The Visual System
We installed 3 42'' LCD monitors giving a 120 degree field of view.While CRT's are the preferred way to present visual stimuli, due to space constraints we had to use LCD's. The key for accurate timing is to measure the stimulus onset timing/delay of these screens. Manufacturers are silent about these numbers.
Each screen is driven by a dedicated computer, but the 3 graphics cards are frame locked and g-synced with a fixed update rate of 60Hz.
We build a circuit, using photo-transistors which allows us to determine the time point at which a screen area is illuminated and compared this with a trigger pulse send as the frame loop reaches the swap buffer phase.
The 3 screens stich nicely together, the lines between the screens give the impression of a cockpit.
