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Text of a brochure from HP on the LaserJet III; part number 5952-1442. The brochure contains many diagrams, pictures, and examples which are not found in this file. You should be able to get a copy of the complete pamphlet from your HP dealer. HP LaserJet III printer -- a new standard for the 1990s A primer on Resolution Enhancement technology and PCL 5 printer language Introduction ------------ Hewlett-Packard Company has a reputation for being responsive to user needs; it is part of the corporate culture. But HP is not content simply to respond to user needs. In order to be successful, the company believes it must also anticipate those needs. The introduction of the HP LaserJet printer in 1984 is the best example of this. The printer met customer needs for fast, quiet, high-quality printing and addressed needs they had yet to envision. The HP LaserJet printer established the desktop laser category in the printer market, a category it continues to dominate. To maintain its leadership, HP consistently has sought to establish new standards for price/performance with each new HP LaserJet product. The company believes the HP LaserJet III printer is the laser printer which, in its class, best anticipates customer needs in the 1990s: It meets the user's No. 1 need for improved print quality; provides access to more fonts through on-the-fly font scaling; and increases graphics performance by using vector graphics. The HP LaserJet III printer is the replacement for the and compatible with the HP LaserJet series II. As the replacement for the series II, but with more functionality, the HP LaserJet III printer sets a new price/performance point in the industry. This booklet examines the two principal components which make the HP LaserJet III printer the new print-quality and price/performance standard in office laser printing -- HP's Resolution Enhancement technology and PCL 5 printer language. A Little HP LaserJet History ---------------------------- The introduction of the first HP LaserJet printer in May 1984 established 300 by 300 dots-per-inch (dpi) resolution as the new standard in print quality for business communications. Desktop laser printers brought quick, quiet, quality printing to the business office -- and to the daisy-wheel printer, its demise. Mixing text, graphics and a variety of fonts on one page became not only possible, but affordable. Laser printers changed the look of business documents and established print quality as the No. 1 user requirement in business office printing. Still, however good the text looked with those first desktop laser printers, large areas of black graphics often took on the streaked appearance of a photocopy. In March, 1987, HP took the next step in print quality with the introduction of the HP LaserJet series II printer. Based on a new engine that printed denser blacks, text and graphics took on a crisper, cleaner look. By the beginning of the 1990s, the print quality of the HP LaserJet series II remained the standard against which desktop laser printers were measured. Though competing products had succeeded in matching the print quality of the series II printer, none had exceeded it. That goal has been achieved by the HP LaserJet III printer, with its innovative Resolution Enhancement technology. The Jaggies ----------- The fact remains that laser printers are simply high-resolution dot-matrix printers and suffer from the same print-quality dilemma as their noisy impact cousins -- the 'jaggies.' Jaggies, the stairstep effect on curves and lines that are at an angle other than vertical or horizontal, are caused when a continuous image is broken up into a series of dots and placed on a grid. The obvious solution is to go to higher-resolution printing -- to a denser grid. Such laser printers exist, but users pay a significant penalty in price and speed, a penalty most aren't willing to pay. The New Print-Quality Standard ------------------------------ In the HP LaserJet III printer, HP advances the print-quality standard by combining a variety of technologies to maintain the design fidelity of type when it is scaled, while smoothing edges of both text and graphics. Type fidelity is maintained by using Wilmington, Mass.-based AGFA Compugraphic's Intellifont font-scaling technology in conjunction with its hinted outlines (discussed further in the following PCL 5 section). The edges of text and graphics are then smoothed by the HP-patented Resolution Enhancement Technology --------------------------------- Resolution Enhancement technology improves edge smoothness and prints sharper points and line intersections by intelligently adjusting dot size and position in relationship to neighboring dots. This process is designed to enhance the print quality of both text and graphics without affecting gray-scale images. Dot position is adjusted in the horizontal plane by controlling the on-off timing of the laser beam. This process is used to smooth the jaggies of nearly vertical lines. Dot size is controlled by varying the intensity of the laser beam. This process is used to smooth nearly horizontal lines and to create sharper points and line intersections. Nearly Vertical Lines and Curves -------------------------------- The HP LaserJet III printer's laser beam scans the photosensitive drum from right to left. This makes it possible to shift the dot placement on the grid to the left or right by adjusting the on-off timing of the laser beam; the beam is turned on either sooner or later. The resulting edge of a nearly vertical line or curve looks smoother because the dot's position has been shifted closer to neighboring dots. The benefits of this process are apparent in italic text as illustrated below. Nearly Horizontal Lines and Curves ---------------------------------- Smoothing nearly horizontal lines and curves is technically more complicated than the process described for vertical enhancements. Horizontal smoothing is achieved by varying dot size. Illustrated below is a nearly horizontal line printed without the benefit of Resolution Enhancement. This same jagged effect occurs on horizontally oriented curves as illustrated below with the lowercase CG Times "r." Resolution Enhancement modulates the intensity of the laser beam to address the problem. This deposits smaller than normal amounts of energy on the photosensitive drum. The drum, in turn, attracts a smaller amount of toner and produces smaller dots. Resolution Enhancement precisely controls the size of a printed dot by modulating the laser beam. Its smoothing effect is created by placing dots that have been divided in 20 percent increments into corollary relationships. The 20 percent dot is placed opposite the 80 percent dot, the 40 percent dot opposite the 60 percent dot and so on to create a line that appears uniform in width. This smoothing is apparent on the enhanced nearly horizontal line below. Sharper Points -------------- This same dot-modulating process is used to produce sharper points, most apparent in the serifs of letters. A serif is any short line extending from and at an angle to the ends of a letter's strokes. The artist who designs a typeface usually intends that the end of a serif come to a fine point. At 300 dpi, serif points appear blunt because the dots are too large to fit in the boundaries of the character. With Resolution Enhancement, the dots at the end of the serif are printed at the appropriate percentage to produce a finer point. Line Intersections ------------------ In offset printing, ink sometimes collects on the printing plates where two lines intersect. This pool of ink creates an undesirable thickness when the intersection is printed. The same thing happens in the laser printing process; toner pools at line intersections. Resolution Enhancement recognizes intersection and prints smaller dots in those areas. The smaller dots attract less toner and produce a sharper angle. Resolution Enhancement Settings ------------------------------- The Resolution Enhancement feature on the HP LaserJet III printer can be set to light, medium, or dark, or turned off completely from the printer's front control panel. The settings are necessary to produce the best possible print quality because there is inherent variation among laser printers in the line thickness they produce. The HP LaserJet III printer comes from the factory with Resolution Enhancement set on dark. The printer's self-test printout produces a graphic to help the user determine the optimal setting for his printer. When a third-party gray-scale board is used with the printer, Resolution Enhancement should be turned off. Technical Overview ------------------ Resolution Enhancement technology is implemented with the aid of a patented application-specific integrated circuit (ASIC) which was designed and manufactured by HP. This circuit intercepts the video signal and adjusts the timing and power of the HP LaserJet III printer's laser beam using pulse-width modulation, a method of sending pulses of light to the drum which vary in size. This is possible because the laser beam can be controlled at a faster rate than is required for normal printer operation. Resolution Enhancement produces no speed degradation and requires no software support; information is processed as fast as the video signal passes through the ASIC. The Resolution Enhancement system intercepts and stores a six-dot-high by 2,560-dot-wide row of information at a time. It then looks at each dot in relationship to its 49 closest neighbors. Through a process of pattern recognition, potential problem areas are identified and decisions are made by the ASIC to adjust the placement or size of the dot to create a better curve, line, intersection or point. In short, Resolution Enhancement technology resets the print-quality expectations users have for 300 dpi laser printers. HP's PCL Printer Language ------------------------- Resolution Enhancement focuses on user demands for higher print quality. HP's PCL 5 printer language, used by the HP LaserJet III printer, addresses the next level of user needs: o More fonts in more sizes that are easier to use; o Access to more typeface designs; o Better looking and faster graphics; o More versatile page layouts; o Compatibility with other HP LaserJet printers. A Little PCL History -------------------- HP's PCL printer language grew out of the customer need for software and system compatibility across HP's printer lines. HP's experience in the high-end page-formatting laser-printer market in the late 1970s gave the company a vision for how user needs could be addressed at the low-end with non-impact printers. It also helped HP conclude that it needed a printer language more flexible than the print-and-space languages used by dot-matrix and daisy-wheel printers. HP needed a printer language that could be used across different technologies and implementations -- impact or non-impact, inkjet or laser. It also needed a language that could be extended to meet emerging user needs, such as color and duplex (two-sided) printing, while maintaining compatibility with existing products. At the same time, HP made the decision to focus its developing non-impact printer business on the office printing market. So HP also needed a printer language that provided a price/performance combination acceptable to that market. The answer was HP's PCL printer language. Today, PCL is the native printer language in the HP LaserJet, DeskJet and PaintJet printer families. It is also the language emulated by virtually all competitive laser printers on the market. What PCL Is ----------- The basic concept of PCL is quite simple. PCL is made up of printer control codes and ASCII characters which, when combined, tell the printer to perform some specific function, like "print the next page in landscape, use the line printer font and print six lines per inch." These strings of characters are called escape sequences. The printer recognizes escape sequences as printer commands -- not data to be printed -- because each begins with the ESC character. What makes PCL unique is not that it instructs the printer by this method, but the particular, consistent and optimized way HP writes its escape sequences. Companies offering various levels of HP LaserJet emulation essentially have sought to match PCL escape sequences. (Detailed technical information is available in the HP LaserJet III printer Technical Reference Manual, HP part number 33449-90903. The remainder of this booklet focuses on the features of PCL 5 and the user needs those features address.) Backward Compatibility ---------------------- Before we look at PCL 5 in greater detail, it is appropriate to look at HP's first assumption when developing any new LaserJet printer. Customers need to have their investments in HP LaserJet printers, accessories and the software that supports them protected: A new HP LaserJet printer product must be compatible with the installed LaserJet base. PCL 4, or LaserJet series II compatibility, was the starting point for PCL 5. Code to increase functionality was then added to create PCL 5. Similarly, after the PCL 5 functionality was added, product testing began with compatibility testing. For the HP LaserJet III printer, a battery of LaserJet series II test suites was used to ensure printer compatibility. Then applications testing was conducted with some 20 top software packages, again to establish that software supporting the series II was fully functional on the HP LaserJet III printer. HP font and typeface accessories were subjected to the same sorts of testing procedures to ensure that current HP LaserJet printer users would not lose their investments. All told, PCL 5 code went through more than 7,000 compatibility tests. A current LaserJet printer user can, with confidence, purchase the new HP LaserJet III printer and still use the same software and font products and get the same results. PCL 5 ----- Five major enhancements distinguish PCL 5 in the HP LaserJet III printer from PCL 4 in the HP LaserJet series II printer: o Font scaling; o Vector graphics; o Print direction; o Print model; o Raster compression. Font Scaling ------------ HP LaserJet users want access to more font sizes and more typeface designs. HP is meeting those needs through Intellifont, AGFA Compugraphic's very fast font-scaling technology, and the printer's eight internal scalable typefaces. Intellifont converts a typeface outline to different sizes using an algorithm. Since the fidelity of a character is affected by the scaling process, hints (information provided with the outline of each character) are used by Intellifont to maintain design integrity over the full scaling range. Integrated into PCL 5, Intellifont allows the HP LaserJet III printer to scale its eight internal typefaces, as well as downloaded typefaces and cartridge-based scalable typefaces, on the fly. Scaling range is from one- quarter point to 999.75 points in quarter-point increments. Users will be able to access font scaling from inside their applications as software vendors support PCL 5. Applications which integrate Intellifont will provide HP LaserJet III printer users with exact point-size matching of printer and screen fonts. As an application calls for a particular font, the printer creates and stores it automatically. The result is high-speed printing of high-quality text. The number of fonts that can be downloaded to the printer is limited only by memory. Similarly, the number of fonts the printer can print on a page is limited only by the number available to the printer -- whether resident, downloaded or on a cartridge. For comparison, the HP LaserJet series II is limited to 32 downloadable fonts and can print only 16 fonts on a page. The functional limit for the HP LaserJet III printer is 32,769 fonts. Use of the HP LaserJet III printer's font capabilities has also been simplified by AutoFont Support. AutoFont Support is HP's solution for providing font metrics automatically for both outline and bit-mapped fonts used by LaserJet printers. The benefit to customers using software with AutoFont Support is that new font or typeface products are automatically supported. Each font or typeface product shipped from HP will come with AutoFont Support files. Software developers will include an AutoFont Support reader in their application. The AutoFont Support reader reads the AutoFont Support file and creates the appropriate font driver for use by the application software. Customers using software with an AutoFont Support reader will no longer need a font-driven software update when they add to their typeface libraries. Similarly, since AutoFont Support files are provided with each font or typeface product, the metric code a software developer previously needed to include in software can be eliminated. The software developer only needs to write one AutoFont Support reader per application for all PCL 4 and PCL 5 LaserJet printers. Vector Graphics --------------- PCL 5 also offers users improved graphics performance. The seamless integration of HP-GL/2, a standardization of HP's popular pen plotters, provides HP LaserJet III printer users a significant increase over the HP LaserJet series II in business graphics performance and functionality. Vector graphics is a method of drawing graphics by defining two points in a given field and then drawing a line between them. Efficiency is gained because vector graphics must neither recognize or process every dot or white-space data. Raster graphics, by contrast, draws graphics by sending a bit map to the printing device that includes all black- and white-space data in the image. Incorporation of vector graphics into PCL also provides software developers the tools they need to add features to their applications to let users do such things as print text on any angle, in a circle or in a spiral. Vector graphics also allows picture-frame scaling. Graphics and text can be scaled to a desired percentage or stretched either vertically or horizontally. This feature can be used to create such special effects as oblique fonts or distorted images. The integration of Intellifont and HP-GL/2 into PCL also means the AGFA Compugraphic scalable typefaces are available for text portions of otherwise vector-oriented graphics. No more stick fonts -- and both the text and graphics benefit from Resolution Enhancement. Print Direction --------------- With PCL 5, users can now print text in multiple orientations, such as portrait and landscape on the same page. This new features will be appreciated by the desktop publisher, and spreadsheet and electronic forms user. In addition to multiple orientations on one page, every font available to the printer can be rotated and printed in four different directions -- portrait, landscape, reverse portrait, and reverse landscape. This effectively quadruples the number of available fonts and can conserve PC disk space and printer memory -- only one orientation needs to be stored on disk or downloaded to the printer. Print Model ----------- PCL 5 contains a set of tools for software developers called the print model. These tools can be used by developers to add features to software that will allow users to create more complex pages more quickly and with greater ease. The two basic capabilities in the PCL 5 print model enable users to: o Fill objects with shades of gray or line patterns; o Overlay images in either a transparent or opaque mode. Gray tones and line patterns can be used to fill objects or fonts for special effects. Since these shades and patterns are part of PCL 5 -- not raster information -- printing performance is optimized. A second feature of the print model defines how image combinations can be overlaid. Image components can be printed transparently so the image underneath shows through the top component, or opaquely so the image underneath is obscured or erased by the overlapping image. Special effects such as shadow- and reverse-image printing can be created with this feature. Raster Compression ------------------- Raster data can consume large amounts of disk space and require significant PC processing time. PCL 5's superior vector graphics capabilities do not remove the need for fast processing of raster data from such things as scanned images or bit-mapped images from software applications. Now data can be compressed to conserve disk space and for faster processing through the parallel I/O and then decompressed by the HP LaserJet III. Three different data compression algorithms are employed to allow transmission of the minimum amount of data necessary to reproduce the rasterized image: o TIFF pack bits; o Byte run-length encoding; o Delta row; Improved Performance -------------------- The firmware and hardware systems for the HP LaserJet III printer have been optimized to increase overall printing performance. Text processing is faster largely because Intellifont is so fast. While the printer is rated at 8 pages per minute, that rating is for 5,000 characters per page, compared to 2,500 characters per page for the HP LaserJet series II printer. More of the microprocessor in the LaserJet III printer has been dedicated to the parallel I/O which has resulted in a 46 percent increase in I/O performance. The net result of these system efficiencies is that, once a file is sent to the printer, the PC is available to the user sooner than it would be on a series II. Software Support ---------------- PCL 5 is the fruit of a collaborative effort involving HP and third-party software developers as they sought to address user needs. HP's work with these developers began shortly after the introduction of the HP LaserJet series II. The extended version PCL 4 used by the LaserJet IID and IIP printers resulted from this interactive process. The first HP LaserJet III printer development units were shipped to major software developers in the summer of 1989. In October 1989, HP held a developers conference in Sun Valley, Idaho, and a second wave of printers went out to developers. HP-GL/2 developers were also given the tools to support PCL 5 -- especially its font capabilities - - in their applications. As a result, applications support for the printer is strong and end users can begin exploring the capabilities of the HP LaserJet III printer as soon as they open the box. Right for the Business Office ----------------------------- PCL is to the DOS market what PostScript (R) is to the Macintosh market -- the printer language standard. As the business user becomes more sophisticated, office printing needs are overlapping with those of the desktop publisher -- the office printing and desktop publishing markets are converging. Now, with the HP LaserJet III printer, DOS-based users have easier access to the most commonly used features of PostScript, font scaling and vector graphics. HP Supports Industry Standards ------------------------------ HP recognizes that a certain percentage of its LaserJet customers will always require PostScript. The PostScript printer cartridge for the HP LaserJet IID, IIP and III printers gives them a sharable option which does not require that they buy a second laser printer with resident PostScript. This cartridge option is possible because the formatter architecture used in these printers gives them the capability to accept personality cartridges. Similarly, the Epson FX/IBM Proprinter cartridge offers users with applications written specifically for those printers an upgrade path to LaserJet printing. The day-to-day activities of the business office account for approximately 90 percent of the laser printer market. For users in this environment, the HP LaserJet III printer meets those day-to-day printing needs. Resolution Enhancement technology sets the new print-quality standard for 300 dpi laser printers. PCL 5, with its incorporation of Intellifont font scaling and vector graphics, provides HP LaserJet printer users the capability and performance they need in the 1990s. ------------------------ Adobe and PostScript are registered trademarks of Adobe Systems, Inc. in the U.S.A. and other countries. CG Times and Intellifont are products of Agfa Corporation, AGFA Compugraphic Divison. PCL and Resolution Enhancement are registered trademarks of Hewlett-Packard Company. All other brand and product names are trademarks of their respective companies. Copyright 1989 Hewlett-Packard Company.