1. A device for merging a 2D radioscopy image with an image obtained from a 3D image data record, comprising: a memory unit that stores the 2D radioscopy image and the 3D image data record; a segmentation unit that segments a surface to be displayed from the 3D image data record; a registration unit that registers the 2D radioscopy image with the 3D image data record; a back-projection unit that back-projects pixels of the 2D radioscopy image onto the segmented surface taking account of a projection geometry of the 2D radioscopy image and the registration; and an image merger unit that generates a virtual endoscopy view of the surface from the segmented surface using the back-projected pixels, wherein a viewing point or an angle of aperture or a viewing direction of the image display do not correspond to a viewing point or an angle of aperture or a viewing direction of the 2D radioscopy image.