A comparison of Landolt C and triangle resolution targets using the synthetic observer approach to sensor resolution assessment

Resolution is often provided as one of the key parameters addressing the quality capability of a sensor. One traditional approach to determining the resolution of a sensor/display system is to use a resolution target pattern to find the smallest target size for which the critical target element can be "resolved" using the sensor/display system, which usually requires a human in the loop to make the assessment. In previous SPIE papers we reported on a synthetic observer approach to determining the point at which a Landolt C resolution target was resolved; a technique with marginal success when compared to human observers. This paper compares the results of the previously developed synthetic observer approach using a Landolt C with a new synthetic observer approach based on Triangle Orientation Detection (TOD). A large collection of multi-spectral (visible, near infra-red, and thermal) sensor images of triangle and Landolt C resolution targets were recorded at a wide range of distances. Each image contained both the triangle and the Landolt C resolution targets as well as a person holding a weapon or other object. The images were analyzed using the two different synthetic observer approaches, one for triangles and one for Landolt Cs, and the results compared with each other for the three different sensors. This paper describes the results and planned future effort to compare the results with human visual performance for both the resolution targets and for the hand-held objects.