Brazilian Journal of Medical and Biological Research
On-line version ISSN 1414-431X
SIMAS, M.L.B. and SANTOS, N.A.. Contrast sensitivity to radial frequencies modulated by Jn and jn Bessel profiles. Braz J Med Biol Res [online]. 2002, vol.35, n.11, pp. 1357-1366. ISSN 1414-431X. http://dx.doi.org/10.1590/S0100-879X2002001100014.
We measured human contrast sensitivity to radial frequencies modulated by cylindrical (Jo) and spherical (jo) Bessel profiles. We also measured responses to profiles of jo, j1, j2, j4, j8, and j16. Functions were measured three times by at least three of eight observers using a forced-choice method. The results conform to our expectations that sensitivity would be higher for cylindrical profiles. We also observed that contrast sensitivity is increased with the jn order for n greater than zero, having distinct orderly effects at the low and high frequency ends. For n = 0, 1, 2, and 4 sensitivity tended to occur around 0.8-1.0 cpd while for n = 8 and 16 it seemed to shift gradually to 0.8-3.0 cpd. We interpret these results as being consistent with the possibility that spatial frequency processing by the human visual system can be defined a priori in terms of polar coordinates and discuss its application to study face perception.
Keywords : Spatial frequency; Angular frequency; Polar gratings; Face perception; Contrast sensitivity.