Home – Home – Jornals – Avtometriya 2025 number 2

Image quality assessment is crucial in the design of optical systems with an increased depth of the field and containing axicons, which possess two caustics, retain the linearity property but are spatially variant, creating difficulties for their analysis. We propose to consider the images formed by each of the caustics within the framework of the linear systems theory. A theoretical analysis of image formation is performed and PSFs are found for three optical systems in which toroidal light waves are formed by means of the axicon, as well as multiple experiments are carried out to determine the resolving power of such systems. As a result, it is shown that the axicon produces an image of a single object as a continuous set of ‘intermediate’ images along the focal segment. Light beams incident from the object to the centre of the axicon produce an image in the immediate vicinity of the axicon, while beams incident to the periphery of the axicon produce an image at the periphery of the focal segment. In doing so, all these low-contrast images mask each other. The lens-axicon tandem simultaneously produces images of the object both at the near diffraction zone in the form of a set of ‘intermediate’ images and at the far zone in a geometrically transformed form. Moreover, in the near diffraction zone, the depth of the field imaged by the tandem can exceed the depth of the field imaged by the single objective. The experimental data confirm the theoretical conclusions.