An artist’s easel having four legs that are pivoted at their upper ends on a pivot housing so that the lower ends can be spread to support an artist’s board or collapsed to a position in which they are adjacent one another. The spring may be a metal mechanical spring or formed of a resiliently flexible material, particularly a polymeric material. In order to be independent of the nature and location of the diffraction pattern, the diffraction pattern derived from the document to be examined is projected onto a screen and the image of the pattern recorded and evaluated by a camera. The unfolding of the pleats controls a deployment trajectory of the front wall, and the pleats have an undulating transverse curve length corresponding to a maximum trajectory of the front wall.