Optics: measuring and testing – Surface roughness
Reexamination Certificate
1999-02-22
2004-04-27
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Surface roughness
C356S237200
Reexamination Certificate
active
06727993
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface inspection apparatus and a surface inspection method, particularly to a surface inspection apparatus and a surface inspection method for measuring surface conditions of automobile parts, OA apparatus, household electric appliances or the like.
2. Discussion of the Background
In fields of trim parts of automobile, OA, domestic electrification or the like, the level of requirement for physical properties of the surfaces of products concerning their external appearances, in concrete terms, injuries, unevenness in height, unevenness in gloss, unevenness in color, and so forth, has become severer year by year. In particular, in products made of synthetic resins, in addition to the above-described various properties, the external appearance of a weld line, the external appearance of flow marks, stress whitening, and so forth, are greatly concerned in their commodity values.
The surface condition of such a product is hitherto appraised by performing a sensuous test, in which a classification is made on eye observation. In the sensuous test, however, the result of the test is obtained only in a rank on each appraisal item, and minute information on the surface condition, that is, information at the same level as a state of seeing with the naked eye can not be preserved, so it is a hindrance to quality control and material development.
In order to solve such a problem, it has been done to keep the surface condition of a product with a photograph or the like, but it is not considered objective data because its contrast varies according to photographing conditions, printing conditions, and so forth, so a method and an apparatus in which the surface condition of a product or a material can be accurately evaluated or measured have been desired earnestly.
On the other hand, as a method for measuring the surface condition of a synthetic resin material, the present applicant proposed a method for measuring the degree of whitening by an injury in the surface of the material (Japanese Patent Publication No. 52160/1995). This method is a method in which an injury of a predetermined shape is inflicted on a sample made of a synthetic resin, the injured whitening portion is irradiated with a light in dark-field illumination, and the light quantity of the component parallel with the optical axis of the objective lens in diffusedly reflected rays of the light is measured to measure the injury whitening degree. By changing the magnification of the objective lens according to the size of the injury, the light detection extent, that is, the extent in the surface of the sample subject to the measurement of the reflected light is controlled.
This method is useful for a material test in material development or the like, but has a problem that it can not be applied to surface inspection of products in quality control. That is, in this method, because an injury of a predetermined shape must be inflicted on a sample for measurement, the surface condition of the product can not be evaluated as it is, and further, because only the portion of the injury of the predetermined shape is measured due to the low detection accuracy, the surface condition of the whole of the object to be measured including the portion other than the injury can not be measured.
Besides, because an objective lens of a high magnification is used to decrease the detection extent when the whitening degree of a minute injury is measured, in case of a sample having a complicated shape, or the like, if the injury varies in position, a measurement error arises due to a divergence of the focus so a highly accurate measurement can not be realized. If an objective lens of a low magnification is used in order to decrease such a divergence of the focus, the peripheral portion of the injury is included in the detection extent, and so there is a problem that the reflected light from the injury can not be detected with a good accuracy.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a surface inspection apparatus and a surface inspection method in which the surface condition can be measured with a good accuracy independently of the shape of an object to be measured, and which can be applied also to surface inspection of products.
A surface inspection apparatus of the present invention is characterized by comprising a light source for applying a light to a surface of an object to be measured, an objective lens opposite to the surface of the object to be measured and for receiving a reflected light applied from the light source and reflected on the surface of the object to be measured, light detection means for detecting a component incident on the corresponding objective lens from a parallel direction with its optical axis in the reflected light passing through this objective lens and obtaining its light quantity, and a slit provided in the optical path between the objective lens and light detection means.
In the present invention, the light applied from the light source is reflected on the surface of the object to be measured, and the reflected light passes through the objective lens. When the reflected light is incident on the objective lens, the reflected light incident in parallel with the optical axis of the objective lens is incident on the slit after passing through the objective lens, and only the light having passed through the opening of this slit is introduced to the light detection means to obtain its light quantity.
In this manner, because the slit is provided in the light path between the objective lens and the light detection means, since only the component having passed through the opening of the slit in the reflected light reflected in the parallel direction with the optical axis of the objective lens can be taken out and detected, the detection extent of the reflected light in the surface of the object to be measured, namely, the light detection extent can be restricted by the opening of the slit. Accordingly, because the reflected light within the extent limited by narrowing the light detection extent with the objective lens and the slit can be taken out and its light quantity can be obtained, the surface condition of the aimed external appearance can be measured exactly and with a high accuracy.
Further, when the surface condition of the object to be measured of a complicated shape is measured, in case of using the objective lens of a low magnification for preventing a divergence of the focus, because the detection extent in the surface of the object to be measured can be restricted by the slit, since the surface of the object to be measured can be finely divided into a plurality of light detection extents and detected, the surface condition of the object to be measured can be measured with a good accuracy.
Because a superior detection accuracy can be obtained in this manner, not only the conventional degree of whitening of an injury but also a difference in the surface condition due to color, unevenness in height, or the like can be measured, and because the whole of the surface of the object to be measured including an uninjured portion can be measured, in addition to that an evaluation result corresponding to the external appearance of the object to be measured can be obtained, since it is avoided to inflict a predetermined injury on the surface of the object to be measured for measurement as a conventional manner, it can be applied to not only a surface inspection of a material but also a surface inspection in quality inspection of products.
Besides, when the object to be measured is evaluated with scanning, it is desirable to narrow the measurement area, that is, the light detection extent. At this time, because there is a fear of movement of focus with scanning, it is preferable for suppressing the movement of focus to narrow the light detection extent by using the objective lens of a magnification as low as possible and decreasing the opening of the slit.
Besides, because the objective lens of a lower m
Idemitsu Petrochemical Co. Ltd.
Rosenberger Richard A.
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