ABSTRACT
This chapter introduces metrics for measuring subjectively the visual performance and some objective metrics that take into account properties of the neural visual system. Measures of optical quality and optical performance are objective methods. The simplest metric for optical quality is any of the aberration coefficients, which will inform of the amplitude of a particular aberration. A single coefficient does not capture the whole optical quality because other aberrations may also be present in varying degrees. Optical quality ensures image quality and, therefore, a correct visual performance. New objective metrics that incorporate some neural characteristics of the visual system have been proposed recently that correlate better with clinical measures of visual performance. Objective image quality metrics for evaluating processed images are preferred to subjective evaluation, which is slow and inconvenient for practical usage. Optical metrics have proven to be useful in many applications in vision.
