Optical pickup device, track discrimination signal detection method and optical recording medium recording and reproducing apparatus

摘要

PROBLEM TO BE SOLVED: To form a track identification signal even when an optical recording medium adopting a 'land and groove system', such as, for example, a 'DVD- REAM' or 'DVR', is used without increasing the number of parts and without complicating the constitution of parts. SOLUTION: Main spots for performing recording and reproducing and sub- spots parted from the main spots are formed on an optical disk 101. Astigmatism is added to the sub-spots by a hologram element 17 which is an astigmatism adding means. Differences appear in the intensity distribution of return light depending upon whether the spots exist on the land parts or groove parts by the astigmatism and therefore the track identification signal is formed by detecting this differences.