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AssigneeNederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO
InventorAntonius Ludovicus Gerardus Van Valkenburg
Estimating the term…
Method for inspecting an article for defects, light scattered by the article is collected. A defect in the article gives rise to a pulse scanning response signal, which is fed to a processing unit. The light beam has a wavelength such that the article is transparent thereto. At least two scanning response signals are obtained, which are associated with focal points at different focal depths in the article. The location of the defect in the direction of the light beam is determined from the steepness of the front and rear flanks of the pulse scanning response signals. By this means it is possible to determine whether a defect is on or in the article. The at least two scanning response signals can be obtained by scanning the article at least twice, with different focal depth for each scan.
Method for inspecting an article (1) for defects (2), wherein the article (1) is scanned by means of a scanning light beam (3, 4, 5), the light scattered by the article (1) is collected and the collected light is converted into an electrical scanning response signal (6, 7, 8) which is fed to a processing unit (18) for processing the scanning response signals (6, 7, 8), a defect (2) in the article (1) giving rise to a pulse in the scanning response signal (6, 7, 8), characterised in that the light beam (3, 4, 5) has a wavelength such that the article (1) is transparent thereto, in that at least two scanning response signals (6, 7, 8) are obtained, each of which being associated with a focal point located in the direction of the light beam at a different depth in the article (1), and in that the location of the defect (2) in the direction of the light beam is determined from the steepness of the front and rear flanks of the pulses in the scanning response signals (6, 7, 8).
Installation for inspecting an article (1) for defects (2), comprising an article holder (10) for holding an article (1) to be inspected in an inspection plane, a light source (9), which emits a scanning light beam (3, 4, 5) for scanning the article (1) to be inspected, a collection device (11, 19, 25) for collecting the light scattered by the article (1), a converter (13), for converting the collected light into an electrical scanning response signal (6, 7, 8) and a defect (2) in the article (1) giving rise to a pulse in the scanning response signal, and a processing unit (18) connected to the output of the converter (13) for processing the scanning response signal (6, 7, 8), characterised in that the scanning light beam (3, 4, 5) has a wavelength such that the article (1) is transparent to said beam, that means are present for obtaining at least two scanning response signals (6, 7, 8), each of which being associated with a focal point located in the direction of the scanning light beam at a different depth in the article (1), and in that the processing unit (18) is provided with a flank steepness measuring device for measuring the steepness of the front and rear flanks of the pulses in the scanning response signals (6, 7, 8) fed thereto, and an evaluation device for determining the location of a defect from the measured flank steepnesses.
Dependencies are inferred from the claim text.