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Technical Paper

Usage of High Flux White LEDs for DRL and Front Turn Signal Lighting

Currently, high flux white LEDs are being studied extensively for forward lighting applications. Because of their light output levels that are reaching new highs at an impressive rate, these devices can also be considered for signal lighting applications by means of color filtering. In this paper, we will present results from studies of high efficiency collectors with these types of LEDs for use in Front Turn Signal Lamp (FTSL) and Daytime Running Lamp (DRL) applications. Comparison of package size vs. collection efficiency for various configurations will be discussed. We will also review LED color temperature vs. amber color filters, and its effect on system optical efficiency.
Technical Paper

The Design of a Visual Aim Low Beam Head Lamp with a High Intensity Discharge Source

This paper discusses methodologies for the optical design of a High Intensity Discharge (HID) light source reflector optic low beam head lamp which meets visual optical aim (VOA) requirements. Methods of optimizing the gradient of the sharp cut-off required for visual aiming are presented. A merit function with conditional equations is introduced to optimize the design to maximize the gradient, maximize the hot spot, and control glare light. Design results are shown both before and after the design has been optimized.
Technical Paper

Study of Tubular Volume Light Source Intensity Distribution

Neon light sources offer unique challenges to the optical design of automotive lighting. When the tubular neon light source was first introduced, its luminous intensity distribution was assumed to be the same as other tubular sources, such as fluorescent tubes. However, upon investigation and analysis of measured data it became apparent that unlike fluorescents, neon tubes, as a volume source, provide a unique luminous intensity distribution instead of the familiar Lambertian distribution. This paper will develop an optical model for a tubular volume light source (neon tube), and further results will identify the effects of other optical elements, such as fluted lensing.
Technical Paper

Studies for Headlamp Optical Design Using LEDs

The studies for headlamp optical design using current available and future projected white LEDs have been conducted. With desires of high performance and compact packaging sizes for both high and low beam headlamps, using LED light sources is a great challenge for the headlamp design optical engineers for light collecting efficiency, beam pattern compression and optical accuracy. Although total lumen flux produced by the LEDs may be comparable to the exiting light sources, e.g., incandescent bulbs, the optical and mechanical characteristics of LEDs may limit the headlamp applications. The paper identifies the etendue concerns and limitations for automotive headlamps when using LED light sources. It provides a guideline for considerations of using LEDs for automotive headlamp applications.
Technical Paper

Optical Transform Limitations in Headlamp Photometric Performance

Automotive lamps are essentially the optical transform devices. A light intensity angular distribution from a given light source (filament, HID arc, LED, etc.) is transformed to a desired new light intensity angular distribution namely beam pattern by means of an optical system such as a reflector or lens optics, or a projector module system. There are fundamentally five types of optical transformations occurring in a headlamp optical design: A). Light intensity angular distribution transforms from a light source to a beam pattern that is another fashion of angular distribution via a reflector-optics device. This transform device, sometimes, is referred to as the free-form reflector design; B). Light intensity angular distribution from a light source is transformed to a spatial distribution on a focal plane of an ellipsoidal (or similar) reflector; C).
Technical Paper

LED Flux Measurement Methods for Automotive Lighting

Currently, there is still no standardized method to measure LED flux in automotive lighting. Usually, LED manufacturers provide a lumen range (or bin) for a given type of LED. However, with the increased usage of high-flux LEDs, the need for an absolute lumen value is becoming important for optical design of automotive lamps. The knowledge of an LED lumen value is necessary for more precise lamp designs. Three different types of measurements for LED flux were compared. These three measurement methods are: 1). 2π flux integrating sphere; 2). 4π flux integrating sphere; and 3). Goniometer. In this paper, we will discuss the results from these three methods, and conclude with recommendations on the preferred methods and parameters critical for accurate LED flux measurements.
Technical Paper

Design of Reflector Optics for Visually Aimable Lowbeam Head Lamps

This paper discusses the optical design of motor vehicle head lamps using the new federal visual optical aim requirements. Methodology for using filament images from a head lamp reflector to create the required sharp gradient for visual aimable lamps is presented. The paper discusses hardware tolerance factors which would degrade a sharp cut-off, and methods are reviewed for accounting for and designing robustness against the tolerance factors. Hardware results are shown for designs using the techniques described in the paper.