| 摘要 |
PURPOSE:To shorten inspection time while enabling accurate evaluation, by irradiating the entire surface of a circuit board with a large calibre beam of laser light to examine a diffraction light intensity distribution of the entire surface of the circuit board thus observing a diffraction light pattern thereof. CONSTITUTION:The entire surface of a circuit board 1 is irradiated with a large calibre beam of laser light 20 with a uniform intensity generated with a beam expander comprising a plurality of lenses and a diffraction light from a diffraction grating is taken with a TV camera 23 to observe. Here, the angle of incidence of the laser light is predetermined, and also the intensity I0 of an emission laser light is predetermined. Then, diffraction light intensity distribution of the circuit board is inspected from the of a picture take with the camera 23. A higher intensity of the diffraction light can be evaluated and selected from a light color part of the picture. On the other hand, when the density of the picture is uniform, the light intensity distribution does not look so clear to discriminate. The intensity of a center specified line L of a TV scan line is extracted at the bottom of the picture. The intensity thus obtained is evaluated in comparison with a reference value Is, thereby allowing a subsequent epitaxial growth on an acceptable circuit board alone.
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