Metal sintering layer-by-layer with DLP As of current technological advancements, there exists Metal 3D printers that make use of Digital Light Processing (DLP) projector to 3D print metal objects. These printers use a mixture of metal powder and binder. The mixture is placed on the build platform and a laser light beam (or UV light beam, I'm not sure) projection of the layer to be printed is projected on top of the mixture. The light causes the binder to bind the metal powders to each other creating the desired layer. Similar process is repeated for subsequent layers until the object is fully printed. Once fully printed the object is de-binded and sintered in an oven to form the final object.
Now, my question is, like in SLS 3D printing, why cant we directly shoot high-power laser beams with the help of DLP projector onto the powder (without the binder) and cause the metal powder to sinter there itself?
SLS uses a high powered laser to smelt the binder of a ceramic or the metal itself. We are talking about at least a 40 W laser which focuses its power on a circle of about 50 µm. How much power are we talking about with that lowest viable laser for plastic SLS?

$\frac{40\ \text{W}}{\pi \ 62.5\times 10^-9\ \text{m}^2}=640\times 10^6 \frac{\text{W}}{\text{m}²}$

A typical SLA/DLP machine like the Sparkmaker runs on 48 W in total. Assuming that's 40 W for their $55\text{ mm}\times98\text{ mm}=0,00539\text{ m}^2$, so the total projector power of the Sparkmaker is

$\frac{40\ \text{W}}{\pi \ 0,00539\ \text{m}^2}=7.421\times 10^3 \frac{\text{W}}{\text{m}²}$

That's about 5 orders of magnitude too little to smelt a layer in the same time. To get a DLP-like projector doing SLS work, you'd need a light source that runs at about a similar power per square meter - wich would just melt the moment it turns on.