| 简介 |
Light scattered by flaws on a wafer is extremely weak, and PMT and MPPC are detection methods for measuring the weak light at high speed and high sensitivity. The detection method has a function for photoelectrically converting the weak light and exponentially increasing the number of electrons; however, since the quantum efficiency of photoelectric conversion is low; i.e., 50% or less, a problem is presented in regard to losing the signal light and reducing the S/N ratio. The present invention addresses light amplification for directly amplifying light before photoelectric conversion. Light amplification is a method in which a signal light and light from an excitation light source are introduced into a rare-earth-doped fiber, and the signal light is amplified upon induced emission. The present invention is characterized in that this light amplification is used. The present invention is further characterized in that the amplification factor changes due to a variety of conditions. |
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