Hewlett-Packard Company

Douglas L Franz

Mark S Hickman

Majid Azmoon

Donald G Harris

Nicholas Nicoloff, Jr

John A Christianson

Richard I Klaus

Thomas B Pritchard

Casey D Hoekstra

King W Yeung

In the preferred form, a scanning carriage in a color inkjet printer houses a high resolution printhead for black (or monochrome) printing and one or more lower resolution printheads for color printing. The nozzle arrangements, paper feed increments, and ink drop firing frequency for the black printhead and color printhead(s) are selected to provide various alignments between the larger color ink dots and the smaller black ink dots to achieve maximum ink coverage with a minimum of ink or to achieve additional color shades.

Dot alignment in mixed resolution printer

An inkjet printer is disclosed with mixed print resolution capabilities. The printed dots have a high resolution monochrome component such as black and lower resolution components such as cyan, magenta and yellow. For increased throughput, a higher resolution black printhead has a wider swath. Various alignments between the printheads and printed dots are disclosed. In one embodiment, the top edges of the smaller color printheads are aligned in a scanning carriage at or near the top of the wider black printhead. In other embodiments, the bottom edges of the smaller color printheads are aligned at or near the bottom of the wider black printhead. In another embodiment, the small color printheads are centered with the wider black printhead.

Alignment of differently sized printheads in a printer

The method approximates full color resolution by combining dot-on-dot (DOD) and dot-next-to-dot (DND) techniques in printing images received from a computer. The method prints with DOD at the edge of an image or in a depleted area within an image and prints with DND elsewhere within the image to conserve printing time and ink. In the method, the color for each dot of the image is stored, and the image is divided into subgroups of four dots each. Each dot is then tested for significance by looking at whether other dots within the group or adjacent to the group are white. The color for each dot is mapped to one or more colors for printing, the mapping depending on the significance status of at least one dot within the subgroup. In this manner the image is checked for solid and depleted areas of color so that the minimum number of dots are printed within each subgroup.

Method for approximating full resolution color printing

Digital integrated circuit testable input/output pad logic includes modified output driver logic and a latch for storing a test bit provided externally at the I/O pad terminal. The output driver logic selects either the normal pad output signal (O) for output during normal operation, or the stored test bit (S) or its complement (S') for output during a test operation. The output driver logic and latch are controlled by control logic signals (DP,SP,NDN,LS,NLS,NSN) derived from common tri-state (NTR) and latch (NTM) test signals provided externally at dedicated test pins (NTR,NTM). The control logic signals are provided over a bus to all similar testable I/O pads for testing all testable I/O pads within the IC under control of the two test signals.

Testing integrated circuit pad input and output structures

A drop detector having a piezoelectric membrane mounted to a substrate is presented. When a drop strikes the piezoelectric membrane, the membrane vibrates at a selected resonant frequency. The resonant frequency is selected to enhance the sensitivity of the drop detector and the signal-to-noise ratio of the output. The value of the selected resonant frequency depends on the type of material used for the piezoelectric membrane, the thickness of the membrane, the mounting of the membrane to the substrate, and other parameters such as the coating on the membrane. The vibrations of the membrane produce an output signal having a frequency equal to the selected resonant frequency. Since the frequency of the output signal is known, the output signal can be filtered with a bandpass filter to enhance the signal-to-noise ratio of the output signal. The resulting membrane drop detector is a high sensitivity, high signal-to-noise ratio drop detector.

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Vancouver, WA, United States of America

Douglas L Franz