Hp Indigo B.v.

Hewlett-packard Development Company, L.P.

Oron Ambar

Haim Vladomirski

Yuval Yunger

Zvi Erlich

Craig Breen

Guy Nesher

Tal Frank

Rodolfo Jodra Barron

Vladimir Shalmai

A light source adjustment apparatus is disclosed. The light source adjustment apparatus includes processing apparatus to receive a scanned image of a pattern printed by a print apparatus onto a printable medium, the pattern including a plurality of blocks of print agent of a first colour printed during a printing operation in which light sources of a light source array irradiate a photoconductive surface; analyse the scanned image to identify a region of non-uniformity within the plurality of blocks of print agent; correlate a location of the identified region of non-uniformity with a corresponding light source in the light source array; determine, based on the identified region of non-uniformity, an adjustment to be made to a parameter of the corresponding light source; and generate a signal to effect the determined parameter adjustment with regard to the corresponding light source. A method and a print apparatus are also disclosed.

Adjusting print apparatus light sources

A focus adjustment method is disclosed. The focus adjustment method includes depositing, using a print apparatus, print agent onto a printable substrate, the print apparatus comprising a photoconductive surface and a writing head having a first end and a second end, the writing head having an array of light sources to emit radiation onto the photoconductive surface during a printing operation. The method also includes during said depositing, moving the writing head relative to the photoconductive surface, between a first position and a second position, to create a printed image. The method also includes determining, based on the printed image, for each of a plurality of locations along the writing head, a position of the writing head relative to the photoconductive surface at which the writing head is most focussed. The method also includes calculating, using processing apparatus, a position of the first end of the writing head and a position of the second end of the writing head relative to the photoconductive surface at which the focus of the writing head at the plurality of locations is within a defined threshold. The method also includes adjusting the position of the first end of the writing head and the second end of the writing head relative to the photoconductive surface according to the calculated positions. A print apparatus and the machine-readable medium are also disclosed.

Focus adjustment in print apparatus

In an example, a method includes determining a first scaling to be applied to a first print operation and a second scaling to be applied to a second print operation. Each print operation includes selectively removing charge from a charged photoconductor by irradiating the photoconductor in a plurality of scans, forming a first print agent pattern on the photoconductor and delivering the first print agent pattern to a substrate. If the first and second scalings are different, a control instruction may be determined to change the scan-to-scan spacing between the first and second print operations.

Controlling scan-to-scan spacing between print operations

In an example, a method includes determining an indication of pixel separation for an image region to be printed to a substrate. A power level of a laser light source to address a pixel on a region of a photoconductive surface corresponding to the image region may be adjusted based on the indication of pixel separation to compensate for print spot size variation associated with pixel separation.

Adjusting power levels to compensate for print spot size variation

Certain examples described herein relate to an optical controller () for an exposure unit () of a printer. In certain examples, memory () stores a plurality of data structures each comprising adjustment factors useable to adjust a plurality of optical elements () of the exposure unit. Different data structures correspond to different gray coverages in an image generated by the printer. In certain examples, a processor () determines gray levels for different image regions in input image data. In certain cases, the processor links the determined gray levels to corresponding data structures within the plurality of data structures to obtain adjustment factors for the different image regions. In certain cases, the processor adjusts the optical elements for each image region using the corresponding obtained adjustment factors to enable the generation of an exposed image using the exposure unit based on the input image data.

Generating an exposed image

An electric cross-talk, ECT, effect of laser-diode array is measured by capturing a first image of a first laser spot of a first laser diode with a second laser diode being turned off () and a second image of a second laser spot of the first laser diode while switching on the second laser diode (). A spot-energy ratio is determined () by processing the images, and an ECT-coupling coefficient on the first laser diode is calculated () by switching the second laser diode. Compensating for the ECT effect includes determining a signal for predicting the ECT effect on the first laser diode by switching the second laser diode, and generating a driving signal based on a desired current profile and the ECT-prediction signal.

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Ness Ziona, Israel

Oron Ambar