In this paper, an active color control method is proposed to detect the scanned image of FPD system. The brightness of the light source is adjusted by using the high-power light-emitting diode (LED) and communication port of the mixed color source. The mixed light irradiates the active matrix organic light-emitting diode (AMOLED) panel after passing through the beam expander and forming a harness. After intensity correction, the image quality is evaluated by Tenenbaum gradient, and the dimming level is determined by simplex search method (SSM). Each time the AMOLED panel is scanned, the color of the light will change and will be repeated until the image quality is close to the local maximum value. The number of scans performed is less than 225, and the number of dimming level combinations is 20484. The proposed method reduces the manual setting of detection equipment and realizes automatic color lighting for obtaining high-quality images. It has certain practical value for FPD detection equipment.