PURPOSE To assess the accuracy of human blood oximetry measurements in a model eye with a hyperspectral fundus camera. METHODS Seven human whole blood samples (two arterial, five venous) were obtained, the oxygen saturations measured with a CO oximeter, and the samples inserted into quartz tubes with internal diameters of 100 and 150 μm. The tubes (n =… (More)
We describe the mapping of the optical transfer function (OTF) of an incoherent imaging system into a geometrical representation. We show that for defocused traditional and wavefront-coded systems the OTF can be represented as a generalized Cornu spiral. This representation provides a physical insight into the way in which wavefront coding can increase the… (More)
A quartic phase retardation function is described that reduces the variation of the intensity of the focal point of incoherent imaging systems suffering from primary third-order aberrations limited to coma and astigmatism. Corresponding modulation transfer functions are shown to remain practically invariant for moderate amounts of coma and astigmatism.
The design of modern imaging systems is intricately concerned with the control of optical aberrations in systems that can be manufactured at acceptable cost and with acceptable manufacturing tolerances. Traditionally this involves a multi-parameter optimisation of the lens optics to achieve acceptable image quality at the detector. There is increasing… (More)
Wavefront coding involves the insertion of an asymmetric refractive mask close to the pupil plane of an imaging system so as to encode the image with a specific point spread function that, when combined with decoding of the recorded image, can enable greatly reduced sensitivity to imaging aberrations. The application of wavefront coding has potential in the… (More)
Optical coherence tomography (OCT) and reflectance imaging are used in clinical practice to measure the thickness and transverse dimensions of retinal features. The recent trend towards increasing the field of view (FOV) of these devices has led to an increasing significance of the optical aberrations of both the human eye and the device. We report the… (More)
We present a comprehensive study of the effect of detector sampling on wavefront-coded systems. Two important results are obtained: the spurious response ratios are reduced in wavefront-coded systems with a cubic phase mask and detector sampling does not compromise the restoration of wavefront-coded images with extended depth of field. Rigorous computer… (More)
A novel insight into the fundamental principles of wavefront coding is described; we show that the optical transfer function can be considered in terms of a generalised Cornu spiral and consequently important performance parameters can be derived in a greatly simplified and informative manner from the geometry of such a spiral. Introduction Recent years… (More)