Night vision

Humans achieve ability to see at night conditions using several different imaging systems: night vision devices (image intensifier systems), thermal imagers, SWIR imagers, and some more sensitive VIS-NIR (CCD/CMOS/ICCD/EMCCD) cameras. However, due to historical reasons, night vision technology is usually understood as night vision devices.

Night vision devices (NVDs) are apparently simple systems built from three main blocks: optical objective, image intensifier tube, and optical ocular. The task of the optical objective is to create low intensity, invisible image of the observed scenery at input plane of the image intensifier tube. The latter tube consisting of a photocathode, an anode in form of a phosphor screen, and other components, intensifies an input low-luminance image into a brighter image created on the anode (screen). The latter image is seen by human observer using the optical ocular.
     Night vision is a fully matured technology that has found mass applications in both military, security and defense sectors. NVDs are offered on international market in form of a long series of devices of different design configuration, type of image intensifier tube, type of night vision optics, and performance. In spite of apparent simplicity, proper understanding, testing  and evaluation of NVDs is a complicated task as many details are to be taken into account. 
    Reading of following literature is recommended  to understand sophisticated situation on international night vision market  and situation in night vision metrology:
  1. Chrzanowski  K., Review of night vision technology, Opto-Electronics Review, 21 (2), p. 153-181, 2013 
  2.  Chrzanowski K., Review of night vision metrology, Opto-Electronics Review, 22 (1), 2015 
  3. Chrzanowski K., A computerized station for testing night vision devices, 6th International Symposium on Optronics in Defence and Security, Paris, 2014