| 摘要 |
PURPOSE:To enable a light spot to follow a track correctly by setting equidistances so as to be prescribed distances different from each other for every image forming means when a pair of second light spots deviated by the equidistance to both sides from a segment of a line passing through the center of a first light spot and parallel with the track are generated. CONSTITUTION:Light spectral-separated by a diffraction grating 2 arranged between a light source 1 and a half mirror 7 is image-formed by a lens 4 through the half mirror 7 and the lens 3. At that time, the light from the light source 1 is spectral-separated so that a pair of the second spots B1, B2 deviated by equidistance from the segment of a line passing through the center of the light spot A and parallel with the track of the disk 50 at the front and the rear of the light spots A lying along the track of the disk 50 are formed on an optical disk 50. Then, this equidistance is set so as to be the prescribed distance different from each other for every image forming means. Thus, the first light spot can be made to follow correctly the information track of different width. |
