2. Virtual Retinal Display (VRD) Emulator Test System H.L. Pryor, B. Burstein, J. Kollin, E.S. Viirre, E. Seibel, J.P. Kelly, T. Furness III. Human Interface Technology Lab; University of Washington; Seattle, WA Washington Technology Center Introduction: "Virtual Retinal Display" (VRD) scans intensity modulated laser light pixels directly onto retina. Each pixel is modulated in short pulses of 30ns to 40ns. The input light is a combined beam from three different wavelengths of laser light which produces a color gamut exceeding that of a conventional CRT. Current system produces VGA resolution, at 640 x 480 pixels. The area covered by the laser spot on the back of the retina for the duration of a single pixel is called a “retinel.” Background: Emulator System Requirements: The scanned light sources of the emulator will be modulated by passing the light through a 35mm slide. Capability to: –Vary spot size at the retina. –Vary the spacing between between horizontal lines –Vary the spacing between pixels –Vary scan rates of the system –Investigate coherent versus incoherent light –Control light intensity –Use a common source of modulation –Match laser lines of VRD (645, 514, 472 nm)and other color combinations –Characterize optical parameters –Automate data collection RulerRuler Conclusions: Supported by NSF grant IRI 97-03598 and Microvision Inc.. Human Interface Technology Lab Predicted Results: Contrast sensitivity at lower spatial frequencies will be higher. Possible shift at higher spatial frequencies but not as likely. Subject’s critical flicker thresholds should be consistently higher with the VRD relative to the CRT. Retinels size should be able to approach foveal cone spacing. As retinels approach cone spacing line separation will become less tolerant. Light coherence will have minimal effect on the enhanced performance. The point and angle of entrance beams at the corneal surface will be identified as major contributors to the enhanced performance. Retinel Unlike CRT monitors, the VRD has no phosphor persistence but depends on the light-gathering properties of the photoreceptors and the temporal integration properties of the visual system. Therefore, the interactions between the VRD delivered light and the psychophysical image quality created by the brain are of extreme importance for future enhancements. The enhanced image quality of the VRD is believed to be the result of several system properties: 1) Small exit pupil which gives large depth of focus 2) Beam size which minimizes optical aberrations at cornea 3) Laser light penetrates mild to moderate media opacities with minimal scattering 4) High luminance and high color contrast 5) Collimation and coherence of the light 6) Decreased flicker sensitivity 7) No perceptual laser speckle Unfortunately, the current VRD design does not provide a way to test many of the these system properties. Therefore an Emulator of the VRD has been developed. VRD Emulator Test System Non-Coherent Light Argon Laser Red Laser Polygon Scanner Slide AO Modulator Galvonometer The scanned light from the emulator will serve as an excellent research test bed for future VRD research testing. System Design: