Evaluation Methods for Stereopsis Performance
Stereopsis is one mechanism of visual depth perception, which gains 3D information from the displaced images of both eyes. Depth is encoded by disparity, the offset between the corresponding projections of one point in both retinas. Players in ball sports, who are adapted to highly competitive environments, can be assumed to develop improved performances in stereopsis, as they are required and thus trained constantly to rapidly and accurately estimate the distance of the ball. However, literature provides controversial results on the impact of stereopsis on sports such as baseball or soccer. The standard method to quantify stereopsis is to evaluate near static stereo acuity only, which denotes a subject’s minimum perceivable disparity from a near distance with stationary visual targets. These standard methods fail to reveal potential contributions of further components of stereopsis such as recognition speed, distance stereo acuity, and dynamic stereopsis, which were identified by literature to be important to describe the performance of stereopsis in sports. Therefore, this thesis contributes to the literature by introducing the Stereo Vision Performance (StereoViPer) test, which combines distance stereo acuity and response time analyses for static and dynamic stereopsis by using 3D stereo displays.
The first purpose was to provide a proof of concept for the static test. Experiments analyzed the response time measurements, compared the test with traditional methods and evaluated the ability of the test to discriminate between clear and known differences in stereopsis performance, i.e. normal and defective stereopsis. The second purpose was to provide investigations of stereopsis in highly competitive ball sports. Therefore, the test was extended by a dynamic part and a gesture driven input interface to support the connection between visual perception and motor reaction. The method was used to evaluate stereopsis in soccer by comparing professional, amateur, and inexperienced subjects. This thesis contributes to the evaluation of stereopsis in soccer by speed measurements and dynamic stimuli. The third purpose was to evaluate the influence of the used 3D stereo displays on the conducted stereopsis measurements. As 3D displays provide unnatural viewing conditions, a zone of comfortable viewing has been introduced in literature that should avoid discomfort during the consumption of simulated 3D content. This thesis contributes by investigating whether the zone is sufficient to obtain natural stereopsis performance results and which further limitations due to artificial 3D content might apply.
As the method could successfully discriminate between normal and defective stereopsis and produced results, which were in agreement with the literature, the proof of concept could be shown. However, soccer players did not show superior stereopsis performance compared to inexperienced subjects, although they demonstrated significantly (p <= 0.01) lower monocular choice reaction times. The zone of comfortable viewing did not preserve natural stereopsis performance. Therefore, disparities need to be selected as low as possible for stereopsis performance measurements.
In conclusion, the StereoViPer test produced results that are in agreement with the literature and extended the evaluation of stereopsis by static and dynamic stereo acuity measurements in combination with response time analyses. The test provides a finer discrimination of stereopsis performance than traditional methods. This thesis contributed to the investigation of stereopsis in competitive sports by introducing an extensive testing battery, which meets the requirements of suggestions in literature.