Photon Folding for Imaging in Non-Focusing Telescopes

We present a new technique - photon folding - for imaging in non-focusing telescopes. Motivated by the epoch-folding method in timing analysis, the photon folding technique directly provides the statistical significance of signals in images, using projection matrices. The technique is very robust against common imaging problems such as aspect errors and non-uniform background. The technique provides a deterministic recursive algorithm for improving images, which can be implemented on-line. Higher-order photon folding technique allows a systematic correction for coding noises, which is suitable for studying weak sources in the presence of highly variable strong sources. The technique can be applied to various types of non-focusing telescopes such as coded-aperture optics, rotational collimators or Fourier grid telescopes.