Fuji Xerox has been offering various features and a wide range of systems to increase efficiency in printing processes. It has developed a technology to directly print 2,400 dpi 1-bit TIFFNote1 data that is commonly used in print workflows, and introduced that technology in the DocuColor 1450 GA/PX140 Print Server (Fig. 1) released in January 2011.
While the prepress processes of offset printing are becoming fully digitalized, 1-bit TIFF data is still commonly used in the print workflow as the output data of prepress processes. When xerography printers can directly print 2,400 dpi 1-bit TIFF data, there is a great advantage of checking moiré patterns more efficiently, as images and halftone dots for CTPNote2 can be output at low cost and in short time with image quality equivalent to that in offset printing.
To realize the direct printing of 1-bit Tiff data, Fuji Xerox has been developing the technologies described below.
Fig. 1: DocuColor 1450 GA/PX140 Print Server
As shown in red in Fig. 2, introducing the new image processing circuit that transfers 2,400 dpi 1-bit data directly to VCSEL ROSNote3 and high-speed high-bandwidth interface technology solved the issue of extremely slow data processing speed due to data that is twice the size of data used in the conventional path. Optimizing the amount of light exposed by VCSEL ROS thus reduced the variance in density that occurs when outputting 2,400 dpi 1-bit data.
Fig. 2: New Image Processing Circuit in DocuColor 1450 GA
VCSEL developed by Fuji Xerox is the key technology that enables the writing of images in 2,400 dpi resolution. It enables the control of two-dimensional multiple beams in one scan. Introducing VCSEL ROS that enables the writing of images in 2,400 dpi output resolution and optimizing the number of beams in one scan in the DocuColor 1450 GA reduced the streaks that occur at the boundaries of scanning beams. By adopting voltage driving technology for the light-waveform response and current driving technology for light-power stability, Fuji Xerox successfully achieved both high speed drive and a stable light power waveform.
To reproduce print images with high fidelity and reproduce tone at image quality equivalent to that in offset printing upon using xerography printers, tone reproduction curve characteristics were improved to a level equivalent to that in offset printing by correcting the amount of light exposed by VCSEL ROS (Fig. 3). As a result, the reproducibility of dots has been improved and that of moiré patterns now approaches the level in offset printing. As the reproducibility of 2,400 dpi RIP images and the aforementioned dots has been improved, the reproduction of text has also been improved.
Fig. 3: Tone Correction for Offset Printing / Xerography
In order to reproduce moiré patterns accurately, the cyclic variance in density and nonuniform partial density unique to printers must be avoided. Therefore, the new thicker aluminum-based photoreceptor was introduced to enhance stiffness and reduce vibration upon rotation. Moreover, gear accuracy and pitch were also optimized to reduce vibration and variable speed in the driving mechanism. This led to achieving high image quality that offers the high fidelity reproduction of images.
By combining the above technologies, Fuji Xerox succeeded in realizing the direct printing of 2,400 dpi 1-bit TIFF data that is commonly used in print workflows.