Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Reexamination Certificate
2000-05-26
2002-11-05
Evans, F. L. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
C356S239100, C356S124000
Reexamination Certificate
active
06476909
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method thereof for inspecting optical members, mostly optical members made of plastic, and more particularly relates to an apparatus and method for inspecting optical members using image processing technology.
2. Description of the Related Art
Recently, optical members made of plastic have been widely used in photographing lens systems or finders of cameras, due to their lightweight and low-cost qualities.
However, with such optical members there is a possibility that dust, e.g., in the form of carbonated plastic, remains in the mold after injection molding and thus might enter inside a lens being molded. Additionally, since plastic is softer than glass, there is a higher possibility of a flawed lens being produced, and therefore inspection for defects before assemble has an increased importance.
Defect inspection is undertaken in order to judge whether an optical member has sufficient performance to be used, namely whether it is non-defective and useable, or is defective and can not be used.
In the prior art, defect inspection is usually either in the form of visual inspection by the naked eye, in which a skilled worker illuminates the optical member, such as a lens or prism, by an intense light, or in the form of image processing of an inputted image obtained by picking-up an image of the optical member.
If dust has entered a lens, factors such as the size of the dust, the depth of entry, or the distance from the optical axis, need to be determined. On the other hand, if there is a flaw, factors such as the size of the flaw, the surface on which the flaw is, or the distance of the flaw from the optical axis, need to be determined.
The criteria used for judging whether an optical member is defective or non-defective, is different depending on whether dust has entered the member or whether there is a flaw, for example, even in the case that the dust and the flaw have the same size, one may be allowable, e.g., the dust, while the other type of defect, e.g., the flaw, is not. Therefore, an inspector should judge whether the lens is defective or non-defective, not only from the extent of the defect, but also from the identification of the type of defect, i.e., whether it is dust or a flaw.
In visual inspections by the naked eye, a judgement as to whether a lens is defective or non-defective is subjective according to each individual inspector, and thus judgement criteria may change according to the physical condition of the same inspector, e.g., in the weakening of the eyes, to say nothing of the judgement criteria of a different inspector, thus making it difficult to maintain unitary judgements.
SUMMARY OF THE INVENTION
The present invention is made considering the problems of the prior art as described above. An object of the present invention to provide an optical member inspection apparatus and method of inspection thereof capable of judging the defectiveness of an optical member according to objective criteria.
Another object of the present invention is to provide an optical member inspection apparatus capable of obtaining the most appropriate luminance in accordance with the shape of an object to be inspected.
Yet another object of the present invention is to provide an optical member inspection apparatus capable of obtaining the most appropriate luminance in accordance with the color of a defect.
Still another object of the present invention is to provide an optical member inspection apparatus capable of obtaining the most appropriate luminance for detecting defects according to the type of an object to be inspected.
Another object of the present invention is to provide an apparatus capable of being used for an optical member, as a subject for inspection, that has a function of a wedge prism which deflects light in one direction.
Another object of the present invention is to provide an optical member inspection apparatus and method of inspection thereof provided with a magnification adjustment function capable of setting magnification according to objective criteria.
Still another object of the present invention is to provide an optical member inspection apparatus, in regard to an inspection apparatus by using image processing, capable of promptly detecting a defect of an object to be inspected.
Another object of the present invention is to provide an optical member inspection apparatus capable of detecting a mold mark separated from other defects using image processing.
Yet another object of the present invention is to provide a method of mark separation capable of separating a mark accurately through simple processing, from an input image obtained by picking-up an image of an optical member, and also provides an optical member inspection apparatus using the same method.
Still another object of the present invention is to provide a method of efficient inspection in the case of a sequential inspection of optical members in regard to a plural number of items to be inspected, and also provide an optical member inspection apparatus using the method.
Another object of the present invention is to provide an optical member inspection apparatus and method of inspection thereof, for which it is not necessary to execute complicated image processing for the removal of noise etc., while the subject inspection range is wider than the designed effective aperture.
Yet another object of the present invention is to provide an optical member inspection apparatus capable of expediting the duration of inspection in the case of a sequential inspection of a plural number of objects to be inspected.
Still another object of the present invention is to provide a method of controlling of lighting luminance, according to a histogram of a picked-up image, and also provides an optical member inspection apparatus using the same method.
To achieve the objects mentioned above, according to an aspect of the present invention, an optical member inspection apparatus is provided having an inspection optical system having a light source, and a diffusing means for diffusing the light emitted from the light source. The diffusing means has a central portion and a peripheral portion. The diffusion transmittance of the peripheral portion is higher than the diffusion transmittance of the central portion. The inspection optical system also has an image pick-up means to pick-up an image of the optical member to be inspected, and is positioned so as to receive that light emitted from the light source and transmitted through the diffusing means and the optical member. A judging means is also provided, for judging whether or not the optical member has a defect, in accordance with image signals output from the image pick-up means.
Preferably, the diffusing means consists of a plane plate member, having central and peripheral portions, extending substantially perpendicular to an optical axis of the image pick-up means. However, first and second diffusing plates, together determining the central and peripheral portions, could also be used as the diffusing means. The shapes of the central and peripheral portions, are preferably determined according to the shape of the optical member to be inspected. In addition, it is also preferred that the central and peripheral portions are each variable in shape, and that the optical member inspection apparatus includes means for setting each shape.
The diffusing means preferably consists of a liquid crystal panel having a plurality of segments, each segment having a diffusion transmittance that can be varied according to a voltage applied thereto. The setting means sets the shape of the peripheral and central portions by controlling the voltage applied to each segment.
Preferably, a wavelength selecting means is provided for selecting a wavelength of that light incident on the optical member. The wavelength selecting means can vary the spectral transmittance of the central and peripheral portions.
In addition, a means for moving at least the diffusing means in a direction along the
Hara Masato
Kida Atsushi
Nakayama Toshihiro
Sugiura Masayuki
Asahi Kogaku Kogyo Kabushiki Kaisha
Evans F. L.
Pitney Hardin Kipp & Szuch LLP
Smith Zandra
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