Display strobing: An effective countermeasure against visual blur from whole-body vibration

Crews and equipment in aerospace vehicles, including spacecraft at launch, can be exposed to significant vibration. Prior to this study, we examined the ability of vibrating observers to read alphanumeric symbology on stationary (i.e., non-vibrating) flight-relevant display formats and noted performance degradation with increasing vibration amplitude and decreasing font size. Here we test the efficacy of a display strobing countermeasure for the reading decrements caused by the same 12-Hz whole-body vibration in the surge (chest-to-spine) direction applied in our prior studies. To produce the strobe countermeasure, we triggered the backlight of a stationary liquid crystal diode (LCD) display panel to flash in synchrony with the 12-Hz vibration of the observer’s seat while experimentally varying both the strobe duty cycle and phase angle between the strobe onset and the vibration cycle zero-crossings. Strobing proved an effective countermeasure, restoring reading error rates during 0.7g (6.9m/s2 half-amplitude) whole-body vibration to levels indistinguishable from those achieved under the non-strobed (equivalent luminance) non-vibrating baseline condition and improving response times although not fully to the baseline. While we noted differences in the “preferred” phase angle of individual observers, on average, no overall effect of phase angle was detected. Likewise, no effect was seen for the two duty cycles and their respective equivalent luminance levels. Further studies are needed to determine the efficacy of strobing for multi-axis and multi-frequency vibration, and for displays with moving images.