A Real-Time and Portable Bionic Eye Simulator - Biomedical Engineering Systems and Technologies - page 41

Fig. 12. Ball Interception Test Setup

and that particular roll was done again at the end of the trial. For each mode, 60 rolls
were done. A predefined randomised roll sequence was used that ensured each of the
4 ramps was used equally and also that there was an equal amount of 'fast' and 'slow'
rolls. The aim of this test was to observe the effects of lowered frame rates, and so the
modes tested were: a control (full resolution, full colour) and 4-level thresholding at
4Hz, 10Hz, and 60Hz. Subjects were given 5 minutes to familiarise themselves with the
task before beginning the trials. The testing was conducted in a single session, with a
minimum 1 minute break in between each mode tested.

5 Results and Discussion

5.1 Maze Test
The left graph in Figure 13 details the time to completion (in seconds) for each mode,
averaged over the 7 subjects. The order of the modes reflects the order that the subjects
were tested in. The error bars show the standard error. 2-way, paired T-Tests were con-
ducted between the control time and each of the non-control modes, as well as between
the 4-level thresholding full frame rate mode and the other 3 modes (binary and both
reduced frame rates).
The times taken for all the non-control modes were significantly higher ( p < 0 . 05 for
all) than the time for the control. The binary and reduced frame rate modes were slightly
longer than the 4-level thresholding full frame rate mode, but all the non-control modes
were within the statistical margin of error ( p > 0 . 05 for all).
The right graph in Figure 13 details the number of collisions for each mode, averaged
over the 7 subjects. The error bars show the standard error. The average number of
collisions was very low, due to a few of the subjects not colliding with anything in
any of the modes, but the binary thresholding and reduced frame rate modes had more
collisions on average than the 4-level thresholding full frame rate.

5.2 Chessboard Test

The left graph in Figure 14 details time to completion (in seconds) for each mode,
averaged over the 7 subjects. The order of the modes reflects the order the subjects were