Optical recording method, optical recording device, master medium exposure device, optical information recording medium, and reproducing method

Abstract

An optical recording method for recording information by irradiating an optical disc medium with a modulated write pulse train of laser light variable over a plurality of power levels such that a plurality of marks are formed on the optical disc medium, edge positions of each of the marks and a space between adjacent two of the marks being utilized for recording of the information. The optical recording method includes the steps of: encoding record data to generate encoded data which is a combination of marks and spaces; classifying the encoded data according to a combination of a mark length of the mark, a space length of a first space that immediately precedes the mark, and a space length of a second space that immediately succeeds the mark; generating a write pulse train for forming the mark, in which at least one of a leading end edge position, a trailing end edge position and a pulse width of the write pulse train is changed according to a classification result; and irradiating the optical disc medium with the write pulse train generated to form the plurality of marks on the optical disc medium.

Description

[0001]This application is a continuation of U.S. patent application Ser. No. 12 / 918,108 filed on Aug. 18, 2010, which is hereby incorporated herein by reference in its entirety, and which is a §371 of PCT / JP2009 / 005141 filed Oct. 5, 2009.TECHNICAL FIELD[0002]The present invention relates to an optical recording method, an apparatus for manufacturing a master through an exposure process (master-manufacturing exposure apparatus), an optical information recording medium, and a reproduction method, which utilize maximum likelihood decoding, such as PRML, an optical recording apparatus. More particularly, the present invention relates to a technique of writing under the optimum recording conditions by making adaptive recording compensation at least according to the space lengths of spaces preceding and succeeding an interested mark, for the purpose of decreasing optical intersymbol interference or thermal interference which is caused in recording of or reproduction from a mark or pit suf...

AI Technical Summary

Benefits of technology

"The present invention relates to an optical recording method and apparatus that use maximum likelihood decoding to decrease intersymbol interference caused by thermal interference or optical interference in recording or reproducing optical information. The invention also includes a technique of writing under the optimum recording conditions by making adaptive recording compensation at least according to the space lengths of spaces preceding and succeeding an interested mark. The invention can be applied to optical disc media such as BDs and DVDs, and can increase the recording density by decreasing the length of marks and spaces."

Problems solved by technology

However, especially when the length of a space with a preceding record mark becomes shorter, thermal interference occurs such that the heat at the trailing end of the recorded mark is conducted via a space portion to affect the increase in temperature at the leading end of a succeeding mark and, on the other side, the heat at the leading end of the recorded mark affects the cooling cycle at the trailing end of a preceding mark.

Even when marks and spaces formed on a track have correct lengths, edge positions of short marks and spaces which are detected in reproduction are disadvantageously different from their ideal values due to the frequency characteristics of a reproduction optical system which depend on the size of the light spot.

When the sizes of marks and spaces are smaller than the light spot, large intersymbol interference occurs, and accordingly, the jitter in reproduction is increased, so that the bit error rate is increased.

In recent years, the higher densities of optical disc media cause the lengths of record marks to come closer to the optical resolution limit, so that increase in intersymbol interference and deterioration in SNR (Signal to Noise Ratio) become larger.

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