Method and apparatus for forming a three-dimensional article by fusion of a powdered medium in a powder bed

A powder bed fusion apparatus, comprising:

• means for distributing respective layers of a powdered medium over a powder bed;
• means for heating a current one of said respective layers of the powdered medium distributed over said powder bed to a temperature below a melting point of the powdered medium;
• means for projecting respective images of respective cross-sectional layers of an object on the current one of the respective layers of the powdered medium distributed over said powder bed, a respective projected image of a respective cross-sectional layer being created by a first liquid crystal on silicon (LCoS) panel, of the means for projecting, spatially modulating a first laser beam and projection of a resulting spatially light modulated laser beam through a first optical path onto said current one of the respective layers of the powdered medium so as to form a fused portion of the current one of the respective layers of the powdered medium in locations in the powder bed having a shape corresponding to said respective image of the respective cross-sectional layer of the object;
• a control system coupled to the means for distributing, means for heating, and means for projecting, said control system including a processor and a memory coupled to the processor, the memory storing instructions, which instructions when executed by the processor cause the processor to, for each respective cross-sectional layer of the object:
• cause the means for distributing to distribute, one at a time, said respective layers of the powdered medium over the powder bed, each successive respective layer of the powdered medium being distributed over a previously distributed one of the respective layers of the powdered medium,
• cause the means for heating to heat the current one of the respective layers of the powdered medium distributed over said powder bed to the temperature below the melting point of the powdered medium, and
• cause the means for projecting to project the respective image of the respective cross-sectional layer of the object being fabricated onto the current one of the respective layers of the powdered medium then-distributed over said powder bed by spatial light modulation of the first laser beam and to project second respective images of each respective cross-sectional layer of the object on respective layers of the powdered medium distributed over said powder bed, wherein the second respective projected images of the respective cross-sectional layers are created by directing a second laser beam through a second optical path, which comprises one or more of a second LCoS panel, a digital micromirror device, diffractive optics, and a mirror galvanometer, and projection of a resulting laser beam onto said respective layers of the powdered medium, wherein the first and second laser beams are formed from a common laser beam using a polarizing beam splitter and wherein the first LCoS panel is configured to receive the first laser beam from the polarizing beam splitter.