A large class of perceptual studies of the temporal (or teansient) response of the human visual system requires a tachistoscope for stimulus presentation. The current tachistoscope operates by optically exposing the subject to two or three photographic stimuli in a controlled sequence. Due to several limitations of this optical device. we explored the possibilities of a video instrument which would perform the same function. After about two yiiars of searching, and simultaneous advances in high speed electronics, we now know how to build the device which would allow us to perform the perceptual studies. This proposal deals specifically with the development of the tool necessary for the perception research, and does not address the psychophysical experiments. The video tachistoscope- requires new technology to achieve the high bandwidth and high data rates required for displaying a sequence of images. Fortunately. Brian Rosen's group at MegaScan Technology has the expertise to manufacture the components which require the new technology. These components, with the necessary software and computer. Will be assembled at North Coast Engineering to produce the whole """"""""system"""""""" referred to as the -video tachistoscope-. North Coast Engineering is committed to developing the entire system. including the higher-level software for stimulus generation and manipulation. Compared with a standard photographic/optical tachistoscope, a video tachistoscope would have more flexibility in image creation. storage. and presentation. However, stand2rd video frame rates do not give sufficient temporal resolution in expertmental displays. We will build and test a video tachistoscope capable of 500 frames per second, 512x5l2 pixels per frame. and Bbits per pixel, with programmable tradeoffs among these three parameters. At 500 frames per second. the temporal resolution is one frame interval or 2 milliseconds which is necessary for perceptual experiments using tachistoscopic presentations in the study of spatio-temporal response characteristics or motion. The fast display system will consist of a specially designed monitor with P167 phosphor, a controller with image memory. and an interface to a microcomputer. The controller memory module will store from I to 128 Images which could be generated by the computer or selected from a library of stimulus images. The display sequence willbe programmable so that each of the stored Images can be displayed for a specified number of video frames. Upon completion of the first instrument, we will test its electronic and optical characteristics Then, we plan to conduct experiments using both the optical tachistoscope and the ew Instrument. then proceed to use the video tachistoscope in various experiments in visual perception and aging, as well as develop software for efficient use of the highly flexible and powerful instrument. After the first unit, the new Instrument will be relatively inexpensive and affordable by many research labs, academic departments. and vision testing labs.
