An apparatus for generating and displaying an image of an object comprising a radiation source and a series of at least two linear detectors capable of resolving incident source radiation spectroscopically spaced therefrom to define a scanning zone therebetween; means to cause an object to move relative to and through the scanning zone in use; an image generation apparatus to generate at least a first image from the output of a first linear detector, a second image from the output of second linear detector, and a third image, such that each such image includes a representation of spectroscopically resolved incident radiation; an image display adapted successively to display at least the first, second and third such images and thus display the monocular movement parallax between the images.