1. Field of the Invention
The present invention relates to an input apparatus that uses a capacitive sensing method in detecting operations, and electronic equipment having the input apparatus.
2. Description of the Related Art
Conventionally, for digital equipment such as cellular phones, personal computers, car navigation systems, and digital cameras, techniques using a touch sensor or a touch panel as an input apparatus have come into widespread use. Examples of such input apparatuses include a capacitive type, a resistive type, and an optical type, and they have advantages and disadvantages and are used for a wide range of purposes. Among them, the capacitive type is excellent in detection accuracy and used for many devices. Some digital camera products equipped with touch panels using the capacitive sensing method have been released.
For input apparatuses using the capacitive sensing method, there are some detection methods, one of which detects the earth capacity of a human body, and this method has been used for many touch sensor ICs (integrated circuits). The ICs using this method are capable of detecting an electrical conductor with a ground potential approaching a sensor.
There are prior arts that apply this capacitive sensing type detection technique to a mechanical structure of an input apparatus (Japanese Laid-Open Patent Publication (Kokai) Nos. 2009-218785 and 2001-296966). First, Japanese Laid-Open Patent Publication (Kokai) No. 2009-218785 discloses the technique associated with a faucet device to detect the touch of a human finger or the like and continue an operating state even when a person moves the finger off the faucet device. When the touch of a human finger is detected using a touch sensor, and the faucet device is rotated, the rotating state of the faucet device can be detected and stored based on the position of an electrical conductor with a ground potential. By dynamically switching voltage applied to a sensor portion between a sensor detection potential and a ground potential, the rotating state can be detected with one sensor pattern.
Japanese Laid-Open Patent Publication (Kokai) No. 2001-296966 discloses a structure of a conductor which is incorporated in a rotating operation unit so as to improve resolution in rotation detection. In general, when the touch sensor technique is used for a rotating operation member, improvement of resolution in rotation detection can be realized by placing a number of sensor patterns. If this method is used, many touch sensor ICs may be required as the case may be, and this is not efficient. For this reason, according to Japanese Laid-Open Patent Publication (Kokai) No. 2001-296966, with attention focused only on detecting the direction of rotation, the number of types of sensors divided into blocks is three or more, and the sensors are arranged in order such that different types of sensors are adjacent to each other so that resolution in detecting the rotation of direction can be improved.
However, in the case where a plurality of types of sensors are used so as to improve detection resolution, the total area of each type of sensor patterns is small. Thus, the detection level of touch sensor ICs is relatively low. This tendency increases as the size of the rotating operation member decreases. In the future, a structure that optimizes (maximizes) the detection level of sensors as the size of the rotating operation member decreases so that the rotation of the rotating operation member can be efficiently detected at higher levels to improve detection sensitivity is desired.