Browse Prior Art Database

Decoding and Encoding for Product Identification

IP.com Disclosure Number: IPCOM000075321D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 77K

Publishing Venue

IBM

Related People

Jorgenson, RR: AUTHOR

Abstract

Shown is a decoding and identification technique for readily translating human readable alphanumeric characters directly into binary-coded decimal (8421-BCD) output for EDP control, data reduction, and/or display applications. The technique is applicable to nearly any type of product identification or reading application, with particular utility in integrated circuit applications with regard to wafer and mask serial number and/or part number identification.

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Decoding and Encoding for Product Identification

Shown is a decoding and identification technique for readily translating human readable alphanumeric characters directly into binary-coded decimal (8421-BCD) output for EDP control, data reduction, and/or display applications. The technique is applicable to nearly any type of product identification or reading application, with particular utility in integrated circuit applications with regard to wafer and mask serial number and/or part number identification.

The underlying theory of operation of this decoding and identification concept is based on the technique of bandpass detection of specific frequencies of a diffraction pattern representing the Fourier transformation of BCD coded grating segments contained within the equivalent human readable numeral or character which is etched into a suitable surface, such as that of a semiconductor wafer. In general, the numerals or numbers to be identified represent a composite of a human readable and a BCD machine readable font which utilizes a solid-state phototransistor array and logic for information processing. Fig. 1 illustrates a typical font geometry showing this relationship.

As indicated in Fig. 1, each numeral #1 through #9 is a composite of grating segments. There are four (4) distinct grating segments for each decimal position
(i.e., units, tens, hundreds, etc.), since a 8421 BCD conversion is discussed in this particular instance. Each grating segment is composed of an inclined parallel fine line structure each having their own unique line size, spacing, and inclination, yielding a particular spatial frequency content at the Fourier transformation plane of the decoding optical system such as that shown in Fig. 2.

Thus, for a particular decimal position, numerals 0 through 9 can be decoded to their B:CD equivalent, as illustrated in Table 1, for direct machine input (display and/or computer). As will be noted, the numeral "0" is solid, thus, representing the absence of a light spot or spatial frequency at the Fourier transformation plane of the decoding optical system. For example, for seven (7) decimal places, there would be 28 (7 x 4) unique grating segments. Table II illustrates typical grating segment geometry for numerals 0 through 9 for each of seven decimal positions.

Referring to Fig. 2, if a wafer located at the signal plane 01 is illuminated by a collimated monochromatic light source, S1, lens L2 forms a diffraction pattern representing the Fourier transformation of the input information at a distance f behind the lens (back focal plane). In this particular case, light reflecting from the grating segments is diffracted into various orders symmetrically across the optical axis. The Fourier transformation of the BCD diffraction grating is distributed in space in accordance with the following relationship: R(n) = n lambda f over w. where: n = order of the maxima (in this discussion we are interested in sensin...