Target simulators are image projectors that project a real optical image of simulated targets (mostly airborne/space targets).

In contrast to to typical test systems that project images of static simple shape artificial targets, the target simulators project images  that resemble real targets (typically airborne targets).

Computer simulators are computer programs that simulate an electro-optical imaging system (typically thermal imager) by generating on computer screen images similar to images generated by simulated real EO imager.