KEYWORDS: Near field optics, Light emitting diodes, Geometrical optics, Light sources, Near field, Modeling, Data modeling, Optical design, Optical spheres, Ray tracing
Tailoring of secondary optics, especially in short distances to the light source, requires appropriate,
point source based, primary optic models which provide adequate accuracy. We propose a method to
generate such models for complex, even non-smooth, primary optics by using spatial radiation patterns
and applying backward tailoring. Furthermore, we demonstrate the scope of this method and the
improvements on the secondary optic design process.
Light guide rods based on multiple total internal reflections provide some powerful design opportunities. Therefore, they
are very suitable for producing arbitrary light distributions. Especially for LEDs they work highly efficient due to the use
of the whole emitted light flux and the theoretical lossless light propagation by total internal reflection. Frequent
applications are color mixing and the creation of a homogeneous luminance distribution at the output surface. However,
the capabilities of common light guide rods are under-utilized. Therefore, we demonstrate a new design approach that enhances the performance of light guiding systems and is applicable to illumination problems.
We propose an easy-to-handle method of surface parameterization which is valuable for enhancing the illumination
design process. Therefore, an additional normal vector function is provided defining the desired direction of the virtual
normal vector at each point of the surface. Hence, the reflection/refraction properties are seperated from the shape of the
surface. These surfaces are named Virtually Reflecting/Refracting Surfaces (VRS). This type of surface provides the
opportunity to alter the normal direction without changing the shape of the surface and vice versa. Therefore, the
designer can have a selective look at those quantities depending mainly on position or on direction. This means that, e.g.,
one can first prescribe the geometrical shape and adjust the surface's optical properties afterwards. Moreover, structured
surfaces, e.g., segmented reflectors, can be replaced in between by virtually reflecting surfaces in order to eliminate
discontinuities. This is apparently expedient for improving the convergence in automatic design. We investigate optical
layouts with VRS to demonstrate their impact on the design and the optimization process.
High-Power-LEDs have reached a development stage that affords their reasonable application to general illumination.
Nonimaging total internal reflection optics (TIR optics) that generate non-rotationally symmetric light distributions are
proper components to preserve the advantages associated with this type of light source. Thus, high efficiency has to be
reconciled, e.g., with the use of freeform surfaces. This contribution investigates the development of TIR optics for LED-based
illumination applications. First, we consider rotationally symmetric TIR optics in order to illustrate their functional
principle and demonstrate some special design criteria. Second, we apply them to non-rotationally cases using the
tailoring technique. Finally, we illustrate various aspects of the design process with selected examples.
The automotive lighting technology is in considerable progress due to new components, e.g., High-Power-LEDs and
light guides, and new sophisticated production techniques. Furthermore, great importance is being attached to the
appearance of front and tail lamps. White High-Power-LEDs have reached a development stage that affords its
reasonable application to low beam headlamps. This challenging illumination function requires sophisticated design
techniques in order to preserve the advantages associated with this source type. Thus, high efficiency and stylish
appearance have to be reconciled, e.g., with the use of freeform surfaces. Beside the demands from manufacturers and
customers, car lamps have to meet several regulations (ECE, SAE, etc.). This contribution describes the illumination
design of a LED-based low beam headlamp using advanced mathematical methods, e.g., 3D-Tailoring, automatic
optimization, and Virtually Reflecting/Refracting Surfaces (VRS). We propose this new surface type with non
conventional reflection/refraction properties as an advantageous design tool for the first layout and for automatic
optimization, as well. For efficiency reasons, special attention will be paid to the creation of the cut-off line without
using additional stops.
The application of ultra bright monochromatic and white High-Power-LEDs in the range of automotive lighting systems
is now state of the art. These LEDs offer new possibilities in optical design and engineering within different fields of
automotive lighting, e.g., tail lamps, signal lamps, headlamps and interior lighting.
This contribution describes the process of the optical design of an automotive LED tail lamp based on a practical
example. We will elaborate the principal geometric approach, the radiometric conditions and the optical design by using
standard and advanced mathematical optimization methods. Special attention will be paid to the following topics:
efficient light coupling from the LED into the optical device, adaptation of the illuminance and optimization with respect
to the requirements from SAE/ECE regulations.
It will be shown that the development of LED-lamps requires the complex interaction of several factors. The challenge
for the optical designer is to fulfill the technical demands while also considering the appearance of the final product
desired by the customer. Further design specifications emerge from the electrical and thermal layout of the lamp.
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