Two-Step Technology for Improving Details of Images Captured with Mobile Devices

In this study, we developed a two-stage technology for improving the sharpness of images. In the first stage, the correction was performed using a linear square exponential (SE) filter with a centrally symmetric frequency response in the form of quadratic and exponential functions. This stage included setting the parameters of the SE filter and the actual processing. In the second stage, non-linear correction was carried out. The idea of the filter was to increase the impact of the central value, if it was at the edge of different intensity levels. We assumed that an increase in the absolute value of the weighted average of the differences in the point neighbourhood could be an indicator of such edges. The central point of the reference area belonged to the edge if its value was considerably greater or lesser than the significant number of values in this area. The first experiment confirmed the possibility for the improvement of the quantitative criteria of image restoration by non-linear correction. The second experiment illustrated the increase in the image sharpness obtained using a diffraction Fresnel lens. The proposed technology has opened up prospects for the use of cameras based on diffraction optic elements in mobile devices.