Abstract: A size difference measuring method comprising: an optical interference measuring step without wringing, of obtaining, through simultaneous measurement of interference fringes, size information relating to the end standards which are set between interferometers, by an optical interferometer without wringing that comprises: one light emitter that emits coherent light; a beam splitter; the interferometers which are arranged with predetermined separation interval between them and each of which has an optical axis in agreement with the length-measurement axes of the end standards having known preliminary values; and a first interference fringe observation device and a second interference fringe observation device; and a computing step of computing a difference of a size of the end standards, based on the interference fringe phase differences acquired as the size information of the end standards.

Abstract: A size difference measuring method comprising: an optical interference measuring step without wringing, of obtaining, through simultaneous measurement of interference fringes, size information relating to the end standards which are set between interferometers, by an optical interferometer without wringing that comprises: one light emitter that emits coherent light; a beam splitter; the interferometers which are arranged with predetermined separation interval between them and each of which has an optical axis in agreement with the length-measurement axes of the end standards having known preliminary values; and a first interference fringe observation device and a second interference fringe observation device; and a computing step of computing a difference of a size of the end standards, based on the interference fringe phase differences acquired as the size information of the end standards.