A sensor, such as a proximity sensor, having its components sealed within a case, has its sensitivity adjusted with a remotely settable digital potentiometer after assembly of the sensor. The present invention includes a first circuit to sample the incoming optical black signal output from a CCD. The assignment index field has a value greater than or equal to number of previously assigned subframes within the bundling window. The third semiconductor layer is formed in a third region of a part of the semiconductor substrate with the insulation film and the second semiconductor layer extending in the third region and interposed between the semiconductor substrate and the third semiconductor layer.