Eastman-kodak Company

Pin S Tschang

Hieu T Pham

Kenneth D Kieffer

Eric Karl Zeise

Yee S Ng

Jeremy K Chung

John S Hayward

Charles E Ayers

Benjamin B Snavely

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 printhead, for example one that includes a plurality of LEDs, is driven by a current that is programmed to have a linear temperature profile with a desired slope. The change in current with temperature facilitates maintaining of LED uniformity. Linearity between various stages of driver circuitry is maintained by a digital-to-analog converter that includes transistors arranged in a common centroid configuration. Driver current to each LED is provided by a master slave circuit that is dedicated to each LED. Thus, cross-talk between LED channels is minimized.

Non-impact printhead and driver circuit for use therewith

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

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.

Dot printer with token bit selection of data latching

A hybrid color image sensing array includes: (a) an array of semiconductor image sensing elements, each element having superposed upper and lower light responsive channels for producing first and second photosignals, the intrinsic spectral responses of the channels being different due to the differential absorption of light by a semiconductor material; and (b) an array of color filter elements disposed over the array of image sensing elements, the array of filter elements having: (1) elements of a first relative transmittance type adapted to tailor the spectral responses of an image sensing element such that the photosignals produced by the element possess a component representing the response of the element to light in a first preferred spectral region and a component representing the response of the element to light in a second spectral region, and (2) elements of a second relative transmittance type adapted to tailor the spectral responses of the image sensing element such that the photosignals produced by the element possess a component representing the response of the element to light in the first spectral region and a component representing the response of the element to light in a third spectral region. Known matrixing procedures are employed to separate a relatively high resolution first signal and relatively lower resolution second and third signals from the photosignals produced by the hybrid color image sensing array.

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Rochester, NY, United States of America

Pin S Tschang