High-resolution photorefractive incoherent-to-coherent optical converter

We demonstrate a novel photorefractive incoherent-to-coherent optical converter in which there is a ∼45° angle between the propagation direction of the incoherent image and the grating vector. Thus the number of the grating periods in one pixel is large even for a very high resolution. When the output image has the same direction with the incoherent incident beam, the resolution does not depend on the interaction length between the incoherent beam and the grating. A resolution as high as 283 line pairs/mm, which is the resolution of out projection system, is obtained for a one-dimensional resolution target. Two-dimensional incoherent-to-coherent conversion is also demonstrated.