VIS-NIR imaging

VIS-NIR cameras are electronic imagers sensitive to visible and near infrared radiation that generate output electronic image. VIS-NIR cameras are typically imagers built using silicon solid state sensors manufactured using two competing technologies: complementary metal-oxide-semiconductor (CMOS) or charge-coupled device(CCD). However, a growing number of high sensitivity VIS-NIR cameras use silicon solid state sensors built using non-standard technologies: intensified CCD (ICCD), intensified CMOS (ICMOS), electron multiplied CCD (EM CCD), electron bombarded active pixel sensor (EBAPS sensor, electron bombarded CMOS (EBCMOS), microchannel plate complementary metal-oxide semiconductor (MCPCMOS), scientific CCD (sCCD), scientific CMOS (sCMOS).

From point of test methodology, technology of manufacturing imager sensor is of no importance and details of differences between different types of image sensors used in VIS-NIR cameras shall not be discussed here. More important is division of VIS-NIR cameras on criterion of electronic image standard. Great majority of VIS-NIR cameras generates electronic image using two analog video standards: PAL or NTSC. However, increasing number of VIS-NIR cameras use different digital standards: Camera Link, GigE , LVDS, SDI, DVI, HD-SDI, HDMI, AHD, HD-TVI, HD-CVI, CoaXPress, USB2.0, USB3.0, Ethernet. Practically it means that different frame grabbers and acquisition software are needed to capture VIS-NIR cameras present on market.

Terminology of technology of VIS-NIR imaging is not standardized and a series of different names are used for these cameras: CCD cameras (in past majority of VIS-NIR cameras were CCD cameras), TV cameras (VIS-NIR cameras could be treated as successors of classical old television cameras), day light cameras (VIS-NIR cameras are mostly used at day conditions in contrast to thermal imagers used at night conditions), video cameras (VIS-NIR cameras generate live video type images), machine vision cameras (almost all cameras used in machine vision are VIS-NIR cameras).

VIS-NIR cameras have found a very wide range of applications and are manufactured world wide in very big numbers. This website concentrates mostly on testing high-end surveillance cameras. These are expensive VIS-NIR cameras integrated with big zoom objectives that enables long/medium range surveillance and are used in defense applications, protection of important infrastructure, search and rescue operation, and environmental protections. VIS-NIR cameras are often under-estimated in comparison to thermal imagers. However, they have proved to be a valuable tool in long range surveillance due to their ability to deliver high resolution color images at continuously regulated FOV when keeping size, mass and price several times smaller comparing to thermal imagers of similar FOV. Next, best VIS-NIR cameras can effectively operate at both day and night conditions. Measurement ot performance parameters are extreme lighting conditions is considered as crucial for proper evaluation of these high-end surveillance cameras.

Testing and evaluation of high-end VIS-NIR cameras for long/medium range surveillance is practically not standardized. There several modern standards issued by international organizations (European Broadcasting Union, European Machine Vision Association, British Standards Institution) that regulate testing VIS-NIR cameras in three specific civilian applications (television studio, machine vision, short range CCTV surveillance) but no standards that regulate testing and evaluation of discussed here military type VIS-NIR cameras. In this situation tests of military type VIS-NIR cameras are typically done using modified methodology of testing thermal imagers. Light sources replace blackbodies in test system. Minimal Resolvable Contrast replaces Minimum Resolvable Temperature Difference as the main parameter. There are also several other differences.