Fundamentals & Background Knowledge
Light simulation is based on the physical principles of geometrical optics and enables precise analysis of the propagation, distribution, and interactions of light within optical systems. The following section explains the key terms and methods that form the foundation of modern light simulation.
Ray Tracing
Ray tracing is the core method in light simulation. Light rays are traced from a source through an optical system. When a ray encounters an interface, it is reflected, refracted, or scattered according to the optical properties of the material. The method provides an intuitive and realistic representation of luminous flux distribution within optical systems, enabling efficient planning and optimization before any physical prototype is manufactured.
Non-Sequential Rays (NS-Rays)
In this method, the starting point and direction of a light ray are explicitly defined in order to analyze the path of individual rays through the system. This form of ray tracing is primarily used to verify and optimize specific geometries — for example, during the development of light guides or reflectors.
Monte Carlo Rays
The Monte Carlo method is based on randomly generated rays simulated in large numbers, producing a statistically robust and realistic representation of the overall luminous flux distribution. This approach is used primarily for complex optical systems involving large numbers of rays, in order to create a high-fidelity representation of real-world behavior.
Physical Principles of Light Propagation
The propagation of light follows the laws of reflection, refraction, absorption, and scattering. These physical relationships form the basis of every light simulation and fundamentally determine how efficiently light is utilized and distributed within a system.
Light Source
The light source is the starting point of the simulation. It can represent natural radiation (e.g., sunlight) or artificial illumination (e.g., LED, laser). Key parameters include luminous intensity, emission characteristics, spectrum, and geometry. Various light source types are modeled in simulation — including point sources, area sources, and volume sources.
Light Guide
Light guides direct light from the source to the receiver. They operate on the principle of total internal reflection (TIR), whereby light is guided within the material without escaping it. Light guides may be made from glass, plastic, or flexible fibers. Their geometry and surface structures (e.g., light extraction features) are the primary determinants of the efficiency and uniformity of luminous flux distribution.
Receiver (Detector)
The receiver (or detector) is the surface or plane on which light ultimately arrives and at which the luminous flux distribution is to be evaluated. In the simulation, it is used to determine quantities such as illuminance, luminous intensity, or luminance. The receiver does not influence the ray path within the simulation; it solely captures the results. With appropriate settings, it can evaluate luminous flux distribution from various viewing positions.
Reflection
Reflection describes the redirection of light at an interface between two media. The angle of incidence equals the angle of reflection. Reflection is a fundamental phenomenon in the design of mirrors, reflectors, and optical displays.
Refraction
When a light ray enters a medium with a different refractive index, it changes direction in accordance with Snell’s Law. This effect is decisive for the function of lenses and transparent materials used in optical systems, as it is governed by their specific surface geometry.
Total Internal Reflection (TIR)
When light travels through a medium with a higher refractive index and strikes an interface with a lower refractive index, it can be completely reflected at a specific angle. This total internal reflection enables efficient light guidance, for example in optical fibers and light guides.
Absorption
Absorption describes the process by which light energy is absorbed by a material and converted into heat or other forms of energy. In the simulation, this effect supports the analysis of energy-efficient materials and coatings, but can also be used deliberately as a baffle — for example for accent or symbol lighting.
Scattering
Scattering occurs when light strikes rough or microstructured surfaces. It produces diffuse light distribution and is deliberately applied to achieve uniform illumination or specific optical effects.
Luminous Flux (Φ)
Luminous flux is measured in lumens (lm) and describes the total light output emitted by a light source.
Luminous Intensity (I)
Luminous intensity is measured in candela (cd) and describes how much luminous flux is emitted within a defined solid angle.
Illuminance (E)
Illuminance is measured in lux (lx) and describes the amount of light striking a specific surface area. It is a key parameter for evaluating brightness on work surfaces or displays.
Luminance (L)
Luminance, measured in candela per square metre (cd/m²) – also commonly expressed as nits (1 nit = 1 cd/m²) – describes the brightness of a luminous or reflecting surface in a specific direction, as perceived by the human eye.
Luminous Homogeneity
Luminous homogeneity describes the evenness of luminous flux distribution. A uniform color distribution indicates homogeneous illumination, while high contrast values point to uneven illumination. This parameter is especially important for light guides or display surfaces that require a defined level of homogeneity or consistent luminance distribution.
Ray Path
The ray path shows how light rays are guided through an optical system. Simulation makes it possible to visualize interactions with interfaces, media, and materials — forming the basis for the optimization of lighting systems.
