THE EFFECT OF AMBIENT ILLUMINATION LEVEL ON PERCEIVED AUTOSTEREOSCOPIC DISPLAY QUALITY AND DEPTH PERCEPTION Monika Pölönen Nokia Research Center, PO Box 1000, 00045 Nokia Group, Finland Corresponding author, e-mail: Monika.Polonen@nokia.com Fax: +358718035322 Phone: +358 504837693 Marja Salmimaa Nokia Research Center, PO Box 1000, 00045 Nokia Group, Finland e-mail: Marja.Salmimaa@nokia.com Jukka Häkkinen Nokia Research Center, PO Box 407, 00045 Nokia Group, Finland e-mail: Jukka.Hakkinen@nokia.com Department of Mediatechnology, Helsinki University of Technology, P.O. Box 5500, FIN-02015 HUT e-mail: Jukka.Hakkinen@tkk.fi Displays 32(3) 135-141 Abstact Twenty participants viewed real-world videos with a small hand-held autostereoscopic device in three ambient illuminations with three display luminance levels. Perceived depth, naturalness, viewing experience, presence experience and discomfort were evaluated with two videos. The results show that illumination and luminance levels influence perceived quality parameters, but perceived depth is less sensitive to changes in ambient illumination than other parameters associated with 3D image quality. 3D presentations were immersive and realistic, which enabled exploration of the 3D world. Some mild visual strain symptoms were reported as a result of viewing scenes for 40 minutes. In conclusion, the use of auto stereoscopic hand-held devices seems feasible in different contexts with different display luminance levels, and the overall experience is enjoyable and immersive. Keywords: 3D, auto stereoscopic display, perceived depth, naturalness, viewing experience, sickness, visual strain, presence 1. INTRODUCTION As stereoscopic displays become more common, the issues related to various possible uses become more relevant. For example, if a mobile device has an autostereoscopic display, the display should be usable in various illuminance conditions ranging from a dim living room in the evening to bright sunlight in the daytime. High illuminance situations are problematic especially because they reduce the contrast of the display unless it has reflective components. Further, a large difference between the display luminance and the illumination level of the environment can reduce the visibility of the display, leading to sensations of discomfort or transient adaptation effects from fixating back and forth between two luminance levels [e.g., [1],[2]]. Chakrabarti, Kaczmarek, Thomas, and Romanyukha [[3]], among others, observed that room illuminance affects the intensity ratio of maximum to minimum monitor luminance. According to the authors, the consequent loss in the contrast ratio causes image contrast degradation. Even though a high contrast ratio is achieved when a very low monitor surround luminance of 0%–5% of the maximum is used in low ambient light of 5 lux or less, an increase in room illuminance can drastically reduce image contrast. Sheedy et al. [[1]] tested the effects of the luminance surrounding a computer display and showed that performance decreased at lower levels of surround luminance whereas higher surround luminance levels showed no effect on transient adaptation. Optimal performance was attained for surround luminance levels that were equal or higher than the display luminance. When participants were able to adjust the surround luminance level, they selected a luminance that was slightly less than the central luminance at 91 cd/m 2 , but the preferred levels varied widely across the subject sample.