A control device for an image display includes at least two reference points, a modulation unit and a remote controller. The modulation unit modulates the light of a predetermined spectrum generated by the reference points with a brightness variation cycle. The modulation unit controls the reference points to emit the light with a first brightness within a first period of the brightness variation cycle and to emit the light with a second brightness within a second period of the brightness variation cycle, wherein the first brightness and the second brightness are not zero gray level. The remote controller captures the light of the predetermined spectrum with a sampling cycle and demodulates an image variation of the reference points with respect to the remote controller. The present invention further provides a control method for an image display.