| 摘要 |
<p>A slit for selectively allowing the transmission of emitted light from a light-emitting portion that has been diffracted through passing through a pipe wherein there is no fluid is provided on the slit side of the pipe, between a slit of the light-emitting portion and a slit of a detecting portion. The emitted light from the light-emitting portion, which is diffracted by passing through the pipe wherein there is a fluid, is blocked by the plate member wherein the slit is formed, so as to not arrive at the detecting portion.</p> |
