Lens for focusing electromagnetic radiation in forming layers in three-dimensional rapid prototyping includes a heating element in the exit window

摘要

A lens assembly for focussing a beam of electromagnetic radiation used in solidifying a reactive layer, has a heating element (16) built into the mounting (14) of the exit lens (15). The heater can be in the form of windings or can be a printed film in metal or graphite. Leads are taken to the outside and the mounting can include a temperature sensor. Alternatively the temperature can be deduced from measurement of the heater current. An independent claim is included for the process of building up a three-dimensional object in layers by radiation using a lens with a heated exit window. The temperature of the window is controlled and additionally a gas can be blown against the lens.