RIP/Controller Technology

There are several functions which are required in order to deliver data to a raster marking engine. Data must be captured, converted to an appropriate driving signal, and synchronized with the marking engine. Mundane services such as feeding paper, starting the engine, checking for jams, and the not-so-mundane task of jam recovery must be provided. Additional features may also be incorporated. Although sometimes difficult to isolate, the system component most often associated with this level of processing function is referred to as the Controller. Additionally, the Controller also serves to connect a marking engine to host systems: connectivity and many user features are dependent upon it.

A Raster Image Processor is often combined with a Controller to allow a broader range of data support, including non-raster formats. Its level of functionality may vary; current RIPs generally transform page description data (in a format such as Hewlett-Packard’s PCL or Adobe’s PostScript) into full raster format, but a less complex RIP may simply manipulate a bitmap before feeding it to the controller. Ultimately, it may be paired with a Job Controller to provide many features normally associated with full computer operating systems. Under guidance of the controller, the RIP feeds raster data to the marking engine. All algorithmic quality enhancements are performed by the RIP/Controller and both print speed and quality are often more a function of the RIP/Controller technology than of the engine. Since the engine will image any data fed to it from the RIP, the success or failure of a job to print correctly can be solely determined by its capabilities.

In one architecture, the controller works as a traffic cop for page description data entering from a host computer, directing and merging such elements as feature selection information for the marking engine, raster data supplied by the RIP, and storage queries for resources the RIP may request from a hard disk. Variations on this setup allow for a less robust controller, but still contain many of these functions. While an embedded RIP may be integrated into the printer with a controller and marking engine, host-based RIPs are implemented as software on a standard workstation; they serve the same functions. Additionally, host-based RIPs may utilize workstation operating system features to provide connectivity and user interface as well as the data stream for the marking engine controller. Cost, versatility, and functionality issues may make host-based RIPs a better solution in some cases, and embedded RIPs a better solution in others. A third solution, that of putting the RIP functionality in a stand-alone unit, offers another cost/performance tradeoff, particularly when multiple marking engines may be driven. All three basic RIP implementations: embedded, host-based, or stand-alone, have benefits within the scope of certain applications; they tend to be better suited to different situations.