Projection (optic): directing light via lenses

Projection is the transfer of an image by means of an optic onto a surface. In architectural lighting, the light from a point light source, usually an LED, is directed via lenses onto the target surface. The light is scattered or focused, depending on the shape of the lens. High quality lens systems are precisely matched to the light source and thus able to direct the light with precision onto the target surface. The result is effective photometric systems that achieve high illuminance (lx) with low connected load (W).

How does projection work?

Multi-level lens systems are suitable for uniformly transmitting the light of an LED. First, the light emitted by the LED is focused by a lens. This so-called collimator generates light with an almost parallel beam path. The light rays now hit a second lens, the shape of which determines the actual light distribution of the luminaire. Lens systems feature high precision and efficiency. High uniformity in terms of brightness and colour constancy is generated within the light beam. Imperfections or spill light losses are avoided because all light rays are guided through the lens system.

What projection effects are possible?

The imaging optic of contour spotlights enables sharp edges of light beams when projected. Shifting the lens regulates the sharpness of the edge of the light beam, to e.g. gain a high-contrast differentiation from the surroundings. An additional framing attachment can be used to illuminate pictures with sharp edges so that works of art appear to glow from within.

What is the difference between reflection and projection?

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 coloured edges to the light beams may also be possible, as well as a non-uniform distribution of illumination in the centre.

Lens systems, on the other hand, which have been developed according to the principle of projection, are characterised by precision, efficiency and high uniformity in brightness as well as colour 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.