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Jakob Thomassen, Caterina Ripamonti; Correcting the spatial non-uniformity and viewing angle dependency of an LCD monitor. Journal of Vision 2016;16(12):249. doi: 10.1167/16.12.249.
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© ARVO (1962-2015); The Authors (2016-present)
Improvements in the characteristics of Liquid Crystal Displays (LCDs) are making this technology increasingly popular for vision science experiments. However, the effects of viewing angle dependency are still inferior to that of Cathode Ray Tube (CRT) technology, which have traditionally been used for presenting computer-controlled visual stimuli. Here we show how an LCD monitor can be calibrated to dramatically improve its spatial uniformity and how to compensate for its viewing angle dependency when the location of the observer is known and their position held constant. We first characterised the non-uniformity of the LCD by taking a series of measurements at different locations perpendicular to the screen. These measurements were then used to calculate coefficients for a model of the spatial non-uniformity of the screen. To test the calibration model, we made nine evenly spaced measurements perpendicular to the screen (3x3 grid) and found that the Michelson contrast fell below 0.02. However, this performance would only hold true if the visual angle subtended by the monitor was smaller than 30 degrees in the horizontal direction, beyond which the non-Lambertian characteristics of the LCD affect its light output. To compensate for a wider range of viewing angles subtended by the LCD, we characterised the dependency of angles in the horizontal, vertical and oblique directions. These data were then combined with the data from the perpendicular measurements to produce a model that corrects for both viewing angle dependency and spatial uniformity when the observer's location is known.
Meeting abstract presented at VSS 2016
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