a straight line beam scanner 20 will be given first a description will now be given of the straight line beam scanner 20 and the hologram disk 21 in fig3 a divergent wave 23 from the laser diode 21 is wavefront transformed into an incident wave 25 on the disk 21 by the holographic lens 24 then the incident wave 25 is transformed into scanning beam 26 by the phase transfer function of the disk 21 and straight line scanning is performed the hologram disk 21 includes a plurality of interferometric zone plates izp 21a having an interference fringe shape generated by interfering the coherent plane and spheric waves having wavelengths shorter than the semiconductor laser 22 with each other the hologram disk 21 is segmented into a plurality of zones in a circumferential direction when a light is projected as a reconstructed light which is a divergence wave from the semiconductor laser 22 onto the hologram disk 21 a scanning beam 26 as a diffraction light forms an image on the photoconductor drum 27 by a number of zones per one rotation of the izp 21a fig4 shows parameters for a straight line scanning holographic disk using a divergent spherical wave as the reference wave the reconstructed wave is a convergent.