining beams is determined. When using only one light sensor, the time for the lead beam to travel the predetermined distance is the scan time of the lead beam. When using two light sensors, the time for the lead beam to travel the predetermined distance is the time for the lead beam to travel between the two light sensors, which define the predetermined distance, in the same scan. This determination of the time for the lead beam to travel the predetermined distance and its separation time from another of the remaining beams is continuously made for all of the remaining beams even during printing. If the beam separation time of each of the remaining beams from the lead beam is large enough for the one light sensor to generate distinct pulses for the lead beam and any one of the remaining beams during the same scan, the separation time for any one of the laser beams can be directly measured in only one scan.

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Lexington, KY, United States of America

Craig Palmer Bush