Exemplary embodiments are described below with reference to schematic figures which do not restrict the invention.
With the size of the central diaphragm 9, which can to a certain extent be of a variable design, a certain independency of the sensor compared with angular deviations is produced, so that the surface to be examined can to a certain extent be inclined toward the vertical illumination direction. The central diaphragm of the optical detector system effects an annular detector aperture irrespective of the site of the scanning beam. This annular aperture enables a uniform detection sensitivity for linear defects, irrespective of their direction on the surface to be examined.
A complete examination of flat glass is thus possible, and defects, which are punctiform, laminar or linear, can be recognized and localized in the submicrometer range. In particular, the complete inspection of the surface with a rough localization of the defects is carried out using a first sensor with high depth of field and the decision as to on which side of a flat glass panel the defect lies is made using a second sensor with lower depth of field.
With a corresponding infeed of a flat glass panel, a laminar scanning of the object and thus the detection of different types of defects is achieved using the oscillating movement of the laser beam.
Fine scratches scatter the illuminating light only perpendicularly to its longitudinal axis. They are thus only visible if they are viewed perpendicularly to their longitudinal axis. To ensure that scratches of this type can be identified irrespective of their position on the glass, the aperture of the optical receiver system must be arranged rotationally-symmetrical to the illumination direction. If the aperture is not completely rotationally symmetrical for technical reasons, several sensors with overlapping aperture ranges can be used. In this way, an object surface is scanned in succession. The high measurement speed is achieved by the parallel use of several sensors. Furthermore, this illustrated modular design enables the inspection system to be adapted to glass plates of different widths.
As the depth of field of the above-described sensor is greater than the glass thickness, defects on the front and rear sides can at first not be distinguished from one another. To this end, a second sensor is provided, the depth of field of which is smaller than the glass thickness and can thus emit distance and/or height values. In practice, a complete examination is not possible using only a second sensor of this type. This is thus only used if the lateral position of a defect, which is already found using the first sensor, is fixed and thus only the height position is still to be determined.
Number | Date | Country | Kind |
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102006019468.3 DE | Apr 2006 | DE | national |