Abstract: An electrostatic opposing field spectrometer has an extraction electrode (AN) and an opposing field electrode arrangement with a pair of planar opposing field electrodes (EG1 and EG2) mounted to an outer electrode part (EM) at either end of a truncated conical shaped bore extending therethrough, where the smaller opening of the bore is in the direction of the extraction electrode (AN). The planar opposing field electrodes (EG1 and EG2), in conjunction with the bore surface, generates substantially spherical equi-potential lines (A1 and A2) which transmit a larger solid angle distribution of secondary electrons (SE) triggered at a measuring point (M) on the specimen surface (PR).