Image of optical diffraction radiation (ODR) source and spatial   resolution of ODR beam profile monitor
  The approach to obtain the image shape of an optical diffraction radiation (ODR) source focused by lens on a detector with taking into account the "pre-wave zone" effect has been developed. In full analogy with optical transition radiation source the characteristic size of ODR slit image doesn't depend on the Lorentz-factor and is defined by slit width, wavelength and lens aperture. If a beam is passed through a narrow slit the shape of a slit image depends on a beam size. ODR generated by extremely ultrarelativistic beam passing through a narrow slit may be used to determine the beam size from ODR slit image. 
A.P. Potylitsyn