Lexmark International, Inc.

Martin Christopher Klement

Roger Steven Cannon

Craig Palmer Bush

Wilson Morgan Routt, Jr

Daniel Eugene Pawley

Eric Wayne Westerfield

Daniel Richard Klemer

Timothy A Green

David John Mickan

John Parker Richey

Christopher Gregory Chee

Steven Jeffrey Harris

Gregory Lawrence Ream

Philip Edwin Riggs

E Dawson Ward

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

Methods and apparatus include aligning printing of a bi-directionally scanning electrophotographic (EP) device, such as a laser printer or copy machine. At least first and second scan lines formed in opposite directions define a calibration page for manufacturing, servicing or end-user operating. The page includes pluralities of diagnostic patterns repeatedly tiled together in various formats. In one instance, a first pattern defines a substantially rectangular cell of pixels (pels) for at least a first and second scan line of opposite directions. A second pattern defines the first pattern except at least one of the pels of either the first and second scan lines is intentionally displaced at least one pel width in the scan direction. Upon repeatedly tiling groups of either the first or second patterns together, multiple bars of the calibration page are formed. A darkest of the bars represents a preferred calibration setting of the EP device.

Print alignment for bi-directionally scanning electrophotographic device

An imaging apparatus includes a controller executing instructions to form a latent image, and a print engine. The print engine includes a laser source, a micro-electromechanical system (MEMS) device, and a module for mounting the MEMS device. The print engine is communicatively coupled to the controller and configured to form the latent image using the laser source and the MEMS device. The module includes a base having a first support and a second support, the second support having a support guide feature; and a bracket attached to the MEMS device. The bracket has a central axis, a first end, and a second end, the second end having a bracket guide feature, the first end being affixed to the first support to form a cantilever arrangement. The support guide feature engages the bracket guide feature to form a sliding joint having a sliding axis substantially parallel to the central axis.

Imaging apparatus having print engine that includes MEMS device

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 system for driving a torsion based on frequency, amplitude and offset control signals includes a pulse width modulator subsystem configured to generate output pulses having controlled pulse durations alternately to each of two channels, the output pulses encoding the frequency, amplitude and offset control signals. A driver circuit is configured for driving the torsion oscillator with a voltage of one polarity during a pulse output to the one of the channels, and a voltage of opposite polarity during a pulse output to the other of the channels.

Torsion oscillator voltage control driver with each of dual voltage polarity for each of dual channel

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 module for mounting a micro-electromechanical system (MEMS) device includes a base having a first support and a second support. The second support has a support guide feature. The module also includes a bracket attached to the MEMS device. The bracket has a central axis, a first end, and a second end. The second end has a bracket guide feature. The first end is affixed to the first support of the base to form a cantilever arrangement. The support guide feature engages the bracket guide feature to form a sliding joint having a sliding axis substantially parallel to the central axis.

Module for mounting a MEMS device

A method reduces the Q factor of the resonant frequency response of a torsional oscillator system in a laser printer, where the Q factor is expressed as a function of the resonant frequency and 3 dB bandwidth of the frequency response. The frequency response of the torsional oscillator system is a function of at least a rotational inertia, a spring constant and a damping constant. The method includes the steps of decreasing the rotational inertia of the torsional oscillator system by a first factor, and decreasing the spring constant by a second factor that is substantially equal to the first factor. The method generally increases component yields, thereby reducing component costs. Also, laser printers using torsion oscillators having reduced Q factors may be used over a wider speed range. Conversely, a single laser printer model may be used at a single speed, rather than at speeds that vary due to variations in resonant frequency. The method also provides for greater freedom of movement of the operating point of the printer during printer development.

Method and apparatus for reducing Q factor in an oscillating laser scanner

A method for determining an operating point of an oscillation controller. The method builds a model of an oscillation device based upon its design parameters. Then the resonant frequency of each specific oscillator is measured in its application environment, and the model, or a table derived from the model is used to define the operating point. The operating point may be expressed in terms of clock counts by factoring in the clock rate of the oscillation controller.

Determining operating point of feedback controller applied to operation of oscillating scanning device

A method for improving the operation of an electrophotographic printer. The method includes providing an electrophotographic printer containing a laser scanning unit. A torsion oscillator for the laser scanning unit is enclosed in closed compartment. The closed compartment includes side walls having first and second side wall edges, a bottom wall attached on the first side wall edges, and a cover attached adjacent to the second side wall edges. The closed compartment is sufficient to reduce stray air currents from adjacent the torsion oscillator thereby improving the operation of the electrophotographic printer.

Laser scanner having reduced air currents

A system for driving a torsion oscillator based on frequency, amplitude and offset control signals includes a pulse width modulator subsystem configured to generate a stream of repetitive pulse signals which encodes the frequency, amplitude and offset control signals, a low pass filter for filtering the stream of repetitive pulse signals to provide a filtered output, and a driver circuit for driving the torsion oscillator based on the filtered output.

Torsion oscillator current control driver

A torsion oscillator (FIG.) is stabilized in operation by determining the current resonant frequency (); in a first procedure, observing the oscillator for change in resonant frequency (), and then restoring the amplitude and median offset () without changing the drive frequency. In an alternative procedure, after determining the resonant frequency (); setting the drive frequency close to but offset from the current resonant frequency (), observing the oscillator for change in resonant frequency (), and the restoring the close offset to the changed resonant frequency (). By operating slightly off peak, the direction of resonant change is immediately known. The first procedure has less difficulties in implementation, but requires more power.

Torsion oscillator stabilization

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.

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Lexington, KY, United States of America

Martin Christopher Klement