James A. Kuchenbecker, Sara Patterson, Maureen Neitz, Jay Neitz; The best of both worlds: A Maxwellian view visual stimulator incorporating a DLP spatiotemporal light driver with a programmable tunable spectrum source for studying human color vision. Journal of Vision 2017;17(15):45. doi: 10.1167/17.15.45.
For decades, psychophysical experiments investigating human color vision were performed using multichannel Maxwellian view optical systems. These employed grating monochromators and spectral filters to provide exquisite control of the spectral properties of the stimuli which are important for color matching experiments, measurements of wavelength discrimination, and spectral sensitivity in people with normal color vision and a variety of vision disorders. However, those systems provided limited control of the spatial and temporal aspects of the visual stimulus. Later, computer-controlled video displays became popular, offering vision scientists tremendous freedom to manipulate stimuli in time and space. However, the spectrum of a video display is limited to just a red, green, and blue primary, which greatly restricts the type of experiments that can be done to test hypotheses about color vision mechanisms. To overcome the limitations of both afore-described visual display systems, we have developed a visual stimulus generator using a DLP mirror based projector (LightCrafter (LC) 4500), and a programmable tunable light source (OL 490 Agile) which can provide high speed programmable spectra with monochromatic band-passes and continuous spectra with any distribution. These two devices are synchronized so that spectrums generated by the OL 490 are substituted for the RGB primaries of the projector. This produces a display with high spatial resolution, precise and fast timing, repeatable gamma functions, and any spectrum on three separate channels. In addition, a standard digital video input on the LC allows for presentation of images generated by Psychtoolbox, P5, or ViSaGe (Cambridge Research Systems).