A photo detective LCD device includes a light pen. The light pen includes a body, a driving pulse generating module and a light generating module. The body has a pen shape, and an end of the body includes an opening through which light exits. The driving pulse generating module is disposed in the body and generates first and second driving power pulses having first and second frequencies, respectively. The light generating module generates first and second light in response to the first and second driving power pulses, respectively. The first and second light flickers in a third frequency and a fourth frequency, respectively. The power consumption is reduced, and the brightness of sensing light is enhanced. The light pen generates light having at least two different frequencies, and the display device recognizes light generated from the light pen effectively. Therefore, the display device may operate without failure.
1. A light pen comprising:
a body;
a driving pulse generating module that is configured to generate a first driving power pulse having a first frequency during a first time period and a second driving power pulse having a second frequency during a second time period, the driving pulse generating module being disposed in the body; and
a light generating module that is configured to generate a first light in response to the first driving power pulse and a second light in response to the second driving power pulse, the first light flickering at a third frequency, and the second light flickering at a fourth frequency.
2. The light pen of claim 1 , wherein the first and second frequencies respectively have a frequency except a commercial power frequency.
3. The light pen of claim 1 , wherein the driving pulse generating module generates alternately the first driving power pulse and the second driving power pulse.
4. The light pen of claim 1 , wherein the light generating module includes a light emitting diode or a semiconductor laser beam generator.