Lexmark International, Inc.

John Bruce Berry

Keith Bryan Hardin

John Parker Richey

William Pohl Corbett, Jr

James Ronald Booth

Robert Michael Tulenko

An imaging device has a photoconductor with a surface that is selectively discharged by a light from a laser diode to create a latent electrostatic image for attracting toner for transfer to a media. A circuit drives the laser diode. The circuit has a switch for turning on and off the light, a resistor complementary to the laser diode selectively connectable to the switch, and a passive circuit component coupled to the laser diode. The passive circuit component is a delay line, inductor, choke, coiled wire, or ferrite bead is contemplated. It may also typify a length of copper tracing on a printed circuit board that supports the laser diode. The circuit causes an initial overshoot voltage spike in an on voltage pulse that is about 20% or more than the settled on voltage. The voltage spike dampens out in about one-fourth of a total voltage on time of the pulse.

Circuit for driving a light source in imaging device for enhancing quality of isolated pixels

A scanning system for use in an imaging apparatus includes a first light source and a second light source for emitting light beams for generating an image. A driver circuitry has first and second outputs connected to the first and second light sources, respectively, for controlling the first and second light sources. A signal transmitter includes a first interface for communicating a clock signal to the driver circuitry and a second interface for communicating an image information signal to the driver circuitry. During a clock cycle of the clock signal, the driver circuitry captures a first bit information from the image information signal at a rising edge of the clock signal and a second bit information from the image information signal at a falling edge of the clock signal. Thereafter, the driver circuitry drives the first and second light sources based on the first and second bit information captured, respectively.

System and method for controlling multiple light sources of a laser scanning system in an imaging apparatus

An improved clock generation circuit is provided that operates with a single input clock frequency, and includes a Phase Locked Loop circuit (PLL) with a digital accumulator in the feedback loop, in which either the Most Significant Bit or the Carry Bit of the binary adder is used as the modulated feedback clock to the phase/frequency detector of the PLL. In one embodiment, a fixed add/phase amount is used to drive one of the inputs of the binary adder to generate a fixed output frequency. If it is desired to modulate the output frequency, then an Add Amount Modulator circuit can be provided that presents a varying numeric value to one of the inputs of the binary adder. The MSB or Carry Bit is communicated to an address look-up table, which then outputs an address to a memory circuit, which in turn presents a different add amount to the binary adder. If a periodic modulation is desired, the address look-up table will point to add amounts that create a particular periodic output frequency profile, which could include a Spread Spectrum profile. Certain optional circuits may be included, such as: a pre-multiply or pre-divide circuit to either increase or decrease the frequency of the input clock signal before it reaches the phase/frequency detector of the PLL; an output divider to provide a lower output clock frequency; a feedback divider to lower the VCO's output frequency before it is directed into the digital accumulator; a synchronizing input (Sync Input); a synchronizing output (Sync Output); a Base Number register to keep the memory size of the look-up table to a reasonably small value; or a Start Number register to provide the add amount upon initialization.

Method and apparatus for providing a clock generation circuit for digitally controlled frequency or spread spectrum clocking

An electrophotographic image forming apparatus transfers image information relating to an image to be formed on a medium, while maintaining desired low levels of electromagnetic emissions. The apparatus includes an image processor that generates low-frequency image information signals containing the image information. A low-frequency interface is connected to the image processor for transferring the low-frequency image information signals. A control circuit, connected to the low-frequency interface, receives the low-frequency image information signals generated by the image processor. The control circuit operates on the low-frequency image information signals to form a high-frequency image information signal therefrom, where the high-frequency image information signal contains the image information. The apparatus also includes a high-frequency interface connected to the printhead control circuit for transferring the high-frequency image information signal. An image formation device, connected to the high-frequency interface, forms an image on the medium. The image formation device forms the image based on the image information contained within the high-frequency image information signal.

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Lexington, KY, United States of America

John Bruce Berry