Abstract 1. A method of producing a kinoform wherein the amplitude distribution function of a plurality of discrete picture elements of an image which is to be reproduced by the kinoform upon coherent irradiation, is established, recorded and converted by computer means into the associated phase distribution function which is required at the location of the kinoform characterised in that for the purposes of producing a kinoform of a code word comprising M discrete light/dark picture elements with 2 =< M =< 50, when establishing the amplitude distribution function of the image to be reproduced, each of the picture elements is replaced by a picture spot which in turn comprises N discrete picture elements which all have approximately the same intensity of radiation, wherein N is so selected that the product of M and N amounts to several hundreds.
A method of producing a kinoform wherein the amplitude distribution function of a plurality of discrete picture elements of an image which is to be reproduced by the kinoform upon coherent irradiation, is established, recorded and converted by computer means into the associated phase distribution function which is required at the location of the kinoform characterised in that for the purposes of producing a kinoform of a code word comprising M discrete light/dark picture elements with 2 ≤ M ≤ 50, when establishing the amplitude distribution function of the image to be reproduced, each of the picture elements is replaced by a picture spot which in turn comprises N discrete picture elements which all have approximately the same intensity of radiation, wherein N is so selected that the product of M and N amounts to several hundreds.
Claim 2
Independent Claim
137 words
A method of producing a kinoform wherein the amplitude distribution function of a plurality of discrete picture elements of an image which is to be reproduced by the kinoform upon coherent irradiation, is established, recorded and converted by computer means into the associated phase distribution function which is required at the location of the kinoform characterised in that for the purposes of producing a kinoform of a code word comprising M discrete light/dark picture elements with 2 ≤ M ≤ 50, when establishing the amplitude distribution function of the image to be reproduced, each of the picture elements is replaced by a picture spot which in turn comprises N discrete picture elements which all have approximately the same intensity of radiation, wherein N is so selected that the product of M and N amounts to several hundreds.
Claim 3
Dependent Claim
35 words
A method according to claim 1, characterised in that each of the picture elements is replaced by a picture spot comprising N discrete picture elements, with N being of the order of magnitude of 50.
Claim 4
Dependent Claim
32 words
A method according to claim 1 or claim 2, characterised in that the discrete light/dark picture elements of the code word are so formed that they have only two discrete light/dark values.
Claim 5
Dependent Claim
33 words
A method according to claim 1 or claim 2, characterised in that the discrete light/dark picture elements of the code word are so formed that they have more than two discrete level values.
Claim 6
Dependent Claim
20 words
Use of the method according to one of claims 1 to 4 for producing authenticity features on documents representing value.
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