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Publication Number: FHWA-HRT-04-144
Date: December 2005
Enhanced Night Visibility Series, Volume XIII: Phase III—Study 1: Comparison of Near Infrared, Far Infrared, High Intensity Discharge, and Halogen Headlamps on Object Detection in Nighttime Clear Weather
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During Phase II of the Enhanced Nighttime Visibility (ENV) project, far infrared (FIR) systems showed promise for pedestrian-detection capabilities (ENV Volume III). These systems, which show warm-bodied objects as light silhouettes on a dark background, have been received with interest in the marketplace. FIR technology is present on production vehicles and remains a unique vision enhancement system because of its ability to present images based on the temperature differential between an object and its background. The images presented by FIR do not contain many details; for example, they do not show headlamp light, pavement markings, signs, or raised retroreflective pavement markers (RRPMs). Despite this lack of detail, FIR has been shown to potentially allow for the early detection of pedestrians, cyclists, or animals (i.e., objects generating heat) on the roadway.
Near infrared (NIR) systems have also gained interest from original equipment manufacturers (OEMs) and suppliers for possible future product offerings. NIR systems, which present features of the forward road scene with more picture-like quality, are a more recent addition to automotive-based vision enhancement systems (VESs). These systems use infrared (IR) emitters to act like IR headlamps when viewed through the IR camera and its associated display. Unlike FIR, NIR systems show many details of the forward roadway scene, including headlamp light, pavement markings, signs, and RRPMs. NIR success in maintaining a clear image in the presence of retroreflective objects and headlamps is negatively affected by bright halos, or “blooming.” This area is currently being refined by system designers, with development of different methods to actively control blooming. While blooming of lights and retroreflective objects is an issue with NIR, these systems nevertheless have the potential to increase the visible distance ahead of the vehicle (when it is viewed through the in-vehicle displays) without blinding oncoming drivers.
This portion of the ENV project compared conventional tungsten-halogen (halogen), high intensity discharge (HID), and NIR and FIR night vision enhancement systems in a set of object detection scenarios. The VESs tested included the following configurations: two NIR systems (NIR 1 and NIR 2), two HID systems (HID 1 and HID 2), one FIR system, and one halogen system (HLB). Each of the systems was tested on a sport utility vehicle (SUV). The HLB headlamps tested are currently available on the market; therefore, they served as a baseline condition, allowing a comparison between readily available technologies and more advanced VES alternatives.
Discussion about the performance of HIDs has often involved discussion of the breadth of the beam pattern and performance in roadway curves. The two HID systems used in this study were selected to provide two different HID beam patterns: one with a shorter, wider pattern (HID 2) and one with a longer, narrower pattern (HID 1). The HID systems also provide a point of comparison between currently fielded technologies and the more advanced VESs. For more information on the headlamps, see the detailed technical specifications of each headlamp in ENV Volume XVII, Characterization of Experimental Vision Enhancement Systems.
Interest in this research also originated, in part, from the increasing number of IR systems on production vehicles. As more and more of these vehicle-based IR systems are introduced into the larger transportation system, it has become important to develop an understanding of the interactions between these systems, their users, other drivers, and the established components of the roadway system, including signage, roadway geometry, and roadway markers. With an infrastructure that has been carefully designed for specifics such as sight distances, visibility levels, and lighting methods, it is important to actively monitor and plan for the introduction of these new vision enhancement technologies. The experimental goal of this research was to investigate the performance of new VESs and develop an understanding of their interaction with the larger transportation system.
The IR systems tested in this phase of the research were provided by automotive manufacturers as well as suppliers of IR vision systems. The manufacturers and suppliers provided the contractor with the prototype systems installed on vehicles and the descriptive information about the specific implementation tested, such as IR emitter types and field of view. To protect proprietary characteristics of the systems, additional details beyond those the manufacturers and suppliers provided were not recorded. The headlamp systems tested were production headlamps purchased by the contractor.