| 摘要 |
PURPOSE:To measure the speed of a light pervious object with good accuracy in a non-contact state, by respectively arranging polarizing plates on the light path reaching the light pervious object from a light source and on the light path reaching a space filter from the light pervious object. CONSTITUTION:The first polarizing plate 8 is arranged on the light path reaching a light pervious object from an illumination light source 2 and the second polarizing plate 9 is arranged on the light path reaching a speed detector 6 from the light pervious object 1. By this constitution, when the light pervious object 1 has optical anisotropy, the directions of the polarizing axes of the aforementioned polarizing plates 8, 9 are adjusted to illuminate the light pervious object 1 by white light from the illumination light source 2. Whereupon, a colored pattern corresponding to the double refractivity distribution or thickness distribution of the object 1 appears on the object 1 by the double refraction phenomenon of the object 1. Since this pattern is observed so as to move at a speed V in the direction shown by an arrow A with the movement of the object 1, the quantity of the light received by a light detector 5 through a space filter 4 changes corresponding to the running speed of the colored pattern and the speed of the light pervious object 1 can be stably measured.
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