| 摘要 |
PURPOSE:To make constant light quantity of beam obtained through a hole, by perforating a plurality of various diameter holes in a rotating disc and installing an optical filter with optical transmission coefficient inversely proportional to the cross-sectional area of the hole for each of these holes. CONSTITUTION:A laser beam L1 is enlarged into a thick parallel flux with a beam expander 21 and by passing through either one of the holes 22b perforated in a rotating disc 22 and conversion is mode into a beam diameter corresponding to each inside diameter of the hole 22b. Here, a beam of light that passed through the hole 22b has light quantity proportional to each hole area and consequently, by passage of this beam through a shade filter 22C provided with optical transmission coefficient inversely proportional to the hole area, all the beams are adjusted to the constant light quantity. Consequently, the required measurement resolution capacity can easily be available and variation in the measurement sensitivity by varying resolution capacity can also be prevented.
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