IMAGE FORMATION APPARATUS
An image formation apparatus comprising: an illumination system operable to direct a radiation beam onto a first plane; a first support structure operable to support a first marker in the first plane and a second support structure operable to support a second marker in a second plane; a projection system arranged between the first and second planes so as to form a combined image of the first and second markers in a third plane; and an alignment system operable to extract data from the combined image to determine an alignment distance between the first and second markers.