Point spread function (PSF) theory has been demonstrated as proof of concept in evaluation of spatial resolution of three dimensional imaging technology like optical coherence tomography (OCT) and confocal microscopy. A robust test target and associated evaluation algorithm are in demand for keeping regular quality assurance and inter-comparison of such 3D imaging system performance. To achieve this goal, standard-size micro spheres were utilized to develop PSF phantoms. The OCT system was investigated with the microsphere PSF phantom. Differing from previous study, a statistical model comprising data from hundreds of scatterers was established to acquire the PSF distribution and variation. The research provided an effective method and a set of practical standard phantoms for evaluating resolution of three dimensional imaging modalities.
The color discrimination is a powerful tool for detection of eye diseases, and it is is necessary to produce different kinds of color rapidly and precisely for testing color discrimination thresholds of human eyes. Three channels’ pulse-width modulation (PWM) and light-mixing technology is a new way to mixing color, and a new measurement method for color discrimination thresholds of human eyes based on PWM light-mix technology can generate kinds of color stimuli. In this study, 5 youth volunteers were measured via this equipment after the test for the stability of the device’s illumination and chrominance. Though the theory of Macadam ellipses and the interleaved staircase method, a psychophysical experiment was made to study the color discrimination threshold of the human eyes around a basic color center. By analyzing the data of the chromatic ellipse and the color discrimination threshold, the result shows that each color is not uniform in a single color region and the color difference threshold of normal human is around the third Macadam ellipses. The experimental results show that the repeatability and accuracy of the observer can meet the accuracy requirements of the relevant experiments, and the data is reliable and effective, which means the measurement method is an effective way to measure the color discrimination thresholds of human visual system.
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