Limiting resolution of low-light-level imaging sensors.

Abstract

Through the aid of electronic light amplifiers, observers can view terrain on moonless nights with near-daylight acuity. This improvement in vision is obtained by using imaging sensors with larger lenses, greater quantum efficiencies, wider spectral responses, and larger photosensitive areas than those of the unaided eye. The observer’s improved resolving power using these sensors can be calculated in terms of a limiting resolution vs light level and an elemental signal-to-noise ratio at any operating point. The analysis facilitates the comparison of sensors on an equal basis and provides the system designer with more detailed sensor operating data. As examples, the limiting performance is calculated for the image orthicon and the secondary-electron conduction camera tube with and without cascaded image intensifiers. The calculated results are compared to those measured and are found to be in good agreement.