Photometer

摘要

The invention relates to a photometer, in particular for the measurement or control of light intensities in plasma processes. In this case, the light to be measured or controlled is fed via an optical fibre (23) to a light chopper (26) and compared, displaced in time, with a second light source, which is, for example, a reference light source (29) having pulsed light. This comparison can be achieved by means of quotient formation and be carried out by means of an analog divider circuit (34, 35, 43, 45). This divider circuit (34, 35, 43, 45) makes it possible to process a signal with high accuracy over four decades, referred to the amplitude of the signal. The output signal obtained by the proportioning is used for the control of a process in which the light brightness of one or more spectral lines is influenced. <IMAGE>