Chromatic Effect Reproduction of Irlen Colored Filters by a Pulse Width Modulation-Driven Three-Chromatic Light Emitting Diode Device

Abstract

Visual Stress (VS) is an abnormal visuoperceptual condition caused by an imbalance in light adaptation ability which yields reading deficits. It was first described in 1983 and, since then, has been treated with the usage of colored spectral filters, either as Irlen overlays either as lenses for symptoms relief. However, the limited options of overlays compromise the pursuit for the patient’s optimal filter so that a device that could provide a broader range of colors would improve achievements for both screeners and patients. The present work aims to develop a micro-controlled RGB LED device whose goal is to reproduce Irlen overlays combinations chromaticities through colored light metamers. Such a device can open possibilities for better diagnosing Visual Stress (VS) by providing screeners a much more extensive range of colors than regular overlays and glasses and, therefore, allowing more accurate scrutiny of the optimal chromatic point for the patient. For the pursuit of this goal, a LED controller based on PWM (Pulse Width Modulation) of currents was built, and a color reproduction methodology was developed to ensure chromaticity matching. From the 47 filters considered, 22 showed a ratio ΔE/JND < 6 and, thus, laid within a range that could provide the reading performance associated with its corresponding filter. Reproduction methodology was effective and demanded 5 main inputs: LED individual and white point color coordinates plus LED characterization curves. The controller proved to be effective for color manipulation inside the device’s gamut, which opens the possibility for both readjustment of the chromaticity, if it is found to vary with patient’s aging, and further connection to an eye tracker to shorten the search for the optimal point.