Architecture of A High Performance LED Printhead Platform

Abstract

Océ's continuous feed printer families are developed to satisfy the ever increasing speed and quality requirements of our customers. One of the key components for higher performance in electrophotographic printing is the exposure system. Océ develops and manufactures LED printheads since many years because of their high reliability and durability. A third generation printhead platform was developed to meet highest speed and quality requirements while lowering overall cost. This was achieved by a combination of mechanical, optical, and electronical improvements.For the mechanical part, customization of a general-purpose pick-and-place system ensured a three-sigma LED-to-LED placement accuracy of less than two microns.The selection of a very uniform SelfocTM lens array with high aperture but low depth of focus forced a mechanical design with minimized tolerances between LED and photoconductor surface in order to achieve optimum print resolution.LED drivers were implemented in full custom mixed-signal CMOS technology with .35 micron design rules. An on-chip bus for data, clock, status, and control signals makes the array length scalable to arbitrary print width with minimal changes to parts. The sustained data throughput of the driver chain comes close to 2 gigabits per second. Various power and timing control settings can be configured via bus commands. Each chip autonomously performs redundancy checks to alert the controller in case of data integrity errors. Non-uniformities of light output are compensated for by individual energy calibration for each dot. Bi-level, four-level, and sixteen-level exposure modes are available. All exposure functions are controlled digitally to achieve highest precision and reliability.Thermal management utilizes a massive heat sink onto which the heat-dissipating elements are directly bonded, and a liquid cooling system to provide for uniform temperature inside each individual print head and across all print heads of a printing system.