Registers – Coded record sensors – Particular sensor structure
Patent
1995-08-30
2000-03-21
Hajec, Donald
Registers
Coded record sensors
Particular sensor structure
235470, G06K 710
Patent
active
060392541
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for illuminating flat bar codes, an image of the bar code being generated on a receiving sensor via receiver optics for the recognition and evaluation of the bar code. The illumination and the receiving sensor are matched to the usually longitudinally extended flat form of a bar code. The method is suitable for use in a bar code reader.
In semiconductor production, semiconductor structures (electronic components; chips) are constructed on silicon wafers, using different chemical and physical processes. During the entire chip production, the wafers must always be able to be assigned unequivocally to a production order. Only in this way can the next process step for the wafers be determined reliably and the process data arising can be stored. For the unequivocal identification of various wafers, a marking is applied to the latter. For marking, laser methods can be used in an advantageous way. Here, either a so-called clear text and/or a bar code marking is applied to a wafer. Because of the multiplicity of successive process steps, in which material coatings, etching sequences or the like are carried out on the wafer, the marking is affected detrimentally. The marking quality decreases on average with the number of production steps.
If the guiding of the process is to be supported by the use of automatic identification devices, even markings of poor quality must be able to be identified reliably.
The identification of wafers proves to be very difficult, because of the disturbing variables present and the treatment processes to be carried out, which affect the markings detrimentally. The identification is therefore often carried out by humans. In individual cases, intelligent image processing systems or scanners especially adapted to this problem are also used for bar code recognition. Disturbing variables occurring such as, for example, inaccurate wafer feeding, tilting of the wafer and streaks on the marking or contrasts which are too low within the bar code lead to a reduced operational reliability of the identification systems. The recognition of the marking with the human eye is cost-intensive and time-intensive. The use of image processing systems is likewise costly and not sufficiently reliable. The recognition times, as a rule, are over one second.
In German Patent Specification DE 27 04 983 C3, a device is described with which the whole field of view, for example the field of the marking area of a bar code, is imaged onto the effective area of a row of photodiodes used as receiving sensor. However, the device is used for the recognition of faults in the surface or in the dimensions of an object.
SUMMARY OF THE INVENTION
The invention is based on the object of achieving optimal contrasts within the image, produced on a receiving sensor, of a bar code applied to a reflecting surface, in order to detect unequivocally the position of marking elements within the bar code. This object is achieved by a method for imaging bar codes, the stationary bar code being illuminated by means of an illumination device and receiving optics imaging the area having the bar code completely in its longitudinal direction, here lying in the x-direction, and at least partially with reference to the height of the marking elements, which run in the y-direction, onto a one- or two-dimensionally spatially resolving receiver. Bundles of light from the illumination device are incident on the area having the bar code in such a way that the reflected bundles of light generate, via receiving optics, a maximum illumination intensity on the receiving sensor, and thus bright-field illumination with respect to the areas surrounding the marking elements. A line of light generated on the illumination device is oriented in such a way that bundles of light which proceed from the beginning to the end of the line of light, seen in the longitudinal direction, are incident on area elements from the beginning to the end of the area having the bar code under bright-field illumination
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"Technische Optik [Technical Optics]; Prof. Gottfried Schroder; Vogel Buchverlag Wurzburg; p. 152".
Froese-Peeck Rudiger
Gerhard Detlef
Lechner Johann
Hajec Donald
Siemens Aktiengesellschaft
Tremblay Mark
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