Reflection means that electromagnetic radiation is deflected and sent back either at the boundary between two media (surface reflection) or inside a medium (volume reflection).
With light control via reflectors, only the light rays emitted to the side are controlled. This usually creates wide light beams. In addition, there is the risk of high losses due to spill light (see figure, red lines) or also imaging errors such as light circles. Unfocused and sometimes colored edges to the light beams may also be possible, as well as a non-uniform distribution of illumination in the center.
Lens systems, on the other hand, which have been developed according to the principle of projection, are characterized by precision, efficiency and high uniformity in brightness as well as color consistency. All light rays are directed through the lens system, which means that neither imperfections nor spill light losses occur. Even very narrow light beams for striking accents can be implemented.