INTERFEROMETER MEASURING SYSTEM USING A PLURALITY OF SYNCHRONOUS LIGHT SOURCE

PROBLEM TO BE SOLVED: To measure the displacements of one or more moving stages by using one or more light sources. SOLUTION: This is the device for synchronizing the measurements of two interferometers 40 and 41 using two light sources 20 and 22. The light sources 20 and 22 output single straight-line polarized light beams 21 and 23. Acoustooptic elements 30 and 31 convert the input beams 21 and 23 into two crossed polarized light beams separated by the frequency difference determined by a main oscillator 10 and a secondary oscillator 14. The oscillators 10 and 14 drive the acoustooptic elements 30 and 31 by different amplifiers 12 and 13 for synchronizing both light sources. Two crossed polarized-light-beam pairs 70 and 72 cross the interferometers 40 and 41. The beams from the interferometers are returned to optical receivers 50 and 51 and send beat frequencies 51 and 53 to electronic measuring devices 60 and 62. The electronic measuring devices 60 and 62 use a signal 150 from the main oscillator 10 and the beat frequencies 51 and 53, determine and store the phase difference and output phase differences 61 and 63.