Encoding and detecting apparatus

An apparatus for determining a data word represented by a plurality of code words recovered from a marked material item, the data word including at least two fields, a first of the plurality of code words being associated with a value of a first of the at least two fields and a second of the plurality of code words being associated with a value of a second of the at least two fields in a dependence upon the value of the first of the at least two fields, the apparatus comprising:

• means for re-generating selectively each first code word of the plurality of code words associated with a possible value of the first of the at least two fields;
• means for arranging for re-generated first code words to be correlated with the recovered code words in a first correlation, each of the first code words being independently generated from a different code word seed;
• means for identifying from a result of the first correlation, the value of the first of the at least two fields:
• means for re-generating selectively each second code word of the plurality of code words associated with a possible value of the second of the at least two fields, and selected in a dependence upon the value of the first of the at least two fields;
• means for arranging for re-generated second code words to be correlated with the recovered code words in a second correlation;
• and
• means for identifying from a result of the second correlation, the value of the second field of the at least two fields.

A method, for a code word detecting apparatus, of determining a data word represented by a plurality of code words recovered from a marked material item, the data word including at least two fields, a first of the plurality of code words being associated with a value of a first of the at least two fields and a second of the plurality of code words being associated with a value of a second of the at least two fields in a dependence upon the value of the first of the at least two fields, the method comprising:

• re-generating, with the code word detecting apparatus, selectively each first code word of the plurality of code words associated with a possible value of the first of the at least two fields;
• arranging, with the code word detecting apparatus, for re-generated first code words to be correlated with the recovered code words in a first correlation, each of the first code words being independently generated from a different code word seed;
• identifying, with the code word detecting apparatus, from a result of the first correlation, the value of the first of the at least two fields;
• re-generating, with the code word detecting apparatus, selectively each second code word of the plurality of code words associated with a possible value of the second of the at least two fields and selected in a dependence upon the value of the first of the at least two fields;
• arranging, with the code word detecting apparatus, re-generated second code words to be correlated with the recovered code words in a second correlation;
• and
• identifying, with the code word detecting apparatus, from a result of the second correlation, the value of the second of the at least two fields.

A detecting data processing apparatus operable to determine at least one data word from code words recovered from a marked material item, the at least one data word including at least two fields, values of a first of the at least two fields being associated with a first set of code words, values of a second of the at least two fields being associated wit a second set of code words, the second set of code words being selected in a dependence upon a value of the first of the at least two fields, the detecting apparatus comprising:

• a code word re-generator operable to re-generate code words each having a plurality of code word coefficients and being independently generated from a different code word seed;
• a correlator operable to correlate the re-generated code words with the recovered code words;
• and
• a control processor operable to control the code word re-generator to re-generate selectively each first code word associated with a possible value of the first of the at least two fields, to arrange for re-generated first code words to be correlated with the recovered code words in a first correlation, to identify, from a result of the first correlation, the value of the first of the at least two fields, to re-generate selectively each second code word associated with a possible value of the second of the at least two fields and selected in a dependence upon the value of the first of the at least two fields, to arrange for re-generated second code words to be correlated with the recovered code words in a second correlation, and to identify, from a result of the second correlation, a value of the second of the at least two fields.