Abstract: An inverter apparatus having at least an inverting portion for inverting a DC electric power into an AC electric power, wherein the inverting portion includes: high speed switching elements; driver circuits for driving the high speed switching element; and a controller portion for outputting logical driving ON/OFF signals for controlling the AC electric power to the driver circuit, wherein the controller portion controls so that the minimal time of the OFF signal of the logical driving ON/OFF signals for the high speed switching element comes to be equal or greater than a predetermined value, thereby protecting the high speed switching elements constructing the inverter apparatus from breakdown due to a the short OFF pulse.

Abstract: In a four-sheet lens configuration composed of convex, concave, convex, and concave lenses, predetermined conditional expressions are satisfied so as to attain a compact size and a wider field angle in a lens system for reading out images, while correcting various kinds of aberration. Further, a bright lens system is obtained. Successively from the object side, a first lens (L.sub.1) comprising a positive meniscus lens with a convex surface directed onto the object side, a second lens (L.sub.2) comprising a biconcave lens, a third lens (L.sub.3.sub.)comprising a biconvex lens, and a fourth lens (L.sub.4) comprising a negative meniscus lens with a convex surface directed onto an imaging surface side are disposed, while the following conditional expressions (1) to (3) are satisfied:0.87<f(1/R.sub.8 -1/R.sub.7)<2.75 (1)0.23<R.sub.1 /f<0.38 (2)1.08<.vertline.N.sub.4 .multidot.f.sub.4 .vertline./f<3.