Programmable freeform optical elements

Abstract

Modern liquid crystal spatial light modulators (SLMs) are capable of shifting the optical path length by some microns, which corresponds to phase shifts of several multiples of 2π. We use this capability to display freeform optical elements (FOEs) on a SLM, as largely smooth phase variations with only a small number of wrapping lines. These FOEs can be programmed to generate so-called caustic intensity distributions, which may be real images reconstructed at a selected position in front of the SLM surface. In contrast to standard diffractive structures, reconstruction of the freeform images is non-dispersive (i.e. white light images can be programmed), free of speckle, and its efficiency does not depend on the wavelength. These features promise novel applications in image projection, and various application fields of SLMs in microscopy.

Modelling of the backside pattern transfer in magic mirror (Makyoh) imaging

“…It has been suggested by several authors [4,26,27] that Makyoh is a special kind of 'optical processing element' where a wavefront is modified by the subwavelength relief of a globally planar reflecting surface. This approach leads to the realm of freeform optics where Laplacian or magic-mirror imaging is often d [21,28].…”

Modeling classical wavefront sensors

“…(3). These small amounts render the diffraction effects, although not considered easy for wavefront sensing via the inversion numerical scheme in §5.1.2, could be helpful to forward modeling in freeform lens designs for caustic imaging [24,53,54] to reduce blurring artifacts.…”

Enhanced chemical etch rate of borosilicate glass via spatially resolved laser-generated color centers

“…The relatively simple intensity pattern of a ring was chosen for a test window. By solving the Poisson's equation in the manner given in [43][44][45], one can calculate the corresponding surface relief (Fig. 9a).…”

“…Such an optical element has a freeform surface, whose effect on the light passing thorough it is defined by the value of the Laplace operator of its sur face relief. In order to calculate the surface relief reproducing the desired intensity distribution one thus needs to solve the Poisson's equation [43][44][45].…”

“…The relatively simple intensity pattern of a ring was chosen for a test window. By solving Poisson's equation in the manner given in [43][44][45], one can calculate the corresponding surface relief (figure 9(a)). It should be noted here that the absolute values of the surface depth do not play an important role; it is the aspect ratio of XY size to depth that defines the local radius of curvature and hence whether the Laplacian condi tion is fulfilled [43,44].…”