Eastman-kodak Company

Hieu T Pham

Yee S Ng

Pin S Tschang

Eric Karl Zeise

Kenneth D Kieffer

Jeffrey Alan Small

Martin Potucek

Mary A Hadley

Edwin A Hediger

Shawn Edward O'Hara

Daniel C Abbas

William L Chapman

Keith W Agar

Michael M Mattern

Charles E Ayers

A product and process for an LED printhead used in electrophotographic printing that generates an exposure clock on the printhead for the LEDs. The present invention provides a high-speed interface that transmits print data that has been modified, or corrected, using the corresponding unique printhead brightness data as the base reference source data to the printhead boards. The corrected print data is then applied to the LED drivers that expose each LED simultaneously and uniquely. A non-linear clock is applied to the LED drivers as the reference clock to create the unique LED on time circuit. An Exposure RAM stores the data as parallel 8-bit data. A LATCH code received at an ASIC converts the Exposure RAM data into a serial bit stream. The preferred embodiment employs a 60 MHz clock, however, it should be readily apparent that numerous other clocking speeds can be employed. From this a linear or non-linear clock stream is created allowing 256 unique (linear or non-linear) exposure on times to the printhead driver circuitry. This is accomplished with a non-linear clock stream which allows a unique period for each clock period which then allows each increment of exposure time to be unique.

Multiple-level printhead using embedded high speed serial data and control link with on-board exposure clock generation

A non-impact printer apparatus and method wherein enabling waveforms for enabling a plurality of recording elements for recording pixels are characterized by pulse durations that can vary by one exposure clock pulse period with some recording elements being enabled after others so that some of the benefits of center pulsewidth modulation (CPWM) are provided without the disadvantages of CPWM of pulsewidths being at least two exposure clock periods apart.

Non-impact printer apparatus and method of printing with improved

A non-impact printer apparatus includes a printhead having a plurality of recording elements. Nonuniformities in emission characteristics of the recording elements are corrected using look-up tables (LUT) assemblages that include a first LUT wherein the recording elements are binned in accordance with bin values associated with their emission characteristics and a second LUT wherein bin values, output from the first LUT are used to address various tables providing exposure correction. The first and second LUTs are advantageously dual port RAM devices that allow operation during printing while simultaneously allowing loading of data into the tables for use for subsequent printing. Thus, process conditions may be continually monitored and correction data updated without delaying of current printing which may occur using correction data already stored in the LUT assemblages.

Apparatus and method for grey level printing with uniformity correction

A non-impact recording apparatus for recording grey level exposures, the recording apparatus includes one or more recording elements such as LEDs. Image data signals of a predetermined multibits per pixel bit-depth dimension are generated by a data source along with a signal representing the predetermined bit-depth dimension. An exposure clock counter counts exposure clock pulses and outputs a count signal in response to clock pulses. The count signal represents a count value. A comparator compares a multibits-per-pixel image data signal with the count signal from the counter and generates a signal. A current driver is responsive to the signal from the comparator and controls a recording duration. Counting in the counter is adjusted in accordance with the multibits per pixel bit-depth dimension of the image data signal.

Dot printer and method for grey level recording with different bit-depth

A color image-forming apparatus comprises an electrophotoconductive imaging member moving in a first direction. A first corona charger forms an electrostatic charge on the imaging member. A first exposure device such as a laser or LED printhead imagewise modulates the electrostatic charge on an area of the member comprising an image frame. A first developer station develops a first visible image on the image frame with a pigmented toner of a first color. A second corona charger electrostatically charges the image frame having the visible image. A second exposure device such as a laser or LED device imagewise modulates the electrostatic charge on the image frame that was formed by the second charger. A second visible image is then formed on the image frame with a pigmented toner of a second color. The first and second visible images are transferred to a surface of a receiver sheet to form a two-colored image thereon. One of said first and second exposure devices is a raster printer that records rasterized lines of image data in a direction transverse to the first direction. The raster printing includes means for storing data representing bow error in printing of a raster line. Printing is done in response to image data and bow error data for recording substantially straight raster lines of image dam.

Electrophotographic image recording apparatus and method with correction

A non-impact dot printer such as an LED printer, records grey levels of each dot by pulse width modulating the exposure on-time for each LED. The on-time of each LED for each exposure is controlled by comparing a count, representing an exposure time, with a second time changing count. The time changing count changes in accordance with clock periods of varying periodicity that are determined in accordance with human perception response criteria. This allows for the need for fewer data bits to define grey scale and exposure correction information reducing the number of data lines otherwise required.

Dot printer and method for grey level recording and circuit for use in

A non-impact printer apparatus is described that includes a recording head having a plurality of recording elements such as LED's for recording on a recording medium. A plurality of driver chips are provided on the head and each includes a plurality of current driving channels for selectively driving a plurality of recording elements in accordance with respective image data signals. The driver chips each further include an extra current driving channel not associated with a recording element for generating a current related to that sent to said recording elements. Monitoring of the current in the extra channel is provided to permit for changes of current to the recording elements and/or corrected image data to provide fine tuned control over uniformity of the recording elements.

L.E.D. array printer with extra driver channel

An LED printhead or the like includes a data bus for carrying multibit digital image data signals for grey level recording. A token bit signal is generated and shifted through registers upon the printhead to enable image data registers associated with each LED to latch the image data signals in appropriate order. The image data signals control the energization times for recording pixels. A digitally adjustable current mirror controls the level of current to each LED during recording. Digital current data signals for controlling this level of current are also communicated over one of the lines of the data bus. A token bit signal is also used to control the latching of current data signals in registers storing the digital data used for current control.

Non-impact printer with token bit control of data and current regulation

An improved printer apparatus includes a print head having a series of point-like radiation sources, such as LED's, arranged in a row for exposing a recording medium. Logic means is provided for determining which of the point-like radiation sources are to be selected for energization. A current driver means responsive to the logic means provides electrical current to the radiation sources selected. A current driver means include a current mirror having a master circuit for generating a reference current and a plurality of slave circuits for providing respective driver currents to the radiation sources selected for energization. The master circuit includes a resistor of the type that at least prior to adjustment permits for substantially continuous adjustment of driver current over a range of resistance values. Two independent power supplies are provided to the print head. One power supply provides electrical energy for the logic device at a fixed voltage suitable for the logic devices. A second power supply provides the electrical energy for illuminating the point-like radiation sources. Thus, power to the logic devices is isolated from noise generated during energization of the point-like radiation sources. A variable voltage is provided by this second power supply to permit for flexibility in adjustment of the currents to the point-like radiation sources. This variable voltage may be adjusted in response to aging of the LED's or temperature of the print head.

Printer apparatus

An improved printer apparatus includes a print head having a series of point-like radiation sources, such as LED's, arranged in a row for exposing a recording medium. Logic means is provided for determining which of the point-like radiation sources are to be selected for energization. A current driver means responsive to the logic means provides electrical current to the radiation sources selected. A current driver means include a current mirror having a master circuit for generating a reference current and a plurality of slave circuits for providing respective driver currents to the radiation sources selected for energization. The master circuit includes a series of parallel connected transistors that may be instantaneously reprogrammed by digital control signals to said transistors. The characteristics of the transistors vary so that currents from them are scaled by say powers of two to provide an expanded current control capability. Environmental conditions and/or aging often require change in current to maintain desired recording performance. The need for such change may be automatically sensed and a new digital control word sent to the transistors to adjust current to the radiation sources.

Non-impact printer apparatus with improved current mirror driver and

Modular optical LED printhead arranged for a fixed focus distance outside the printhead structure. A supporting and registration plate contains a rectangular opening in which the lens is located. The plate is secured to the overall LED supporting structure of the printhead by end members which, with side members, completely seal the LED's and connections from contaminants. The registration plate has at least two surfaces thereon which mate with surfaces in the associated apparatus to accurately position the plate. During the alignment process of the printhead, the lens and plate are adjusted to provide a focus at a fixed distance from one of the registration surfaces of the plate. Alignment of the lens across the axis of the LED array is provided by recessed set screws and a shim. Because of the fixed distance from the registration surface, the printhead can be installed in suitably constructed apparatus without further alignment.

Modular optical printhead for hard copy printers

A circuit for generating a set of center pulse-width modulated waveforms comprises a counter having a time changing count, and comparators which compare the count with respective preset counts. The preset counts to the comparators being set so that the set of waveforms created is center pulse-width modulated.

Circuit for generating center pulse width modulated waveforms and

In a non-impact dot printer, such as an LED printer, multiple bits of image data determining the on-time of each LED are latched into an appropriate data register in accordance with a token bit that is passed along a shift register. The shift register is preferably bi-directional to permit for selection of direction wherein identical driver circuitry is provided on opposite sides of a line of LED's.

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Webster, NY, United States of America

Hieu T Pham