| 摘要 |
PROBLEM TO BE SOLVED: To provide a superior detecting circuit having a large S/N ratio and a superior detecting sensitivity while an outgoing beam emitted from a light emitting element will make the total internal reflection in case a finger does not contact with a touch face. SOLUTION: In an optical type touch switch using the light emitting element and a light receiving element, the outgoing beam emitted from a light emitting element enters into a light guide body, and the incident light is reflected by the touch face installed at the light guide body, and the reflected light is led to the light receiving element, and when a finger does not contact with the touch face, almost all of the incident light led to the light guide body enters from the light emitting element is made to have the total internal reflection at the touch face and to enter into the light receiving element, and when the finger contacts with the touch face, a part of the light transmits through the finger, and by utilizing the fact that the incident light to enter into the light receiving element greatly decreases as the other light has irregular reflections by the finger, a contact of the finger is made to be detected.
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