Optics: measuring and testing – Sample – specimen – or standard holder or support
Patent
1992-06-15
1994-10-04
Rosenberger, Richard A.
Optics: measuring and testing
Sample, specimen, or standard holder or support
356 36, 356243, 250304, G01N 2101
Patent
active
053531124
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the optical inspection of samples of particulate material and in particular, the the preparation and presentation of such samples for optical inspection.
BACKGROUND OF THE INVENTION
Optical inspection can be used to determine properties of particulate material, for example colour and reflectivity. One particular application of optical quality measurement is in monitoring the cosmetic quality of synthetic diamond crystals that are to be used as abrasive material. In one known measurement system, a sample is placed in a pot, that is to say an open container, and the exposed surface of the material is inspected by a suitable optical measurement device. Usually, the sample surface is uneven, and its height relative to the measurement device is inconstant, depending on the size of the particles. In the case of saw diamond abrasive, even though each sample is taken from a specific size range, there is still a variation of size and shape of particles within the sample. The resulting uneven sample surface and variations in surface height relative to the measurement device materially reduce the accuracy and repeatability of the measurement results, and measurement on one sample may not be readily comparable with measurements on other samples.
SUMMARY OF THE INVENTION
An object of the present invention is to improve the repeatability and accuracy of optical inspection measurements on particulate material, and in particular to provide for improved presentation of samples for optical inspection.
According to one aspect of the invention there is provided a method of preparing a sample of particulate material comprising placing the said material in an open container, providing a reference surface at a predetermined position, moving the container thereby bringing an exposed surface of the particulate material therein into intimate contact with the reference surface, holding the container in the position thus defined, and removing the reference surface, thereby presenting said sample with an exposed surface which is substantially even and located at a predetermined position defined by said reference surface.
According to another aspect of the invention there is provided apparatus for the optical inspection of particulate material, comprising a support, an open sample container mounted for movement in height relative to the support, a reference member having an undersurface placed at a predetermined height relative to the support and such that the sample of particulate material previously placed in the container can be raised into contact of the said undersurface, and means for holding the container in the position defined by such contact, the reference member being movable away from the container at said position to permit subsequent optical inspection of the exposed surface of the sample at the said position.
According to yet another aspect of the invention there is provided an optical inspection apparatus for particulate material, comprising a body, a container movably supported in the body for containing a sample of said material, a reference member having a reference and compaction surface on its underside and locatable above the container with the said surface at a predetermined position, and means for moving the container containing a said sample towards the said member when the latter is so located, thereby urging a said sample against the said surface, and means for holding the container in the thus-defined position when the said member is removed, so as to leave a compacted and even sample surface exposed for optical inspection.
The reference member or reference surface is preferably used not only to define the position of the sample surface but also to compact the sample and level the sample surface. Accordingly the sample will normally be urged against the reference member under a certain amount of pressure.
In a preferred arrangement, respective carriers for optical inspection devices and for the reference member are interchangeably mountable on the body
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Gersan Establishment
Pham Hoa Q.
Rosenberger Richard A.
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