Summary

The work reported here is an extension of earlier work on a statistical theory of visual thresholds. Experiments are reported in which the quantum noise limitation of visual thresholds is explored further by the deliberate addition of noise to the test patterns presented to the observers. A theoretical framework is developed to account for the influence of this noise and it is found that empirical observations show the principal characteristics predicted by this theoretical framework. This appears to confirm the validity of this approach to visual thresholds. It also provides a convenient means for predicting the response of the eye when used to observe the output of any imaging system in which noise is present

322 Session No. 7 Pattern Recognition I General Papers RECOGNITION OF HAND-PRINTED NUMERALS REDUCED Abstract TO GRAPH-REPRESENTABLE FORM

A method for reducing hand-printed characters to directed graphs is described. When hand-printed characters are reduced to this form, area zoning techniques which have been successfully applied in real time environments can be used. Alternatively, the data in this form can be used to generate descriptions in a simple character-description language. 1

Session No. 7 Pattern Recognition I General Papers 333 VISUAL DETECTION OF NOISY PATTERNS

Experiments are reported in which the quantum noise limitation of visual thresholds is explored further by the addition of noise to test patterns presented to the observers. The results show the characteristics predicted by a statistical theory of vision developed to account for the influence of the added noise, which was reported earlier. In particular, these measurements make it possible to calculate independent values for quantum efficiency and for Rose's factor of certainty. List of Symbols the area of summation of the eye the effective area of the stimulus (se