Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Reexamination Certificate
1999-03-30
2001-02-06
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
C356S239200
Reexamination Certificate
active
06184977
ABSTRACT:
CROSS-REFERENCED APPLICATIONS
This application is based on Application No. HEI 10-83464 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and device for inspecting for surface defects, internal defects, and surface-adhered foreign matter on semitransparent materials. Specifically, the present invention relates to a method and device for inspecting for surface defects, internal defects, and surface-adhered foreign matter on semitransparent hard disk substrates, liquid crystal display panels, lenses and the like.
2. Description of the Related Art
In general, inspection methods and inspection devices for detecting surface defects (scratches, pits), internal defects (air bubbles, contaminants), surface-adhered foreign matter (adhered small particles) (hereinafter referred to collectively as “defects”) and the like in hard disk substrates, liquid crystal display panels, lenses and the like formed of semitransparent material can be separated into: inspection methods and inspection devices of the reflection type, which inspect for defects from information included in light reflected by the surface of the object being inspected (hereinafter referred to as “inspection object”); and inspection methods and inspection devices of the transmission type, which inspect for defects from information included in light transmitted through the inspection object.
In inspection methods and inspection devices of the reflection type, disadvantages arise in that the inadequate contrast between the scattered light from a defect area and the reflected light from the non-defect area due to low light reflectivity of the transparent or semitransparent inspection object prevents satisfactory defect inspection from being attained. Furthermore, the reflected light from the inspection object includes not only reflected light from the surface of the inspection object on the light source side (surface reflected light), but also includes reflected light from the surface of the inspection object on the side opposite the light source (back surface reflected light), which presents the disadvantage of eliminating the effects of this back surface reflected light from the inspection results.
In inspection methods and inspection devices of the transmission-type, on the other hand, while they do not have the disadvantages typical of the inspection methods and devices of the reflection type, they are subject to dispersion of the scattered light in all directions because they use a construction which condenses (collects) the light from a light source at the inspection position of the inspection object, i.e., they use a construction which causes light to enter the inspection position from various angles. This type of construction is disadvantageous in that there is insufficient contrast between the scattered light from a defect area and the transmitted light from the non-defect area, such that defect inspection cannot be readily accomplished.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel inspection method and inspection device capable of easily detecting defects in an inspection object formed of transparent or semitransparent material.
The present invention utilizes substantially parallel light rays to illuminate an inspection object in a detection method for detecting defects of an inspection object from illumination light transmitted through a detection object formed of transparent or semitransparent material. This substantially parallel light includes not only completely parallel light but also light which can be regarded as completely parallel.
Other modes of the inspection method of the present invention observe the inspection object from a direction substantially parallel to the direction of advancement of the substantially parallel light.
The inspection device of the present invention embodies the inspection method of the invention, and utilizes substantially parallel light rays to illuminate an inspection object in a detection method for detecting defects of an inspection object from illumination light output from a light source and transmitted through a detection object formed of transparent or semitransparent material.
Another mode of the inspection device of the present invention sets the light source and inspection object to a relationship such that the light output from a light source becomes substantially parallel at the position of the inspection object in a detection device for detecting defects of an inspection object from illumination light emitted from a light source and transmitted through a detection object formed of transparent or semitransparent material.
Another mode of the inspection device of the present invention provides a detection unit for detecting defects of an inspection object such that the inspection object is observed from a direction substantially parallel to the direction of advancement of the substantially parallel light.
Another mode of the inspection device of the present invention provides a detection unit for detecting defects of an inspection object, said detection unit being disposed at a position such that the light transmitted through the inspection object does not directly enter.
Yet another mode of the inspection device of the present invention provides a light shield member between a light source and an inspection object or between an inspection object and the detection unit such that light transmitted through an inspection object to the detection unit for detecting defects of the inspection object does not directly enter.
Still another mode of the inspection device of the present invention moves light shield member relative to the inspection object.
These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate specific embodiments of the invention.
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patent: 4989973 (1991-02-01), Noso et al.
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patent: 05119468 (1993-05-01), None
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patent: 08201313 (1996-08-01), None
McDermott & Will & Emery
Minolta Co. , Ltd.
Rosenberger Richard A.
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