目前為止使用萊維特定律在量測距離的研究是以造父變星光變曲線的平均星等來討論，因此我們想要去討論多相位萊維特定律和平均星等萊維特定律的差別，探討多相位萊維特定律在量測距離上的展望。我們用OGLE III的大麥哲倫星雲(LMC)的經典造父變星的觀測資料去討論這個主題，我們分為兩個方向去討論，一是萊維特定律的分散度，二是量測距離。在分散度的討論上，的確存在一個相位的分散度會小於平均星等的分散度，但兩者的差距不大，對於降低誤差的貢獻可以忽略。另外，我們同樣以LMC不同觀測資料來做量測距離的自我檢測，兩種方法算出的距離皆落於我們預設的大麥哲倫星雲的距離誤差範圍內，多相位萊維特定律算出的距離比平均星等算出的距離近；要確定兩種方法差異性，仍需應用至其它星系的距離量測才能確定。 We use the Optical Gravitational Lensing Experiment III (OGLE III) classical Cepheid data to derive multi-phase period-luminosity relation ( PL relation), and compare with mean PL relation in the application of distance estimator. First, we discuss the difference in PL relation's dispersion. It exists that there's a phase with smaller dispersion value than mean's, but thier difference is small. In addition, there is a bump existed in a specific phase, it might be due to Cepheid pulsational inner shock. We also performed self-testing in estimating distance using different observational data in LMC's Cepheids. The distance derived from multi-phase PL relations is closer than the distance derived from mean PL relation, and they are reasonable because they are within errors. We suggest to test other galaxy's distance to discuss their differences in more detail.
