Christopher Dainty

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It is fairly well established that the higher-order aberrations of the eye fluctuate over relatively short time periods, but as yet there is no conclusive evidence regarding the origin of these fluctuations. We measured the aberrations and the pulse pressure wave simultaneously for five subjects. The aberrations were measured by using a Shack-Hartmann(More)
A high-resolution retinal imaging camera is described that uses a Shack-Hartmann wave-front sensor and a Fourier deconvolution imaging technique. The operation of the camera is discussed in detail and high-resolution retinal images of the human cone mosaic are shown for a retinal patch approximately 10 arc min in diameter from two different retinal(More)
We present a practical method for reconstructing the optical system of the human eye from off-axis wavefront measurements. A retinal beacon formed at different locations on the retina allows probing the optical structure of the eye by the outgoing beams that exit the eye through the dilated pupil. A Shack-Hartmann aberrometer measures the amount of wave(More)
The methodology of objective assessment, which defines image quality in terms of the performance of specific observers on specific tasks of interest, is extended to temporal sequences of images with random point spread functions and applied to adaptive imaging in astronomy. The tasks considered include both detection and estimation, and the observers are(More)
We measured the wavefront aberrations of the eyes of five subjects with a Shack-Hartmann sensor sampling at 21.2 Hz and decomposed the measurements into Zernike aberration terms up to and including the fifth radial order. Coherence function analysis was used to determine the common frequency components between the aberrations within subjects. We found the(More)
Maximum-likelihood (ML) estimation in wavefront sensing requires careful attention to all noise sources and all factors that influence the sensor data. We present detailed probability density functions for the output of the image detector in a wavefront sensor, conditional not only on wavefront parameters but also on various nuisance parameters. Practical(More)
The measurement of the strength of atmospheric optical turbulence by use of a modified generalized SCIDAR (scintillation detection and ranging) inversion technique is outlined and demonstrated. This new method for normalizing and inverting scintillation covariances incorporates the geometry specific to generalized SCIDAR. Examples of profiles from two(More)
Microfluctuations of accommodation have been the subject of many studies. New technological developments now permit us to study the dynamics of the microfluctuations with unprecedented resolution and accuracy. We aim to characterise their temporal statistics for different levels of accommodative effort, using a custom-built aberrometer. We conducted 46 s(More)
The time-evolution of ocular aberrations has been the subject of many studies, but so far there has been little discussion involving the modelling of the underlying temporal statistics. This paper presents a non-stationary modelling approach based on a coloured-noise generator, which can be applied to ocular aberration dynamics. The model parameters are(More)
The strength of optical turbulence, Cn2(z), 2-3 m above ground level, was measured as a function of distance along a 1.23-km path by the simultaneous capture of the scintillation from two infrared laser sources. The data collected differ in a number of important aspects from the normal vertical scintillation detection and ranging (SCIDAR) data in astronomy.(More)