Just-Noticeable Levels of Aberration Correction

Abstract

Purpose: The objectives of this study were to determine whether the correction of higher-order aberrations (HOA) would be detectable by “normal” subjects and whether a full correction is necessary or better than a partial correction of the main HOA (i.e., spherical aberration (SA), coma and trefoil). Methods: Three subjects made side-by-side comparisons between an uncorrected aberrations image (i.e., including typical HOA) and partially corrected variant images in order to determine which image was subjectively preferred. Results: The subjective preference was found to be well correlated (r2=0.84) with the volume under the modulation transfer function (VMTF). A significant difference of subjective preference was found with change of SA correction (P=0.014) and with change of coma correction (P=0.009) but not with the correction of trefoil (P=0.133). Changing the VMTF by less than 6.3% did not induce a perceptible difference (i.e., subjective preference higher than 25%) whereas changing the VMTF by more than 10% often induced a perceptible difference. Moreover, based on the through-focus subjective preference curve, we obtained a just-noticeable level of defocus of 1/8 D. Conclusions: The subjective quality of vision of a subject with typical aberrations could be improved by either a partial (50%) or a full correction of both SA and coma, this gain being comparable to 1/8 D of defocus blur. However, the effect of the correction of the trefoil appears negligible. The VMTF is a good image quality metric to predict subjective preference. A perceptible difference in image quality can be obtained by changing the VMTF by 6.3 to 10%.

Keywords

• simulation
• tolerance
• aberration
• image quality
• adaptive optics