A Human Factors Analysis of Optical Distortion in Automotive Glazing
Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
The glazing is today a part of the car design. The customer is more or less taking for granted that his or her view from inside the car is a direct mirror of the outside world. With more complex shapes, lower installation angles and thinner glass it is a great challenge to produce even better quality at a lower price. While the windscreen is regulated by law, the lack of well specified requirements for the optics in the backlight (rear window), together with the absence of direct customer complaints, is causing the optical quality of the backlight to decrease. The requirements and measuring methods used today are described in technical terms and do not correspond to the human perception of optical distortion.
This report is a first step towards new technical requirements, for the optics of backlights, based on the driver’s perception of optical distortion. The knowledge of how optical transmission distortion occurs, how it should be measured and how it affects the driver, is essential in order to control it.
Several databases were searched and contacts with experts were established, in order to gain knowledge. The connection between the technical requirements and the human perception of optical distortion in backlights was investigated by using psychophysical methods. A within factorial design was employed with two independent variables; viewing distance from backlight to tailing object and fixation time (viewing time). The result showed a significant difference in perception of optical distortion between 25 and 75 metres. Moreover, optical distortion is, according to the test, more disturbing during free fixation time than for fixation times of about one second.
The requirements often used for backlights today (12 ± 5 millimetres) allow distortions that 68 percent of the test subjects perceived as disturbing. In order to please the test driver from Volvo the requirements need to be as high as 12 ± 2 millimetres, which correspond to the 96th percentile. Furthermore, the result confirms that dynamic measurements are needed to find a connection to human perception of optical distortion. The principles of a new measuring method that measures the deformation and the dynamic distortion were developed to show the possibilities of measuring what the driver perceives.
Even if a good measuring method can help controlling the produced glazing it is not enough to optimize the quality of the production. More important is the choice of thickness and curvature of the glass, the installation angle and the manufacturing method. It is important to set about the origin of the problem and develop a good routine of how to work with optical distortions. Optical distortions in backlights, similar to the tested backlight, have a low probability to disturb the driver in such extent that it has an effect on the driving. Nevertheless, it is a source of irritation and discomfort, which do not belong in a premium car.
Place, publisher, year, edition, pages
Institutionen för ekonomisk och industriell utveckling , 2007. , 82+Appendix p.
Optical Distortion, Automotive, Backlight, Technical Requirements, Visual Perception, Psychophysics
Production Engineering, Human Work Science and Ergonomics
IdentifiersURN: urn:nbn:se:liu:diva-8709ISRN: LIU-IEI-TEK-A--07/00130--SEOAI: oai:DiVA.org:liu-8709DiVA: diva2:23411
Subject / course
2007-03-30, A33, A-huset, Linköping, 10:15
The video files are also clickable from the pdf file pages 29 and 56.2007-04-252007-04-252012-04-24Bibliographically approved