Test Set-Up

164 analysis and optimization of light distributions

and especially the lighting systems in use, shortly introduce the measurement equipment for illuminance andGPS-data before going into further detail for the eye tracking set up. This will include the eye tracking setup it self, the calibration routine and the achievable results for accuracy. The camera system and object recognition software used for this study is already described in section5.2.

test-vehicle and test-equipment

Since this study focuses not only on objective and independent variables like traffic density and object position, but focuses on the driver’s traffic perception through gaze monitoring and the combination of this with the mentioned objective measurements, the influence of the test vehicle is not to be neglected. Therefore, the following sections will focus on the vehicle setup, the lighting parameters and the smaller measurement equipment.

vehicle and lighting parameters

The vehicle in use is a BMW 3-Series from 2016 equipped with a full ^LED headlamps. To minimize the influence of different light distributions, the headlamps are without any AFS

functionality. The high beam is set to manual, so that the driver needs to decide at what point the use of high beam is necessary and useful. The measured light distribution for low beam is shown in 5.66 for a single headlamp. The light distribution for the low and the beam is found in appendixE.1in figureE.1.

−²⁰ −^{10 0 10 20}

−⁵ 0 5

Horizontal Angle in Degree VerticalAngle inDegree

Figure5.66– Light distribution for low and high beam for the BMWLEDheadlamps used for the study. The colour map indicates the recorded luminous intensity under all angles.

The test vehicle is setup with a navigation system in the centre console and a head up display. For daytime driving, the brightness settings for all interior and armature is set to maximum to allow all participants to safely read and identify any system or navigational messages. For nighttime drives, all settings are set to minimum to minimize additional, dis-turbing light for the participants. An interior view of the vehicle is shown in figure5.67.

5.4 optimizing parameters for light distributions on real roads 165

Figure5.67– Interior of the test vehicle with the eye tracking cameras marked by the red circles, the infra-red light sources by green circles, the stereo (scenic) camera by yellow circles and the position of the illuminance sensor by the blue circle. TheGPSsensor is located on the roof of the vehicle and therefore not present in this image.

Red circles mark the eye tracking cameras, green circles the infrared illumination, yellow circles the stero scene camera and the blue circle indicates the position of the illuminance measurement head.

gps and illuminance measurement

To measure the illuminance the driver perceives during the test drives, the illuminance is mea-sured at all times. This is done using a X1-1from GigahertzElectronics. The X1allows a maximum measurement frequency of up to 20 Hz while maintaining an auto-range setting to enable measurements across a large range of illuminance. The measurement head is located right behind the rear view mirror, indicated by the blue circle in figure5.67. Compared to the location right next to driver’s head this position offers both, advantages and disadvantages.

This position is located further away from the driver’s head, leading to slightly different val-ues than the driver actually perceives, and due to the position behind the mirror, it does not record light reflected by the rear view mirror. On the other hand, the driver can not cover the measurement head by moving his position. Furthermore, the position and of the sensor stays the same for all test drives and is not influenced by movement of the driver’s seat.

Additionally, to that, the rear view mirror in the test vehicle dims downs automatically and thereby reduces the light reflected to the driver anyways minimizing this influence.

The^GPS sensor is set to 10 Hz and located on top of the test vehicle over the right passenger seat at the back.

eye-tracking system

The main measurement equipment however, the eye tracking system, is the same system as used is in chapter5.3. This system is already pictured in figure5.67where the four cameras used are shown by the red circles. As explained in chapter to guarantee equal light situations for both day and night drives, the cameras are fitted with infrared passband filter and three additional light sources, marked by the green circles in figure5.67, are installed. The cameras and the infrared light sources are placed in a manner, that allows for wide and natural head movement, while minimizing the impact on the vision of the driver.

166 analysis and optimization of light distributions

Before each test run, the cameras need to be calibrated towards each other using integrated calibration routine of the SmartEyesoftware. In the next calibration step, the gaze direction for each test subject needs to be adjusted since, as explained in chapter2, the calculated gaze direction through the eye ball centre and the actual gaze direction, are not the same and for every test subject different. The setup for this is shown in appendixE.1in figureE.4.