US 6,388,970 B1Granted

Compensation for thermal effects in CD write strategy

AssigneeOak Technology, Inc.

InventorJin Iizuka

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Abstract

Method and system for compensating for thermal effects in writing and reading of mark and space characters on a CD-R/RW disk. Character lengths are measured for character triples (preceding mark, preceding space, present mark) on a disk, and a difference ΔL between present mark length and a reference mark length is computed for each of a selected group of combinations of preceding mark lengths and preceding space lengths. Mean values of ΔL are computed for each of these combinations. These mean values are interpreted as estimates of the thermal effects for the disk. Where the number of values of ΔL, for a given combination of preceding mark lengths and preceding space lengths, used to determine a mean value of ΔL is less than a threshold number, a selected algorithm is used to provide an adjusted mean value. Variation of thermal effects with disk write speed is determined and used in accounting for thermal effects. Frequency response effects of mark and space lengths are removed.

Claims18

Dependent claims

A method for compensating for thermal effects in mark lengths on a compact disk, the method comprising:

providing a sequence of alternating mark and space characters formed on a CD-R/RW disk;
measuring the lengths of selected consecutive triples of characters of a preceding mark, a preceding space and a present mark, denoted as L(PM), L(PS) and L(MK), respectively;
computing a difference Δm=ΔL(MK)/T between the length L(MK)/T and a reference length L0(MK)T=m0 for each of a selected sequence of combinations of the lengths m0, L(PM)/T=m1 and L(PS)/T=m2, and computing a mean value μ(Δm;m0;m1;m2) of the difference for each of the sequence of combinations, where T is a selected length value;
determining the number p of length measurements L(MK) used to determine the value μ(Δm;m0;m1;m2) for at least one combination of said lengths m0, m1 and m2;
when p is at least equal to a selected positive integer M1, accepting and storing said value μ(Δm;m0;m1;m2) as an estimate of thermal effects of character writing length for the at least one combination;
and
when p is less than M1, using a selected algorithm to determine an adjusted value μ′(Δm;m0;m1;m2), and accepting and storing said value μ′(Δm;m0;m1;m2) as an estimate of thermal effects of character writing length for the at least one combination.

4 more elements

A system for compensating for thermal effects in mark lengths on a compact disk, the system comprising a computer that is programmed:

to provide a sequence of alternating mark and space characters formed on a CD-R/RW disk;
to measure the lengths of selected consecutive triples of characters of a preceding mark, a preceding space and a present mark, denoted as L(PM), L(PS) and L(MK), respectively;
to compute a difference Δm=ΔL(MK)/T between the length L(MK)/T and a reference length L0(MK)/T=m0 for each of a selected sequence of combinations of the lengths m0, L(PM)/T=m1 and L(PS)/T=m2, and computing a mean value μ(Δm;m0;m1;m2) of the difference for each of the sequence of combinations, where T is a selected length value;
to determine the number p of length measurements L(MK) used to determine the value μ(Δm;m0;m1;m2) for at least one combination of said lengths m0, m1 and m2;
when p is at least equal to a selected positive integer M1, to accept and store said value μ(Δm;m0;m1;m2) as an estimate of thermal effects of character writing length for the at least one combination;
and
when p is less than M1, to use a selected algorithm to determine an adjusted value μ′(Δm;m0;m1;m2), and to accept and store said value μ′(Δm;m0;m1;m2) as an estimate of thermal effects of character writing length for the at least one combination.

4 more elements

Dependencies are inferred from the claim text.