| 摘要 |
<p>PURPOSE:To surely detect a touch position by detecting an external light level immediately before a light emission of a light emitting element by an opposed light receiving element, setting light receiving and light shielding threshold levels and deciding repeatedly a light receiving level at the time of light emission of the light emitting element. CONSTITUTION:Immediately before a light emission of a light emitting element, a light receiving element generates an output corresponding to an external light level. By a threshold level setting circuit 3, a threshold level is set higher than this output, and a light receiving level at the time of light emitting state of the light emitting element is decided by a light receiving and light shielding deciding circuit 4. In such a way, an output by an external light becomes smaller than the threshold level, therefore, no malfunction occurs. Also, in one direction of a bidirectional light receiving element 6, an output of the light receiving element becomes maximum by the external light, and in case it is impossible to set the threshold, a malfunction by a strong light from the just side does not occur either by nullifying its direction and deciding only the opposite direction.</p> |
