1370431 Photo-electric size measurement KONTRON GmbH & CO KG 8 Oct 1971 [13 Oct 1970] 47060/71 Heading G1A [Also in Division G4] A specimen 7 on a stage is scanned by moving the stage a coding disc 9 being provided to provide pulses which are counted to determine the displacement. Light transmitted by or reflected from the sample is received by a microscope including a beam-splitting prism 3 and optical component 2 which are arranged so that the brightness of the light received by a semiconductor photo-detector 1 is independant of the system magnification. The output of the detector is applied via a low noise amplifier 4 to a discriminator 12 which selects signals in a predetermined range and converts them into pulses representing units of time. Logic circuitry is provided to integrate the measurements during a raster scan to determine the size of components of the sample e.g. to investigate crystallization, grain growth, plastic deformation or sintering.