| 摘要 |
<p>PURPOSE:To allow measurement of roll gap with no influence of light reflected on the surface of a work roll by disposing a member for screening luminous flux selectively in the path of luminous flux projected from a light source body. CONSTITUTION:Upon receiving a horizontal luminous flux from a light source body 10 through a horizontal lens, an irradiation filter 21 disposed between a parallel lens 11 and upper/lower work rolls 2A, 2B passes only a P polarized light selectively, for example, thus irradiating the surface of the rolls 2A, 2B with P polarized light. Upon receiving the P polarized light leaked through the gap between the rolls 2A, 2B and the light reflected on the rolls 2A, 2B, a light receiving filter 22 disposed between the rolls 2A, 2B and a focus lens 13 passes only the P polarized light selectively. This constitution prevents the luminous flux projected from the light source body 1 toward the rolls 2A, 2B and reflected on the surface thereof to be polarized from being superposed as a measurement error of roll gap even if it is received by a detector 14.</p> |
