Chromatic aberration and ocular focus: Fincham revisited

Kruger, Philip B.; Mathews, Steven; Aggarwala, Karan R.; Sanchez, Nivian

doi:10.1016/0042-6989(93)90046-y

Cited by 127 publications

(128 citation statements)

References 66 publications

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“…The term for the point-spread function in Eq. 2 can be expanded to make the factors determining its form more explicit, psf ðx; λ; aðz; λÞ; W ðz; λ; ΔDÞÞ; [3] where aðz; λÞ specifies the shape, size, and transmittance of the pupil aperture, and W ðz; λ; ΔDÞ is a wave aberration function, which depends on the position z in the plane of the aperture, the wavelength of light, the defocus level, and other aberrations introduced by the lens system (15). The aperture function determines the effect of diffraction on the image quality.…”

Section: Resultsmentioning

confidence: 99%

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Optimal defocus estimation in individual natural images

Burge

Geisler

2011

Proc. Natl. Acad. Sci. U.S.A.

134

126

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Defocus blur is nearly always present in natural images: Objects at only one distance can be perfectly focused. Images of objects at other distances are blurred by an amount depending on pupil diameter and lens properties. Despite the fact that defocus is of great behavioral, perceptual, and biological importance, it is unknown how biological systems estimate defocus. Given a set of natural scenes and the properties of the vision system, we show from first principles how to optimally estimate defocus at each location in any individual image. We show for the human visual system that highprecision, unbiased estimates are obtainable under natural viewing conditions for patches with detectable contrast. The high quality of the estimates is surprising given the heterogeneity of natural images. Additionally, we quantify the degree to which the sign ambiguity often attributed to defocus is resolved by monochromatic aberrations (other than defocus) and chromatic aberrations; chromatic aberrations fully resolve the sign ambiguity. Finally, we show that simple spatial and spatio-chromatic receptive fields extract the information optimally. The approach can be tailored to any environment-vision system pairing: natural or man-made, animal or machine. Thus, it provides a principled general framework for analyzing the psychophysics and neurophysiology of defocus estimation in species across the animal kingdom and for developing optimal image-based defocus and depth estimation algorithms for computational vision systems.optics | sensor sampling | Bayesian statistics | depth perception | auto-focus

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Section: Resultsmentioning

confidence: 99%

“…Thus, defocus information is nearly always present in images of natural scenes. Defocus information is vital for many natural tasks: depth and scale estimation (1,2), accommodation control (3,4), and eye growth regulation (5,6). However, little is known about the computations visual systems use to estimate defocus in images of natural scenes.…”

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confidence: 99%

Optimal defocus estimation in individual natural images

Burge

Geisler

2011

Proc. Natl. Acad. Sci. U.S.A.

134

126

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“…The colour fringes are the result of the eye's longitudinal chromatic aberration. The theoretical basis for the chromatic control hypothesis involves either or both of the red-green (R-G) and yellow-blue (Y-B) opponent processes (Flitcroft, 1990;Kruger et al 1993).…”

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confidence: 99%

Red‐green opponent channel mediation of control of human ocular accommodation.

Kotulak

Morse

Billock

1995

The Journal of Physiology

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1. It has been hypothesized, but not verified empirically, that the control of human ocular accommodation is mediated by either the red‐green or yellow‐blue colour channels. Our goal was to determine experimentally whether the red‐green channel by itself could influence the accommodative response. 2. To find out, we isolated the red‐green channel through chromatic bandpass filtering and measured accommodation under dynamic and static conditions. The effect of this filtering was to modulate the red‐green channel without disturbing either the yellow‐blue or luminance channels. 3. Accommodative gain (ratio of response to stimulus amplitude) declined monotonically with decreasing bandwidth under dynamic conditions. Because the outputs of both the luminance and yellow‐blue colour channels did not vary with bandwidth, the only explanation is that the red‐green opponent process was responsible for the effect. 4. Under static conditions, however, accommodation was independent of bandwidth. This may be attributable to the decreased sensitivity to chromatic contrast that occurs at low temporal frequencies.

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“…Sinusoidally moving targets have been used routinely in accommodation research8, 21, 22 because they provide a stringent method of examining the stimulus to accommodation. It has been argued that the predictable rhythmical change in the appearance of the target that accompanies sinusoidal changes in optical vergence can evoke anticipation that increases response gain and decreases phase lag 8, 23, 24.…”

Section: Discussionmentioning

confidence: 99%

“…During monocular viewing, many factors can serve as directional cues for the visual system, such as apparent distance and size,3 chromatic aberration of the eye1, 4, 5 and microfluctuations of accommodation 6, 7, 8. Monochromatic aberrations also may be used to determine the direction of defocus, since even‐order aberrations such as astigmatism and spherical aberration form a different point spread function (PSF) depending on the sign of defocus (whether images are formed behind or in front of the photoreceptors layer) 9…”

Section: Introductionmentioning

confidence: 99%

Human eyes do not need monochromatic aberrations for dynamic accommodation

Bernal-Molina

Marín-Franch

Águila-Carrasco

et al. 2017

Ophthalmic Physiologic Optic

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PurposeTo determine if human accommodation uses the eye's own monochromatic aberrations to track dynamic accommodative stimuli.MethodsWavefront aberrations were measured while subjects monocularly viewed a monochromatic Maltese cross moving sinusoidally around 2D of accommodative demand with 1D amplitude at 0.2 Hz. The amplitude and phase (delay) of the accommodation response were compared to the actual vergence of the stimulus to obtain gain and temporal phase, calculated from wavefront aberrations recorded over time during experimental trials. The tested conditions were as follows: Correction of all the subject's aberrations except defocus (C); Correction of all the subject's aberrations except defocus and habitual second‐order astigmatism (AS); Correction of all the subject's aberrations except defocus and odd higher‐order aberrations (HOAs); Correction of all the subject's aberrations except defocus and even HOAs (E); Natural aberrations of the subject's eye, i.e., the adaptive‐optics system only corrected the optical system's aberrations (N); Correction of all the subject's aberrations except defocus and fourth‐order spherical aberration (SA). The correction was performed at 20 Hz and each condition was repeated six times in randomised order.ResultsAverage gain (±2 standard errors of the mean) varied little across conditions; between 0.55 ± 0.06 (SA), and 0.62 ± 0.06 (AS). Average phase (±2 standard errors of the mean) also varied little; between 0.41 ± 0.02 s (E), and 0.47 ± 0.02 s (O). After Bonferroni correction, no statistically significant differences in gain or phase were found in the presence of specific monochromatic aberrations or in their absence.ConclusionsThese results show that the eye's monochromatic aberrations are not necessary for accommodation to track dynamic accommodative stimuli.

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Chromatic aberration and ocular focus: Fincham revisited

Cited by 127 publications

References 66 publications

Optimal defocus estimation in individual natural images

Optimal defocus estimation in individual natural images

Red‐green opponent channel mediation of control of human ocular accommodation.

Human eyes do not need monochromatic aberrations for dynamic accommodation

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