The present invention allows for dynamic association of a computational device, such as a personal computer or personal digital assistant, with a telephone terminal. Second separation grooves having a width smaller than that of the first separation grooves are formed by removing a second photovoltaic conversion layer and an intermediate reflective layer inside the first separation grooves. Moreover, the application of the reverse bias is performed by varying only the counter electrode, and thus withstand voltage of TFT and the increase of the electric power consumption due to the increase of voltage of the gate signal line drive circuit, which becomes a problem when changing greatly the electric current supplying line, can be suppressed. The image data is encoded responsive to the quantization step size value and the refined rounding offset value. The error correction signal is received by a controller that controls the operation of a postioner that adjusts the position of the heliostat accordingly. Lowering the threshold electron density of conduction electrons in the ground level of the conduction band of quantum dots in this way accelerates the relaxation process of electrons from an excited level to the ground level in the conduction band.