Temporal adaptation to light intensity for spatially complex stimuli

Temporal adaptation to light intensity for spatially complex stimuli

Ciocoiu, J.J.

Heynderickx, I.E.J. (mentor)

Electrical Engineering, Mathematics and Computer Science

Interactive Intelligence Group

Master Media and Knowledge Engineering

2012-07-10

The human eye is a complex organ of the human body which is able to cope with a lot of different situations. One of these situations is adapting to different light intensities by changing the dynamic range of the eye, so-called temporal adaptation. This report gives insight into what temporal adaptation means for luminance visibility while driving on an urban street during nighttime. The first step needed was collecting data of luminance values falling onto the retina while driving in the dark. As driving with a head-mounted eye-tracker was impractical and insufficiently accurate, the experimental set-up was changed into a lab set-up. An HD camera was used to record a video during driving in the dark, while a luminance camera was used to measure the corresponding luminance values. The resulting video was shown to 20 participants in the lab, and they were asked to watch the movie as if they were driving themselves. Their gaze positions on the screen were measured using a table mounted eye tracker. The gaze positions were converted into saliency maps, which were then combined with the luminance values of the video frames to generate weighted luminance maps. From the weighted luminance maps luminance profiles were deduced, representing the luminance value falling on the center of the retina as a function of time. The luminance values measured in these profiles varied between about 1 and 18,000 cd/m2. About 54% of the fluctuations in luminance within a one-second time frame had a difference below 1000 cd/m2, while about 6% of the fluctuations had a difference larger than 10,000 cd/m2. The effect of temporal adaptation on these luminance fluctuations was estimated by superimposing a temporal adaptation model existing in literature on the luminance profiles. Light adaptation (i.e. from a dark to a bright environment) is so fast that we considered it instantaneous for our application. Dark adaptation (i.e. from a bright to a dark environment) is somewhat slower and so was expected to delay the perception of the lower luminance values. However, also for dark adaptation the initial drop in perceived luminance is so fast that temporal adaptation only had a small effect on perceived luminance for the highest light intensity fluctuations. It should be noted, however, that literature on temporal adaptation only reports adaptation to homogeneous light intensity fields, while in our particular case of driving on an urban street during nighttime the visual field was characterized by a rapidly changing spatially complex light intensity field. Models to describe temporal adaptation to spatially complex light fields do not exist yet, and so, may affect the conclusions of our research.

adaptation
spatial adaptation
temporal adaptation
eye adaptation
light adaptation
dark adaptation
luminance

http://resolver.tudelft.nl/uuid:8f834bca-fde1-4095-bf32-6b9500affe27

Student theses

master thesis

(c) 2012 Ciocoiu, J.J.