What is resolution limiting?
When the light is bright the image turns out to be fully free of Photon Granularity. The optical resolution in line pairs/mm is constant and does not depend on the illumination intensity. Such working conditions are called resolution limited regime. The limiting resolution is characterized by means of Modulation Transfer Function (MTF) and Contrast Transfer Function (CTF).The contrast in an optical system functions as a spatial modulation of an input signal. The input should be 100% modulated the image could be parallel black and white line pairs. The output will turn out to be an image that is darker grey and in lighter grey line pairs. The human eye is usually able to notice a contrast down to 3%, which is hence defined as Resolution Limiting. You can define the contrast of the output as-
C=(max.brightness-min.brightness)/(max.brightness+min.brightness) when the brightness is taken from the output image. The contrast will depend on spatial frequency. The more lines in the line pair per mm the smaller the image detail and the contrast output are also lower.
Which all devices can be used for resolution limiting?
Photocathode- depends on acceleration voltage between the photocathode and microchannel plate. It amounts to 140lp/mm
Microchannel plate- the mean of the distance between 2 microchannels of 6 microns the limiting resolution of a single-stage microchannel plate gives the result 85lp/mm
Phosphor screen- the voltage between the microchannel plate and phosphor screen results in the resolution limit of 120lp/mm
Coupling lens- these can achieve a limiting resolution of 260lp/mm