associated with controlling electrodes in such a system the diffraction of rays entering the modulator is at its maximum when electrodes affecting each pixel exhibit a substantial difference of potential in this case higher order rays are directed to a stop screen or diaphragm where they are blocked and no image of sufficient intensity reaches the recording medium e g printing plate precursor reversibly the maximum intensity of radiation reaches the recording medium when no significant difference of potential is exhibited between controlling electrodes in the arrangement shown in fig2 and 3 a cylindrical aspherical lens 4 accurately located in front of laser bar 2 collimates u201c fast u201d rays located on a plane perpendicular to the junction plane of the diode laser the u201c smil u201d representing the deformation of the bar at assembly of the bar is well within u00b1 1 u03bcm a telecentric objective 6 comprising several cylindrical lenses makes an image 8 about three times smaller than the emitting area length of the laser diode in the plane of the bar 2 which is also the plane of the modulator 14 as shown a group of two cylindrical lenses 10 having their focal point on the image plane 8 collimate the beams to the modulator 14 a cylindrical lens 12 focalizes the u201c fast axis u201d rays on the active zone of the modulator 14 at the output of the collimator 10 a spherical lens 16 reproduces at its focal point a second image now modulated of the light source on slit 18 of stop plate 34 whose purpose is to separate diffraction orders another objective 20 which comprises a plurality of lenses.