A device in which a liquid crystal is combined with a touch panel is widely used as a display and operation unit for a small-sized information terminal and such. A user can operate the terminal by touching buttons displayed on a liquid crystal screen using a stylus or a finger. Although touch panels of a pressure-sensitive type and a capacitance type have been contrived, a problem of deterioration of image quality has been noted because such a touch panel has to be provided over a liquid crystal surface. In addition, as this increases the number of component parts, a problem of increased cost for members and assembly has also been noted.
According to Patent Document 1 (Japanese Patent Laying-Open No. 2004-318819), a technique of providing an optical sensor along with a circuit that drives a liquid crystal on a glass substrate has been contrived. With this technique, an input of an image, in addition to a display of an image, is possible as in a case in which commonly used scanners are used. Further, it is possible to use as a touch panel by processing the inputted image. As this type of touch panels can be manufactured in the same process as common liquid crystal display devices without additionally providing pressure-sensitive or capacitance touch panel members, it is also possible to reduce the cost.    Patent Document 1: Japanese Patent Laying-Open No. 2004-318819