Touch-sensitive pushbutton switch

Abstract

A touch-sensitive pushbutton switch includes an optical sensor, in particular an infrared sensor, and an evaluation circuit. The evaluation circuit is able, through the use of a reference device, to set a sensitivity of the optical sensor in dependence on a detected basic level of an evaluation signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, diagrammatic, sectional view illustrating the construction of a touch-sensitive pushbutton switch in accordance with a preferred exemplary embodiment of the present invention;

FIG. 2 is a simplified schematic circuit diagram of an evaluation circuit for the touch-sensitive pushbutton switch of FIG. 1;

FIG. 3 is a signal diagram elucidating a signal profile of an evaluation signal of the evaluation circuit of FIG. 2; and

FIG. 4 is a signal diagram elucidating a setting of a sensitivity of an optical sensor of the touch-sensitive pushbutton switch of FIG. 1.

Claims

1. A touch-sensitive pushbutton switch, comprising: a covering being at least partly transmissive to electromagnetic radiation;an optical sensor disposed behind said covering and having an electromagnetic-radiation-emitting transmitter and an electromagnetic-radiation-receiving receiver;an evaluation circuit for evaluating a measurement signal generated by said receiver and generating an evaluation signal; anda reference device for conducting part of the electromagnetic radiation emitted by said transmitter to said receiver even without actuation of the pushbutton switch, and generating a basic level of the evaluation signal;said evaluation circuit setting a sensitivity of the optical sensor in dependence on a detection of the basic level of the evaluation signal.

2. The pushbutton switch according to claim 1, wherein said evaluation circuit sets a minimum swing of the evaluation signal necessary for identifying an actuation of the pushbutton switch, in dependence on the detected basic level of the evaluation signal.

3. The pushbutton switch according to claim 2, wherein the minimum swing of the evaluation signal necessary for identifying an actuation of the pushbutton switch is set to a predetermined factor of a reference swing corresponding to the detected basic level.

4. The pushbutton switch according to claim 1, wherein said reference device has a diaphragm frame with a partition disposed between said transmitter and said receiver, and said partition has an at least partly transmissive passage opening formed therein.

5. The pushbutton switch according to claim 1, wherein said covering covers said reference device and has front and rear surfaces, and part of the radiation emitted by said transmitter is reflected at least at one of said front or rear surfaces of said covering in direction of said receiver.

6. The pushbutton switch according to claim 1, wherein said reference device has a diaphragm frame with a partition disposed between said transmitter and said receiver, said partition has an at least partly transmissive passage opening formed therein, said covering covers said reference device and has front and rear surfaces, and part of the radiation emitted by said transmitter is reflected at least at one of said front or rear surfaces of said covering in direction of said receiver.

7. The pushbutton switch according to claim 1, wherein the electromagnetic radiation emitted by said transmitter and received by said receiver is infrared radiation.