An apparatus for inverting DC voltage to AC voltage by stacking of DC voltage sources from a series of DC voltage sources comprises a plurality of circuits. A receiver has a photodetector receiving an optical beam reflected by an object to be measured and converting it to an electrical signal, a switch receiving the signal from the modulating signal generator and alternately choosing two channels for the electrical signal with a predetermined timing, and first and second storage sections storing electrical signals on the two channels. In the secondary dismantling process, the remnant is dismantled while asbestos measures are implemented. Such a combined electronic display may provide a significantly reduced cost as compared to a similarly sized single electronic display. Angles formed between each of the two types of inclined surfaces and the lower substrate are different. Then, the substrate is developed so that overlapping regions of the substrate exposed by the pattern at the first location and at the second location are developed differently from non-overlapping regions of the substrate exposed by the pattern only at the first location or at the second location.