1. Technical Field
The present invention relates to position detecting devices and electro-optical devices, and more particularly, to configurations of devices that obtain position information regarding an object to be detected on the basis of values which have been optically detected.
2. Related Art
In typical display devices equipped with an electro-optical device such as a liquid crystal display body, a lighting device such as a backlight may be incorporated in order to make the display screen visible or enhance the visibility. In addition, in the display devices, the display screen may be provided with a pointed position detecting unit such as a touch panel. In this case, when a given position on the display screen is pointed by a pen, a finger or the like, the pointed position is detected and input into an information processing device or the like.
As the pointed position detecting unit (positional coordinate inputting unit) such as a touch panel, electrostatic capacitive type touch panels, resistive film type touch panels or the like that mechanically or electrically detect the state of a contact on the display screen are known. In addition, optical touch panels are known in which a grid of infrared light beams is formed across the display screen and photosensors are correspondingly provided so as to detect the infrared light beams, so that, when a finger or the like interrupts infrared light beams, the positional coordinates of the finger or the like can be detected. In general, various types of optical touch panels are known, and examples of the optical touch panels include the ones disclosed in JP-A-2004-295644 and JP-A-2004-303172.
However, in the optical touch panels described above, it is necessary to arrange, adjacent to the display screen, multiple light sources and photosensors, optical switches, or light guide structures or the like in order to support the resolution of positional coordinates to be detected. This increases the number of optical elements, whereby there is a problem in that the manufacturing cost is increased and more power is consumed.