Unless I'm misreading it looks like the light isn't the correct wavelength, or possibly concentration, to cure the resin except for at the focal point. I'm not

Unless I'm misreading it looks like the light isn't the correct wavelength, or possibly concentration, to cure the resin except for at the focal point. I'm not sure exactly how they're doing it but picture the adjustable lens of a flashlight, that lets you move the focal point (the point at which the beam crosses over itself). The resin would only cure where that crossover happens. I'm not sure if that's exactly what's going on but from the article that's what it seems to be.