## Determining 4-Bar Target Sizes

IRCameras has provided this 4-bar resolution calculator to help a customer determine the appropriate set of resolution targets to test the minimum resolvable temperature difference (MRTD) of a customer’s sensor.

IRCameras recommends at least four 4-bar targets be used to develop a MRTD curve. The following calculator provides the appropriate spatial frequencies IRCameras suggests. Each of the targets are based on particular camera parameters and test system configuration.

The formulated target frequencies are related to the Nyquist frequency (symbol Fo) of the unit under test, typically .2, .5, .8 and .95 of the Nyquist frequency (Fo). To determine the Nyquist frequency you need to first determine the IFOV of your camera. If you need assistance in determining your sensor’s IFOV, please see our Calculate IFOV page.