Abstract: A spectrometer and a metrology system capable of improving spectral performance are provided. The spectrometer includes a collimator lens, a focusing lens, and a spatial light modulator (SLM), wherein light reflected by the SLM is output from an output slit through the focusing lens and a dispersive optical element, and on a second plane perpendicular to a first plane including optical paths of pieces of light dispersed at different angles, an incident slit, the output slit, and a reflective plane have a conjugate relationship.

Abstract: Tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylenediphosphonite, stabilizers for organic materials, which contain said compound, and stabilized organic materials containing said compound as a stabilizer. The tetrakis(2,4-di-tert-butyl-5-methylphenyl)-4,4'-biphenylenediphosphonite has particularly superior hydrolysis resistance, and is characterized in that it has superior storage stability due to its scarce hygroscopicity. It can be purified and handled easily since it is in a powder form, and it shows less volatility at high temperatures. By using the compound of the present invention as a stabilizer for organic materials, extremely useful organic materials imparted with superior processing stability, heat resistance and resistance to oxidative degradation can be provided.