A reading device (400) to aid in viewing the image to be produced by illuminating a diffractive optical surface (100) to produce a diffracted beam. The device (400) includes a light source (402) to produce a laser beam which is directed through a lens system (403). The beam is directed to and illuminates a diffractive optical surface to produce a diffractive beam. The diffractive beam is intercepted by an image receiving surface (409). A user of the device could then view the image on the image receiving surface (409). To configure the machine (400) to provide a focused image onthe image receiving surface (409), a mirror is placed at the position of the diffractive surface to produce a "spot" on the surface (409), which spot can then be adjusted in respect of size and focus. This is achieved by altering the lens system and position at which it is engaged by the laser beam.
