應用於距離基線場絕對校正之干涉比長儀介紹

On the Väisälä Comparator for the Absolute Calibration of Baseline

「長度」是基本物理量測量之一，也是國家測量製圖所需要之基本要件。距離測量儀器需要經由校正，以確認其所量測之值的不確定度，而「基線場」是目前測量儀器如電子測距儀校正之標準設施。校正之追溯，常見者為使用標準件進行比對之「相對校正」，而以「絕對校正」方式確認「基線場」標準值則較為少見。「V?is?l? Comparator」（干涉比長儀）之性質為「白光干涉儀」，精度可達10^（-7），亦即0.1ppm。由於其高精度與高解析度，在芬蘭基線場於1933年建立時，便以為建立「基線場」標準值之「絕對校正」工具。本文謹概略介紹此一「干涉比長儀」之設計概念、基本特性，並引用近期文獻，說明其儀器形貌。

＂Length＂ is an important fundamental physical property, as well as a basic measurement for surveying and mapping. The instrument used for range measurement should be calibrated to confirm its uncertainty. Baseline calibration is the current well-established calibration procedure for range instruments such as EDM. Traceability is a fundamental principle of calibration. This is frequently performed in the form of ＂relative calibration＂ with ＂standard parts＂, whereas ＂absolute calibration＂ is rarely applied. However, the ＂Väisälä Comparator＂ is an instrument capable of performing ＂absolute calibration＂ of a baseline. The design is based on interferometry of white light and can reach levels of 10^(-7), that is 0.1ppm. Due to its high accuracy and high resolution, the ＂Väisälä Comparator＂ has been utilized as the means of absolute calibration since the establishment of a Finnish standard baseline in 1933. This note briefly introduces the fundamental principles of the ＂Väisälä Comparator＂. Referencing recent literature, the instrument and its operation are also described.