<title>What eye model should we use for MRT testing?</title>

Abstract

In its current forni, the NVL model does not adequately predict the laboratory measured minimum resolvable temperature (MRT) values at low or high spatial frequencies. The differences between the measured and the predicted values are caused by inappropriate modeling of the eye, tremendous variability in observers, and ill-defined data analysis methodology. In the usual laboratory procedure, the observer is allowed to move his head. This, in effect, renioves the eye's response from the model because by adjusting his viewing distance, the observer appears to achieve equal detection capability at all spatial frequencies. Recent studies provide two new eye models: one allowing head movement and one in which the head is stationary. A NVL type model was modified to accept five different eye models: the original NVL eye model, the Sendall-Rosell model, the two new eye models, and the Campbell-Robson eye model. All the models provided the same shaped MRT curve at high spatial frequencies to within a constant. Large discrepancies exist at low spatial frequencies presumably due to the inability to model the eye's inhibitory response.