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Technical Paper

Auto-Levelling Projector Headlamp System with Rotatable Light Shield

It has often been noted that the fixed position of conventional headlamp beams can present drawbacks. When a car accelerates or decelerates, the angle that the headlamp beam makes with the road surface will change due to vehicle pitching. This beam angle variation can cause a reduction in visibility distance, or alternatively, glare on oncoming vehicles. Both cases represent situations in which safety is impaired during night driving. The headlamp system to be discussed here was developed with a view towards solving this problem. It features a cylindrical light shield which, by rotating in response to sensors, can compensate for vehicle pitching and correct the beam to road angle. Our test results confirm that by using this system, the negative effects of changes in vehicle inclination, including glare on oncoming vehicles and reduced road illumination distance, can be all but eliminated.
Technical Paper

Beam Controllable Headlighting System

These headlighting systems control the headlamp beams according to the running state of a vehicle at night in order to provide optimal illumination. They have two functions: to control the range of illumination according to vehicle speed and to control beam direction in response to the steering. Two optical systems were developed to realize these functions. One system uses two movable mirrors in each headlamp, while the other system uses a movable lens installed in front of the projector lamp. According to photometric data analysis done in our laboratory, bath systems improve visibility on curved roads substantially. It was also found that they are effective in limiting glare projected onto oncoming vehicles.
Technical Paper

Development of Controlled Surface Reflector for Headlamps

This report describes the development of an advanced technology headlamp reflector which is capable of producing a sharp cut-off line. Similar attempts in the past have suffered from various drawbacks, but through the use of a mathematically derived set of equations describing a controlled curved surface, we were able to greatly increase performance specifications. Prototype headlamp tests showed improved distant visibility, a major problem in existing designs. Furthermore, by superimposing a ripple pattern onto the reflector surface, we were able to attain sufficient light diffusion to enable the reflector to be used within headlamps having highly slanted outer lenses.
Technical Paper

Development of New Forward Lighting Systems with Controllable Beams

In recent years, traffic fatalities in Japan have consistently numbered in excess of 10,000, making them a serious social issue. Among these deaths resulting from traffic accidents, fatal accidents occurring at night outnumber daytime fatalities by three to one; when conditions are rainy, this figure increases to ten to one. These facts point to the importance of the role of automobile forward lighting systems. In order to provide enhanced nighttime safety measures, we have been working since 1990 on the development of a headlamp system that can control and adjust the headlamp beam in response to driving conditions. In this report, we will outline the general features, functions and lighting performance of forward lighting systems, focusing on this newly developed headlamp system.
Technical Paper

Development of Smoothly Curved Fresnel Lens

This thesis gives a detailed report on the development of the curved Fresnel lens making it possible to control luminous flux in a smoothly curved configuration.
Technical Paper

LED Headlamp Development for Mass Production

To meet the market requirement for headlamps having lower power consumption, high photometric performance and long life whilst providing new styling opportunities, it has been anticipated that LED light sources would provide the necessary technological basis. Against this backdrop, Koito has succeeded in developing the necessary headlamp technologies and commercializing the world's first headlamp utilizing white LED's. The key point is that the various challenges associated with the development of an LED headlamp such as the commercial application of a synthesized light distribution, control of the light axis structure for the multi-lamp system, development of adequate thermal management for the cooling of the LED's and the achievement of volume production of the lamps have been successfully overcome.
Technical Paper

Motorcycle Headlamp Banking Angle Controlling Device

The motorcycle banks at an angle in order to maintain an adequate balance between the motorcycle and centrifugal force when it turns. This results in the following problems: 1) The motorcycle rider's visibility is reduced due to insufficient forward illumination. 2) Glare is projected onto oncoming drivers. This thesis is a report on the development of a device designed to prevent the above-mentioned problems so that the rider may drive his motorcycle safely at night.
Technical Paper

New Optical System for Low Profile Headlamps

The demand for headlamps with low profile and slant lens has been increasing in such a vehicle styling trend that it has been getting more and more aerodynamic to reduce air resistance and thereby to improve fuel consumption and driving performance. Lamp manufacturers, in answer to the demand, have tried to develop various types of new optical headlamp systems. We, Koito Manufacturing Co., Ltd., have been also studying and developing our own low profile headlamps and now we have found a new optical system which can be applied to such a severe condition of 65 mm in height and 45° of the outer lens slant. Here we report the details of the development.
Technical Paper

Optical System for Illuminating the Lateral Section of Wraparound Lamps

With the increased use of wraparound lamps in automotive design, the problem of how to illuminate the lateral section which is blocked from the light source by the chassis has become a point of concern. This report describes the development of an optical system which makes use of a photoconductive panel in order to resolve this problem.
Technical Paper

Steerable Forward Lighting System

This is a report on the development of a lamp system that will change the extent of the illuminated area in response to the steering angle. The optical performance of headlamp systems has been improved in response to increases in automobile performance and changes in traffic conditions. However, most of a driver's perception at night is visual so it is necessary to improve the driver's forward visibility at night in accordance with the increased performance of automobiles. The light distribution of current headlamps is designed mainly in consideration of straight forward vehicle movement so the area that a driver wants to see when making a turn is not necessarily sufficiently illuminated. In order to provide sufficient illumination for safe cornering, a headlamp system that changes the distribution of light in response to the steering angle with the use of microcomputer control has been developed.
Technical Paper

The Development of Infrared Projector

A driver's night view assistance system has been put into practical use. The night view assistance system helps drivers to see farther down the road than low beam headlamps by illuminating the road scene with an infrared projector. We have developed an infrared projector by using a projector type headlamp. Infrared is produced by shielding visible light at a multiple-layer film of Silicon (Si) and Silicon Dioxide (SiO2) which is deposited alternately on a condenser lens surface. The principle of the multiple-layer film and the infrared projector's structure are reported in this paper.
Technical Paper

Thermal Air Flow Analysis of an Automotive Headlamp - The PIV Measurement and the CFD Simulation by Using a Skeleton Model

Heat transfer evaluation and air flow field prediction are important for improving the heatproof capability, durability and ventilation performance of automotive headlamps. In the present study, heat transfer and air flow field in a headlamp model were investigated both experimentally and numerically. The Particle Image Velocimetry (PIV) was employed to measure the velocity field of the heat transfer loop in the headlamp at first. Then, Computational Fluid Dynamics (CFD) simulations were conducted by using the PIV measurement results as boundary conditions for the CFD simulation.