Touch panel devices have a display function and an input function, and superior intuitive operability. Thus, in recent years, they have been used as an input device (or a manipulation device) for a variety of electronic equipment such as ATMs (automated teller machines) for financial institutions, portable digital assistants (such as a tablet PC (personal computer) and a smartphone), or medical equipment.
With respect to a touch panel of a touch panel device, there exist touch panels of various detection schemes according to the principle of operation, such as a resistive touch panel, a capacitive touch panel, a surface acoustic wave touch panel, an optical touch panel (an infrared optical imaging touch panel), and an electromagnetic sensing touch panel. Thus, with respect to a touch panel of a touch panel device used as an input device for electronic equipment, a touch panel of a most suitable detection scheme is selected according to, for example, the application, the environment, and the specifications. However, each detection scheme has both strong and weak points, and there exists no detection schemes that have an advantage in every aspect.
For example, a capacitive touch panel has the advantage of high transmission and great durability.
A touch panel is known that is used in a processor of an endoscopic device as an input device of medical equipment (see, for example, Japanese Laid-open Patent Publication No. 2009-37343). For example, the following operation is performed in this touch panel device: when a first display button is pressed down, a processor control circuit that received a signal indicating a pressed position calculates an amount of shift from a center point of the first display button to the pressed position; an area that can react is extended on the basis of the amount of shift, the area being set for the first display button; and before the time period that has elapsed since the first display button was pressed down last time reaches a predetermined upper limit time period, a second display button is pressed down in order to cancel out a function to be executed by the first display button being pressed down, and the extended reaction area is restored to a reference area that is an original reaction area.