Resolution of the Image Sensor

Prototype ESA microscope: resolution test using 10 micrometre graticule

The image sensor does not permit the resolution of discrete mammalian cells, though it does show small cell aggregates and also provides satisfactory quantitative images of living aquatic protozoa. In this further assessment, a 10 micrometer graticule is utilised as a test object of known calibration.


Conventional light-ground illumination allows us to resolve the graticule with the 6mm lens and the sensor. At the centre, left extremity (appearing here like a grey rectangle) the transverse line spacing is 10 micrometers. The line spacing adjacent to this (centre) is at 100 micrometers, and the longer lines - left and right, marked by red crosses - are therefore one millimetre apart.

For reference, vertebrate cells are customarily 15 micrometers in diameter; cell aggregates often 40-50 micrometers in diameter. The separation of the 100 micrometer lines corresponds to that of a (coarse) human hair.

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