SLA holds the historical distinction of being the world’s first 3D printing technology. Stereolithography was invented by Chuck Hull in 1986, who filed a patent on the technology and founded the company 3D Systems to commercialize it.
An SLA printer uses mirrors, known as galvanometers or galvos, with one positioned on the X-axis and another on the Y-axis. These galvos rapidly aim a laser beam across a vat of resin, selectively curing and solidifying a cross-section of the object inside this build area, building it up layer by layer.
Most SLA printers use a solid state laser to cure parts. The disadvantage to these types of 3D printing technology using a point laser is that it can take longer to trace the cross-section of an object when compared to DLP.