To accurately measure the contact angle of the fillet formed on a matrix by a liquid substance, using an optical technique.
An illumination means 36 is equipped with a plurality of light- emitting parts 42 and the fillet 40 is illuminated by the first pattern, second pattern and third pattern which illuminate the fillet 40 in a diffused state and, different in emission intensity of the light-emitting parts 42. Angles of the respective parts of the fillet 40 are calculated, on the basis of the ratio of the intensity of reflected light at illumination of the fillet 40 by the first pattern and the intensity of reflected light at the time of illumination of the fillet 40 by the second pattern, by a computer 16. A reflected light image at the illumination of the fillet by either one of the patterns or a composited light image obtained by compositing a plurality of reflected light images is confirmed by a monitor and angle data calculated by mistake will not be used in operation or corrected to be used in operation, to perform integration from a proper start point to operate the three-dimensional shape of the fillet. Since a contact angle θ is calculated from this three-dimensional shape, the contact angle θ can be accurately calculated.
YAMASHITA MASAHIKO
TAKAO HISAFUMI
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