Slope Calibration Algorithm for OLED Display Gamma-Tuning Instruments

Abstract

Unlike LCDs that use backlight, OLED display emits light by itself. Due to this, the accuracy of the gamma tuning process calibrated by the measurement of the photometric characteristics of panels plays a crucial role in the OLED manufacturing process. For accurate photometric measurements, measuring the tilt angle of the panel is essential because the horizontal angle of an OLED panel, when an optical instrument inspects it, must not exceed +/- 2.5°. In this paper, an algorithm that calculates the tilt angle through image processing on photo images of OLED panels placed on optical measuring devices is developed. The location of 4 corner points and the outline lengths of the tilted OLED panel can be measured. Then, the angles of the slope in the direction of the x- and y-axes with respect to the z-axis can be calculated to obtain the tilt of the panel. After that, to meet the range of errors required for optical instruments, the tilt of the panel can be corrected to be placed horizontally by providing information on the slope. The mean error comparing the slope calculated by this algorithm with the actual measured slope is about 1.09°.