The invention relates to a device and a method for exposing photosensitive plates (33) for printing presses, comprising controlled laser exposure apparatus and a conveyor system for moving forward the photosensitive plates. The problem with the plate exposers at present is that they are not sufficiently accurate. A device is therefore provided whereby the controlled laser exposure apparatus (63) comprises means (1, 20) for measuring and compensating the variances in the laser beam orientation. The controlled laser exposure apparatus (63) comprises a software control (21). Another problem is that one laser source cannot bridge the scanning of photosensitive plates (200) with great width. Two laser sources (2) synchronised with each other are therefore provided. The invention further relates to a housing for a device such as specified above.