Hqn096 - Advanced Inkjet Screens

Technical Note Hqn096
Advanced Inkjet Screens ^TM For Harlequin Core

Introduction

Advanced Inkjet Screens ^TM (AIS) comprises several halftone designs that have been specifically created to mitigate common artefacts arising from inkjet printing at high speed.

They are the result of several years of research and development including printing samples on presses from several dozen different OEM partners, on a wide variety of substrates, and multiple ink technologies, including UV and aqueous.

AIS can be used either with Global Graphics Software's ScreenPro^TM standalone screening engine or with the Harlequin Core SDK. This document is specific to the Harlequin Core.

Prerequisites

Note: The AIS screen tiles may only be used in an Harlequin Core instance when the Advanced Inkjet Screens layered option has been enabled. The precise mechanism for enabling a layered option varies depending on the security model that you're using.

When printing with grayscale heads or in a configuration where multiple nozzles jet onto the same location on the substrate (for example with multiple print bars or multi-pass printing), the AIS tiles should be used in a multi-level halftone. This requires an additional layered option: MLS-Mix.

Please contact your account manager if you wish to obtain a suitable license for either or both options.

Installation

Note: AIS is provided as a separate .zip archive and is not supplied as part of the main HHR installers (either Install anywhere or Zip).

1. 1. Copy/extract all files from the AIS.zip archive into an empty folder.
      1. If the option is offered, select Use folder names.
      2. The top level displays a readme.txt file and a SW folder.
   2. Copy the contents of the SW folder into the SW folder for the HHR. AIS files are merged into the HHR's existing SW directory structure.
   3. To confirm the installation is successful, run the HHR using one of the new TestConfig files supplied in the AIS zip archive.

Choosing which AIS screen to use

As with all screening processes it is difficult to provide definitive advice on which screens will give the best results on a particular print system. However, the Pearl and Opal screens are simplest to configure and use; we suggest starting with those unless you have requirements that are specifically addressed by the Mirror screens.
In general:

• Pearl is the flexible "all-rounder".
• Opal can be more "robust", and should be considered the first-choice screen for higher resolution devices (over 600dpi).

Mirror is specialized for difficult substrates.

Table 1: Mirror screens vs. Pearl and Opal screens

If the notes above suggest use of Pearl or Opal, then start with Opal if the press resolution is 600dpi or above, or Pearl if the press resolution is below 600dpi. Once you are confident in the output you are achieving with your selected screen you should also try the other one of the pair, as there are potentially many complex interacting parameters to consider; it is sometimes difficult to predict reliably which will be better.

Supplied test configurations

The AIS installation includes TestConfig files – as shown in the following table – to show how the Pearl and Mirror screens can be used; these files are in the SW/TestConfig folder.

Table 2: Example TestConfig files

Configuring to use AIS for 1-bit output

Select CMYK-AIS-Pearl-600dpi to produce 1-bit output using the Pearl screen:

• Adjust the TestConfig to vary the InterleavingStyle, SeparationStyle and HWResolution if required to match your device.
• This TestConfig will produce output in CMYK. It's a good idea to test output in that mode first (assuming that your press uses CMYK inks at all).
• If you need to output in additional colorants (for example, Orange, Green, White, etc.), extend the list of colors in the Type 5 halftone, setting HalftoneColor to /E,/F etc. for the additional colorants (up to a maximum of 16 colorants). You should also apply the SeparationDetails and ColorantFamilies and setrendering code that you would normally use to generate output in the required colorant set.

• If you wish to use Mirror instead of Pearl, search and replace all instances of "Pearl" with "Mirror" in the TestConfig.

Configurating to use AIS for multi-level output

If you're printing with grayscale heads, or in-system where multiple nozzles will print on the same location on the substrate, you will need to use multi-level screening.
You'll use a type 1009 halftone to do this; see Technical Note Hqn094: Mixing multi-bit screens. There are also examples in the "Mix" example TestConfigs; see Table 2: Example TestConfig files.
To set the output raster depth to 2- or 4-bit, use the /ValuesPerComponent key in
setpagedevice:
<< /ValuesPerComponent 4 >> setpagedevice % for 2 bit
<< /ValuesPerComponent 16 >> setpagedevice % for 4 bit
Select one of the CMYKPearlMix600dpi, CMYKOGVPearlMix600dpi or CMYKOGVMirrorMix600dpi example TestConfigs. For information see Table 2: Example TestConfig files.

Tooling to create new multi-level screens

Global Graphics Software provides the AIS Tools to assist in selecting the correct multi-level screening parameters. From HHR 13, AIS Tools are applicable for using Mirror, Opal and Pearl screens in HHR. For information see the documentation supplied with them.