The above results were evidence that the point sources were produced by light reflecting from the cone photoreceptor apertures: the LSO/MSA combination was imaging the cone mosaic. By fitting an additional, high-intensity fixation target to the cLSO it was shown that the point structures were located at the focal plane at which light is trapped into the visual system. The point sizes and spacings were compatible with those found in anatomical studies and it was shown that point spacing increased with increasing retinal eccentricity-a fact which was also predicted from anatomical studies. Experiments were undertaken to confirm the point structures corresponded to cone photoreceptor apertures. Arrays of point-like structures could then be identified in the final, processed images.
Image of unequal pupil size software#
Many individual frames from a single imaging sequence were aligned and averaged using novel image processing software to improve the signal to noise ratio. The video output of the cLSO was digitised using a high-speed, low-noise video frame grabber. The attachment reduced the field of view of the cLSO to approximately three degrees of visual angle at the retina but also reduced the amount of light returning to the imaging detector and consequently lowered the signal to noise ratio. An optical attachment to an existing prototype cLSO was designed and constructed. This thesis describes a project to image the human retina in vivo using a modified confocal laser scanning ophthalmoscope (cLSO). The results are compared to the state-of-art methods, showing the superiority of DPFR over the others in terms of restoration quality and implementation efficiency.
Six image quality matrixes including image definition, image sharpness, image local contrast, image multiscale contrast, image entropy, and fog density are used for objective assessments. Moreover, the DPFR method is tested on 906 images from five public databases. Each step of DPFR is tested experimentally with retinal images of different degraded situations to validate its robustness.
Image of unequal pupil size how to#
While a solution about how to bypass the challenge is proposed. The failure of the dark channel prior on retinal images in RGB color space is clarified. Based on the DPFR model, the procedures of the proposed retinal image restoration algorithm are given. The DPFR model reveals the specific double pass fundus reflection feature that was hitherto neglected in modeling the light propagation of fundus imaging in all published reports on retinal image enhancement. This study introduces a novel image formation model - the double pass fundus reflection (DPFR) model for retinal image enhancement (restoration). Third, the technique provides a means for inferring the complete optical transfer function of the eye, including the phase transfer function, and the shape of the point-spread function. The measured image quality was unchanged when the pupils were interchanged, i.e., when the first-pass entrance pupil size becomes the second-pass exit pupil size, and vice versa. To test for reversibility in the living eye we have used a double-pass apparatus with different exit and entrance pupil sizes (one of them small enough to consider the eye diffraction limited), so that the ingoing and the outgoing transfer functions are different. That is, when entrance and exit pupils are equal, the double-pass image results from two passes through an optical system having a transfer function that is the same in both directions. Second, we show that in double-pass measurements the eye behaves like a reversible optical system. Consequently, when entrance and exit pupil sizes are equal, phase information is lost from the double-pass images. First, we confirm that in the eye the double-pass spread function is the cross correlation of the input spread function with the output spread function. We have used a modified double-pass apparatus with unequal entrance and exit pupil sizes to measure the optical transfer function in the human eye and have applied the technique to three different problems.
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