Touch panels comprising a bias line biased at a bias voltage, a select line, a readout line, a photo cell and a readout circuit. The photo cell comprises a first photo switch, a second photo switch and a storage capacitor. The first photo switch and the storage capacitor is coupled in series between the readout line and the bias line, and the first photo switch is further controlled by the select line. The second photo switch is connected between the readout line and the bias line. The readout circuit and the select line are managed by a reset mode, an exposure mode and a readout mode. The voltage variation of output terminal of the readout circuit is used in obtaining the state of the photo cell.