High-Track-Density Optical Disc by Radial Direction Partial Response

We propose a new recording method, the radial direction partial response (RPR), with which we are able to use a narrow track pitch. This method can be used only for optical read-only-memory discs. We present experimental results of this method combined with the multilevel recording technique called “single carrier independent pit edge recording” (SCIPER). (The combined method is called SCIPER-RPR). When a track pitch of 0.45 µm and 0.28 µm/bit in linear recording density is read out by a digital versatile disc (DVD) equivalent optical pickup, we confirmed a bit error rate of 1.5×10-4.