Abstract: A hot casting, freshly emerging from the mold, is inspected for any surface defects by a revolving line scan camera; the camera is disposed in an annular water-cooled, two-part housing having an inwardly directed annular gap covered by a sheet that revolves with the camera; the camera can look through a small gap of that sheet.

Abstract: A current mirror amplifier including three or more tandem stages has a photo diode connected, as usual, with one end at the input of the first stage, but with the other end at the input of a third or later stage, which third or later stage is made up of transistors of the same polarity type (NPN) as make up the first stage. Consequently a very low reverse bias is advantageously applied to the photo diode and the linearity and stability of the resulting photo electric device is enhanced with respect to changing input light levels and with respect to variations in DC supply voltage.