Real-time liquid metal droplet analyzer with spatial modulation in additive manufacturing

A method of sensing characteristics of a stream of jetted material in a 3D printer, the method comprising:

• ejecting molten droplets along a jetting path from an ejector to a build platform;
• sensing light emanating from the molten droplets to generate an electrical signal corresponding to the light;
• encoding information in the light using an optical mask positioned adjacent to the jetting path, wherein the optical mask comprises a plurality of regions comprising light-blocking regions and light-passing regions configured to modulate the electrical signal as the molten droplets travel along the jetting path;
• and
• controlling the 3D printer based on the electrical signal.

An optical mask for a 3D printer, comprising:

• a first light transmissive region configured to pass infrared light at a first spectral range;
• a second light transmissive region configured to pass infrared light at a second spectral range different from the first spectral range;
• and
• a frame that holds the first light transmissive region and the second light transmissive region together, wherein the frame is configured to mate with a connector of a 3D printer to position the optical mask adjacent to a jetting path of a stream of molten droplets.