“SmartGlass” Obstacles for Dynamic Inducing of Light Scattering in Vision Research Experiments
We describe a technique that allows control of visual stimuli quality through the use of a setup with a polymer dispersed liquid crystal (PDLC) film positioned in the optical pathway of one or both human eyes. Nowadays, PDLC films allow alteration of the resolution and contrast limits of the transmitted light due to continuous change in the light scattering that is obtained by the application of an AC electrical field. In our experimental setup, the use of a wide-aperture up to area of 20 x 15 cm2 PDLC sheet is combined with a flat-screen PC display or with a modified display emission block without its interference filter unit and with an installed individually controllable colored light-emitting diode (LED) backlight. In the latter case, the spatial structure of visual stimulus remains constant, but the PDLC switching-on timing for intensity, color, and contrast of visual stimuli control is done by a PC via an Arduino USB interface. Arduino applies a voltage to the backlight colored LEDs and the low voltage up to 30 – 80 V to light-scattering PDLC sheet. Modifications to this setup can improve the resolution of the timing and screen stimulus intensity and color purity, and increase the flexibility of its application in visual research tasks. A particular use of PDLC scattering sheets involves the altering of the stimuli input strength of the eye in different binocular viewing schemes. In such applications, a restricted-optical-aperture PDLC element is mounted in a goggle frame, and the element is controlled by the application of low-voltage AC field. The efficacy of the setup is demonstrated in experiments of human vision contrast sensitivity adaptation studies. Studies allow to determine the characteristic time of the contrast sensitivity altering of 4 s during adaptation phase and the same order of the characteristic time during recovery.
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